Measurements of coronary velocity and reactive hyperemia in the coronary circulation of humans.

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Abstract
An acceptable method for measuring phasic coronary velocity and reactive hyperemia in humans is not available. A Doppler probe was developed which can be coupled to surface coronary vessels 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 showed that the probe does not alter myocardial perfusion or cause tissue damage. 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 the following: although reactive hypermia responses were demonstrable following 1-2-s coronary occlusions, maximal responses usually occurred with 20-s coronary occlusions; following 20 s 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 s. These studies provide the 1st quantitative measurements of coronary reactive hyperemia in humans.