Table 1 . Definitions of cardiomyopathy phenotypes [ 3 ] with echocardiographic examples [ 9 , 10 ] .
Phenotype Definition Example
Hypertrophic cardiomyopathy ( HCM )
Increased left ventricular wall thickness with a non-dilated left ventricle .
Restrictive cardiomyopathy ( RCM )
Dilated cardiomyopathy ( DCM )
Endomyocardial form : Fibrous tissue is visible macroscopically ( endocardial scar ), which usually bridges the interventricular septum and left ventricular free wall , and may cause fixed , mid-left ventricular obstruction and often apical left ventricular thinning or aneurysm ; left atrial or bi-atrial enlargement is generally present . Myocardial form : Normal left ventricular dimensions ( including wall thickness ) with left atrial enlargement or biatrial enlargement .
Left ventricular systolic dysfunction ( reduced contractility ) is characterised by a progressive increase in ventricular dimensions , normal or reduced left ventricular wall thickness , and atrial dilation .
Arrhythmogenic cardiomyopathy ( AC ), also known as arrhythmogenic right ventricular cardiomyopathy ( ARVC ) or dysplasia ( ARVD )
Severe right atrial and right ventricular dilation , often with right ventricular systolic dysfunction and wall thinning . The left side of the heart may also be affected . Arrhythmias and rightsided congestive heart failure are common .
Non-specific phenotype
A cardiomyopathy phenotype that is not adequately described by the other categories .
Table 2 . Stages of feline cardiomyopathy .
Stage
Findings
A
B1 ( low risk of imminent heart failure or aortic thromboembolism )
B2 ( high risk of imminent heart failure or aortic thromboembolism )
Currently healthy patients that show no clinical signs but are predisposed to cardiomyopathy ( e . g . at-risk breeds ).
Asymptomatic patients with cardiomyopathy , with normal atrial size or mild atrial enlargement .
Asymptomatic patients with cardiomyopathy , with moderate to severe atrial enlargement .
C Patients that have signs of heart failure or aortic thromboembolism , whether current or resolved with treatment .
D
Patients with signs of heart failure that is no longer responsive to standard therapy .
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