EFFECT OF VENTRICULAR PACING ON CORONARY BLOOD-FLOW IN PATIENTS WITH NORMAL CORONARY-ARTERIES

Although ventricular pacing is thought to produce impairment of left v entricular function by altering the sequence of ventricular activation and AV dyssynchrony, little is known about the effect of ventricular pacing on coronary blood flow. We measured coronary blood flow and cor onary flow reserve in the left anterior descending coronary artery dur ing sinus rhythm, and during both atrial and ventricular pacing at a r ate of 100 ppm in 14 patients with normal coronary arteries. The doubl e product increased significantly during both types of pacing. Coronar y arterial diameter during ventricular pacing significantly increased compared to that during both sinus rhythm and atrial pacing. Coronary flow velocity during ventricular pacing was significantly lower compar ed to that during both sinus rhythm and atrial pacing. Coronary blood flow increased significantly during atrial pacing (30.7% +/- 12.1%; P < 0.001), but not significantly during ventricular pacing (23.6% +/- 4 7.0%; P = ns). While coronary flow reserve during both atrial (3.9 +/- 1.3) and ventricular pacing (3.8 +/- 0.9) was lower compared to its v alue during sinus rhythm (4.5 +/- 1.5), the difference was not signifi cant. There was a significant positive correlation between the coronar y flow reserve during sinus rhythm and the increase of coronary blood flow during ventricular pacing (R-2 = 0.78; P < 0.001). We concluded t hat an increase in coronary blood flow during ventricular pacing is no t a common finding regardless of the increase in metabolic demand. The increase of coronary blood flow during ventricular pacing was less in patients with a reduced coronary flow reserve. These findings suggest that preservation of AV synchrony and the presence of a normal sequen ce of ventricular activation may play an important role in preserving coronary blood flow in this subset of patients.