Larger interventricular conduction time enhances mechanical response to resynchronization therapy.

BACKGROUND: Previous studies have reported that the left ventricular (LV) pacing site is a major determinant of the hemodynamic response to cardiac resynchronization therapy (CRT). However, lead positioning in a lateral or posterolateral cardiac vein may not be optimal for every patient. The objective of this study was to assess the relationship between the right ventricular (RV)-to-LV conduction time and the systolic function during CRT on the basis of changes to LV pressure-volume loops. METHODS: Left ventricular pressure and volume data were determined using a conductance catheter during CRT device implantation in 10 patients. Four endocardial LV sites were systematically assessed at four atrioventricular delays. The RV-to-LV conduction time was measured as the time interval between spontaneous peak R waves, recorded through the RV lead and the LV catheter. RESULTS: The optimal pacing site varied among patients. However, the pacing site associated with the maximum RV-to-LV conduction time resulted in a stroke volume improvement comparable to the pacing site identified through individual hemodynamic optimization (41 ± 17 mL vs 44 ± 18 mL, P = 0.266). Moreover, the RV-to-LV conduction time recorded at each endocardial pacing site correlated positively with the increase in stroke volume (r = 0.537; P < 0.001), stroke work (r = 0.642; P < 0.001), and the pressure-derivative maximum (r = 0.646; P < 0.001) obtained with CRT. CONCLUSIONS: An optimal acute response to CRT can be obtained by positioning the LV lead at the site associated with the maximum RV-to-LV conduction time. A significant correlation appears to exist between RV-to-LV conduction time and the improvement in systolic function with CRT.

Incidence of ventricular arrhythmias after biventricular defibrillator replacement: impact on safety of downgrading from CRT-D to CRT-P.

BACKGROUND: Cardiac resynchronization therapy (CRT) reduces mortality and hospitalizations. It is debated whether CRT alone (CRT-P) or CRT plus defibrillator (CRT-D) is preferable, and still guidelines are not exhaustive. The aim of the study was to investigate whether to implant CRT-P or CRT-D in CRT-D patients who did not experience malignant arrhythmias at the moment of replacement. METHODS: Out of 451 heart failure patients undergoing CRT-D according to guidelines, 103 (67±10 years, 80% men) underwent device replacement with CRT-D. Every 6 months patients underwent to clinical evaluation and device interrogation and episodes of ventricular arrhythmias (VA) stored. At baseline and before replacement echocardiogram was performed. Patients were defined responders if left ventricular (LV) end-systolic volume decreased ≥15% and super-responders if LV ejection fraction increased ≥40% or ≥50%. RESULTS: Mean follow-up was 75±24 months after implantation and 26±10 months after replacement. First VAs incidence per year did not decrease over time (P=0.619). Before replacement, 27 patients (26.2%, 15 responders/12 non-responders) experienced VA. After replacement, 8 patients (7.7%, 4 responders/4 non-responders) experienced VA for the first time. Super-responder condition was not associated with lower VA incidence before (0.499) and after (P=0.339) replacement. At multivariate analysis, age was the only independent predictor of electrical appropriate therapy after substitution (ORper year=1.17; 95% CI: 1.03-1.34; P=0.003). CONCLUSIONS: Freedom from VA before device replacement does not correlate with freedom from VA after replacement, so downgrade from CRT-D to CRT-P is not feasible at replacement, in particular in the elderlies, independently of responder and super-responder condition.