Increased valvulo-arterial impedance differently impacts left ventricular longitudinal, circumferential, and radial function in patients with aortic stenosis: A speckle tracking echocardiography study

Abstract

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 (ZV_a ) 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 ZV_a 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 cm² or <0.6 cm² /m² ) underwent standard echocardiography to characterize aortic valve gradients, LV function, and ZV_a . 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 ZV_a quartiles: Q1 (ZV_a ≤3.43 mm Hg/mL/m² ), Q2 (3.43<ZV_a ≤4.1 mm Hg/mL/m² ), Q3 (4.1<ZV_a ≤5.1 mm Hg/mL/m² ), ad Q4 (ZV_a >5.1 mm Hg/mL/m² ). ZV_a increase from Q1 to Q4 was associated with a progressive reduction in GLS and GCS (ANOVA, both P<.0001). GRS was relatively insensitive to ZV_a 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.

Keywords: aortic stenosis; left ventricular function; speckle tracking echocardiography.