TRANSVERSE ARCH HYPOPLASIA PREDISPOSES TO ANEURYSM FORMATION AT THE REPAIR SITE AFTER PATCH ANGIOPLASTY FOR COARCTATION OF THE AORTA

Objectives. This study used magnetic resonance imaging (MRI) to evaluate the morphology and pathophysiology of aneurysm formation after patch angioplasty for coarctation of the aorta. Background. Late aneurysm formation at the repair site is a well known and frequent complication after patch angioplasty. However, because the underlying mechanisms remain unresolved, postoperative outcome is unpredictable and adequate follow-up difficult. Methods. Seventy-three of 85 patients with patch angioplasty for coarctation of the aorta were screened for aneurysm formation. Magnetic resonance imaging was performed in all 33 patients with an aneurysm, and results were compared with those for 13 control patients and 10 normal subjects. Mean (+/-SD) time between operation and MRI was 12.0 +/- 2.0 years. Aneurysm was defined as the ratio of the diameter of the aorta at the repair site to the diaphragmatic aorta greater than or equal to 1.5. Hypoplasia of the transverse arch and recoarctation at the repair site were defined as a ratio <0.9. Transverse arch ratios on MRI were compared with those on preoperative cineangiography and the pressure gradient between the patient's right and left arm. Results. All 33 patients with an aneurysm had a hypoplastic transverse arch. The 13 patients with a normal ratio at the repair site had a normal transverse arch ratio (chi square, p < 0.0001). Logarithmic regression showed a significant negative correlation (r = 0.62) between the repair site and transverse arch ratios. A significant pressure difference between the patient's right and left arm was found in patients with versus those without aneurysm (p = 0.0009). No significant difference was found between transverse arch ratios on preoperative cineangiography and postoperative MRI (mean 0.014 +/- 0.1, p = 0.4). Conclusions. Aneurysm formation at the repair site is highly related to hypoplasia of the transverse arch. Sufficient catch-up growth of a hypoplastic transverse arch is rare after late patch angioplasty. Dynamic phenomena, such as flow acceleration and turbulence, originating in a narrow transverse arch, may contribute to aneurysm formation at the repair site after patch angio plasty.