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Stroke Prophylaxis: Hypertension Management and Antithrombotic Therapy
Abstract
To review trials involving risk factor management and pharmacologic therapy for the prevention of stroke.
English-language literature published between 1966 and 1992 was analyzed; pertinent literature is reviewed.
Studies that evaluated the impact of risk factor management on prevention of vascular events were selected. In addition, trials assessing the safety and efficacy of pharmacologic intervention in primary and secondary stroke prevention were evaluated.
Trials were evaluated for their ability to demonstrate a decrease in stroke occurrence.
Various trials were analyzed in several categories. Studies evaluating risk factor management of hypertension and cardiogenic cerebral emboli were reviewed and recommendations made based on a consensus of these trials. The use of antiplatelet agents in stroke prevention was addressed by a review of pertinent trials and meta-analyses.
The control of risk factors and the use of antiplatelet agents significantly reduces the risk of vascular events. Benefit from different therapies may be specific to certain patient populations and recommendations are made for these patients.
In the present pilot study an attempt was made to evaluate the usefulness of results obtained about the treatment of patients suffering from high blood pressure for a pharmacoepidemiological study of the therapeutic value of antihypertensive agents. Data from 90 hypertensive patients were used in the present retrospective-prospective study. These patients all attended an out-patient clinic located in one of the East-Bohemian districts that are participating in the MONICA programme. Instead of the analysis of the population data, regular blood pressure measurements, plasma glucose levels, and total cholesterol concentrations were measured and analysed. The consumption of various antihypertensive drugs in this study was similar to that found in larger studies performed in other health districts of the Czech Republic. Diuretics were the drugs most frequently prescribed for hypertensive patients. General practitioners rarely prescribed calcium channel blockers and angiotensin-converting enzyme inhibitors in 1990 and 1991. The metabolic effects of antihypertensive drugs, mostly diuretics, were not significantly evident. The most frequent occurrence of non-compensated blood pressure was recorded for the treatments with Trimecryton and methyldopa. However, the validity of these findings should be tested in a larger group of hypertensic patients.
Stroke prevention is a crucial issue because (i) stroke is a frequent and severe disorder, and (ii) acute stroke therapies that are effective at the individual level have only a little impact in term of public health. Stroke prevention consists of the combination of 3 strategies: an optimal management of vascular risk factors, associated when appropriate with antithrombotic therapies, carotid surgery, or both. Primary prevention trials have shown that reducing blood pressure in hypertensive subjects reduces their vascular risk, including stroke. The association of perindopril plus indapamide reduces the vascular risk in patients who have had a stroke or TIA during the last 5 years, irrespective of their baseline blood pressure. Lowering serum cholesterol with statins or gemfibrozil in patients with hypercholesterolemia or coronary heart disease (CHD), reduces the risk of stroke. However, no trial of cholesterol-lowering therapy has been completed in stroke patients. A strict control of high cholesterol levels should be encouraged, because of benefits in terms of CHD. Statins should be prescribed for stroke patients with CHD, or increased cholesterol levels. Cigarette smoking is associated with an increased risk of stroke and should be avoided. Careful control of all risk factors, especially arterial hypertension in type 1 and type 2 diabetics is recommended, together with a strict glycemic control to reduce systemic microvascular complications. Estrogens prescribed in hormone replacement or oral contraceptive therapies are not recommended after an ischemic stroke. It is also recommended to reduce alcohol consumption and obesity, and to increase physical activity in patients at risk for first-ever or recurrent stroke. An optimal management of risk factors for stroke is crucial to reduce the risks of first-ever stroke, recurrent stroke, any vascular event after stroke and vascular death. One of the major public health issues for the coming years will be to focus more on risk factor recognition and management.
The ISH Statement on blood pressure lowering and stroke prevention was finalized after presentation and discussion at the World Health Organization and International Society of Hypertension (WHO-ISH) Meeting on Stroke and Blood Pressure, held in Melbourne Australia, 5-7 December 2002. The meeting was conducted under the auspice of the Austin Hospital Medical Research Foundation, Melbourne.
To assess the clinical benefits of treating hypertension in elderly patients and to derive practical guidelines regarding indications, goals, and forms of treatment.
Review of six published randomised trials.
Active treatment of hypertension in elderly patients was associated with significant improvements in several indices of cardiovascular morbidity and mortality, particularly the incidence of fatal and non-fatal strokes. On the basis of the trial data, combined systolic and diastolic hypertension was defined as a sustained systolic pressure greater than 160 mmHg and diastolic pressure greater than 90 mmHg. There is convincing evidence that efforts should be made to reduce both systolic and diastolic pressures to below these levels in patients up to the age of 80 years. Isolated systolic hypertension was defined as a systolic pressure greater than 160 mmHg in the presence of a diastolic pressure less than 90 mmHg. Two trials reported benefit from the treatment of isolated systolic hypertension in patients up to the age of 80, and further trials are underway to support or refute this recommendation. Diuretics have an established role in the management of hypertension in elderly patients; beta adrenoceptor antagonists have given variable results, and the benefits are less impressive than with diuretic based regimens. Newer agents show promise in the treatment of elderly patients, particularly in the presence of coexisting disease, but their effects on morbidity and mortality have not been evaluated in large randomised trials.
Diuretics rather than beta blockers are the treatment of choice for patients with uncomplicated hypertension, but combinations of drugs may be required in as many as 50% of patients.
Nonrheumatic atrial fibrillation is common among the elderly and is associated with an increased risk of stroke. We investigated whether anticoagulation with warfarin would reduce this risk.
We conducted a randomized, double-blind, placebo-controlled study to evaluate low-intensity anticoagulation with warfarin (prothrombin-time ratio, 1.2 to 1.5) in 571 men with chronic nonrheumatic atrial fibrillation; 525 patients had not previously had a cerebral infarction, whereas 46 patients had previously had such an event. The primary end point was cerebral infarction; secondary end points were cerebral hemorrhage and death.
Among the patients with no history of stroke, cerebral infarction occurred in 19 of the 265 patients in the placebo group during an average follow-up of 1.7 years (4.3 percent per year) and in 4 of the 260 patients in the warfarin group during an average follow-up of 1.8 years (0.9 percent per year). The reduction in risk with warfarin therapy was 0.79 (95 percent confidence interval, 0.52 to 0.90; P = 0.001). The annual event rate among the 228 patients over 70 years of age was 4.8 percent in the placebo group and 0.9 percent in the warfarin group (risk reduction, 0.79; P = 0.02). The only cerebral hemorrhage occurred in a 73-year-old patient in the warfarin group. Other major hemorrhages, all gastrointestinal, occurred in 10 patients: 4 in the placebo group, for a rate of 0.9 percent per year, and 6 in the warfarin group, for a rate of 1.3 percent per year. There were 37 deaths that were not preceded by a cerebral end point--22 in the placebo group and 15 in the warfarin group (risk reduction, 0.31; P = 0.19). Cerebral infarction was more common among patients with a history of cerebral infarction (9.3 percent per year in the placebo group and 6.1 percent per year in the warfarin group) than among those without such a history.
