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Characteristics of nonsustained ventricular tachycardia (nsVT) episodes. A, Time of occurrence during the day of the first and second nsVT episode used for analysis. B, Summary data of the number of complexes in the nsVT episodes analyzed (left) and the heart rate during the nsVT episodes (right). N=43 (ICM+nsVT), 37 (DCM+nsVT). 2-tailed t test. DCM indicates dilated cardiomyopathy; and ICM, ischemic cardiomyopathy. Downloaded from http://ahajournals.org by on July 7, 2022
Source publication
Background
An increase in beat‐to‐beat variability of repolarization (BVR) predicts arrhythmia onset in experimental models, but its clinical translation is not well established. We investigated the temporal changes in BVR before nonsustained ventricular tachycardia (nsVT) in patients with implantable cardioverter defibrillator (ICD).
Methods and...
Contexts in source publication
Context 1
... first nsVT episode of the day, used in subsequent analysis, occurred at all hours of the day without distinguishable preferred time-of-day patterns in both groups (Figure 2A). There tended to be more nsVT episodes in ICM+nsVT than DCM+nsVT, but this was not statistically significant (ICM+nsVT: 10.1±6.4 versus DCM+nsVT: 7.9±4.7, ...
Context 2
... The number of complexes and rate of the nsVT episodes considered for analysis were comparable (P=0.676 and P=0.582, Figure 2B). Figure 3B). ...
Context 3
... P<0.001 and DCM: 1.43±0.28 ms, P=0.003), although the resting heart rate was not different ( Figure S2). Figure 4A illustrates the temporal analysis of QT-BVR before the occurrence of a nsVT event (top insert), or matched timepoints in ICD candidates without nsVT, and examples of the Poincaré plots at 30-, 5-, and 1-minute before the nsVT used for QT-BVR calculation (bottom insert). ...
Context 4
... P=0.003), although the resting heart rate was not different ( Figure S2). Figure 4A illustrates the temporal analysis of QT-BVR before the occurrence of a nsVT event (top insert), or matched timepoints in ICD candidates without nsVT, and examples of the Poincaré plots at 30-, 5-, and 1-minute before the nsVT used for QT-BVR calculation (bottom insert). The timepoints used for analysis in the control groups were matched to nsVT-timepoints of the respective ICD patients in Figure 2A. The time-of-day profile matched timepoints are presented in Figure S3 and reflect the random distribution of nsVT in ICD patients (P=0.989). ...
Citations
... P2Y12-ADPRB is supposed to improve ADP-induced platelet hyperreactivity. In a multicenter international prospective registry of 7,824 enrolled patients, the use of P2Y12-ADPRB was associated with lower mortality and shorter duration of mechanical ventilation: only 9% of patients were admitted to the ICU [52]. In another prospective case series of only five patients, improvement of blood oxygenation was observed with combined antiplatelet therapy including P2Y12-ADPRB [53]. ...
... Temporal variability in repolarization, quantified as short-term variability (STV) of repolarization, reflects the state of the repolarization reserve (Thomsen et al., 2004;Varro and Baczko, 2011). STV has been demonstrated to increase leading up to an episode of TdP in the CAVB dog (Varkevisser et al., 2012;Wijers et al., 2017), in pigs with cardiac ischemia (Amoni et al., 2022) as well as before spontaneously occurring ventricular arrhythmias in patients (Smoczynska et al., 2020b). Secondly, TdP arise from a location with a high spatial dispersion repolarization (SDR), and insusceptibility for TdP is associated with the absence of such regions of high SDR . ...
Background: An electrical storm of Torsade de Pointes arrhythmias (TdP) can be reproducibly induced in the anesthetized chronic AV-block (CAVB) dog by infusion of the I Kr -blocker dofetilide. Earlier studies showed that these arrhythmias 1) arise from locations with high spatial dispersion in repolarization (SDR) and 2) can be suppressed by high-rate pacing. We examined whether suppression of TdP by high-rate pacing is established through a decrease in SDR in the CAVB dog.
