How is a Heart Murmur Diagnosed? 

A heart murmur is not a condition in itself, but rather a sound heard between heartbeats. While the typical heart sound is a clear ‘lub-dub’, a murmur sounds like a ‘whooshing’ or ‘swishing’ noise caused by turbulent blood flow within or near the heart. Finding out you have a heart murmur can be concerning, but many are harmless. However, because a murmur can sometimes indicate a problem with a heart valve or a structural defect, a formal diagnosis is essential. This article explains the step-by-step process UK healthcare professionals use to diagnose and categorise heart murmurs. 

What We’ll Discuss in This Article 

• The clinical definition of a heart murmur and how it is first identified. 

• The role of physical examination and the use of the stethoscope. 

• Key diagnostic tests, including echocardiograms and ECGs. 

• The difference between ‘innocent’ and ‘pathological’ murmurs. 

• How doctors determine the underlying cause of abnormal heart sounds. 

• When a heart murmur requires urgent medical investigation. 

How is a Heart Murmur First Identified? 

A heart murmur is typically first identified during a physical examination using a stethoscope, a process known as ‘auscultation’. The doctor listens to several areas of the chest to determine the murmur’s timing, pitch, and volume. While many murmurs are discovered during routine check-ups for unrelated issues, they may also be investigated if a patient reports symptoms like breathlessness or chest pain. 

During this initial assessment, the doctor is not just listening for the sound itself, but for specific characteristics that help differentiate a harmless sound from one that requires further testing. 

• Timing: Does the murmur happen when the heart is contracting (systolic) or relaxing (diastolic)? 

• Intensity: Doctors use a grading scale from 1 (very faint) to 6 (very loud). 

• Location: Where on the chest the sound is loudest helps identify which valve might be involved. 

• Radiation: Does the sound travel to the neck or the armpit? 

What are the Main Diagnostic Tests for Heart Murmurs? 

If a doctor hears a murmur that sounds ‘pathological’ (potentially abnormal), they will order further diagnostic tests. The ‘gold standard’ for diagnosis is an echocardiogram, an ultrasound scan that allows the doctor to see the heart’s structure and valves in motion. Other common tests include an Electrocardiogram (ECG) to check the heart rhythm and a chest X-ray to look at the heart’s size and shape. 

These tests provide a comprehensive picture of how the heart is functioning and whether the turbulent blood flow is caused by a structural issue. 

• Echocardiogram: Uses sound waves to create live images of the heart valves and chambers. 

• Electrocardiogram (ECG): Records the electrical activity of the heart to check for arrhythmias or strain. 

• Chest X-ray: Can show if the heart is enlarged or if there is fluid in the lungs. 

• Cardiac MRI: Used in complex cases to provide highly detailed 3D images of the heart’s anatomy. 

What Causes a Heart Murmur to be Detected? 

Heart murmurs are caused by turbulent blood flow, which can be triggered by a variety of factors. In many cases, the cause is ‘functional’, meaning the heart is healthy but blood is moving faster than usual due to pregnancy, fever, or anaemia. In other cases, the murmur is caused by structural issues such as ‘valve stenosis’ (narrowing) or ‘valve regurgitation’ (leaking). 

Valve Narrowing (Stenosis) 

When a heart valve becomes stiff or narrow, blood must be forced through a smaller opening. This creates turbulence, much like water moving through a narrowed pipe, which results in a harsh-sounding murmur. 

Leaky Valves (Regurgitation) 

If a valve does not close tightly, blood leaks backward into the chamber it just left. This backward flow creates a ‘whooshing’ sound that is often detected during the relaxation phase of the heartbeat. 

Congenital Defects 

Some murmurs are present from birth due to holes in the heart walls (such as atrial septal defects) or abnormally shaped valves. These are often detected during newborn or childhood physical examinations. 

What are the Triggers for Investigating a Murmur? 

While some murmurs are found by chance, certain clinical ‘triggers’ make a diagnostic investigation more urgent. If a murmur is accompanied by symptoms like sudden breathlessness, fainting during exercise, or chest tightness, it suggests the heart’s efficiency is being affected. Additionally, a new murmur appearing after a fever or a heart attack is a significant trigger for immediate testing. 

• Exertional Dyspnoea: Shortness of breath when performing simple tasks. 

• Syncope: Fainting or feeling very lightheaded, which may indicate a severely narrowed valve. 

• Cyanosis: A blue or grey tinge to the lips or nails, indicating poor oxygenation. 

• Unexplained Fatigue: Tiring much faster than usual without a clear cause. 

Differentiation: Innocent vs. Pathological Murmurs 

A crucial part of the diagnostic process is differentiating between an ‘innocent’ murmur and a ‘pathological’ one. Innocent murmurs are common in children and thin adults; they are simply the sound of blood moving through a normal, healthy heart. Pathological murmurs, however, are caused by a physical abnormality in the heart’s structure and require medical management. 

Feature	Innocent Murmur	Pathological Murmur
Cause	Normal blood flow (e.g., during exercise).	Structural defect (e.g., leaky valve).
Symptoms	No symptoms; the person is healthy.	Breathlessness, chest pain, or fatigue.
Timing	Almost always systolic (during contraction).	Can be systolic or diastolic.
Grade	Usually quiet (Grade 1 or 2).	Can be loud or have a ‘thrill’ (vibration).

Conclusion 

Diagnosing a heart murmur begins with a simple stethoscope examination and is confirmed through detailed imaging, such as an echocardiogram. While many murmurs are innocent and require no treatment, others serve as an important early warning sign of underlying valve disease or structural issues. If your doctor detects a murmur, they will use these diagnostic tools to ensure your heart is functioning safely and efficiently. 

If you experience severe, sudden, or worsening symptoms, such as intense chest pain, sudden breathlessness, or fainting, call 999 immediately. 

Authority Snapshot (E-E-A-T Block) 

This article was written and reviewed by Dr. Rebecca Fernandez, a UK-trained physician with extensive experience in cardiology, internal medicine, and emergency care. Drawing on her clinical background in managing acute cardiac cases and inpatient care, this guide provides a medically accurate overview of the diagnostic pathway for heart murmurs. Our goal is to provide clear, safe, and factual information based on NHS and NICE guidelines to help you understand the clinical assessment of heart sounds.