What is the most common type of heart disease in dogs?

Mitral valve disease is recognized as the most common type of heart disease in dogs, particularly in older and small breed dogs. This condition involves the deterioration of the mitral valve, which can lead to leakage (regurgitation) of blood back into the left atrium during contraction of the heart. As a result, it often causes heart murmurs and can progress to congestive heart failure if not managed appropriately.

Unlike hypertrophic cardiomyopathy, which is more prevalent in cats than in dogs, mitral valve disease specifically affects the canines and is often asymptomatic initially. Over time, as the valve's function worsens, signs such as coughing, fatigue, and difficulty breathing may develop due to fluid accumulation in the lungs.

Arrhythmia refers to irregular heartbeats but is not categorized as a specific disease and can occur as a consequence of various heart conditions, whereas congestive heart failure is a syndrome or outcome of heart disease rather than a specific type of heart disease itself. Thus, while each of the other options relates to heart conditions, mitral valve disease remains the clear leader in prevalence among canine heart issues.