Reviewed and fact checked by Bruce Whittle, DVM
While heart conditions are relatively uncommon in dogs, they can present serious health problems when they do occur. The cells of the body need oxygen and nutrients and require waste products to be removed, and the heart is the pump that makes this happen. When the heart is weakened or inefficient, the body’s cells suffer due to unmet needs. Most common heart conditions in dogs have similar clinical signs, so advanced testing—such as radiography (X-rays), echocardiography (ultrasound), and electrocardiogram (ECG)—is often necessary for a specific diagnosis.
Congestive Heart Failure
Congestive heart failure is a condition seen in older dogs and is characterized by the heart muscle being unable to pump blood forward efficiently, allowing pressure to build up in the blood vessels leading to the lungs. The higher pressure in the lungs causes fluid to leak out of blood vessels and into lung tissue, creating a condition similar to pneumonia. In more advanced stages, fluid may also accumulate in the abdominal cavity due to a backup of blood returning to the heart. Common signs of congestive heart failure include persistent coughing, panting without exercise, reduced energy, and a swollen abdomen in advanced cases. Your veterinarian will likely take radiographs and perform an ultrasound of the chest to evaluate heart function and may collect a blood sample to test for other conditions that cause similar signs. While congestive heart failure cannot be cured, it can be managed. Dogs with this condition often require lifelong medications to improve heart muscle contraction and decrease fluid buildup in the lungs. When combined with an appropriate diet, these treatments can significantly improve a dog’s quality of life.
Congenital Heart Defects
Common congenital heart defects include:
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Ventricular septal defect (VSD)
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Patent ductus arteriosus (PDA)
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Aortic stenosis
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Pulmonic stenosis
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Atrial septal defect
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Mitral valve dysplasia
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Tetralogy of Fallot
Congenital defects are anatomical anomalies present at birth. These conditions may or may not be genetic. VSD is characterized by a hole between the two lower chambers of the heart, while atrial septal defect is a hole between the two upper chambers. Both allow blood to flow backward from the stronger left side of the heart to the weaker right side. PDA occurs when a blood vessel that bypasses the lungs before birth fails to close normally. Pulmonic and aortic stenosis refer to the narrowing of the large blood vessels leaving the heart. Mitral valve dysplasia involves abnormal valve leaflets from birth that allow blood backflow. Tetralogy of Fallot is a complex condition involving four defects at once. Clinical signs of congenital heart defects generally resemble those of congestive heart failure and include exercise intolerance, coughing, panting, and sometimes a bluish tint to the mouth’s mucous membranes. Echocardiography is often performed by specialists for diagnosis. Fortunately, some congenital defects are treatable with surgery.
Mitral Valve Disease
Mitral valve disease involves thickening of the heart valves between the upper and lower chambers on the left side of the heart. Unlike mitral valve dysplasia, which is present at birth, mitral valve disease develops over time. Clinical signs are similar for both conditions. Normally, the valves prevent backflow of blood; when diseased or thickened, blood flows backward in the heart, reducing circulation to the rest of the body and causing similar clinical signs to other heart conditions. Medical management can improve quality of life.
Dilated Cardiomyopathy (DCM)
Dilated cardiomyopathy is a progressive condition in which the heart enlarges and the heart muscle weakens. It most often affects middle-aged and older, large-breed male dogs. Proposed causes include genetics, viral infections, nutritional deficiencies, or idiopathic origins (unknown cause). Doberman Pinschers and Boxers may have a genetic predisposition to DCM. Diets containing peas, lentils, or potatoes as major ingredients have been suspected as contributing factors, though research is ongoing.
Heartworm Disease
Heartworm disease is a serious parasitic infection caused by nematode worms spread by mosquitoes. Although more common in certain regions, dogs traveling to these areas can become infected and later spread the parasite to other dogs. Heartworm infection is relatively easy to diagnose with a blood test, and effective preventive medications are available. Early treatment is most successful before severe heart and lung changes occur. Advances in diagnostics, prevention, and treatment have made this once-difficult disease much more manageable.
Myocarditis
Myocarditis is inflammation of the heart muscle. In dogs, it is usually associated with infections by viruses, bacteria, fungi, or parasites, as well as autoimmune disease, toxins, hemodynamic shock, or heat stroke. Causes may include Staphylococcus bacteria, Parvovirus, West Nile Virus, Borrelia burgdorferi (Lyme Disease), Toxoplasma, and roundworms, among others. Any over-stimulation of the immune system can potentially lead to myocarditis. Veterinarians may suspect the condition based on fever or a heart murmur, but these signs are nonspecific. A heart muscle biopsy is needed for definitive diagnosis, though it is rarely performed due to risk. Unfortunately, the prognosis for myocarditis is generally poor.
Conclusion
Although fortunately uncommon, many dogs do experience heart conditions, whether congenital or acquired later in life. Because clinical signs are similar for most heart conditions, advanced testing is often necessary. Your veterinarian may refer your dog to a veterinary cardiology specialist for evaluation. Early diagnosis and intervention can be critical for successful treatment and improved quality of life.
