Heart Murmurs: A Practical Clinical Guide
Understanding Heart Murmurs
Heart murmurs result from turbulent blood flow through cardiac structures, occurring in up to 80% of children and 52% of adults, with most being innocent and requiring no intervention. 1
Primary Mechanisms of Murmur Production
- High blood flow through normal or abnormal orifices (pregnancy, thyrotoxicosis, anemia, arteriovenous fistula) 2
- Forward flow through narrowed or irregular orifices into dilated vessels or chambers 2
- Backward/regurgitant flow through incompetent valves 2
Grading System You Must Know
Systolic Murmurs (6-Point Scale)
- Grade 1/6: Very faint, barely audible 3
- Grade 2/6: Soft but readily heard 3
- Grade 3/6: Moderately loud, no thrill 3
- Grade 4/6: Loud with palpable thrill 3
- Grade 5/6: Very loud, heard with stethoscope partially off chest 3
- Grade 6/6: Extremely loud, heard with stethoscope off chest 3
Diastolic Murmurs (4-Point Scale)
- Graded 1-4, with all grades being pathological and requiring evaluation 3
Critical Decision Algorithm: When to Order Echocardiography
IMMEDIATE Echocardiography Required (No Exceptions)
By Murmur Timing:
- ALL diastolic murmurs (virtually always pathological) 3, 2
- ALL continuous murmurs 3
- ALL holosystolic murmurs (at apex or left sternal edge) 3
- ALL late systolic murmurs (at apex or left sternal edge) 3
By Murmur Intensity:
By Associated Symptoms:
- ANY murmur with syncope 3
- ANY murmur with angina 3
- ANY murmur with heart failure symptoms 3
- ANY murmur with thromboembolism 3
By Dynamic Auscultation Findings:
- Increases with Valsalva or standing (suggests hypertrophic cardiomyopathy or mitral valve prolapse) 3
- Increases with transient arterial occlusion or sustained handgrip 3
- Does NOT increase after premature ventricular contraction (suggests mitral regurgitation or VSD) 3
When Echocardiography is Indicated for Grade 1-2 Midsystolic Murmurs
Even soft murmurs require imaging when red flags are present:
- Symptoms of infective endocarditis 3
- Thromboembolism has occurred 3
- Heart failure symptoms present 3
- Myocardial ischemia/infarction suspected 3
- Syncope has occurred 3
- Abnormal physical findings: widely split S2, systolic ejection sounds 3
- ECG or chest X-ray abnormalities: ventricular hypertrophy, atrial enlargement 3
Innocent Murmurs: When NO Workup is Needed
In asymptomatic adults, you can confidently avoid echocardiography when ALL of the following are present:
- Grade 1-2 intensity at left sternal border 3
- Systolic ejection pattern (crescendo-decrescendo) 3
- Normal intensity and splitting of S2 3
- No other abnormal sounds or murmurs 3
- No evidence of ventricular hypertrophy or dilatation on exam 3
- Does NOT increase with Valsalva or standing 3
- Normal ECG and chest X-ray 3
Common Causes by Murmur Type
Systolic Murmurs:
- Aortic stenosis: Most frequent pathological cause requiring valve replacement in adults, crescendo-decrescendo at right upper sternal border radiating to carotids 2, 4
- Aortic sclerosis: Extremely common in older adults with hypertension, focal thickening without significant obstruction 2
- Mitral regurgitation: Holosystolic at apex radiating to axilla 2
- Hypertrophic cardiomyopathy: Increases with Valsalva/standing 2
- Mitral valve prolapse: Late systolic with mid-systolic click 2
- Ventricular septal defect: Holosystolic at left sternal border 2
Diastolic Murmurs:
- Aortic regurgitation: Early diastolic, high-pitched at left sternal border 2
- Mitral stenosis: Mid-diastolic rumble at apex with opening snap 2
- Tricuspid stenosis: Mid-diastolic at lower left sternal border 2
- Austin-Flint murmur: Functional mitral stenosis from severe chronic aortic regurgitation 2
Continuous Murmurs:
- Patent ductus arteriosus: Machinery-like murmur at left infraclavicular area 2
Key Physical Examination Findings
Aortic Stenosis Red Flags:
- Soft or absent A2 4
- Reversed splitting of S2 in severe cases 4
- Left ventricular hypertrophy on palpation 4
- Murmur increases after premature ventricular beats 4
Dynamic Auscultation Techniques:
- Valsalva maneuver: Decreases most murmurs except hypertrophic cardiomyopathy and mitral valve prolapse (which increase) 3
- Standing: Same effect as Valsalva 3
- Squatting: Opposite effect—increases most murmurs, decreases hypertrophic cardiomyopathy 3
- Handgrip exercise: Increases mitral regurgitation and aortic regurgitation 3
Critical Pitfalls to Avoid
Common Diagnostic Errors:
- Trivial valvular regurgitation detected by echo in normal patients with no audible murmur is physiological and not clinically significant 3
- In older patients with hypertension, grade 1-2 midsystolic murmurs may be from sclerotic aortic valve leaflets or flow into tortuous vessels, not necessarily pathological 3
- Clinically significant aortic stenosis, aortic regurgitation, mitral regurgitation, and hypertrophic cardiomyopathy are frequently missed or misinterpreted by auscultation alone 5
Age-Specific Considerations:
- Neonatal murmurs are more likely to represent structural heart disease and warrant echocardiography 6
- In children, family history of sudden cardiac death, congenital heart disease, maternal diabetes, or genetic disorders increases likelihood of pathology 6
Special Populations
Children and Adolescents:
- Clinical examination by experienced pediatric cardiologist has 96% sensitivity and 95% specificity for detecting pathological murmurs 7
- ECG rarely changes diagnosis in children with murmurs 7
- Red flags in children: holosystolic or diastolic murmur, grade ≥3, harsh quality, abnormal S2, maximal intensity at upper left sternal border, systolic click, increased intensity when standing 6