Most Likely Diagnosis: Mitral Valve Prolapse
In an asymptomatic patient presenting with a pansystolic murmur radiating to the axilla on routine pre-employment examination, mitral valve prolapse (MVP) is the most likely diagnosis. 1, 2
Clinical Reasoning
Why MVP is Most Likely
A pansystolic murmur radiating to the axilla is pathognomonic for mitral regurgitation, and MVP is the most common valvular disorder in the United States, occurring in 1-2.5% of the population. 1, 2
The asymptomatic presentation in a young adult during routine screening strongly favors MVP as the underlying etiology, since most MVP patients remain asymptomatic throughout life with a benign prognosis. 1
MVP typically becomes clinically manifest in the third and fourth decades of life, making it the most likely finding in a pre-employment examination of a working-age adult. 3
While the classic auscultatory finding of MVP is a midsystolic click followed by a late systolic murmur, the murmur can become holosystolic (pansystolic) when regurgitation is more severe, though the patient remains asymptomatic. 4, 2
Why Other Options Are Less Likely
Ischemic Mitral Regurgitation (Option B):
- This is highly unlikely in a young, asymptomatic patient with no history suggesting coronary artery disease. 1
- Ischemic MR typically occurs in patients with prior myocardial infarction causing papillary muscle dysfunction, which would be accompanied by symptoms and risk factors. 1
Functional Mitral Regurgitation (Option C):
- Functional MR produces a midsystolic murmur, NOT a pansystolic murmur, making this diagnosis incompatible with the clinical presentation. 1, 2
- Functional MR occurs secondary to left ventricular dilation from cardiomyopathy or heart failure, which would produce symptoms such as dyspnea and fatigue. 1
Rheumatic Mitral Regurgitation (Option D):
- While rheumatic fever can cause MVP (80% of patients with prior rheumatic fever and systolic murmurs have MVP on echocardiography), rheumatic heart disease has markedly decreased prevalence in industrialized countries. 1, 5
- Rheumatic MR typically presents with mixed valvular disease and a symptomatic history of acute rheumatic fever, which is not mentioned in this case. 1
- The asymptomatic presentation during routine screening makes primary MVP far more likely than rheumatic etiology. 1
Diagnostic Confirmation
Echocardiography is indicated for diagnosis of MVP and assessment of MR severity, leaflet morphology, and ventricular compensation in this asymptomatic patient with physical signs of MVP. 4
Dynamic auscultation can support the diagnosis: the murmur typically becomes louder with Valsalva maneuver or standing (which decreases preload) and softer with squatting (which increases preload). 1, 2
Clinical Significance
MVP has a benign prognosis in most patients, with age-adjusted survival similar to the general population. 1
The complication rate is approximately 2% per year, with sudden death occurring in fewer than 2% of cases during long-term follow-up. 4
Approximately 5% of affected men and 1.5% of affected women ultimately require valve surgery, with complications concentrated disproportionately in older men. 6
All patients with MVP should receive antibiotic prophylaxis prior to surgical or dental procedures to prevent endocarditis. 7