Heart Disease in Senior Dogs: Murmurs, Coughs and Treatment

Two diseases account for most heart problems in older dogs. Mitral valve disease (MVD), a leaky valve, dominates in small and medium breeds and is nearly universal in old Cavalier King Charles Spaniels. Dilated cardiomyopathy (DCM), a weakened heart muscle, dominates in large breeds such as Dobermans, Great Danes, Irish Wolfhounds and Boxers. Both are progressive, both are treatable, and in both, treatment started before symptoms buys time.

Signs

• A heart murmur found at a check-up (often the first and only sign for years)
• Coughing, especially at night or after lying down
• Faster breathing at rest; breathing with the belly
• Tiring on walks, reluctance to exercise
• Fainting or collapse, particularly with excitement (more typical of DCM and rhythm problems)
• Swollen belly (fluid), weight loss and muscle loss in later stages
• Restlessness at night, unable to settle lying down

What the vet does

Listening to the heart grades the murmur. Chest X-rays show heart size and any fluid in the lungs. An echocardiogram (ultrasound) is the definitive test: it shows the valve, the chamber sizes and how well the muscle pumps, and it decides whether medication should start. In large breeds, a 24-hour Holter monitor detects the rhythm abnormalities of early DCM. A blood test, NT-proBNP, helps screen and monitor.

Treatment

Before symptoms. For MVD with an enlarged heart, starting pimobendan before any symptoms delayed the onset of heart failure by around 15 months in a large trial. For Dobermans with early DCM, the same drug delayed heart failure and extended survival. This is why a murmur in a senior dog deserves an echo rather than a wait-and-see.

Heart failure. Diuretics to clear fluid, pimobendan, ACE inhibitors, sometimes spironolactone and anti-arrhythmic drugs. Dogs often go from crisis to comfortable within days, and many live well for a year or more on medication.

Diet. Mild sodium restriction, adequate protein and calories (heart failure causes muscle loss), omega-3 supplementation. Avoid grain-free and pulse-heavy diets, which have been associated with DCM in dogs without a genetic predisposition; if your dog is on one and develops DCM, tell your vet.

Home monitoring. Sleeping breathing rate weekly. Over 30 per minute on repeated counts is the earliest sign that fluid is building and a dose needs adjusting.

Breed screening

Cavaliers should have their heart listened to yearly from age one. Dobermans, Boxers and giant breeds benefit from yearly Holter and echo from around age three. The specifics are on each breed’s page.