What effect does Valsalva maneuver have on murmurs?

The Valsalva maneuver involves forcibly exhaling against a closed airway, which leads to changes in intrathoracic pressure and subsequently affects venous return to the heart and cardiac output. During this maneuver, several physiological changes occur, including a transient decrease in venous return, which typically results in a reduction in stroke volume and ultimately affects the intensity of murmurs.

In most cases, murmurs that are volume-dependent—such as those produced by conditions like aortic or mitral regurgitation—will become less intense during the Valsalva maneuver because there is less blood flowing across the valves during this time. The decrease in blood volume reaching the heart leads to a reduction in the severity of these abnormal sounds.

Consequently, all murmurs that are dependent on blood volume and flow for their intensity tend to decrease in volume with the Valsalva maneuver. This is the fundamental rationale for why the correct response points to a decrease in all murmurs' intensity. The effect of the maneuver reflects the underlying hemodynamic changes that occur rather than a selective impact on specific types of murmurs.