When do coronary arteries primarily receive blood flow?
A. During inspiration
B. During diastolic
C. During expiration
D. During systole
Correct Answer: B. During diastolic
Although the coronary arteries may receive a minute portion of blood during systole, most of the blood flow to coronary arteries is supplied during diastole. Breathing patterns are irrelevant to blood flow. The RCA and LMCA extend from the aortic root to supply different regions of the heart. The RCA gives rise to the sinoatrial nodal branch of the right coronary artery, posterior descending artery branch of the RCA, and the marginal branch.
Option A: The RCA supplies blood to the right side of the heart. The sinoatrial nodal branch of the RCA provides blood to the SA node, and the atrioventricular nodal artery delivers blood to the AV node. The marginal branch of the right coronary artery provides blood supply to the lateral portion of the right ventricle. The posterior descending artery branch supplies blood to the inferior aspect of the heart.
Option C: The LMCA supplies blood to the left side of the heart. The LAD provides blood to the anterior ventricular septum and the greater portion of the anterior portion of the left ventricle. The LCx supplies blood to the lateral wall of the left ventricle and sometimes to the posterior inferior aspect of the heart when there is left heart dominance.
Option D: There are numerous normal physiological coronary artery variances. Starting with coronary dominance, the PDA in 70% of patients arises from the right coronary artery (known as right dominance); in about 10% of cases, a branch from the LCx supplies the inferior segment of the heart (known as left dominance). In about 20% of cases, there is dual supply from both the right coronary artery and the LCx (known as codominance).
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