Understanding the Seriousness of Heart Murmurs in Cats
A heart murmur in a cat is an abnormal sound heard during a veterinary examination with a stethoscope. Instead of the normal "lub-dub" heart sounds, a murmur produces an additional "whooshing" noise due to turbulent blood flow in the heart or blood vessels. The seriousness of this condition varies depending on the underlying cause, which may range from completely harmless to severely life-threatening.
Types of Heart Murmurs
- Innocent (Physiologic) Murmurs: These are low-grade murmurs often found in young healthy kittens or in adult cats undergoing stress. They are usually soft, not linked to disease, and may disappear with age or relaxation.
- Pathologic Murmurs: These are due to structural issues in the heart or diseases affecting blood circulation and require further evaluation and management.
Grading of Murmurs
Murmurs are categorized by their loudness on a scale from 1 to 6:
- Grade 1: Very soft, barely audible
- Grade 2: Soft but easily detectable
- Grade 3: Moderately loud
- Grade 4: Loud and can be felt on the chest
- Grade 5: Very loud with a palpable thrill
- Grade 6: Extremely loud, clearly audible with the stethoscope slightly off the chest
It’s important to note that the grade doesn't always indicate the severity of heart disease—some serious conditions may produce low-grade murmurs and vice versa.
Common Causes of Heart Murmurs in Cats
Several health issues can lead to heart murmurs:
- Congenital heart defects (e.g., VSD, ASD, PDA)
- Cardiomyopathies, especially hypertrophic cardiomyopathy (HCM)
- Valvular insufficiencies or stenosis
- Systemic hypertension (high blood pressure)
- Anemia
- Hyperthyroidism
- Heartworm infection
- Endocarditis (infection of the heart valves)
- Other metabolic or systemic diseases
Breed Predisposition
Certain breeds like Maine Coons, Ragdolls, British Shorthairs, American Shorthairs, and Siamese cats have genetic risks of developing heart conditions that may be associated with murmurs.
Symptoms of Underlying Heart Disease
- Weakness or lethargy
- Exercise intolerance
- Rapid or labored breathing
- Panting
- Loss of appetite or weight
- Hiding more than usual
- Pale or bluish gums
- Fainting or collapse
- Fluid buildup in the lungs
- Sudden hind limb pain or paralysis (from blood clots)
- Stunted growth in kittens
Diagnosis and Monitoring
If a murmur is detected, a veterinarian may conduct:
- Echocardiogram: Ultrasound of the heart, the most definitive test
- Chest X-rays: To check heart size and lung fluid
- Blood tests: To detect conditions like anemia and hyperthyroidism
- Electrocardiogram (ECG): Checks for rhythm abnormalities
- Blood pressure measurement
Treatment Approaches
- Innocent murmurs: Require no treatment, just monitoring
- Treatment for underlying conditions: May involve medications for heart failure, controlling blood pressure and thyroid levels, or managing systemic illness
- Surgical correction: Rare but possible for certain defects
- Regular follow-up: Including ultrasound, lab work, and physical exams
- Nutrition and stress management
Prognosis and Outlook
The outlook for cats with heart murmurs varies:
- Innocent murmurs and mild disease often carry a good to excellent prognosis.
- Severe heart disease can lead to more guarded or poor outcomes.
Regular veterinary checkups and early detection play key roles in improving the quality and longevity of life for cats with significant heart conditions. With proper care, many cats with murmurs—whether benign or linked to disease—can live comfortably for many years.
