Hypertrophic cardiomyopathy in cats (HCM) is a common heart disease characterized by abnormal thickening of the heart muscle, particularly in the left ventricle. This condition decreases the heart’s ability to efficiently pump oxygenated blood throughout the body, leading to various health issues.
Causes and Risk Factors
The exact cause of HCM is often unknown, though genetic predisposition is suspected, especially in breeds like the Maine Coon, Persian, Ragdoll, and American Shorthair. Other potential contributing factors include:
- Underlying diseases: Hyperthyroidism and hypertension can cause myocardial thickening.
- Viral infections: Conditions like feline panleukopenia may play a role, although their involvement is not clearly established.
- Cardiac obstructions and infiltrative diseases: Subaortic stenosis or lymphoma can affect cardiac function.
- Other rare causes: Hypersomatotropism (acromegaly) is an uncommon cause of HCM.
Affected cats typically range between 5 to 7 years of age, with males appearing more at risk. The condition is rare in dogs.
Symptoms and Disease Progression
HCM leads to stiffness of the left ventricle, increasing cardiac pressure and causing complications such as:
- Pulmonary edema (fluid accumulation in the lungs)
- Pleural effusion (fluid in the chest cavity)
- Ascites (fluid in the abdomen, though less common)
- Aortic thromboembolism (blood clot formation that can cause paralysis)
Clinical Signs to Monitor
- Difficulty breathing (dyspnea)
- Exercise intolerance and excessive fatigue
- Loss of appetite (anorexia)
- Sudden collapse or death
- Occasional vomiting
- Cardiac arrhythmias and heart murmurs
- Weak femoral pulse
- Crackling lung sounds upon auscultation
- Sudden paralysis of hind limbs due to thromboembolism
Diagnosis
Diagnosis involves several key exams:
- Chest X-rays: Assess heart size and detect pulmonary edema.
- Cardiac ultrasound (echocardiogram): The gold standard to measure myocardial thickness.
- Blood tests: Identify underlying conditions such as hyperthyroidism.
- Electrocardiogram (ECG) and blood pressure measurement: Supplementary tests to evaluate cardiac function.
- Pro-BNP blood test: Aids in screening and diagnosing HCM.
Treatment and Management
Severe cases may require hospitalization with oxygen therapy and stress management. Medical treatments aim to:
- Reduce heart rate and regulate arrhythmias
- Enhance ventricular relaxation
- Dilate blood vessels to improve circulation
- Prevent blood clot formation
In cases of severe complications, medications are given specifically to treat pulmonary edema, pleural effusion, or ascites.
Long-term Follow-up and Prognosis
Continuous veterinary follow-up is crucial to adjust treatment and manage disease progression. A sodium-restricted diet (such as Hill’s Prescription Diet h/d) and reduced physical activity are recommended.
The prognosis depends on the severity:
- Asymptomatic cats: Median life expectancy exceeds 5 years.
- Young males and Ragdolls: Typically aggressive progression.
- Severe heart failure: Median survival is 3 months, though some live over 2 years.
- HCM with aortic thromboembolism: Typically less than 2 months survival, though some survive up to 6 months.
Conclusion
Hypertrophic cardiomyopathy in cats is a serious condition requiring ongoing veterinary care for optimal management and outcomes.
