Association Between Left Ventricular Ejection Fraction Post-Cardiac Resynchronization Treatment and Subsequent Implantable Cardioverter Defibrillator Therapy for Sustained Ventricular Tachyarrhythmias

Positive response to cardiac resynchronization therapy reduces arrhythmic events after elective generator change in patients with primary prevention CRT-D

INTRODUCTION

Cardiac resynchronization therapy (CRT) and implantable cardioverter-defibrillators (ICD) are effective therapies for heart failure (HF) patients with cardiac dyssynchrony. Patients receiving primary prevention CRT-defibrillator that positively remodel might no longer qualify for ICD indication due to CRT-induced left ventricular ejection fraction (LVEF) improvement. We aimed to evaluate the outcome of CRT-D patients at the time of device replacement (DR).

METHODS AND RESULTS

Patients undergoing primary prevention CRT-D DR were prospectively included from November 2007 to March 2011 in 2 centers. CRT response was as defined as ≥1 NYHA class improvement and an increase in LVEF ≥10%. Before DR, all patients underwent echocardiography and device interrogation. Patients without theoretical ongoing ICD indication (TOII) at DR were defined as those with LVEF ≥40% without appropriate ICD therapy (appropriate therapy) during the first ICD service-life. A total of 107 consecutive patients were enrolled. Sixty-one patients (57%) were considered CRT responders after the index procedure. At the time of DR (56.4 ± 14.4 months from initial implant), 87% of CRT responders were free of appropriate therapy, compared with 70% of CRT nonresponders (P = 0.02). Thirty-nine patients (37%) did not meet the criteria for TOII. During follow-up (mean 26.4 ± 14.4 months after DR), 37 patients (95%) without TOII were free of appropriate therapy versus 49 of 68 patients (72%) with ongoing TOII (P = 0.007). By multivariable analysis, the only independent predictor of appropriate therapy after DR was TOII (hazard ratio = 6.43; P = 0.01).

CONCLUSION

Absence of theoretical ICD indication occurs in more than one-third of CRT-D patients undergoing DR. In addition, appropriate therapy rate is relatively low (2.2% per year) in this subgroup of patients.

Appropriateness of primary prevention implantable cardioverter-defibrillators at the time of generator replacement: are indications still met?

OBJECTIVES

This study sought to determine how often patients with primary prevention implantable cardioverter-defibrillators (ICDs) meet guideline-derived indications at the time of generator replacement.

BACKGROUND

Professional societies have developed guideline criteria for the appropriate implantation of an ICD for the primary prevention of sudden cardiac death. It is unknown whether patients continue to meet criteria when their devices need replacement for battery depletion.

METHODS

We performed a retrospective chart review of patients undergoing replacement of primary prevention ICDs at 2 tertiary Veterans Affairs Medical Centers. Indications for continued ICD therapy at the time of generator replacement included a left ventricular ejection fraction (LVEF) ≤35% or receipt of appropriate device therapy.

RESULTS

In our cohort of 231 patients, 59 (26%) no longer met guideline-driven indications for an ICD at the time of generator replacement. An additional 79 patients (34%) had not received any appropriate ICD therapies and had not undergone reassessment of their LVEF. Patients with an initial LVEF of 30% to 35% were less likely to meet indications for ICD therapy at the time of replacement (odds ratio: 0.52; 95% confidence interval: 0.30 to 0.88; p = 0.01). Patients without ICD indications subsequently received appropriate ICD therapies at a significantly lower rate than patients with indications (2.8% vs. 10.7% annually, p < 0.001). If ICD generator explantations were performed instead of replacements in the patients without ICD indications, the cost savings would be $1.6 million.

CONCLUSIONS

Approximately 25% of patients who receive primary prevention ICDs may no longer meet guideline indications for ICD use at the time of generator replacement, and these patients receive subsequent ICD therapies at a significantly lower rate.

Ventricular arrhythmias in super-responders to cardiac resynchronization therapy

INTRODUCTION AND OBJECTIVES

Cardiac resynchronization therapy is associated with improved quality of life and reduced morbidity and mortality in patients with severe ventricular dysfunction and wide QRS. However, its role in the reduction of ventricular arrhythmias is more controversial.

METHODS

We compared the incidence of ventricular arrhythmias in patients who were undergoing cardiac resynchronization therapy with an implantable cardioverter-defibrillator in terms of the degree of echocardiographic response to resynchronization. Patients were classified in 3 subgroups;super-responders, responders, and nonresponders.

RESULTS

We included 196 patients who were followed up for a median 30.1 months [interquartile range, 18.0-55.1 months]. We recorded the presence of ventricular arrhythmias in 37 patients (18.8%); 3 patients (5.9%) in the super-responder group had ventricular arrhythmias vs 14 (22.2%) among the responders and 20 (24.4%) in the group of nonresponders (P = .025). In multivariate analysis, the only independent predictors of the appearance of ventricular arrhythmias were secondary-prevention device implantation (odds ratio = 4.04; 95% confidence interval, 1.52-10.75; P=.005), absence of echocardiographic super-response (odds ratio=3.81; 95% confidence interval, 1.04-13.93; P=043), QRS >160 ms (odds ratio=2.39; 95% confidence interval, 1.00-1.35; P=.049) and treatment with amiodarone (odds ratio=2.47; 95% confidence interval, 1.03-5.91; P=.041).

CONCLUSIONS

The patients classified as super-responders to cardiac resynchronization therapy had a significant reduction in incidence of ventricular arrhythmias by comparison with the other patients. Despite this, arrhythmic episodes do not completely disappear in this subgroup.