Does reception of appropriate shocks from the implantable cardioverter defibrillator affect survival?

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.

Mechanisms of syncope in implantable cardioverter-defibrillator recipients who receive device therapies

A significant proportion of implantable cardioverter defibrillator (ICD) recipients ultimately receive device therapies. Determinants and mechanisms of syncopal events in these patients are not established. To address this issue, we reviewed prospectively collected data on 114 ICD recipients who received device therapies. There were 99 men and 15 women with a mean age of 63+/-10 years. Ejection fraction was 29+/-13%. At initial presentation, 74 patients (65%) had syncope during arrhythmia. Of 114 patients, 18 patients (16%) subsequently experienced syncope during device therapies over a period of 35+/-24 months of follow-up. Arrhythmias during syncopal events documented by telemetry, event recorders, RR intervals, or ICD stored electrograms were obtainable in 13 patients, and included sustained monomorphic ventricular tachycardia (VT) in 10 patients, ventricular fibrillation (VF) in 2 patients, and atrial fibrillation in 1 patient. The explanations for arrhythmia-related syncope included ICD proarrhythmia in 8 patients (62%), rapid monomorphic VT in 3 (23%), and VF in 2 patients (15%). Patients with syncope could not be differentiated from those without syncope by demographic, clinical, or electrophysiologic variables. There was no significant difference in mortality between patients with or without syncope (39% vs 25%, p = 0.25). Syncope is not uncommon in ICD recipients who receive device therapies. When it occurs, syncope is often due to ICD proarrhythmia; hence, it is potentially preventable by meticulous device programming.

Incidence and clinical significance of multiple consecutive, appropriate, high-energy discharges in patients with implanted cardioverter-defibrillators

BACKGROUND

Some patients with an automatic implantable cardioverter-defibrillator (ICD) suffer multiple appropriate, consecutive, high-energy discharges (MCDs) during follow-up. Such events might represent resistant ventricular arrhythmias and might have prognostic significance.

METHODS AND RESULTS

Eighty consecutive patients with an ICD were followed up for up to 82 months (mean, 21 +/- 19 months). Thirty-eight patients had survived an out-of-hospital cardiac arrest and 42 had recurrent ventricular tachycardia. During follow-up, 16 patients had MCD (group A), 26 patients had episodes of single appropriate discharges (group B), and 38 patients had no appropriate discharges (group C). Group A patients had worse functional status (P = .001), lower left ventricular ejection fractions (LVEFs) (P = .001), and lower survival rates (log rank, P = .003) than the remaining two groups of patients. Cox analysis showed LVEF (P = .001) to be an independent predictor of MCD. Independent predictors of death or heart transplant were MCD (P = .001), female sex (P = .001), age (P = .001), history of cardiac arrest (P = .003), and functional status (P = .003). The only independent predictor of total mortality was female sex (P = .002). Independent predictors of cardiac death were MCD (P = .007) and female sex (P = .018). Independent predictors of arrhythmic death were age (P = .001), female sex (P = .02), and MCD (P = .023).

CONCLUSIONS

In patients with an ICD, the development of MCD is an independent predictor of cardiac and arrhythmic mortality. If this finding is confirmed in larger studies, it may help to identify patients in whom other therapeutic alternatives, ie, heart transplantation, should be considered during follow-up after ICD implantation.

Lessons learned from data logging in a multicenter clinical trial using a late-generation implantable cardioverter-defibrillator. The Guardian ATP 4210 Multicenter Investigators Group

OBJECTIVES

This study examined patterns of implantable cardioverter-defibrillator use as documented by data logging.

BACKGROUND

Implantable cardioverter-defibrillators are accepted therapy for malignant ventricular tachyarrhythmias; however, relatively little is known about their patterns of use. Incorporation of data-storage capacities into these devices provides insight into long-term defibrillator function.

METHODS

Stored data-logging information was retrieved from 401 implanted cardioverter-defibrillators in 393 patients over an average of 303 days of follow-up.

