Comparative study of myocardial function in cases of feline hypertrophic cardiomyopathy with and without dynamic left-ventricular outflow-tract obstruction

Abstract

In recent years, hypertrophic cardiomyopathy (HCM) in cats has become much more common in clinical practice due to improvements in diagnostic techniques and equipment performance. One phenotype is obstructive HCM with left ventricular (LV) outflow tract obstruction (DLVOTO). It has been reported that the presence or absence of DLVOTO does not affect long-term prognosis in cats with HCM. In this study, we evaluated and compared myocardial function in HCM-affected cats with and without DLVOTO using the two-dimensional speckle-tracking echocardiography. LV longitudinal strain of the endocardial, epicardial, and whole layer and LV circumferential strain of the epicardium were significantly decreased in all HCM-affected cats compared to healthy cats. However, these values were not significantly different between those with and without DLVOTO. In contrast, the endocardial and whole layers of LV circumferential strain were only significantly decreased in HCM-affected cats with DLVOTO compared to healthy cats. This could be attributed to the fact that the LV pressure load associated with DLVOTO affected the endocardial myocardium more in the LV endocardial layer, and that lower values of LV endocardial strain lowered the values of LV strain in the whole layer. In conclusion, our results suggest that LV myocardial function may have been more compromised in the HCM-affected cats with DLVOTO.

Keywords: cardiomyopathy; cat; myocardial function; speckle tracking echocardiography; strain.

Figure 1

Myocardial motion analysis results of endocardium by 2D-STE method (representative data). LV-SL, peak systolic strain in the longitudinal direction at left ventricles; LV-SC, peak systolic strain in the circumferential direction at left ventricles. Arrows indicate the peak of the endocardium.

Figure 2

Results of longitudinal strain by 2D-STE method (box-and-whisker diagram). ^*The value is significantly different from the healthy cats (p < 0.05).

Figure 3

Results of circumferential strain by 2D-STE method (box-and-whisker diagram). ^*The value is significantly different from the healthy cats (p < 0.05).