Which drug causes vasodilation to increase venous capacity thus lowers preload?

Which drug causes vasodilation to increase venous capacity thus lowers preload?

• A. Lasix
• B. Atenolol
• C. Nifedipine
• D. Hydralazine

Answer: (A)

Preload is the filling pressure of the ventricles, largely determined by venous return to the heart. Increasing venous capacity would tend to reduce venous return and thus preload, but among these options the most direct way to lower preload is by reducing the circulating blood volume. Lasix is a diuretic that increases urine output, which lowers intravascular volume and venous return, thereby decreasing preload. The other drugs don’t primarily reduce preload through volume loss: atenolol lowers heart rate and contractility, nifedipine mainly causes arterial dilation (reducing afterload), and hydralazine mainly dilates arteries with variable effects on venous return.

Preload is the filling pressure of the ventricles, largely determined by venous return to the heart. Increasing venous capacity would tend to reduce venous return and thus preload, but among these options the most direct way to lower preload is by reducing the circulating blood volume. Lasix is a diuretic that increases urine output, which lowers intravascular volume and venous return, thereby decreasing preload. The other drugs don’t primarily reduce preload through volume loss: atenolol lowers heart rate and contractility, nifedipine mainly causes arterial dilation (reducing afterload), and hydralazine mainly dilates arteries with variable effects on venous return.