Are heart murmurs always linked to CHD?Â
No, heart murmurs are not always linked to congenital heart disease (CHD). In fact, many heart murmurs heard in children are what doctors call innocent or functional murmurs. These are simply the sounds of blood moving through a completely normal, healthy heart. While a heart murmur can sometimes be the first sign of a structural defect, many children and even some adults have murmurs that have no impact on their health or life expectancy.
What We will cover in this ArticleÂ
- The clinical definition of a heart murmurÂ
- The difference between innocent and pathological murmursÂ
- How doctors use the grading system to assess heart soundsÂ
- Common causes of murmurs that are not related to CHDÂ
- When a heart murmur requires further investigationÂ
- Diagnostic steps to rule out structural heart defectsÂ
What is a Heart Murmur?Â
A heart murmur is an extra or unusual sound heard during a heartbeat, typically described as a swishing or whistling noise. It is caused by turbulent blood flow in or near the heart. When a doctor listens to a heart with a stethoscope, they are usually listening for the two distinct sounds of the heart valves closing (often described as lub-dub). A murmur occurs when there is additional noise between or during these sounds.
It is important to understand that a murmur is a physical finding, not a disease. It is a sign that prompts a doctor to look closer at the heart’s anatomy and function.
Innocent vs. Pathological MurmursÂ
Cardiologists in the NHS categorise murmurs into two main groups to determine the level of concern and the necessity of follow-up tests.
Innocent Murmurs (Functional)Â
Innocent murmurs are extremely common in childhood, with some studies suggesting that up to 50% of healthy children will have one at some point. These murmurs occur because a child’s heart is close to the chest wall, and their blood flows relatively quickly.
- Characteristics: They are usually quiet, change with the child’s position, and often become louder if the child has a fever or is excited.Â
- Impact:Â There is no structural problem, no symptoms, and no treatment is needed.Â
Pathological Murmurs (Structural)Â
A pathological murmur is one caused by a structural abnormality in the heart, which is where the link to CHD exists.
- Characteristics:Â These murmurs are often louder, have a specific harsh quality, and do not change with position.Â
- Causes:Â They are caused by issues such as a hole in the heart (VSD), a narrowed valve (stenosis), or a leaky valve (regurgitation).Â
How Doctors Grade MurmursÂ
To communicate the intensity of a murmur, clinicians use a grading scale from 1 to 6. This helps determine how much turbulence is present.
| Grade | Description | Clinical Significance |
| Grade 1 | Very faint; only heard with great effort | Almost always innocent |
| Grade 2 | Soft, but easily heard with a stethoscope | Usually innocent |
| Grade 3 | Moderately loud, but no physical vibration | May require investigation |
| Grade 4 | Loud and associated with a ‘thrill’ (vibration) | Likely pathological |
| Grade 5 | Very loud; can be heard with stethoscope barely touching | Always pathological |
| Grade 6 | Extremely loud; heard without the stethoscope touching | Always pathological |
Causes of Murmurs Not Related to CHDÂ
A murmur can appear in a perfectly formed heart due to physiological changes that increase blood flow speed:
- Fever:Â When the body temperature rises, the heart beats faster and more forcefully.Â
- Anemia:Â A lack of red blood cells makes the blood thinner, which can cause turbulent flow sounds.Â
- Hyperthyroidism:Â An overactive thyroid speeds up the heart rate.Â
- Growth spurts: Rapid changes in a child’s body can temporarily change how heart sounds are conducted.Â
To Summarise
While heart murmurs are a primary way that CHD is discovered, they are not always linked to a defect. Most murmurs in children are innocent sounds made by a healthy heart. However, because a murmur is the most common outward sign of a structural heart problem, doctors will carefully assess the sound’s intensity and quality, along with the child’s overall health, to decide if further tests like an echocardiogram are necessary.
If you experience severe, sudden, or worsening symptoms such as your child fainting or having a blue tinge to their skin during activity, call 999 immediately.
Can an adult develop an innocent heart murmur?Â
Yes, thin adults or pregnant women often develop innocent murmurs because their heart is closer to the chest wall or their blood volume has increased.Â
Do innocent murmurs ever go away?Â
Yes, most children ‘outgrow’ innocent murmurs as their chest wall thickens and their heart rate slows down as they reach adolescence.Â
Can a doctor tell if a murmur is innocent just by listening?Â
Often, yes. Experienced doctors can identify the specific musical or vibratory quality of an innocent murmur. However, if there is any doubt, they will order an ultrasound.Â
Will a heart murmur affect my child’s ability to play sports?Â
If the murmur is innocent, there are no restrictions at all. If it is linked to CHD, the cardiologist will provide a specific activity plan based on the defect.Â
Does a loud murmur mean a more serious defect?Â
Not necessarily. Sometimes a very small hole in the heart makes a very loud, high-pitched noise, while a larger, more serious hole can be quieter.Â
Should I be worried if my doctor finds a murmur during a fever?Â
Generally no. It is very common for murmurs to appear or get louder during a fever. The doctor will usually want to listen again once the child is well.Â
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Authority Snapshot (E-E-A-T Block)
This article was reviewed by Dr. Stefan Petrov, a UK-trained physician with experience in general medicine, surgery, and emergency care. Dr. Petrov has performed countless physical examinations and diagnostic assessments in both hospital and primary care settings. His expertise ensures this guide to heart murmurs follows the 2026 NHS and NICE clinical safety standards.
