Congestive Heart Failure in Dogs
The importance of good dog heart health cannot be underestimated. Without a heart there is no life, it is as simple as that.
What Is Heart Failure in Dogs?
Heart failure in dogs is a syndrome that occurs then the heart of the sac surrounding the heart (pericardial sac) becomes so severe that the heart can no longer pump blood effectively to maintain perfusion to tissues in the body.
Different conditions can result in forward or backward failure. Forward failure is a term used when the heart cannot pump enough blood into the outflow tracts (aorta and pulmonary artery) to maintain a normal arterial pressure. Backward failure occurs when there are elevated atrial pressures (first heart chamber which pumps blood into the ventricles of the heart) resulting in what is more commonly recognised as congestive heart failure (CHF).
What Common Conditions Cause CHF And Forward Failure Which May Be Diagnosed?
Congestive Heart Failure
- Degenerative mitral valve disease
- Severe tricuspid regurgitation (right hand side of the heart)
- Patent ductus arteriosus
- Dilated cardiomyopathy (DCM)
- Slowly developing pericardial effusion (idiopathic haemorrhagic)
- Cardiac arrhythmia
Forward Failure
- Aortic stenosis
- Pulmonic stenosis
- Rapidly developing pericardial effusion (haemorrhage due to haemangiosarcoma
Should your pet be diagnosed with one of the above conditions your vet will discuss a plan of action as to how is best to manage and treat the condition. It is important to bear in mind that causes of CHF can also cause forward failure if they become more advanced or if left untreated.
What Clinical Signs Are Associated with Canine Heart Failure?
The heart is divided into 4 chambers; the right and left atria and the right and left ventricles. Larger veins from the body and lungs drain into the right and left atria respectively, and when distended they pump blood into the ventricles.
The more muscular ventricles then eject blood into the major arteries; the right side to the lungs and the left side to the aorta which delivers oxygenated blood from the lungs to the rest of the body. Depending on which side of the heart is affected they may be accompanied by different clinical signs.
Signs associated with left-sided heart failure include:
- Coughing
- Fast or difficulty breathing
- Distended abdomen with fluid (known as ascites) in advanced stages
Forward heart failure can be associated with the following clinical signs:
- Weakness
- Exercise intolerance
- Collapse with loss of consciousness (termed syncope)
- Cold extremities
- Pale mucous membranes, typically seen on the gums
- Hypothermia
How Is Heart Failure in Dogs Diagnosed?
If your pet has a relevant history accompanied by the clinical signs as mentioned above then your vet may recommend further diagnostic imaging to characterise the type of cardiac disease present. Most dogs affected tend to develop clinical signs over the age of 5 years.
Degenerative mitral valve disease (DMVD) is the most common acquired disease (75%) of dogs and prevalence increases with age. The condition commonly affects older small breed dogs (<25kg); Cavaliers (CKCS), terriers, poodles, and male's area affected earlier in some breeds (CKCS).
Degenerative mitral valve disease is characterised by structural changes the heart valve between the left atria and ventricles and may be accompanied by clinical signs or a heart murmur may be detected as an incidental finding on when your pet is given a clinical exam.
Due to the degenerative nature of the disease, your dog may present with a low-grade heart murmur initially which may increase in intensity as your pet becomes older. Early detection is important to commence treatment as soon as possible to slow down the disease progression.
Should a heart murmur consistent with DMVD be detected, particularly if similar intensity to the normal heart sounds, chest radiographs and an ultrasound of the heart (echocardiogram) will help with staging the disease and direct appropriate treatment for your pet.
Enlargement of the heart with increased size of the left atrium is a consistent finding, although echocardiography is gold standard to confirm the diagnosis by examining the mitral valve leaflets.
Stages of DVMD are listed below:
Stage B1: No cardiomegaly with no clinical signs (includes the majority of cases)
Stage B2: Cardiomegaly detected with no accompanying clinical signs
Stage C: Signs of heart failure (forward or backward failure)
Stage D: Signs of heart failure that are refractory to treatment
What Is the Treatment for Heart Failure In Dogs?
Prior to the onset of cardiomegaly, therapeutic intervention is controversial as the weight of evidence does not support initiation of therapy in early disease.
Treatment with Pimobendan (Vetmedin) is often indicated when your pet is diagnosed with stage B2 heart disease (if they have a big heart). This leads to significant prolongation to heart failure up to 1 year (EPIC study). This is attributable to improving outflow from to the left ventricle and allow heart to work with smaller volume whilst improving contractility and relaxation of the heart easing congestion.
Once heart failure has developed (>stage C) best evidence supports a regimen of with the most strongly indicated being first (EPIC study):
- Diuretic (furosemide)*
- Pimobendan*
- ACE inhibitor
- Spironolactone
* must haves for treatment if on budget
Furosemide is a diuretic drug that helps reduce circulating fluid volume in the vascular system which helps reduce fluid accumulations in the lungs. Furosemide is indicated following the diagnosis which is based on obtaining radiographs of the chest.
Thereafter treatments tend to be dosed according to the most pressing clinical problems identified. Spironolactone is additional diuretic that can be used as adjunctive therapy in severe cases and ACE inhibitors work to inhibit an reduce formation of an enzyme angiotensin II resulting in dilation of the blood vessels and thus reducing the load on the heart.
Together we care for your dog’s heart
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Benefits
- Designed specifically with canine heart health in mind
- Vital part of a good cardiovascular health care plan for dogs
- Healthier heart improves quality of life and life expectancy
When Should My Dog Be Re-Examined?
Dogs being treated for CHF should be examine 1-2 weeks after initial presentation and after commencing treatment. Thereafter they should have regular check-ups every 3-4 months for your vet to fully evaluate response to treatment and the severity of heart disease to monitor progressions and adjust treatment regime if indicated.
Useful tests such as measuring electrolytes, urea and creatinine (to determine kidney function and filtration rate) and blood pressure may be taken to evaluate effects on the rest of the body. Your vet is also likely to recommend radiographs to check for fluid in the lungs (termed pulmonary oedema) to determine whether to commence further treatment to relieve symptoms. Signs of pulmonary oedema are most likely to manifest as a shortness of breath, persistent coughing and exercise intolerance.
Cases of suspected forward failure are commonly referred to a specialist in cardiology to confirm the diagnosis and for recommendations for appropriate treatment. This is most likely to entail more an ultrasound of the heart called and echocardiogram to assess the pericardial sac surrounding the heart and the diameter of the major arterial outflow tracts.
References:
(1) Top 100 consults in small animal practice
(2) EPIC study, Adrian Boswood, Lecturer in cardiology RVC