Many dogs with heart disease act normal at first. A heart murmur found during a routine visit may be the earliest clue, especially in small, older dogs with mitral valve disease. The signs owners notice later—less stamina, coughing, or breathing differently—are important but do not diagnose a heart problem on their own.
What owners might notice
Reduced stamina. A dog that once finished a familiar walk may lag behind, pause to rest, or avoid play. Heat, pain, arthritis, and respiratory illness can cause similar changes, so a physical examination matters.
A new or persistent cough. Heart failure can be associated with coughing, but airway disease is also common in dogs. In fact, a coughing dog with a heart murmur does not automatically have congestive heart failure. Your veterinarian may recommend chest radiographs to tell these causes apart.
Faster breathing while asleep. When a calm dog is sleeping, watch the chest rise and fall for a full minute. Note the usual rate and any consistent upward change. Repeated rates above about 30 breaths a minute in a dog with known heart disease deserve a call to the veterinary team; obvious effort or distress requires emergency care at any rate.
Changes in appetite or behavior. Weakness, restlessness at night, and difficulty getting comfortable are less specific clues that can accompany serious illness.
Signs that cannot wait
Seek emergency veterinary care for labored breathing, blue or gray gums, collapse, or fainting—especially if breathing does not promptly return to normal. Keep the dog calm and cool while arranging transport. Do not give human heart medications or extra doses of a pet’s prescriptions without instructions.
How a veterinarian investigates
Listening to the heart is a useful first step. Depending on the findings, the vet may recommend chest x-rays, an echocardiogram, blood pressure testing, and laboratory work. These distinguish heart enlargement and fluid in the lungs from airway disorders. A cardiac ultrasound is especially useful for characterizing valve disease and staging it.
What to record before your appointment
Keep a short log of cough episodes, sleeping breathing rate, appetite, weight, and how far the dog walks before stopping. A video of unusual breathing or coughing can help the clinician. Avoid strenuous exercise until a dog with new symptoms has been evaluated.
Learn more about heart disease stages and treatment decisions. For dogs that are stable, telehealth can help owners prepare questions, but only an in-person visit can provide necessary imaging and examination.
Evidence
The ACVIM consensus guidelines on canine mitral valve disease explain diagnosis, staging, and why coughing alone cannot establish heart failure. This educational guide does not replace veterinary assessment.
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.