Dilated Cardiomyopathy, Canine - contd.
DCM generally is not curable, and spontaneous recovery is unlikely. The primary goals of treatment are to lessen clinical signs of heart failure and to prolong survival. Treatment of an individual dog is dictated by the severity of its signs at the time of diagnosis, and the presence or absence of changes such as congestive heart failure and arrhythmias. The primary drug to reduce fluid accumulation secondary to congestive heart failure is furosemide, marketed as Lasix. It can be used to treat acute, life-threatening fluid accumulation or to control and prevent congestive abnormalities in chronic settings.
Digoxin is used for several reasons in the treatment of DCM. It may help increase the heart's ability to contract and slow down the ventricular response rate in dogs with atrial fibrillation. Digoxin also blunts some of the neurological and hormonal responses to heart failure that lead to worsening of the condition. Drugs such as dobutamine, amrinone, and milrinone may be used to increase the heart muscle's ability to contract, but they are indicated primarily for short-term emergency situations.
Recently, the use of drugs called angiotensin converting enzyme, or ACE, inhibitors has been shown to benefit dogs with DCM by reducing the signs due to heart failure and improving exercise tolerance. ACE-inhibitors have many effects, including blood vessel dilation, which reduces the resistance the heart has to pump against. The drug also remodels the diseased heart muscle. Other types of blood vessel dilators can be used in the short-term or long-term treatment of DCM to reduce the load that the heart has to pump against to get blood to flow.
Other drugs control heart rhythm disturbances. Digoxin is commonly used in dogs with atrial fibrillation. Other anti-arrhythmic drugs, including procainamide, marketed as Procan, and mexiletine, marketed as Mexitil, are used for dogs with ventricular arrhythmias due to DCM.
L-carnitine is a compound that plays an important role in fatty acid metabolism and in neutralizing potential toxins in cells. Carnitine deficiency in the heart muscle has been shown to be potentially reversible in at least one family of boxers with DCM. Although the diagnosis of heart muscle carnitine deficiency is difficult, and the appropriateness of supplementation with l-carnitine for all dogs with DCM is unknown, such supplementation is not known to be harmful. L-carnitine supplementation can be considered for all dogs with DCM.
Another substance that may play a role in the treatment of DCM, particularly in cocker spaniels, is taurine. Taurine deficiency was found to be the most important factor associated with DCM in cats in the 1980's, and correction of cat food formulations to eliminate taurine deficiency resulted in the almost complete elimination of DCM as a major heart muscle disease in cats. However, the exact role of taurine in the treatment of DCM in dogs remains undetermined. Other substances, such as coenzyme Q-10, may also play a role in the treatment of this disease.