Low-intensity anticoagulation with warfarin prevented cerebral infarction in patients with nonrheumatic atrial fibrillation without producing an excess risk of major hemorrhage. This benefit extended to patients over 70 years of age.
There is evidence that aspirin in low doses favorably influences the course of pregnancy-induced hypertension, but the mechanism, although assumed to involve suppression of the production of thromboxane by platelets, has not been established. We performed a randomized study of the effect of the long-term daily administration of 60 mg of aspirin (n = 17) or placebo (n = 16) on platelet thromboxane A2 and vascular prostacyclin in women at risk for pregnancy-induced hypertension. Low doses of aspirin were associated with a longer pregnancy and increased weight of newborns. Serum levels of thromboxane B2, a stable product of thromboxane A2, were almost completely (greater than 90 percent) inhibited by low doses of aspirin. The urinary excretion of immunoreactive thromboxane B2 was significantly reduced without changes in the level of 6-keto-prostaglandin F1 alpha, a product of prostacyclin. Mass spectrometric analysis showed that aspirin reduced the excretion of the 2,3-dinor-thromboxane B2 metabolite--mainly of platelet origin--by 81 percent and of thromboxane B2, probably chiefly of renal origin, by 59 percent. The urinary excretion of 6-keto-prostaglandin F1 alpha and of its metabolite 2,3-dinor-6-keto-prostaglandin F1 alpha was not affected. Low doses of aspirin only partially (63 percent) reduced neonatal serum thromboxane B2. No hemorrhagic complications were observed in the newborns. Thus, in women at risk for pregnancy-induced hypertension, low doses of aspirin selectively suppressed maternal platelet thromboxane B2 while sparing vascular prostacyclin, but only partially suppressed neonatal platelet thromboxane B2, allowing hemostatic competence in the fetus and newborn.
A six year randomised trial was conducted among 5139 apparently healthy male doctors to see whether 500 mg aspirin daily would reduce the incidence of and mortality from stroke, myocardial infarction, or other vascular conditions. Though total mortality was 10% lower in the treated than control group, this difference was not statistically significant and chiefly involved diseases other than stroke or myocardial infarction. Likewise, there was no significant difference in the incidence of non-fatal myocardial infarction or stroke--indeed, disabling strokes were somewhat commoner among those allocated aspirin. The lower confidence limit for the effect of aspirin on non-fatal stroke or myocardial infarction, however, was a substantial 25% reduction. Migraine and certain types of musculoskeletal pain were reported significantly less often in the treated than control group, but as the control group was not given a placebo the relevance of these findings was difficult to assess. There was no apparent reduction in the incidence of cataract in the treated group. The lack of any apparent reduction in disabling stroke or vascular death contrasts with the established value of antiplatelet treatment after occlusive vascular disease.
Objective: To identify those patients with nonrheumatic atrial fibrillation who are at high risk and those at low risk for arterial thromboembolism. Design: Cohort study of patients assigned to placebo in a randomized clinical trial. Setting: Five hundred sixty-eight inpatients and outpatients with nonrheumatic atrial fibrillation assigned to placebo therapy at 15 U.S. medical centers from 1987 to 1989 in the Stroke Prevention in Atrial Fibrillation study. Patients were followed for a mean of 1.3 years. Measurements: Clinical variables were assessed at study entry and correlated with subsequent ischemic stroke and systemic embolism by multivariate analysis. Main Results: Recent (within 3 months) congestive heart failure, a history of hypertension, and previous arterial thromboembolism were each significantly and independently associated with a substantial risk for thromboembolism (> 7% per year; P ≤ 0.05). The presence of these three independent clinical predictors (recent congestive heart failure, history of hypertension, previous thromboembolism) defined patients with rates of thromboembolism of 2.5% per year (no risk factors), 7.2% per year (one risk factor), and 17.6% per year (two or three risk factors). Nondiabetic patients without these risk factors, comprising 38% of the cohort, had a low risk for thromboembolism (1.4% per year; 95% CI, 0.05% to 3.7%). Patients without clinical risk factors who were under 60 years of age had no thromboembolic events. Conclusion: Patients with atrial fibrillation at high risk (> 7% per year) and low risk (< 3% per year) for thromboembolism can be identified by readily available clinical variables.
Objective:
To identify echocardiographic predictors of arterial thromboembolism in patients with nonrheumatic atrial fibrillation and to determine whether these add to clinical variables for risk stratification.
Design:
Cohort study of patients assigned to placebo in a randomized clinical trial.
Setting:
Five hundred sixty-eight inpatients and outpatients with nonrheumatic atrial fibrillation assigned to placebo therapy at 15 U.S. medical centers from 1987 to 1989 in the Stroke Prevention in Atrial Fibrillation study. Patients were followed for a mean of 1.3 years.
Measurements:
M-mode and two-dimensional (2-D) echocardiograms performed at study entry and interpreted by local cardiologists. The predictive value of 14 echocardiographic variables for later ischemic stroke or systemic embolism was assessed by multivariate analysis.
Main results:
Left ventricular dysfunction from 2-D echocardiograms (P = 0.003) and the size of the left atrium from M-mode echocardiograms (P = 0.02) were the strongest independent predictors of later thromboembolism. Multivariate analysis of these two independent echocardiographic predictors with the three independent clinical predictors of thromboembolism (history of hypertension, recent congestive heart failure, previous thromboembolism) identified 26% of the cohort with a low risk for thromboembolism (1.0% per year; 95% Cl, 0.2% to 4.0%). Compared with risk stratification using clinical variables alone, echocardiographic results altered thromboembolic risk stratification in 18% of the entire cohort and in 38% of those without clinical risk factors.
Conclusions:
Both left ventricular and left atrial variables are significant predictors of thromboembolism in patients with nonvalvular atrial fibrillation. Our results challenge traditional views of the pathogenesis of ischemic stroke in patients with atrial fibrillation and suggest that standard echocardiography contributes to risk stratification, differentiating the one third of patients without clinical risk factors who are at increased risk for stroke from the remainder who may not need antithrombotic prophylaxis.
Background.
Aspirin is known to improve the outcome of patients who have had a cerebral transient ischemic attack, but the optimal dose of aspirin remains uncertain. Experimental evidence indicates that 30 mg of aspirin daily alters platelet aggregation more favorably than the 300-mg dose currently used in patients after transient ischemic attack or minor ischemic stroke.
Methods.
We assessed the effects of two doses of a water-soluble preparation of acetylsalicylic acid, or aspirin (30 mg vs. 283 mg a day), on the occurrence of death from all vascular causes, nonfatal stroke, or nonfatal myocardial infarction in a double-blind, randomized, controlled clinical trial in patients who had had a transient ischemic attack or minor stroke. A total of 3131 patients participated in the study. The mean follow-up was 2.6 years.
Results.
