Abstract 1605: Impact Of Cardiac Resynchroniztion Therapy On Patients With Right Ventricular Pacing-induced Left Bundle Branch Block.
The impact of cardiac resynchronization therapy (CRT) on patients with right ventricular (RV) pacing-induced left bundle branch block (LBBB) is less established. The purpose of the study is to compare the pattern of left ventricular (LV) mechanical dyssynchrony (LVMD) between patients with intrinsic and RV pacing-induced LBBB; and to evaluate the impact of CRT on these two groups.
Methods: We studied 95 consecutive patients with CRT (male 76, female 19, age 70.1± 9.5 years). Patients consisted of 67 patients with intrinsic LBBB (Group I) and 28 patients with RV pacing-induced LBBB (Group II). Patients with complete right bundle branch block were excluded. The time difference (TPW-TDI) between QRS onset to the end of LV ejection by pulsed wave Doppler and QRS onset to the end of the systolic wave in basal segment with greatest delay by tissue Doppler imaging was measured before CRT and at the last follow-up after CRT. TPW-TDI > 50ms was defined as LVMD. Positive response to CRT was defined as left ventricular end systolic volume decreasing ≥15% after CRT.
Results: The percentage of CRT responders in Group II were significantly greater than Group I (68% vs 42%, p=0.04) during follow-up of 15.5± 11.1 months. After adjusting by age, gender and clinical features, this pattern of CRT responses persisted (p= 0.003). There was greater reduction of the QRS duration in Group II after CRT (177.6± 28.4ms vs 154.1± 39.5ms, p= 0.01). However, there were no significant difference in TPW-TDI between two groups neither at baseline (p= 0.63) or in the end of follow-up (p=0.72). There was no significant difference in mortality (15% vs 14%, p= 1.0) and Kaplan-Meier plot survival (p=0.80) between two groups during follow-up of 17.3± 10.8 months.
Conclusions: Patients with heart failure and RV pacing-induced LBBB have at least the same or better response rate to CRT than patients with intrinsic LBBB. The change of LVMD after CRT was similar in these two groups of patients.