Characterization of the Cardiac Reinnervation of Patients With Transposition of the Great Arteries Long After Repair With the Arterial Switch Operation. Correlation With Electrocardiographic and Exercise Test Parameters

To describe the myocardial reinnervation pattern of a cohort of patients with TGA long after ASO using cardiac nuclear imaging.

To identify myocardial perfusion defects using cardiac nuclear imaging.

To identify myocardial innervations/perfusion mismatch using cardiac nuclear imaging.

To determine exercise capacity (METs and double product) and chronotropic response (Maximal heart rate and heart rate increase pattern). Correlate with myocardial reinnervation pattern and sinus node reinnervation.

To determine exercise induced ischeamic ST segment changes. Correlate with myocardial perfusion defects and innervation-perfusion mismatch.

To determine sinus node innervation through heart rate variability (HRV) which will be assessed by time domain variables (the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD)) and frequency domain variables (variance of all R-R intervals - total power (TP); power in the very low frequency range - very low frequency (VLF, 0.003-0.04 Hz); power in the low frequency range-low frequency (LF, 0.04-0.15Hz); low frequency power in normalized units-normalized low frequency; power in the high frequency range-high frequency (HF, 0.15-0.40 Hz); and high frequency power in normalized units-normalized high frequency and the ratio of low frequency to high frequency (LF/HF)).