Heart Disease

Heart disease in dogs encompasses several conditions, most commonly mitral valve disease (MVD) in small breeds and dilated cardiomyopathy (DCM) in large breeds. Both cause the heart to pump less efficiently over time, eventually leading to heart failure if unmanaged.

The encouraging reality is that significant advances in management have extended life and improved quality of life for dogs with cardiac conditions. Early detection - before heart failure develops - allows treatment to begin at a stage where it has the most impact.

The stages of heart disease

Heart disease typically progresses through stages:

• Preclinical (Stage B): Heart disease present (e.g., a heart murmur) but no symptoms. Dogs may be in this stage for months to years.
• Congestive Heart Failure (Stage C/D): The heart can no longer compensate. Fluid accumulates in the lungs (pulmonary oedema) or abdomen (ascites). Symptoms become apparent.

Treatment in Stage B can significantly delay progression to heart failure. This is why regular cardiac monitoring matters - catching the transition point allows earlier intervention.

What to monitor

Resting respiratory rate (RRR). This is the single most important home monitoring tool for dogs with known heart disease. Count breaths per minute while your dog is sleeping or at complete rest - chest rises and falls count as one breath. A normal sleeping respiratory rate is below 30 breaths per minute. A rate consistently above 30 warrants vet contact; a sudden increase is an emergency.

To measure accurately: count for 30 seconds and multiply by two. Take three readings over different times and days and log the average.

Exercise tolerance. Note how far your dog walks before they slow, stop, or show reluctance. Declining exercise tolerance is an early sign of reduced cardiac output.

Cough. A soft, persistent cough - particularly at night or at rest, rather than during exercise - can indicate fluid in the lungs. Note whether the cough is dry, productive, the time of day, and frequency.

Appetite. Reduced appetite is a sign of worsening cardiac status.

Breathing at rest. Note whether breathing seems laboured, rapid, or effortful when the dog is at rest.

Fainting (syncope). Sudden collapse or brief loss of consciousness, often during or after exercise or excitement, requires immediate veterinary assessment.

Abdominal distension. A swollen or rounded abdomen may indicate fluid accumulation (ascites).

Starting a resting respiratory rate log

Log the RRR every day at the same time - ideally first thing in the morning when your dog is sleeping. Over time, you establish your dog's personal normal. A single reading of 28 is fine; a trend from 22 to 28 to 32 over three weeks is significant.

Many cardiac apps and general pet health apps allow you to enter daily RRR values and visualise the trend - use this feature if available.

When to contact your vet

Go to the emergency vet immediately if:

• Breathing is laboured, rapid, or the dog seems to be struggling to breathe
• Your dog faints or collapses
• RRR is above 40 breaths per minute while at rest
• Gums are pale, blue, or grey

Contact your vet the same day if:

• RRR has risen consistently above 30 over several days
• A new or worsening cough has developed
• Your dog is significantly less willing to exercise than a week ago

Schedule a routine appointment for:

• Regular cardiac assessments and echocardiography as recommended
• Medication reviews and dose adjustments
• Annual or biannual monitoring in preclinical dogs

Frequently Asked Questions

My dog has a heart murmur - does that mean they have heart disease? A heart murmur is a sound caused by turbulent blood flow. It may indicate structural heart disease, but some murmurs are benign (functional murmurs). Your vet will grade the murmur (1–6) and may recommend echocardiography to assess whether structural disease is present.

Can heart disease in dogs be cured? In most cases, no - the underlying structural changes are not reversible. Management aims to slow progression, control symptoms, and maintain quality of life. Some conditions (e.g., patent ductus arteriosus in puppies) are surgically correctable.

What medications are used for heart disease in dogs? The most commonly used drugs include ACE inhibitors (enalapril, benazepril) which reduce the heart's workload, pimobendan (Vetmedin) which improves heart muscle function and is licensed for both MVD and DCM, and diuretics (furosemide, torasemide) which help clear fluid accumulation. The specific combination depends on the stage of disease.

My dog's vet mentioned BOAS scoring - is this related to heart disease? BOAS is a separate condition (brachycephalic airway disease). It is not directly the same as heart disease, though respiratory signs can overlap. If a dog has both conditions, it's important the vet is aware of both.

Should Cavalier King Charles Spaniels be screened for MVD? Yes. The Kennel Club and British Veterinary Association run the MVD Breeding Scheme for CKCSs. Breeding dogs should be screened by a cardiologist to reduce prevalence of the condition in the breed. For pet CKCSs, annual cardiac assessments from age one are generally recommended.