In the group assigned to receive 30 mg of aspirin, the frequency of death from vascular causes, nonfatal stroke, or nonfatal myocardial infarction was 228 of 1555 (14.7 percent), as compared with 240 of 1576 (15.2 percent) in the group assigned to receive 283 mg. The age- and sex-adjusted hazard ratio for the group receiving the lower dose was 0.91 (95 percent confidence interval, 0.76 to 1.09). There were slightly fewer major bleeding complications in the 30-mg group than in the 283-mg group (40 vs. 53), and significantly fewer reports of minor bleeding (49 vs. 84). Fewer patients receiving 30 mg of aspirin reported gastrointestinal symptoms (164 vs. 179) and other adverse effects (73 vs. 90).
Conclusions.
Our data indicate that 30 mg of aspirin daily is no less effective in the prevention of vascular events than a 283-mg dose in patients with a transient ischemic attack or minor stroke, and has fewer adverse effects. (N Engl J Med 1991;325:1261–6.)
Background.
Nonrheumatic atrial fibrillation increases the risk of stroke, presumably from atrial thromboemboli. There is uncertainty about the efficacy and risks of long-term warfarin therapy to prevent stroke.
Methods.
We conducted an unblinded, randomized, controlled trial of long-term, low-dose warfarin therapy (target prothrombin-time ratio, 1.2 to 1.5) in patients with nonrheumatic atrial fibrillation. The control group was not given warfarin but could choose to take aspirin.
Results.
A total of 420 patients entered the trial (212 in the warfarin group and 208 in the control group) and were followed for an average of 2.2 years. Prothrombin times in the warfarin group were in the target range 83 percent of the time. Only 10 percent of the patients assigned to receive warfarin discontinued the drug permanently. There were 2 strokes in the warfarin group (incidence, 0.41 percent per year) as compared with 13 strokes in the control group (incidence, 2.98 percent per year), for a reduction of 86 percent in the risk of stroke (warfarin:control incidence ratio = 0.14; 95 percent confidence interval, 0.04 to 0.49; P = 0.0022). There were 37 deaths altogether. The death rate was markedly lower in the warfarin group than in the control group: 2.25 percent as compared with 5.97 percent per year, for an incidence ratio of 0.38 (95 percent confidence interval, 0.17 to 0.82; P = 0.005). There was one fatal hemorrhage in each group. The frequency of bleeding events that led to hospitalization or transfusion was essentially the same in both groups. The warfarin group had a higher rate of minor hemorrhage than the control group (38 vs. 21 patients).
Conclusions.
Long-term low-dose warfarin therapy is highly effective in preventing stroke in patients with nonrheumatic atrial fibrillation, and can be quite safe with careful monitoring. (N Engl J Med 1990; 323:1505–11.)
Objective - To establish whether treatment with diuretic or β blocker in hypertensive older adults reduces risk of stroke, coronary heart disease, and death. Design - Randomised, placebo controlled, single blind trial. Setting - 226 general practices in the MRC general practice research framework. Subjects - 4,396 patients aged 65-74 randomised to receive diuretic, β blocker, or placebo. Patients had mean systolic pressures of 160-209 mm Hg and mean diastolic pressures <115 mm Hg during an eight week run in and were not taking antihypertensive treatment. Intervention - Patients were randomised to atenolol 50 mg daily; hydrochlorothiazide 25 mg or 50 mg plus amiloride 2.5 mg or 5 mg daily; or placebo. The regimens were adjusted to achieve specified target pressures. Mean follow up was 5.8 years. Main outcome measures - Strokes, coronary events, and deaths from all causes. Results - Both treatments reduced blood pressure below the level in the placebo group. Compared with the placebo group, actively treated subjects (diuretic and β blocker groups combined) had a 25% (95% confidence interval 3% to 42%) reduction in stroke (p = 0.04), 19% (-2% to 36%) reduction in coronary events (p = 0.08), and 17% (2% to 29%) reduction in all cardiovascular events (p = 0.03). After adjusting for baseline characteristics the diuretic group had significantly reduced risks of stroke (31% (3% to 51%) p = 0.04), coronary events (44% (21% to 60%), p = 0.0009), and all cardiovascular events (35% (17% to 49%), p = 0.0005) compared with the placebo group. The β blocker group showed no significant reductions in these end points. The reduction in strokes was mainly in non-smokers taking the diuretic. Conclusion - Hydrochlorothiazide and amiloride reduce the risk of stroke, coronary events, and all cardiovascular events in older hypertensive adults.
Background:
Atrial fibrillation in the absence of rheumatic valvular disease is associated with a fivefold to sevenfold increased risk of ischemic stroke.
Methods and main results:
The Stroke Prevention in Atrial Fibrillation Study, a multicenter, randomized trial, compared 325 mg/day aspirin (double-blind) or warfarin with placebo for prevention of ischemic stroke and systemic embolism (primary events), and included 1,330 inpatients and outpatients with constant or intermittent atrial fibrillation. During a mean follow-up of 1.3 years, the rate of primary events in patients assigned to placebo was 6.3% per year and was reduced by 42% in those assigned to aspirin (3.6% per year; p = 0.02; 95% confidence interval, 9-63%). In the subgroup of warfarin-eligible patients (most less than 76 years old), warfarin dose-adjusted to prolong prothrombin time to 1.3-fold to 1.8-fold that of control reduced the risk of primary events by 67% (warfarin versus placebo, 2.3% versus 7.4% per year; p = 0.01; 95% confidence interval, 27-85%). Primary events or death were reduced 58% (p = 0.01) by warfarin and 32% (p = 0.02) by aspirin. The risk of significant bleeding was 1.5%, 1.4%, and 1.6% per year in patients assigned to warfarin, aspirin, and placebo, respectively.
Conclusions:
Aspirin and warfarin are both effective in reducing ischemic stroke and systemic embolism in patients with atrial fibrillation. Because warfarin-eligible patients composed a subset of all aspirin-eligible patients, the magnitude of reduction in events by warfarin versus aspirin cannot be compared. Too few events occurred in warfarin-eligible patients to directly assess the relative benefit of aspirin compared with warfarin, and the trial is continuing to address this issue. Patients with nonrheumatic atrial fibrillation who can safely take either aspirin or warfarin should receive prophylactic antithrombotic therapy to reduce the risk of stroke.
