Impact of QRS morphology on heart rate turbulence and heart rate variability after cardiac resynchronization therapy in patients with heart failure.

OBJECTIVE: Impairment of heart rate turbulence (HRT) and heart rate variability (HRV) are associated with poor prognosis in chronic heart failure (CHF). Although previous studies have demonstrated that patients with a left bundle branch block (LBBB) have a better outcome with cardiac resynchronization therapy (CRT), the effect of QRS morphology on HRV and HRT is not known. We aimed to evaluate the effect of QRS morphology on HRV and HRT after CRT implantation in patients with CHF.

PATIENTS AND METHODS: Patients who had been implanted a CRT device with cardioversion-defibrillation feature were included to the study. Forty-three patients with LBBB (group 1) were compared with 21 patients without LBBB (group 2). HRV and HRT parameters were compared before and one month after CRT implantation.

RESULTS: We compared the echocardiographic and electrocardiographic changes in both groups after CRT. Cardiac output (CO) was found to be significantly much more increased in group 1 (1.1 ± 0.4 vs. 0.6 ± 0.4, p = 0.001). Similarly, except SDNN and LF, all HRT and HRV parameters were significantly changed in the patients with LBBB (TO 1.4 ± 0.3 vs. 1.2 ± 0.2, p = 0.001; TS -1.8 ± 0.7 vs. -0.9 ± 0.7, p = 0.001; RMSSD -15.7 ± 9.9 vs. -6.3 ± 6.2, p = 0.001; PNN50 -7.0 ± 4.6 vs. -1.7 ± 1.1, p = 0.001; HF -13.3 ± 6.7 vs. -4.3 ± 3.5, p = 0.001; LF/HF 1.9 ± 0.4 vs. 1.5 ± 0.2, p = 0.001) compared to those without LBBB. Lineer regression analysis showed that the CO (β = 0.2, t = 2.8, p = 0.007) and QRS configuration (β = 0.6, t = 0.5, p = 0.001) were independent parameters affecting TO.

CONCLUSIONS: HRV and HRT are improved after CRT but these improvements are more remarkable in patients with LBBB. CO, QRS configuration (but not duration) were two independent parameters affecting TO, LF and LF/HF ratio after CRT.