[Morphological and functional MRI studies after correction of aortic isthmus stenosis]

To compare the results of different methods for postoperative assessment after coarctation repair by magnetic resonance imaging and to evaluate their reliability. The morphometric results are contrasted to functional parameters of CW Doppler, oscillometric pressure gradient and flow quantification in VEC-MRI.

54 patients (age: 6 to 36 years) were assessed by MRI 3 to 31 years after coarctation repair. The aortic diameters were compared to growth-dependent normal values and to the diameter of the ascending (AA) and descending aorta (DA), and their mean values (MV).

Patients after coarctation repair had mostly subnormal diameters of AA (mean value: 80% of normal) and AD (95% of normal). Compared to the control group, mean dispersion of AD diameters was significantly larger in the patient group (2.6 vs. 1.5 mm, p < 0.001). Degree of stenosis varied with the method. It was similar when using normal values and the diameter for DA, but dispersion was smaller when normal values were used. Correlation of the functional parameter to the degree of stenosis was weak. The highest correlation (r = 0.78) was reached when using normal values as the reference with mean cross-sectional velocity from VEC-MRI.

The use of normal values as the reference for quantification of residual coarctation is more reliable than common methods. Since only one measurement is needed, it seems to be less susceptible to errors and more practical. MRI offers not only a tool for accurate morphologic assessment, but with VEC-MRI it is also possible to obtain a functional parameter which is superior to oscillometric pressure gradient and CW Doppler.