Heart murmur:
when it can be caused by a valve

Article written and reviewed by Dr Luca Moretti

A heart murmur is not a diagnosis. It is a sound that a doctor hears with a stethoscope when blood flows in a way that produces audible vibrations. It may be innocent, occur in temporary conditions that increase blood flow, or be a sign of heart valve disease.
To understand what it means, the clinical context and the characteristics of the murmur are needed. When the finding raises suspicion of structural heart disease, an echocardiogram is the main test used to determine whether a valve is narrowed, leaking or has other abnormalities.

Valvular heart diseases are one possible cause of a murmur, but not the only one. For this reason, it is not appropriate to try to establish the diagnosis independently based only on the statement “a murmur can be heard.”

What a murmur is and why it does not always mean disease

Normal blood flow through the heart produces sounds that mainly correspond to valve closure. When blood flow becomes faster, passes through a narrowed opening or flows backward through a valve that does not close properly, additional sounds called murmurs may occur.
There are also innocent or functional murmurs, in which the heart and valves are structurally normal. They may be promoted by conditions that increase flow velocity, such as fever, anemia, pregnancy or high cardiac output. Their significance therefore varies greatly according to age and context.

The doctor describes a murmur according to when it occurs in the cardiac cycle, where it is heard most clearly, the direction in which it radiates, its pitch and its intensity. These characteristics may suggest a particular lesion, but auscultation does not replace imaging when anatomy and severity need to be defined accurately.

Which valve diseases can cause a murmur

A narrowed valve accelerates blood flow through a reduced opening. This is what happens, for example, in aortic stenosis or mitral stenosis. A valve that does not close properly instead allows blood to flow backward, as occurs in mitral regurgitation or aortic regurgitation.
The type of murmur may suggest which valve is involved, but there are overlaps and individual variations. In addition, the presence of more than one valve lesion can make auscultation less straightforward.

An important point is that murmur intensity does not reliably measure severity. A very audible murmur does not necessarily mean severe disease and, in some conditions, an important lesion may produce a relatively soft murmur. Severity is established mainly by echocardiography together with integration of the clinical findings.

When a murmur requires an echocardiogram

The decision does not depend only on whether a murmur is present. The doctor considers whether it is new, whether its characteristics are compatible with a structural lesion, whether symptoms are present, whether there are electrocardiographic abnormalities or other findings on physical examination, and whether the person already has known heart disease.
A diastolic murmur in an adult is generally considered pathological and requires further evaluation. The significance of systolic murmurs, which are much more common, varies: some are innocent, while others suggest aortic stenosis, mitral regurgitation or other conditions.

A transthoracic echocardiogram makes it possible to examine valve structure, measure flow velocities and gradients, quantify any regurgitation and assess the effects on the heart chambers. Its purpose is not only to confirm that a valve is abnormal: it also helps distinguish a mild lesion from one that requires closer follow-up or treatment.

Which symptoms make a murmur more important to assess

A murmur associated with shortness of breath, reduced exercise capacity, chest pain, dizziness or fainting, persistent palpitations or edema warrants clinical assessment. This is not because these symptoms automatically prove valvular heart disease, but because they increase the likelihood that the auscultatory finding is clinically significant.
If a person with a known murmur suddenly develops marked breathing difficulty, faints or has significant chest pain, it is not appropriate simply to wait for the next scheduled follow-up.

In children and young adults, innocent murmurs are relatively common, whereas the likelihood of degenerative valve abnormalities increases with age. This does not mean that every murmur in an older adult corresponds to severe valvular heart disease, but it makes interpretation in the clinical context and, when indicated, by echocardiography particularly important.

Frequently asked questions about heart murmurs

Does a heart murmur mean that I have valvular heart disease?
No. A murmur may be innocent or functional. In other cases it may be produced by valvular stenosis or regurgitation.

How can you tell whether a murmur is pathological?
The characteristics of the murmur, age, symptoms, medical history and other findings are assessed. If structural heart disease is suspected, echocardiography clarifies the cause.

Does a loud murmur always indicate severe valvular heart disease?
No. Auscultatory intensity does not reliably correspond to lesion severity.

Is an echocardiogram always needed for a heart murmur?
Not in every situation. The need depends on the characteristics of the murmur and the context. A new or suspicious murmur, or one associated with symptoms, is more likely to require echocardiographic investigation.

Which symptoms associated with a murmur deserve attention?
Shortness of breath, reduced exercise tolerance, chest pain, dizziness or fainting, persistent palpitations and edema, especially if new or worsening.