The effect of an increase in heart rate on remote myocardial blood flow in a two vessel coronary stenosis-occlusion model.
The effect of a moderate increase in heart rate on regional blood flow (8-10 mu radiolabeled microspheres) to myocardium supplied by a stenosed left circumflex coronary artery with (n = 11) or without (n = 7) concomitant left anterior descending coronary artery occlusion was investigated in anesthetized mongrel dogs. In the presence of a left circumflex coronary artery stenosis (gradient 32 +/- 5 mmHg [x +/- SEM]) and an unstenosed left anterior descending coronary artery a pacing-induced rise in heart rate (22 +/- 1 beats/min) increased epicardial flow to the posterior wall supplied by the left circumflex coronary artery (+0.21 +/- 0.08 mL/min/g, p = 0.03). Posterior bed endocardial flow was unchanged (-0.03 +/- 0.08 mL/min/g, p = 0.76). In dogs with a left circumflex coronary artery stenosis of similar severity (gradient 34 +/- 4 mmHg), left anterior descending coronary occlusion did not significantly alter posterior bed endocardial or epicardial flow. Atrial pacing increased heart rate by 22 +/- 1 beats per minute and caused remote posterior bed endocardial flow to fall (-0.08 +/- 0.03 mL/min/g, p = 0.03). Epicardial flow to that region rose (+0.09 +/- 0.02 mL/min/g, p less than 0.0002). Thus, a moderately severe coronary stenosis prevents the expected increase in endocardial flow normally seen after an increase in heart rate. Remote bed endocardial flow actually falls when heart rate is increased in the presence of an occlusion in a second major coronary artery.
D000818:Animals; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D006339:Heart Rate