Alteration in Subendocardial and Subepicardial Myocardial Strain in Patients with Aortic Valve Stenosis: An Early Marker of Left Ventricular Dysfunction?

Background It has been suggested that myocardial systolic impairment may not be accurately detected by the evaluation of endocardial excursion alone. The aim of this study was to test the hypothesis that changes in left ventricular (LV) subendocardial and subepicardial strain are sensitive markers of severity of aortic stenosis (AS) and LV function in patients with AS. Methods Transthoracic echocardiography was performed in 73 consecutive patients with AS who had preserved systolic function and in 20 controls. Longitudinal strain, subendocardial radial strain, subepicardial radial strain, and transmural radial strain were measured using LV apical and short-axis images. Results The 73 patients enrolled in this study were classified according to AS severity: mild ( n = 10), moderate ( n = 15), or severe ( n = 48). Although transmural and subepicardial radial strain showed similar values in all groups, subendocardial radial strain and longitudinal strain could differentiate mild or moderate AS from severe AS. Only the ratio of subendocardial to subepicardial radial strain (the bilayer ratio) decreased significantly as the severity of AS increased. Bilayer ratio showed weak correlations with LV ejection fraction ( r = 0.37) and E/E′ ratio ( r = −0.33) and moderate correlations with LV mass ( r = −0.55) and aortic valve area ( r = 0.71). Moreover, bilayer ratio was independently associated with AS severity ( P = .001). In 21 patients who underwent aortic valve replacement, subendocardial radial strain and bilayer ratio increased 7 days after surgery, whereas other echocardiographic parameters of LV function showed no improvement. Conclusions Bilayer ratio can reliably differentiate patients with varying degrees of AS severity and is a sensitive marker of LV function. These findings suggest that the evaluation of subendocardial and subepicardial radial strain might be a novel method for assessing LV mechanics in patients with AS.