Effects of heart rate and perfusion pressure on segmental coronary resistances and collateral perfusion
This study examined the responsiveness of coronary arteries and microvessels to changes in heart rate and perfusion pressure. Our purpose was to determine quantitatively the sensitivity of segmental coronary resistances upon these hemodynamic interventions and to study their significance for collateral circulation.
Collateral perfusion pressurePPC was measured as peripheral coronary pressure of an occluded coronary artery after embolisation of its terminal vascular bed with 25 μm microspheres in 7 open chest dogs. With measurement ofPPC it was then possible to determine the segmental coronary resistances of the coronary arteries and the microvasculature.
Atrial pacing up to 220 min−1 decreasedPPC from 54±6 to 45±6 mm Hg (P<0.01); after maximum dilation with carbochromene (3 mg/kg i.v.) and dipyridamole (0.2 mg/kg i.v.) pacing increasedPPC from 34±8 to 39±8 mm Hg (P<0.01).
Elevating coronary perfusion pressure from 53±4 to 107±4 mm Hg induced an increase in the resistance of arteries up to the origin of collaterals by 19% (P<0.01) and in the resistance of the distal microvessels by 34% (P<0.01); after maximum dilation elevating perfusion pressure decreased proximal resistance by 32% (P<0.01) and distal resistance by 60% (P<0.01).
These results demonstrate that collateral circulation depends on collateral perfusion pressure in the donor coronary artery which is subject to metabolic regulation, as well as on the pressure at the orifice of collaterals to the ischemic vasculature which is passively subject to mechanical influences of diastolic duration and perfusion pressure.
Key wordsSegmental coronary resistances Coronary collateral circulation Heart rate Coronary perfusion pressure
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