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Coronary perfusion during tachycardia — FRCA Primary MCQ

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HardPhysiologyCoronary perfusion during tachycardiaFRCA Primary

A patient with severe left ventricular hypertrophy becomes tachycardic and hypotensive during laryngoscopy. ST depression appears despite normal oxygen saturation. Which physiological issue is most important?

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Correct answer: A — Reduced diastolic coronary perfusion time

Most left ventricular coronary perfusion occurs during diastole, and tachycardia shortens diastole while increasing oxygen demand. Systolic perfusion is limited by intramyocardial compression, especially in hypertrophy. Myocardial oxygen demand rises rather than falls with tachycardia and hypertension. Maintaining diastolic pressure and avoiding tachycardia are central in hypertrophied or ischaemic hearts.

Reference: Ganong Review of Medical Physiology; Primary FRCA physiology texts