A systolic murmur is an extra whooshing or swishing sound heard between the first and second heartbeats, during the phase when your heart is actively pumping blood. It’s one of the most common findings during a routine physical exam, and in many cases it’s completely harmless. Between one-third and three-quarters of children between ages 1 and 14 will have an innocent murmur at some point, and some carry it into adulthood without any problems. In other cases, a systolic murmur signals an underlying issue with a heart valve or the heart’s structure.
How the Sound Is Produced
Your heart makes two distinct sounds in each cycle. The first (S1) happens when the valves between the upper and lower chambers snap shut as the heart begins to contract. The second (S2) occurs when the valves leading to the lungs and the rest of the body close after the heart finishes pumping. A systolic murmur is any extra sound that occurs between S1 and S2.
The sound itself comes from turbulent blood flow. Normally, blood moves through the heart in smooth, orderly streams. When something disrupts that flow, whether it’s a narrowed valve, a leaking valve, or simply a high volume of blood moving quickly, the turbulence vibrates surrounding tissue and creates an audible murmur. Even conditions like anemia, where the blood is thinner than usual, can speed up flow enough to generate the sound.
Types of Systolic Murmurs
Systolic murmurs are grouped by when exactly the sound falls within that pumping phase.
- Midsystolic (ejection) murmurs begin just after S1 and stop just before S2, so both normal heart sounds are still clearly audible. These are tied to blood being pushed forward through a narrowed or stiffened valve. The classic example is aortic stenosis, where the valve leading to the body’s main artery has become too narrow. The sound typically starts soft, swells louder in the middle, then fades, producing a diamond-shaped pattern.
- Holosystolic (pansystolic) murmurs stretch from the moment S1 occurs all the way to S2, making the normal heart sounds hard to hear. These usually mean blood is leaking backward through a valve that should be sealed shut. Mitral regurgitation is the most common cause: during contraction, blood slips backward from the lower left chamber into the upper left chamber instead of flowing out to the body.
- Late systolic murmurs begin well after S1 and may or may not reach S2. Mitral valve prolapse, where one of the valve’s flaps bulges and allows a small leak partway through contraction, is a typical cause.
Common Causes
Valve Narrowing (Stenosis)
When a heart valve stiffens or narrows, blood has to squeeze through a smaller opening at higher speed, creating turbulence. Aortic stenosis produces a high-pitched, crescendo-decrescendo murmur best heard on the upper right side of the chest that often radiates up toward the neck. Pulmonic stenosis creates a similar sound on the upper left side, though it doesn’t travel as widely.
Valve Leaking (Regurgitation)
If a valve doesn’t seal completely when the heart contracts, blood flows backward. Mitral regurgitation is the most common regurgitant murmur. There are several variations: some result from damage caused by infection or rheumatic disease, others from stretching of the muscles that anchor the valve, and others from a sudden tear or rupture. Tricuspid regurgitation, on the right side of the heart, works the same way but is less common.
Structural Problems
A hole between the heart’s lower chambers (ventricular septal defect) lets blood cross from the high-pressure left side to the lower-pressure right side during contraction, producing a holosystolic murmur. In newborns, a vessel called the ductus arteriosus sometimes fails to close after birth, creating abnormal flow patterns. Thickening of the heart muscle itself, a condition called hypertrophic obstructive cardiomyopathy, can partially block blood leaving the heart and generate a midsystolic murmur.
Innocent vs. Concerning Murmurs
Innocent murmurs are extremely common and don’t reflect any structural problem with the heart. They tend to share a few features: they’re soft (graded low on the 1-to-6 loudness scale), low-pitched, and have a blowing or musical quality. They also change noticeably with body position. A type called a “Still’s murmur” in children is loudest when lying down and quieter when sitting up. A “venous hum,” another harmless sound, does the opposite and often disappears entirely when lying flat.
Certain characteristics raise concern. Any murmur graded louder than 3 out of 6 warrants further evaluation. High-pitched murmurs are more likely to be pathological. A murmur that doesn’t change at all with position changes or physical maneuvers tends to point toward a valve problem rather than an innocent finding. And any murmur heard during the filling phase of the heartbeat (diastolic) rather than the pumping phase is considered abnormal until proven otherwise.
Symptoms That Signal a Problem
Many systolic murmurs produce no symptoms at all and are discovered incidentally during a routine checkup. When a murmur is tied to significant heart disease, symptoms typically develop gradually and reflect the heart’s declining ability to pump efficiently. The most common warning signs are shortness of breath (especially with exertion), chest pain, dizziness, and fainting.
In children, the key red flag is a noticeable drop in activity level or an inability to keep up with peers during exercise. In adults, worsening exercise tolerance that progresses over weeks or months points toward a valve or structural problem rather than simple deconditioning. Fainting during physical activity is particularly concerning and should always be evaluated promptly.
How Systolic Murmurs Are Evaluated
The evaluation starts with a stethoscope. A clinician listens for several features: how loud the murmur is on the 1-to-6 scale, where on the chest it’s heard most clearly, whether it’s high or low pitched, and whether the sound changes when you shift from lying down to sitting or standing, or when you bear down as if straining. Where the sound travels matters too. A murmur that radiates to the neck suggests aortic stenosis, while one that spreads toward the left armpit points toward mitral regurgitation.
If the murmur sounds potentially concerning, the primary tool for determining its cause is an echocardiogram, an ultrasound of the heart. This produces real-time images of the valves opening and closing and shows exactly how blood is flowing through each chamber. It can identify narrowed valves, leaking valves, holes between chambers, and thickened heart muscle. A chest X-ray may also be ordered to check whether the heart appears enlarged, which can be a sign that it has been working harder than normal for an extended period.
Family history plays a role in the workup as well. A family background of heart defects, genetic disorders, or sudden cardiac events can shift how aggressively a murmur is investigated, even if it initially sounds benign.