Impact of transverse aortic arch hypoplasia after surgical repair of aortic coarctation: an exercise echo and magnetic resonance imaging study.

Background: We sought to assess the impact of persistent hypoplasia of the transverse aortic arch (TAA) after repair of aortic coarctation (AoC), on blood pressure response to exercise, left ventricular (LV) hypertrophy and presence of collateral circulation.
Methods: 34 consecutive patients with end-to-end repair of AoC (age at repair 3.2+/-2.5 years) underwent exercise echocardiography and magnetic resonance imaging (MRI) at 24+/-7 years of age (range 11.3 to 44.6 years). Systolic Doppler pressure gradient (SPG) across the descending aorta and blood pressure at the right arm were measured at baseline and every minute throughout all exercise. Magnetic resonance imaging was used to measure LV mass index, presence and amount of collateral flow, and the diameters of the aortic isthmus and TAA indexed to the diameter of the diaphragmatic.
Results: Aortic isthmus index was higher than that of the TAA (p=0.006). We observed LV hypertrophy in 15 patients (45%) and presence of collateral circulation in 14 (41%). Eighteen patients (53%) had an abnormal blood pressure response to exercise. Patients with abnormal pressure response to exercise had smaller TAA index (p=0.0005), but similar aortic isthmus index (p=0.09). They also had higher exercise SPG (p<0.0001), higher LV mass index (p<0.0001) and prevalence of LV hypertrophy (p=0.007), higher prevalence of collateral circulation (p<0.0001) and a higher amount of collateral flow (p<0.0001). TAA index, but not aortic isthmus index, correlated with exercise blood pressure (r=-0.59, p=0.003), exercise SPG (r=-0.70, p=0.0005), amount of collateral flow (r=-0.74, p=0.0002) and LV mass index (r=-0.68, p=0.0007).
Conclusions: After repair of AoC, hypoplasia of the TAA may be responsible for abnormal blood pressure response to exercise, persistence of collateral circulation and LV hypertrophy.