Potential mechanism of left ventricular spherical remodeling: association of mitral valve complex-myocardium longitudinal tissue remodeling mismatch

Abstract

Since mitral valve (MV) complex (MVC) longitudinally bridges left ventricular (LV) base-end and its middle, insufficient MVC longitudinal tissue length (TL) elongation relative to whole LV myocardial longitudinal TL elongation could limit LV-base-longitudinal-TL elongation, leading to predominant LV-base-transverse-TL elongation, constituting LV spherical remodeling. In 30 patients with dilated cardiomyopathy (DCM), 30 with aortic regurgitation (AR), and 30 controls, LV sphericity, LV-apex- or base- transverse- and longitudinal-TL, MVC-longitudinal-TL and whole-LV-longitudinal-TL were measured by 3D echocardiography. Ratio of each measure vs. mean normal value (i.e., LV-apex-transverse-TL ratio) was considered to express the directional and regional tissue elongation. [LV-base-longitudinal-TL ratio/global-LV-TL ratio] and [MVC-longitudinal-TL ratio/whole-LV-longitudinal-TL ratio] were obtained as the degree of LV-base-longitudinal-TL or MVC-longitudinal-TL elongation relative to the whole LV elongation. LV-apex-transverse-, LV-apex-longitudinal- and LV-base-transverse-TL ratios were significantly increased (1.27 to 1.42, p<0.01) in both DCM and AR, while the LV-base-longitudinal-TL ratio was not increased in DCM (1.04±0.19, n.s.) and only modestly increased in AR (1.12±0.21, p<0.01). Whole-LV-longitudinal-TL ratio was significantly increased in both DCM and AR (1.22±0.18 and 1.20±0.16, p<0.01), while MVC-longitudinal-TL ratio was not or only modestly increased in both groups (1.07±0.15, n.s. and 1.12±0.17, p=0.02, respectively). Multivariable analysis revealed that LV sphericity was independently related to a reduced [LV-base-longitudinal-TL ratio/global-LV-TL ratio] (standard β=-0.42, p<0.01), which was further related to a reduced [MVC-longitudinal-TL ratio/whole-LV-longitudinal-TL ratio] (standard β=0.72, p<0.01). These are consistent with the hypothesis that relatively less MVC-longitudinal-TL elongation in the process of primary LV myocardial tissue elongation may limit LV-base-longitudinal-TL elongation, contributing to LV spherical remodeling.

Echocardiographic Advances in Dilated Cardiomyopathy

“…Hence, MVC may potentially deforms regionally and not uniformly leading to limited elongation of LV base and asymmetrically less elongation of the MVC. LV sphericity can be calculated via 2D echocardiography by the ratio of transverse cavity dimension to the longitudinal diameter at end diastole, so a higher sphericity index represents greater LV sphericity: therefore, remodeling is predominant at bases and not as clear at the apex leading to new promising diagnostic tools and interventions [ 57 ]. Artificial intelligence and machine learning (ML).…”