Cardiac Resynchronization Therapy and Proarrhythmia: Weathering the Storm

Abstract

Despite clear benefits of cardiac resynchronization therapy (CRT) on mortality and morbidity in randomized controlled trials among select patients with systolic dysfunction and severe congestive heart failure (CHF), 1,2 there have been numerous case reports over the past 5 years describing significant ventricular proarrhythmia, which manifests primarily as ventricular tachycardia (VT) storm, encountered usually within hours to days after initiation of biventricular pacing. 3-10 At first, the association appeared to be most significant for polymorphic VT, 3,5 but, subsequently, a predominance of monomorphic VT among patients with ischemic cardiomyopathy has been reported. 4,6,7,9 In almost all cases, cessation of biventricular pacing completely suppressed VT and attempts to resume left ventricular pacing resulted in VT recurrence.The report by Nayak et al. 11 in this issue of the Journal represents the largest reported series of VT storm occurring after initiation of CRT and advances our understanding regarding the clinical characteristics and management of this rare but serious adverse outcome. Within this single referral center, 8 out of 191 patients (4%) developed recurrent episodes of sustained monomorphic VT in temporal proximity to initiation of biventricular pacing. A similar percentage of patients developed this complication in a smaller series from another center as well (5 of 145 patients; 3.4%). 6 In contrast to prior reports, half of the patients in the present series developed VT storm more than a week after initiating CRT. This delayed time course raises the possibility that additional intervening precipitants, such as worsening myocardial dysfunction and CHF, may account for at least part of the observed temporal association. Four of these patients experienced cessation of VT when left ventricular (LV) pacing was turned off, suggesting that LV pacing was indeed playing a role in the initiation of VT in these patients. For the other cases where LV pacing was continued throughout, the evidence that LV pacing was the trigger for the VT storm is less clear.There are several reported mechanisms by which epicardial LV pacing may alter the myocardial substrate and promote ventricular arrhythmias. First, epicardial LV pac-

Right ventricular lead proarrhythmia: A novel intervention for an under-recognized phenomenon

“…Theories of proarrhythmia due to CRT devices center around effects of LV pacing. Among its numerous effects, LV pacing reverses the normal activation wavefront pattern to epicardium to endocardium, and it also has the potential of pacing into scar, which may enter critical isthmuses, leading to sustained VT. 4 , 5 , 8 Additionally, canine experiments have demonstrated that transmural dispersion of repolarization increases when pacing occurs from the epicardium vs the endocardium. 9 In humans, biventricular and LV epicardial pacing have been shown to prolong the QT interval and enhance transmural dispersion of repolarization compared to RV endocardial pacing.…”

Electrical Storm in a Patient with Dilated Cardiomyopathy Suppressed with Cardiac Resynchronization Therapy

“…Nevertheless the effect of biventricular pacing on arrhythmia events has not been as clear cut. There are a number of reports suggesting that CRT can cause arrhythmia or even induction of electrical storm after the implantation of biventricular pacing [1]. This has been attributed to the altered ventricular activation sequence and the prolongation of ventricular repolarization phase induced by the LV pacing [1].…”

“…There are a number of reports suggesting that CRT can cause arrhythmia or even induction of electrical storm after the implantation of biventricular pacing [1]. This has been attributed to the altered ventricular activation sequence and the prolongation of ventricular repolarization phase induced by the LV pacing [1]. This is of particular concern in cases when CRT device implantation is not associated with a defibrillator backup.…”

“…A worrying incidence of proarrhythmic effect in the form of electrical storm (ES) after the institution of cardiac resynchronization therapy (CRT) has been repeatedly reported in the recent past [1]. However there are contradictory reports related to either the proarrhythmic [1] or the antiarrhythmic [2,3] potential of the CRT as far as the induction or/and suppression of ES. In line with these reports, we present a case of ES in a patient with dilated cardiomyopathy not responding to triple antiarrhythmic drug therapy, including sedation and intubation, but successfully suppressed after biventricular pacing.…”

Electrical storm after cardiac resynchronization therapy in a patient with nonischemic cardiomyopathy: Signal‐averaged vector‐projected 187‐channel electrocardiogram‐based risk stratification for lethal arrhythmia

“…Proarrhythmic events after CRT have been reported in 5–10% of CRT recipients [1–4]. Gasparini et al investigated the incidence of electrical storm in patients with heart failure treated with CRT and reported an increased incidence in patients with nonischemic cardiomyopathy in whom a CRT‐D was implanted for secondary prevention [5].…”