Dilated Cardiomyopathy - Feline Cardiomyopathies
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Overview
Dilated cardiomyopathy (DCM) is now an uncommon feline cardiomyopathy, representing ~10% of cardiomyopathies. Previously, DCM was associated with taurine deficiency. However, the discovery of this in 1987 led to supplementation of commercial feline diets with adequate taurine. The rare cases of taurine deficiency observed since then are generally the consequence of vegetarian, vegan or canine diets to cats. It is difficult to differentiate true DCM, which is a primary systolic failure of the myocardium, from other forms of cardiac pathology which may result in a 'DCM phenotype'. Examples include the end stage of undiagnosed valvular diases (mitral dysplasia), ischaemic myocardial disease (HCM) or sustained tachycardia (tachycardia-induced cardiomyopathy).
Pathophysiology
Reduced myocardial contractility, predominantly involving the left ventricle (LV), will result in reduced stroke volume and increased ventricular filling pressure.
Clinical Signs
Signalment
DCM is most commonly diagnosed in middle-aged and older cats. Cats are typically diagnosed at the end-stage phase of disease when they have clinical signs referable to heart failure.
Physical Exam
- May present with signs of systolic failure (low output failure;cardiogenic shock): hypotension, hypothermia, bradycardia, weak femoral pulses
- Murmurs are quiet or absent
- Gallop rhythm may be present
- Dyspnoea, tachypnoea with restrictive pattern (rapid, shallow breaths), muffled heart and ventral lung sounds (pleural effusion)
- Dyspnoea, crackles (pulmonary oedema)
- Ascites, hepatomegaly, jugular venous distension and jugular pulses, hepatojugular reflux (right-sided congestive heart failure)
- Arterial thromboembolism (ATE) is common
Diagnosis
Differential Diagnoses
The differentials for systolic myocardial failure in the cat include:
- Taurine deficiency-induced cardiomyopathy
- Idiopathic DCM
- Tachycardia - induced cardiomyopathy
- Severe volume overload (mitral insufficiency, large left to right shunt)
- Doxorubicin toxicity