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

PURPOSE: To evaluate whether the vascular system resulting from an arteriallesion shows differences in permeability to a tracer with respect to the normalvascular system and whether eventual differences are maintained for long periods.MATERIALS AND METHODS: Permanent ischemia was induced in rats with femoralarterial removal, and magnetic resonance (MR) imaging was performed after 1, 7,14, and 90 days. Gadopentetate dimeglumine was injected, and the kinetics of its penetration in the leg were studied. Phosphorus 31 spectroscopy was performed to determine the bioenergetic characteristics of the gastrocnemius muscle at restand stimulation. Ischemic muscles were then processed for electron microscopy.RESULTS: After ischemia induction, a hyperintense area that progressivelydecreased was present on T2-weighted images. Gadopentetate dimeglumine improvedthe signal intensity of the area. Three months after arterial occlusion, thecontrast-enhanced images still showed microvessels highly permeable to thetracers. Spectroscopic data revealed that 3 months after arterial removal, thebioenergetic reserve of the gastrocnemius muscle was reduced, suggesting that thecontrast-enhanced MR imaging-visible area is functionally relevant.Ultrastructural examination revealed persistent muscle damage and signs ofchronic microangiopathy.CONCLUSION: After ischemia induction, the restitutio ad integrum is not complete,and delayed muscle injuries can result from arterial insufficiency