Douketis J et al. N Engl J Med 2015; 373:823-33. DOI: 10.1056/NEJMoa1501035
"In conclusion, in the BRIDGE trial, we found that for patients with atrial fibrillation who require temporary interruption of warfarin treatment for an elective operation or other elective invasive procedure, a strategy of forgoing bridging anticoagulation was noninferior to perioperative bridging with low-molecular-weight heparin for the prevention of arterial thromboembolism. The strategy of forgoing bridging treatment also decreased the risk of major bleeding."
http://www.nejm.org/doi/pdf/10.1056/NEJMoa1501035