Appropriate Shock In Patients Research Articles

Lack of Prognostic Value of T-Wave Alternans for Implantable Cardioverter-Defibrillator Benefit in Primary Prevention.

New methods to identify patients who benefit from a primary prophylactic implantable cardioverter-defibrillator (ICD) are needed. T-wave alternans (TWA) has been shown to associate with arrhythmogenesis of the heart and sudden cardiac death. We hypothesized that TWA might be associated with benefit from ICD implantation in primary prevention. In the EU-CERT-ICD (European Comparative Effectiveness Research to Assess the Use of Primary Prophylactic Implantable Cardioverter-Defibrillators) study, we prospectively enrolled 2327 candidates for primary prophylactic ICD. A 24-hour Holter monitor reading was taken from all recruited patients at enrollment. TWA was assessed from Holter monitoring using the modified moving average method. Study outcomes were all-cause death, appropriate shock, and survival benefit. TWA was assessed both as a contiguous variable and as a dichotomized variable with cutoff points <47 μV and <60 μV. The final cohort included 1734 valid T-wave alternans samples, 1211 patients with ICD, and 523 control patients with conservative treatment, with a mean follow-up time of 2.3 years. TWA ≥60 μV was a predicter for a higher all-cause death in patients with an ICD on the basis of a univariate Cox regression model (hazard ratio, 1.484 [95% CI, 1.024-2.151]; P=0.0374; concordance statistic, 0.51). In multivariable models, TWA was not prognostic of death or appropriate shocks in patients with an ICD. In addition, TWA was not prognostic of death in control patients. In a propensity score-adjusted Cox regression model, TWA was not a predictor of ICD benefit. T-wave alternans is poorly prognostic in patients with a primary prophylactic ICD. Although it may be prognostic of life-threatening arrhythmias and sudden cardiac death in several patient populations, it does not seem to be useful in assessing benefit from ICD therapy in primary prevention among patients with an ejection fraction of ≤35%.

Fragmented QRS complex as a predictor of appropriate shocks in patients undergoing cardiac resynchronization therapy and defibrillator. A chronicle of a shock foretold?

Abstract Introduction Cardiac resynchronization therapy (CRT) has demonstrated to reduce mortality and hospitalization for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) in specific subgroups of patients Moreover, adding an implantable cardioverter defibrillator (ICD) to CRT (CRT-D) has demonstrated to reduce the risk of sudden cardiac death in specific subgroups of patients. However, patients undergoing CRT-D are a very heterogeneous group. In the recent years, several clinical findings, such as fragmentation of the QRS complex (fQRS), have been reported as potential prognostic factors in various cardiac diseases. Nevertheless, the evidence to support the prognostic significance of fQRS in patients undergoing CRT-D remains to be scarce. Purpose The objective of this study is to evaluate if the presence of pre-implantation fQRS predicts appropriate ICD shocks in patients undergoing CRT-D implantation. Methods Consecutive patients undergoing CRT-D implantation were prospectively included from October 2009 to December 2022. Demographic, clinical, electrocardiographic and echocardiographic variables as well as appropriate ICD shock events were collected from electronic clinical records and telephone interview. Fragmentation of the QRS complex was defined by the presence of different RSR′ patterns including an additional R-wave (R′), notching of the R-wave and S-wave or the presence of more than 1R′ in two contiguous leads corresponding to a main coronary artery territory. Results A total of 180 patients were included. Mean age at the device implantation was 69.9 years (standard deviation, SD ±9.6 years), 80.6% were male, 63.8% presented hypertension and 40.0% were diabetic. The aetiology of the LV systolic dysfunction was non-ischaemic in 45.6% of the patients and ischaemic in 54.6%. 43.9% had prior history of acute myocardial infarction, while myocardial scar was described in 45.6% of the patients. Pre-implantation fQRS was found in 61.7% of the patients. Mean LVEF at baseline was 23.6%. The median follow-up time was 34.8 months. At the end of the follow-up, 30.5% patients died. 9.8% of the patients presented appropriate ICD shocks (9.2% in patients with pre-implantation fQRS and 0.6% in patients without pre-implantation fQRS). A multivariate survival analysis using Cox regression showed that presence of pre-implantation fQRS complex was a powerful independent predictor for appropriate ICD shocks (HR 8.36; 95% CI 1.08–64.32). Kaplan-Meier curves for appropriate shocks regarding pre-implantation fQRS status are presented in Figure 1. Conclusions According to our results, pre-implantation fQRS seems to be a strong independent predictor for appropriate ICD shocks after CRT-D implantation. Therefore, these patients could benefit from a more rigorous follow-up as they present higher risk of an arrhythmic event. However, further research is needed to confirm these findings.Figure 1.Kaplan-Meier curves

