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When an AED meets an ICD... Automated external defibrillator. Implantable cardioverter defibrillator
Abstract
The chances of prehospital care providers being confronted with a patient with an implantable cardioverter defibrillator (ICD) are increasing and so care providers must receive proper training. Based on observations made during the resuscitation of a patient with an ICD using an automated external defibrillator (AED) some technical features and possible interactions of ICDs and AEDs are highlighted. Furthermore, we discuss the key points of basic knowledge, safety, and treatment protocols for cardiac arrest and other situations required for practical training in the ICD for prehospital care providers.
... torsades de pointes and in patients with an internal cardioverter defibrillator or ICD) have an impact on the RAA accuracy. [8][9][10][11][12][13] The American ...
... Since 1992, this local quality assurance program is performed by one of the authors (PC). 10,13,15 In February 2012 the three first tier units of the Ghent Fire Brigade started using ZOLL AED PRO ® devices. In November 2012 the Wetteren Fire Brigade (with two units) made the same switch. ...
The rhythm analysis algorithm (RAA) of automated external defibrillators (AEDs) may be deceived by many factors. In this observational study we assessed RAA accuracy in prehospital interventions. For every rhythm analysis judged to be inaccurate, we looked for causal factors and estimated the impact on outcome.
In 135 consecutive patients, two physicians reviewed 837 rhythm analyses independently. When they disagreed, a third physician made the final decision.
Among 148 shockable episodes, 23 (16%) were not recognized by the RAA due to external artefacts (n=7), fine ventricular fibrillation (VF; n=7), RAA error without external artefacts (n=4) or a combination of factors (n=5). In six cases the omitted/delayed shock was judged to be of clinical relevance: survival with some neurological deficit (n=4), death without regaining consciousness (n=1) and no restoration of spontaneous circulation (n=1). In 689 non-shockable episodes, the RAA decided "shockable" 25 times (4%). This wrongful decision was due to external artefacts (n=9), a concurrent shock of an internal cardioverter defibrillator (n=1), RAA error without external artefacts (n=13) or a combination of factors (n=2). Fifteen spurious shocks were delivered. As these non-shockable rhythms did not deteriorate after the shock, we assumed that no significant harm was done.
Up to 16% of shockable rhythms were not detected and 4% of non-shockable rhythms were interpreted as shockable. Therefore, all AED interventions should be reviewed. Feedback to caregivers may avoid future deleterious interactions with the AED, whereas AED manufacturers may use this information to improve RAA accuracy. This approach may improve the outcome of some VF patients.
Copyright © 2014. Published by Elsevier Ireland Ltd.
Defibrillation is one of the few interventions known to favorably impact survival in cardiac arrest. In witnessed arrest, survival improves with defibrillation as early as possible, whereas it may improve outcomes to administer high-quality chest compressions for 90 seconds before defibrillation in unwitnessed arrest. Minimizing pre-, peri-, and post-shock pauses has been shown to have mortality benefits. Refractory ventricular fibrillation has high mortality rates, and there is ongoing research into promising adjunctive treatment modalities. There remains no consensus on optimal pad positioning and defibrillation energy level, however, recent data suggest anteroposterior pad placement may be superior to anterolateral placement.
Background:
Implantable cardioverter-defibrillators (ICDs) are a well-established therapy for patients at risk of life-threatening ventricular arrhythmias. With rising implant rates, the risk of a rescuer performing chest compressions during discharge is increasing, leading to concerns over rescuer safety from the resultant leakage current. More recently, subcutaneous ICDs (S-ICD) have been developed, which utilise a higher energy and more superficial electrodes compared with transvenous ICDs (T-ICD), raising safety concerns further.
Objective:
We measured the current a rescuer would potentially receive from T-ICDs and S-ICDs if they were in contact with the patient at the time of ICD discharge to assess its magnitude in relation to international safety standards.
Methods:
Surface voltages adjacent to ICD electrodes were measured on patients undergoing defibrillation threshold checks. Rescuer current was then calculated assuming a total rescuer circuit impedance of 1696 Ω.
