If Your Dog Keeps Coughing and Panting — Causes of Dilated Cardiomyopathy and When to Visit the Vet

HeartDiseasesMeongsiljang Veterinary Advisory Board

Dilated cardiomyopathy in dogs is a heart condition in which the heart muscle becomes thin and the chambers abnormally enlarge, leading to reduced contractile function. We’ve compiled essential information for pet owners, covering symptoms, causes, diagnosis, treatment medications, and home care.

What Is Dilated Cardiomyopathy?

Large breed dogs undergoing cardiac examinations at the veterinary clinic

Canine dilated cardiomyopathy (DCM) is a heart disease in which the heart muscle’s ability to contract weakens, causing the heart chambers to abnormally enlarge (eccentric hypertrophy) and the heart to pump blood inefficiently. The most critical point is that by the time symptoms become obvious, heart function is often already significantly impaired. If you notice signs such as coughing, difficulty breathing, lethargy, or fainting, seek veterinary care immediately. While DCM is most common in large and giant breeds like Doberman Pinschers, Great Danes, Irish Wolfhounds, and Newfoundlands (reported in approximately 0.5–1.4% of the general dog population), it can also occur in some small-to-medium breeds, such as Cocker Spaniels. Note that the heart condition commonly seen in Boxers resembles DCM but is classified separately as arrhythmogenic right ventricular cardiomyopathy (ARVC), which has distinct characteristics.

Why Does It Occur? Causes and Pathogenesis

The causes of dilated cardiomyopathy can be broadly categorized into three main groups.

Genetic factors: A strong familial or genetic predisposition is suspected in certain breeds, such as Doberman Pinschers, Great Danes, Irish Wolfhounds, and Newfoundlands. However, in most cases, the specific DNA defects have not yet been clearly identified. The condition seen in Boxers resembles DCM but is classified separately as arrhythmogenic cardiomyopathy, which has distinct characteristics.

Nutritional factors: Deficiencies in specific nutrients, such as taurine, can be associated with cardiomyopathy (taurine-deficient DCM in cats is a classic example). In cases where nutritional deficiency is the cause, heart function may recover after correction.

Other factors: Cases linked to diet or idiopathic cases with no clear cause have also been reported.

The underlying causes and disease progression can vary significantly depending on the breed.

Key Symptom Checklist

Persistent coughing: If the cough worsens at night or when lying down, it may be a sign of heart failure.

Shortness of breath or panting: If your pet breathes heavily with minimal activity or their tongue turns blue (cyanosis), immediate veterinary attention is required.

Exercise intolerance: If your pet frequently refuses walks or tires quickly and collapses, this should raise suspicion.

Abdominal distension: Heart failure can lead to fluid accumulation in the abdomen (ascites), causing the belly to appear swollen.

Fainting or sudden collapse: If accompanied by arrhythmia, your pet may suddenly lose consciousness.

A puppy showing signs of shortness of breath and lethargy, with a concerned owner by its side.

Emergency Signs Requiring Immediate Veterinary Care

Seek immediate care at a 24-hour veterinary clinic if you notice any of the following signs: 1) Blue or pale discoloration of the lips, tongue, or gums (cyanosis); 2) Severe, persistent difficulty breathing while sitting or lying down; 3) Sudden collapse or loss of consciousness; 4) Extreme lethargy with an inability to stand. These symptoms may indicate acute heart failure, which is life-threatening.

How Is It Diagnosed?

Diagnosing dilated cardiomyopathy requires a combination of tests.

Auscultation: This is the first step to check for heart murmurs and irregular heartbeats.

Chest X-ray: This helps assess heart enlargement and pulmonary congestion.

Echocardiogram: This is the key test for precisely measuring ventricular size, contractility (fractional shortening), and ejection fraction.

Electrocardiogram (ECG): This confirms the presence and type of arrhythmia.

Blood and biomarker tests: These evaluate the extent of myocardial damage by measuring cardiac stress markers (NT-proBNP) and troponin levels.

Treatment Methods — Medication Management

Currently, treatment focuses more on reducing the heart’s workload and extending lifespan rather than achieving a complete cure.

Pimobendan: Enhances myocardial contractility and dilates blood vessels. It is recommended for use starting from the preclinical stage.

Diuretics: Help eliminate excess fluid when fluid accumulates in the lungs.

