Assessment of Right Ventricular Strain in Children with Repaired Tetralogy of Fallot Using Speckle Tracking Imaging
Tetralogy of Fallot (TOF) is a congenital heart defect that was first surgically repaired in 1955. The initial surgical approach involved the use of a trans-annular right ventricular outflow tract patch to relieve obstruction. However, this procedure often resulted in long-standing pulmonary valve regurgitation and increased right ventricular (RV) volume, leading to complications such as arrhythmias and sudden death. Over time, the surgical strategy evolved to preserve the pulmonary annulus, which, while reducing regurgitation, introduced a mix of pulmonary stenosis and regurgitation. Today, clinicians are concerned with the long-term decline in RV function in patients with repaired TOF (rTOF) and rely on cardiac magnetic resonance imaging (CMR) to assess RV volumes and function. However, CMR is not routinely used for monitoring RV dysfunction in rTOF patients due to its complexity and cost. Echocardiography, particularly speckle tracking imaging (STI), has emerged as a valuable tool for estimating RV function and assisting in determining the appropriate timing for CMR.
The right ventricle plays a critical role in cardiovascular function, and its dysfunction is a significant clinical indicator in rTOF patients. Early detection of RV dysfunction is essential for timely intervention. However, echocardiographic evaluation of RV function in rTOF patients is challenging due to the complex shape of the ventricle. STI provides an alternative method for quantifying ventricular function by measuring strain and strain rate (SR). While STI is commonly used to assess left ventricular function, its application in evaluating RV function, particularly in pathological conditions like rTOF, remains less established.
This study aimed to evaluate changes in RV deformation parameters during the early phase in pediatric patients after TOF surgery and to investigate the value of STI in assessing RV function. The study included 75 consecutive rTOF patients who underwent surgery between 2008 and 2016. Inclusion criteria required that patients had no changes in medical therapy or surgical intervention, while exclusion criteria included a post-surgical duration of less than one year, arrhythmia, and poor-quality echocardiography results. Baseline data and surgical information were reviewed for 57 patients, and their echocardiographic data were compared with those of 24 healthy controls. The study was approved by the local research ethics committee, and informed consent was obtained from the parents of all participants.
Echocardiographic imaging was performed using iE33 or EPIQ 7C ultrasound systems equipped with transthoracic broadband transducers. Two-dimensional (2D) greyscale harmonic images were obtained with patients in the supine position, and RV chamber measurements were performed according to the guidelines of the American Society of Echocardiography. Functional parameters, including fractional area change (FAC) and tricuspid annular plane systolic excursion (TAPSE), were assessed. FAC was calculated as the difference between end-diastolic and end-systolic areas divided by the end-diastolic area. TAPSE was measured as the maximal excursion of the lateral annulus in the apical four-chamber view. All diameter parameters were corrected for body surface area (BSA).
Three-dimensional (3D) echocardiography was performed from the apical acoustic window using X5-1 and X7-2 transducers. RV datasets were acquired separately to include the entire ventricular chamber, and offline analysis was performed using 3D RV analysis software. The right ventricular three-dimensional ejection fraction (3D-EF) was calculated as the difference between end-diastolic and end-systolic volumes divided by the end-diastolic volume. Patients were divided into two groups based on the RV 3D-EF cutoff value: Group I (3D-EF ≥45%) and Group II (3D-EF <45%).
Speckle tracking imaging was used to assess myocardial deformation, with strain defined as the percentage change in myocardial deformation and SR as the deformation rate of the myocardium over time. Longitudinal and transverse strain and SR were measured for both the RV free wall and septum. Global longitudinal strain (GLS) was also calculated.
The study population included 39 male (68%) and 18 female (32%) patients, with a median age at surgery of 0.61 years and a mean postoperative duration of 3.8 years. The patients were divided into Group I (37 patients) and Group II (20 patients) based on RV 3D-EF. The control group consisted of 24 healthy children. Baseline characteristics showed that RV diameters were larger in the rTOF groups compared to the control group, but there was no significant difference between the two rTOF groups. All RV function parameters were lower in the rTOF groups than in the control group, except for TAPSE. Group II had more severe pulmonary stenosis, but the width of regurgitation did not differ significantly between the two rTOF groups. GLS was lower in Group II than in Group I, and both groups had lower GLS than the control group.
Multiple linear regression analysis was performed to develop a predictive model for 3D-EF using echocardiographic parameters. The best-performing model incorporated both FAC and GLS, with the equation: Y = 15.624 + 0.541 × FAC – 0.585 × GLS. The standardized coefficients for FAC and GLS were 0.557 and -0.380, respectively.
Segmental myocardial deformation parameters were compared between the two rTOF groups and the control group. Longitudinal strain and SR of the free wall and septum were lower in Group II than in the control group, and further lower than in Group I. Transverse strain and SR of the RV free wall and septum were higher in Group I compared to the control group, but there was no significant difference in Group II. The septum transverse strain and SR were lower in Group II compared to Group I.
Intra-observer and inter-observer agreement analyses were performed for 3D-EF and GLS measurements. The coefficients of variation for intra-observer measurements were 8.0% for 3D-EF and 10.9% for GLS, while the coefficients of variation for inter-observer measurements were 8.7% for 3D-EF and 14.3% for GLS.
In conclusion, this study demonstrated that RV function, including 3D-EF and GLS, was slightly decreased in rTOF patients during the early postoperative phase. The transverse strain and SR were significantly increased in patients with normal EF, suggesting a potential preservation of RV myocardial function. STI proved to be an effective diagnostic technique for detecting RV function in rTOF patients, with segmental parameters such as transverse strain and SR providing valuable insights into pre-clinical changes in RV function. Further studies are needed to explore the long-term implications of these findings and to establish the role of STI in the routine clinical monitoring of rTOF patients.
doi.org/10.1097/CM9.0000000000000126
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