A dog coughing after being diagnosed with a heart murmur can understandably make you wonder whether the two problems are connected.
Noticeable signs include a dry or persistent cough, coughing at night or after activity, or a change in a dog’s breathing.
The connection depends on what is causing the murmur, how significant any underlying heart disease is, and what other symptoms your dog has.
A heart murmur can be harmless in some dogs, while in others it can indicate structural heart disease.
A dog’s age, breed, medical history, breathing pattern, activity level, and progression of symptoms all matter when determining what the cough means.
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Dog Coughing Due to Heart Murmur: Why It Happens
A dog may be coughing due to a heart murmur when the murmur is caused by underlying heart disease that has affected the heart’s function or contributed to changes in the lungs.
In some dogs with significant heart disease, increased pressure or congestion associated with the heart can contribute to coughing or faster breathing.
However, the heart murmur itself is not necessarily what causes the cough. A murmur is an abnormal sound heard when blood flows through the heart, and some murmurs occur without significant heart disease.
Dogs with a murmur can also develop respiratory problems unrelated to the heart.
Dog Coughing Due to Heart Murmur: Common Causes
Heart disease causing respiratory changes
Some heart conditions can eventually affect circulation between the heart and lungs. When heart function becomes compromised, pressure can build up within the pulmonary circulation and contribute to fluid accumulation in the lungs.
A dog with clinically significant heart disease may develop coughing along with faster breathing, reduced stamina, difficulty exercising, or other changes in normal behavior.
Whether this is happening depends on the underlying cardiac diagnosis rather than the presence of a murmur alone.
Related: Understanding Dog Coughing Due to Enlarged Heart
Mitral valve disease
Mitral valve disease is a common cause of heart murmurs in dogs, particularly in older small-breed dogs.
As the valve becomes abnormal, blood can leak backward through the valve, producing a murmur.
In dogs that develop significant progression of the disease, heart enlargement and increased pressure within the circulation can eventually contribute to respiratory signs.
A cough in a dog with a known mitral valve problem therefore deserves attention, but coughing does not automatically mean the heart disease has progressed to heart failure.
Dilated cardiomyopathy
Dilated cardiomyopathy causes the heart muscle to become weakened and the heart chambers to enlarge.
Dogs with significant disease may develop exercise intolerance, weakness, coughing, increased breathing rate, or difficulty breathing. Some may also develop abnormal heart rhythms.
A murmur may or may not be prominent depending on the individual dog and the nature of the cardiac disease.
Related: Dog coughing up phlegm (Causes and when to worry)
Congenital heart disease
Some puppies and younger dogs have heart abnormalities present from birth that produce a murmur.
Certain congenital defects can eventually affect circulation enough to cause exercise intolerance, respiratory changes, weakness, or other symptoms.
Other murmurs in young dogs may be innocent and disappear as the puppy matures.
A puppy or young dog with a persistent murmur and coughing should therefore be assessed rather than assuming that the cough is unrelated or that the murmur is automatically serious.
Pulmonary hypertension
Pulmonary hypertension involves increased pressure in the blood vessels supplying the lungs.
It can occur as a consequence of several underlying heart, lung, or other diseases. Affected dogs may develop coughing, faster breathing, exercise intolerance, weakness, or episodes of collapse.
If a dog with a murmur develops new respiratory symptoms, pulmonary hypertension may be one of the conditions a veterinarian considers depending on the overall examination.
Heart enlargement
Certain heart diseases can cause the heart to become enlarged.
An enlarged heart may contribute to respiratory symptoms in some dogs, although coughing is not proof that heart enlargement is present.
Chest X-rays and cardiac imaging can help determine whether the heart is enlarged and whether there are signs of changes affecting the lungs.
This is one reason a new cough in a dog with a murmur may warrant further investigation.
Respiratory disease unrelated to the murmur
A dog with a heart murmur can develop a completely separate respiratory condition.
Kennel cough, chronic bronchitis, tracheal collapse, pneumonia, airway irritation, and other respiratory problems can all cause coughing.
The fact that a murmur is present does not automatically make the heart the source of every cough.
This distinction is especially important in dogs with mild or previously stable murmurs.
Tracheal collapse
Tracheal collapse can cause a persistent, dry, harsh cough, particularly in some small-breed dogs.
The cough may become worse with excitement, exercise, heat, or pressure around the neck. A dog may have both tracheal collapse and a heart murmur, with the airway condition being responsible for the cough.
A veterinarian may need to investigate both possibilities rather than assuming that the murmur explains the respiratory symptoms.
Chronic bronchitis
Chronic bronchitis can cause a persistent cough even when a dog’s heart is functioning normally.
