A heart murmur itself isn’t a single image on an echocardiogram. It’s the visual evidence of turbulent or abnormal blood flow, and it shows up in several distinct ways depending on what’s causing it. The most recognizable sign is a burst of color on the screen, produced by a mode called color Doppler, which maps the speed and direction of blood moving through your heart in real time. Normal flow appears as smooth bands of red or blue. Abnormal flow tied to a murmur shows up as a mosaic of greens, yellows, and mixed colors, indicating turbulence.
But the color splash is only one piece of the picture. An echocardiogram also reveals the structural problem behind the murmur, whether that’s a leaky valve, a narrowed valve, or a hole in the heart wall, and each of these looks different on screen.
Color Doppler: The Turbulent Jet
Color Doppler is usually the first thing that makes a murmur visible. The ultrasound machine assigns colors to blood based on its direction: red for flow toward the probe, blue for flow away from it. When blood moves smoothly, the color is uniform. When it’s forced through a narrowed opening or leaks backward through a faulty valve, the flow becomes chaotic, and the screen lights up with a swirling patch of mixed colors often called a “jet.”
For a leaking valve (regurgitation), this jet appears on the wrong side of the valve. If your mitral valve leaks, for example, a colored jet sprays backward into the left atrium during each heartbeat. The jet can be central, fanning out in a cone shape, or eccentric, hugging the wall of the chamber if it’s deflected by valve anatomy. Eccentric jets are harder to measure accurately because they can appear smaller than they really are.
For a narrowed valve (stenosis), the jet shoots forward through the tight opening, creating a narrow, high-velocity stream on the downstream side. A structural hole, like a ventricular septal defect, produces a jet of blood crossing from one chamber to another, visible as a streak of color punching through the wall between the ventricles.
Spectral Doppler: The Velocity Graph
Color Doppler shows where turbulence is happening. Spectral Doppler measures how fast the blood is moving and displays it as a graph over time, with each heartbeat producing a characteristic waveform shape. This is where clinicians can tell a mild murmur from a severe one.
In continuous-wave Doppler, the machine captures the peak velocity of blood along a single line through the heart. A normal aortic valve lets blood pass at roughly 1 to 1.5 meters per second. A severely narrowed aortic valve forces blood through at 4 meters per second or more, producing a tall, dense waveform on the graph. The shape of the waveform matters too. A gradually peaking signal that crests late suggests more severe obstruction, while an early peak suggests milder narrowing.
For regurgitation, spectral Doppler picks up the high-velocity backflow signal and displays it on the opposite side of the baseline from normal flow, making it easy to spot. In some cases, the Doppler signal reveals parallel bands called harmonics, which correspond to the “musical” quality some murmurs have when heard through a stethoscope. These harmonics are produced by a vibrating structure, such as a valve leaflet fluttering in the abnormal flow.
What Valve Problems Look Like
Beyond the flow patterns, the echocardiogram shows the valve itself in grayscale ultrasound, and the structural changes are often striking.
A stenotic aortic valve typically appears thickened and bright white on the screen, reflecting calcium deposits that have built up over years. Normal valve leaflets are thin and open wide with each heartbeat. Calcified leaflets are stiff and barely move, opening only partway and creating a narrow slit instead of a wide circle. In a short-axis view (looking down at the valve from above), the opening may look like a small irregular hole rather than a full triangle. Bicuspid aortic valves, which have two leaflets instead of three, show an asymmetric closure line and an elliptical opening rather than a round one, along with a characteristic doming shape in the long-axis view.
A regurgitant mitral valve often looks structurally different too. The leaflets may prolapse, meaning they bow backward into the left atrium like a parachute during each contraction, or they may fail to close completely, leaving a visible gap. The echocardiographer measures the “vena contracta,” which is the narrowest width of the leaking jet right at the point where it passes through the valve gap. This measurement is relatively quick and doesn’t depend much on blood pressure at the time of the scan, though it’s most reliable when the jet is central rather than eccentric.
Holes in the Heart Wall
Septal defects, or holes between heart chambers, are another common source of murmurs. On a standard grayscale image, a ventricular septal defect may appear as a visible break or dropout in the wall between the left and right ventricles. Color Doppler confirms it by showing blood flow crossing through the hole, typically as a high-velocity jet from the higher-pressure left ventricle into the right. Small defects can be surprisingly hard to see on the grayscale image alone, so the color Doppler jet is often what clinches the diagnosis.
Chamber Enlargement and Secondary Changes
A murmur that has been present for months or years often leaves a footprint on the heart’s overall shape, and this is clearly visible on the echocardiogram. When a valve leaks significantly, the chambers receiving the extra blood volume gradually stretch. Chronic mitral regurgitation, for instance, causes the left atrium to balloon outward, sometimes growing to several times its normal size. The left ventricle may also dilate as it works harder to compensate.
Stenosis produces a different pattern. A narrowed aortic valve forces the left ventricle to pump against high resistance, so the heart muscle thickens instead of stretching. On the echocardiogram, the ventricular walls appear noticeably bulkier than normal. These secondary changes help the clinician gauge how long the problem has been developing and how much strain it’s placing on the heart, even before looking at the jet itself.
Standard vs. Transesophageal Imaging
Most echocardiograms are transthoracic, meaning the ultrasound probe is pressed against the outside of your chest. This is painless and gives a good view for most murmur evaluations. In some cases, though, the image quality is limited by body size, lung tissue, or the location of the abnormality.
A transesophageal echocardiogram places a small ultrasound probe into the esophagus, directly behind the heart, which eliminates interference from ribs and lungs. This approach is superior for detecting small masses, vegetations (clumps of infection on a valve), and subtle structural defects. It can reveal findings missed entirely on the standard chest-wall approach, making it especially useful when a murmur’s cause remains unclear after the initial scan or when the stakes of missing a diagnosis are high, such as suspected endocarditis.
Putting It All Together
No single image defines a heart murmur on an echocardiogram. The diagnosis comes from layering multiple views: the grayscale anatomy showing valve structure and chamber size, the color Doppler map revealing where blood is flowing abnormally, and the spectral Doppler graph measuring how fast and in what pattern that blood is moving. A mild murmur might show nothing more than a thin wisp of color at a valve with otherwise normal anatomy. A severe one can transform the entire picture, with a large turbulent jet, visibly damaged valve leaflets, and chambers that have remodeled under the strain. The combination of these findings is what turns a sound heard through a stethoscope into a precise structural diagnosis.