Predicting arrhythmic death: a plea for standardized reporting techniques and data based on continuous electrocardiographic monitoring

Designation and distribution of events in the Multicenter UnSustained Tachycardia Trial (MUSTT)

Patients with coronary artery disease, depressed left ventricular ejection fraction, and nonsustained ventricular tachycardia (VT) have a high mortality rate due to arrhythmic (arrhythmic death/cardiac arrest) and other cardiac causes. The Multicenter UnSustained Tachycardia Trial (MUSTT) investigated whether electrophysiologic study (EPS) was helpful in choosing drug or defibrillator therapy in patients induced into sustained VT. The events committee attempted to categorize follow-up events in patients in MUSTT and to present a detailed breakdown of events. A derivative of the Hinkle-Thaler classification was used, incorporating lessons from other multicenter studies. The committee was blinded to results of EPS and implantable cardioverter-defibrillator (ICD) or other antiarrhythmic therapy status of patients. The primary end point was cardiac arrest or death from arrhythmia. Secondary end points were death from all causes, cardiac causes, and spontaneous sustained VT. Classifications were death and cardiac arrest. Each was similarly divided as arrhythmic with 14 subcategories, e.g., unwitnessed or related to EPS and nonarrhythmic with 10 subcategories, e.g., ischemia. Terminal VF in progressive heart failure was considered nonarrhythmic. Events were reviewed by 2 members. Disagreements were resolved by the 2 members or, if needed, by the full committee. Of the 2,202 patients in MUSTT, there were 902 deaths. Sustained VT requiring cardioversion occurred in 182 patients. An additional 94 patients had resuscitated cardiac arrests. Events occurred in 1,027 patients, and all were reviewed. The 3 leading events were deaths that were classed as sudden/unwitnessed (23% of 902), due to progressive heart failure (22%), or due to noncardiovascular causes (18%). Arrhythmic deaths or cardiac arrests were highest in inducible patients randomized to no antiarrhythmic therapy; next were inducible patients receiving an ICD; and lowest were in patients who were noninducible. In conclusion, the classification system provided a detailed breakdown of events in consistent categories, showing utility for event analysis and interpretation and development of therapeutic strategies. The classifications assigned by the committee were used in all MUSTT outcomes reports, thus affecting all reported outcomes and overall interpretations of the MUSTT.

Determinants of outcome in patients with sustained ventricular tachyarrhythmias: the antiarrhythmics versus implantable defibrillators (AVID) study registry

BACKGROUND

The prognosis of patients with sustained ventricular tachyarrhythmias varies according to clinical characteristics. We sought to identify predictors of survival in a large population of patients with documented sustained ventricular tachyarrhythmias not related to reversible or correctable causes included in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Registry.

METHODS AND RESULTS

We analyzed the impact of 36 demographic, clinical, and discharge treatment variables on the outcome for 3559 patients. Survival status was assessed with the use of the National Death Index. Multivariate analyses were performed with the use of the Cox proportional hazards model. After a mean follow-up of 17 +/- 12 months, 631 patients died. Actuarial survival was 0.86 (95% confidence interval [CI] 0.85 to 0.88), 0.79 (95% CI 0.78 to 0.81), and 0.72 (95% CI 0.70 to 0.74) at 1, 2, and 3 years. Multivariate predictors of worse survival included older age, severe left ventricular dysfunction, lower systolic blood pressure, history of congestive heart failure, diabetes, smoking or atrial fibrillation, and preexistent pacemaker. The hemodynamic impact of the qualifying arrhythmia was not a predictor of outcome. Defibrillator implantation and hospital discharge while the patient was taking a beta-blocker or an angiotensin-converting enzyme inhibitor were associated with better prognosis.

CONCLUSIONS

Despite therapeutic advances, the mortality rates of patients with sustained ventricular tachyarrhythmias remain high. Prognosis depends on the severity of underlying heart disease, as reflected by the extent of left ventricular dysfunction and the presence of heart failure. Well-tolerated ventricular tachycardia in patients with structural heart disease does not carry a significantly better prognosis than ventricular tachyarrhythmia with more severe hemodynamic consequences.

Shocks as predictors of survival in patients with implantable cardioverter-defibrillators

OBJECTIVES

The objective of the study was to determine whether the occurrence of shocks for ventricular tachyarrhythmias during therapy with implantable cardioverter-defibrillators (ICD) is predictive of shortened survival.

BACKGROUND

Ventricular tachyarrhythmias eliciting shocks are often associated with depressed ventricular function, making assessment of shocks as an independent risk factor difficult.

METHODS

Consecutive patients (n = 421) with a mean follow-up of 756+/-523 days were classified into those who had received no shock (n = 262) or either one of two shock types, defined as single (n = 111) or multiple shocks (n = 48) per arrhythmia episode. Endpoints were all-cause and cardiac deaths. A survival analysis using a stepwise proportional hazards model evaluated the influence of two primary variables, shock type and left ventricular ejection fraction (LVEF <35% or >35%). Covariates analyzed were age, gender, NYHA Class, coronary artery disease, myocardial infarction, coronary revascularization, defibrillation threshold and tachyarrhythmia inducibility.

RESULTS

The most complete model retained LVEF (p = 0.005) and age (p = 0.023) for the comparison of any shock versus no shock (p = 0.031). The occurrence of any versus no shock, or of multiple versus single shocks significantly decreased survival at four years, and these differences persisted after adjustment for LVEF. In the LVEF subgroups <35% and <25%, occurrence of multiple versus no shock more than doubled the risk of death. Compared with the most favorable group LVEF > or =35% and no shock, risk in the group multiple shocks and LVEF <35% was increased 16-fold.

CONCLUSIONS

In defibrillator recipients, shocks act as potent predictors of survival independent of several other risk factors, particularly ejection fraction.