Abstract 9374: Machine Learning on Automated Measurement of 12 Leads Electrocardiography Can Predict Appropriate Shock in Patients With Implantable Cardioverter Defibrillator

Introduction: Prediction for appropriate shock in patients with implantable cardioverter defibrillator (ICD) is still challenging. We tried to predict the shock by machine learning (ML) model on automated microvolt-level measurement of 12-leads electrocardiography (ECG). Hypothesis: ML on 12-leads ECG can predict appropriate ICD shock. Methods: Consecutive 177 patients (61.5±14.4years, 141males, organic heart disease: 121cases) with ICD were enrolled. ECG was measured by ECAPs12c system (Nihon-Koden) at ICD implantation. Shock was defined as appropriate ICD shock and anti-tachycardia overdrive pacing. Statistic significant predictors were extracted by univariate Cox regression analysis. Because of many correlation/confounding/multicollinearity among the predictors, multivariate Cox was not performed, and machine learning (ML) predictive model was utilized to compare the importance of the predictors. Results: Fifty-six patients were treated by appropriate shock during the observation period (median during implantation to shock: 1.85years). Thirteen significant predictors were extracted, and T-axis showed the smallest P value of univariate Cox (P=0.0007). Random Forest Classifier model demonstrated high accuracy (0.740) and T-axis showed the most important role to build the model. Receiver operating characteristics (ROC) curve analysis indicated the cut-off value as 105 degree, and Kapan-Meier curve analysis demonstrated T-axis ≥105 degree group showed worse prognosis than T-axis &gt;105 degree group. Conclusions: ML of microvolt-level measurement of 12-leads ECG potentially had high predictive value for appropriate shock of ICD, and T-axis played an essential role for the prediction.

Impact of signal-averaged electrocardiography findings on appropriate shocks in prophylactic implantable cardioverter defibrillator patients with nonischemic systolic heart failure

BackgroundAppropriate shock therapy is associated with subsequent all-cause death in heart failure (HF) patients who receive an implantable cardioverter defibrillator (ICD) for the primary prevention of sudden cardiac death. To evaluate the impact of signal-averaged electrocardiography (SAECG) findings on appropriate shocks in prophylactic ICD patients with nonischemic systolic HF.MethodsWe studied 86 patients with nonischemic HF and a left ventricular ejection fraction ≤ 35% who underwent new ICD implantation for the primary prevention of sudden cardiac death. We excluded patients who had a previously implanted permanent pacemaker and patients who received cardiac resynchronization therapy with an ICD. SAECG was performed before implantation. Abnormal SAECG findings were defined if 2 of the following 3 conditions were identified: filtered QRS duration (fQRS) ≥ 114 ms, root-mean-square voltage during the last 40 ms of the fQRS (RMS 40) < 20 μV, and duration of the low-amplitude potentials < 40 μV (LAS 40) > 38 ms; additionally, patients with a QRS complex ≥ 120 ms who met both the RMS 40 and LAS 40 criteria were also considered to have abnormal SAECG findings. The primary outcome was the first occurrence of appropriate shock after implantation of the ICD. The secondary outcomes were the first occurrence of inappropriate shock and all-cause mortality.ResultsForty-two patients met the criteria for abnormal SAECG findings (49%). During a median follow-up period of 61 months, 17 patients (20%) died, 24 (28%) received appropriate shock therapy, and 19 (22%) received inappropriate shock therapy. There was a significantly higher incidence of appropriate shocks in patients with abnormal SAECG findings than in those with normal SAECG findings (log-rank test, p = 0.025). Multivariate analysis revealed that abnormal SAECG findings were independently associated with the occurrence of appropriate shock (hazard ratio 2.67, 95% confidential interval 1.14–6.26). However, abnormal SAECG findings were not related to inappropriate shock. There was no difference in the incidence of all-cause death between patients with abnormal and normal SAECG findings.ConclusionsOur results suggest that abnormal SAECG findings are associated with a high probability of appropriate shocks in prophylactic ICD patients with nonischemic systolic HF.

