Heart failure is a life-threatening condition that is the result of a weakened heart muscle. When the heart muscle is weakened, it is unable to provide adequate circulation, and fluid buildup can occur, most notably in the lungs. But what causes the heart muscle to weaken? Read on to learn the 4 most common causes of heart failure in dogs.
1. Degenerative Valve Disease
Degenerative Valve Disease — also known as chronic valvular disease , endocardiosis, valvular regurgitation, or valvular insufficiency — is the most common cause of heart failure, and accounts for approximately 75 percent of cardiovascular disease in dogs. It is most common in toy and small breeds, and it is characterized by the degeneration of cardiac valves.
With this condition, the mitral and tricuspid valves are usually affected. The valve leaflets thicken and become deformed, and the free edges of the valves can no longer connect. These and other changes to the cardiac valves can cause them to leak, which allows blood to flow backward into the atrium of the heart. This regurgitation increases the blood pressure in the atrium and causes enlargement of the heart.
The greatest indication of degenerative valve disease is a loud heart murmur. Heart failure caused by degenerative valve disease will also likely cause coughing, rapid breathing, shortness of breath, fainting, lethargy, lack of appetite, and weight loss.
2. Dilated Cardiomyopathy
Dilated Cardiomyopathy — or DCM — is an acquired disease of the heart muscle. With DCM, the muscles of the lower heart chambers are no longer able to contract normally. Since the muscles cannot effectively pump blood out of the heart, blood will begin to back up within the heart and within the pulmonary veins that are connected to the heart. This results in an enlargement of the heart.
DCM is most common in large and giant breed dogs, especially males. Predisposed breeds include Doberman Pinschers, Dalmatians, Great Danes, Boxers, Newfoundlands, Cocker Spaniels, and Portuguese Water Dogs, and the specific cause of DCM can vary depending on the breed.
The symptoms of heart failure associated with dilated cardiomyopathy include loss of appetite, pale gums, coughing, difficulty breathing, increased heart rate, weakness, and fainting. A swollen abdomen may also be seen in some cases.
3. Congenital Heart Disease
Congenital heart disease is caused by heart defects that have been present since birth. Common defects include valve narrowing, valve malformations, abnormal openings between heart chambers, patent ductus arteriosus (a condition in which the ductus arteriosus — a blood vessel — does not close), and Tetralogy of Fallot (an abnormality that results in insufficiently oxygenated blood being pumped into the body).
The majority of dogs with congenital heart disease die within the first year. Those who survive are likely to show symptoms such as stunted growth, difficulty with exercise, and fainting. With these dogs, heart failure can occur suddenly and without warning.
4. Heartworm Disease
Heartworm disease is caused by parasites that are transmitted via a bite from a mosquito. The arteries that carry blood from the heart become plugged up with worms, and the heart has to pump hard against the pressure of the obstruction. This is what is referred to as pulmonary hypertension, and some hearts may be strong enough to handle it, and some may not.
If worms begin backing up into the heart from the arteries, the heart will have to work even harder because there will be less space in the pumping chamber for blood. In many cases, the heart just can’t keep up, and heart failure will occur.
Heart failure can happen when the heart muscles thicken due to overwork and arrhythmia (abnormal heart rhythm) develops. It can also happen when the heart muscles become too weak to function, resulting in the accumulation of fluid in the chest and abdominal cavities. In these cases, the dog may exhibit difficulty breathing and/or the appearance of a pot belly.
Prevention and Treatment of Heart Failure in Dogs
The best way to prevent heart failure is to treat the underlying cause before it progresses. A yearly visit to the veterinarian helps to ensure that problems are identified before they become severe.
If your dog does develop heart failure, it is typically treated with medication, like Vetmedin for dogs, and changes to diet. Medications can improve overall heart function and help prevent fluid buildup. Switching to a low-sodium diet can also keep fluid from accumulating.
Your dog’s chances of survival will ultimately depend on their specific condition and how quickly treatment is sought.