The use of high-field magnetic resonance in the follow-up of patients with mechanic aortic valve prosthesis and composite aortic tubular prosthesis

Eleven patients who had undergone cardiac surgery were studied by means of high-field MR imaging (1.5 T). Six patients had had aortic root and valve replaced with a Bj?rk-Shiley (BS) composite tubular aortic graft prosthesis for acute dissection of ascending aorta. In the other 5 patients with rheumatic calcific aortic disease, the valve had been replaced with a BS prosthesis. As a whole, MRI studies were 14. Previous evaluations of magnetic field effects had seem carried out ex vivo on both BS valves and BS composite prostheses, on surgical ligation clips (Tantalium and Stainless) and on stainless wires for sternal closure. In 4 patients (2 BS composite grafts and 2 BS valves) MRI diagnosed chronic dissection of both arch and descending aorta. In 1 of them, with a BS valve, associated localized acute dissection of ascending aorta was observed. In 3 patients with BS composite grafts, MRI revealed pseudo-aneurysms (including a thrombosed one) at the graft level. In one case MRI was repeated 4 times and was very helpful in monitoring the pseudo-aneurysm. MRI showed pericardial hematoma in 2 patients with BS grafts and paravalvular abscess in a case with BS valve. In one patient with BS valve fast-imaging MR revealed severe aortic regurgitation. No adverse reactions were demonstrated on MR images of prosthetic implants. MRI artifacts were insignificant with the spin-echo technique, while the fast-imaging technique showed clear image distortion at the valve level.