Predictors of left ventricular function deterioration in patients with left bundle branch block and ejection fraction >50%.

Resynchronization therapy has become standard of care in patients with left bundle branch block (LBBB), congestive heart failure (CHF), and low ejection fraction (EF). In order to characterize the left ventricular (LV) function evolution in patients with LBBB and baseline preserved LVEF, records of all patients who visited an academic echocardiography laboratory during a period of 4 years were retrospectively investigated. Patients were included if they had a baseline EF >50%, LBBB on surface electrocardiography, and at least one follow-up echocardiogram no earlier than 3 months after the baseline study. The endpoint was the occurrence of EF deterioration to values ≤40%. Clinical variables associated with this outcome were identified. Forty-nine patients satisfied the entry criteria. Over a mean 13±8.5 months of follow-up (range 3 to 36), 8 patients (16%) experienced EF deterioration ≤40%. History of CHF prior to baseline echocardiogram and LV mass >300 g were associated with this phenomenon (P=.004 and P=.015, respectively), with a negative predictive value of 100% and 92%, respectively. Our data profiles a risk-stratification methodology in patients with LBBB and baseline EF >50% and possibly a triage strategy toward resynchronization therapy in this population.

Mechanisms of inappropriate defibrillator therapy in a modern cohort of remotely monitored patients.

INTRODUCTION: Defibrillator (ICD) technology and monitoring are evolving rapidly. We investigated the mechanisms of inappropriate ICD therapies in a modern cohort of patients followed at our institution via remote monitoring. METHODS: From September 2009 to March 2011, a total of 2,050 ICD patients (19,600 patient-months) were remotely followed. All events (shocks and antitachycardia pacing) were adjudicated by arrhythmia specialists. RESULTS: A total of 249 patients received ICD therapy (34% inappropriate therapy). Inappropriate ICD shocks affected 33 (1.6%) patients. There were a total of 249 inappropriate episodes in 85 patients. Supraventricular tachycardia (SVT) with 1:1 atrioventricular association was the predominant mechanism accounting for 133 episodes in 50 patients, followed by atrial fibrillation (97 episodes in 27 patients). T-wave oversensing (16 episodes in five patients), electromagnetic interference (two episodes in two patients), and ectopic beats (one episode in one patient) accounted for a small proportion of events. There were 35 arrhythmic episodes in five patients that could not be classified, all in patients with single-chamber devices. There were no differences in these results by device manufacturer. CONCLUSIONS: Despite many technological advances, inappropriate ICD shocks still occur but at very low rates and SVT with 1:1 atrioventricular association represents their most common mechanism.

Accelerated junctional rhythm and nonalternans repolarization lability precede ventricular tachycardia in Casq2-/- mice.

BACKGROUND: Calsequestrin-2 (CASQ2) is a Ca(2+) buffering protein of myocardial sarcoplasmic reticulum. CASQ2 mutations underlie a form of catecholaminergic polymorphic ventricular tachycardia (CPVT). The CPVT phenotype is recapitulated in Casq2 -/- mice. Repolarization lability (RL)-beat-to-beat variability in the T wave morphology-has been reported in long-QT syndrome, but has not been evaluated in CPVT. METHODS AND RESULTS: ECG from Casq2 -/- mice was evaluated with respect to heart rate (HR) and RL changes prior to onset of ventricular tachycardia (VT) to gain insight into arrhythmogenesis in CPVT. Telemetry from unrestrained mice (3-month-old males, 5 animals of each genotype) and ECG before and after isoproterenol administration in anesthetized mice was analyzed. Average HR in sinus rhythm (SR), occurrence of nonsinus rhythm and RL were quantified. HR was slower in Casq2 -/- animals. Accelerated junctional rhythm (JR) occurred more frequently in Casq2 -/- mice and often preceded VT. In Casq2 -/- mice, HR increased prior to VT onset, prior to onset of JR and on transition from JR to VT. RL increased during progression from SR to VT and after isoproterenol administration in Casq2 -/-, but not in Casq2+/+ animals. Isoproterenol did not increase repolarization alternans in either genotype. CONCLUSIONS: Accelerated JR, likely caused by triggered activity in His/Purkinje system, occurs frequently in Casq2 -/- mice. The absence of CASQ2 results in increased RL. The increase in HR and in RL precede onset of arrhythmias in this CPVT model. Nonalternans RL precedes ventricular arrhythmia in wider range of conditions than previously appreciated.

Women and minorities are less likely to receive an implantable cardioverter defibrillator for primary prevention of sudden cardiac death.

