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?
- A)Reduced venous return decreases myocardial fiber length
- B)Greater preload increases sarcomere stretch and contractile forceGABARITO
- C)Increased afterload from arterial vasoconstriction
- D)Reduced ventricular compliance lowers filling pressure
- E)Decreased calcium entry during phase 2 of the action potential
Explicação
Greater preload increases sarcomere stretch and contractile force is correct. The Frank Starling mechanism states that increased ventricular filling increases stroke volume because myocardial fibers contract more forcefully when stretched to an optimal length.... Ver explicação completa e trilha adaptativa →