Other than administering supplemental oxygen, how can the supply of oxygen to the myocardium be increased in a patient with suspected ACS?

• A. Elevate body temperature
• B. Lower heart rate
• C. Increase strenuous activity
• D. Increase fluid intake

Answer: (B)

Lowering the heart rate is the best way to boost myocardial oxygen supply in suspected ACS because slower rate lengthens diastole, the phase when coronary arteries mostly perfuse the heart. More time in diastole means more coronary blood flow and oxygen delivery to the myocardium. At the same time, a slower heart rate decreases myocardial oxygen demand by reducing wall stress and the amount of work the heart has to do. Together, this improves the balance between oxygen supply and demand when the heart is stressed.

Elevating body temperature would increase metabolic demands and oxygen needs, not help. Increasing strenuous activity raises oxygen consumption and reduces diastolic perfusion time, worsening supply. Increasing fluid intake might change preload, but it doesn’t reliably increase oxygen delivery to the heart and can risk edema or fluid overload in ACS.