Ultrasonic experimental research of systolic left ventricular transmural torsion in different electro-mechanical patterns: a canine model

Abstract

Objective To evaluate the mechanical characteristics of systolic left ventricular(LV) transmural torsion in different LV electro-mechanical patterns using speckle tracking imaging. Methods Five open-chest canine models were employed for the acquirement of the basal, apical short-axis and four-chamber views of LV during baseline(BASE) and right atrial appendage(RAA), right ventricular apical (RVA), left ventricular lateral wall (LVL) and left ventrieular apical (LVA) pacing. Subendocardial (subend),subepicardial(subepi) and bulk rotation angle(RA) and segmental angle excursion(AE) at basal and apical level were analyzed using a dedicated workstation. LV torsion at different layers and bulk and global LV ejection fraction (EF) were calculated. Results ① There were no significant difference of transmural torsion and RA at basal and apical level between BASE and RAA pacing (P>0.05);② LV torsion of subend, subepi and bulk during RVA pacing were lower than those during RAA pacing(P0.05);LV torsion of subend and bulk during LVA pacing were lower than those during RAA pacing(P0.05);LV RA of subend,subepi and bulk at basal level during RVA and LVA pacing were lower than those during RAA pacing (P 0.05); ④AE of segments near the pacing site decreased during different ventricle paeings (P<0.05); ⑤At BASE and during RAA pacing, LV bulk and subepi torsion were positively correlated to EF; RA of subend,subepi and bulk at basal level were positively correlated to EF. Conclusions LV transmual torsion are significantly depressed during RVA and LVA pacing. There is a spatial co-relationship between LV EF and torsion and rotation of bulk and subepi at basal level in normal LV electro-mechanical patterns. Key words: Echocardiography; Cardiac pacing, artificial; Ventricular function, left; Torsion