Heart Disease and Breathing Problems in Dogs

Heart disease in dogs — most commonly mitral valve disease in small breeds and dilated cardiomyopathy in certain larger breeds — tends to announce itself through breathing and coughing changes well before any more dramatic cardiac symptom becomes obvious. This makes respiratory signs genuinely valuable early warning indicators, and it's part of why several symptoms across this guide keep circling back to heart disease as an underlying cause.

The progression typically follows a recognizable pattern: exercise intolerance appears first, often subtly, followed by a soft cough that's worse at night or after lying down, then a gradually rising resting or sleeping respiratory rate as the condition advances, and in more progressed cases, visible labored breathing and potentially coughing up foam or fluid as fluid accumulates around the lungs (a condition called congestive heart failure).

Small breeds — Cavalier King Charles Spaniels, Chihuahuas, Dachshunds, Poodles, and similar — are at meaningfully elevated risk for the valve disease that most commonly causes this pattern, and regular veterinary check-ups that include listening to the heart become increasingly valuable as these breeds age.

What to do: Any combination of the signs above, especially in a small-breed or senior dog — a new cough worse at night, declining exercise tolerance, or a rising resting respiratory rate — warrants a vet visit focused on cardiac evaluation. Medication can meaningfully slow disease progression and improve quality of life when started early, which makes catching this pattern sooner rather than later genuinely worthwhile.

For the individual pieces of this pattern in more depth, here's more on the specific nighttime coughing signature and tracking resting respiratory rate as an early indicator.