Can patients chronically anticoagulated with warfarin for nonrheumatic atrial fibrillation, with a history of an embolic event such as a TIA or CVA more than 1 year ago, safely be taken off anticoagulation in the preoperative state, or should they have a bridge with low-molecular-weight heparin (LMWH) both pre- and postoperatively until the INR is once again at a therapeutic range?
Response from Gerald W. Smetana, MD
The management of anticoagulation in the perioperative period varies based on the intrinsic risk of thromboembolic events due to patient-related risk factors. When risk of perioperative stroke or other arterial thromboembolic events is due to atrial fibrillation, clinicians may refine the risk estimate by use of such risk factors. High-risk factors for embolic events include prior stroke, TIA, or other arterial embolus, hypertension, impaired left ventricular systolic function, age > 75 years, rheumatic mitral valve disease, and prosthetic valves. Moderate-risk factors include age of 65-75 years, diabetes mellitus, and coronary artery disease with preserved left ventricular function.
Patients with atrial fibrillation who are at higher risk for stroke or other embolic events in the nonsurgical setting likewise carry a higher risk of embolic events in the perioperative period.
The patient in this query is a patient with a history of TIA or stroke who, by the above definitions, would be at high risk for embolic events. The 6th American College of Chest Physicians (ACCP) consensus conference on antithrombotic therapy recently proposed guidelines for perioperative management of anticoagulation. This guidelines suggest the use of bridging full-dose unfractionated heparin or full-dose LMWH for patients at high risk for perioperative embolic events. The recommended strategy is to discontinue warfarin 4 days before surgery, and to begin heparin or LMWH as the INR falls (approximately 2 days before surgery), then to discontinue heparin 5 hours before (or LMWH 12-24 hours before) surgery. Heparin (or LMWH) is resumed as soon as possible after surgery in addition to warfarin, and is continued until the INR has been therapeutic for 48 hours. An earlier review also supported preoperative heparin for high-risk patients while the INR was subtherapeutic off warfarin, but recommended restricting postoperative heparin coverage to high-risk patients whose risk of bleeding was low.
LMWH is an attractive potential alternative to intravenous unfractionated heparin due to its ease of use and the avoidance of a lengthy and costly hospital stay. The ACCP consensus recommendation to consider this as an alternative to intravenous heparin was based on 3 small studies that showed low rates of thrombotic events (1 patient out of 154) and of bleeding complications (4 patients out of 154).
Medscape Internal Medicine. 2003;5(1) © 2003 Medscape
Cite this: Gerald W Smetana. Preoperative Anticoagulation for Patients With Atrial Fibrillation - Medscape - Feb 03, 2003.