Some dogs with chronic airway inflammation remain active and maintain a normal appetite, while others develop reduced exercise tolerance or increased respiratory effort.
If a dog with a murmur has been coughing for a prolonged period without other evidence of worsening heart disease, a respiratory cause may need to be investigated.
Respiratory infection
A respiratory infection can cause coughing in a dog that happens to have a heart murmur.
Kennel cough and other respiratory infections may produce frequent coughing, gagging, sneezing, or nasal discharge. Some dogs remain bright and continue eating normally.
A sudden onset of coughing after contact with other dogs may therefore point toward a respiratory illness rather than progression of the underlying heart condition.
Related: Dog coughing up blood (Causes and treatment)
Dog Coughing With a Heart Murmur but Acting Normal
A dog with a heart murmur may cough while still eating, playing, and behaving normally.
Acting normal is reassuring, but it does not determine whether the cough is cardiac or respiratory. Some heart conditions and airway diseases can produce relatively mild signs initially.
If the cough is new, persistent, becoming more frequent, or occurring alongside changes in exercise tolerance or breathing, it is worth having your veterinarian reassess the dog.
Dog Coughing at Night With a Heart Murmur
Nighttime coughing in a dog with a heart murmur deserves particular attention because persistent coughing while resting can occur with some cardiovascular and respiratory conditions.
However, nighttime coughing is not specific to heart disease. Chronic airway disease, respiratory infections, and other conditions can also cause a dog to cough more noticeably at night.
If your dog repeatedly wakes up coughing or seems unable to rest comfortably because of breathing problems, veterinary assessment is appropriate.
Dog Coughing After Exercise With a Heart Murmur
Coughing after exercise can provide an important clue when a dog has a known heart murmur.
A dog with significant cardiovascular disease may have reduced exercise tolerance or develop faster breathing and weakness with activity. Respiratory conditions can produce a similar pattern, however.
Pay attention to whether your dog is tiring sooner than usual, stopping during walks, breathing unusually hard, or taking longer to recover. These changes should be reported to your veterinarian.
Does Every Heart Murmur Cause Coughing?
No. A heart murmur does not automatically cause coughing.
A murmur describes an abnormal sound created by blood flow through the heart. It does not, by itself, tell you how severe the underlying problem is or whether the heart is causing respiratory symptoms.
Some murmurs are associated with significant structural heart disease, while others can be innocent or relatively mild. A dog with a murmur can also develop an unrelated cough.
Determining whether the heart is involved requires looking at the dog’s examination findings and, when appropriate, performing cardiac or respiratory testing.
Related: Dog hacking cough and congestive heart failure (Why it happens)
When to Call or Visit the Vet
A new or worsening cough in a dog with a heart murmur should be discussed with a veterinarian, especially if the murmur has not recently been evaluated.
Seek immediate veterinary care if your dog:
Has difficulty breathing or noticeably increased breathing effort
Is breathing rapidly while resting or sleeping
Has blue, gray, white, or unusually pale gums or tongue
Cannot comfortably lie down or settle because of breathing difficulty
Develops sudden or severe coughing
Coughs up blood
Becomes weak, collapses, or faints
Has a significant reduction in exercise tolerance
Stops eating or drinking
Develops marked lethargy
Has a swollen or painful abdomen
Has a rapidly worsening cough or breathing pattern
Has known heart disease and develops new or worsening respiratory signs
Dog Coughing Due to Heart Murmur: Treatment
Treatment depends on whether the cough is actually related to underlying heart disease or is caused by a separate respiratory problem.
A veterinarian will assess the heart and lungs and may recommend chest X-rays, blood tests, blood pressure measurement, an electrocardiogram, or an echocardiogram to evaluate the heart and determine whether there are changes affecting the lungs.
Additional respiratory testing may be appropriate if the findings point away from the heart.
Key Takeaway
A dog coughing due to a heart murmur may actually be coughing because of the underlying heart disease responsible for the murmur, rather than because the murmur itself directly causes coughing.
Some cardiac conditions can eventually affect circulation and breathing, but not every murmur represents significant heart disease.
It is also possible for a dog with a heart murmur to develop an unrelated respiratory condition such as kennel cough, tracheal disease, or chronic bronchitis.
This is why a cough should not automatically be interpreted as worsening heart disease.
If your dog has a known murmur and develops a new, persistent, or worsening cough—especially with faster breathing at rest, reduced exercise tolerance, weakness, fainting, or breathing difficulty—veterinary reassessment is important.
An examination and appropriate cardiac or respiratory testing can help determine whether the heart is actually responsible.