Early Silent Graft Failure in Off-pump Coronary Artery Bypass Grafting: A Computed Tomography Analysis

Objectives: Prevalence of early silent bypass occlusion after OPCAB demonstrates a gray zone and may affect the short-term results. The purpose was to assess predictors of graft failure prior to discharge by non-invasive multi-slice computed tomography (CT).

Methods: From 01/17 till 08/17, 122 asymptomatic patients after OPCAB underwent CT during the first postoperative week. In total, 218 arterial and 199 venous grafts were evaluated. Patients, who underwent postoperative coronary angiography because of suspected perioperative infarction, were excluded. Two groups (patent (n = 94) vs occluded (n = 28)) could be compared. Cardiovascular risk factors, collateralization of native vessels using the Rentrop classification, grade of native vessel stenosis, flow and pulsatile index (PI) were analyzed. Numeric variables presented as median (interquartile range). Inferential statistics were performed with Mann-Whitney U-test. Nominal and categorical variables were tested with Fisher-Freeman-Halton exact test.

Results: In 28 patients, at least one occluded graft could be identified with a tendency to female gender (p = 0.06). The number of distal anastomosis was 3.4 for the patent and 3.6 for the occluded group (p = 0.31). The use of both internal thoracic arteries was 60.2% in the patent and 62.1% in the occluded group (p = 0.29). The patency of all arterial grafts was 95.9%, of venous grafts 86%. In detail, 9 occluded arterial grafts and 28 venous grafts were found. For 13 of the occluded bypasses the decision for an intervention or stenting was made. There were significant differences in flow and PI with lower flow and higher PI in the occluded group (flow p = 0.006; PI p = 0.0001). No impact of collateralization or grade of native vessel stenosis on bypass occlusion could be found.

Conclusion: Early silent graft failure occurred predominantly in venous grafts with a tendency to female gender. Low flow and high PI measurements ask for a precise evaluation of the quality of anastomoses.

Table 1 Bypass characteristics

Bypass Characteristics	patent n = 380	occluded n = 37	p
Stenosis grade (target vessel) (%)	90 (80 - 95)	90 (75 - 99)	0.996
Flow (ml/min)	34 (24 - 49)	26.5 (18 - 37)	0.0064
Pulsatile Index	1.8 (1.4 - 2.3)	2.75 (1.7 - 4.1)	0.0001
Collaterals (Rentrop) (%)			0.6225
- 0	320 (84.4)	30 (78.9)
- 1	12 (3.2)	1 (2.6)
- 2	14 (3.7)	2 (5.2)
- 3	33 (8.7)	5 (13.3)
Sequential anastomoses (>1) (%)	119 (31.4)	15 (39.5)	0.4808