Coronary Blood Flow — FRCA Primary MCQ
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Correct answer: E — Diastolic predominance is greater in the left than in the right coronary artery
Left coronary flow has the greater diastolic predominance. During left ventricular systole, contraction generates high intramyocardial pressure and compresses the intramural vessels, particularly in the subendocardium, markedly restricting forward flow. Relaxation reduces this extravascular resistance, allowing flow to increase during diastole. Right ventricular systolic pressure and wall tension are lower, so systolic compression of the right coronary microcirculation is less marked. Right coronary flow is therefore less strongly diastolic than left coronary flow, although contemporary human measurements indicate that it is still usually greater in diastole than systole. Thus A and D reverse or obscure the difference, C is incorrect because systolic flow does not normally cease completely, and E reverses the normal left-coronary pattern.
Reference: Seligman H et al. Phasic flow patterns of right versus left coronary arteries in patients undergoing clinical physiological assessment. EuroIntervention. 2022;17(15):1260-1270. https://pubmed.ncbi.nlm.nih.gov/34338643/