Evaluation of red blood cell distribution width in cats with hypertrophic cardiomyopathy

Background Red blood cell distribution width (RDW) is a measurement of variability in circulating erythrocytes size, and has recently been shown to correlate with prognosis in a variety of human diseases, including acute and chronic heart failure. Objectives To determine if RDW differs between healthy controls, cats with hypertrophic cardiomyopathy (HCM) without congestive heart failure (CHF) and cats with HCM and CHF, and to evaluate whether RDW values at presentation can provide useful prognostic information in cats with HCM. Animals Retrospective single-centre study. Seventy-three cats diagnosed with HCM by echocardiography and 30 healthy controls presented to a veterinary teaching hospital between October 2006 and April 2013 were included. Physical examination, haematology and echocardiographic data obtained on one single visit were retrospectively reviewed and compared between three groups: controls, cats with HCM without CHF, and cats with HCM and CHF. Outcome data were obtained from clinical records or referring veterinarians. Univariable and multivariable survival analyses were performed. Results Red blood cell distribution width was significantly greater in cats with HCM and CHF compared with cats with HCM without CHF, and the controls. It was also significantly associated with cardiac mortality in univariable survival analysis, and this association remained significant in multivariable survival analysis after controlling for the effect of CHF, left atrial size, left ventricular systolic function, haematocrit and pro-thrombotic state. Conclusions A higher RDW may be seen in cats with CHF and is an independent predictor of cardiac death in cats with HCM without concurrent non-cardiac-related illness.