Cardiovascular System MCAT Practice Question
A 62-year-old male with atherosclerosis undergoes cardiac catheterization revealing a 70% stenosis in the left anterior descending coronary artery. The cardiologist explains that this narrowing increases resistance to blood flow according to Poiseuille's equation. Which of the following best describes how this stenosis affects coronary blood flow and myocardial oxygen delivery?
Answer choices
- AFlow decreases proportionally to the reduction in vessel diameter
- BFlow decreases inversely with the fourth power of the radius, severely limiting oxygen delivery during increased demandCorrect answer
- CFlow increases due to compensatory vasodilation of stenotic segment
- DFlow remains constant because collateral circulation immediately compensates
- EFlow is unaffected because pressure gradients remain unchanged
- FFlow decreases linearly with the cross-sectional area of the vessel, with minimal impact on oxygen delivery during exercise
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