Coronary Artery Disease USMLE Step 1 Practice Question
A 62-year-old man with hypertension presents with chest pain and dyspnea on exertion. Vital signs show BP 158/92 mmHg, HR 88 bpm, RR 18/min, SpO2 98% on room air. ECG demonstrates ST-segment depression in leads V4-V6. Troponin is elevated at 0.8 ng/mL. He denies recent cocaine use. During acute coronary syndrome management, IV fluids increase end-diastolic volume, causing increased stroke volume without sympathomimetic agents. Which mechanism best explains this cardiac response?
Answer choices
- AReduced venous return decreases myocardial fiber length
- BGreater preload increases sarcomere stretch and contractile forceCorrect answer
- CIncreased afterload from arterial vasoconstriction
- DReduced ventricular compliance lowers filling pressure
- EDecreased calcium entry during phase 2 of the action potential
- FPositive inotropic effect from catecholamine release during acute ischemia
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