Interference with anticoagulation monitoring by procainamide-induced lupus anticoagulant.

A patient scheduled for coronary revascularization was discovered to have elevated partial thromboplastin and activated clotting times. Preoperative testing revealed a lupus anticoagulant, probably secondary to long-term procainamide therapy. The resultant inability to use conventional anticoagulation monitoring for cardiopulmonary bypass was solved by direct measurement of heparin concentration. Operation and recovery were uneventful, and the patient was treated with long-term warfarin anticoagulation for this hypercoagulable state.