Grading of Heart Murmurs
Heart murmurs are traditionally graded on a scale of 1 through 6 for systolic murmurs and 1 through 4 for diastolic murmurs, based on their intensity, which is an essential component of cardiac auscultation assessment. 1
Systolic Murmur Grading Scale (1-6)
- Grade 1: Very faint, barely audible murmur that can only be heard after the listener has "tuned in"; may not be heard in all positions 2, 1
- Grade 2: Quiet, but clearly audible murmur 2, 3
- Grade 3: Moderately loud murmur, without a palpable thrill 2, 1
- Grade 4: Loud murmur, associated with a palpable thrill 2, 3
- Grade 5: Very loud murmur that can be heard with the stethoscope partially off the chest; associated with a palpable thrill 2, 1
- Grade 6: Extremely loud murmur that can be heard with the stethoscope entirely off the chest; associated with a palpable thrill 2, 3
Diastolic Murmur Grading Scale (1-4)
- Grade 1: Very faint, barely audible murmur 1
- Grade 2: Quiet, but clearly audible murmur 1
- Grade 3: Moderately loud murmur 1
- Grade 4: Very loud murmur 1
Clinical Significance of Murmur Grades
- Grade 1-2 systolic murmurs in adults, particularly those that are midsystolic at the left sternal border, are often innocent or functional, especially when associated with normal intensity and splitting of S2 2
- Grade 3 or louder systolic murmurs typically warrant further evaluation with echocardiography, as they are more likely to represent organic heart disease 2, 3
- All diastolic murmurs, regardless of grade, virtually always represent pathological conditions and require further cardiac evaluation 2
- Murmur intensity correlates well with the severity of regurgitation in chronic organic aortic and mitral valve disease 4
Additional Characteristics That Influence Murmur Assessment
- Timing: Holosystolic (pansystolic), midsystolic (ejection), early systolic, late systolic, early diastolic, middiastolic, presystolic, or continuous 2
- Configuration: Crescendo, decrescendo, crescendo-decrescendo (diamond-shaped), or plateau 2, 1
- Location and radiation: Where the murmur is best heard and where it radiates 2, 1
- Pitch: High, medium, or low frequency 2, 1
- Duration: Short, medium, or long 2, 1
Dynamic Auscultation to Assess Murmurs
- Respiration: Right-sided murmurs generally increase with inspiration; left-sided murmurs are usually louder during expiration 2
- Valsalva maneuver: Most murmurs decrease in intensity, except hypertrophic cardiomyopathy (HCM) murmurs (become louder) and mitral valve prolapse (MVP) murmurs (become longer and often louder) 2
- Exercise: Murmurs caused by flow across normal or obstructed valves become louder with both isotonic and isometric exercise 2
- Positional changes: Standing typically diminishes most murmurs except HCM and MVP; squatting usually makes most murmurs louder except HCM and MVP 2
Clinical Approach Based on Murmur Grade
- Asymptomatic adults with grade 1-2/6 midsystolic murmurs and no other cardiac physical findings typically need no further workup 2, 5
- Echocardiography is recommended for asymptomatic patients with grade 3 or louder systolic murmurs 2
- All diastolic murmurs, continuous murmurs, holosystolic murmurs, and late systolic murmurs warrant echocardiographic evaluation regardless of intensity 2, 5
- Murmur grades can help predict severity of valvular regurgitation: grades ≥3 for aortic regurgitation and ≥4 for mitral regurgitation predict severe regurgitation in 71% and 91% of patients, respectively 4
Common Pitfalls in Murmur Assessment
- Systolic murmurs may be present in patients with aortic regurgitation, potentially masking the diastolic component 6
- Grade 2 for aortic regurgitation and grade 3 for mitral regurgitation have poor correlation with the actual degree of regurgitation 4
- Patient factors such as obesity, chest wall deformities, and lung disease can affect murmur intensity and audibility 2
- Relying solely on murmur intensity without considering other characteristics (timing, configuration, location) may lead to misdiagnosis 2, 1