Congestive Heart Failure in Dogs: Recognising and Managing CHF

Congestive heart failure, often abbreviated as CHF, is not a single disease but rather a clinical syndrome — a collection of signs and symptoms that occur when the heart can no longer pump blood effectively enough to meet the body's needs. The term 'congestive' specifically refers to the congestion — the accumulation of fluid — that occurs when blood backs up behind a failing heart. CHF is one of the most common serious conditions affecting older dogs, and understanding it is essential for any owner whose dog has been diagnosed with heart disease.

"Congestive heart failure sounds like a terminal diagnosis, and I understand why owners feel devastated when they hear those words. But what I want every owner to know is that CHF is a manageable condition. With the right medications, careful monitoring, and a dedicated owner, many dogs with CHF continue to enjoy a good quality of life for months to years. The key is early recognition and consistent treatment." — Dr. Sarah Chen, DVM

In a healthy heart, the right side pumps blood to the lungs to pick up oxygen, and the left side pumps oxygen-rich blood out to the body. In CHF, one or both sides of the heart fail to keep up with demand. When the left side fails — the most common scenario in dogs — blood backs up into the lungs, causing pulmonary oedema (fluid in the lung tissue) and respiratory distress. When the right side fails, blood backs up into the body, causing fluid to accumulate in the abdomen (ascites), the liver, and occasionally the limbs.

The most common underlying cause of CHF in dogs is myxomatous mitral valve disease (MMVD), which accounts for roughly 75% of canine heart disease cases. Dilated cardiomyopathy, congenital heart defects, pericardial disease, and heartworm disease are other important causes. Regardless of the underlying disease, the management principles of CHF remain similar. This guide will help you understand how heart disease progresses to heart failure, how to recognise the signs, and how CHF is treated.

Veterinary cardiologists use the American College of Veterinary Internal Medicine (ACVIM) staging system to classify heart disease severity and guide treatment decisions. Understanding these stages helps owners grasp where their dog stands and what to expect next.

Stage A — At Risk

Dogs in Stage A are at increased risk of heart disease due to their breed but have no detectable murmur or structural cardiac changes. This includes breeds predisposed to MMVD (Cavalier King Charles Spaniels, Dachshunds, Miniature Poodles) and breeds predisposed to DCM (Dobermans, Great Danes, Irish Wolfhounds). No treatment is required at this stage, but awareness and regular veterinary check-ups are recommended. For Dobermans and other DCM-prone breeds, screening echocardiography and Holter monitoring should begin at three to four years of age.

Stage B — Heart Disease Without Symptoms

Stage B dogs have structural heart disease — typically a heart murmur and echocardiographic evidence of valve disease or cardiomyopathy — but have never shown symptoms of heart failure. This stage is subdivided:

• Stage B1 — a murmur is present, but the heart has not yet enlarged. No medication is typically recommended. Monitoring with periodic echocardiography (every six to twelve months) tracks progression
• Stage B2 — the heart has enlarged in response to the disease (confirmed by echocardiography and/or chest X-rays). The landmark EPIC study demonstrated that starting pimobendan at this stage delays the onset of heart failure by a median of fifteen months. ACE inhibitors may also be prescribed. This is the critical intervention point — catching dogs at Stage B2 and starting treatment can make an enormous difference in outcomes

Stage C — Active or Previous Heart Failure

Stage C includes dogs that are currently in congestive heart failure or have been in heart failure previously and are now managed with medications. This is the stage at which most dogs are diagnosed, as the symptoms of heart failure — coughing, breathing difficulty, exercise intolerance — prompt owners to seek veterinary attention. Stage C dogs require lifelong medication and regular monitoring.

Stage D — Refractory Heart Failure

Stage D describes dogs whose heart failure symptoms persist despite standard treatment at maximum doses. These dogs have end-stage disease and require intensive, specialised management. Treatment modifications may include higher or more frequent diuretic doses, additional vasodilators, anti-arrhythmic medications, and in some cases, hospitalisation for intravenous therapy. While Stage D carries a more guarded prognosis, some dogs can be stabilised and enjoy additional weeks to months of reasonable quality of life.

Early recognition of heart failure symptoms is one of the most important things a dog owner can do. The sooner CHF is identified and treated, the better the outcome. Symptoms differ somewhat depending on whether the left or right side of the heart is primarily affected.

