title: Coronary haemodynamics and myocardial metabolism during cardiopulmonary bypass.
abstract: An experimental animal preparation is described which has allowed us to determine coronary haemodynamics and the overall myocardial metabolic rate of the disease-free, beating, normothermic heart during total cardiopulmonary bypass. We have confirmed that under these conditions the required coronary blood flow is about 50ml/min/100g myocardium, which can be achieved at a low perfusion pressure (60 mm Hg or 8 kPa), and that overall myocardial metabolism is represented by an oxygen utilization of just over 2 ml/min/100g. We have also defined the associated dynamic parameters which characterize oxygen transport in the coronary circulation during bypass. By controlling coronary perfusion, analogous in a clinical setting to selective coronary perfusion, we have demonstrated a simple linear correlation between perfusion pressure and coronary flow, indicating a "fixed" coronary vascular resistance. Under these conditions the myocardial oxygen uptake rises towards a maximum of 4ml/min/100g with the expected associated changes in the parameters characterizing oxygen transport in the coronary circulation. These trends are postulated as being a reflection of alterations in regional myocardial perfusion. By extrapolating to the clinical situation, these data have appeared to give valid information concerning the adequacy of coronary perfusion.
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002315:Cardiopulmonary Bypass; D003326:Coronary Circulation; D004285:Dogs; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D010477:Perfusion; D014655:Vascular Resistance