Different Dynamic Luminal Compression of Intramural Segment During Cardiac Cycle in Anomalous Aortic Origin of Coronary Arteries Revealed by Ivus Gated Sequences

Introduction: Anomalous Aortic Origin of Coronary Artery (AAOCA) with intramural (IM) segment is associated with risk of sudden cardiac death (SCD). The pathogenic mechanism is believed to be the IM compression caused by the aorta expansion during effort. However, the IM compression occurrence and magnitude during the cardiac cycle remain unknown. Hypothesis: We hypothesized that the IM segment is subjected to dynamic compression during different phases of cardiac cycle with a luminal area and roundness smaller in systole than in end-diastole. Methods: Lumen dynamics was derived from IVUS pullbacks of N=35 AAOCA (N=23 with IM tract) after retrospective image-based gating to identify cardiac cycles. The cyclic change of area (A) and roundness (R=minimum/maximum lumen axis) of ostial, distal IM, and extramural (EM) tracts were described after manual lumen segmentation. The systolic phase was identified, in each patient, by estimating normal PQ and QT intervals from image-based gating. Results are presented with median and interquartile range. One-tailed Wilcoxon signed-rank test (p<0.025) assessed differences between systolic and diastolic phases in each tract. Results: A systolic reduction of roundness was observed in ostium [R systole = 0.5 (0.2), R diastole = 0.6 (0.3), flattening: -7% (10), p=0.01] and distal IM segment [R systole = 0.7 (0.2), R diastole = 0.8 (0.2), flattening: -6% (16), p=0.004]. No-IM segments showed normal behaviour and remained circular during the entire cardiac cycle. The distal IM had an area reduction during systole [A systole = 8.3 (2.3) mm 2 , A diastole = 8.1 (2.9) mm 2 , narrowing: -4% (11), p=0.009] that was not observed in all other segments (Figure 1). Conclusion: AAOCA with IM segment has pathological dynamic compression mainly in systole. Studying AAOCA behaviour with IVUS during the cardiac cycle may help to evaluate and quantify the severity of the narrowing.