Left-Sided Heart Failure Symptoms

Left-sided CHF — the most common form — causes fluid to accumulate in the lungs. The hallmark symptoms include:

• Cough — typically a soft, repetitive cough that is worst at night, early morning, or when the dog lies down. Many owners initially attribute this to kennel cough, allergies, or 'just getting older'. The cough is caused by fluid in the lung tissue irritating the airways and by the enlarged left atrium pressing on the main bronchus
• Increased respiratory rate and effort — breathing becomes faster and more laboured, particularly at rest. A consistently elevated sleeping respiratory rate (above 30 breaths per minute) is one of the earliest and most reliable indicators of developing pulmonary oedema
• Exercise intolerance — your dog tires more quickly, walks shorter distances, or stops during walks to rest. Activities that were previously easy become difficult
• Restlessness at night — dogs with pulmonary oedema often struggle to settle and sleep, pacing or changing position frequently. They may prefer to sleep with their head elevated or refuse to lie flat, as lying down worsens fluid accumulation in the lungs
• Breathing difficulty — in severe cases, dogs breathe with open mouths, extend their necks, and adopt a wide-legged stance to maximise chest expansion. This is a medical emergency

Right-Sided Heart Failure Symptoms

Right-sided CHF is less common and causes fluid to accumulate in the abdomen and body tissues:

• Abdominal distension — a pot-bellied appearance develops as fluid (ascites) accumulates in the abdominal cavity. This can progress rapidly and may be mistaken for weight gain
• Jugular vein distension — the jugular veins in the neck may become visibly enlarged or pulsate
• Peripheral oedema — swelling in the limbs, though this is less common in dogs than in humans with right-sided failure
• Hepatomegaly — liver enlargement from blood congestion, which may cause abdominal discomfort

Biventricular Failure

Some dogs develop failure of both sides of the heart simultaneously, presenting with a combination of respiratory and abdominal symptoms. DCM frequently causes biventricular failure, while MMVD more commonly presents with left-sided failure initially.

If your dog shows any of these signs — particularly a new cough, increased breathing rate, or abdominal swelling — schedule a veterinary appointment promptly. In cases of severe breathing difficulty, seek emergency care immediately.

Diagnosing CHF involves confirming that fluid has accumulated due to heart disease and identifying the underlying cardiac condition. Your veterinarian will use a combination of physical examination findings and diagnostic tests.

Physical Examination

A thorough physical examination provides important initial clues. Your vet will listen for a heart murmur (present in nearly all dogs with MMVD-related CHF), an increased heart rate, an irregular heart rhythm, and abnormal lung sounds — crackles or increased breath sounds indicate pulmonary oedema. They will assess the jugular veins for distension, palpate the abdomen for fluid or liver enlargement, and check the pulse quality. The respiratory rate and effort are carefully noted.

Chest X-rays (Radiographs)

Thoracic radiographs are the most important initial diagnostic test for confirming CHF. They reveal heart size and shape (an enlarged vertebral heart score), pulmonary oedema (diffuse, fluffy opacities in the lung fields), pleural effusion (fluid between the lungs and chest wall), and enlargement of the pulmonary veins — all hallmarks of left-sided heart failure. Right-sided failure may show an enlarged vena cava, hepatomegaly, and ascites. Chest X-rays are also invaluable for monitoring treatment response — clearing of pulmonary oedema confirms that diuretic doses are effective.

Echocardiography

An echocardiogram identifies the underlying cardiac disease causing CHF. For MMVD, it demonstrates thickened, prolapsing mitral valve leaflets and mitral regurgitation, along with measurements of left atrial and left ventricular enlargement. For DCM, it reveals thin, poorly contracting heart walls with dilated chambers. The echocardiogram also provides prognostic information — the degree of left atrial enlargement and systolic function directly influence expected survival times.

Blood Tests and Additional Diagnostics

Blood work evaluates kidney function (critical for safe diuretic dosing), electrolytes, and cardiac biomarkers. NT-proBNP is typically markedly elevated in dogs with CHF and can help differentiate cardiac from non-cardiac causes of cough or breathing difficulty. An electrocardiogram (ECG) detects arrhythmias — particularly atrial fibrillation, which complicates CHF management and worsens prognosis. A blood pressure measurement may also be performed. Ensuring comprehensive diagnostics supports the most targeted and effective treatment plan — a principle central to proactive veterinary care.

The treatment of CHF in dogs is well-established and, when implemented effectively, can provide months to years of good quality life. Treatment involves a combination of medications, dietary modifications, and careful monitoring.