Vasodilators (ACE inhibitors): Lower blood pressure and inhibit cardiac remodeling.

Antiarrhythmics: Added when arrhythmias such as ventricular tachycardia are present.

The specific combination of medications and dosages is determined by the veterinarian based on echocardiographic findings.

A scene in which a veterinarian explains the treatment plan based on the results of an echocardiogram.

Home Care Management Points

Activity Management: Avoid strenuous exercise and limit physical activity to short walks. If heart failure is severe, prioritize indoor rest.

Low-Sodium Diet: Choose prescription diets low in sodium or food recommended by your veterinarian.

Regular Echocardiographic Exams: Regularly monitor changes in heart size and contractile function (fractional shortening) to guide medication adjustments. Your veterinarian will determine the appropriate examination intervals based on your pet’s cardiac condition.

Weight Management: Maintain an ideal body weight, as obesity places additional strain on the heart.

Adherence to Medication Schedule: It is crucial to administer heart medications, such as pimobendan, exactly as prescribed by your veterinarian in terms of dosage and timing, without missing any doses.

At-Risk Breeds and Preventive Screening Guide

Large and giant breeds such as Doberman Pinschers, Great Danes, Irish Wolfhounds, and Newfoundlands have a higher genetic predisposition to dilated cardiomyopathy. Boxers, on the other hand, are commonly affected by arrhythmogenic right ventricular cardiomyopathy (ARVC), a distinct condition. Since the asymptomatic latent stage is typically detected around 5 to 7 years of age, it is advisable for at-risk breeds to undergo regular echocardiographic screening starting at this age, even if no symptoms are present. If you have concerns about your dog's nutritional status, please consult your veterinarian for dietary and nutritional advice.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Is dilated cardiomyopathy curable?

While a complete cure is currently difficult, symptoms can be managed and quality of life maintained through medication and lifestyle adjustments. Prognosis is especially favorable when management begins during the latent stage, before heart failure symptoms appear. In cases where nutritional deficiencies, such as taurine deficiency, are the underlying cause, cardiac function can sometimes recover after correction.

Which breed is most commonly affected?

It occurs most frequently in large and giant breeds such as Doberman Pinschers, Great Danes, Irish Wolfhounds, and Newfoundlands. It can also appear in some small-to-medium breeds, including Cocker Spaniels. Boxers are prone to arrhythmogenic right ventricular cardiomyopathy (ARVC), a condition that is similar to dilated cardiomyopathy (DCM) but distinct from it.

Should I avoid feeding my pet grain-free food?

There have been reports linking certain nutrient deficiencies or diet-related issues to cardiomyopathy. However, based solely on the veterinary textbooks provided, it is difficult to definitively conclude that a specific type of pet food poses a risk. If you are concerned about your pet’s diet, consult your veterinarian to assess their nutritional status before making any changes.

How often should pets have regular check-ups?

If your pet has already been diagnosed, regular follow-up echocardiograms are recommended. For at-risk breeds, routine screening is also advised as a preventive measure. Your veterinarian will determine the appropriate screening interval based on your pet’s heart condition.

When should I start using Pimobendan?

Pimobendan is a medication that supports heart muscle contraction and helps maintain cardiac function in many dogs. The appropriate time to start treatment and the correct dosage are determined by your veterinarian based on echocardiogram results and the dog’s overall heart condition.

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References

[1] Freid KJ, Freeman LM, Rush JE, Cunningham SM, Davis MS, et al. Retrospective study of dilated cardiomyopathy in dogs. J Vet Intern Med. 2020;35(1):58–67. PMID: 33345431.

[2] Adin D, DeFrancesco TC, Keene B, et al. Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type. J Vet Cardiol. 2019;21:1–9.

[3] Palermo V, et al. A missense variant in the titin gene in Doberman Pinscher dogs with familial dilated cardiomyopathy and sudden cardiac death. Hum Genet. 2019;138(5):515–524. PMID: 30715562.

[4] Keene BW, Panciera DP, Atkins CE, et al. Myocardial L-carnitine deficiency in a family of dogs with dilated cardiomyopathy. J Am Vet Med Assoc. 1991;198(4):647–650.

[5] Boag AK, Hughes D, eds. Small Animal Critical Care Medicine, 3rd Ed. Elsevier, 2023. Chapter on Canine Cardiomyopathy.