Methods: Dofetilide (25 μg/kg in 5 min) was administered to 5 anesthetized CAVB dogs to induce TdP arrhythmias. During the experiments, animals were continuously paced from the right ventricular apex at 50 beats/minute (RVA50). Upon TdP occurrence and conversion, RVA pacing was consecutively set to 100, 80 and 60 beats/minute for 2 min, referred to as pacing blocks. To determine the additional anti-arrhythmic effects of HRP over defibrillation alone, the number of arrhythmic events and SDR at RVA100 were compared to data from three previously conducted experiments, in which dogs underwent the same experimental protocol but were paced at RVA60 upon TdP occurrence (RVA60 retro ). In all experiments, recordings included surface electrocardiogram and mapping by 56 intramural needles, each recording four electrograms, evenly inserted into the ventricular walls and septum. For each pacing block, the number of ectopic beats (EB), and TdP severity were scored. SDR was quantified as the average difference in repolarization time within four squared needles (SDR cubic ).
Results: In 4 out of 5 animals, pacing at RVA100 suppressed TdP occurrence. One dog could not be converted by defibrillation after the initial TdP. Compared to RVA50, pacing at RVA100, but not RVA80 and RVA60, significantly reduced the TdP score (78 ± 33 vs . 0 ± 0, p < 0.05 and vs . 12.5 ± 25 and 25 ± 50, both p > 0.05). The reduction in TdP score was reflected by a significant decrease in SDR cubic (125 ± 46 ms before TdP vs . 49 ± 18 ms during RVA100, p < 0.05), and SDR was smaller than in the RVA60 retro animals (101 ± 52 ms, p < 0.05 vs . RVA100).
Conclusion: In CAVB dogs, high-rate pacing effectively suppresses TdP, which, at least in part, results from a spatial homogenization of cardiac repolarization, as reflected by a decrease in SDR.
... In the chronic atrioventricular block (CAVB) dog model, in which Torsade de Pointes (TdP) arrhythmias can be provoked by pharmacological block of repolarizing currents following volume-overloadrelated cardiac remodelling, 6 STV at baseline identified subjects that developed SCD during follow-up. 7 Moreover, STV increased shortly before drug-induced TdP, predicting imminent VA. 7,8 Similar results were obtained in humans, where elevated STV at baseline was associated with the occurrence of VA in patients with long QT syndrome, non-ischaemic cardiomyopathy, and structural heart disease, and could predict impending VA. [9][10][11][12][13][14] To continuously monitor the arrhythmic risk by cardiac implantable devices, a fully automatic method to determine STV on the intracardiac electrogram (STV-ARI auto ) has been developed. This method demonstrated high efficacy in predicting VA in the CAVB dog model. ...
... 6,8 These patterns hold true in human studies as well: in patients with ischaemic and non-ischaemic cardiomyopathy, STV-QT increased just before VA, while QT and QTc-intervals did not. 12,13 Therefore, the findings in the current study-indicating that STV, unlike QT(c)-intervals and ST-elevation, signals imminent VA during acute MI-are consistent with literature. ...
Aims
An automated method for determination of short-term variability of repolarization (STV) on intracardiac electrograms (STV-ARIauto) has previously been developed for arrhythmic risk monitoring by cardiac implantable devices, and has proved effective in predicting ventricular arrhythmias (VA) and guiding preventive high-rate pacing (HRP) in a canine model. Current study aimed to assess (1) STV-ARIauto in relation to VA occurrence and secondarily (2a) to confirm the predictive capacity of STV from the QT-interval and (2b) explore the effect of HRP on arrhythmic outcomes in a porcine model of acute myocardial infarction (MI).
Methods and results
MI was induced in 15 pigs. In 7/15 pigs STV-QT was assessed at baseline, occlusion, one minute before VA and just before VA. 8/15 pigs were additionally monitored with an electrogram catheter in the right ventricle, underwent echocardiography at baseline and reperfusion, and were randomized to paced or control group. Paced group received atrial pacing at 20 beats/minute faster than sinus rhythm one minute after occlusion. STV increased prior to VA in both STV modalities. The percentage change in STV from baseline to successive timepoints correlated well between STV-QT and STV-ARIauto. HRP did not improve arrhythmic outcomes and was accompanied by a stronger decrease in ejection fraction.
