P868Global strain rate is a load dependent parameter of heart deformation - the transcatheter atrial septal defect closure model


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Abstract

Purpose: Two-dimensional strain analysis allows accurate measurement of cardiac deformation indices such as tissue velocity (TV), strain, and strain rate. In recent years, there has been an effort to find an accurate parameter for the measurement of myocardial contractility, independent of loading condition. TV has been shown to be load dependent, as has strain in most articles. Strain rate has been claimed as a preload-independent valuable parameter to evaluate heart contractility.We aim to investigate whether strain rate is indeed load independent in the model of sharp and sudden change in preload condition before and after atrial septal defect (ASD) closure.Methods: Echocardiographic data was retrospectively processed to measure TV, global strain (GS), and global strain rate (GSR) in the free wall of the right ventricle immediately before and after successful percutaneous closure of an ASD in 11 children aged 2-13 years (average 7.1). The average shunt through the ASD was 1.7:1 (1.2- 2.4:1). We measured TV, GS, and GSR from the apical 4-chamber view using two-dimensional strain analysis software (Echopac, General Electric Medical Systems, Milwaukee, WI). The mean values for TV, GS, and GSR before and after ASD closure were compared using the paired t-test. p<0.05 was considered significant. This study was approved by our institutional review board.Results: The average peak systolic TV decreased from 11.5±1 (m/s) before to 8.5±1 (m/s) after closure (p<0.00001). The average right ventricle free wall GS decreased from 30.8 ± 4% to 26.5±4.5 % (p=0.05). The average GSR decreased from 2.1±0.3 (1/sec) before ASD closure to 1.6±0.4 (1/sec) after closure (p<0.00002) (Fig.). Qp/Qs correlated well with the percent change of TV before and after ASD closure (Qp/Qs = .6 + .04 TV percent change; r =.72, SEE=.3).Conclusions: GSR seems to be preload dependent in the model of acute change in loading conditions associated with ASD closure. Qp/Qs correlated with increased right ventricular peak systolic velocity.

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