What Is a Heart Murmur?
A heart murmur is an abnormal whooshing or swishing sound heard through a stethoscope, caused by turbulent blood flow inside the heart or its large vessels. A murmur is a finding, not a disease: it tells your vet that something is changing the way blood moves, and that cause can range from harmless to serious.
Not always bad news
Many puppies and kittens have soft “innocent” murmurs that fade by about 4 to 6 months of age. A new murmur in an adult pet deserves a closer look.
Murmur Grades
- Grade 1 to 2: soft, hard to hear
- Grade 3 to 4: moderate to loud
- Grade 5 to 6: very loud, with a vibration felt through the chest wall
Loudness does not always match severity, especially in cats, so grade is only one part of the picture.
Common Causes
- Dogs: mitral valve disease in older small breeds, dilated cardiomyopathy in large breeds, and birth defects such as patent ductus arteriosus, subaortic stenosis and pulmonic stenosis
- Cats: hypertrophic cardiomyopathy and hyperthyroidism
- Outside the heart: anemia, fever, pregnancy or excitement can cause temporary “physiologic” murmurs
Signs That Need Attention
- Coughing, especially at night or after rest
- Fast or labored breathing while resting or asleep
- Tiring easily, fainting or collapse
- A swollen belly or poor appetite and weight loss
Count breathing at rest
Many vets suggest counting your pet’s breaths while asleep. A resting rate that climbs above about 30 to 40 breaths per minute is a reason to call your vet.
Diagnosis
An echocardiogram (heart ultrasound) is the best test to find the cause of a murmur. Chest X-rays, blood pressure, an ECG and blood tests such as NT-proBNP may also be used. Cardiac screening is part of a thorough wellness exam.
Treatment and Outlook
Treatment depends entirely on the cause. Innocent murmurs need nothing. Valve disease and cardiomyopathy are often managed with medication once they reach a certain stage, and some birth defects can be corrected with surgery or catheter procedures. Many pets with murmurs live long, comfortable lives with regular monitoring.
Frequently Asked Questions
Is a heart murmur a death sentence?
No. Many murmurs are mild or harmless, and even pets with heart disease often do well for years with monitoring and treatment.
Can my pet still have anesthesia?
Often yes, but your vet may recommend an echocardiogram first to plan the safest anesthesia.
Does a murmur affect pet insurance?
It can be treated as a pre-existing condition once noted. See congenital condition coverage in pet insurance.
Did your vet hear a murmur? Find a veterinary clinic near you for an exam.