Conclusion
STV-ARIauto values increase before VA onset, alike STV-QT in a porcine model of MI, indicating imminent arrhythmias. This highlights the potential of automatic monitoring of arrhythmic risk by cardiac devices through STV-ARIauto and subsequently initiate preventive strategies. Continuous HRP during onset of acute MI did not improve arrhythmic outcomes.
... 7 With new analysis tools, he demonstrated how temporal changes in beat-to-beat variability of repolarization predict imminent arrhythmias in patients. 8 In early 2021, he returned to South Africa to resume his clinical training to become a cardiologist. Despite his clinical duties, he managed to continue with his research data analysis and writing in order to finish manuscripts and prepare his PhD thesis. ...
... The study found that patients with ischemic cardiomyopathy tended to have an increased incidence of non-sustained ventricular tachycardia compared to those with dilated cardiomyopathy; however, due to small sample sizes, the difference lacked statistical significance. Further studies are needed to determine whether early investigations such as Holter monitoring for beat variability or interventions such as prophylactic ICD placement can aid in preventing mortality in these high-risk populations [14]. ...
A 71-year-old female visiting from Colombia presented to the emergency room with a productive cough, subjective fever, and chills for the past three days. Baseline EKG demonstrated a QT interval of 385 milliseconds with left ventricular hypertrophy and T wave inversions in leads V4, V5, and V6. Azithromycin was administered, and she was subsequently found to have torsades de pointes (TdP) on telemetry. In high-risk individuals, medications with reduced effects on cardiac conduction should be considered to avoid potentially lethal reactions. This case highlights the importance of clinical history prior to the administration of medications that have a propensity to cause abnormalities in cardiac conduction. Our patient had a grossly normal QT interval prior to the administration of azithromycin; however, she subsequently developed torsades de pointes. The patient was on telemetry monitoring, and cardiopulmonary resuscitation was quickly initiated as she was in a hospitalized setting; however, in an outpatient community setting, she likely would not have survived. By examining all the elements which contribute to QT prolongation, clinicians can have a deeper understanding of the complexities, particularly in individuals with multiple co-morbid conditions prior to the administration of medications that have a propensity to affect the QT interval.
Ventricular arrhythmia (VT/VF) can complicate acute myocardial ischemia (AMI). Regional instability of repolarization during AMI contributes to the substrate for VT/VF. Beat-to-beat variability of repolarization (BVR), a measure of repolarization lability increases during AMI. We hypothesized that its surge precedes VT/VF. We studied the spatial and temporal changes in BVR in relation to VT/VF during AMI. In 24 pigs, BVR was quantified on 12-lead electrocardiogram recorded at a sampling rate of 1 kHz. AMI was induced in 16 pigs by percutaneous coronary artery occlusion (MI), whereas 8 underwent sham operation (sham). Changes in BVR were assessed at 5 min after occlusion, 5 and 1 min pre-VF in animals that developed VF, and matched time points in pigs without VF. Serum troponin and ST deviation were measured. After 1 mo, magnetic resonance imaging and VT induction by programmed electrical stimulation were performed. During AMI, BVR increased significantly in inferior-lateral leads correlating with ST deviation and troponin increase. BVR was maximal 1 min pre-VF (3.78 ± 1.36 vs. 5 min pre-VF, 1.67 ± 1.56, P < 0.0001). After 1 mo, BVR was higher in MI than in sham and correlated with the infarct size (1.43 ± 0.50 vs. 0.57 ± 0.30, P = 0.009). VT was inducible in all MI animals and the ease of induction correlated with BVR. BVR increased during AMI and temporal BVR changes predicted imminent VT/VF, supporting a possible role in monitoring and early warning systems. BVR correlated to arrhythmia vulnerability suggesting utility in risk stratification post-AMI.
NEW & NOTEWORTHY The key finding of this study is that BVR increases during AMI and surges before ventricular arrhythmia onset. This suggests that monitoring BVR may be useful for monitoring the risk of VF during and after AMI in the coronary care unit settings. Beyond this, monitoring BVR may have value in cardiac implantable devices or wearables.
