Endocarditis in Dogs and Cats: Symptoms, Treatment, and Prevention

1 Symptoms

Chronic fibrous degeneration of the atrioventricular valves and endocardium is a common cause of heart disease and is divided into infectious and non-infectious forms. Systemic bacterial or viral infection, heartworm, and protozoa can all produce endocarditis.

Valvular endocarditis often follows persistent bacterial infection, chronic sepsis, pleurisy, rheumatism, mastitis, metritis, or prostatitis; fungi and rickettsia can also be responsible. Male cats with hypertrophic cardiomyopathy frequently develop severe endocarditis.

Affected pets show reduced appetite, lethargy, lowered exercise tolerance, panting and coughing after activity, and intense night-time coughing. Cats may suddenly develop hind-limb gait difficulty with left-ventricular hypertrophy, left-atrial enlargement, and arterial embolism. A holosystolic murmur and gallop rhythm are audible on auscultation.

2 Causes and Transmission

Endocarditis develops when bacteria, viruses, fungi, rickettsia, heartworm, or protozoa reach the heart valves via the bloodstream, often seeding onto previously damaged valve tissue. Uremic dogs are also prone to atrial wall endocarditis.

The initiating infections may be contagious or environmentally acquired, and heartworm is mosquito-transmitted, so general infection control and parasite prevention reduce risk.

3 Diagnosis

A new or changing murmur with systemic signs of infection raises suspicion. Echocardiography visualizes vegetations on the valves and measures chamber enlargement, while blood cultures identify the organism.

Electrocardiography documents arrhythmias and embolism-related changes, radiographs assess heart size and lung congestion, and cardiac biomarkers confirm myocardial stress. Heartworm testing is performed when that cause is possible.

4 Treatment

Treatment uses adequate, prolonged antibacterial therapy to control sepsis and prevent heart failure, kidney failure, and arrhythmias. Veterinary-directed antibiotics are chosen by culture and sensitivity and given for many weeks.

Loop diuretics and potassium-sparing diuretics manage fluid overload, and antiarrhythmic agents (lidocaine-class or quinidine-class) control ventricular rhythm disturbances. Underlying heartworm is addressed separately under careful supervision. All dosing follows veterinary guidance.

5 Prevention

Prompt treatment of bacterial infections, dental disease, and uterine or prostate infections limits the spread of organisms to the heart. Year-round heartworm prevention removes a recognized trigger.

Regular veterinary exams, good dental care, and early antibiotic therapy for sepsis reduce the chance of valve colonization. Report persistent cough, fatigue, or lameness to a veterinarian early.