Results:
Twenty-five patients were recruited. Rescuer current from S-ICDs was significantly higher than those from T-ICDs (S-ICD: Median RMS 135 mA range 91 mA-164 mA, T-ICD: Median RMS 31 mA, range 9 mA-75 mA, P < 0.0001). Surface voltages (median RMS) to which the rescuer is likely to be exposed are higher when performing chest compressions from the patient's left side compared with the right (127 V vs 67 V respectively, 95% CI of difference -34 V to -67 V, P < 0.0001).
Conclusions:
Rescuers performing chest compressions on ICD patients are at risk from leakage current, particularly from S-ICDs. Chest compressions should be performed from the opposite side to the ICD to reduce rescuer risk.
A resuscitation in patients with an implanted pacemaker or
an implanted cardioverter-defibrillator is often not caused by a
device dysfunction, but more commonly caused by a progress in
heart failure or ischemia. In the presence of a severe device
dysfunction as lead fracture, dislodgement, battery depletion or
capacitor problems, however, resuscitation may become necessary.
Although this is a less frequent emergency, it requires
sufficient knowledge on devices and programming, to rapidly
solve the underlying problem leading to resuscitation. In
patients with an implanted cardioverter-defibrillator
ventricular tachycardias below the detection rate, which lead
according to the literature in up to 9% of the cases to
resuscitation, always have to be kept in mind. Since it does not
represent device failure, reprogramming of the device can solve
the problem. Electrical storm in patients with an ICD occurs in
approximately 10% of all ICD patients during further follow-up
and requires specific knowledge on treatment and acute
reprogramming in order not to aggravate the situation and to
prevent need of resuscitation.
As more patients have pacemakers and internal cardioverter defibrillators implanted, and live longer with these and other life-extending therapies, the utility of these devices and the potential for malfunction become meaningful to physicians. This article presents a basic understanding of the reasons for implantation, how the devices function, and what to do to help improve patient care if a problem occurs.
Implantable cardioverter-defibrillators (ICDs) have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. ICDs are implanted using techniques similar to standard pacemaker implantation. They not only provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, but also provide antitachycardia pacing for monomorphic ventricular tachycardia and antibradycardia pacing. Devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Intensivists are increasingly likely to encounter patients with ICDs. Electrosurgery can be safely performed in ICD patients as long as the device is deactivated before the procedure and reactivated and reassessed immediately afterward. Prompt and skilled intervention can prove to be life-saving in patients presenting with ICD-related emergencies, including lack of response to ventricular tachyarrhythmias, pacing failure, and multiple shocks. Recognition and treatment of tachyarrhythmia can be temporarily disabled by placing a magnet on top of an ICD. The presence of an ICD should not deter standard resuscitation techniques. Multiple ICD discharges in a short period of time constitute a serious situation. Causes include ventricular electrical storm, inefficient defibrillation, nonsustained ventricular tachycardia, and inappropriate shocks caused by supraventricular tachyarrhythmias or oversensing of signals. ICD system infection requires hardware removal and intravenous antibiotic therapy. Deactivation of an ICD with the consent of the patient or relatives is reasonable and ethical in terminally ill patients.
The field of defibrillation is one of the most rapidly advancing areas in resuscitation. Defibrillation is also one of the most promising interventions for achieving improved survival from cardiac arrest. The purpose of this article is to provide an overview of the science and clinical applications of defibrillation.
Despite recent therapeutic advances, SCD remains the leading cause of mortality in industrialized nations. The most frequent cause of SCD is ventricular tachyarrhythmias in the setting of advanced structural heart disease due to chronic coronary heart disease or idiopathic dilated cardiomyopathy. Although high-risk groups can be prospectively identified, attempts at primary prevention have been largely unsuccessful. Effective treatment strategies for SCD survivors include antiarrhythmic drug therapy guided by programmed stimulation, endocadial resection, and ICDs. Device therapy has proven extremely effective in preventing recurrent sudden death from ventricular tachyarrhythmias. Widespread application of ICD therapy, perhaps even to include members of high-risk populations that have not experienced cardiac arrest, will depend on many factors including the demonstration that device therapy improves total mortality, not just arrhythmia-related mortality, reduction in cost, and improvements in the devices themselves. Some of the important characteristics of the optimal ICD of the future are nonthoracotomy lead placement; subpectoral generator placement; multiprogrammable, tiered therapy; improved diagnostic specificity, whether based on electrogram or hemodynamic-sensing algorithms; improved integration of brady- and tachy-sensing systems; and enhanced electrogram storage capability with trans-telephonic retrieval of electrogram recordings. The creation of this ideal ICD will obviously require continued technological advances; however, given the tremendous improvements realized over the first three generations of ICD systems, optimism for the future seems warranted.
