How does the murmur of mitral valve prolapse (MVP) respond to increased preload?

In mitral valve prolapse (MVP), the characteristic murmur is often a mid-systolic click followed by a late systolic murmur. This auscultatory finding is influenced by the dynamics of the heart and the positioning of the mitral valve during the cardiac cycle.

When preload increases, as seen in conditions that enhance venous return to the heart (such as during physical exertion or when lying down), the volume of blood within the left ventricle increases. This enhanced volume causes the left ventricle to stretch more, leading to an increase in the tension of the chordae tendineae and potentially causing the prolapsed segment of the mitral valve to occur later in systole. As a result, the duration of the murmur may be shorter or it might blend more with the heart sounds, thus leading to an apparent improvement in the murmur associated with MVP.

This response enables clinicians to understand that changes in preload can dynamically affect the murmur associated with MVP and is an essential consideration when evaluating patients with this condition.