Direct measurements of intramyocardial pressure in dogs suggest that coronary flow cessation at 15 mm Hg is not attributable to diastolic intramyocardial pressure.
This comment was prompted by the article, "Characterization of the Extravascular Component of Coronary Resistance by Instantaneous Pressure-Flow Relationships in the Dog" We have conducted similar investigations of the coronary pressure-flow relationships, including direct measurements of intramyocardial pressure (Heineman et al., 1979) and critical closing pressure (Sherman et al., 1980). While our observations agree with those of Panerai et al., in particular that coronary blood flow ceases at diastolic perfusion pressure of approximately 15 mm Hg, our measurements of IMP do not support their conclusion that this flow cessation phenomenon is attributable to diastolic intramyocardial pressure. We have found diastolic IMP to be 2.7 2.2 mm Hg (mean SD, n = 15) at all depths in the myocardial wall, whereas the systolic IMP is a function of the depth from the epicardial surface.
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Grayson et al. (1980) studied this question.
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