[Magnetic resonance with the spin-echo technic in the noninvasive evaluation of the patency of aortocoronary bypasses: preliminary data].

Abstract

Patients with previous coronary artery bypass graft surgery often develop chest pain due to ischemic or nonischemic causes. Noninvasive evaluation of graft patency is thus of obvious potential importance.
In order to assess the efficacy of magnetic resonance imaging (MRI) in evaluating graft patency after coronary artery bypass graft surgery, 16 patients with prior surgery and history of chest pain were studied prospectively by coronarography and MRI. These 16 patients with a total of 40 grafts were evaluated, using MRI with Spin-Echo T1 technique within 3.6 +/- 4.4 days from coronarography with a 0.5 Tesla magnet, cardiac and respiratory gating and scannings in transaxial planes. A graft was defined as patent if a signal void was identified in at least two different slices in a position consistent with a bypass graft. Images were analyzed by two different observers aware of the type of surgery but not the result of the coronarography.
Thirty-six out of the 40 grafts were classified correctly by MRI. Twenty-eight grafts were patent as shown by coronarography; 26 of them were classified correctly by MRI. Twelve grafts were shown as occluded; 10 of them were classified correctly by MRI. In particular, all of the 14 grafts to the left anterior descending artery (3 of them using the internal mammary artery), 13/16 of the grafts to the left circumflex artery and 9/10 of the grafts to the right coronary artery were classified correctly.
This study demonstrates the capability of MRI to evaluate coronary artery bypass graft patency with a sensitivity of 92.8% and specificity of 83.3%; this technique has significant clinical limitations because resolution is not adequate to evaluate the presence of graft stenosis.