Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 186

Because of systolic compression of the microcirculation, the LV receives blood mainly during diastole (>80% of the left coronary flow occurs in diastole). Tachycardia, in addition to increasing O₂ demands, reduces myocardial O₂ supply by reducing diastolic time.

As opposed to the LV, the RV is thin and does not compress its microcirculation as much in systole, which explains why its flow is not as affected by systole. Approximately 50% of the right coronary-to-RV flow occurs in systole.

The LV coronary blood flow is directly related to the pressure gradient between DBP and LVEDP (coronary perfusion pressure) and inversely related to the microvascular resistance; the latter depends on myocardial stiffness, and, thus, on LVEDP as well (flow = delta pressure/microvascular resistance). An increase in LVEDP reduces coronary flow, even in the absence of a coronary stenosis.

Since the RV receives significant flow during systole, the coronary blood flow of the RV is partly related to the gradient between SBP and RV systolic pressure, not just DBP and RVEDP.