A grade II heart murmur is a faint but easily audible sound heard through a stethoscope during a heartbeat. On the six-point Levine scale used to rate murmur intensity, it sits near the quieter end, one step above the faintest murmurs that only specialists can detect. Grade II murmurs are among the most commonly identified murmurs in routine checkups, and the majority turn out to be harmless.
How the Grading Scale Works
Heart murmurs are graded from 1 to 6 based on how loud they sound through a stethoscope. A grade I murmur is so quiet that only an expert listener can pick it up under ideal conditions. A grade II murmur is louder: faint, but audible to any trained clinician listening in a quiet room. A grade III murmur is easily heard without straining but still doesn’t produce a vibration you can feel on the chest wall (called a “thrill”). Grades IV through VI are progressively louder and do produce that palpable vibration, with a grade VI murmur audible even with the stethoscope slightly lifted off the skin.
The grade alone doesn’t tell the full story. Doctors also note when the murmur occurs in the heartbeat cycle (during contraction or between beats), where on the chest it’s loudest, and whether it changes with body position or breathing. All of these details together help determine whether the murmur reflects a structural heart problem or is simply the sound of normal blood flow.
Why Most Grade II Murmurs Are Harmless
A murmur graded at II or below is far less likely to signal a heart problem than a louder one. As a general clinical rule, murmurs rated grade III or louder raise more concern for underlying structural issues. Grade I and II murmurs frequently fall into the “innocent” or “functional” category, meaning they’re caused by blood flowing normally through the heart rather than by a defective valve or abnormal opening.
The timing matters, though. A grade II murmur heard during the heart’s contraction phase (systolic) is often a choice between something completely benign and a minor structural variation like a small hole between the upper chambers of the heart. Many systolic murmurs at this intensity need no treatment at all. Diastolic murmurs, heard between contractions, are a different story. With one exception (a harmless humming sound caused by blood flow in the neck veins), diastolic murmurs at any grade are considered abnormal and typically need further evaluation.
Grade II Murmurs in Children
Innocent heart murmurs are remarkably common in kids. Estimates range from 20% to 80% of children having one at some point, depending on the study and how carefully examiners listen. Two of the most frequently detected innocent murmurs in children, Still’s murmur and venous hum, are typically graded at I or II on the Levine scale.
Still’s murmur produces a characteristic musical or vibratory quality, most often heard in children between ages 3 and 6. It tends to disappear by adolescence as the chest grows and the heart’s position shifts. A venous hum, which sounds like a continuous low-pitched humming, also appears in the same age range and is caused by blood flowing through the large veins near the collarbone. It typically goes away when the child lies down or turns their head, which is one of the quickest ways to confirm it’s harmless. Both of these murmurs resolve on their own as a child transitions into adulthood, and neither requires any restriction on physical activity.
What Makes a Grade II Murmur Concerning
While most grade II murmurs are benign, certain features shift the picture. A grade II murmur is more likely to warrant further investigation if it:
- Occurs during diastole (between heartbeats rather than during contraction)
- Gets louder when standing, which is the opposite of what innocent murmurs typically do
- Accompanies abnormal heart sounds, such as an unusual second heart sound that doesn’t split normally, or an extra clicking sound
- Appears alongside symptoms like shortness of breath, poor weight gain in infants, chest pain, or fainting
When none of those red flags are present, and the first and second heart sounds are normal, a grade II systolic murmur in an otherwise healthy person is rarely anything to worry about. Many doctors will simply monitor it over time without ordering additional tests.
How a Grade II Murmur Is Evaluated
The initial evaluation is straightforward: a doctor listens to the heart in a quiet room, noting the murmur’s loudness, timing, location, and pitch. They’ll often ask you (or your child) to change positions, sitting up, lying down, or standing, because innocent murmurs frequently change or disappear with position changes. A murmur that vanishes when lying flat, for example, strongly suggests a venous hum rather than a structural problem.
If the physical exam raises any questions, the next step is usually an echocardiogram, which is an ultrasound of the heart. This painless imaging test shows the heart’s valves and chambers in real time and can definitively confirm whether a murmur is caused by an anatomical issue or is simply the sound of healthy blood flow. For a grade II murmur with all the hallmarks of an innocent murmur, many clinicians feel confident making that call based on the stethoscope exam alone, particularly in children.