Phasic and Mean Blood Flow in the Canine Septal Artery and an Estimate of Systolic Resistance in Deep Myocardial Vessels

• Gregg and Green concluded that phasic patterns of coronary flow recorded from meters placed at the ostia of coronary arteries fail to indicate actual hlood flow within the myocardium except during late systole and late diastole. They interpret the superficial arteries as in essence, elastic volume buffers imposed between flow meters and the myocardium. Three deviations of recorded flow curves from true myocardial flow may be predicted on theoretical grounds. 1. The magnitude of the sharp reversal of flow usually registered in early systole is underestimated because the blood expressed from deep layers of myocardium distends superficial vessels and is not metered. 2. The generally recorded mid-systolic forward flow is too high since the rise in aortic pressure results in further distention of large surface vessels and of vessels in superficial layers of myocardium where systolic extravascular compression is less than in deeper layers. This is recorded, however, as a forward flow through the meter. 3. Finally, the metered forward flow during early diastole is less than the true intramyocardial flow since blood from the distended superficial vessels flows into the relaxing myocardium without being metered. In dogs the septal artery passes almost