1: Pacing Clin Electrophysiol. 2008
Jun;31(6):714-21.
Anh D, Srivatsa U, Bui HM, Vasconcellos S, Narayan SM.
University of California and VA Medical Center,
San Diego, California 92161, USA.
BACKGROUND: The impact of altered ventricular activation, including
biventricular (BV) pacing, on T-wave alternans (TWA) and arrhythmic substrates
is unclear. We studied how differing ventricular activation sequence alters
TWA; the interval from peak-to-end of the T-wave (TpTe) and T-wave amplitude
during right (RV), left (LV), and biventricular (BV) pacing; and right atrial
(RA) pacing in patients with preexisting conduction delay. METHODS AND RESULTS:
We measured TWA during RA, RV, LV, and BV pacing in 33 patients receiving
cardiac-resynchronization-therapy-defibrillators. TWA magnitude (V(alt)) was
lower during BV than RV (P < 0.01), RA (P < 0.01), or LV pacing. As a
result, BV-TWA was more often negative than RV-TWA (P < 0.01), LV-TWA, and
RA-TWA, particularly when discordant between pacing modes (P < 0.01). Overall,
83% of TWA recordings were abnormal (25% indeterminate), and 17% negative. BV
pacing reduced T-wave amplitude (P < 0.05) and TpTe (P < 0.005) compared
to RV pacing and LV pacing (P < 0.05; P < 0.005 respectively). Notably,
TWA magnitude varied linearly with T-wave amplitude for all pacing modes (P
< 0.001). Over 410 +/- 252 days' follow-up, RV-TWA predicted the combined
endpoint of death and ICD therapy with 86% negative predictive value (P <
0.05). BV-TWA, RA-TWA, and other repolarization indices were not predictive. CONCLUSIONS:
BV pacing attenuates TWA in tandem with reduced T-wave magnitude. In these
patients with baseline QRS prolongation, RV-TWA predicted events more
effectively than BV-TWA and RA-TWA. Further studies are required to understand
how altered ventricular activation influences repolarization dynamics and
arrhythmic tendency.
PMID: 18507544 [PubMed
- in process]