Assessment of left ventricular systolic function by strain imaging echocardiography in various stages of feline hypertrophic cardiomyopathy.

BACKGROUND: Diastolic dysfunction occurs in many cats with hypertrophic cardiomyopathy (HCM). Less is known about systolic function in various stages of HCM. Myocardial strain analysis by tissue Doppler imaging (TDI) is a noninvasive echocardiographic method to assess systolic function that has not been reported previously in cats.

OBJECTIVES: To evaluate systolic function in various stages of feline HCM by measurement of myocardial strain.

ANIMALS: Two hundred and sixty-three cats.

METHODS: Cats were classified by echocardiography into one of the following groups: clinically healthy (control) group (n=160), mild HCM (n=22), moderate HCM (n=39), and severe HCM (n=42). Peak myocardial strain, measured by TDI in the basal and midventricular segment of the interventricular septal wall (IVS) and the left ventricular posterior wall (LVPW), was compared among different HCM and control groups.

RESULTS: Whereas conventional echocardiography demonstrated an apparently normal or supernormal contractile state based on percentage of fractional shortening, myocardial strain in all HCM groups was significantly decreased compared with the control group (P<.001). There was a significant correlation between strain values and wall thickness (P<.001). Reproducibility of strain analysis was 6.3% in the IVS and 9.7% in the LVPW.

CONCLUSIONS AND CLINICAL IMPORTANCE: Myocardial strain analysis is a new, valuable, and reproducible method in cats. This method allows noninvasive detection of abnormal systolic deformation in cats with HCM despite apparently normal left ventricular systolic function as assessed by conventional echocardiography. The abnormal systolic deformation already was present in mild HCM and increased with progressive left ventricular concentric hypertrophy.