The automatic implantable cardioverter defibrillator (AICD) is a proven therapy for preventing the potentially lethal consequences of recurrent ventricular arrhythmias. Given the ever-increasing number of patients who have these devices, it can be anticipated that an increasing number of these patients will likely present to emergency departments with problems associated with this therapy. We review normal automatic implantable cardioverter defibrillator function and focus on the evaluation and treatment of problems that may bring a patient to the ED. Included are interaction with the device by magnets, assessment of the propriety of shocks received by the patient, and what to do when patients state they have received a shock from the device. An algorithmic approach is presented to facilitate management of these patients.
The automatic implantable cardioverter-defibrillator continuously monitors the heart, identifies malignant ventricular tachyarrhythmias and then delivers electrical countershock to restore normal rhythm. There are two defibrillating electrodes which are also used for waveform analysis; one is located in the superior vena cava and the other is placed over the cardiac apex. A third bipolar right ventricular electrode is used for rate counting and R wave synchronization. When ventricular fibrillation occurs, a 25 J pulse is delivered; when ventricular tachycardia faster than the preset rate is detected, the discharge is R wave-synchronized. The clinical evaluation study of this therapeutic method began in February 1980 in patients with recurrent refractory life-threatening ventricular tachyarrhythmias. So far, the device has been implanted in nearly 500 patients with a follow-up period of up to 59 months. The risks and complications associated with this treatment were found to be moderate. Actuarial analysis has demonstrated significant impact on the survival rate of the patients receiving implants with 1 year arrhythmic mortality rate reduced to 2% or less in all groups analyzed. The available data indicate that the automatic cardioverter-defibrillator can reliably identify and correct potentially lethal ventricular tachyarrhythmias, leading to a substantial improvement in survival in properly selected high risk patients.
Survival to hospital discharge was related to the clinical history and emergency care system factors in 285 patients with witnessed cardiac arrest due to ventricular fibrillation. Only the emergency care factors were associated with differences in outcome. Both the period from collapse until initiation of basic life support and the duration of basic life support before delivery of the first defibrillatory shock were shorter in patients who survived compared with those who died (3.6 +/- 2.5 versus 6.1 +/- 3.3 minutes and 4.3 +/- 3.3 versus 7.3 +/- 4.2 minutes; p less than 0.05). A linear regression model based on emergency response times for 942 patients discovered in ventricular fibrillation was used to estimate expected survival rates if the first-responding rescuers, in addition to paramedics, had been equipped and trained to defibrillate. Expected survival rates were higher with early defibrillation (38 +/- 3%; 95% confidence limits) than the observed rate (28 +/- 3%). Because outcome from cardiac arrest is primarily influenced by delays in providing cardiopulmonary resuscitation and defibrillation, factors affecting response time should be carefully examined by all emergency care systems.
Several studies have examined the effect of early defibrillation by basic EMTs on patient survival. Although the studies have a common theme of early basic EMT defibrillation, they are diverse in locations, devices, control groups, caregivers, and protocols. They provide a confusing array of information that is difficult to review, synthesize, and interpret. Metaanalysis allows data pooling of these primary studies to combine results and statistically compare the observed variation in study outcomes. The purpose of this metaanalysis was to examine the published studies of early basic EMT defibrillation to learn whether this treatment has an effect on survival of out-of-hospital cardiac arrest. Analysis of the 10 studies that met inclusion criteria showed that despite variations in design, the overall effect size for all the studies was .092, indicating a 9.2% increase in survival over what would have been expected had the EMT-Ds not intervened.