Core Medications

The standard medical management of CHF in dogs rests on three pillars, often referred to as the 'triple therapy':

• Furosemide (Frusemide) — a loop diuretic and the most important medication in acute CHF management. Furosemide removes excess fluid from the lungs and body by increasing urine production. In acute heart failure, it is given intravenously or intramuscularly for rapid effect. Once stabilised, dogs transition to oral furosemide, with the dose titrated to the lowest effective level that keeps the sleeping respiratory rate below 30 breaths per minute. Too much furosemide can cause dehydration and kidney damage; too little allows fluid to re-accumulate. Finding the right balance requires close collaboration between owner and vet
• Pimobendan (Vetmedin) — a positive inotrope (strengthens heart contractions) and vasodilator (relaxes blood vessels) that has revolutionised CHF management in dogs. Multiple studies have shown that pimobendan significantly extends survival in dogs with both MMVD-related and DCM-related CHF compared to older treatments. It is typically given twice daily on an empty stomach. Pimobendan is considered essential in the treatment of canine CHF and should not be discontinued without veterinary guidance
• ACE inhibitors (benazepril or enalapril) — these medications block the renin-angiotensin-aldosterone system, a hormonal cascade that is abnormally activated in heart failure and contributes to fluid retention, blood vessel constriction, and progressive heart damage. ACE inhibitors provide modest but meaningful survival benefits and are well-tolerated by most dogs

Additional Medications

• Spironolactone — a potassium-sparing diuretic and aldosterone antagonist. It provides additional neurohormonal blockade and a mild diuretic effect, complementing furosemide. Spironolactone has been shown to improve survival in dogs with CHF when added to standard therapy
• Antiarrhythmic drugs — if atrial fibrillation or other dangerous arrhythmias develop, medications such as diltiazem, digoxin, or mexiletine may be added to control heart rate and rhythm
• Sildenafil — may be prescribed for dogs with pulmonary hypertension, a complication of chronic left-sided heart failure

Dietary Management

Moderate dietary sodium restriction helps reduce fluid retention. This does not mean a drastically salt-free diet — extreme sodium restriction can actually worsen neurohormonal activation. Instead, avoiding high-sodium treats (cheese, deli meats, many commercial treats) and feeding a good-quality commercial diet with appropriate sodium levels is sufficient for most dogs. Maintaining adequate caloric intake is crucial, as cardiac cachexia — muscle wasting driven by heart failure — can significantly impact quality of life. Adding omega-3 fatty acids may help combat muscle wasting and reduce inflammation.

Owners are the front line of CHF management. Your observations at home are the most important factor in detecting changes early and adjusting treatment before a crisis develops.

The Sleeping Respiratory Rate — Your Most Valuable Tool

The single most important thing you can do for a dog with CHF is to monitor their sleeping respiratory rate (SRR). When your dog is sleeping peacefully (not dreaming or twitching), count the number of breaths over 30 seconds and multiply by two to get breaths per minute. A well-managed dog with CHF should have an SRR consistently below 30 breaths per minute — and ideally below their established personal baseline. If the SRR rises above 30 or shows a consistent upward trend over two to three days, contact your vet — this often indicates fluid re-accumulation before other symptoms become apparent. Many veterinary cardiologists now recommend smartphone apps specifically designed for SRR tracking.

Additional Home Monitoring

• Cough frequency — note how often your dog coughs each day, and whether coughing worsens at night or when lying down
• Appetite and water intake — decreased appetite may indicate worsening failure or medication side effects. Increased water intake is expected with furosemide but excessive thirst warrants mention
• Energy and activity level — track willingness to walk, play, and interact. A sudden decline in energy is significant
• Abdominal girth — if your dog is at risk for right-sided failure or ascites, measuring the belly circumference at the same point each day can detect fluid accumulation early

Quality of Life

Living well with CHF means maintaining the activities your dog enjoys while respecting new limitations. Gentle, regular exercise (short walks, calm play sessions) is generally beneficial — it maintains muscle tone and mental engagement. Avoid strenuous exercise, extreme heat, and overexcitement. Keep a consistent daily routine, as dogs with CHF often do better with predictability. Ensure all family members understand and follow the medication schedule. Senior pet care principles are particularly relevant for dogs managing CHF alongside the normal changes of ageing.

Prognosis

The prognosis for dogs with CHF has improved dramatically with modern treatment. Dogs with MMVD-related CHF receiving optimal triple therapy typically survive a median of nine to eighteen months after their first episode of heart failure — and some individuals live two to three years or more. Dogs with DCM-related CHF generally have shorter survival times, though pimobendan has improved outcomes significantly compared to previous decades. Stage D (refractory) heart failure carries a more guarded prognosis, but even these dogs may be stabilised for weeks to months with aggressive therapy adjustments.

Regular veterinary rechecks — typically every two to four months, with chest X-rays and blood work to monitor kidney function and electrolytes — allow your vet to fine-tune medications and catch complications early. Together with diligent home monitoring, comprehensive care planning, and a strong vet-owner partnership, dogs with CHF can continue to enjoy meaningful, comfortable lives.