Heart Disease & Murmurs

Heart disease can be present for years before signs appear — which is why routine screening matters. When signs do develop, they often reflect reduced cardiac output or fluid backing up into the lungs:

• A heart murmur detected during a routine exam (often the first sign, before any symptoms)
• Coughing — especially at night or in the early morning in dogs (fluid in the lungs)
• Rapid or labored breathing, or an increased resting respiratory rate at home
• Exercise intolerance — tiring easily on walks, reluctance to play
• Weakness or fainting (syncope) episodes
• Abdominal distension from fluid accumulation (ascites)
• Weight loss and muscle wasting in later stages
• In cats: open-mouth breathing, hiding, or sudden hind-limb paralysis (aortic thromboembolism — a cardiac emergency)

Measuring your pet's resting respiratory rate at home — counting breaths per minute while asleep — is one of the most sensitive early warning signs of heart failure. A rate consistently above 30 breaths per minute in a sleeping dog or cat warrants a call to our team.

The cause of heart disease varies by species and by the specific condition:

• Myxomatous mitral valve disease (dogs) — the valve leaflets gradually thicken and leak; strongly heritable in Cavalier King Charles Spaniels; also very common in Dachshunds, Chihuahuas, and other small breeds
• Hypertrophic cardiomyopathy (cats) — abnormal thickening of the heart muscle; Maine Coons and Ragdolls have identified genetic mutations; many other breeds are also commonly affected
• Dilated cardiomyopathy (dogs) — the heart muscle weakens and the heart enlarges; seen in Dobermans, Great Danes, Boxers, and other large breeds; a possible link to grain-free diets is under ongoing investigation by the FDA
• Secondary heart disease — caused by hyperthyroidism (cats), systemic hypertension, congenital defects (patent ductus arteriosus/PDA, subaortic stenosis, pulmonic stenosis), or heartworm infection

Age is a universal risk factor: cardiac disease becomes progressively more common in dogs over seven and cats over ten.

A thorough cardiac work-up tailored to the individual patient typically includes:

• Auscultation (listening with a stethoscope) — characterizes murmur grade, rhythm, and location
• Echocardiogram (cardiac ultrasound) — performed on-site by Dr. D'Urso; this is the gold standard for measuring chamber size, valve anatomy, and heart function. It determines whether a dog with MMVD has reached the threshold where medication is beneficial (EPIC/QUEST study criteria).
• Chest radiographs (X-rays) — assess heart size and detect fluid in the lungs (pulmonary edema)
• Electrocardiogram (ECG) — identifies arrhythmias
• Blood pressure measurement — hypertension worsens cardiac disease and may be the primary driver in some cats
• Blood panel and NT-proBNP test — a blood biomarker that rises when the heart is under stress; useful for monitoring and for screening cats (a cardiac biomarker profile can suggest early HCM before symptoms appear)

Treatment is tailored to the type of heart disease, its stage, and the individual patient. Common approaches include:

• Pimobendan (Vetmedin) — a heart-strengthening medication now recommended before symptoms appear in dogs with enlarged hearts from MMVD; strongly evidence-based (EPIC trial)
• Diuretics (furosemide, torasemide) — remove excess fluid from the lungs in congestive heart failure
• ACE inhibitors and other vasodilators — reduce the heart's workload and help manage blood pressure
• Anti-arrhythmic medications — for dogs (especially Dobermans or Boxers) with dangerous rhythm problems
• Atenolol and other beta-blockers — used in cats with HCM and certain arrhythmias
• Anti-clot therapy (clopidogrel) — recommended for cats with HCM at elevated risk for aortic thromboembolism (ATE)
• Interventional cardiology — patent ductus arteriosus (PDA) ligation and pericardectomy are performed by our surgical team for select cases

Dietary management (sodium restriction in heart failure), exercise modification, and home respiratory rate monitoring are important complements to medication.

Any pet with a newly detected heart murmur should have an echocardiogram to determine its significance — many murmurs are present for years before any action is needed, but knowing the baseline is essential. Cats with HCM are at risk for sudden catastrophic events, and pre-emptive screening of at-risk breeds (Maine Coons, Ragdolls) gives the best chance of early intervention. If your dog or cat is breathing faster than usual at rest, coughing at night, or suddenly seems to have weak or cold hind legs, call us immediately — these may be signs of heart failure or ATE. Dr. D'Urso's on-site cardiology means you can get expert evaluation without the wait of a distant specialty center. Book an appointment today.