Aortic arch shape is not associated with hypertensive response to exercise in patients with repaired congenital heart diseases

Abstract

Background: Aortic arch geometry is linked to abnormal blood pressure (BP) response to maximum exercise. This study aims to quantitatively assess whether aortic arch geometry plays a role in blood pressure (BP) response to exercise.

Methods: 60 age- and BSA-matched subjects--20 post-aortic coarctation (CoA) repair, 20 transposition of great arteries post arterial switch operation (ASO) and 20 healthy controls--had a three-dimensional (3D), whole heart magnetic resonance angiography (MRA) at 1.5 Tesla, 3D geometric reconstructions created from the MRA. All subjects underwent cardiopulmonary exercise test on the same day as MRA using an ergometer cycle with manual BP measurements. Geometric analysis and their correlation with BP at peak exercise were assessed.

Results: Arch curvature was similarly acute in both the post-CoA and ASO cases [0.05 ± 0.01 vs. 0.05 ± 0.01 (1/mm/m²); p = 1.0] and significantly different to that of normal healthy controls [0.05 ± 0.01 vs. 0.03 ± 0.01 (1/mm/m²), p < 0.001]. Indexed transverse arch cross sectional area were significantly abnormal in the post-CoA cases compared to the ASO cases (117.8 ± 47.7 vs. 221.3 ± 44.6; p < 0.001) and controls (117.8 ± 47.7 vs. 157.5 ± 27.2 mm²; p = 0.003). BP response to peak exercise did not correlate with arch curvature (r = 0.203, p = 0.120), but showed inverse correlation with indexed minimum cross sectional area of transverse arch and isthmus (r = -0.364, p = 0.004), and ratios of minimum arch area/ descending diameter (r = -0.491, p < 0.001).

Conclusion: Transverse arch and isthmus hypoplasia, rather than acute arch angulation plays a role in the pathophysiology of BP response to peak exercise following CoA repair.

Figure 1

Patient-specific 3D geometric reconstructions of aortas. Normal (healthy subject), ASO (arterial switch operated subject), CoA (coarctation of the aorta subject) displaying geometric landmarks of centreline from the centre point of the aortic valve to the descending aorta at the level of the diaphragm, circle tangent to the highest point of the vessel centreline with the radius (r) for assessment of arch curvature, and positions of measurements for cross sectional areasA1 (transverse arch), A2 (isthmus) and A3 (descending aorta) as labelled.

Figure 2

Five examples for each group of 3D anatomical reconstructions. 5 cases healthy controls (top panel) with smooth arch curvature, 5 ASO cases(middle panel) with acute arch angulation and 5 cases of CoA post repair (bottom panel), with acute angulation and some hypoplastic transverse arch and isthmus).

Figure 3

Scatter plots displaying correlations of systolic BP at peak exercise with various geometric measures. (A) BSA indexed aortic arch curvature, (B) indexed minimum aortic arch area at the level of transverse segment or isthmus, and (C) Ratio of the minimum area at the level of transverse arch or isthmus to descending aortic ratio respectively. Letter (r) denotes correlation coefficient with an accompanying sign of dispersion –p values are reported for statistical significance at p = 0.05.