Symptoms and treatment of canine hypertrophic cardiomyopathy.
Hypertrophic cardiomyopathy(HCM) is a heart disease caused by thickening of the left ventricular wall and decreased blood volume. Blood pools in the left atrium, causing it to expand. Eventually the volume of the left ventricle becomes smaller and smaller, blood pools in the lungs, and left heart failure occurs.
Thrombus can occur in left atrium congestion, and the thrombus can migrate to other parts of the body. The left ventricular output is blocked, resulting in a decrease in cardiac output.
The cause of most HCM is unclear. In Maine Coon cats, American shorthair cats, and puppet cats, HCM is a hereditary disease. Norwegian forest cats, Turkish vanilla cats, Scottish fold cats, British shorthair cats and Devon Rex cats also have genetic predispositions .
HCM can also be secondary to hyperthyroidism, hypertension, and aortic stenosis. The incidence of males is higher than that of females.
The main symptoms
80% of affected cats can auscultate heart murmurs during routine physical examination. Therefore, HCM is usually found before heart failure occurs. Arrhythmia or extra heart sounds can be auscultated.
The clinical manifestations of HCM vary with severity. Symptoms can progress from mild to severe, and can also remain stable for several years.
Early symptoms include drowsiness and exercise intolerance. The initial manifestations may be increased breathing rate (greater than 50 breaths/min) and forced breathing. If there is thrombosis in the front or hind limbs, the affected limb is cold, the foot pads are blue , and paralysis occurs. The initial pain is obvious.
After the heart murmur is auscultated, further examinations should be performed, such as chest X-ray, echocardiography, blood pressure, and thyroid function (for cats greater than 5 years old). Cats with heart failure and thrombosis also need to undergo laboratory tests , mainly including kidney and other organ function tests. If there is arrhythmia, an electrocardiogram is required.
Maine Coon and Ragdoll cats can undergo blood genetic testing.
There are no drugs to prevent HCM, so asymptomatic cats generally do not need treatment until they have a significant decrease in cardiac output, thickened ventricles, enlarged atria, and increased heart rate. The treatment drugs are atenolol and diltiazem. Cats with asymptomatic HCM secondary to hypertension or hyperthyroidism do not need to use HCM drugs if the primary disease has been controlled.
Cats that have developed heart failure need to be hospitalized, including oxygen inhalation, diuretics (furosemide), nitroglycerin, etc., until the condition is stable. If the pleural effusion is large, it may need to be removed by puncture. Once the symptoms of heart failure are stable, furosemide, atenolol (beta-blockers) or diltiazem (calcium channel blockers) can be taken orally. These drugs keep the heart at a relatively slow heart rate so that the left ventricle has enough time to perfuse.
If the left atrium is enlarged, medications to prevent thrombosis can be used.
ACEI (Angiotensinase Inhibitor), such as enalapril, benazepril, ramipril, can be used to reduce fluid retention, especially when the animal has developed left heart failure.