CONDITION
Congestive Heart Failure in Dogs
Why this matters now
Congestive heart failure in dogs typically develops as the end-stage manifestation of progressive cardiac disease. Myxomatous mitral valve disease (MMVD) is the most common underlying cause in small to medium breeds, while dilated cardiomyopathy (DCM) predominates in large and giant breeds. The transition from compensated heart disease — where the heart maintains adequate output through compensatory mechanisms — to decompensated heart failure may occur gradually or may be precipitated by factors such as arrhythmia development, dietary indiscretion, concurrent illness, or anaesthetic events. Most dogs that develop CHF are middle-aged to elderly, though breed-specific cardiomyopathies can produce heart failure in younger animals.
Heart failure follows a trajectory of progressive decompensation, though the rate varies considerably between individuals. Initially, neurohormonal compensatory mechanisms — activation of the renin-angiotensin-aldosterone system, sympathetic nervous system upregulation, and cardiac remodelling — maintain cardiac output at the expense of increased blood volume and cardiac workload. As these mechanisms become insufficient, fluid begins to accumulate. Left-sided failure produces pulmonary oedema (fluid in the lungs), while right-sided failure produces ascites (abdominal fluid), pleural effusion, and peripheral oedema. Many dogs develop biventricular failure over time. The condition is managed rather than cured, with the goal of controlling fluid accumulation, reducing cardiac workload, and maintaining quality of life for as long as possible.
Signals & patterns
Early signals
Coughing, particularly at night or when lying down
As pulmonary oedema develops or the enlarged heart compresses the left mainstem bronchus, a cough may emerge that is most noticeable during rest or recumbency. The cough may initially be soft and infrequent, easily dismissed as a throat-clearing sound, but tends to become more persistent as fluid accumulation increases.
Increased respiratory rate at rest
The resting respiratory rate (breaths per minute when the dog is calmly resting or sleeping) is one of the most sensitive indicators of early fluid accumulation in the lungs. Normal dogs typically breathe fewer than 30 times per minute at rest. A sustained increase above this threshold, particularly when trending upward over days, may indicate developing pulmonary congestion.
Reduced exercise tolerance
Dogs may begin tiring more quickly on walks, lagging behind on familiar routes, or showing reluctance to engage in activities they previously enjoyed. This reduced stamina reflects the heart's inability to increase its output sufficiently to meet the elevated oxygen demands of physical exertion.
Restlessness at night
Difficulty settling at night, frequent position changes, and apparent inability to find a comfortable sleeping position may reflect early respiratory discomfort. Some dogs prefer to sleep with their head elevated or in sternal recumbency rather than their usual position, as lying flat increases pulmonary venous pressure and worsens congestion.
Later signals
Laboured breathing and abdominal effort
As pulmonary oedema becomes more significant, breathing requires increased effort. The dog may show visible abdominal movement with each breath, flaring of the nostrils, or extension of the neck to straighten the airway. Breathing may appear rushed, shallow, and effortful even at rest.
Abdominal distension
Right-sided heart failure produces ascites — the accumulation of free fluid in the abdominal cavity. The abdomen may gradually enlarge, developing a pot-bellied appearance that contrasts with muscle wasting over the spine and hindquarters. The fluid may be detectable as a fluid wave on palpation.
Syncope or collapse
Fainting episodes may occur during exertion, excitement, or coughing fits as the failing heart cannot maintain cerebral perfusion during moments of increased cardiovascular demand. These episodes are typically brief, with rapid recovery, but indicate significant haemodynamic compromise.
Cyanosis
A bluish or greyish discolouration of the gums and tongue indicates severe hypoxaemia, where the blood oxygen levels have dropped to critically low levels. This sign reflects advanced pulmonary compromise and represents a significant escalation in the severity of the condition.
Click to read about the biological mechanisms
How this is usually investigated
Investigation of suspected heart failure combines physical examination findings with imaging and biomarker assessment to confirm the diagnosis, identify the underlying cardiac disease, and stage the severity of failure.
Thoracic radiography
Echocardiography
Cardiac biomarkers
Electrocardiography
Blood pressure measurement
Options & trade-offs
Management of congestive heart failure centres on reducing fluid accumulation, decreasing cardiac workload, and supporting remaining cardiac function. Treatment is lifelong and typically involves multiple medications that work through complementary mechanisms.
Diuretic therapy
Furosemide (frusemide) is the cornerstone of CHF management, promoting renal excretion of sodium and water to reduce circulating blood volume and relieve pulmonary congestion. Spironolactone may be added for its additional neurohormonal benefits and potassium-sparing diuretic effect. Torasemide represents an alternative loop diuretic with more consistent oral bioavailability.
