Dilated cardiomyopathy (DCM) is the most common disease affecting the heart muscle in large- and giant-breed dogs. It can also occur in medium-breed dogs, though this is less common. It is less frequently observed in cats. While there is no cure for DCM, its signs and symptoms can be managed in many patients. Vigilant monitoring of the pet’s condition and consistent medication administration are crucial to maximizing your pet’s quality and length of life.
To better understand how the changes that occur with DCM affect the normal function of your pet’s heart, please see the The Normal Heart
While diseases affecting heart valves and other organs can indirectly affect the heart, DCM is a disease of the heart muscle itself. We do not know the precise cause of DCM, but it is thought to be a genetic disease, based on the fact that it is commonly seen in some breeds such as Doberman pinscher, Great Dane, Irish wolfhound and Newfoundland. The inciting cause is thought to be related to changes in proteins at the cellular level. These changes weaken the muscle cells of the heart. Researchers are continuing to find genes that are associated with the disease, but right now, there is no way to predict which animals will develop this disease.
In patients with DCM, the heart loses its ability to contract effectively. The muscle itself is weak, and so cannot push all the blood out of the heart and into the circulation during systole. Therefore, some blood stays in the chambers of the heart. Over time the heart tries to expand its chambers to both accommodate the blood “left behind” and to try to squeeze more forcefully. This expansion of the heart muscle is also called dilatation, which is where part of the name for DCM comes from.
With progression of the disease, more blood is left in the heart with each heartbeat, and more dilation occurs. This stretching can even lead to a gap between the leaflets of the heart valves. Think of a pair of swinging doors; now imagine keeping the doors the same size but pushing out the door frame on all sides. The gap in the middle represents a gap in the valve leaflets. When this occurs, blood can flow backwards across this leaky valve, resulting in a condition known as “insufficiency” or “regurgitation.” This adds to the heart’s workload and worsens the dilatation. In DCM, the heart becomes enlarged, weak, and “floppy”—unable to pump blood around the body.
Treatment and Prognosis
Although dogs with DCM can experience a relatively long period of time without symptoms, eventually all affected dogs will develop heart failure. Treatment of DCM involves managing the signs of heart failure when they develop and includes drugs such as vasodilators (ACE-i), diuretics (furosemide) and drugs supporting the pump function of the heart (digoxin, pimobendan). If your pet also has an abnormal heart rhythm (arrhythmia), we might also prescribe medications to improve the way the heart beats. These include drugs such as sotalol or diltiazem.
With the Heart Failure Clinic program, we can teach you to monitor your pet’s condition for signs of heart failure. By following the monitoring and medication guidelines outlined in your personalized Heart Failure Diary, we have the best chance of helping your pet lead as long and fulfilling a life as possible. While there is no cure for DCM, even dogs that are very ill can often benefit from medication. Survival times can range from few to several month with appropriate therapy.