Does mitral stenosis (narrowing of the mitral valve) cause a murmur?

Mitral Stenosis Causes a Characteristic Diastolic Murmur

Yes, narrowing of the mitral valve opening (mitral stenosis) causes a characteristic middiastolic or presystolic murmur. 1, 2

Characteristics of Mitral Stenosis Murmur

Mitral stenosis produces a distinctive murmur with the following features:

• Timing: Middiastolic murmur that may extend into presystole (if in sinus rhythm)
• Location: Best heard at the apex of the heart
• Quality: Low-pitched, rumbling in character
• Radiation: Localized to the apex, minimal radiation
• Associated findings: Often preceded by an opening snap

The murmur occurs due to turbulent blood flow across the narrowed mitral valve during diastole when blood flows from the left atrium to the left ventricle 1.

Pathophysiology of Mitral Stenosis Murmur

The murmur of mitral stenosis results from:

1. Restricted valve opening: Narrowing of the mitral valve orifice creates a pressure gradient between the left atrium and left ventricle
2. Turbulent flow: Blood accelerates as it passes through the stenotic valve, creating audible turbulence
3. Timing relationship: The murmur occurs during ventricular filling in diastole when blood flows across the mitral valve 1, 2

According to the American College of Cardiology/American Heart Association guidelines, middiastolic murmurs usually originate from the mitral and tricuspid valves and occur early during ventricular filling due to "a relative disproportion between valve orifice size and diastolic blood flow volume" 1.

Differentiating Features from Other Murmurs

The mitral stenosis murmur can be distinguished from other murmurs by:

• Timing: Occurs in diastole (between S2 and the next S1), unlike systolic murmurs
• Duration: Typically middiastolic, sometimes extending into presystole if in sinus rhythm
• Quality: Low-pitched, rumbling (requires bell of stethoscope pressed lightly)
• Response to maneuvers: Becomes louder with exercise and in left lateral position 2

It's important to note that diastolic murmurs are virtually always pathological and require further cardiac evaluation, according to the American Heart Association and American College of Cardiology 2.

Etiology of Mitral Stenosis

The causes of mitral stenosis include:

• Rheumatic heart disease: Still the most common cause worldwide 3
• Degenerative/calcific changes: Increasingly common in developed countries, especially in elderly patients 3, 4
• Congenital: Rare cause of mitral stenosis

Clinical Significance and Evaluation

The presence of a mitral stenosis murmur has important clinical implications:

• Indicates significant narrowing of the mitral valve (usually when valve area is <1.5 cm²) 5
• Associated with symptoms like dyspnea, fatigue, and potentially pulmonary edema as severity increases
• May be accompanied by other findings like an opening snap, signs of pulmonary hypertension, or atrial fibrillation

Echocardiography is the definitive diagnostic tool to confirm mitral stenosis, assess its severity, and evaluate valve morphology 2, 5.

Common Pitfalls in Diagnosis

Several pitfalls can occur when evaluating mitral stenosis murmurs:

• Confusion with Austin-Flint murmur: A low-pitched diastolic murmur at the apex in severe aortic regurgitation that can mimic mitral stenosis 1
• Missing the murmur: The low-pitched nature requires careful auscultation with the bell of the stethoscope
• Atrial fibrillation effects: In patients with atrial fibrillation, the presystolic component of the murmur is absent, and the intensity varies with cycle length 6
• Overlooking degenerative mitral stenosis: In elderly patients, calcific mitral stenosis may be missed if not specifically considered 4

The presence of a diastolic murmur should always prompt further evaluation, as diastolic murmurs are rarely innocent or physiologic 2.