CT Angiography for Late Complications of Coarctation Surgery
Abstract & Commentary
Synopsis: Helical CT angiography can usually replace catheter angiography for the evaluation of late complications of surgery for aortic coarctation.
Source: Schaffler GJ, et al. Helical CT angiography with maximum intensity projection in the assessment of aortic coarctation after surgery.
AJR Am J Roentgenol 2000;175:1041-1045.
Late postoperative complications of coarctation of the aorta include re-stenosis and aneurysm. Traditionally, patients have undergone catheter-based angiography for diagnosis of re-stenosis or aneurysm formation.
This study evaluated 25 patients (mean age, 134 months) who had previously undergone coarctation repair (mean time after surgery, 109 months). All 25 patients had suspected re-stenosis on the basis of systolic blood pressure differential between the right upper and lower extremities or a flow jet in the postoperative segment of the aorta at echocardiography. Patients were examined with both catheter angiography and helical CT angiography. The CT data were displayed using maximum intensity projection (MIP) reconstructions. At the time of catheter angiography, Schaffler and colleagues measured systolic blood pressure gradients between the pre- and post-stenotic segments of the former coarctation.
On the basis of catheter angiography, 11 of 25 patients had a normal aortic contour (group A), 12 had a re-stenosis (group B), and two had an aneurysm at the surgical site (group C). In four patients a circumscribed pouch was demonstrated at the site of surgery, and an intimal flap was identified in four other patients. The mean time for performing MIP reconstructions was 15 minutes. The CT MIP reconstructions yielded identical results with respect to classification into the three groups (A,B, and C), circumscribed pouches, and intimal flaps. There was strong correlation between catheter angiography and CT angiography for measurement of the narrowest diameter in the area of former coarctation (r = 0.98) or in the descending aorta (r = 0.99). There was no correlation between the systolic pressure gradients found at catheter angiography and the ratio of the diameter of the former coarctation site to the diameter of the descending aorta (r = -0.04).
Schaffler et al concluded that CT angiography can replace catheter angiography for postoperative follow-up of aortic coarctation, and that catheter angiography should be reserved for patients who have abnormal findings on CT angiography that require endovascular intervention or surgery.
Comment by Gautham P. Reddy, MD
This study shows that a noninvasive technique can be as accurate as catheter angiography for postoperative evaluation of coarctation. The MIP reconstructions, which could be performed in a mean of only 15 minutes, provided diagnostic information nearly identical to that of catheter angiography.
Magnetic resonance imaging (MRI), which has been used for pre- and postoperative evaluation of coarctation for more than 10 years,1 is an alternative to CT angiography. Some advantages of MRI over CT angiography include the absence of ionizing radiation and the lack of need for iodinated contrast agent. In addition, velocity-encoded cine MRI can be used to evaluate the functional significance of the stenosis.2
Given the wide availability of CT angiography and MRI, there is no reason to perform routine catheter angiography for the postoperative monitoring of patients with coarctation. Catheter angiography should be reserved for patients who need an endovascular intervention or whose noninvasive imaging examination is technically suboptimal. Patients who need repeat surgery usually do not need diagnostic catheter angiography if the CT angiography or MRI is performed.
References
1. von Schulthess GK. Coarctation of the aorta: MR imaging. Radiology 1986;158:469-474.
2. Steffens JC, et al. Quantitation of collateral blood flow in coarctation of the aorta by velocity encoded cine MRI. Circulation 1994;90:937-943.
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