Trade-offs: Diuretics are essential for controlling clinical signs but carry risks of dehydration, electrolyte imbalances (particularly hypokalaemia with furosemide alone), and prerenal azotaemia if doses exceed the patient's needs. The dose often requires escalation over time as the disease progresses and the kidneys develop diuretic resistance. Regular monitoring of kidney values and electrolytes helps guide dosing.
ACE inhibitor therapy
Angiotensin-converting enzyme inhibitors (enalapril, benazepril) counteract the overactivated renin-angiotensin-aldosterone system, reducing vasoconstriction, decreasing aldosterone-mediated fluid retention, and reducing cardiac workload. These medications have been shown to improve survival and quality of life in dogs with CHF.
Trade-offs: ACE inhibitors can cause hypotension, particularly when combined with diuretics, and may affect renal function. Regular monitoring of kidney values and blood pressure is important during treatment. The benefits of reduced cardiac workload and neurohormonal modulation generally outweigh these risks, but individual dose adjustment is necessary.
Positive inotropic therapy
Pimobendan is a calcium sensitiser and phosphodiesterase inhibitor that improves cardiac contractility while also providing vasodilatory effects (inodilator). It has become a standard component of CHF treatment, with evidence of improved survival time and quality of life. In certain conditions, it may be started before the onset of heart failure.
Trade-offs: Pimobendan is generally well-tolerated but may increase the risk of arrhythmias in some patients. Its positive inotropic effects may increase myocardial oxygen demand. The dual mechanism of action (improved contractility plus vasodilation) makes it particularly effective in heart failure but requires consideration of the overall drug regimen to avoid excessive haemodynamic effects.
Dietary modification
Moderate sodium restriction may help reduce fluid retention, though severe sodium restriction is generally avoided as it can activate neurohormonal systems that worsen heart failure. Maintaining adequate caloric and protein intake is important to prevent cardiac cachexia. Omega-3 fatty acid supplementation may provide anti-inflammatory and anti-arrhythmic benefits.
Trade-offs: Dietary changes must balance sodium restriction against palatability and adequate nutrition. Dogs with heart failure often have reduced appetite, so overly restrictive diets may worsen nutritional status. Commercial cardiac diets are formulated to balance these considerations but may not suit all patients.
Monitoring and dose adjustment
Home monitoring of resting respiratory rate provides owners with a practical tool for detecting early decompensation. Counting breaths per minute when the dog is calmly resting or sleeping, and tracking the trend over time, can identify fluid re-accumulation before clinical signs become severe, enabling earlier intervention.
Trade-offs: Effective home monitoring requires owner education and consistent technique. Respiratory rate can be influenced by factors other than heart failure, including pain, anxiety, temperature, and concurrent respiratory disease. The value of home monitoring lies in identifying trends rather than interpreting individual readings in isolation.
Common misconceptions
"Heart failure means the heart has stopped working"
Heart failure does not mean the heart has stopped or is about to stop. Rather, it means the heart's pumping capacity has declined to the point where it can no longer meet the body's demands without compensatory mechanisms causing fluid accumulation. Many dogs with heart failure continue to maintain reasonable activity levels and quality of life with appropriate medical management for months to years.
"Dogs with heart failure should not exercise at all"
While strenuous exercise may be inappropriate for dogs in heart failure, moderate, gentle activity is generally beneficial and helps maintain muscle mass, joint function, and mental wellbeing. The appropriate level of activity depends on the individual dog's clinical status and should be guided by the dog's comfort and willingness rather than arbitrary restrictions. Most dogs will self-limit their activity to an appropriate level.
"Heart failure only affects old dogs"
While heart failure is more common in older dogs due to the progressive nature of the most common underlying cardiac diseases, it can occur at any age. Congenital heart defects can produce heart failure in puppies or young adults, and certain breed-specific cardiomyopathies may cause heart failure in middle-aged dogs. The age at which heart failure develops depends on the specific cardiac disease and its rate of progression.
Understanding the principles of heart failure management can help owners participate meaningfully in their dog's care. Learning to count and track the resting respiratory rate provides a practical monitoring tool that can detect changes before they become clinically obvious. Recognising the signs of fluid re-accumulation — increased breathing rate, return of coughing, reduced energy, or reluctance to lie flat — enables earlier communication with the veterinary team. The progressive nature of the underlying heart disease means that treatment protocols typically require adjustment over time, and familiarity with the medications, their purposes, and their potential side effects supports informed decision-making as the management plan evolves.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS