Electrical storm in patients with transvenous implantable cardioverter-defibrillators: incidence, management and prognostic implications.

OBJECTIVES: The purpose of this study was to determine the precise incidence, therapeutic options and prognostic implications of electrical storm in patients with transvenous implantable cardioverter-defibrillator (ICD) systems. BACKGROUND: Approximately 50% to 70% of patients treated with an ICD receive appropriate device-based therapy within the first 2 years. Most arrhythmic events require only one appropriate ICD firing for termination. However, some patients receive multiple appropriate shocks during a short period of time, a condition referred to as "arrhythmic or electrical storm." METHODS: This prospectively designed observational study comprised 136 recipients of transvenous ICDs who were followed for 403+/-242 days. Electrical storm was defined as ventricular tachycardia or fibrillation resulting in device intervention > or = 3 times during a single 24-h period. RESULTS: During follow-up, 57/136 patients (42%) received appropriate ICD therapy. Electrical storm occurred in 14/136 patients (10%) at an average of 133+/-135 days after ICD implantation. The mean number of arrhythmic episodes constituting electrical storm was 17+/-17 (range: 3 to 50; median 8) per patient. In 12 patients, electrical storm required hospital admission. The arrhythmia cluster could be terminated by a combined therapy with beta-blockers and intravenous amiodarone whereas class I antiarrhythmic drugs were only occasionally successful. The cumulative probability of survival as estimated by the Kaplan-Meier method showed that patients with an episode of electrical storm did not have a worse outcome compared to those without such an event. CONCLUSIONS: Electrical storm represents a frequent event in patients treated with modern ICDs. It occurs most commonly late after ICD implantation and can be managed by combined therapy with beta-blockers and amiodarone. Electrical storm does not independently confer increased mortality.

Assessment of QT dispersion for prediction of mortality or arrhythmic events after myocardial infarction: results of a prospective, long-term follow-up study.

BACKGROUND: Risk stratification by means of analysis of QT dispersion (QTD) in the 12-lead surface ECG is under intense investigation in various patient populations. The aim of the present prospective study was to evaluate the prognostic value of QTD and other ECG variables reflecting dispersion of ventricular repolarization in comparison with established risk stratifiers during long-term follow-up in a large cohort of post-myocardial infarction patients treated according to contemporary therapeutic guidelines. METHODS AND RESULTS: In 280 consecutive infarct survivors, the 12-lead ECG was optically scanned and digitized for analysis of QTD (QTmax-QTmin) and 25 other repolarization variables, including recently developed and validated parameters such as the T peak-to-T end interval and the area under the T wave. In addition, a variety of established risk stratifiers were assessed. After a mean follow-up period of 32+/-10 months, 30 patients reached one of the prospectively defined study end points (death, ventricular tachycardia, or resuscitated ventricular fibrillation). Comparisons between event and nonevent patients by means of Kaplan-Meier event probability analyses revealed that none of the ECG dispersion variables were of discriminative value. In contrast, variables such as left ventricular ejection fraction (P=0.007), mean 24-hour heart rate (P=0.022), or heart rate variability (P=0.007) proved to be potentially useful risk stratifiers in this patient population. On multivariate analysis, only LVEF, heart rate variability, and a history of thrombolysis were independent predictors of outcome. CONCLUSIONS: Determination of QTD from the surface ECG even when performed with the best available methodology failed to predict subsequent risk in this large series of infarct survivors.

Changes in autonomic tone following thrombolytic therapy for acute myocardial infarction: assessment by analysis of heart rate variability.

