How are heart murmurs graded?

Grading of Heart Murmurs

Heart murmurs are traditionally graded on a scale of 1 through 6 based on their intensity, which is an essential component of cardiac auscultation assessment along with timing, configuration, location, radiation, pitch, and duration. 1

Grading Scale for Systolic Murmurs

The 6-point grading scale for systolic murmurs is as follows:

• Grade 1: Very faint, barely audible even with careful auscultation 1, 2
• Grade 2: Quiet but clearly audible 1, 2
• Grade 3: Moderately loud, without a thrill (palpable vibration) 1, 2
• Grade 4: Loud, associated with a thrill 1, 2
• Grade 5: Very loud, audible with stethoscope partly off the chest, associated with a thrill 1, 2
• Grade 6: Extremely loud, audible with stethoscope entirely off the chest, associated with a thrill 1, 2

Grading Scale for Diastolic Murmurs

Diastolic murmurs are typically graded on a 4-point scale:

• Grade 1: Very faint, barely audible 1
• Grade 2: Quiet but clearly audible 1
• Grade 3: Moderately loud 1
• Grade 4: Very loud 1

Clinical Significance of Murmur Grading

The intensity of a heart murmur often correlates with clinical significance:

• Grade 1-2 systolic murmurs are often innocent or physiological, especially in children and young adults 1, 2
• Grade 3 or louder systolic murmurs frequently indicate underlying cardiac pathology 2
• Diastolic murmurs of any grade virtually always represent pathological conditions and require further cardiac evaluation 1

Factors Affecting Murmur Intensity

Several factors can influence the intensity of a heart murmur:

• Blood flow rate through normal or abnormal orifices 1
• Pressure gradient between cardiac chambers 1
• Patient factors such as chest wall thickness 1
• Physiological states such as anemia, fever, pregnancy, or thyrotoxicosis 1, 2

Other Important Characteristics of Murmurs

While grading intensity is important, a comprehensive assessment should include:

• Timing in the cardiac cycle (systolic, diastolic, continuous) 1
• Configuration (crescendo, decrescendo, crescendo-decrescendo/diamond-shaped, plateau) 1
• Location and radiation pattern 1
• Response to dynamic maneuvers (Valsalva, respiration, position changes) 1

Clinical Approach to Murmur Assessment

• All diastolic murmurs require further evaluation regardless of grade 1
• Systolic murmurs grade 3 or higher generally warrant echocardiographic evaluation 2, 3
• Lower-grade systolic murmurs may require further evaluation if associated with:
  • Concerning symptoms (syncope, angina, heart failure) 1
  • Abnormal associated findings (fixed splitting of S2, absent S2, etc.) 1
  • High-risk patient populations (neonates, patients with genetic syndromes) 4

Common Pitfalls in Murmur Assessment

• Relying solely on murmur grade without considering other characteristics can lead to misdiagnosis 3
• Underestimating the significance of lower-grade murmurs in certain clinical contexts (e.g., severe AS with low cardiac output may produce only a grade 2 murmur) 1
• Over-investigating innocent murmurs, particularly in children 5, 4
• Failing to recognize that multiple cardiac lesions may be present simultaneously, altering the expected auscultatory findings 3