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Heart Disease (Hypertrophic Cardiomyopathy) in Dogs

Cardiomyopathy, Hypertrophic in Dogs

Hypertrophic cardiomyopathy (HCM) is an uncommon heart muscle condition found in dogs. It involves the thickening of the heart walls, resulting in inadequate blood pumping during systolic contraction and insufficient blood filling during diastolic relaxation. If left untreated, HCM can progress to congestive heart failure.

This condition primarily affects young male dogs under three years old and is more prevalent among mature Boston Terriers.

Symptoms and Types

In most cases, dogs with HCM don’t show any symptoms. However, symptomatic dogs typically display signs of congestive heart failure, such as exercise intolerance, shortness of breath, coughing, and a bluish skin discoloration. Occasionally, a dog with HCM might faint during strenuous activity. During a veterinary examination, signs such as a systolic heart murmur and a heart gallop may be observed. Unfortunately, sudden and fatal heart failure is often the most reported clinical sign of HCM.

Causes

The exact cause of HCM in dogs remains largely unidentified. While genetic abnormalities in gene codings for specific proteins have been identified in humans and cats with the disease, no similar evidence has been found in dogs.

Diagnosis

Diagnosing HCM in dogs involves a series of challenging medical tests. Radiographic assessments may show either normal results or indicate an enlargement of the left ventricular and atrium. If left-sided congestive heart failure is present, fluid accumulation in the lungs will be evident. Electrocardiogram (EKG) results are typically normal, although abnormal ST segments and T waves may sometimes appear. Blood pressure readings usually return normal results. A definitive diagnosis of HCM requires an examination of the heart using echocardiograph (ultrasound of the heart) imaging. In severe cases of HCM, the echocardiograph will reveal thickened left ventricular walls, papillary muscle enlargement, and an enlarged left atrium.

Treatment

Typically, treatment for HCM is recommended only when the dog exhibits congestive heart failure, severe arrhythmias (abnormal heart rhythm), or frequent episodes of loss of consciousness. If left-sided congestive heart failure is present, diuretics and ACE inhibitors are commonly prescribed. Dogs with arrhythmias may receive beta-adrenergic blockers or calcium channel blockers to enhance heart oxygenation and lower the heart rate. Dogs not experiencing congestive heart failure due to HCM can often be managed on an outpatient basis, with treatment including exercise restriction and a low-sodium diet.

Living and Management

The follow-up care for HCM will primarily depend on the severity of symptoms. Regular radiographic and echocardiograph imaging will be necessary to monitor the effectiveness of therapy, track disease progression, and assess the need for medication adjustments. Due to the rarity of HCM in dogs, prognosis data is limited. If congestive heart failure is present due to HCM, the prognosis is generally poor, with survival heavily influenced by the extent of the disease. Your veterinarian will offer guidance on your dog’s prognosis and advise on quality of life measures you can implement.

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