Does transient occlusion of the coronary sinus alter the coronary pressure-flow relation in open-chest anesthetized dogs?
Elevation of coronary venous pressure increases zero-flow pressure without altering the slope of the coronary pressure-flow relation, challenging the vascular waterfall mechanism in the coronary circulation.
We studied the effect of transient occlusion of the coronary sinus on the relationship between aortic pressure and circumflex coronary blood flow in open-chest anesthetized dog preparations during artificially prolonged diastoles. The coronary pressure-flow relation was linear, and flow stopped at an arterial pressure (Pf = 0) that always exceeded coronary venous pressure (Pcv). During reactive hyperemia, Pf = 0 was 31 mmHg when Pcv was 5 mmHg and increased to 52 mmHg when the coronary sinus was occluded (Pcv, 38 mmHg). Elevation of Pcv translated the coronary pressure-flow relation to a higher Pf = 0 without altering the slope of the relation. Pf = 0 increased by about two-thirds of the increase in Pcv. We found no evidence that there existed a level of Pcv below which changes in Pcv had no effect on the coronary pressure-flow relation. These data are not compatible with the existence of a vascular waterfall mechanism in the coronary circulation unless it is assumed that Pcv is one of the determinants of Pf = 0.
Bellamy et al. (Tue,) studied this question.
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