What is the characteristic murmur heard in mitral valve (MV) prolapse?

From the Guidelines

The characteristic murmur heard in mitral valve prolapse (MVP) is a mid-to-late systolic click followed by a high-pitched, late systolic murmur best heard at the apex of the heart. This murmur occurs when the mitral valve leaflets prolapse back into the left atrium during ventricular contraction, causing mitral regurgitation 1. The click represents the sudden tensing of the redundant valve leaflets, while the murmur results from blood flowing backward through the incompetent valve.

Key Characteristics of the Murmur

• The timing and intensity of both the click and murmur can vary with physiologic maneuvers, such as standing or Valsalva maneuver, which causes the click and murmur to occur earlier in systole, while squatting or handgrip delays them 1.
• The murmur is typically medium-to high-pitched and loudest at the cardiac apex, and may have a musical or honking quality 1.
• The murmur can radiate to the left axilla and may be accompanied by a palpable thrill in severe cases.

Diagnostic Evaluation

• The primary diagnostic evaluation of the patient with MVP is the physical examination, with the principal auscultatory feature being the midsystolic click and late systolic murmur 1.
• Two-dimensional and Doppler echocardiography is the most useful noninvasive test for defining MVP, and can help assess the severity of mitral regurgitation and leaflet morphology 1.

Management

• Reassurance is a major part of the management of patients with MVP, and patients with mild or no symptoms and findings of milder forms of prolapse should be reassured of the benign prognosis 1.
• A normal lifestyle and regular exercise is encouraged, and antibiotic prophylaxis may be recommended for patients with a definite diagnosis of MVP, particularly if there is associated mitral regurgitation 1.

From the Research

Characteristic Murmur of Mitral Valve Prolapse

• The characteristic murmur heard in mitral valve (MV) prolapse is a late systolic murmur, which frequently follows a midsystolic click 2.
• This murmur is often described as a late systolic murmur or a mid-systolic click, and may be accompanied by a midsystolic click 3, 4.
• The murmur may vary in intensity and duration, and can be affected by changes in preload and other hemodynamic conditions 5.
• In some cases, the murmur may be a high-pitched crescendo murmur that starts immediately after the first sound and ends approximately 100 ms before the second sound 5.
• The presence and characteristics of the murmur can be an important diagnostic feature of mitral valve prolapse, and can be used to guide further evaluation and management 2, 6.

Variability of the Murmur

• The murmur associated with mitral valve prolapse can be variable, and may change in response to different physiologic and pharmacologic maneuvers 5.
• The onset and amplitude of the systolic murmurs, as well as the endpoint of systolic murmurs, can be dynamically altered according to preload 5.
• In some cases, the murmur may be softer or more faint, and may require careful auscultation to detect 5.
• Echocardiography can be a useful tool in evaluating the severity of mitral regurgitation and guiding management decisions 2, 5.

Clinical Significance of the Murmur

• The presence of a murmur in mitral valve prolapse can be an important indicator of the severity of the condition, and can guide further evaluation and management 2, 6.
• Patients with mitral valve prolapse and a murmur may be at increased risk of complications such as mitral regurgitation, arrhythmias, and endocarditis 2, 3, 4.
• Antibiotic prophylaxis may be recommended for patients with mitral valve prolapse and a murmur, particularly those with thickened or redundant leaflets seen on echocardiography 2, 4.