How is the type of heart murmur diagnosed?

Diagnosis of Heart Murmur Type

The type of heart murmur is diagnosed through systematic cardiac auscultation combined with dynamic maneuvers, followed by echocardiography when indicated based on specific clinical and auscultatory features. 1

Initial Auscultatory Assessment

The diagnosis begins with characterizing the murmur's fundamental properties during cardiac examination:

Timing in the Cardiac Cycle

• Systolic murmurs occur between S1 and S2 and include midsystolic (crescendo-decrescendo), holosystolic/pansystolic (plateau-shaped throughout systole), and late systolic patterns 1, 2
• Diastolic murmurs occur after S2 and virtually always indicate pathological conditions requiring immediate echocardiographic evaluation 1, 2
• Continuous murmurs span both systolic and diastolic phases (excluding innocent cervical venous hums or mammary souffles in pregnancy) and mandate further workup 1

Location and Radiation

• Mitral regurgitation produces murmurs best heard at the apex radiating to the axilla 3
• Tricuspid regurgitation is loudest at the lower left sternal border 3
• Aortic stenosis is maximal at the second right intercostal space with radiation to the carotids 1

Intensity Grading

• Systolic murmurs are graded 1-6, with grade ≥3 requiring echocardiography regardless of other findings 1, 2
• Diastolic murmurs are graded 1-4, with all grades requiring echocardiographic evaluation 2

Dynamic Auscultation for Differential Diagnosis

Dynamic maneuvers are essential for distinguishing murmur etiology:

Respiratory Variation

• Right-sided murmurs (tricuspid regurgitation, pulmonic stenosis) increase with inspiration 1, 3
• Left-sided murmurs typically increase with expiration 1

Positional Changes

• Hypertrophic cardiomyopathy: murmur becomes louder with standing and Valsalva, softer with squatting 1
• Mitral valve prolapse: click-murmur complex moves earlier (closer to S1) with standing/Valsalva, later (toward S2) with squatting 1, 4
• Most other murmurs: diminish with standing, increase with squatting 1

Exercise and Handgrip

• Mitral regurgitation, ventricular septal defect, and aortic regurgitation: increase with sustained handgrip exercise 1
• Aortic stenosis and mitral stenosis: increase with exercise due to increased flow 1

Post-Premature Beat Response

• Aortic stenosis: increases in intensity after a ventricular premature beat or long R-R interval in atrial fibrillation 1
• Mitral regurgitation and ventricular septal defect: do not increase or may decrease after premature beats 1

Indications for Echocardiography

Echocardiography provides definitive diagnosis and is mandatory in specific scenarios:

Absolute Indications (Regardless of Murmur Grade)

• All diastolic murmurs (excluding innocent venous hums) 1, 2
• All continuous murmurs (excluding mammary souffles in pregnancy) 1
• Holosystolic or late systolic murmurs at the apex or left sternal edge 1, 2
• Any systolic murmur grade ≥3 1, 2

Symptomatic Presentations

• Syncope, angina, heart failure, myocardial ischemia/infarction, or thromboembolism accompanying any murmur 1, 2
• Signs of infective endocarditis 1, 2

Specific Dynamic Auscultation Findings

• Murmurs that increase with Valsalva/standing and decrease with squatting (suggesting hypertrophic cardiomyopathy or mitral valve prolapse) 1
• Murmurs that increase with transient arterial occlusion or handgrip (suggesting mitral regurgitation or ventricular septal defect) 1
• Murmurs that fail to increase after premature ventricular contractions (suggesting mitral regurgitation or ventricular septal defect) 1

Additional Physical Findings

• Widely split second heart sounds or systolic ejection sounds 1, 2
• Abnormal ECG or chest X-ray showing ventricular hypertrophy or atrial enlargement 1, 2

When Echocardiography is NOT Required

Asymptomatic adults with grade 1-2 midsystolic murmurs meeting ALL of the following criteria do not require immediate echocardiography 1, 2:

• Systolic ejection pattern at the left sternal border
• Normal intensity and splitting of S2
• No other abnormal cardiac sounds
• No evidence of ventricular hypertrophy or dilatation
• No increase with Valsalva or standing
• Normal ECG and chest X-ray (if obtained)
• Normal exercise capacity

These represent innocent or functional murmurs, particularly common in high-output states like anemia or pregnancy 1

Critical Pitfalls

• Elderly patients with aortic stenosis may lack the classic parvus et tardus pulse due to vascular aging, potentially leading to underestimation of severity 1
• Trivial physiological regurgitation (especially mitral, tricuspid, or pulmonic) is detected by echocardiography in many normal patients without audible murmurs, requiring clinical correlation 1
• Combined valvular lesions (particularly aortic and mitral disease) are frequently missed on physical examination alone, with sensitivity only 55% 5
• Aortic regurgitation commonly presents with a systolic murmur rather than the classic diastolic murmur, especially when detected by non-cardiologists 6
• Severely reduced left ventricular ejection fraction can cause underestimation of aortic stenosis severity due to diminished murmur intensity 5