The Physicians' Health Study is a randomized, double-blind, placebo-controlled trial designed to determine whether low-dose aspirin (325 mg every other day) decreases cardiovascular mortality and whether beta carotene reduces the incidence of cancer. The aspirin component was terminated earlier than scheduled, and the preliminary findings were published. We now present detailed analyses of the cardiovascular component for 22,071 participants, at an average follow-up time of 60.2 months. There was a 44 percent reduction in the risk of myocardial infarction (relative risk, 0.56; 95 percent confidence interval, 0.45 to 0.70; P < 0.00001) in the aspirin group (254.8 per 100,000 per year as compared with 439.7 in the placebo group). A slightly increased risk of stroke among those taking aspirin was not statistically significant; this trend was observed primarily in the subgroup with hemorrhagic stroke (relative risk, 2.14; 95 percent confidence interval, 0.96 to 4.77; P = 0.06). No reduction in mortality from all cardiovascular causes was associated with aspirin (relative risk, 0.96; 95 percent confidence interval, 0.60 to 1.54). Further analyses showed that the reduction in the risk of myocardial infarction was apparent only among those who were 50 years of age and older. The benefit was present at all levels of cholesterol, but appeared greatest at low levels. The relative risk of ulcer in the aspirin group was 1.22 (169 in the aspirin group as compared with 138 in the placebo group; 95 percent confidence interval, 0.98 to 1.53; P = 0.08), and the relative risk of requiring a blood transfusion was 1.71. This trial of aspirin for the primary prevention of cardiovascular disease demonstrates a conclusive reduction in the risk of myocardial infarction, but the evidence concerning stroke and total cardiovascular deaths remains inconclusive because of the inadequate numbers of physicians with these end points.
Neurogenic mechanisms are important in the maintenance of most forms of hypertension, yet the brain is highly vulnerable to the deleterious effects of elevated blood pressure. Hypertensive encephalopathy results from a sudden, sustained rise in blood pressure sufficient to exceed the upper limit of cerebral blood flow autoregulation. The cerebral circulation adapts to chronic less severe hypertension but at the expense of changes that predispose to stroke due to arterial occlusion or rupture. Stroke is a generic term for a clinical syndrome that includes focal infarction or hemorrhage in the brain, or subarachnoid hemorrhage. Atherothromboembolism and thrombotic occlusion of lipohyalinotic small-diameter end arteries are the principal causes of cerebral infarction. Microaneurysm rupture is the usual cause of hypertension-associated intracerebral hemorrhage. Rupture of aneurysms on the circle of Willis is the most common cause of nontraumatic subarachnoid hemorrhage. Stroke is a major cause of morbidity and mortality, particularly among persons aged 65 years or older. Treatment of diastolic hypertension reduces the incidence of stroke by about 40%. Treatment of isolated systolic hypertension in persons aged 60 years and older reduces the incidence of stroke by more than one third. Blood pressure management in the setting of acute stroke and the role of antihypertensive therapy in the prevention of multi-infarct dementia require further study.
(Arch Intern Med. 1992;152:938-945)
We studied whether changes in recognition and control of hypertension could be detected in the population of Rochester, Minn, from 1950 to 1979, a period in which a major decrease in the incidence rate of stroke was observed. Prevalence of diastolic blood pressure greater than or equal to 105 mm Hg fell 26% and 70% in men and women, respectively, between 1950 to 1959 and 1970 to 1979. Prevalence of pressures greater than or equal to 95 mm Hg decreased 5% in men and 58% in women. Increasing control of hypertension had an almost inverse linear relationship with the decreasing incidence of stroke in women, but the incidence of stroke in men did not decrease until ten years after improvement in the control of blood pressure began. We conclude that improvements in the detection and control of hypertension contributed to the declining incidence of stroke and that differences in management of hypertension could account for the difference between men and women in the trend of stroke decline.
(JAMA 1987;258:214-217)
Isolated systolic hypertension (ISH), defined as systolic blood pressure of 160 mm Hg or greater when the diastolic pressure is less than 95 mm Hg, is a common form of hypertension among the elderly. We collected incidence and prevalence data on ISH and evaluated several potential factors for its occurrence in the Framingham Heart Study during 16 biennial examinations. The factors evaluated were age, sex, all components of the blood pressure (systolic and diastolic blood pressure, pulse pressure, and mean arterial pressure), Metropolitan relative weight, serum cholesterol level, serum uric acid level, cigarette smoking, ventricular heart rate, glucose intolerance, and hematocrit. The population at risk (1687 men and 1992 women) were those members of the Framingham cohort with a systolic blood pressure less than 160 mm Hg in the first four biennial examinations. Results showed ISH in 14.4% of the men and 22.8% of the women. Cumulative incidence rates were 418 per 1000 in men and 533 per 1000 in women. Significant risk factors for ISH were age, sex, all components of the blood pressure, and increased relative weight in women. We conclude that ISH is a highly prevalent disorder. Its major determinants are age, sex, increasing levels of blood pressure, and obesity in women.(JAMA 1988;260:3451-3455)
• Chronic atrial fibrillation without valvular disease has been associated with increased stroke incidence. The impact of atrial fibrillation on the risk of stroke with increasing age was examined in 5184 men and women in the Framingham Heart Study. After 30 years of follow-up, chronic atrial fibrillation appeared in 303 persons. Age-specific incidence rates steadily increased from 0.2 per 1000 for ages 30 to 39 years to 39.0 per 1000 for ages 80 to 89 years. The proportion of strokes associated with this arrhythmia was 14.7%, 68 of the total 462 initial strokes, increasing steadily with age from 6.7% for ages 50 to 59 years to 36.2% for ages 80 to 89 years. In contrast to the impact of cardiac failure, coronary heart disease, and hypertension, which declined with age, atrial fibrillation was a significant contributor to stroke at all ages.(Arch Intern Med 1987;147:1561-1564)
The Canadian Atrial Fibrillation Anticoagulation Study was a randomized double-blind placebo-controlled trial to assess the potential of warfarin to reduce systemic thromboembolism and its inherent risk of hemorrhage. As a result of the publication of two other “positive” studies of similar design and objective, this study was stopped early before completion of its planned recruitment of 630 patients. There were 187 patients randomized to warfarin and 191 to placebo. Permanent discontinuation of study medication occurred in 26% of warfarin-treated and 23% of placebo-treated patients. The target range of the international normalized ratio was 2 to 3. For the warfarin-treated patients, the international normalized ratio was in the target range 43.7% of the study days, above it 16.6% of the study days and below it 39.6% of the study days. Fatal or major bleeding occurred at annual rates of 2.5% in warfarin-treated and 0.5% in placebo-treated patients. Minor bleeding occurred in 16% of patiente receiving warfarin and 9% receiving placebo. The primary outcome event cluster was nonlacunar stroke, noncentral nervous systemic embolism and fatal or intracranial hemorrhage. Events were included in the primary analysis of efficacy if they occurred within 28 days of permanent discontinuation of the study medication. The annual rates of the primary outcome event cluster were 3.5% in warfarin-treated and 5.2% in placebo-treated patients, with a relative risk reduction of 37% (95% confidence limits, −63.5%, 75.5%, p = 0.17). This esumate of benefit of anticoagulant therapy in atrial fibrillation is consistent with the estimates from previous reports and supports the use of warfarin in patients with nonrheumatic valvular atrial fibrillation for the prevention of systemic thromboembolism.
The decision to initiate long-term anticoagulant therapy in a patient with valvular heart disease is frequently difficult because of the many variables that influence the risks of thromboembolism and of bleeding in a given individual. The patient's age, the specific valve lesion, the heart rhythm, the duration of the valve disease, a history of thromboembolism, patient attitude and life-style, associated diseases, and medications all must be considered. Because the state of such variables may change with time, a proper decision at one time in a patient's life may be inappropriate at another time. In some instances, the literature on a given subject is sparse or contains conflicting data that further confound the issue. Since the database for these guidelines is constantly being modified, particularly as a consequence of new randomized clinical trials, the clinician would do well to review his decision at frequent intervals.
