Carotid endarterectomy reduced the overall incidence of ipsilateral neurologic events in a selected group of male patients with asymptomatic carotid stenosis. We did not find a significant influence of carotid endarterectomy on the combined incidence of stroke and death, but because of the size of our sample, a modest effect could not be excluded.

To assess visual interpretation of the coronary arteriogram as a means of predicting the physiologic effects of coronary obstructions in human beings, we compared caliper measurements of the degree of coronary stenosis with the reactive hyperemic response of coronary flow velocity studied with a Doppler technique at operation, after 20 seconds of coronary arterial occlusion. In 39 patients (44 vessels) with isolated, discrete coronary lesions varying in severity from 10 to 95 per cent stenosis, measurement of the percentage of stenosis from coronary angiograms was not significantly correlated (r = -0.25) with the reactive hyperemic response. Results were the same for obstructions in the left anterior descending, diagonal, and right coronary arteries. Underestimation of lesion severity occurred in 95 per cent of vessels with greater than 60 per cent stenosis of the diameter by arteriography. Both overestimation and underestimation of lesions with less than 60 per cent stenosis were common. These results, together with the high interobserver and intraobserver variability of standard visual analysis of angiograms, suggest that the physiologic effects of the majority of coronary obstructions cannot be determined accurately by conventional angiographic approaches. The need for improved analytical methods for the physiologic assessment of angiographically detected coronary obstructions is apparent.

An acceptable method for measuring phasic coronary velocity and reactive hyperemia in humans has not been available. We have developed a doppler probe which can be coupled to surface coronary vessel* at the time of cardiac surgery with a small suction cup. Phasic coronary velocity can be measured with a signal to noise ratio that exceeds 20:1. Animal studies have shown that the probe does not alter myocardial perfusion or cause tissue damage. In addition, changes in mean coronary velocity are closely related (r « 0.97) to changes in coronary flow over a wide range (15-400 ml/min). The characteristics of reactive hyperemia in the coronary circulation of dogs determined with the doppler system are similar to those obtained simultaneously with an electromagnetic flow meter. Transient occlusions of branch coronary vessels in patients with normal coronary arteries are not associated with significant changes in heart rate, left atrial, or mean arterial pressure. The characteristics of reactive hyperemia in normal vessels of 13 patients were as follows: although reactive hyperemia responses were demonstrable following 1 to 2-aecond coronary occlusions, maximal responses usually occurred with 20-second coronary occlusions; following 20 seconds of coronary occlusion, the ratio of peak to resting velocity was 5.8 ± 0.6 (mean ± SE); the ratio of repayment to debt area was 3.1 ± 0.2, and the duration of the reactive hyperemia response was 20.8 ± 0.3 seconds. These studies provide the first quantitative measurements of coronary reactive hyperemia in humans. Circ Res 49: [877][878][879][880][881][882][883][884][885][886][887][888][889][890][891] 1981

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The pathogenesis of angina pectoris in patients with aortic stenosis and normal coronary arteries remains uncertain. Using a specially designed Doppler probe, we measured the maximal velocity of coronary blood flow in the left-anterior descending coronary artery at the time of elective open-heart surgery in 14 patients with aortic stenosis and left ventricular hypertrophy (13 had angina) and in 8 controls without left ventricular hypertrophy. The ratio peak velocity of coronary blood flow, after a 20-second occlusion, to resting velocity was decreased by more than 50 per cent (P less than 0.05) in the patients with aortic stenosis. In 7 of the patients this ratio was decreased by more than 75 per cent. Studies of the velocity of coronary blood flow in vessels perfusing the right ventricle in these patients showed only mild abnormalities. These data demonstrate a selective and marked decrease in coronary reserve to the hypertrophied left ventricle in patients with severe aortic stenosis. The impairment in coronary reserve is probably an important contributor to the pathogenesis of angina pectoris in these patients.