Abstract 2304: T-Wave Alternans during Cardiac Resynchronization Therapy
Background: Cardiac resynchronized therapy (CRT) involving right ventricular endocardial and left ventricular epicardial pacing improves cardiac output, quality of life, and functional class in patients with congestive heart failure and wide QRS complex. Although a great deal of attention has been directed at showing the mechanical benefits, little attention has been focused on the consequences of reversing the direction of activation of the left ventricular wall. Reversal of the normal activation sequence prolongs the QT interval and increases the existing transmural dispersion of repolarization, creating a substrate and trigger for reentrant arrhythmias. However, controversy exists on the incidence of ventricular tachyarrhythmias in patients with CRT. Presence of microvolt T wave alternans (TWA) has been shown to be independently predictive of ventricular arrhythmic events.
Purpose: The aim of this study was to evaluate the effects of various modes of atrial and ventricular pacing on TWA.
Methods: TWA was measured during right atrial (RA) pacing, right ventricular (RV) endocardial pacing, left ventricular epicardial pacing, and biventricular (BV) pacing at incremental pacing every 5 minutes ranging from 70 to 120 beats/min in 15 patients with permanent BV pacing (mean left ventricular ejection fraction: 32±5%). Positive criteria for TWA was:
alternans voltage (V alt)> 1.9μV and
alternans ratio (AR) >3.0μV for at least one minute using spectral method using CH2000 system (Cambridge Heart, Inc).
Results: Mean V alt (μV) during RA, BV, RV and LV pacing were 2.4±0.5, 2.8±0.3, 1.4±0.5 and 1.5±0.6 (p<0.01 between BV vs. RV). Mean AR during RA, BV, RV and LV pacing were 12.5±3.7, 16.4±6.5, 5.3±1.8 and 7.3±2.1. Positive TWA was observed in 57%, 73%, 50% and 60% during RA, BV, RV and LV pacing.
Conclusion: BV pacing may exaggerate the heterogeneity of ventricular repolarization as measured by an increase of TWA, thus CRT may lead to the development of ventricular tachyarrhythmias and suggests the need for CRT associated with a defibrillation system, especially in patients with positive TWA.