Although the benefits of antihypertensive treatment in "young" elderly (under 70 years) hypertensive patients are well established, the value of treatment in older patients (70-84 years) is less clear. The Swedish Trial in Old Patients with Hypertension (STOP-Hypertension) was a prospective, randomised, double-blind, intervention study set up to compare the effects of active antihypertensive therapy (three beta-blockers and one diuretic) and placebo on the frequency of fatal and non-fatal stroke and myocardial infarction and other cardiovascular death in hypertensive Swedish men and women aged 70-84 years. We recruited 1627 patients at 116 health centres throughout Sweden, who were willing to participate, and who met the entry criteria of three separate recordings during a 1-month placebo run-in period of systolic blood pressure between 180 and 230 mm Hg with a diastolic pressure of at least 90 mm Hg, or a diastolic pressure between 105 and 120 mm Hg irrespective of the systolic pressure. The total duration of the study was 65 months and the average time in the study was 25 months. 812 patients were randomly allocated active treatment and 815 placebo. The mean difference in supine blood pressure between the active treatment and placebo groups at the last follow-up before an endpoint, death, or study termination was 19.5/8.1 mm Hg. Compared with placebo, active treatment significantly reduced the number of primary endpoints (94 vs 58; p = 0.0031) and stroke morbidity and mortality (53 vs 29; p = 0.0081). Although we did not set out to study an effect on total mortality, we also noted a significantly reduced number of deaths in the active treatment group (63 vs 36; p = 0.0079). The benefits of treatment were discernible up to age 84 years. We conclude that antihypertensive treatment in hypertensive men and women aged 70-84 confers highly significant and clinically relevant reductions in cardiovascular morbidity and mortality as well as in total mortality.
WHEN doctors prescribe antihypertensive drugs they face a dilemma. They are well aware that the benefits of lowering blood pressure in patients with hypertension far outweigh the risks, yet they have been warned that at some level of lowered blood pressure the tables turn and the risks become dominant. The initial downward slope of the mortality rate and the subsequent upward slope when the blood pressure gets too low form the so-called J curve. Our argument, presented here, is not that the J curve does not exist, but rather that the putative cause- and-effect relation between the reduction in blood . . .
We critically appraised the medical literature to evaluate whether there is a point beyond which blood pressure reduction in hypertensive subjects is no longer beneficial and possibly even deleterious. Thirteen studies that stratified cardiovascular outcomes by level of achieved blood pressure in treated hypertensive subjects who had been followed up for at least 1 year were critiqued by four independent reviewers. Data addressing population, protocol, and methodological characteristics were evaluated. Studies did not show a consistent J-shaped relationship between treated blood pressure and stroke, but they did demonstrate a consistent J-shaped relationship for cardiac events and diastolic blood pressure. The beneficial therapeutic threshold point was 85 mm Hg. We conclude that low treated diastolic blood pressure levels, ie, below 85 mm Hg, are associated with increased risk of cardiac events.
The recent publication of a new meta-analysis of 14 randomized trials of antihypertensive drug therapy in the Lancet has heightened the debate regarding the benefits of treatment of hypertension.1,2 There is little disagreement that pharmacologic therapy results in a decrease in strokes and in stroke deaths, reduction in the occurrence of congestive heart failure, reversal of left ventricular hypertrophy in more patients receiving treatment than on placebo or control, and a reduction in the rate of progression of renal disease in adequately treated hypertensive subjects.³⁻⁷ This article stems from the finding in the new meta-analysis that hypertension treatment results in a significant reduction in coronary heart disease (CHD). Although previous individual trials and overviews have suggested reductions of a similar magnitude, these findings have been dismissed as unimportant because statistical significance was not achieved.² This most recent and comprehensive meta-analysis included over 37 000 patients treated for
There are 14 unconfounded randomised trials of antihypertensive drugs (chiefly diuretics or beta-blockers): total 37,000 individuals, mean treatment duration 5 years, mean diastolic blood pressure (DBP) difference 5-6 mm Hg. In prospective observational studies, a long-term difference of 5-6 mm Hg in usual DBP is associated with about 35-40% less stroke and 20-25% less coronary heart disease (CHD). For those dying in the trials, the DBP difference had persisted only 2-3 years, yet an overview showed that vascular mortality was significantly reduced (2p less than 0.0002); non-vascular mortality appeared unchanged. Stroke was reduced by 42% SD 6 (95% confidence interval 35-50%; 289 vs 484 events, 2p less than 0.0001), suggesting that virtually all the epidemiologically expected stroke reduction appears rapidly. CHD was reduced by 14% SD 5 (95% CI 4-22%; 671 vs 771 events, 2p less than 0.01), suggesting that just over half the epidemiologically expected CHD reduction appears rapidly. Although this significant CHD reduction could well be worthwhile, its size remains indefinite for most circumstances (though beta-blockers after myocardial infarction are of substantial benefit). At present, therefore, a sufficiently high risk of stroke (perhaps because of age, blood pressure, or, in particular, history of cerebrovascular disease) may be the clearest indication for antihypertensive treatment.
The associations of diastolic blood pressure (DBP) with stroke and with coronary heart disease (CHD) were investigated in nine major prospective observational studies: total 420,000 individuals, 843 strokes, and 4856 CHD events, 6-25 (mean 10) years of follow-up. The combined results demonstrate positive, continuous, and apparently independent associations, with no significant heterogeneity of effect among different studies. Within the range of DBP studied (about 70-110 mm Hg), there was no evidence of any "threshold" below which lower levels of DBP were not associated with lower risks of stroke and of CHD. Previous analyses have described the uncorrected associations of DBP measured just at "baseline" with subsequent disease rates. But, because of the diluting effects of random fluctuations in DBP, these substantially underestimate the true associations of the usual DBP (ie, an individual's long-term average DBP) with disease. After correction for this "regression dilution" bias, prolonged differences in usual DBP of 5, 7.5, and 10 mm Hg were respectively associated with at least 34%, 46%, and 56% less stroke and at least 21%, 29%, and 37% less CHD. These associations are about 60% greater than in previous uncorrected analyses. (This regression dilution bias is quite general, so analogous corrections to the relations of cholesterol to CHD or of various other risk factors to CHD or to other diseases would likewise increase their estimated strengths.) The DBP results suggest that for the large majority of individuals, whether conventionally "hypertensive" or "normotensive", a lower blood pressure should eventually confer a lower risk of vascular disease.
We describe a patient with inherited plasminogen deficiency who developed extensive cerebral venous thrombosis. Several other conditions that might have contributed to a hypercoagulable state, including mild thrombocytosis, thyrotoxicosis, and a chronic inflammatory lung disorder, were present. We also discuss the evidence linking plasminogen deficiency with a thrombophilic state. The diagnosis of cerebral venous thrombosis in this case was readily established by nuclear magnetic resonance imaging, a technique that is ideally suited for the evaluation and follow-up of patients with this condition.
