Pansystolic Murmur Causes and Diagnosis

Pathophysiological Mechanism

Pansystolic murmurs are characterized by a sound that begins with S1 and continues throughout systole until S2, typically plateau-shaped in configuration, and are generated when blood flows between chambers with significant pressure differences throughout systole 1, 2, 3, 4

Mitral regurgitation is caused by backward flow from left ventricle to left atrium due to mitral valve prolapse with leaflet malcoaptation, rheumatic heart disease affecting valve leaflets, papillary muscle dysfunction or rupture, functional MR due to left ventricular dilation and annular enlargement, infective endocarditis with leaflet destruction, and congenital mitral valve abnormalities 2, 3, 4, 5
Tricuspid regurgitation is caused by backward flow from right ventricle to right atrium due to pulmonary hypertension causing right ventricular dilation, right ventricular failure with annular dilation, infective endocarditis, rheumatic heart disease, and carcinoid heart disease 2, 3, 4, 5, 6
Ventricular septal defects are abnormal communications between left and right ventricles, which can be congenital or acquired, and may be caused by post-surgical complications 3, 4

Mitral regurgitation murmurs are typically best heard at the apex and radiate to the axilla, while tricuspid regurgitation murmurs are usually loudest at the lower left sternal border and may increase with inspiration 5, 7

Echocardiography is the gold standard for confirming the cause of a pansystolic murmur, and dynamic auscultation can help differentiate causes, with right-sided murmurs typically increasing with inspiration and left-sided murmurs usually louder during expiration 3, 7

Pansystolic murmurs almost always indicate pathological conditions requiring further evaluation, and early identification and management of the underlying cause can prevent complications such as heart failure, pulmonary hypertension, and arrhythmias 3, 5

The American College of Cardiology notes that the pansystolic murmur radiating to the axilla is characteristic of mitral regurgitation, and when mitral valve prolapse (MVP) progresses, it can present with either a late systolic murmur or a pansystolic murmur depending on severity 8
The murmur of mitral regurgitation associated with anterior leaflet pathology radiates to the axilla and left infrascapular area, which matches the patient's presentation 8
Dynamic auscultation should be performed to confirm the diagnosis, with the murmur typically becoming louder with Valsalva maneuver or standing and softer with squatting, as recommended by the American Heart Association 9 and the American College of Cardiology 10

Echocardiography is essential to confirm the diagnosis and assess the severity of mitral regurgitation, although the article does not provide a specific citation for this fact, it is a widely accepted recommendation

The American College of Cardiology notes that the pansystolic murmur radiating to the axilla is characteristic of mitral regurgitation, and when mitral valve prolapse (MVP) progresses, it can present with either a late systolic murmur or a pansystolic murmur depending on severity 8
The murmur of mitral regurgitation associated with anterior leaflet pathology radiates to the axilla and left infrascapular area, which matches the patient's presentation 8
Dynamic auscultation should be performed to confirm the diagnosis, with the murmur typically becoming louder with Valsalva maneuver or standing and softer with squatting, as recommended by the American Heart Association 9 and the American College of Cardiology 10

A pansystolic murmur radiating to the axilla is pathognomonic for mitral regurgitation, specifically indicating anterior leaflet pathology according to the American College of Cardiology 11
The asymptomatic presentation in a young adult undergoing routine pre-employment screening strongly favors MVP as the underlying etiology 12
MVP is the most common valvular disorder diagnosed in the United States, occurring in 1-2.5% of the population using modern echocardiographic criteria 12
Ischemic mitral regurgitation is unlikely in a young and asymptomatic patient with no history suggesting ischemic heart disease, as it typically occurs in patients with coronary artery disease and prior myocardial infarction causing papillary muscle dysfunction 11
Functional mitral regurgitation is unlikely because it produces a midsystolic murmur, not a pansystolic murmur, and occurs secondary to left ventricular dilation from cardiomyopathy or heart failure, which would produce symptoms 11, 13
Rheumatic mitral regurgitation is less likely because rheumatic heart disease has markedly decreased prevalence in industrialized countries, and it typically presents with mixed valvular disease and a symptomatic history 13

MVP has a benign prognosis in most patients, with age-adjusted survival similar to the general population 12
Patients with thickened mitral valve leaflets (≥5 mm) have an increased risk of complications, including endocarditis, progressive MR requiring surgery, and arrhythmias 12

Approximately 5% of affected men and 1.5% of affected women ultimately require valve surgery, with complications concentrated disproportionately in older men (no citation, but included for context, however 12 does discuss MVP)
The complication rate is approximately 2% per year, with most patients remaining asymptomatic throughout life (no citation, however 12 does discuss MVP)

A pansystolic murmur radiating to the axilla can become holosystolic when regurgitation is more severe in mitral valve prolapse (MVP), although the patient remains asymptomatic, as reported by the American Heart Association 14
Echocardiography is indicated for diagnosis of MVP and assessment of mitral regurgitation severity, leaflet morphology, and ventricular compensation in asymptomatic patients with physical signs of MVP, according to the American College of Cardiology 14

MVP has a complication rate of approximately 2% per year, with sudden death occurring in fewer than 2% of cases during long-term follow-up, as noted in guidelines from the American Heart Association 14

In patients with mitral valve prolapse, the intensity of the pansystolic murmur decreases when the patient squats (preload increase), whereas it becomes louder with Valsalva or standing (preload decrease), reflecting the preload‑dependent nature of the prolapse. 15

The midsystolic click‑murmur complex of mitral valve prolapse can be mistaken for a benign flow murmur if the ejection click is not identified, potentially delaying appropriate echocardiographic evaluation. 16