& x20;Reason for biphasic flow in right coronary artery? - INI-CET EXAM -2026

INI-CET EXAM -2026

Applied Physiology

Medium

Appeared in: INI-CET EXAM -2026

Explanation

The right ventricle (RV) is a low-pressure chamber compared to the high-pressure left ventricle.
During systole, the pressure in the RV does not rise high enough to overcome the aortic pressure that drives blood into the coronary arteries.
Because the driving pressure from the aorta remains higher than the intramyocardial pressure of the RV throughout the cardiac cycle, blood flows into the right coronary artery during both systole and diastole.
This continuous flow during both phases of the cardiac cycle creates a characteristic biphasic flow pattern.

Option A: Increased aortic pressure is the driving force for perfusion in both coronary arteries but does not explain the difference in flow patterns between the right and left sides.
Option B: Increased right ventricular mass (hypertrophy) would increase intramyocardial pressure during systole, which would impede, not facilitate, systolic blood flow, tending to make the flow monophasic.
Option C: This is factually incorrect for a normal heart and is the opposite of the correct reason. High pressure in the right ventricle would compress the RCA and reduce systolic flow.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiology of Coronary Artery Blood Flow as background academic context rather than a clinical decision trigger.
Understanding the biphasic flow to the right ventricle is crucial for interpreting coronary angiography and Doppler flow studies.
The continuous perfusion of the right ventricle during both systole and diastole makes it less vulnerable to ischemia compared to the left ventricle, which is perfused primarily in diastole.
What if? If a patient develops severe pulmonary hypertension, the right ventricular pressure can rise significantly. This increased systolic pressure would compress the RCA, reducing or eliminating the systolic flow component and making the RV more susceptible to ischemia, similar to the LV.

How to Approach the Question

First, identify the core concept: blood flow in the coronary arteries.
Recall the major differences between the left and right ventricles, specifically the pressures they generate during systole.
Connect ventricular pressure to its effect on blood vessels within the heart muscle (intramyocardial pressure). High pressure compresses vessels, while low pressure allows them to stay open.
Deduce the flow pattern: If the vessel is compressed during systole (high LV pressure), flow is mainly in diastole (monophasic). If the vessel remains open (low RV pressure), flow occurs in both systole and diastole (biphasic).
Evaluate the options based on this physiological principle. 'Low pressure in the right ventricle' is the only option that correctly explains why the RCA can be perfused throughout the cardiac cycle.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 233-235

E6 Physiology Guyton 4SAE Part 2A p. 14-16