Cardiovascular System MCAT Practice Question
Researchers investigate myocardial oxygen consumption (MVO₂) in different cardiac conditions. The rate-pressure product (heart rate × systolic blood pressure) serves as a clinical surrogate for MVO₂. A patient taking a beta-blocker shows reduced heart rate and contractility. Based on cardiac energetics principles, which of the following best explains the benefit of beta-blockade in reducing myocardial oxygen demand?
Answer choices
- AIncreased stroke volume compensates for decreased heart rate
- BDecreased contractility and heart rate reduce wall tension and total metabolic cost of contractionCorrect answer
- CEnhanced oxygen extraction from coronary blood maintains myocardial function
- DDecreased systolic blood pressure increases coronary perfusion pressure
- EReduced preload decreases diastolic wall stress
- FIncreased coronary vasodilation improves oxygen delivery despite reduced cardiac workload
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