Dobutamine Stress Echocardiography:
In this study, Senning patients showed chronotropic incompetence, as the increase in heart rate at peak stress did not reach the expected target heart rate for age or the test had been aborted because of the development of symptoms (Dyspnea, or arrhythmia). Chronotropic incompetence may be the cause of dyspnea in such patients during dobutamine infusion. This was in agreement with Sterrett LE et al, who noticed that decreased exercise tolerance in patients after arterial switch surgery for D-transposition of the great arteries was due to chronotropic incompetence and was known to be associated with increased mortality in adults. (34)
In this study the tricuspid systemic atrioventricular regurge increased in severity with peak dobutamine stress, this may be because the decrease in RV EDV was non-significant that remained tricuspid valve annulus dilated with increased contractility on the other hand during peak dobutamine stress.
In this study, despite, the dysfunctional RV showed an increase in RV EF with peak dose stress dobutamine, but this increase was not that such a significant one. This may be due to the significant decrease in RV end-systolic volume than RV end-diastolic volume. So, wall stress increased less with dobutamine stress test in patients who underwent the Senning procedure. However, in this study other parameters used to assess the contractile reserve of the systemic RV; TAPSE, and RV GLS proved the existence of masked RV contractile reserve at peak dobutamine stress echocardiography in such age group of Senning patients, thus promoting the necessity for continuing anti-fibrotic and anti-failure measures in those patients in such age group. Monitoring exercise capacity, contractile reserve, and response to anti-fibrotic measures in atrial switch patients remain important diagnostic and predictive tests.