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Research code: 1251815
Ethics code: 99310319193
Clinical trials code: 99-3-103-19193

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Isa Tafreshi R, Radgoodarzi M, Hassani M, Navabi Shirazi M A. Evaluation of right ventricular function in children with repaired tetralogy of Fallot who may undergo pulmonary valve replacement by echocardiography; a comparison with MRI findings. RJMS 2024; 31
URL: http://rjms.iums.ac.ir/article-1-8448-en.html
, isatafreshi.r@iums.ac.ir
Abstract:   (321 Views)
Tetralogy of Fallot (TF) represents the most prevalent form of cyanotic congenital heart disease, characterized by chronic pulmonary regurgitation, the foremost postoperative complication leading to right ventricular (RV) dilation, progressive RV dysfunction, and life-threatening arrhythmia(2). Multiple criteria have been established to determine the optimal timing for surgical intervention in asymptomatic patients for this progressive condition. Nevertheless, achieving consensus on the optimal timing of pulmonary valve replacement (PVR) remains elusive(2, 11). An essential criterion for this decision is the assessment of RV systolic function, which proves challenging due to the complex RV geometry and the absence of standardized methods for RV volume assessment. Consequently, the limitations of echocardiography have prompted the use of cardiac MRI (CMR) as an essential tool for RV size and function assessment(6, 10). However, the limited availability and accessibility of CMR compared to echocardiography highlight the need for reliable and reproducible echocardiographic methods to determine the appropriate timing for CMR assessment(8, 9, 50).
The objective of our study was to identify optimal echocardiographic parameters for RV function and size that would indicate the necessity for further CMR evaluation. Additionally, we aimed to investigate potential correlations between echocardiographic measures of RV systolic function and CMR-derived parameters.
Methods. This is a prospective study of patients with repaired TF who revealed severe pulmonary regurgitation or severe RV dilation and who underwent cardiac MRI between 2015 and 2022. A trained physician, blinded to CMR data, conducted the transthoracic echocardiographic study within six months before the CMR evaluation. Inclusion criteria were: (1) age below 18 years, (2) significant RV dilation, (3) absence of significant residual cardiac lesions or arrhythmias, (4) left ventricular ejection fraction (LVEF) greater than 50%, (5) no limitations in daily physical activities (NYHA functional class I), and (6) absence of concomitant diseases.
All patients exhibited regular sinus rhythm with complete right bundle branch block. The study protocol followed the guidelines of the Declaration of Helsinki for humans and was approved by our institutional review board.
Echocardiographic data were obtained and analyzed according to the guidelines of the American Society of Echocardiography(14, 15, 26). To measure ventricle size in the four-chamber view, the largest transverse diameter of the right ventricle in the basal third was recorded and expressed in millimeters, then compared with the data obtained in MRI.
Quantitative RV function was assessed by calculating fractional area change (FAC) and right ventricular outflow tract fractional shortening (RVOT-FS) using 2D echocardiography. FAC, considered one of the best-validated quantitative methods for measuring RV function, with a value of less than 35%, is considered indicative of ventricular dysfunction(16, 20). Tricuspid annular plane systolic excursion (TAPSE) of the lateral tricuspid annulus, a reproducible marker of RV systolic function, was measured using 2D-guided M-mode from the apical 4-chamber view. Previous reports have shown that TAPSE less than 16 mm is correlated with RV systolic dysfunction(21). The longitudinal performance of the RV was evaluated using Tissue Doppler Imaging (TDI) by measuring parameters at the lateral corner of the tricuspid valve annulus. The peak longitudinal systolic velocity of the RV free wall (s') was obtained as an index of regional RV systolic function, with values less than 9.5 cm/s considered indicative of right ventricular dysfunction(26). Additionally, myocardial acceleration during isovolumic contraction (IVA) as a measure of ventricular contractility was calculated from the basal level of the RV-free wall. Also, the TDI-derived myocardial performance index (TDI-MPI) was determined from the lateral ring of the tricuspid valve(22).
Results. The study included 37 patients with an average age of 10.8 ± 2.2 (range:7-17) years who underwent TF repair at an average age of 13.8 ± 5.5 months. All patients received a trans annular patch enlargement of the right ventricular outflow tract, with a median follow-up post-operation of 9.5 ± 2.1 years. All patients exhibited LVEF within the normal range, and none had RVEF less than 40% by CMR. We observed a significant correlation between echocardiographic-derived RV end-diastolic diameter and RV end-diastolic volume obtained by CMR (r=0.61, p< 0.05). RV-FAC<35% was not seen in any of the patients and the values of RV-FAC were correlated with CMR-derived RVEF (P<0.01, r =0.58). Furthermore, RVOT-FS, as one of the new measures of RV systolic function, showed a direct statistical relationship with CMR-RVEF (P< 0.02, r=0.57)(20). Although TAPSE values were lower than those reported in the normal population, there was no statistical correlation with CMR-RVEF or right ventricular volumes(9, 37). MPI was calculated as an important measure of global RV function with an average value of 0.48±0.08, but no significant correlation was found with CMR-RVEF. IVA values, as another measure of longitudinal function of the right ventricle, were found within the normal range, but the statistical relationship between this measure and CMR-RVEF was not seen(29, 47). The average s´ wave velocity was 7.2± 1.4 cm/s, lower than the normal population in previous reports, but had no statistical relationship with CMR-RVEF(26). On the other hand, our findings revealed a significant correlation between s´ velocity, and IVA values with ventricular diastolic volume, which is consistent with previous studies(30, 39).
Conclusion. Measuring both RVOT-FS and RV-FAC indices by echocardiography is crucial in predicting CMR-RVEF, serving as one of the most important standard criteria in deciding the appropriate timing for PVR. Simultaneously, monitoring the increase of right ventricular diameter with echocardiography offers an easy and accurate method to estimate the severity of ventricular dilatation. IVA and s' wave, as indicators of regional right ventricular myocardial function, along with MPI as an index of global ventricular function, correlated with the degree of ventricular dilatation caused by increased volume load and will play a role in the follow-up process of patients with repaired TF. Therefore, measuring this set of echocardiographic indices is important in estimating both CMR-derived RVEF and RV diastolic volume, significantly contributing to reducing the frequency of MRI in the follow-up of patients with repaired TF.

Type of Study: Research | Subject: Pediatric Cardiology

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