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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

We have developed a directional pulsed-Doppler system to make blood flow velocity measurements in the coronary arteries of the rat. The probe consists of a 1-mm2 crystal mounted in a 6-mm suction cup, which can be attached by vacuum to the vessel without requiring dissection. Recordings of phasic coronary blood flow velocity (CBV) in the rat indicate that 82 +/- 2% (mean +/- SE) of the area under the CBV recording occurs in diastole. CBV increased during an infusion of dipyridamole and changed in parallel with alterations in left-ventricular pressure. To validate the technique we correlated changes in CBV wih changes in microsphere-measured left-ventricular perfusion (range, 20--780 ml/min x 100 g). These two methods of estimating coronary flow correlated closely (r = 0.93). Measurements of phasic CBV in the rat with this Doppler system should permit a detailed characterization of the coronary circulation in many models of disease that have been developed in the rat.

Carotid artery shunts are used extensively during carotid artery surgery to maintain cerebral perfusion. Blood flow through such shunts may be compromised by thrombosis, incorrect placement, or inadvertent clamping of the shunt. Currently, however, no direct method exists to detect poor shunt flow that might precipitate cerebral ischemia. A carotid artery shunt system that continuously monitors blood flow rates has been developed. This system utilizes a Doppler crystal embedded in the wall of a silicone elastomer shunt. The crystal ranges through a "liquid lens" that enables it to be placed without violation of the shunt lumen. Because the crystal is at a fixed angle (45 degrees) to the axis of blood flow and the diameter of the lumen remains constant, a linear relationship should exist between flow rates and the Doppler velocity signal. This hypothesis was tested in vitro using a pulsatile pump and both a starch-water solution and whole blood. Doppler velocity meter readings were compared to timed volume collections over a wide range of flow rates. A direct linear relationship between the Doppler flowmeter and timed volume collections existed, and the system was accurate to within 4.7%. This device may be useful in laboratory studies of carotid shunt dynamics and in clinical practice for early detection of correctable shunt flow abnormalities that could lead to cerebral injury.

It is hypothesized that myocardium subjected to a 5 minute period of coronary occlusion and a 30 minute period of reperfusion has latent abnormalities that become overt when the reperfused myocardium is "challenged" by a subsequent coronary occlusion. This hypothesis is clinically relevant because reperfused myocardium is frequently subjected to recurrent ischemia, as in patients with unstable angina, vasospastic angina or recurrent thrombosis after initial coronary occlusion and thrombolysis. In 19 open chest dogs, the response of regional myocardial function to brief coronary occlusions was studied. Systolic wall thickening and diastolic thinning were measured using a specially developed miniature 5 MHz echocardiographic transducer fixed to the epicardium by suction. All 19 dogs underwent an initial "challenge" coronary occlusion (30 seconds). Thereafter, the control group (n = 8) underwent no intervention for 30 minutes, while the intervention group (n = 11) underwent 5 minutes of coronary occlusion followed by 30 minutes of reperfusion. All dogs were then subjected to a second "challenge" coronary occlusion (30 seconds). In the control group, responses to the second challenge occlusion were the same as to the first occlusion. In the intervention group, regional and global systolic function and myocardial perfusion after the 5 minute coronary occlusion intervention returned to baseline levels, but the response to the second challenge coronary occlusion was significantly different in the intervention group.(ABSTRACT TRUNCATED AT 250 WORDS)

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