When nitrates are given arterially, which effect predominates?

• A. Decrease afterload
• B. Decrease preload
• C. Increase venous return
• D. Decrease heart rate

Answer: (D)

Arterial administration of nitrates mainly lowers afterload. Nitrates release nitric oxide, which causes dilation of systemic arteries, reducing systemic vascular resistance. This makes it easier for the heart to eject blood, decreasing left ventricular wall stress and oxygen demand. While venous dilation (which reduces preload) occurs with nitrates, that effect is more pronounced at venous or lower-dose exposures; the arterial route shifts the balance toward afterload reduction. Nitrates can also cause reflex tachycardia due to the fall in blood pressure, so a decrease in heart rate is not the expected predominant effect.