Fourteen-year follow-up from CABADAS: vitamin K antagonists or dipyridamole not superior to aspirin

Background: Secondary prophylaxis using aspirin is standard of care after coronary artery bypass graft surgery. Limited data are available for long-term results. We evaluated the effect of aspirin, aspirin with dipyridamole, and vitamin K antagonists (VKA) on 14-year clinical outcome of patients included in the Prevention of Coronary Artery Bypass Graft Occlusion by Aspirin, Dipyridamole, and Acenocoumarol/Phenprocoumon Study (CABADAS).

Methods: All 726 Dutch patients for whom antithrombotic therapy with aspirin (n = 248), aspirin with dipyridamole (n = 234), or VKA (n = 244) was randomly allocated were included. The primary endpoint was occurrence of major adverse cardiac events (MACE). Outcomes were retrospectively evaluated during 14-year follow-up.

Results: Cumulative incidences for MACE over 14 years were 49%, 50%, and 59% for patients treated with aspirin, aspirin with dipyridamole, and VKA, respectively. Although the overall occurrence of MACE did not significantly differ among the three treatment groups (p = 0.12), patients treated with VKA were at higher risk of MACE than patients treated with aspirin with dipyridamole (hazard ratio 1.3, 95% confidence interval: 1.0 to 1.8, p = 0.041) and patients treated with aspirin alone (hazard ratio 1.1, 95% confidence interval: 0.86 to 1.5, p = 0.37). This difference was attributed to an increased risk of repeat revascularization in patients treated with VKA, without any differences in cardiac death and myocardial infarction among the three treatment groups. However, the observed high rate of repeat revascularization in patients treated with VKA could reflect an a priori increased probability for repeat revascularization due to the specific conditions surrounding VKA therapy (ie, more intense patient-doctor contacts).

Conclusions: This study with 14-year clinical outcome provides further evidence for the use of aspirin as secondary prophylaxis after coronary artery bypass graft surgery.