Corrigendum to: Milman A, et al. Time-to-first appropriate shock in patients implanted prophylactically with an implantable cardioverter-defibrillator: data from the Survey on Arrhythmic Events in BRUgada Syndrome (SABRUS).

Corrigendum to: Milman A, et al. Time-to-first appropriate shock in patients implanted prophylactically with an implantable cardioverter-defibrillator: data from the Survey on Arrhythmic Events in BRUgada Syndrome (SABRUS).

Time-to-first appropriate shock in patients implanted prophylactically with an implantable cardioverter-defibrillator: data from the Survey on Arrhythmic Events in BRUgada Syndrome (SABRUS).

Data on predictors of time-to-first appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with Brugada Syndrome (BrS) and prophylactically implanted ICD's are scarce. SABRUS (Survey on Arrhythmic Events in BRUgada Syndrome) is an international survey on 678 BrS patients who experienced arrhythmic event (AE) including 252 patients in whom AE occurred after prophylactic ICD implantation. Analysis was performed on time-to-first appropriate ICD discharge regarding patients' characteristics. Multivariate logistic regression models were utilized to identify which parameters predicted time to arrhythmia ≤5 years. The median time-to-first appropriate ICD therapy was 24.8 ± 2.8 months. A shorter time was observed in patients from Asian ethnicity (P < 0.05), those with syncope (P = 0.001), and those with Class IIa indication for ICD (P = 0.001). A longer time was associated with a positive family history of sudden cardiac death (P < 0.05). Multivariate Cox regression revealed shorter time-to-ICD therapy in patients with syncope [odds ratio (OR) 1.65, P = 0.001]. In 193 patients (76.6%), therapy was delivered during the first 5 years. Factors associated with this time were syncope (OR 0.36, P = 0.001), spontaneous Type 1 Brugada electrocardiogram (ECG) (OR 0.5, P < 0.05), and Class IIa indication (OR 0.38, P < 0.01) as opposed to Class IIb (OR 2.41, P < 0.01). A near-significant trend for female gender was also noted (OR 0.13, P = 0.052). Two score models for prediction of <5 years to shock were built. First appropriate therapy in BrS patients with prophylactic ICD's occurred during the first 5 years in 76.6% of patients. Syncope and spontaneous Type 1 Brugada ECG correlated with a shorter time to ICD therapy.

Predicting appropriate shocks in patients with heart failure: Patient level meta-analysis from SCD-HeFT and MADIT II.

No precise tools exist to predict appropriate shocks in patients with a primary prevention ICD. We sought to identify characteristics predictive of appropriate shocks in patients with a primary prevention implantable cardioverter defibrillator (ICD). Using patient-level data from the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), we identified patients with any appropriate shock. Clinical and demographic variables were included in a logistic regression model to predict appropriate shocks. There were 1,463 patients randomized to an ICD, and 285 (19%) had ≥1 appropriate shock over a median follow-up of 2.59 years. Compared with patients without appropriate ICD shocks, patients who received any appropriate shock tended to have more severe heart failure. In a multiple logistic regression model, predictors of appropriate shocks included NYHA class (NYHA II vs. I: OR 1.65, 95% CI 1.07-2.55; NYHA III vs. I: OR 1.74, 95% CI 1.10-2.76), lower LVEF (per 1% change) (OR 1.04, 95% CI 1.02-1.06), absence of beta-blocker therapy (OR 1.61, 95% CI 1.23-2.12), and single chamber ICD (OR 1.67, 95% CI 1.13-2.45). In this meta-analysis of patient level data from MADIT-II and SCD-HeFT, higher NYHA class, lower LVEF, no beta-blocker therapy, and single chamber ICD (vs. dual chamber) were significant predictors of appropriate shocks.

