Effects of systole-specific pericardial pressure increases on coronary flow.
It has been postulated that intrathoracic pressure increases may impair cardiac function by decreasing coronary flow. To determine whether altered coronary flow causes or results from change in cardiac function, we used 14 anesthetized dogs in propranolol-induced heart failure following atrioventricular node ablation. After thoracoabdominal binding, the animals were paced and ventilated at the same frequency, and inspiration was synchronized with cardiac systole, resulting in systole-specific pericardial pressure increases (SSPPI). At SSPPI magnitudes of 15 and 30 mmHg, left atrial transmural pressure decreased and cardiac output increased, whereas decreases in left ventricular end-systolic transmural pressure and myocardial O2 consumption were directly related. Concurrent decreases in coronary sinus flow (CSF) and coronary arteriovenous O2 gradient with SSPPI 15 mmHg indicate autoregulation. However, the arteriovenous O2 gradient remained unaltered with SSPPI 30 mmHg, despite further decrease in CSF. Because the absolute diastolic aortic pressure decreased, a limit may exist for increasing SSPPI above which CSF may be directly affected.
Department of Physiology, University of South Carolina School of Medicine, Columbia 29201.
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Hassapoyannes
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Harper
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Stuck
C A
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Hornung
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Abel
D000818:Animals; D001049:Apnea / Q000503:physiopathology; D001283:Atrioventricular Node / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology*; D004285:Dogs; D006321:Heart / Q000187:drug effects; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D013599:Systole; D014655:Vascular Resistance / Q000502:physiology
D011433:Propranolol