DCM (Dilated Cardiomyopathy) in dogs

Dilated cardiomyopathy (DCM) is the second most common heart disease in dogs after MMVD. The heart muscle weakens and the chambers enlarge, reducing the heart's ability to pump effectively. DCM is primarily a disease of large and giant breeds, with a strong genetic component in several breeds. Specialist cardiology is needed for accurate diagnosis, arrhythmia management, and medication optimisation.

What it is

In DCM, the myocardium (heart muscle) becomes thin and weakened, causing the left — and sometimes right — ventricle to dilate. Reduced cardiac output triggers compensatory responses that ultimately accelerate disease. Many dogs have a prolonged 'occult' phase (abnormal echo with no symptoms) during which early treatment can slow progression. DCM also causes arrhythmias (especially in Dobermanns) that can cause sudden death independently of pump failure.

When it's needed

• Diagnosis from echocardiogram or Holter monitor in predisposed breeds (Dobermann, Irish Wolfhound, Great Dane, Boxer, Cocker Spaniel)
• Occult DCM phase — echo abnormalities detected before clinical signs; early medication initiated
• Symptomatic DCM — exercise intolerance, syncope, respiratory distress, arrhythmia
• Congestive heart failure — emergency hospitalisation, oxygen, IV diuresis
• Ongoing monitoring of arrhythmia burden with 24-hour Holter monitoring

The procedure

Management is medical — pimobendan is the cornerstone of treatment in both occult and overt DCM. Antiarrhythmic drugs (sotalol, mexiletine, amiodarone) are used when ventricular arrhythmias are significant. ACE inhibitors and diuretics manage fluid retention in CHF. Implantable defibrillators are not routinely available in veterinary medicine.

Recovery

Occult DCM: pimobendan extends the time to CHF by roughly 9 months (PROTECT study). Overt DCM: median survival after first CHF episode is 4–6 months in most breeds, though individual responses vary significantly. Dobermanns with arrhythmias have a risk of sudden cardiac death independent of pump function.

Frequently asked questions