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[2D-phase contrast flow evaluation and contrast-enhanced MR angiography for perioperative assessment of internal mammary artery grafts].

PURPOSE
To evaluate LV functional parameters, graft flow and patency in patients with IMA grafts using a combined MR protocol with phase-contrast technique and contrast enhanced MR angiography.


MATERIAL AND METHODS
Using a 1.5 T MR system 27 patients with 27 left internal mammary artery (LIMA) and 41 venous grafts were examined before and 6 months after CABG surgery. A T(1)w-TSE sequence (slice thickness 5 mm) was applied for morphological imaging. LV function (EF, CO) was evaluated on cine images (segmented FLASH 2D, TR(eff) 11 ms, TE 4.8 ms, flip angle 25 degrees ). A phase-contrast FLASH 2D (TR 24 ms, TE 5 ms, flip angle 20 degrees ) sequence was applied for aortic and IMA flow measurements. Postoperatively, a contrast enhanced FLASH 3D MR angiography (TR 3.8 ms, TE 1.4 ms, flip angle 30 degrees ) with 25 ml Gd-DTPA was performed to assess bypass patency.


RESULTS
In patients with reduced LV function (ejection fraction < 50 %) an improvement of the ejection fraction from 38.4 +/- 10.3 % to 49.8 +/- 15.3 % (p < 0.05) was found postoperatively. LIMA grafts were occluded in 1/27 patients, while 6/41 venous grafts were occluded. Distal LIMA anastomoses were demonstrated in 33 % by MRA. Flow of LIMA decreased from 21.2 +/- 11 ml/min/m(2) preoperatively to 14.4 +/- 9.6 ml/min/m(2) postoperatively (p < 0.01).


CONCLUSION
MR imaging allows accurate combined assessment of LV function, bypass patency and flow. The protocol of this study may be applicable for perioperative follow-up studies in patients after CABG surgery.