Abstract 16262: Effects of Cardiac Resynchronization Therapy on QRS and JTc Duration in MADIT-CRT
Background: The MADIT-CRT showed that reduction of heart failure events or death by cardiac resynchronization therapy (CRT) was found in LBBB patients, but not in RBBB and IVCD patients. This study aimed to evaluate effects of CRT on QRS and repolarization duration by QRS morphology and determine whether postimplant changes in studied ECG parameters are predictive of clinical and echocardiographic outcome.
Methods: Baseline and one day post-implant digital ECG recordings were available in 817 patients treated with CRT-D. The CRT-induced changes in the following ECG parameters: QRS duration and JTc duration were evaluated regarding their prognostic value for predicting HF events or death and predicting lack of echocardiographic response to CRT measured by lack of reduction of LVESV by at least 15% evaluated at 12 months.
Results: There were 587 patients with LBBB, 99 with RBBB, and 131 with IVCD with pre- and post-implant ECGs. In post-implant ECG, QRS significantly decreased on average by 13 ms in LBBB patients and by 12 ms in RBBB patients whereas there was significant increase in QRS duration by 5 ms in IVCD patients. JTc increased on average by 31ms in LBBB patients, by 21 ms in RBBB patients, and by 18 ms in IVCD patients. QRS and JTc duration was not useful in identifying CRT benefit in non-LBBB patients. In LBBB patients, lower post-implant QRS shortening (expressed per 10ms change) was associated with significant increase of HF event or death (HR=1.17; p=0.021) and with lack of echocardiographic response to CRT (OR=1.26; p=0.005). In the same models, JTc duration <=343 ms in post-implant ECG was associated with increased risk of HF event or death (HR=2.18; p=0.012) and lack of echocardiographic response to CRT (OR=2.71; p=0.009).
Conclusions: CRT was associated with significant shortening of QRS duration in LBBB patients and RBBB patients whereas it prolongs QRS in IVCD patients. Repolarization duration measured by QTc or JTc was significantly more prolonged in LBBB patients than in RBBB and IVCD patients. Lower CRT-induced QRS shortening and less prolonged CRT-induced JTc duration identified patients who did not benefit from CRT therapy. CRT-induced QRS shortening and JTc lengthening might be useful in identifying patients benefiting from CRT.
- © 2010 by American Heart Association, Inc.