What is a heart murmur?

A heart murmur is an extra or unusual sound heard through a stethoscope during the cardiac cycle. Murmurs are caused by turbulent blood flow through the heart or its valves. While many murmurs are innocent (harmless), some indicate structural valve disease or other cardiac pathology requiring specialist assessment and monitoring.

Innocent murmur — features

• Soft (grades 1–2/6), systolic, short
• No radiation
• Varies with position and respiration
• No associated symptoms or abnormal signs
• Normal ECG and chest X-ray

Common pathological causes

• Aortic stenosis: Harsh ejection systolic murmur radiating to carotids. Most common valve disease in elderly.
• Mitral regurgitation: Pansystolic murmur at the apex radiating to the axilla. Caused by mitral valve prolapse, rheumatic disease, or functional MR.
• Aortic regurgitation: Early diastolic decrescendo murmur. Associated with aortic root dilatation.
• Mitral stenosis: Rare in Australia; more common in patients from endemic regions for rheumatic fever.
• Bicuspid aortic valve: Congenital, present in ~1% of population. Often identified as an ejection click + murmur.
• Hypertrophic cardiomyopathy: Dynamic ejection systolic murmur that increases with Valsalva and decreases with squatting.
• Tricuspid regurgitation: Pansystolic murmur at left sternal edge, increases with inspiration.

Symptoms of significant valve disease

• Breathlessness on exertion
• Chest pain or angina
• Syncope or presyncope (especially with aortic stenosis)
• Palpitations
• Fatigue and reduced exercise tolerance
• Ankle swelling (right heart failure)

• Echocardiogram: Gold standard. Visualises valve morphology, Doppler assessment of stenosis severity and regurgitation, ventricular size and function.
• ECG: May show LVH, left atrial enlargement, AF or conduction abnormalities.
• Chest X-ray: Assesses cardiac silhouette, pulmonary congestion, aortic dilatation.
• Exercise stress echo: For patients with asymptomatic moderate-severe valve disease — unmasks symptoms and assesses haemodynamic response.
• CT / cardiac MRI: Used for aortic root/ascending aorta assessment in bicuspid aortic valve disease, and pre-procedural planning.

Surveillance echocardiography — frequency

Management depends entirely on the type and severity of valve disease. Innocent murmurs require no treatment.

Medical management

• Heart failure therapies for functional MR or AR with LV dysfunction
• Rate control in AF with valvular disease
• Anticoagulation for mitral stenosis with AF
• Endocarditis prophylaxis: not routinely recommended in Australia unless prior endocarditis, prosthetic valve or specific congenital conditions

Surgical / interventional treatment

• Aortic valve replacement (surgical SAVR or transcatheter TAVI) for severe AS
• Mitral valve repair or replacement for severe symptomatic MR
• Transcatheter edge-to-edge repair (MitraClip) for high surgical risk patients with severe MR
• Balloon mitral valvuloplasty for suitable mitral stenosis
• Timing of intervention guided by symptoms, LV function and valve haemodynamics

• Innocent murmurs: normal lifespan, no restrictions, no follow-up required
• Mild-moderate valve disease: regular surveillance echocardiography; most patients remain stable for years
• Severe valve disease: timely intervention restores quality of life and reduces mortality
• Post-valve replacement: regular follow-up, anticoagulation if mechanical valve, bacterial endocarditis awareness
• Physical activity: innocent murmurs — unrestricted; significant valve disease — discuss with cardiologist before competitive sport