Canine heart disease—most commonly myxomatous mitral valve disease (MMVD) in small breeds and dilated cardiomyopathy (DCM) in large breeds—affects millions of dogs. Progressive management through disease stages is essential for maintaining welfare and quality of life.
MMVD is the most common cardiac disease in dogs, accounting for over 75% of cases. The mitral valve leaflets degenerate over time, leading to progressive regurgitation. Cavalier King Charles Spaniels, Dachshunds, Chihuahuas, and other small breeds are predisposed. The ACVIM consensus staging system (Stages A-D) guides treatment and prognosis decisions based on clinical signs, radiographic changes, and echocardiographic measurements.
Early MMVD (Stages A-B1) causes no clinical signs, but owners should be aware of progressive change. Stage B2 (enlarged heart without symptoms) may now benefit from early pimobendan treatment per 2019 ACVIM guidelines. Congestive heart failure (Stage C/D) causes respiratory distress—pulmonary oedema, pleural effusion—exercise intolerance, weakness, and severe welfare compromise. Acute decompensation is a medical emergency causing profound distress.
Pimobendan (positive inotrope and vasodilator) delays progression in Stage B2 and is foundational treatment in heart failure. Furosemide (diuretic) removes excess fluid in congestive heart failure. ACE inhibitors (enalapril, benazepril) reduce cardiac workload. Spironolactone has synergistic diuretic and cardioprotective effects. Multi-drug therapy in advanced disease requires careful monitoring and dose titration to optimise quality of life.
DCM causes progressive ventricular dilation and reduced contractility, primarily in large breeds (Dobermanns, Great Danes, Irish Wolfhounds). Dobermanns face particularly severe disease with sudden cardiac death risk from ventricular arrhythmias. Regular Holter monitoring enables arrhythmia detection and guides antiarrhythmic treatment. DCM progresses rapidly once heart failure develops, with median survival measured in months.
Cardiac dogs require tailored exercise protocols—continued moderate activity at owner-paced levels is beneficial in compensated disease, while severe disease warrants restriction. Dietary sodium reduction is traditional but evidence is mixed. Managing concurrent conditions (hypertension, renal disease) avoids compounding welfare compromise. Monitoring respiratory rate at home enables early detection of worsening fluid accumulation before crisis.
Advanced heart failure causes escalating respiratory distress, weakness, and cardiovascular collapse. Quality euthanasia at home, before terminal respiratory crisis, represents compassionate welfare planning. Many cardiac dog owners benefit from advance discussions about end-of-life signs and decision-making frameworks, reducing the crisis burden when the time comes.