Heart Murmurs in Marfan Syndrome
The two primary murmurs in Marfan syndrome are: (1) a late systolic murmur from mitral regurgitation due to mitral valve prolapse, and (2) an early diastolic murmur from aortic regurgitation caused by aortic root dilatation distorting the aortic valve cusps. 1
Types of Murmurs and Their Mechanisms
Mitral Regurgitation Murmur (Most Common)
Mitral valve prolapse with regurgitation is the predominant valvular abnormality in Marfan syndrome, occurring in the majority of patients 1. The murmur characteristics include:
- Late systolic murmur at the apex, often preceded by a midsystolic click 2
- The click-murmur complex moves with changes in left ventricular volume 2
- Can progress from late systolic to holosystolic as regurgitation worsens 2
- Medium to high-pitched, sometimes with musical or honking quality 2
Mechanism: The underlying connective tissue defect (FBN1 gene mutations affecting fibrillin-1) causes myxomatous degeneration of the mitral valve leaflets with redundancy, elongated chordae tendineae, and eventual prolapse into the left atrium during systole 3, 2. This leads to malcoaptation and regurgitation.
Aortic Regurgitation Murmur (Second Most Common)
Early diastolic murmur begins immediately after S2 2:
- High-pitched, decrescendo configuration
- Best heard along left sternal border
- Increases with handgrip exercise 2
Mechanism: Progressive aortic root dilatation at the sinuses of Valsalva—the hallmark cardiovascular manifestation of Marfan syndrome—distorts the aortic valve cusps, preventing proper coaptation during diastole 1. This is a secondary form of aortic regurgitation (the valve itself is structurally normal initially, but becomes incompetent due to root geometry changes).
Clinical Prevalence
Research data demonstrates the frequency of these findings 4, 5, 6:
- Mitral valve prolapse: 79-89% of patients by echocardiography
- Mitral regurgitation murmur: 74-86% by auscultation
- Aortic regurgitation murmur: 48% by auscultation
- Combined mitral and aortic involvement: 22-34% of patients
Dynamic Auscultation Features
The mitral prolapse murmur has characteristic responses to maneuvers 2:
- Standing/Valsalva: Click occurs earlier, murmur becomes longer and louder (decreased LV volume allows earlier prolapse)
- Squatting: Click moves later, murmur becomes shorter and softer (increased LV volume delays prolapse)
- This behavior distinguishes it from other systolic murmurs
Important Clinical Pitfalls
Do not assume absence of murmur excludes significant disease. Aortic root dilatation—the most life-threatening manifestation—can be clinically silent until complicated by severe regurgitation or dissection 5. The guidelines emphasize that virtually every Marfan patient develops aortic disease during their lifetime, regardless of auscultatory findings 1.
Echocardiography is mandatory for all suspected Marfan patients, as it detects aortic root dilatation (present in 60-80% of patients) and mitral valve prolapse even when physical examination is unrevealing 7, 8.
The presence of mitral valve prolapse in Marfan syndrome differs from isolated MVP—it occurs with equal frequency across age and sex groups, has higher rates of leaflet thickening (≥5mm), and carries increased risk of complications including chordal rupture 3, 4.