Abstract 11595: Predicting Appropriate Shocks In Patients With Heart Failure: Patient Level Meta-analysis From SCD-HeFT and Madit II

Background: Some patients implanted with a primary prevention implantable cardioverter defibrillator (ICD) due to heart failure receive an appropriate shock, but no precise tools exist to predict this outcome. Methods: Using patient level data from the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), we identified patients with any appropriate ICD shock. A variety of clinical and demographic variables were included in a logistic regression model to predict appropriate ICD shocks (Table). Results: There were 1,463 patients randomized to ICD from the two included trials; 285 (19%) had ≥1 appropriate shock over a median follow up of 2.59 years. Compared with patients with no appropriate shocks, patients who received any appropriate ICD shock tended to have NYHA class II or III heart failure symptoms, beta blocker therapy, lower LVEF, wider QRS duration, and a single versus dual chamber ICD (79% of all patients had a single chamber ICD). Other comorbidities were similar between groups. Significant independent predictors of appropriate ICD shocks included NYHA class (NYHA II vs I: OR 1.65, 95% CI 1.07-2.55; NYHA III vs I: OR 1.74, 95% CI 1.10-2.76), LVEF based on one unit change (higher vs lower LVEF: OR 0.96, 95% CI 0.94-0.98), beta blocker therapy (presence vs absence: OR 0.96, 95% CI 0.94-0.98), and single chamber ICD (OR 1.67, 95% CI 1.13-2.45). Conclusion: In this meta-analysis of patient level data from MADIT-II and SCD-HeFT, appropriate ICD shocks were significantly predicted by NYHA class, LVEF, beta blocker therapy, and single chamber ICD. There is a compelling need for a large, prospective study to better define the risk of appropriate ICD shocks in patients meeting criteria for a primary prevention ICD. Until such time, stratification of patients by these factors may better define risk for potentially mortal rhythm events that might be prevented by a primary prevention ICD.

Increased Platelet-to-Lymphocyte Ratios and Low Relative Lymphocyte Counts Predict Appropriate Shocks in Heart Failure Patients with ICDs.

Platelet-to-lymphocyte ratio (PLR) and relative lymphocyte count (L%) are commonly available tests that can be obtained from complete blood count. The aim of this study was to investigate the association between appropriate defibrillator therapy and PLR, and whether decreased lymphocyte count may predict appropriate implantable cardioverter defibrillator (ICD) shocks in heart failure (HF) patients. A total of 147 patients with ischemic or non-ischemic HF who underwent ICD implantation for primary prevention were enrolled in this study. Peripheral venous blood samples were drawn on the same day as ICD implantation. White blood cell counts with differentials, red blood cell indices, and platelet counts were calculated with an automated blood cell counter. All patients were evaluated according to the presence of appropriate ICD therapy. Baseline ejection fraction was significantly lower in the appropriate shock received group (p = 0.040). Median PLR was significantly higher and L% was significantly lower in the appropriate shock received group (p < 0.001). In both ischemic and non-ischemic HF groups, median L% was significantly lower in the appropriate shock received group (p < 0.001; p = 0.006, respectively). In multivariable logistic regression analysis, only L% showed a strong association with appropriate shock therapy (p < 0.001). Higher PLRs are related to appropriate shocks in patients that received ICD with lower EF. Furthermore, decreased L% is independently associated with appropriate shocks in HF.

Retracted: T-peak to T-end Interval Predicts Appropriate Shocks in Patients with Heart Failure Undergoing Implantable Cardioverter Defibrillator Implantation for Primary Prophylaxis.

T-wave peak to T-wave end interval (Tp-e) correlates with dispersion of ventricular repolarization. The purpose of this study was to assess the ability of Tp-e to predict appropriate implantable cardioverter defibrillator (ICD) shocks and all-cause mortality in patients who underwent ICD implantation for primary prophylaxis. Two hundred twenty-eight patients with left ventricular ejection fraction ≤35% and an ICD implanted were followed-up prospectively. Patients divided into two subgroups according to presence of appropriate ICD shocks (Group 1: 112 patients with ICD shocks, Group 2: 116 patients without shocks). End points were appropriate ICD therapy due to ventricular tachycardia (VT)/ventricular fibrillation (VF), death, and a combined end point of VT/VF or death. During a mean follow-up of 22.3 ± 7.7 months, appropriate ICD shocks were observed in 112 of 228 patients (49.1%). The mean duration of the Tp-e Group 1 was significantly longer than Group 2 (115.3 ± 22.2 vs 104.7 ± 20.2 ms, P < 0.001). Ischemic etiology and Tp-e duration were found to be independent predictors of ICD therapy. When the patients were divided into two groups based on Tp-e interval, there was no significant difference regarding the mortality between groups (21.2% vs 21.8%, P: 0.186). However, appropriate ICD shocks due to VT/VF (37.5% vs 58.8%, P < 0.001) and combined end point (39.4% vs 64.5%, P: 0.002) were significantly higher in patients with longer Tp-e group. Tp-e interval independently predicts appropriate ICD shocks in patients with systolic dysfunction and ICDs implanted for primary prevention.

