Dilated cardiomyopathy: Look for multiple disease entities - DVM
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Dilated cardiomyopathy: Look for multiple disease entities


DVM360 MAGAZINE


The ECG may be normal or may demonstrate a variety of rhythm disturbances and chamber enlargement/conduction abnormality patterns.

Atrial fibrillation, characterized by a rapid, irregularly irregular narrow complex tachyarrhythmia with no P-waves, is common in dogs with DCM. Premature ventricular extrasystoles (VPCs) are common in dogs with DCM and may be associated with an increased risk of sudden death (depending on the severity and complexity of the arrhythmia). If left atrial enlargement is present, the P-wave may be wide (P-mitrale). Increased R-wave amplitude indicates left ventricular enlargement. A right axis shift may indicate a conduction abnormality or cardiomyopathy primarily effecting the right side of the heart.

Radiography Thoracic radiographs are useful for detecting and assessing the presence of congestive heart failure. DCM can be associated with left-sided CHF (pulmonary edema), biventricular failure (combination of pleural effusion and pulmonary edema), or right-sided CHF (ascites). Radiographic CHF is usually associated with cardiomegaly and venous congestion. Advanced DCM is unlikely if cardiomegaly is not present, although Doberman Pinschers may appear to have less cardiomegaly than other breeds with severe DCM.

Echocardiographic evaluation of dogs with DCM reveals varying degrees of myocardial dysfunction as evidenced by a decreased fractional shortening, increased end-systolic volume index and reduced ejection fraction. Hemodynamically significant chronic myocardial failure results in chamber enlargement (eccentric hypertrophy); therefore, allowing for larger volumes without significant increases in diastolic pressures.

Atrioventricular valvular insufficiency is common in cases with moderate to severe chamber enlargement. The jet of mitral regurgitation is typically centrally located in this scenario as compared to the typical eccentric jet seen with degenerative valve disease.

Therapy Therapy for DCM involves the use of drugs to relieve the signs of congestion, improve myocardial function, and blunt the compensatory mechanisms that continue to overload the failing heart. There is some suggestion that early administration of ACE inhibitors may delay the onset of clinical signs in dogs with occult DCM. Conventional therapy for symptomatic DCM involves the use of ACE inhibitors (enalapril or benazepril), diuretics (furosemide and spironolactone), and positive inotropic drugs (digoxin). Other therapies include the use of beta blockers (carvedilol), positive inotropic vasodilators (pimobendan), and nutritional supplementation (L-carnitine, taurine and omega-3 fatty acids). Although not readily available in the United States at this time (is available to veterinarians in Canada), pimobendan has been associated with significant increases in survival times for dogs with DCM. Unfortunately, the long-term prognosis for dogs with DCM is guarded with a greater than 90 percent mortality rate at one year after initial diagnosis.

Dr. Hoskins is owner of DocuTech Services. He is a diplomate of the American College of Veterinary Internal Medicine with specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200, or e-mail:
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Source: DVM360 MAGAZINE,
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