What Are Heart Murmurs?
Heart murmurs are extra sounds heard during your heartbeat, created when blood flows in a turbulent (swirly) way instead of smoothly through your heart—like the difference between water flowing gently from a faucet versus spraying out forcefully. 1
How Murmurs Are Made
Your heart makes murmur sounds through three main ways: 1
- Fast blood flow through normal or abnormal openings (like turning up the water pressure)
- Forward flow through a narrowed or irregular opening into a widened blood vessel or heart chamber (like squeezing a garden hose to make water spray farther)
- Backward or leaky flow through a valve that doesn't close properly (like a door that won't shut all the way)
Are Murmurs Dangerous?
Most murmurs are completely harmless—especially the ones heard in children and young adults. 1 Think of these "innocent" murmurs like hearing the sound of blood whooshing through your heart when everything is working perfectly fine. 1
However, some murmurs signal actual heart problems: 1
- Diastolic murmurs (sounds between heartbeats) are virtually always abnormal and need a heart doctor's evaluation 1
- Continuous murmurs usually need checking, except for two innocent types: venous hums (blood flowing through neck veins) and mammary souffles (blood flow in breast tissue during pregnancy or breastfeeding) 1
What Causes Innocent Murmurs?
Harmless murmurs commonly occur when: 1
- Your heart pumps faster than usual (during pregnancy, with thyroid problems, anemia, or exercise)
- You're a child or young adult with a thin chest wall that transmits sound easily
- Blood ejects normally but makes audible turbulence in the outflow areas
Most innocent murmurs in children and young adults are "midsystolic" (heard during the middle of the heartbeat) and come from the aortic or pulmonic outflow areas. 1
When Should You Worry?
Red flags that suggest a murmur needs further evaluation include: 2
- A harsh-sounding murmur
- Grade 3 or louder intensity (on a 1-6 scale)
- Abnormal second heart sound
- A clicking sound with the murmur
- Murmur that gets louder when standing up
- Any symptoms like shortness of breath, chest pain, or fainting
If your doctor cannot confidently identify your murmur as innocent, you need an echocardiogram (heart ultrasound) to see the actual heart structures and blood flow. 1, 2 This test provides the definitive answer about whether your heart is structurally normal. 1
The Bottom Line
Heart murmurs are extremely common—present in up to 80% of school children and 52% of adults—and the vast majority are completely benign findings that require no treatment. 3, 4 The key is distinguishing the innocent "background noise" from sounds that indicate actual valve problems or structural heart abnormalities. 1