OBJECTIVE:

Graft patency is the primary determinant of survival after CABG. Modern angiography studies reveal that 5-11% of grafts are occluded perioperatively. These early graft failures are usually due to technical errors that are preventable. The purpose of this investigation was to compare the sensitivity and specificity of two technologies: transit time ultrasound flow measurement(TTF) and indocyanine green(ICG) fluorescent-dye angiography, to detect intraoperative graft errors. We used x-ray angiography as a 'gold standard'.

METHODS:

Patents undergoing isolated CABG with no contraindications for postoperative angiography were enrolled. Patients were intraoperatively randomized to receive patency assessment with either 1: ICG angiography (Novadaq Spy™ system) then TTF (Medtronic Butterfly™) or 2: TTF then ICG angiography(i.e crossover study design). Patients underwent x-ray angiography on postoperative day 4. The primary endpoint was to compare the sensitivity and specificity of the two techniques versus gold standard x-ray angiography to detect >50% stenosis at any anastomosis, in the graft body, or in the first 1 cm distal to the distal anastomosis. The study was powered to detect a 10% difference in sensitivity between techniques. We apriori anticipated 50% of randomized patients would be able to undergo x-ray angiography.

RESULTS:

The data presented below are from a pre-planned interim analysis performed at 50% recruitment. At the time of interim analysis, 53 patients were enrolled in the trial and underwent intraoperative patency assessment. 27 of these patients went on to receive x-ray angiography of 28 internal mammary arteries, 20 radial arteries and 39 saphenous veins. In the 87 grafts studied, the sensitivity for detecting >50% stenoses was 100% for ICG angiography and 25% for TTF, p=0.04. The sensitivity for detecting total occlusion was 100% for both techniques. Specificity for detecting >50% stenoses was 100% for ICG angiography and 80% for TTF,p=0.1. Specificity for total graft occlusion was 100% for both techniques. See Figure for a representative ICG angiography image. TTF flow in the depicted graft was within normal parameters.

CONCLUSIONS:

ICG angiography provides superior sensitivity and specificity for detecting hemodynamically significant graft errors. TTF appears limited in its ability to discriminate lesions that are >50% stenotic but not totally occluded. Final results of this trial will be presented at the meeting.

Comparison of ICG and X-Ray angiography of a kinked
vein bypass graft

Presented at: The American Association of Thoracic Surgeons (AATS) 85^th Annual Meeting, C. Walton Lillehei Resident Forum Session - San Francisco, California, April 10, 2005