Coronary blood flow is maximum during?

ANSWER: (D) I so volumetric relaxationREF: Ganongs 22nd ed page 621CORONARY BLOOD FLOW:Coronary blood flow, like blood flow in other vessels, is dependent on a pressure gradient, principally driven by mean arterial pressure. However, because aortic pressure can vary widely and because the heart beats continuously, the pressure gradient and, hence coronary blood flow fluctuate depending on the state of contraction. During systole, especially on the left side of the heart, the pressure within the coronary artery secondary to extravascular compression from the squeezing effect of the contracting myocardium virtually eliminates antegrade coronary blood flow. The coronary blood flow" goes to zero just prior to ventricular ejection, corresponding to isovolumic contraction and increased extravascular compression. Conversely, coronary blood flow through the left side is maximal during blood flow through the right side, however, is maximal during peak systole, because developed pressure and consequently extravascular compression within the RV are considerably less than in the LV, thus allowing for antegrade flow during both systole and diastole