Feline Myocardial Disease: 1: Classification, Pathophysiology and Clinical Presentation

Abstract

Practical relevance Myocardial disease (cardiomyopathy, CM) is the most common cardiac disorder observed in cats. The disease usually leads to the development of congestive heart failure, which is the major cause of cardiac mortality. Arterial thromboembolism is another severe outcome often associated with feline CM. Patient group The median age of cats when diagnosed with a form of CM is 5.5 years (range 4 months to 16 years). The disease appears to be equally distributed between males and females and among different breeds, although a genetic predisposition of some pedigrees should be taken into consideration (ie, Maine Coons, Ragdolls, Norwegian Forest cats). Audience General practitioners, as well as specialists in small animal medicine, cardiology and pathology, have to deal with CM on a regular basis. Clinical challenges The diagnosis and clinical management of myocardial disease in cats represents one of the greatest challenges in veterinary cardiology. Although several attempts have been made to standardise the classification of CM, both in humans and cats, some disagreement still exists among cardiologists. Classification criteria are continuously evolving as the aetiology of myocardial disease becomes better understood. It is now widely appreciated that, for a given aetiology, there may be a spectrum of phenotypes ranging from restrictive to dilated. Diagnostics The diagnosis and classification of CM is primarily based on echocardiographic criteria. However, phenotypic variability is substantial, even within a single form of CM, and this often causes subjective interpretations of echocardiographic diagnosis, especially by inexperienced echocardiographers. Post-mortem examination is an alternative approach to diagnosis. Evidence base The clinical management of feline myocardial disease is even more controversial, especially in the light of recent clinical studies. This two-part article reviews the literature to date, discusses various manifestations of the disease in cats and offers a critical, and often controversial, approach to diagnosis and management.