Delayed muscle injuries in arterial insufficiency: Contrast-enhanced MR imaging and P-31 spectroscopy in rats

PURPOSE: To evaluate whether the vascular system resulting from an arterial lesion shows differences in permeability to a tracer with respect to the n ormal vascular system acid whether eventual differences are maintained for long periods. MATERIALS AND METHODS: Permanent ischemia was induced in rats with femoral arterial removal, and magnetic resonance (MR) imaging was performed after 1 , 7, 14, and 90 days. Gadopentetate dimeglumine was injected, and the kinet ics of its penetration in the leg were studied. Phosphorus 31 spectroscopy was performed to determine the bioenergetic characteristics of the gastrocn emius muscle at rest and stimulation. Ischemic muscles were then processed for electron microscopy. RESULTS: After ischemia induction, a hyperintense area that progressively d ecreased was present on T2-weighted images. Gadopentetate dimeglumine impro ved the signal intensity of the area. Three months after arterial occlusion , the contrast-enhanced images still showed microvessels highly permeable t o the tracers. Spectroscopic data revealed that 3 months after arterial rem oval, the bioenergetic reserve of the gastrocnemius muscle was reduced, sug gesting that the contrast-enhanced MR imaging-visible area is functionally relevant. Ultrastructural examination revealed persistent muscle damage and signs of chronic microangiopathy. CONCLUSION: After ischemia induction, the restitutio ad integrum is not com plete, and delayed muscle injuries can result from arterial insufficiency.