title: Effects of cardiac contraction on segmental coronary resistances and collateral perfusion.
abstract: This study examined the reactions of coronary arteries and microvessels to changes in left ventricular pressure, as well as their significance for collateral circulation. Collateral perfusion pressure was measured as peripheral coronary pressure of an occluded coronary artery after embolisation of its terminal vascular bed with 20 micron microspheres in 9 anesthetized dogs. With measurement of collateral perfusion pressure it was then possible to determine the segmental coronary resistances of the coronary arteries and the microvasculature. Left ventricular pressure was increased by aortic clamping during autoregulation and after maximal pharmacological dilation of the coronary circulation. During autoregulation, the increase in left ventricular pressure induced a resistance decrease mainly in the postcollateral microvessels. With maximal vasodilation, the increase in left ventricular pressure induced a resistance increase mainly in the postcollateral microvessels. Finally with ventricular fibrillation, the resistance of the postcollateral microvasculature was markedly decreased. We conclude that both metabolic regulation of coronary blood flow and extravascular compression of coronary circulation by cardiac contraction act predominantly on postcollateral microvessels. Coronary collateral circulation may be impaired at increased left ventricular pressure.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002866:Chromonar / Q000494:pharmacology; D003097:Collateral Circulation / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000502:physiology; D004176:Dipyridamole / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000503:physiopathology; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014693:Ventricular Fibrillation / Q000503:physiopathology
chemical_list: D004176:Dipyridamole; D002866:Chromonar