A systolic ejection murmur is a whooshing sound heard through a stethoscope during the phase when your heart is pumping blood out. It has a distinctive pattern: the sound builds in intensity, peaks in the middle, then fades before the next heartbeat. This crescendo-decrescendo shape is its hallmark, distinguishing it from other types of heart murmurs. In many cases, especially in children, teenagers, and pregnant women, it’s completely harmless. In others, it signals a valve problem or structural heart condition that needs monitoring or treatment.
How the Sound Is Produced
Your heart has four valves that open and close with each beat. During systole (the pumping phase), the aortic valve and the pulmonic valve open to let blood flow out of the heart into the body and lungs. When blood passes smoothly through a wide-open valve, it’s silent. But when something narrows that opening, or when blood is moving faster than usual, the flow becomes turbulent, like water rushing through a kinked hose. That turbulence vibrates the surrounding tissue and produces an audible sound.
The crescendo-decrescendo pattern reflects what’s happening in real time. As the heart contracts, blood accelerates through the narrowed or high-flow area, making the sound grow louder. At peak flow, the sound is loudest. Then as the heart finishes contracting, flow slows and the sound tapers off. The whole event takes a fraction of a second.
Innocent Murmurs vs. Pathological Ones
Not every systolic ejection murmur means something is wrong with your heart. Innocent (also called “functional” or “flow”) murmurs are extremely common and happen when blood moves through a structurally normal heart at higher-than-usual speed. Several everyday conditions can trigger this:
- Fever, which increases heart rate and blood flow
- Anemia, where the heart pumps harder to compensate for fewer oxygen-carrying red blood cells
- Pregnancy, when blood volume increases significantly
- Overactive thyroid, which revs up the cardiovascular system
- Exercise or physical activity
- Rapid growth during adolescence
These murmurs are typically soft, short, and disappear once the underlying condition resolves. A child with a fever might have a clearly audible murmur that’s completely gone at the next checkup. Innocent murmurs are generally graded low on the intensity scale (grade 1 or 2 out of 6), meaning they’re faint and require careful listening to detect.
Common Conditions That Cause Pathological Murmurs
Aortic Stenosis
The most well-known cause of a pathological systolic ejection murmur is aortic stenosis, where the aortic valve (the main exit valve from the heart) becomes stiff or narrowed. This is often caused by age-related calcium buildup on the valve leaflets, or by a congenital abnormality where the valve has two flaps instead of the usual three. The murmur is heard best at the upper right side of the breastbone (the second intercostal space) and often radiates upward into the neck along the carotid arteries.
One clinically useful detail: as aortic stenosis worsens, the peak of the murmur shifts later in the pumping phase. In mild stenosis, the sound peaks early. In severe stenosis, it peaks late. This timing shift gives a rough sense of severity even before imaging. The murmur also tends to grow louder with worsening stenosis, though in very advanced disease the heart may be too weak to generate a loud sound, so loudness alone is unreliable.
Pulmonic Stenosis
A narrowed pulmonic valve (the exit to the lungs) produces a similar crescendo-decrescendo murmur, but it’s loudest at the upper left side of the breastbone. This condition is less common in adults and is more often associated with congenital heart conditions.
Hypertrophic Cardiomyopathy
In this inherited condition, the heart muscle is abnormally thick, particularly the wall between the two lower chambers. During contraction, the thickened muscle can partially block blood flow out of the heart, creating a systolic ejection murmur heard between the left side of the breastbone and the apex of the heart (near the left nipple). This murmur behaves differently from aortic stenosis in response to certain physical maneuvers, which helps distinguish the two.
Atrial Septal Defect
A hole between the two upper chambers of the heart allows extra blood to flow into the right side, increasing flow across the pulmonic valve. This produces a soft systolic ejection murmur at the upper left chest. The telltale sign is a “fixed split” of the second heart sound, meaning the normal two-part closing sound of the valves stays evenly split regardless of breathing. This combination is characteristic enough that experienced listeners can suspect the diagnosis from the stethoscope alone.
How Murmurs Are Graded
Doctors rate murmur intensity on a six-point scale developed decades ago and still in universal use. Grade 1 is the faintest detectable sound, requiring concentration and a quiet room. Grade 2 is soft but immediately recognizable. Grade 3 is moderate. Grade 4 is loud and accompanied by a “thrill,” a vibration you can feel with your hand flat on the chest. Grade 5 is very loud, and Grade 6 is so loud it can be heard with the stethoscope lifted just off the skin.
Most innocent murmurs fall in the grade 1 to 2 range. A murmur of grade 3 or higher, or any murmur accompanied by a palpable thrill, generally warrants further evaluation. But grading is just one piece of the puzzle. The location, timing, shape, and response to body position all matter.
What Happens During Evaluation
If a murmur sounds like it could be more than innocent, the standard next step is an echocardiogram, essentially an ultrasound of the heart. This painless imaging test shows the valve anatomy, measures how fast blood is moving through each valve, and calculates the valve opening area.
For aortic stenosis specifically, three measurements determine severity. The peak blood velocity across the valve is normally under 2.5 meters per second. Mild stenosis ranges from 2.5 to 2.9, moderate from 3 to 3.9, and severe is 4 or above. The pressure difference (gradient) across the valve and the calculated valve opening area provide additional confirmation. A normal aortic valve opens to about 3 to 4 square centimeters. Severe stenosis means the opening has shrunk below 1 square centimeter, and very severe is 0.6 or smaller, which is associated with particularly poor outcomes if untreated.
For conditions like hypertrophic cardiomyopathy, echocardiography measures wall thickness, chamber size, and whether there’s obstruction during contraction. Current guidelines from the American Heart Association and American College of Cardiology recommend repeat echocardiograms every one to two years for people with confirmed hypertrophic cardiomyopathy, even if they feel fine, to track any changes over time.
Symptoms That Signal a Problem
Many people with pathological systolic ejection murmurs have no symptoms for years. The murmur is discovered incidentally during a routine physical. When symptoms do develop, they typically reflect the heart’s inability to pump blood effectively through the narrowed or obstructed area. The three classic warning signs are shortness of breath (especially with exertion), dizziness or lightheadedness, and fainting (syncope). Chest pain during physical activity can also occur, particularly with aortic stenosis.
The appearance of any of these symptoms in someone with a known murmur usually marks a turning point. Severe aortic stenosis, for example, can remain stable for years, but once symptoms begin, the outlook worsens significantly without intervention. That’s why regular monitoring matters even when you feel perfectly well.
Living With a Systolic Ejection Murmur
If your murmur has been identified as innocent, no treatment or follow-up is needed. It’s not a disease, and it won’t become one. Many people go their entire lives with an audible flow murmur that means nothing.
If the murmur is linked to a structural condition, the approach depends on severity. Mild valve narrowing might only require periodic monitoring with echocardiograms. For hypertrophic cardiomyopathy, the 2024 AHA/ACC guidelines have moved away from blanket exercise restrictions. Most patients are no longer universally restricted from vigorous activity or competitive sports. Instead, participation is evaluated annually on an individual basis, balancing benefits and risks. Practical advice like staying well hydrated and avoiding certain blood pressure medications that could worsen obstruction becomes part of daily management.
For severe or symptomatic valve disease, the primary treatment is valve replacement or repair, which has become increasingly less invasive over the past two decades. Many aortic valve replacements are now done through a catheter inserted in the leg rather than open-heart surgery, with shorter recovery times and fewer complications.