RESULTS

A total of 91,443 detections were recorded in 299 patients. One hundred-six patients (26%) had detections due to supraventricular tachycardias, electrical noise or other causes, resulting in inappropriate therapy delivery to 92 patients (23%). Two hundred eighty-one patients recorded 66,276 episodes of ventricular tachycardia or ventricular fibrillation. Of these, 74.4% episodes terminated spontaneously without any delivered therapy, 22.1% terminated after antitachycardia pacing, and 1.7% terminated after shock therapy. Antitachycardia pacing was activated without formal testing in 47% of all patients receiving this therapy and was successful in 96% of all episodes receiving this therapy. Acceleration of tachycardia to shock therapy occurred in 1.3% of all episodes and in 30.5% of patients receiving antitachycardia pacing. Thirty-four patients (8.7%) died during follow-up. Mortality was associated with patient age, heart failure functional class at implantation and frequency of shocks received during follow-up (all p < or = 0.05).

CONCLUSIONS

Most ventricular tachyarrhythmia detections by this noncommitted implantable cardioverter-defibrillator resolve spontaneously, whereas the majority receiving therapy can be treated with antitachycardia pacing. Mortality after implantable cardioverter-defibrillator implantation is associated with age, heart failure class and frequency of shocks received during follow-up. Data-logging capabilities provide valuable insights into the patterns of defibrillator use.

Implantable cardioverter-defibrillator therapy in 300 patients with coronary artery disease presenting exclusively with ventricular fibrillation

To determine outcomes of implantable cardioverter-defibrillator (ICD) therapy in a uniform population of survivors of sudden cardiac death, we used epicardial defibrillation lead systems to study 300 patients with coronary artery disease (CAD) presenting exclusively with ventricular fibrillation (VF) unassociated with acute myocardial infarction. Operative (30-day) mortality, 2.7% overall, was lower (0.6%) in patients with ejection fractions (EF) > or = 0.30. Over a median follow-up of 1.9 years, cumulative actuarial shock incidence was similar in patients who underwent concomitant coronary artery bypass graft (CABG) surgery (38%) and in those who did not. The 2-year cumulative actuarial incidences of any or appropriate shocks were 65% and 38%, respectively. Sudden death survival at 2 years was 92.5% and 99.3% for patients with EFs < or = 0.30 and > 0.30, respectively. The total mortality rate was similar in shocked and in unshocked patients. Multivariate analysis identified EF and female gender as significant predictors of any and appropriate shock occurrence (all p values < or = 0.05) and EF as a significant predictor of sudden, cardiac, and total mortality (all p values < 0.03). We conclude that in CAD patients presenting exclusively with VF unassociated with acute myocardial infarction and treated with thoracotomy-requiring ICD therapy: (1) operative (30-day) mortality is minimal for patients with an EF > or = 0.30; (2) device use is high and sudden death rates low regardless of concomitant CABG; (3) low EF is a significant predictor of cumulative shock occurrence and mortality (sudden, cardiac, and total); (4) female gender may be a predictor of shock occurrence; and (5) similar mortalities and low sudden-death rates in shocked and nonshocked ICD patients imply that ICD therapy improves survival in shocked patients to a level observed in comparable patients in whom ventricular tachyarrhythmia does not recur.

Interventional electrophysiology--state-of-the-art 1993

The field of clinical electrophysiology has broadened significantly in the last several years, spawning a new discipline known as Interventional or Therapeutic Electrophysiology. In the United States, Electrophysiology has its own training path and accreditation requirements. One of the reasons for the growth of interest in electrophysiology is the exciting introduction of nonpharmacologic methods of arrhythmia therapy, including curative radiofrequency catheter ablation and implanted devices for antitachycardia pacing/defibrillation. The arrhythmia specialist now has at his/her disposal a wide range of options for patients with symptomatic or life-threatening cardiac arrhythmias.

