The role of magnetic resonance in the evaluation of functional results after CABG/PTCA.

Magnetic resonance imaging (MRI) is a non-invasive modality which can be used for direct visualization of coronary artery bypass grafts. Spin-echo and gradient-echo (cine-MRI) techniques are now available on standard MR machines and provide information on graft morphology and graft patency with a 90% accuracy. By combining the standard techniques with MR phase velocity mapping, the flow rate in the graft can be measured, thereby offering a unique non-invasive assessment of the graft function. Newer techniques include MR coronary angiography, pharmacologically induced stress MRI, ultrafast MRI of the first-pass (perfusion) of a paramagnetic contrast agent through the myocardium, and 31P MR spectroscopy of high-energy phosphate metabolism of the myocardium. All of these may develop into valuable diagnostic tools for the assessment of functional results after CABG or PTCA, but still require clinical validation. At present, MRI is a useful screening procedure for assessment of graft patency and function in post-operative pain syndromes and in late graft occlusion or stenosis.