Accessory left ventricular chamber in a cat: multimodality imaging description by cardiac magnetic resonance imaging and echocardiography.

A left ventricular accessory chamber is a complex and uncommon phenotype consisting in a subdivision of the left ventricle by a thick-walled muscle bundle or septum into two cavities. Multiple aetiologies such as congenital double-chambered left ventricle and acquired endomyocardial form of restrictive cardiomyopathy have been reported. The endomyocardial form of restrictive cardiomyopathy, owing to its structural heterogeneity, can present a similar phenotype to the congenital abnormality with intraventricular lesions bridging the ventricular septum and left ventricular free wall. Conventional echocardiography is the first-line, accepted, non-invasive imaging modality to investigate underlying cardiac disease but presents limitations for the overall assessment of myocardial tissue. This report describes the use of cardiac magnetic resonance imaging as an additional imaging modality to provide multiplanar morphological, structural, and functional information of the myocardium. In the presented images, hyperintensities on cardiac magnetic resonance imaging within the myocardium along with hyperechoic and heterogeneous myocardial tissue on echocardiography and elevated troponin I were suggestive of a presumptive acquired pathological process such as feline endomyocarditis-left ventricular endomyocardial fibrosis complex, rather than a sole congenital anomaly. Although the diagnosis was not confirmed, this case exemplifies the advantages of using complementary multimodality imaging in a cat presented with a left ventricular accessory chamber.