The aim of the study was to examine prospectively the association between regular aspirin use and the risk of a first myocardial infarction and other cardiovascular events in women.
Prospective cohort study including 6 years of follow-up.
Registered nurses residing in 11 US states.
US registered nurses (n = 87,678) aged 34 to 65 years and free of diagnosed coronary heart disease, stroke, and cancer at baseline. Followup was 96.7% of total potential person-years of follow-up.
Incidence of myocardial infarction, stroke, cardiovascular death, and all important vascular events.
During 475,265 person-years of follow-up, we documented 240 nonfatal myocardial infarctions, 146 nonfatal strokes, and 130 deaths due to cardiovascular disease (total, 516 important vascular events). Among women who reported taking one through six aspirin per week, the age-adjusted relative risk (RR) of a first myocardial infarction was 0.68 (95% confidence interval [CI], 0.52 to 0.89; P = .005), as compared with those women who took no aspirin. After simultaneous adjustment for risk factors for coronary disease, the RR was 0.75 (95% CI, 0.58 to 0.99; P = .04). For women aged 50 years and older, the age-adjusted RR was 0.61 (95% CI, 0.45 to 0.84; P = .002) and the multivariate RR was 0.68 (95% CI, 0.50 to 0.93; P = .02). We observed no alteration in the risk of stroke (multivariate RR = 0.99; P = .94). The multivariate RR of cardiovascular death was 0.89 (P = .56) and of important vascular events was 0.85 (P = .12). When examined separately, the results were nearly identical for the subgroups who took one through three and four through six aspirin per week. Among women who took seven or more aspirin per week, there were no apparent reductions in risk.
The use of one through six aspirin per week appears to be associated with a reduced risk of a first myocardial infarction among women. A randomized trial in women is necessary, however, to provide conclusive data on the role of aspirin in the primary prevention of cardiovascular disease in women.
We compared the efficacy and complications of anticoagulation with warfarin in 258 patients with prosthetic heart valves treated with regimens of "moderate intensity" (prothrombin-time ratio, 1.5; international normalized ratio, 2.65) or "high intensity" (prothrombin-time ratio, 2.5; international normalized ratio, 9) in a prospective, randomized study. The two patient groups were followed up for 421 patient-years and 436 patient-years, respectively. Eleven patients were lost to follow-up. Thromboembolism occurred with similar frequency in the two groups (4.0 and 3.7 episodes per 100 patient-years, respectively), but there was a total of 6.2 bleeding episodes per 100 patient-years in the moderate-intensity group, as compared with 12.1 episodes in the high-intensity group (P less than 0.002). There were 5.2 episodes of minor bleeding per 100 patient-years in the moderate-intensity group, as compared with 10.1 episodes in the high-intensity group (P less than 0.01). Major bleeding was also more common in the high-intensity group (2.1 episodes per 100 patient-years--including the only two fatal hemorrhages--as compared with 0.95 episode in the moderate-intensity group), but the difference was not statistically significant. We conclude that a moderate anticoagulant effect (prothrombin-time ratio, about 1.5) in patients with a mechanical prosthetic heart valve offers protection equivalent to that of more intensive therapy, but at a significantly lower risk.
Many patients suffer a stroke early after a transient ischemic attack, but the reason why is often unclear. We studied 12 patients with less than 75% stenosis of the internal carotid artery and a single hemispheric transient ischemic attack lasting less than 1 hour who had a normal neurologic examination 3-13 hours later and a normal computed tomogram 24-36 hours later. Single-photon emission computed tomography using technetium-99m HM-PAO less than or equal to 50 hours after the attack showed no abnormality in eight patients, but in the other four there was an area with 30-50% reduction in perfusion ipsilateral to the transient ischemic attack. Three of these four patients developed an ipsilateral infarct 3-7 days later, but none of the eight patients with normal single-photon emission computed tomograms had a stroke during the following weeks. No difference in therapy, risk factors, severity of internal carotid artery disease, or timing of the technetium-99m study could explain these findings. We suggest that some transient ischemic attacks, though clinically identical to others, may be associated with persisting focal hypoperfusion, which predisposes to early stroke.
The steady decline in mortality from stroke in the United States accelerated markedly in the 1970s. It has been widely assumed that an increase in the rate of treatment of hypertension is the most likely explanation for this major public health achievement. An analysis of available information, however, suggests that improvements in the community control of hypertension in the United States in the period 1970-1980 have contributed in only a minor way. There were 45,357 fewer deaths from stroke in 1980 among those aged 35-74 years than might have been expected if the death rates had stayed the same as in 1970. Data from the National Health and Nutrition Surveys indicate that six million more people received antihypertensive medication in 1980 than in 1970. Results from a pooled analysis of randomized controlled trials of the treatment of hypertension suggest that between 6% and 16% of the reduction in stroke mortality was due to the increased treatment of hypertension. Epidemiological observations indicate that between 16% and 25% of the overall decline in stroke mortality can be attributed to the treatment of hypertension, suggesting that clinical trials probably underestimate the community-wide benefits of treatment. These results also suggest that at least three quarters of the decline in stroke mortality in the United States in the period 1970-1980 is due to factors other than antihypertensive treatment.
We compared combination therapy with low-dose aspirin plus ticlopidine to therapy with aspirin alone or ticlopidine alone in patients suffering transient ischemic attack or cerebral infarction. In 17, 24, and 23 patients, respectively, 300 mg/day aspirin, 200 mg/day ticlopidine, and 81 mg/day aspirin plus 100 mg/day ticlopidine were administered orally. Aspirin alone markedly inhibited platelet aggregation induced by arachidonic acid, partially inhibited platelet aggregation induced by adenosine diphosphate, and did not inhibit platelet aggregation induced by platelet activating factor. Ticlopidine alone inhibited platelet aggregation induced by adenosine diphosphate and platelet activating factor, but did not inhibit platelet aggregation induced by arachidonic acid. Combination therapy with aspirin plus ticlopidine markedly inhibited platelet aggregation induced by all three agonists. Plasma concentrations of beta-thromboglobulin and platelet factor 4 remained unchanged by aspirin alone, were slightly reduced by ticlopidine alone, and were markedly reduced by aspirin plus ticlopidine. Plasma concentration of thromboxane B2 was reduced by aspirin alone or with ticlopidine, but not by ticlopidine alone. The level of 6-ketoprostaglandin F1 alpha was reduced only by aspirin alone. Bleeding time was significantly prolonged by aspirin alone and by ticlopidine alone, although the greatest prolongation was produced by aspirin plus ticlopidine. Our results indicate that the combination of aspirin plus ticlopidine is a potent antiplatelet strategy, although the clinical importance of the changes observed need to be determined by a properly designed and controlled prospective study.
