Correction of Right Ventricular Pacing Induced Reduction in Coronary Flow by Left and Biventricular Pacing

Patients with right ventricular (RV) pacing may develop left ventricular (LV) systolic dysfunction conventionally attributed to altered electrical activation of the myocardium. Pacing of LV usually corrects LV dysfunction resulting from RV pacing. Most of the patients with RV pacing are elderly and frequently suffer from coronary artery disease. Aim: Compare RV and LV pacing effects on coronary artery flow. Methods: Twenty five patients with heart failure, reduced LV systolic function, wide QRS and left bundle branch block reduced who were treated with cardiac resynchronization pacing therapy (CRT) were studied. All had complete transthoracic Doppler echocardiographic studies. All patients had Doppler sampling of blood velocities in the left anterior descending coronary artery (LAD) during spontaneous rhythm, RV pacing, LV pacing, simultaneous biventricular (BV) pacing, and BV pacing with 30msec delay. Results: LAD diastolic blood velocity was higher, 40.4 ± 12.56, during spontaneous rhythm compared to RV pacing, 37.8 ± 12.56, p=0.0031. LV compared to RV pacing was associated with higher LAD diastolic velocities (43.7±13.72 vs 37.8±13.71cm/sec, p<0.0001), and time velocity integrals (15.47±5.35 vs 12.78±4.94cm, p<0.0001). Compared to RV pacing, BV pacing with and without delay increased significantly LAD diastolic velocity (41.83±12.18 and 46.0±15.98cm/sec respectively, p<0.0008) and time velocity integral (14.34±3.67 and 15.9±6.32, p<0.03). Conclusions: Both LV and BV pacing correct the reduction in coronary artery flow associated with RV pacing and spontaneous left bundle branch. Possibly, reduction in coronary artery flow during RV pacing may contribute to LV systolic dysfunction.