Assessment of complicated arterial bypass grafts:: Value of contrast-enhanced subtraction magnetic resonance angiography

Purpose: To evaluate complicated aortoiliac and lower extremity arterial bypass grafts with contrast-enhanced subtraction magnetic resonance angiography (MRA). Methods: Twenty-three patients with 40 vascular grafts with either clinical symptoms or abnormal duplex findings were selected. They were examined using a fast T1-weighted gradient-echo sequence. Twelve to 19 coronal sections of 5 to 8 mm were acquired before and after an intravenous bolus injection of gadolinium (0.1 mmol/kg) in 25 to 40 seconds, Final images were created by subtracting each precontrast section from its corresponding postcontrast section. The MRA was obtained after subtraction and maximum intensity projection. Results: MRA detected 38 grafts (95%) with 28 abnormalities. Two stenoses were overestimated. MRA had a sensitivity of 91% and a specificity of 92% for diagnosis of graft stenoses and occlusions. MRA brought out more information in five cases by demonstrating four nonthrombotic ectasias that were unseen by duplex sonography and one thrombotic ectasia that was unseen by x-ray angiography. Conclusions: MRA seems to compare favorably with x-ray angiography for the diagnosis of arterial bypass graft complications. A multicenter trial will be necessary to validate these preliminary results and to assess the exact role of MRA, compared with the other established techniques.