INTRODUCTION: Little data are available on changes in autonomic tone during the first 24 hours of acute infarction in patients undergoing thrombolytic therapy. Particularly, the association of changes in autonomic tone to reperfusion of the infarct-related artery has not been evaluated in man. Heart rate variability (HRV) is a noninvasive tool to assess cardiac autonomic tone, which carries prognostic information in postinfarction patients. METHODS AND RESULTS: To assess changes in autonomic tone with angiographically assessed success of thrombolysis in patients with acute infarction, the proportion of adjacent RR intervals different by greater than 50 msec (pNN50) was analyzed from 24-hour Holter monitoring initiated before the start of thrombolytic therapy in 103 consecutive patients. Mean heart rate (HR) and pNN50 were available in 95 of 103 patients and were separately analyzed for the first hour after initiation of thrombolysis (reperfusion phase) and the first 24 hours. As assessed by coronary angiography 90 minutes after start of thrombolysis, 74 patients (78%) had successful coronary artery reperfusion. HR averaged 72 +/- 13/min for the first hour in all 95 patients and 74 +/- 13/min for the first 24 hours. The respective values for pNN50 were 11.2% +/- 11.7% for the first hour and 9.7% +/- 9.2% for the first 24 hours. Patients with inferior myocardial infarction (MI) had a lower mean HR of 72 +/- 12/min versus 76 +/- 13/min (P = 0.11) and a higher pNN50 (11.2% +/- 9.8% versus 7.6% +/- 8.3%, P = 0.01) compared to patients with anterior MI. The mean HR correlated weakly with pNN50 (r = -0.33, P < 0.01). For patients with coronary artery patency after 90 minutes, mean HR was 70 +/- 12/min for the first hour compared to 80 +/- 13/min for patients without (P = 0.003). For the first 24 hours, these values were 72 +/- 12/min compared to 80 +/- 14/min (P = 0.02). For the first hour, pNN50 averaged 12.6% +/- 12.4% for patients with successful reperfusion compared to 6.6% +/- 7.3% for patients without (P = 0.024). For the first 24 hours, these values were 9.2% +/- 8.5% compared to 11.5% +/- 11.3% (P = NS). Patients with in-hospital ventricular fibrillation (n = 8) had a higher mean HR throughout the first 24 hours (88 +/- 16/min vs 73 +/- 12/min, P = 0.008) compared to patients with an uneventful course. Additionally, there was a trend toward a lower HRV in patients with ventricular fibrillation. CONCLUSION: Thrombolysis-induced reperfusion of the infarct-related artery results in a higher vagal tone during the early hours of MI as compared to failed reperfusion. This finding is independent from infarct location and associated with a trend toward a lower incidence of ventricular fibrillation during the acute phase of infarction.

Efficacy and safety of sotalol in patients with complex ventricular arrhythmias.

Sotalol is a unique beta-blocker that prolongs repolarization. Its use in 626 patients with complex ventricular ectopic activity, as reported in the literature, resulted in suppression of arrhythmia in 50 to 60% of treatment attempts. Detailed analysis of data on arrhythmias in 356 patients that were entered prospectively into a database revealed a median reduction in ventricular premature beats of 76%, compared to a median suppression of repetitive ventricular ectopic activity of 91% and of episodes of nonsustained ventricular tachycardia of 97% (p = 0.002 vs reduction of ventricular premature beats). This marked antiarrhythmic potency of sotalol in repetitive ventricular arrhythmias is thought to be due to its class III activity. Drug efficacy was independent of age, sex, the presence or absence of organic heart disease and the degree of sotalol-induced prolongation of corrected QT interval. Evaluation of left ventricular function in 215 patients treated with the drug demonstrated that depression of left ventricular ejection fraction occurred far less frequently than expected with conventional beta-blockers. Even patients with severely depressed pump function tolerated sotalol surprisingly well. There is a propensity of the drug to aggravate arrhythmia, which resulted in serious proarrhythmic events in 30 (3.5%) of 853 patients. These often consisted of torsades de pointes (9 of 30 patients). Proarrhythmia occurred primarily within the first 3 days of dosing, and exhibited a dose-dependence. In conclusion, sotalol is an effective and well-tolerated antiarrhythmic drug in patients with complex ventricular ectopic activity.(ABSTRACT TRUNCATED AT 250 WORDS)