Mitral valve regurgitation produces a high-pitched, blowing murmur that lasts throughout the heart’s contraction phase. Doctors describe it as a “whooshing” sound layered over the normal heartbeat, beginning with the first heart sound and continuing all the way to the second. It’s one of the more recognizable heart murmurs, and its specific qualities tell clinicians a lot about what’s happening inside the heart.
The Core Sound: Blowing and High-Pitched
The classic murmur of mitral regurgitation is called “holosystolic,” meaning it spans the entire period when the heart muscle is squeezing blood out. During that squeeze, the mitral valve should be sealed shut, but in regurgitation, blood leaks backward through the valve into the upper chamber. That backward jet of blood vibrating through the valve creates a continuous, blowing noise that sounds distinctly different from the normal “lub-dub.”
The sound is high-pitched, similar in frequency to the noise you’d hear blowing steadily across the opening of a bottle. It has a smooth, even quality rather than a harsh or rumbling one. In the most typical form (caused by rheumatic heart disease or chronic valve degeneration), the murmur maintains a steady, plateau-like intensity from start to finish. It begins right at the first heart sound and extends to, and sometimes slightly past, the second heart sound.
Where the Sound Is Loudest
The murmur is heard best at the apex of the heart, which sits at the fifth intercostal space on the left side of the chest, roughly in line with the middle of the collarbone. This is the spot where a stethoscope picks up the mitral valve most clearly.
One of the murmur’s signature features is radiation. The sound doesn’t stay put. It travels toward the left armpit and sometimes around to the area below the left shoulder blade. A clinician listening at the apex will often slide the stethoscope laterally to confirm this radiation pattern, which helps distinguish mitral regurgitation from other systolic murmurs that radiate in different directions (aortic stenosis, for example, sends its murmur up toward the neck).
How Acute and Chronic Cases Sound Different
Not all mitral regurgitation murmurs sound the same. When the valve fails suddenly, such as after a heart attack tears one of its supporting structures, the murmur takes on a decrescendo pattern. It starts loud and fades as systole progresses, sometimes cutting off before the second heart sound entirely. Acute regurgitation murmurs tend to be louder overall, often graded at 3 out of 6 or higher on the standard intensity scale. The intensity reflects the sudden, forceful jet of blood that the heart hasn’t had time to adapt to.
Chronic mitral regurgitation, by contrast, produces the classic steady, plateau-shaped murmur. The heart has gradually adjusted to the leak, and the murmur becomes a more predictable, even sound. In some chronic cases, the murmur gets slightly louder toward the end of systole, a pattern called late systolic accentuation.
The Click of Mitral Valve Prolapse
Mitral valve prolapse is one of the most common causes of mitral regurgitation, and it adds a distinctive extra sound. Before the murmur begins, there’s a brief, sharp mid-systolic click, like a snap. The click occurs when the floppy valve leaflets balloon backward and their supporting cords pull taut. If regurgitation follows, a late systolic murmur trails the click.
This click-murmur combination shifts with body position, which makes it unique among heart sounds. When you stand up or perform a Valsalva maneuver (bearing down as if straining), the click moves earlier in systole and the murmur lasts longer. Squatting does the opposite: the click shifts later and the murmur shortens. These predictable changes help clinicians confirm prolapse during a physical exam without needing imaging.
Extra Heart Sounds in Severe Cases
When mitral regurgitation becomes severe, a third heart sound often appears. Normal hearts produce two audible sounds per beat (“lub-dub”). A third heart sound, sometimes called an S3 gallop, adds a low-pitched thud shortly after the second sound, creating a rhythm that resembles the cadence of the word “Kentucky” (lub-dub-ta). It’s caused by blood rushing rapidly into a left ventricle that’s been stretched out by chronic volume overload.
The third heart sound is clinically significant because it signals that the heart is struggling. It reflects rapid filling of an enlarged ventricle and correlates with heart failure, a low pumping fraction, and worse outcomes. In extreme cases, this third sound can become so prominent that it’s not just audible but visible as a pulsation on the chest wall and palpable as a knock under the examiner’s hand. At that point, the second heart sound may become nearly inaudible because the heart’s output has dropped so low.
What Makes the Murmur Louder or Softer
The intensity of the murmur changes with anything that alters blood flow or pressure in the heart. One simple bedside test is the isometric handgrip: squeezing something tightly for 20 to 30 seconds raises the resistance that the left ventricle pumps against, which forces more blood backward through the leaky valve and makes the murmur louder. This maneuver helps clinicians confirm that a systolic murmur is coming from mitral regurgitation rather than another source.
Anything that increases blood volume in the heart, like lying flat or raising the legs, also tends to amplify the sound. Conversely, maneuvers that reduce blood volume in the ventricle, such as standing quickly, can make the murmur of standard mitral regurgitation softer (though, as noted above, they have the opposite effect in prolapse).
How Reliably Doctors Detect It by Ear
Auscultation, the formal term for listening with a stethoscope, is surprisingly sensitive for picking up mitral regurgitation. In a large multi-center study of over 4,300 patients, clinicians detected mitral regurgitation murmurs with about 90% sensitivity when compared against echocardiogram results. That’s comparable to detection rates for other valve problems like aortic stenosis (89%) and tricuspid regurgitation (90%). The stethoscope remains a powerful first screening tool, though echocardiography is the standard for confirming the diagnosis and measuring severity.