From the Guidelines
Murmur grades range from 1 to 6, providing a standardized way to describe heart murmur intensity, with Grade 1 being very faint and Grade 6 being extremely loud. The grading system is as follows:
- Grade 1 murmurs are very faint, barely audible even with careful auscultation
- Grade 2 murmurs are quiet but can be heard immediately
- Grade 3 murmurs are moderately loud without a thrill (vibration)
- Grade 4 murmurs are loud and accompanied by a palpable thrill
- Grade 5 murmurs are very loud with a thrill and can be heard with the stethoscope partially off the chest
- Grade 6 murmurs are extremely loud and can be heard with the stethoscope entirely off the chest 1. This grading system helps clinicians communicate murmur severity and track changes over time. When documenting murmurs, it's essential to also note:
- Timing (systolic/diastolic)
- Location
- Radiation
- Quality
- Whether they change with respiration or position The grade alone doesn't necessarily indicate disease severity, as some serious conditions may present with soft murmurs while some benign conditions can produce louder sounds. Clinical correlation with other findings and possibly imaging studies is essential for proper diagnosis and management, as recommended by the American College of Cardiology/American Heart Association guidelines 1.
From the Research
Grades of Heart Murmurs
- The grades of heart murmurs are typically rated on a scale of 1 to 6 grades of intensity 2
- A grade 1 or 2 murmur is often considered functional and may disappear when the underlying cause is controlled, whereas a grade 3 or 4 murmur is more likely to be associated with organic heart disease or anemia 2
- Some studies suggest that murmurs can be classified as absent, soft, or loud 3
- The murmur grade is a quantitative measure of the murmur intensity and is strongly correlated with the patient's clinical condition 3
Murmur Grading Schemes
- Various clinicians have proposed grading schemes to differentiate pathological and physiological murmurs or different degrees of pathology 4
- The current, commonly used murmur grading scheme has been adapted by veterinary cardiologists and has been used for over 50 years, but its clinical utility has only recently been examined 4
- Some studies suggest that a simpler, more intuitive grading scheme might achieve the same desired outcome as the more complex scheme, potentially with less confusion 4
Clinical Significance of Murmur Grades
- A loud systolic murmur does not necessarily indicate a bad prognosis or even serious heart disease 2
- The grade of the murmur can be useful in the diagnosis and prognosis of heart disease 2
- Red flags that increase the likelihood of a pathologic murmur include a holosystolic or diastolic murmur, grade 3 or higher murmur, harsh quality, an abnormal S2, maximal murmur intensity at the upper left sternal border, a systolic click, or increased intensity when the patient stands 5