Data from 30 years of follow-up of the original Framingham Study cohort of 5,070 men and women aged 30-62 years who were first examined during the period 1948-1952 and who were free of cardiovascular disease reveal that blood pressure is a strong and consistent predictor of the development of coronary heart disease, stroke, transient ischemic attack, and congestive heart failure. Other factors related to blood pressure like obesity, left ventricular hypertrophy as demonstrated on electrocardiograms, and heart enlargement as shown by x-ray radiography made several selective additional independent contributions to risk; heart enlargement by x-ray radiography was the best predictor of congestive heart failure.
From November, 1985, to June, 1988, 1007 outpatients with chronic non-rheumatic atrial fibrillation (AF) entered a randomised trial; 335 received anticoagulation with warfarin openly, and in a double-blind study 336 received aspirin 75 mg once daily and 336 placebo. Each patient was followed up for 2 years or until termination of the trial. The primary endpoint was a thromboembolic complication (stroke, transient cerebral ischaemic attack, or embolic complications to the viscera and extremities). The secondary endpoint was death. The incidence of thromboembolic complications and vascular mortality were significantly lower in the warfarin group than in the aspirin and placebo groups, which did not differ significantly. 5 patients on warfarin had thromboembolic complications compared with 20 patients on aspirin and 21 on placebo. 21 patients on warfarin were withdrawn because of non-fatal bleeding complications compared with 2 on aspirin and none on placebo. Thus, anticoagulation therapy with warfarin can be recommended to prevent thromboembolic complications in patients with chronic non-rheumatic AF.
We performed a double-blind randomized trial comparing high doses of subcutaneous heparin (12,500 units every 12 hours) with low doses (5000 units every 12 hours) for 10 days in the prevention of left ventricular mural thrombosis in 221 patients with acute anterior myocardial infarction. Left ventricular mural thrombosis was observed by two-dimensional echocardiography on the 10th day after infarction in 10 of 95 patients (11 percent) in the high-dose group and in 28 of 88 patients (32 percent) in the low-dose group (P = 0.0004). One patient in the high-dose group and four in the low-dose group had nonhemorrhagic strokes (P = 0.17). One patient in the low-dose group had a fatal pulmonary embolism. There was no difference in the frequency of hemorrhagic complications, which occurred in six patients in the high-dose group and four in the low-dose group. The mean (+/- SEM) plasma heparin concentration was 0.18 +/- 0.017 U per milliliter in the high-dose group and 0.01 +/- 0.005 U per milliliter in the low-dose group (P less than 0.0001). In the high-dose group, the mean plasma heparin concentration was 0.10 +/- 0.029 U per milliliter among patients with abnormal two-dimensional echocardiograms, as compared with 0.19 +/- 0.019 U per milliliter among patients with normal echocardiograms (P = 0.01). We conclude that heparin administered subcutaneously in a dosage of 12,500 units every 12 hours to patients with acute anterior transmural myocardial infarction is more effective than a lower dosage (5000 units every 12 hours) in preventing left ventricular mural thrombosis.
The antithrombotic approach to patients with acute myocardial infarction in the prevention of venous, left ventricular and coronary artery thromboembolic events should be based on an understanding of pathogenesis and risk. Coronary thrombotic events involve conditions of high shear rate present in areas of vessel stenosis or disrupted atherosclerotic plaque, which lead to activation of both platelets and the coagulation system, and are best prevented by platelet inhibitors alone or in combination with an anticoagulant. However, thromboembolism that originates in the venous system or cardiac chambers is related to situations of blood stasis and low shear rate, which predominantly result in clotting activation and fibrin-thrombus formation and are best approached with anticoagulant therapy. For prevention of venous thrombosis and pulmonary embolism, early mobilization is essential and should be supplemented by low-dose heparin in patients at high risk, including the elderly and those with large infarcts, heart failure or previous thromboembolic events. For prevention of left ventricular mural thrombosis and systemic embolism, high-dose heparinization is indicated in patients with large infarcts, particularly in the anterior location and in those with heart failure. Subsequently, warfarin therapy should be considered for patients at high embolic risk, including those with echocardiographic evidence of mobile and protruding thrombi, severe left ventricular dysfunction or prior emboli. In patients with acute infarction, aspirin is recommended for preventing coronary reocclusion and reinfarction. Although anticoagulants may also be of benefit for this purpose, their use is still controversial.(ABSTRACT TRUNCATED AT 250 WORDS)
We retrospectively and prospectively reviewed the incidence of stroke in 105 patients with systemic lupus erythematosus (SLE). Stroke occurred in 14 (15%) of 91 consecutive patients with documented SLE; nine (64%) of the 14 had multiple cerebral infarcts. Factors associated with stroke and the frequency of stroke were systemic thrombosis (30%), elevated partial thromboplastin time (36%), spontaneous abortion (50%), age over 60 years (57%), transient ischemic attacks (57%), previous stroke (64%), and cardiac valvular disease (86%). The major period of risk for the first stroke was during the first 5 years of SLE. The most frequent etiology was a cardiogenic embolus or an antibody-mediated hypercoagulable state, with cerebral vasculitis occurring only in association with infection. Because of the decreased fibrinolysis seen in patients with SLE, anticoagulant therapy may be the most effective preventive treatment currently available. Anticoagulant therapy seemed to prevent recurrent focal cerebral ischemia in our patients and was associated with relatively few and minor complications. Patients with a history of transient ischemic attacks or cardiac valvular lesions are at high (57% and 87%, respectively) risk of stroke. Patients who have had a stroke are at high (64%) risk for a recurrent stroke. Anticoagulant therapy is recommended for all of these patients.
We report the results of the Ticlopidine Aspirin Stroke Study, a blinded trial at 56 North American centers that compared the effects of ticlopidine hydrochloride (500 mg daily) with those of aspirin (1300 mg daily) on the risk of stroke or death. The medications were randomly assigned to 3069 patients with recent transient or mild persistent focal cerebral or retinal ischemia. Follow-up lasted for two to six years. The three-year event rate for nonfatal stroke or death from any cause was 17 percent for ticlopidine and 19 percent for aspirin--a 12 percent risk reduction (95 percent confidence interval, -2 to 26 percent) with ticlopidine (P = 0.048 for cumulative Kaplan-Meier estimates). The rates of fatal and nonfatal stroke at three years were 10 percent for ticlopidine and 13 percent for aspirin--a 21 percent risk reduction (95 percent confidence interval, 4 to 38 percent) with ticlopidine (P = 0.024 for cumulative Kaplan-Meier estimates). Ticlopidine was more effective than aspirin in both sexes. The adverse effects of aspirin included diarrhea (10 percent), rash (5.5 percent), peptic ulceration (3 percent), gastritis (2 percent), and gastrointestinal bleeding (1 percent). With ticlopidine, diarrhea (20 percent), skin rash (14 percent), and severe but reversible neutropenia (less than 1 percent) were noted. The mean increase in total cholesterol level was 9 percent with ticlopidine and 2 percent with aspirin (P less than 0.01). The ratios of high-density lipoprotein and low-density lipoprotein to total cholesterol were similar in both treatment groups. We conclude that ticlopidine was somewhat more effective than aspirin in preventing strokes in this population, although the risks of side effects were greater.
