Which intervention most effectively reduces myocardial oxygen demand?

Which intervention most effectively reduces myocardial oxygen demand?

• A. Elevations in afterload
• B. Increase heart rate
• C. Reduce heart rate with beta-blocker
• D. Nitrates

Answer: (D)

Myocardial oxygen demand is driven mainly by heart rate, contractility, and the wall tension the heart must generate to pump blood. Reducing wall tension lower the heart’s oxygen needs most effectively. Nitrates are potent preload reducers: they dilate veins, which lowers venous return and decreases left ventricular end-diastolic pressure. By reducing LV filling and wall stress, the heart doesn’t have to work as hard to eject blood, so its oxygen consumption drops quickly. They can also ease afterload a bit, adding to the effect. Elevating afterload would push the heart to work harder and raise oxygen demand. Increasing heart rate directly increases oxygen demand. Lowering heart rate with a beta-blocker reduces demand, but the reduction is not as immediate or as focused on wall stress as preload reduction achieved with nitrates. For rapid, substantial decreases in myocardial oxygen demand, reducing preload with nitrates is most effective.

Myocardial oxygen demand is driven mainly by heart rate, contractility, and the wall tension the heart must generate to pump blood. Reducing wall tension lower the heart’s oxygen needs most effectively. Nitrates are potent preload reducers: they dilate veins, which lowers venous return and decreases left ventricular end-diastolic pressure. By reducing LV filling and wall stress, the heart doesn’t have to work as hard to eject blood, so its oxygen consumption drops quickly. They can also ease afterload a bit, adding to the effect.

Elevating afterload would push the heart to work harder and raise oxygen demand. Increasing heart rate directly increases oxygen demand. Lowering heart rate with a beta-blocker reduces demand, but the reduction is not as immediate or as focused on wall stress as preload reduction achieved with nitrates. For rapid, substantial decreases in myocardial oxygen demand, reducing preload with nitrates is most effective.