What is the most common acquired cardiac defect in dogs?

Mitral insufficiency is recognized as the most common acquired cardiac defect in dogs, particularly as they age. This condition occurs when the mitral valve does not close properly, allowing blood to flow back into the left atrium from the left ventricle during contraction. This backflow can lead to volume overload in the heart and subsequently cause congestive heart failure if left untreated.

The condition is frequently seen in small and toy breed dogs, such as Cavalier King Charles Spaniels, Dachshunds, and Poodles. Over time, the condition can progress from a benign state to one requiring medical management, which may include the use of diuretics, ACE inhibitors, or other medications aimed at improving heart function and controlling symptoms.

In contrast, other options listed are not the most common acquired disorders. Congenital heart disease, while significant, refers to defects present at birth rather than acquired later in life. Aortic stenosis is also an acquired condition but is less prevalent compared to mitral insufficiency. Cardiomyopathy, although a significant ailment affecting the heart muscle, is not as commonly seen as mitral insufficiency among acquired conditions in dogs.