Enlarged Heart (Dilated Cardiomyopathy) in Dogs

Key takeaways

Dilated cardiomyopathy (DCM) in dogs is a progressive heart disease in which the muscle weakens and stretches, losing the ability to pump blood effectively. Blood buildup causes further weakening, stretching, and congestive heart failure. 

  • Dogs with DCM are often asymptomatic until they are in congestive heart failure or develop arrhythmia
  • Symptoms include lethargy, lack of appetite, trouble breathing, cough, abdominal distention, and fainting
  • Multifactorial causes are suspected for DCM including genetic inheritance, diet, toxins, metabolic conditions, and infectious disease 
  • Echocardiogram (heart ultrasound) confirms diagnosis of DCM
  • Most forms of DCM are incurable and treatment focuses on symptom relief, though adequate nutrition may reverse DCM in some cases
  • Prognosis depends on severity of symptoms and underlying cause but most cases have a poor prognosis
Connect with a vet to get more information
Book an online vet

A closer look: Enlarged Heart (Dilated Cardiomyopathy) in Dogs

DCM primarily affects the lower left chamber of the heart (left ventricle), which pumps blood from the lungs to the body, although it can also affect the right side.

Dogs with a cough, weight loss and decreased energy should be evaluated promptly. Difficulty breathing, collapse, sudden weakness, or fainting in dogs is an emergency.

Connect with a vet to get more information

With DVM, ICH certifications and great reviews by pet parents like you for this symptom

Risk factors

DCM is the second most common type of heart disease in dogs and large breed dogs are predisposed.

In recent years there has been a great deal of reporting and public interest in whether DCM is directly correlated with nutritional deficiencies in dogs. In particular there has been concern that DCM is associated with speciality diets such as grain-free or legume-based protein formulations. Research is ongoing and more information is needed to fully understand the relationship between grain-free and legume-based diets and DCM in dogs. Feeding a well balanced, vet recommended diet is considered the best standard for avoiding nutrient deficiencies.

DCM, in most cases, progresses to congestive heart failure (CHF).

Possible causes

  • Idiopathic (unknown)
  • Nutritional factors, in particular taurine deficiency
  • Genetic
  • Chemical/toxin exposure, including Doxorubicin and Epirubicin
  • Infectious disease (rare) including parvovirus and lyme disease
  • Parasitic (rare) including Trypanosomiasis

Main symptoms

Testing and diagnosis

DCM diagnosis starts with a full physical exam. X-rays may be done to visualize an enlarged heart and/or fluid in or around the lungs. Echocardiogram (ultrasound of the heart) is required to definitively diagnose DCM. Blood tests may be done to identify underlying problems with nutrition or infection. From there, an electrocardiogram (EKG) or a 24-hour EKG (Holter monitor) may be indicated.

Steps to Recovery

Treatment may be complex, involving several types of medications used to increase the heart’s ability to pump blood effectively and treat any arrhythmias. Nutritional supplementation and/or diet change may be indicated. To relieve discomfort, fluid removal procedures may be used on the chest or abdomen.

DCM is a progressive disease, so the prognosis depends on the stage of disease when identified.

Prognosis for diet-associated DCM cases is fair to good, as nutritional changes may reverse the disease process. DCM is more often progressive and incurable, and by the time signs of heart failure are evident, the long-term prognosis is poor and survival time is 6-24 months on average. Left-sided heart failure, which is more common with DCM, carries a worse prognosis than right-sided.


There is no specific prevention for DCM. Ensuring complete and balanced nutrition may be helpful and is recommended in any case. In addition, screening is available to pet parents and breeders of dogs that are predisposed to DCM. Neutering dogs with DCM prevents genetic transmission.

Is Enlarged Heart (Dilated Cardiomyopathy) in Dogs common?

DCM is the second most common heart disease of dogs. Large and giant breed dogs are predisposed, as are certain specific breeds.

Typical Treatment

Depending on the case, treatment may include: Medications

  • Inotropes
  • Antiarrhythmics
  • Diuretics
  • Vasodilators
  • ACE inhibitors
  • Palliative care
  • Diet change
  • Nutritional supplementation


Mark D. Kittleson , DVM, PhD, DACVIM-Cardiology - Writing for Merck Veterinary Manual
Robert Prošek, DVM, MS, DACVIM, ECVIM-CA - Writing for Veterinary Partner
Melissa Boldan, DVM - Writing for petMD

Our editorial committee

Our medical review team is responsible for validating and maintaining the quality of our medical information.