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The Graft Imaging to Improve Patency (GRIIP) Trial Results
Steve Singh, Nimesh Desai, Genta Chikazawa, Hiroshi Tsuneyoshi, Visal Pen, Jessica Vincent, Jennifer Ku, Fuad Moussa, Gideon Cohen, George Christakis, Stephen E. Fremes; Sunnybrook Health Sciences Centre, Toronto, ON, Canada
READER COMMENTS
Objective: The primary objective was to determine if intra-operative graft assessment, with criteria for graft revision, can decrease the proportion of patients with ≥1 total (100%) graft occlusions 1 year post-operatively. Secondary objectives were to determine if intra-operative graft flow assessment can decrease: i) the proportion of patients with ≥1 graft stenoses (50-99%); ii) the proportion of patients with complete graft occlusion or stenosis; and iii) the frequency of perioperative and 1 year major adverse cardiac events (MACE).
Methods: This a single-centre, randomized, single-blinded controlled clinical trial. Patients were randomized to receive intra-operative graft patency assessment using indocyanine green fluorescent angiography and transit-time flowmetry and graft revision according to specific criteria, or serve as controls receiving standard intra-operative management. Patients underwent conventional X-ray or 64 slice CT angiography post-operatively.
Results: Between September 2005 and August 2008, 156 patients undergoing isolated CABG surgery were enroled (Imaging n=76, Control n=76). The groups were similar in terms of demographic and angiographic characteristics. On-pump CABG was performed in all but 12 patients. Operative, cross clamp and cardiopulmonary bypass times were all non-significantly longer in the Imaging patients. The number of grafts constructed in the 2 groups were similar (Imaging: 3.0±0.7 grafts/pt; Control: 3.0±0.6 grafts/pt). There were no significant differences between the 2 groups in the incidence of perioperative events. Overall, the 1 year MACE (death, MI, PCI, redo CABG) was similar in the Imaging (12.7%) and the Control (9.4%) patients (p=0.55). Post-operative X-ray (n=23) or CT angiography (n=61) was performed in 43 Imaging patients at 9.6 ± 8.7 months following surgery and 41 Control patients at 11.5 ± 8.9 months post-operatively. Graft occlusion results are presented in the Table. The proportion of patients with ≥1 graft occlusions was similar between the 2 groups [25.6% in the Imaging group (11/43 patients) and 31.7% in the Controls (13/41 patients)] as was the incidence of the other graft patency endpoints. The incidence of saphenous vein graft occlusion was high in both the Imaging and Control patients.
Conclusion: Routine intra-operative graft assessment is safe, but does not lead to a marked improvement in graft patency 1 year post-CABG. The incidence of saphenous vein graft failure is high even with routine intra-operative graft surveillance.


Imaging(n=43) Controls(n=41) RR (95% CI) p-value
Total # grafts 125 120
PRIMARY ENDPOINT
Graft occlusions, No. (%) 15/125 (12.0) 16/120 (13.3) 0.90 (0.47-1.74) 0.75
Saphenous vein grafts, No. (%) 15/59 (25.4) 14/63 (22.2) 1.14 (0.61-2.16) 0.68
Arterial grafts, No. (%) 0/66 (0) 2/57 (3.5) 0.19 (0.01-3.90) 0.28
Patients with ≥ 1 graft occlusion, No. (%) 11/43 (25.6) 13/41 (31.7) 0.81 (0.41-1.59) 0.54
SECONDARY ENDPOINTS
Grafts with >50% stenosis, No. (%) 4/125 (3.2) 5/120 (4.2) 0.77 (0.21-2.79) 0.69
Saphenous vein grafts, No. (%) 1/59 (1.7) 4/63 (6.3) 0.27 (0.03-2.32) 0.23
Arterial grafts, No. (%) 3/66 (4.5) 1/57 (1.8) 0.86 (0.18-4.11) 0.85
Patients with ≥ 1 graft with >50% stenosis, No. (%) 3/43 (7.0) 5/41 (12.2) 0.56 (0.14-2.19) 0.40
Grafts with >50% stenosis or occlusion, No. (%) 19/125 (15.2) 21/120 (17.5) 0.87 (0.49-1.53) 0.63
Saphenous vein grafts, No. (%) 16/59 (27.1) 18/63 (28.6) 0.95 (0.54-1.68) 0.86
Arterial grafts, No. (%) 3/66 (4.5) 3/57 (5.3) 0.86 (0.18-4.11) 0.85
Patients with ≥ 1 graft with >50% stenosis or occlusion, No. (%) 13/43 (30.2) 17/41 (41.5) 0.73 (0.41-1.30) 0.29

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