A study reported in the New England Journal of Medicine was conducted to compare outcomes for radial arterial grafts and saphenous-vein grafts in coronary artery bypass surgeries (Gaudino et al. 2018). Read this excerpt from the study abstract and answer the questions that follow. Methods: We performed a patient-level combined analysis of randomized, controlled trials to compare radial-artery grafts and saphenousvein grafts for coronary artery bypass grafting (CABG). Six trials were identified. The primary outcome was a composite of death, myocardial infarction, or repeat revascularization. 

Results: A total of 1036 patients were included in the analysis(534 patients with radial-artery grafts and 502 patients with saphenousvein grafts). After a mean (;SD) follow-up time of 60 ; 30 months, the incidence of adverse cardiac events was significantly lower in association with radial-artery grafts than with saphenous-vein grafts (95% confidence interval [CI], 0.49 to 0.90; P = 0.01). As compared with the use of saphenous-vein grafts, the use of radial-artery grafts was associated with a nominally lower incidence of myocardial infarction (95% CI, 0.53 to 0.99; P = 0.04) and a lower incidence of repeat revascularization (95% CI, 0.40 to 0.63; P = 0.001) but not a lower incidence of death from any cause (95% CI, 0.59 to 1.41; P = 0.68).

a. Which graft method had more positive outcomes? Explain.

b. There was an outcome for which one method did not have significantly better outcomes than the other. What outcome was this and how does the p-value support this conclusion?