After tissue heart valve replacement 108 patients were randomised to standard anticoagulant control with rabbit brain thromboplastin (Dade C reagent, therapeutic range 18-24 s; international normalised ratio 2.5-40) and 102 to a less intensive regimen controlled with human brain thromboplastin (Manchester Comparative Reagent, therapeutic range 26-30 s; INR 2.0-2.25). Treatment was continued for three months, outcome measures being major or minor embolism or haemorrhage. 2 patients in each group had major embolic events and 11 in each group had minor embolic events. The 95% confidence intervals on the differences are -3.4% to 3.2% for major embolism and -9.3% to 8.2% for minor embolism. Haemorrhagic complications were significantly more frequent with standard treatment (15 patients) than with the less intensive regimen (6 patients); and of the 5 patients with major haemorrhagic complications, all were in the standard treatment group, again a significant difference. The less intensive regimen is thus no less effective and safer than standard anticoagulant therapy in patients with tissue heart valve replacement.
Between July 1979 and December 1984, 785 patients received 815 St. Jude Medical valve prostheses. Valve-related mortality in the follow-up period was due to thromboembolism in seven cases, anticoagulant-related hemorrhage in three and perivalvular leak in two. Freedom from valve-related death or reoperation at 3 years was 96.4% for aortic valve replacement and 98.3% for mitral valve replacement. The overall rate of thromboembolism was 2.6%/patient-year with warfarin, 9.2%/patient-year with antiplatelet medication and 15.6%/patient-year in patients with no anticoagulant therapy. One episode of thrombotic obstruction of a mitral valve, in a patient receiving no anticoagulant therapy, resulted in an occurrence rate of such obstruction of 0.22%/patient-year. Valve replacement with the St. Jude valve produced excellent clinical results, but long-term anticoagulation with warfarin was required to minimize thromboembolic complications. The use of antiplatelet agents alone provided inadequate protection.
The effect of very-low-dose aspirin as an antithrombotic agent was evaluated blindly in 301 patients who had recently undergone carotid endarterectomy. After randomization, 150 patients received aspirin and 151 received placebo. The two groups were comparable with regard to age, sex, blood pressure, previous cerebrovascular events, and smoking habits. The effect of the study medication on platelet aggregation was measured twice in each patient during the first 2 months and at each follow-up visit; the dose was individually adjusted. In 76% of the patients receiving aspirin, 50 mg/day gave satisfactory platelet inhibition, 13% needed 60 mg/day, 8% needed 70 mg/day, and 3% needed 100 mg/day. Platelet aggregation was found to be inhibited in only 1.2% of the measurements in the patients receiving placebo. Observation during treatment averaged 21 months; total intention-to-treat follow-up averaged 25 months. For the combined outcome events of transient ischemic attack, stroke, acute myocardial infarction, and vascular death, aspirin reduced risk by 11% (95% confidence limits: -38% to 48%, p greater than 0.1). Thus, there was no significant effect of very-low-dose aspirin in our trial.
Randomized control trials of antiplatelet agents in the prevention of stroke following transient ischemic attacks have had conflicting results. The decision to employ aspirin instead of placebo as the control regimen in trials testing newer antiplatelet agents emphasizes the need for an accurate estimate of the efficacy of older drugs. A meta-analysis of seven randomized control trials comparing aspirin and/or sulfinpyrazone or dipyridamole with placebo was performed. For aspirin compared with placebo, a nonsignificant reduction in stroke of 15% (odds ratio 0.85, 95% confidence interval 0.60-1.19; chi 2 = 0.78, p greater than 0.30) was found. For aspirin combined with sulfinpyrazone or dipyridamole compared with placebo, a 39% reduction in stroke was observed (odds ratio 0.61, 95% confidence interval 0.39-0.95; chi 2 = 4.22, p less than 0.05); at the same time a 350% increase in gastrointestinal hemorrhage or peptic ulcer was noted (odds ratio 3.5, 95% confidence interval 1.26-9.75; chi 2 = 4.61, p less than 0.05). A trend in reduction of strokes for men was observed (odds ratio 0.58, 95% confidence interval 0.32-1.07; chi 2 = 2.52, p less than 0.15) for any regimen containing aspirin. The significant benefit of aspirin-combination therapy on stroke must be interpreted cautiously because of a number of possible biases. It is still conceivable that aspirin alone may decrease the incidence of stroke by as much as 40%, but a sample of greater than 13,000 patients would be needed to confirm the benefit observed in our analysis.
One thousand four Medtronic Hall valves (601 mitral, 398 aortic, and five tricuspid) were implanted in 847 patients between December 1979 and June 1987. Total experience at the end of June 1987 was 2,640 patient-years of follow-up. Prothrombin time ratios were reviewed for all patients (16,866 observations), and these ratios were found to be therapeutically low (median international normalized ratio, 2.6) and highly variable (lower 10th percentile, 1.6; upper 10th percentile, 3.9). During the follow-up period, there were no valvular thromboses; the 95% confidence limit for the risk of thrombosis (0.14 per 100 patient-years) is below that reported for other mechanical prostheses. Sixty percent of all thromboembolic events left no residual deficit, and 75% of all bleeding events did not require treatment. Only 11% of thromboembolic events and 7% of bleeding events were fatal. The linearized rate of fatal bleeding was 0.2% per year, and the linearized rate of moderate to severe bleeding was 0.5% per year. Five-year actuarial embolic-free rates were 92%, 84%, and 83% for aortic, mitral, and double valves, respectively. The low risk of valvular thrombosis and of serious thromboembolic events in the Medtronic Hall valve, regardless of the range and variability of anticoagulation, offers greater patient safety than other mechanical prostheses, provides a credible alternative to bioprostheses, and may be particularly relevant to third-world populations.
To examine the effect of short-term, high-dose anticoagulation on the subsequent occurrence of left ventricular (LV) thrombi after a first anterior wall acute myocardial infarction (AMI), 21 patients received placebo and 21 high-dose anticoagulants during the first 10 days of the acute infarction. They were studied with cross-sectional echocardiography 10 days and 1-3 and 6 months post infarction. At 1 month, 6 of 7 thrombi present in the placebo group at 10 days were still visible. No thrombi were detected at 10 days in the anticoagulation group, but 6 patients had developed a LV thrombus at 1 month. These 12 patients with LV thrombi were subsequently treated with oral warfarin for 2 months, after which all thrombi had disappeared. Warfarin was then discontinued, and a thrombus had recurred in 5 patients after 6 months. Apical akinesis at 10 days a predictor for thrombus with a sensitivity and specificity of 100% and 72.2% respectively.
Three of the 13 patients with LV thrombi suffered stroke in contrast to none without thrombi (P=0.025).
We conclude that after discontinuation of short-term high-dose anticoagulation therapy in anterior AMI, LV thrombi may develop rapidly and lead to embolic complications, particularly in patients with persisting apical akinesis.