Preclinical dilated cardiomyopathy and advances in treatment

Dilated cardiomyopathy (DCM) is the most commonly acquired cardiac disease in large and giant breed dogs. It is an important cause of cardiac morbidity and mortality, and Doberman Pinschers are one of the most commonly affected breeds. The two main reasons for death with DCM are refractory congestive heart failure (CHF) and sudden death caused by ventricular arrhythmias. Previously, treatment regimens started only when the patient presented with signs of heart failure. However, the pimobendan randomised occult DCM trial to evaluate clinical symptoms and time to heart failure (PROTECT) study (Summerfield et al, 2012) showed that the administration of pimobendan at the preclinical phase of DCM in Dobermans prolonged time to the onset of clinical signs, and extended survival.

Cardiomyopathy is a term applied to any cardiac disorder caused by myocardial dysfunction. In primary cardiomyopathies, the cause of the myocardial disease is unknown, and so the diagnosis of DCM is often one of exclusion (Dukes-McEwan, 2010). DCM is characterised by four-chamber dilatation and poor systolic function. Systolic dysfunction occurs because of an impairment of myocardial contractility, leading to activation of compensatory neurohormonal mechanisms (the adrenergic and renin–angiotensin–aldosterone systems), which result in fluid retention and progressive dilation of the ventricle. This dilation often also causes distortion of the mitral valve apparatus. This results in mitral regurgitation, which increases the potential for heart failure owing to increased pulmonary venous pressure and/or atrial arrhythmias. Some dogs remain in sinus rhythm, but tachyarrhythmias such as atrial fibrillation can also be seen. Ventricular arrhythmias can also be present, either as uniform or multiform ventricular premature complexes (VPCs), couplets, triplets, ventricular runs or ventricular tachycardia.