What is an enlarged heart in dogs?

Good question. An enlarged heart is, to put it simply, a big heart, but the big heart can be due to various reasons, and finding out that reason is important because it could weigh in on different prognoses. So it could either be an enlarged chamber of the heart or an enlargement around the heart.

An enlarged heart in dogs is exactly what it sounds like - a heart that is larger than it should be. This usually indicates some type of disease, such as one of the chambers becoming too big or too thick.

An enlarged heart is what we would call any sort of dilated or hypertrophic cardiomyopathy where either the heart is enlarging and thinning in dilated cardiomyopathy, think like filling a water balloon, it gets stretched and thinner, versus hypertrophic cardiomyopathy where the heart is actually laying down extra muscle, and that's usually in response to increased resistance or increased regurgitation through one of those one-way valves.