PP-167 The Relation between Digoxin and Appropriate Shocks in Patients with Ischemic Heart Failure and Implantable Cardioverter Defibrillator

PP-167 The Relation between Digoxin and Appropriate Shocks in Patients with Ischemic Heart Failure and Implantable Cardioverter Defibrillator

Outcomes in pacemaker-dependent patients upgraded from conventional pacemakers to cardiac resynchronization therapy-defibrillators

Pacemaker-dependent patients with left ventricular dysfunction benefit from upgrade to cardiac resynchronization therapy (CRT). Those at low risk for ventricular tachyarrhythmias may benefit similarly from upgrade to a CRT-defibrillator or CRT-pacemaker. To determine whether coronary artery disease (CAD), because of associated scar that supports reentry, predicts higher risk of appropriate shocks in pacemaker-dependent patients upgraded to a CRT-defibrillator. We grouped 157 pacemaker-dependent patients with left ventricular ejection fraction (LVEF) ≤35%, no prior sustained ventricular arrhythmias, and conventional pacemakers upgraded to CRT-defibrillators according to the presence (n = 75) or absence (n = 82) of significant CAD. Overall survival, risk of appropriate shocks and antitachycardia pacing, complications related to high-power system components, and LVEF and end-systolic volume changes were contrasted between groups. Patients with CAD had more comorbidities and exhibited increased mortality during a follow-up of 59 ± 30 months (hazard ratio 2.55; 95% confidence interval 1.49-4.36; P = .001). Of 12 patients with appropriate shocks, 11 had CAD. Time to first shock, antitachycardia pacing, and tachyarrhythmia therapy were significantly shorter in patients with CAD (P < .01). The risk of an appropriate shock in patients without CAD was 1 per 362 person-years compared with 1 shock per 26 person-years in patients with CAD. Complications specific to high-energy device components necessitated another procedure in 32 (20%) patients. LVEF improvement and end-systolic volume reduction were similar between groups. Among pacemaker-dependent patients with no prior ventricular arrhythmias upgraded from a pacemaker to a CRT-defibrillator, patients without significant CAD have fewer comorbidities, longer survival, and low risk of appropriate shocks than do patients with CAD. CRT-pacemakers may be appropriate in such patients without CAD.

Upper Limit of Vulnerability at Defibrillator Implantation Predicts the Occurrence of Shocks

Background and Purpose: The utility of upper limit of vulnerability (ULV) testing in patients undergoing defibrillator implantation has been reported. The purpose of this study was to evaluate the difference of outcome between patients with ULV 15 J. Methods: A total of 94 consecutive patients were underwent ICD or CRT-D implantation from February 2009 to December 2010. ULV test has performed in 74 patients, which were retrospectively reviewed. At implantation, we delivered 15 J shock on the peak of T-wave three times to ensure that the most vulnerable part of the cardiac cycle is scanned. If VF was not induced, it meant ULV 15 J (n=14) and we delivered 20 J shock subsequently. When defibrillation was failed, defibrillation threshold was examined closely as much as possible. Results: Patient characteristics between two groups were comparable. After mean follow-up of 393±196 days, the proportion of appropriate shocks in the two groups was 0% vs 21% (p=0.003). There was no case of failed appropriate shocks and death in both groups. Conclusion: ULV can be applied to a safety-margin strategy without inducing VF, and also, is the predictor of the occurrence of appropriate shock in patients with ICD.

