Increased valvulo-arterial impedance differently impacts left ventricular longitudinal, circumferential, and radial function in patients with aortic stenosis: A speckle tracking echocardiography study
Résumé
BACKGROUND: In aortic stenosis (AS), the left ventricle (LV) should face an increased afterload that is due to both the stenotic aortic valve and the peripheral vascular resistance (PVR). Valvulo-arterial impedance (ZVa ) is a recently introduced parameter, which permits the evaluation of global LV afterload in AS. Aim of this study was to assess the influence of increasing ZVa on the longitudinal, circumferential, and radial components of LV mechanics. METHODS: A total of 126 patients (mean age: 80.1±12.0 years, males: 47%) with severe AS (aortic surface <1 cm(2) or <0.6 cm(2) /m(2) ) underwent standard echocardiography to characterize aortic valve gradients, LV function, and ZVa . 2D speckle tracking echocardiography was used to estimate global longitudinal (GLS), circumferential (GCS), and radial (GRS) LV strain. RESULTS: The population was divided into four groups according to ZVa quartiles: Q1 (ZVa ≤3.43 mm Hg/mL/m(2) ), Q2 (3.435.1 mm Hg/mL/m(2) ). ZVa increase from Q1 to Q4 was associated with a progressive reduction in GLS and GCS (ANOVA, both P<.0001). GRS was relatively insensitive to ZVa increase, a significant reduction of GRS appearing only in Q4 patients with respect to Q1 (29.7±16.4 vs 20.7±13.2%, P=.01). CONCLUSIONS: Left ventricle myocardial fibers show a different response to afterload increase. Subendocardial fibers function is impaired earlier, whereas mid-wall circumferential fibers remain substantially unaffected, providing interesting insights into the mechanisms of LV dysfunction in AS.