Acute effects of initiation and withdrawal of cardiac resynchronization therapy on papillary muscle dyssynchrony and mitral regurgitation.

OBJECTIVES The purpose of this study was to evaluate the relationship between dyssynchrony involving the mitral valve apparatus and the acute improvement in mitral regurgitation (MR) after cardiac resynchronization therapy (CRT). The effect of interruption of CRT at 6 months' follow-up on dyssynchrony and MR was also evaluated. BACKGROUND Mitral regurgitation may improve acutely after CRT, but the precise mechanism is not fully understood. METHODS Out of 63 consecutive patients with baseline MR, 25 patients showed an acute reduction in MR severity immediately after CRT. This selected group of 25 patients (age 68 +/- 10 years, left ventricular ejection fraction 23 +/- 8%) was evaluated in the current study. Echocardiography including speckle tracking strain analysis was performed at baseline, after CRT initiation, and during interruption of CRT at 6 months' follow-up to study the relationship between dyssynchrony between the papillary muscles and severity of MR. RESULTS According to the inclusion criteria, all patients showed an immediate improvement in MR after CRT (vena contracta width decreased from 0.54 +/- 0.15 cm to 0.39 +/- 0.13 cm; p < 0.001), accompanied by an improvement in mitral deformation indexes. Furthermore, dyssynchrony between the papillary muscles decreased from 169 +/- 69 ms to 25 +/- 26 ms (p < 0.001). Importantly, these beneficial effects were maintained at 6 months' follow-up, but acute loss of resynchronization (from 26 +/- 28 ms to 134 +/- 51 ms; p < 0.001) was observed after interruption of CRT, with an acute recurrence of MR and worsening in mitral deformation indexes. CONCLUSIONS Cardiac resynchronization therapy can acutely reduce MR in patients with dyssynchrony involving the papillary muscles; interruption of CRT at 6 months' follow-up, however, resulted in acute loss of resynchronization with recurrence of MR.