HYPOTHESIS: Early cardioversion from atrial fibrillation can be safely performed using a short-term anticoagulation strategy of low molecular weight heparin (Lovenox, Sanofi-Aventis) compared to unfractionated heparin, accompanied by a TEE examination prior to cardioversion. The use of LMWH with TEE will result in a safe, cost-effective, and possible efficacious approach to cardioversion of atrial fibrillation compared to UFH with TEE.