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.