Quantification of right ventricular electromechanical dyssynchrony by two-dimensional multi-plane echocardiography in adults with repaired Tetralogy of Fallot
Authors: Bowen DJ , Kauling RM , Pelosi C , Mcghie JS , Cuypers JAAE , Roos-Hesselink JW , Van Den Bosch AE 
Published: February 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Electromechanical dyssynchrony between right ventricular (RV) free wall and septum contraction in repaired Tetralogy of Fallot (ToF) contributes to inefficient RV mechanics and ultimately reduced systolic function (1). Whilst current assessment of RV synchronicity involves the lateral wall and septum, the use of two-dimensional multi-plane echocardiography (2D-MPE) enables additional RV walls to be evaluated, reflecting global myocardial dynamics (2).

Purpose
The aim of this study is to gain new insights into regional RV wall mechanics using 2D-MPE, determining the potential added value of this imaging model in the assessment of electromechanical synchronicity.
Methods
Twenty ToF patients and fifteen healthy controls underwent detailed RV assessment using 2D-MPE. Furthermore, all ToF patients underwent on the same day cardiac magnetic resonance imaging (cMRI). RV wall longitudinal strain (LS) and synchronicity of contraction were measured using speckle tracking in three different RV walls (lateral, anterior and inferior) and the RV septum. RV synchronicity was assessed by the time to peak (TTP) deformation delay between the basal RV wall and mid septal segment. Additionally, mechanical dispersion was calculated as the standard deviation of average TTP strain values across four (SD-4: basal-mid septal and lateral), six (SD-6: inclusive inferior wall) and eight segments (SD-8: inclusive anterior and inferior walls).

Results
RV wall average LS was significantly lower in ToF patients compared to the control group (-20.8 ± 4.0% vs -28.1 ± 3.6%, p = &lt;0.001). In ToF patients, higher LS values were seen in the lateral (-21.5 ± 4.7%) and inferior (-20.7 ± 3.7%) walls compared to the anterior (-19.0 ± 4.5%) wall. RV wall to septum TTP delay was significantly increased for all segments in ToF patients compared to healthy controls (all p &lt;0.03). In ToF patients, inferior wall-septum TTP delay was 50 [5, 89]ms whilst the lateral (65 [26, 81]ms) and anterior wall (66 [40, 98]ms) delay was longer. In healthy controls meanwhile, peak RV wall and septal deformation occurred almost simultaneously (table 1). SD-4 was significantly greater in ToF patients compared to controls (39 [23, 56]ms vs 14 [0, 21]ms, p = 0.001) however SD-6 and SD-8 were not significantly different (36 [22, 53]ms vs 22 [17, 35], p = 0.09; 31 [17, 51]ms vs 30 [20, 32]ms, p = 0.33). The association between mechanical dispersion measurements and cMRI-derived right ventricular ejection fraction (RVEF) strengthened with the inclusion of additional RV walls (SD-4 R² = -0.18; SD-6 R² = -0.18; SD-8 R² = -0.27).

Conclusion
2D MPE provides new insights into RV regional deformation and evaluates the association between the mechanics of individual RV walls and the septum. Further research is required to expand upon this novel approach for the assessment of regional RV function. Abstract Table 1 Abstract Figure 1