Biventricular Pacing Improves Left Ventricular Isovolumetric Relaxation and Compliance More Excellently Than LV Pacing Alone

Introduction: There are few reports that evaluated the effectiveness of cardiac resynchronization therapy (CRT) for left ventricular (LV) diastolic function by an invasive method. We aimed to clarify the hemodynamic improvement brought by CRT, especially throughout diastole. Methods: Twenty-seven patients who underwent CRT were enrolled. We measured 4 LV hemodynamic parameters; +dP/dtmax, −dP/dtmax, tau and LV end-diastolic pressure (LVEDP), using a manometer-tipped catheter. During the measurements, each patient was paced at the same heart rate in 4 different pacing modes; AAI (atrial pacing), DDDRV (right ventricular pacing), DDDLV (LV pacing), DDDBV (biventricular pacing). We compared the parameters in DDDBV with those in the other pacing modes, using repeated measures ANOVA. Results: In DDDBV, both +dP/dtmax and −dP/dtmax were significantly higher, and both tau and LVEDP were prominently lower than those in AAI. The systolic improvement (+dP/dtmax) in DDDLV (1132±275 mmHg/s) was similar to that in DDDBV (1142±270 mmHg/s). Surprisingly, the improvement of LV relaxation (−dP/dtmax, tau) and LV compliance (LVEDP) in DDDBV was superior to those in DDDLV (1117±290 mmHg/s vs 1036±282 mmHg/s; p=0.0189, 51.4±12.8 ms vs 57.0±16.3 ms; p=0.0014, 11.5±8.4 mmHg vs 13.7±8.9 mmHg; p=0.0027, respectively). Conclusions: Biventricular pacing improved both LV relaxation and compliance better than single-LV pacing, probably due to favorable interaction of biventricular contraction and LV elastic recoil.