Coronary Artery Bypass Grafting Transit Time Flow Measurement: Graft Patency and Clinical Outcomes

Background: This subanalysis of the Randomized On-Off Bypass (ROOBY) trial examined transit time flow measurement (TTFM) use and its impact on graft patency and long-term clinical outcomes after coronary artery bypass graft surgery.

Methods: Use of TTFM for ROOBY centers and surgeons was assessed. Comparative patient outcomes based on TTFM use included 1-year graft patency and 1-year and 5-year major adverse cardiac events: all-cause mortality, nonfatal myocardial infarction, and revascularization (percutaneous coronary intervention or repeat coronary artery bypass graft surgery).

Results: Transit time flow measurement was used in 1067 patients (TTFM group) and not used in 501 patients (non-TTFM group); of the TTFM group, median percentage TTFM use was 79% (interquartile range, 41% to 98%) among 18 Veterans Affairs Medical Centers, and 74% (interquartile range, 13% to 98%) among 48 surgeons. Patients were comparable in age (63 ± 8.5 years TTFM vs 62 ± 8 years non-TTFM, P = .30) and estimated 30-day mortality risk (1.8 ± 1.7 TTFM vs 1.9 non-TTFM, P = .53). One-year FitzGibbon A patency was 83% (1600 of 1988 grafts) for TTFM assessed grafts and 78% (629 of 803) for non-TTFM assessed grafts (P < .01). Fewer TTFM patients had an occluded graft (29%, vs 38% non-TTFM; P = .01). Comparing TTFM patients with non-TTFM patients, 5-year major adverse cardiac event rates were 30% vs 25% (P = .06). Individual component rates were 14% vs 11% for death (P = .06), 12% vs 8.8% for myocardial infarction (P = .07), and 13% vs 12% for revascularization (P = .62).

Conclusions: The association of TTFM use with graft patency and clinical outcome is uncertain. Future randomized studies that account for patient risk factors and practice variation would help address this knowledge gap.