Impact of Moderate to Severe Renal Impairment on Mortality and Appropriate Shocks in Patients with Implantable Cardioverter Defibrillators

Background. Due to underrepresentation of patients with chronic kidney disease (CKD) in large Implantable-Cardioverter Defibrillator (ICD) clinical trials, the impact of ICD remains uncertain in this population. Methods. Consecutive patients who received ICD at Creighton university medical center between years 2000–2004 were included in a retrospective cohort after excluding those on maintenance dialysis. Based on baseline Glomerular filtration rate (GFR), patients were classified as severe CKD: GFR < 30 mL/min; moderate CKD: GFR: 30–59 mL/min; and mild or no CKD: GFR ≥ 60 mL/min. The impact of GFR on appropriate shocks and survival was assessed using Kaplan-Meier method and Generalized Linear Models (GLM) with log-link function. Results. There were 509 patients with a mean follow-up of 3.0 + 1.3 years. Mortality risk was inversely proportional to the estimated GFR: 2 fold higher risk with GFR between 30–59 mL/min and 5 fold higher risk with GFR < 30 mL/min. One hundred and seventy-seven patients received appropriate shock(s); appropriate shock-free survival was lower in patients with severe CKD (GFR < 30) compared to mild or no CKD group (2.8 versus 4.2 yrs). Conclusion. Even moderate renal dysfunction increases all cause mortality in CKD patients with ICD. Severe but not moderate CKD is an independent predictor for time to first appropriate shock.

Desmosome Mutations in Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is not a common disease, but it is a deadly one. A detailed understanding of its pathogenesis could provide insights into fundamental mechanisms pertinent to much more common cardiac conditions associated with sudden death. There are several reasons why this might be so. First, ARVC is the most arrhythmogenic form of heart disease in humans. The rate of appropriate shocks in patients with ARVC and implantable defibrillators far exceeds that rate in patients with other highly arrhythmogenic diseases such as long-QT syndrome or hypertrophic cardiomyopathy (data from the North American ARVC registry). Second, arrhythmias are a cardinal feature of ARVC and typically appear early in the disease before significant structural remodeling of the myocardium and contractile dysfunction develop.1 In this sense, ARVC may be as much akin to the ion channelopathies (arrhythmias in a structurally normal heart) as to other types of cardiomyopathies associated with sudden death, such as idiopathic dilated cardiomyopathy or hypertrophic cardiomyopathy in which arrhythmias typically develop in hearts with considerable structural and functional derangements. This does not mean that fibrofatty replacement of the right ventricle plays no role in sudden death. Tissue remodeling in ARVC undoubtedly contributes to arrhythmia substrates, but there is also something about the “unaffected” myocardium that seems to make this such an arrhythmogenic disease. Third, ARVC is a familial disease, usually inherited in an autosomal dominant pattern.2 However, genetic penetrance and disease expression are highly variable. It is not unusual for individuals who carry the same disease-causing mutation to have markedly different clinical manifestations. Even within families, a proband may die suddenly at a young age, whereas first-degree relatives with the same mutation can have a far more benign course.1,2 Knowing the monogenic causes certainly focuses attention on specific genes and provides an entry …

Is gender a risk factor for mortality or appropriate shock in patients with nonischemic cardiomyopathy who have implantable cardioverter defibrillators?

Background: As heart disease is increasingly recognized in women and as important studies have elucidated the benefit of implantable cardioverter defibrillators (ICDs) in patients with nonischemic cardiomyopathy (NICM), little is known regarding the effect of gender difference on arrhythmic risk in this population. We sought to determine if there are gender differences in arrhythmic risk and potential defibrillator benefit in patients with NICM.

Circadian variation of sustained ventricular tachyarrhythmias terminated by appropriate shocks in patients with an implantable cardioverter defibrillator

To determine the circadian variation of sustained ventricular tachyarrhythmias, 78 consecutive patients with an implanted cardioverter defibrillator were analyzed with regard to the occurrence of spontaneous shock episodes during a mean follow-up period of 18 ± 12 months. In 39 patients 207 shock episodes that terminated potentially life-threatening ventricular tachyarrhythmias could be related to an exact time of onset. A circadian variation ( p < 0.001) of these events was demonstrated, with a primary morning peak between 7 hours and 11 hours and a secondary, much smaller peak between 16 hours and 20 hours. This finding indicates the relevance of endogeneous or exogeneous triggers in the cause of malignant arrhythmias that potentially lead to sudden cardiac death. Subgroup analyses revealed an association of the circadian pattern to the New York Heart Association functional classification, indicating perhaps a different role of triggers in different patient populations.