Symptoms and electrocardiographically documented rhythm preceding spontaneous shocks in patients with implantable cardioverter-defibrillator

During a follow-up of 24 +/- 20 months after treatment with an implantable cardioverter-defibrillator (ICD), 101 of 241 patients (42%) received > or = 1 spontaneous ICD shocks with documentation of the rhythm leading to shock by Holter or telemetry monitoring or stored electrograms by the device. Sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) was documented in 67 of the 101 patients (66%) with electrocardiographically documented shocks, nonsustained VT in 4 patients (4%), supraventricular tachyarrhythmias in 41 patients (41%), and normal sinus or pacemaker rhythm in 10 patients (10%). No, mild (palpitations and/or mild dizziness) and severe symptoms (presyncope/syncope) preceded spontaneous ICD shocks in 20 (30%), 33 (49%) and 27 (42%) of the 67 patients, respectively, with electrocardiographically documented VT or VF, and in 23 (56%), 16 (39%) and 1 (2%) of the 41 patients, respectively, with electrocardiographically documented supraventricular tachyarrhythmias. Three of the 4 patients with nonsustained VT had mild symptoms, and 1 patient with nonsustained VT had presyncope. None of the 10 patients with spurious discharges during normal sinus or pacemaker rhythm had symptoms preceding the ICD shocks. It is concluded that (1) most patients with either electrocardiographically documented VT/VF or a non-VT/VF rhythm preceding spontaneous ICD shocks have no or mild symptoms preceding the shock, and (2) severe symptoms preceding ICD shocks suggest sustained VT or VF as the underlying rhythm, although severe symptoms rarely occur in patients with supraventricular tachyarrhythmias or nonsustained VT.

Shock occurrence and survival in 241 patients with implantable cardioverter-defibrillator therapy

BACKGROUND

The purpose of this study was to determine the influence of clinical characteristics on shock occurrence and survival in 241 patients with implantable cardioverter-defibrillator (ICD) therapy.

METHODS AND RESULTS

Two hundred forty-one consecutive patients underwent ICD implantation between November 1982 and November 1991 and were subsequently followed for 26 +/- 22 months (intention-to-treat analysis). Actuarial incidence of "appropriate" shocks was 13%, 42%, and 63%, and the incidence of any spontaneous shocks was 15%, 51%, and 76% at 1, 3, and 5 years of follow-up, respectively. Poor left ventricular function (ejection fraction < or = 30%) was associated with an earlier occurrence of both appropriate and any spontaneous ICD shocks (p = 0.001). Appropriate and any spontaneous shocks occurred significantly later in patients who presented with cardiac arrest and in patients in whom only ventricular fibrillation but no uniform ventricular tachycardia was induced during preoperative programmed stimulation. In addition, amiodarone treatment at implant was associated with later occurrence of any spontaneous shocks. Cumulative survival from all-cause mortality including perioperative mortality was 84%, 62%, and 57%, and survival from arrhythmic death was 97%, 89%, and 83% at 1, 3, and 5 years, respectively. Ejection fraction < or = 30% was the best predictor of both total arrhythmic death (p = 0.019) and total mortality (p = 0.003). Antiarrhythmic therapy with class 1 agents at implant was also associated with a higher total mortality during follow-up (p = 0.023) but not with total arrhythmic death. Age, sex, underlying heart disease, clinical presentation, and preoperative response to programmed stimulation did not predict long-term survival. In addition, survival curves were similar for patients with and without spontaneous shocks.

CONCLUSIONS

The majority of patients receive shocks during long-term follow-up. The occurrence of appropriate or any spontaneous shocks during follow-up is not associated with increased arrhythmic or total mortality consistent with effective prevention of sudden cardiac death with ICD therapy in this high-risk patient population. Although low ejection fraction is the strongest predictor of both shock occurrence and mortality during follow-up, no easy algorithm can be derived from the analyzed clinical characteristics to predict which patients will benefit most from ICD implantation.