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) improve survival in patients with depressed left ventricular ejection fraction (EF). We investigated whether women and minorities are as likely as white men to receive an ICD for primary prevention of sudden cardiac death. METHODS AND RESULTS: We reviewed the electronic medical records of patients with cardiomyopathy by nuclear single-photon emission computed tomography imaging (EF ≤ 35%), who had no prior history of sustained ventricular arrhythmias. Clinical and demographic data were collected and the Charlson comorbidity index (CCI) was calculated for each patient. A total of 233 non-selected patients (age = 68 ± 12 years, 29% women, 21% black, EF 24 ± 6%, CCI 6.62 ± 2.9) were included in this analysis of whom 111 (48%) received an ICD. In univariate analysis, ICD recipients were more likely to be Caucasian men compared with black men or women from all races. After adjusting for race, gender, EF, and the CCI in a multivariate logistic regression model, women were 61% less likely than men [odds ratio (OR) = 0.39, 95% confidence interval (CI) 0.20-0.74, P= 0.004] and blacks were 72% less likely than whites (OR = 0.28, 95% CI 0.13-0.59, P= 0.001) to receive an ICD. CONCLUSIONS: Even after adjusting for comorbid conditions, gender, and racial discrepancies in the implantation of ICDs for the primary prevention of sudden cardiac death exist. Further investigations into the root causes of these discrepancies are needed before any corrective measures can be adopted.

Effectiveness of implantable defibrillators in octogenarians and nonagenarians for primary prevention of sudden cardiac death.

Given their advanced age and frequent co-morbidities, it is unclear whether octogenarians and nonagenarians with decreased left ventricular ejection fraction (LVEF) derive a survival benefit from implantable cardioverter-defibrillators (ICDs) in the primary prevention setting. The purpose of this study was to examine the effect of ICDs, age, and multiple co-morbidities on survival in elderly patients who otherwise meet implantation criteria for primary prevention of sudden cardiac death. Patients ≥80 years of age who received an ICD for LVEF ≤35% at our institution from 2001 through 2008 (n = 99) were compared to a cohort of patients ≥80 years of age with similarly low LVEF who did not receive an ICD (n = 53). Co-morbid conditions were assessed using the Charlson co-morbidity index (CCI). The overall cohort (n = 152, 84 ± 4 years old, 72% men, 87% with ischemic cardiomyopathy, LVEF 25 ± 7%, CCI 5.9 ± 3.2) was followed for 2.3 ± 2.0 years. Patients with ICDs were younger (82 ± 3 vs 86 ± 4 years, p <0.001) and had fewer co-morbidities reflected in a lower CCI (5.3 ± 3.1 vs 6.7 ± 3.1, p = 0.021). Patients with ICDs also had a trend toward lower LVEF (24 ± 6% vs 27 ± 7%, p = 0.06). During follow-up 93 (61%) patients died, 58 (59%) in the ICD group and 35 (66%) in the no-ICD group. ICD recipients had better 1-year survival compared to patients with no ICD (72% vs 52%, p = 0.014). However, after adjusting for age, LVEF, glomerular filtration rate (GFR), and CCI using multivariate Cox models, an ICD did not confer any survival benefit (hazard ratio 0.71, 95% confidence interval 0.42 to 1.20, p = 0.20), whereas age (p = 0.043) and GFR (p = 0.006) were the only independent predictors of survival. In conclusion, age and GFR are the main determinant of survival in octogenarians and nonagenarians with LV dysfunction. After correcting for these parameters, an ICD does not appear to confer a survival benefit.

A novel manoeuvre for discerning supraventricular tachycardia mechanism.

AIMS: Discerning supraventricular tachycardia (SVT) mechanism during catheter ablation procedures can be difficult and time-consuming, which, when combined with diagnostic error, places patients at risk of unnecessary complications. Distinguishing atrial tachycardia (AT) from AV nodal re-entry tachycardia (AVNRT) may be particularly vexatious. Value-added techniques are thus always welcome, particularly if they are not time-consuming nor require complex intracardiac lead configurations. In this study, we assessed whether a new technique, simultaneous right atrial and right ventricular pacing (RA + RV) during ongoing SVT, met these criteria. METHODS AND RESULTS: Using a simple intracardiac lead configuration (right atrial appendage, His bundle, right ventricular apex), the response to RA + RV delivered at 80-90% of the SVT cycle length, was examined in 80 patients referred for catheter ablation. In each patient, the actual tachycardia mechanism was adjudicated by standard electrophysiologic criteria ± successful catheter ablation. Mechanisms of SVT included, non-exclusively, AVNRT (24 patients), accessory pathway-mediated (orthodromic) re-entry (AVRT; 23 patients), AT (10 patients), and sinus tachycardia (ST induced with isoproterenol; 49 patients). Immediately after cessation of RA + RV pacing during persistent SVT, the first intracardiac electrogram observed was right atrial in all AT whereas it was His bundle in all AVNRT. The response during AVRT was mixed. CONCLUSIONS: In this preliminary evaluation, RA + RV pacing appears to add value to the existing armamentarium of electrophysiologic indices to discern SVT mechanism, in particular with respect to discriminating between AVNRT and AT.

Heart failure in women is different than in men; should treatment be different?

Women with heart failure differ from their male counterparts in a number of ways, including etiology, pattern of cardiac remodeling, and prognosis. They may even respond differently to medical therapy. But until prospective, sex-specific studies show that we should do otherwise, we recommend that women with heart failure be treated the same as men, according to established guidelines.