2304/C59 - T-Wave Alternans during
Cardiac Resynchronization Therapy |
|
Keywords: |
Pacing,
Heart failure, Electrocardiography, Signal averaging, Pacemaker, artificial |
Disclosure Block: |
K. Hashimoto, None; I. Watanabe, None; S. Ashino, None; M. Kofune, None; Y. Okumura, None; T. Yamada, None; T. Kofune, None; K. Ohkubo, None; A. Shindo, None; H. Sugimura, None; T. Nakai, None; Y. Kasamaki, None; S. Saito, None. |
|
|
Abstract:
|
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: 1)
alternans voltage (V alt)>1.9μV and 2) 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. |