Abstract 2256: Myocardial Blood Flow and Viability in Children With Transpositon of the Great Arteries After Arterial Switch Operation Assessed With Magnetic Resonance Imaging
Introduction: Coronary complications represent an important risk factor for sudden cardiac death and infarction late after arterial switch operation (ASO) in children with transposition of the great arteries (TGA). Therefore, we sought to investigate regional myocardial blood flow distribution and viability in TGA pts using cardiac magnetic resonance (CMR).
Methods: In 32 TGA patients post ASO (age: 12,4 ±5,3 yrs) CMR first-pass perfusion imaging (0.03 mmol/kg Gd-DTPA; TR/TE/α=2.6/1.1/20°) and late gadolinium enhancement (LDE) imaging for viability assessment using an ECG triggered 3D inversion recovery sequence (TR/TE/α= 3.7/1.8/15°) was applied using a 3 Tesla MR-scanner (Philips, Achieva). These findings were compared to regional wall motion measurements from short axis cine imaging. Seventeen age and gender- matched heart healthy children who underwent MRI for neurological indications served as controls. Seven TGA pts were suspicious of or known to have coronary artery stenosis or occlusion. Quantitative myocardial blood flow at rest and stress (Adenosin 140 mcg/kg/min) was calculated in 6 LV segments per slice (2–3 slices/pt) using a model independent deconvolution. CMR results were compared to conventional x-ray guided coronary angiography in all pts.
Results: In 6 patients myocardial stress blood flow was significantly reduced at stress due to an occlusion of the left coronary artery (LCA) in 4, and a hypoplastic left anterior descending artery in 2. Scar tissue (i.e. LGE) was detected in the antero-septal region of 2 pts with an occluded LCA. One of those patients (14 yr female) received minimal invasive coronary artery bypass surgery and one pt (22 yr male) a conventional mammary artery bypass. Myocardial perfusion reserve (MPR=hyperemic: resting flow) in pts with morphological normal coronary arteries (n=25) was significantly reduced as compared to heart healthy children (2,6 ±0,7 vs 3,4 ±0,9; p<0.05).
Conclusions: In children post arterial switch operation myocardial ischemia and scar tissue can be detected with CMR to guide further therapy. The global impairment of coronary flow reserve in these pts, compared to healthy hearts may indicate altered vasoreactivity due to coronary reimplantation.