Pathophysiology and Natural History Coronary Blood Flow

We have previously shown that dogs with renal hypertension and left ventricular hypertrophy have larger infarcts (per risk area size) than do control animals. A potential explanation for this is that collateral resistance is higher in these dogs. Paradoxically, previous postmortem studies in human hearts with left ventricular hypertrophy have suggested that coronary collaterals are actually increased in this condition. To test the hypothesis that left ventricular hypertrophy is associated with alterations in coronary collateral resistance, studies were performed in dogs with renal hypertension and left ventricular hypertrophy and in patients with aortic valvular disease at the time of cardiac surgery. With an isolated, adenosine-vasodilated, blood-perfused cardiac preparation, collateral and normal zone pressure-flow relationships were established by means of radioactive microspheres in nine dogs with renal hypertension and left ventricular hypertrophy and in 17 controls. Collateral resistance calculated from these pressure-flow relationships were similar in both groups (4.0 --0.7 in dogs with renal hypertension and left ventricular hypertrophy and 3.9 0.4 mm Hg/ml/min/ 100 g in controls). In addition, normal zone resistance was not different between groups (transmural resistances 0. 17 + 0.01 in controls and 0. 18 ± 0.02 in dogs with renal hypertension and left ventricular hypertrophy. In five patients with aortic valve disease, left ventricular hypertrophy, and normal coronary arteries and in six patients without left ventricular hypertrophy who had normal left anterior descending coronary arteries, a 7 MHz suction-mounted echo transducer was used to monitor systolic wall thickening during transient occlusions of the left anterior descending artery at the time of cardiac surgery. Because noncollateralized myocardium ceases to contract promptly after coronary occlusion, this approach provides an indirect index of collateral perfusion. Twenty seconds after the onset of coronary occlusion, systolic thickening had markedly decreased in both groups (15 + 10% of control values in nonhypertrophied hearts and 10 ± 10% in hearts with left ventricular hypertrophy; p = NS between groups). Thus the severity of contraction abnormality induced during transient coronary occlusion in these two groups of patients was similar, suggesting that the degree of severity of ischemia was comparable between the two groups. We conclude that collateral resistance is not altered by hypertension and left ventricular hypertrophy and that left ventricular hypertrophy in patients is not associated with functional evidence of an enhanced collateral circulation. Taken together, these results support the concept that the functional capacity of the coronary collateral hypertrophy. Circulation 71, No. 6, 1135-1145, 1985. CARDIAC HYPERTROPHY is associated with numerous alterations of the coronary circulation. Minimal coronary resistance assessed by a variety of techniques is abnormally elevated in several animal preparations of cardiac hypertrophy. '-1 Capillary denFrom the Departments of Internal Medicine and Cardiothoracic Surgery and the Cardiovascular Center, The University of Iowa College of Medicine, and the Veterans Administration Hospital, Iowa City. Supported by American Heart Association Grant-in-Aid 831069, NIH grants HL27633 and HL20827, PPG grant HL14388, and the Ischemic SCOR HL32295. Dr. Harrison is the recipient of the NHLBI Clinical Investigator Award (1K08HL01046-01). Address for correspondence: David G. Harrison, M.D., E317A General Hospital, University of Iowa, Iowa City, IA 52242. Received Nov. 23, 1984; revision accepted March 15, 1985. Vol. 71, No. 6, June 1985 circulation is not augmented by left ventricular sity has been found to be diminished and oxygen diffusion distance increased by pressure-induced left and right ventricular hypertrophy.44` Thus it is not surprising that patients with aortic stenosis frequently develop angina-like chest pain during exercise even though their coronary arteries are angiographically