9. Milrinone (a positive inotropic drug) would have this effect on a pathologic S3 heart sound?

A. Increase in intensity

B. Decrease in intensity

C. No effect 

The third heart sound (S3), also known as the "ventricular gallop", occurs just after S2 when the mitral valve opens allowing passive filling of the left ventricle. The S3 sound is actually produced by the large amount of blood striking a very compliant left ventricle (LV). A S3 can be an important sign of systolic heart failure, since in this setting the myocardium is usually overly compliant resulting in a dilated LV. Cardiac inotropes such as milrinone will increase contractility and decrease compliance and can result in the S3 heart sound disappearing.