Left ventricular coronary blood flow is significantly lower during systole than during diastole. The primary reason for this phasic variation is:
- A Compression of intramural coronary vessels by the contracting myocardium ✓
- B Sympathetic vasoconstriction of coronary arterioles
- C Decreased aortic root pressure during systole
- D Increased oxygen extraction by the myocardium
Correct answer: A. Compression of intramural coronary vessels by the contracting myocardium
Explanation
Contraction of the left ventricle physically compresses the intramural coronary vessels, impeding flow. Aortic pressure remains high during systole, ruling out option C. Sympathetic stimulation causes coronary vasodilation due to increased metabolic demand, ruling out option B.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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