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)