Critical closing and critical XXXX phenomena in the coronary vasculature of the @entity235 .

@entity296 @entity1538 @entity548 @entity63 @entity235 @entity1167
Direct measurements of coronary venous outflow in a right-heart bypass preparation were used to study the critical closing (CC) and critical @entity1538 (CO) phenomena in the anesthetized @entity235 heart. Arterial pressure was lowered rapidly by @entity548 , and CC pressure was the pressure at which coronary flow stopped completely. Shed blood was returned immediately or after 3 min of @entity63 . The pressure at which coronary flow resumed (CO pressure) was measured. Coronary flow stopped at a mean aortic pressure of 14.3 mmHg. Vasodilator drugs and @entity63 lowered CC pressure to 10.5 and 10.2 mmHg, respectively. Aortic pressure of 47.3 mmHg was needed to resume coronary flow following perfusion arrest. A brief period of @entity63 did not significantly change the CO pressure. These results confirm the presence of CC phenomenon in @entity235 heart and show that CC pressure can be altered by @entity63 or vasodilators. It is suggested that the high value of CO pressure may be responsible for @entity296 associated with @entity63 @entity1167 during open-heart surgery.
