| Abstract | 「Control of Coronary Circulation」The coronary circulation is unique among the organ vascular beds in the body because it provides nutrient blood flow to the organ that itself generates the force that produces the flow of blood. Because of this, traditional consideration of the control of the coronary circulation has given maj or attention to the hemodynamic parameters that influence coronary blood flow. However it is cinical to understand that regional myocardial blood flow (RMBF) is neither uniform throughout the myocardium nor constant in any region during the cardiac cycle (Fig.1). For example, in the left ventricle where, normally, pressure is generated that is equal to aortic systolic pressure, only a small fraction of myocardial blood flow occurs during systole when aonic pressure is highest.1) Aortic diastolic pressure is the motivating force for the majority of left ventricular (LV) blood flow. This is because even though the aonic pressure is less during diastole, the coronary perfusion pressure (CPP), which may de defined as difference between aortic pressure and LV intracaritary pressure, is greater during diastole because LV pressure is low. In contrast, the low pressures normally generated by the right ventricle and both atria allow a high CPP gradient even during systole, therefore right ventricular and atrial blood flow occurs throughout the cardiac cycle with little interference due to cardiac contraction. Neither is myocardial blood flow uniformly distributed across the thickness of the LV wall. |
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