DCM- Canine Dilated Cardiomyopathy

 

DCM is the most common primary cardiovascular disease in dogs, taking up to 50% of all cases. The other half would cover HCM, Heartworms, Restrictive cardiomyopathy and other unclassified cardiomyopathies.

DCM seems to have a prevalence for large dogs, such as Doberman, Newfoundlands..etc., but also Cocker spaniels and other smaller breeds can be affected.

 

DCM is characterized by a markedly enlarged heart. The myocardium appears pale, soft and flabby. The left side (atrium and ventricle) can dominate, but also all chambers can be grossly dilated. The ratio of left chamber wall thickness and chamber diameter gets a lot smaller

Proposed causes for DCM are viral infection (parvovirus in rare cases), myocardial toxins,

microvascular hyperactivity,

nutritional deficiency, (-> certain taurine deficiencycauses or contributes to the development of myocardial failure, the mechanism is still unknown. L-carnitine with its role as a main fat shuttle for long chained fatty acids in the heart muscle, seems to play a role in causing DCM as well. But thereís been no real proof yet, also carnitine supplementation does not beware of sudden death and pre-existing cardiac arrhythmias are not abolished. Carnitine supplementation is said to have a moderate beneficial effect on the myocard.)

 

persistent or recurrent tachycardia (due to hyperthyroidsm, atrial fibrillation-> rise in demand for oxygen, while not having time to support the heart itself), and a large number of genetic abnormalities.

 

 

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The predominant physiologic abnormality in DCM patients is impaired systolic ventricular function caused by declining myocardial contractility. (reduced ventricular pressure and increased end systolic volume.) Diastolic ventricular function is also abnormal in DCM dogs. DCM leads to: congestive heart failure (CHF), systemic arterial hypotension, valvular (mitral and tricuspid) insufficiency, cardiac arrhythmia, exercise intolerance and weakness.

 

 

 

Clinical presentation :

 

Weak and rapid pulses are detected in the majority of DCM dogs, as well as rales, crackles and increased bronchovascular lung sounds in dogs with left-side heart failure. Dogs having a right side or biventricular heart failure, youíll probably find hepatomegaly, ascites, jugular venous distention and jugular pulses. In contrast to other species, peripheral edema occurs rarely in dogs. In dogs being symptomatic for several month, you might find weight loss and muscle atrophy. And of course youíre mostly able to hear a heart murmur, or gallop sound while auscultation. On laboratory findings there can be a moderate rise of AP without an increase of ALT and AST, a mild reduction in globuline with no decline in serum albumin. A slight increase of creatinine and urea.

DCM is not attached to thyroidal illness, but thyroid function in DCM dogs should also be monitored.†† On ECK the QRS-complex seems to be widened, as sign of left ventricle enlargement, the p-wave is enlarged when the right side is enlarged, too. Doberman Pinschers and boxers develop arrhythmias more often than any other breed. Chest x-rays should always be taken, to evaluate heart size and to determine the presence/severity of pulmonary edema.

Echocardiography is the best way to examine DCM, since youíre able to define the extent of systolic and diastolic dysfunction and to exclude any other causes, such as aquired valvularor pericardial disease .

 

Therapy

 

The ultimate treatment goal is to reverse the underlying disease process before irreversible myocardial damage has occurred. Inasmuch in most affected dogs the causes are not known, treatment goal is to improve quality of life and to minimize mortality. Drugs used to treat dogs with DCM include digoxin, other inotropic drugs, diuretics, ACE-inhibitors, vasodilators and anti-arrhythmic drugs, such as b-adrenergic-receptor blockers and calcium antagonists. In 2 cases thereís an opportunity for cure:

a)     persistent or recurrent tachycardia

b)     or taurine deficiency are the causes for DCM

 

Pulmonary edema should always be treated first, with furosemides and/or sodium nitroprusside.

To strengthen the heart, dobutamine is a good choice, but itís not to be mixed with sodium nitroprusside.

 

Prognosis:

 

Owners should be advised, that survival time, even with optimal therapy, are highly variable from one patient to the next. In general you could say, that the severer the problem is, the worse is the prognosis.

 

 

 

 

Mx, 20-03-2002