Most Likely Diagnosis: Mitral Valve Prolapse
In an asymptomatic young man with a pansystolic murmur radiating to the axilla discovered on routine examination, mitral valve prolapse (MVP) is the most likely diagnosis. 1, 2
Clinical Reasoning
Why MVP is Most Likely
MVP is the most common cardiac valvular abnormality detected in young individuals, particularly during the second and third decades of life, and frequently affects asymptomatic patients of slender body habitus. 3
The pansystolic murmur radiating to the axilla is characteristic of mitral regurgitation, and when MVP progresses, it can present with either a late systolic murmur or a pansystolic murmur depending on severity. 4, 2
In asymptomatic young adults discovered incidentally, MVP is far more common than other causes of mitral regurgitation, with studies showing 37% of MVP cases are discovered by chance during routine examinations. 5
The age and asymptomatic presentation strongly favor MVP over other etiologies: rheumatic mitral regurgitation typically presents with symptoms and a history of rheumatic fever, while ischemic MR requires coronary artery disease (uncommon in young patients), and functional MR requires underlying left ventricular dysfunction. 6, 7
Why Other Options Are Less Likely
Rheumatic mitral regurgitation (Option D) would require a documented history of rheumatic fever and typically presents with congestive heart failure (89.4% of cases) and atrial fibrillation (48.9% of cases) rather than being asymptomatic. 7
Ischemic mitral regurgitation (Option B) occurs secondary to coronary artery disease with papillary muscle dysfunction or rupture, which is extremely unlikely in a young asymptomatic man without risk factors. 2
Functional mitral regurgitation (Option C) results from left ventricular dilation and annular enlargement due to underlying cardiomyopathy, which would typically produce symptoms and other examination findings. 4, 2
Key Clinical Pearls
Examination Findings in MVP
Systolic clicks are present in 54% of MVP patients, though 23% have late systolic murmurs and 16% have pansystolic murmurs, with the incidence of murmurs rising with age. 5
Pansystolic murmurs in MVP are more frequent in males and indicate more significant regurgitation, though many patients remain asymptomatic despite this finding. 5
The murmur of mitral regurgitation associated with anterior leaflet pathology radiates to the axilla and left infrascapular area, which matches this patient's presentation. 4
Important Pitfall to Avoid
- The click-murmur of MVP may be misdiagnosed as other conditions, and dynamic auscultation should be performed to confirm the diagnosis, with the murmur typically becoming louder with Valsalva maneuver or standing and softer with squatting. 4
Next Steps
Echocardiography is essential to confirm the diagnosis and assess the severity of mitral regurgitation, as clinical examination alone has variable sensitivity for detecting significant valve disease. 1, 2
All patients with MVP should receive antibiotic prophylaxis prior to surgical or dental procedures if significant regurgitation is present, though current guidelines have modified these recommendations. 8
The long-term prognosis requires monitoring, as complications including severe mitral incompetence (7%), bacterial endocarditis (4%), and arrhythmias (13% supraventricular tachycardia) can develop, contrary to earlier beliefs about benign prognosis. 5