Resting echocardiography:
In patients with D-TGA who underwent atrial switch repair, there are several potential mechanisms for TV regurgitation including, congenital abnormalities of the TV, dysfunction of the systemic RV, right-to-left septal shift, increased retrograde trans-tricuspid pressure gradient, and iatrogenic causes. (21) In this study, TV regurgitation was related to RV enlargement and dysfunction rather than related to anomalies of the TV. It is still not clear whether systemic RV dysfunction or TV regurgitation occurs first. (22)
Patients with systemic RV post atrial switch surgery also have preload abnormalities, and such factors should be taken into account. After a Senning operation, patients may develop hemodynamic abnormalities related to pulmonary and systemic baffles. (23) After the atrial switch, echocardiography is recommended for the evaluation of the systemic right ventricle and integrity of the baffle. (24) In our study, we observed no baffle narrowing with only small baffle leaks in 2 patients denoting preload impairment on the systemic ventricle in these two patients.
The improvement in survival of patients after D-TGA surgical correction (particularly in patients with atrial switch and systemic RV) result in the development of late complications, commonly in adulthood, such as heart failure, atrial arrhythmias, and sudden cardiac death, the incidence of which increases over time. Watchful follow-up is necessary and serial imaging is required to analyze changes in systolic function over time. After atrial switch repair, right ventricular dysfunction was recorded in 48% of patients with D-TGA, symptomatic heart failure was reported in 25% at 15 to 18 years of follow-up, and more than 50% had moderate to severe systemic right ventricular dysfunction after 25 years. (5,25,26)
In this study systemic RV function was significantly depressed in the atrial switch Senning children than in the controls as measured by echocardiographic parameters; RV EF by Simpson’s one-plane method, TAPSE, and speckled RV GLS. This was in agreement with some investigators (27,28) who have proposed that myocardial fibrosis results from prolonged hypoxemia during infancy while patients await the atrial switch repair. Others (29) have believed that it may be caused by insufficient RV blood supply from the right coronary artery in the presence of hypertrophic systemic RV myocardium. These conditions are similar to the morphologic and hemodynamic changes of the RV in pulmonary artery hypertension patients in which afterload is also augmented. (30) Others denoted the presence of the atrial baffles (even those that are well functioning) may decrease RV inflow and consequently RV function. (23)
In patients with structurally normal hearts, the traditional approach to the assessment of systemic ventricular function is to measure ejection fraction. However, attempting to extend this to the atrial switch situation has proved challenging. The geometry of the RV makes it difficult to measure ejection fraction by echocardiography, which has prompted simple visual estimation. In contrast, with the introduction of 2D speckle tracking echocardiography, simple measurement of long-axis GLS is a rapid and definite measurement that has proven utility in a thorough assessment of subtle dysfunction at the early stage, but it has not been definitively estimated in patients with TGA. The technique is equally straightforward for the RV and is especially valid because the main bulk of right ventricular myocardial fibers are arranged longitudinally. With this technology, dysfunction can also be assessed online with very short processing times.
A correlation between Cardiac MRI-derived right ventricular function and right ventricular GLS has been described previously by Lipczynska et al. (31) In their prospective study of 40 patients with D-TGA after the atrial switch procedure (mean age 26 ± 5 years), they found a significant linear correlation between the systemic RV EF by cardiac MRI and RV GLS by echocardiography. In the mentioned study, systemic right ventricular GLS was proposed to be able to discriminate between systemic RV EF below or above 45% derived from cardiac MRI. However cardiac MRI has some limitations for its application in clinical practice including restricted availability, high cost, and contraindications, particularly for serial long-term follow-up of these patients. (32)
The Speckled RV GLS data in our current study confirm reduced systolic contractile function in the systemic RV of Senning children as compared to similar age controls. It has been suggested that systemic right ventricular GLS in patients with systemic right ventricular dysfunction has been found to have a high predictive value, high reproducibility, and can predict adverse clinical outcomes as morbidity and mortality. (33) A reduced septal longitudinal strain may contribute to reduced septal work and failure of the systemic right ventricle in TGA patients. (33)