Electrical remodelling in cardiac resynchronization therapy: decrease in intrinsic QRS duration.

INTRODUCTION

Cardiac resynchronization therapy (CRT) provides a therapeutic option for patients with congestive heart failure (CHF) and left bundle-branch block. Structural myocardial remodelling due to CRT has been described extensively. We hypothesized that CRT might also induce electrical remodelling, thus decreasing the intrinsic QRS duration.

METHODS

In 38 patients with CHF (ejection fraction (EF): 26 +/- 7%) a CRT device was implanted. 18 patients suffered from ischaemic cardiomyopathy (ICM) and 20 from dilated cardiomyopathy (DCM). Echocardiography and 12-lead ECGs without pacing were obtained prior to implantation and after 6 and 12 months. Patients were classified as responders in case of an increase in EF > or = 25% in combination with an increase in NYHA class > or = 1. Variance analysis was performed to determine the impact of response or underlying heart disease (ICM/DCM) on the extent of change in QRS duration (delta QRS duration).

RESULTS

The EF increased to 36 +/- 10% (P < 0.0001) after 6 months and 40 +/- 12% (P < 0.0001) after 12 months of CRT. Intrinsic QRS duration decreased from 171 +/- 18 ms before CRT to 164 +/- 23 ms (P = 0.027) after 6 months and 161 +/- 25 ms (P = 0.002) after 12 months of CRT. 22 patients (58%) were classified as responders. Whereas a significant decrease in intrinsic QRS duration was observed in responders, only a slight decrease was seen in non-responders. However, two-factorial variance analyses did not show a significant influence of response or underlying heart disease (ICM/DCM) on delta QRS duration (P = 0.7).

CONCLUSION

CRT results in an electrical remodelling with a reduction of the intrinsic QRS duration.