Background: Electrical cardioversion (ECV) in patients with atrial fibrillation (AF) is known to be associated with an increased peri-procedural risk for thromboembolic events. ECV of AF for at least 3 weeks of effective oral anticoagulation was recently determined to be disassociated with occurrence of cerebral circulating microemboli (ME). Nonetheless, whether ECV in patients undergoing short-term anticoagulation with heparin is concomitant with cerebral ME still remains obscure. The objective of this study was to determine whether or not short-term anticoagulation with heparin helps avoid microemboli before and immediately after cardioversion of AF in patients undergoing transesophageal echocardiography (TEE)-guided ECV Method: A total of 34 patients (21 women, aged 61 +/- 12 years) who underwent TEE-guided ECV were enrolled into the study. All the patients underwent treatment with heparin for 3 days for anticoagulation before ECV Transcranial Doppler ultrasonography (TCD) of the right middle cerebral artery and left middle cerebral artery was simultaneously performed through the temporal skull with a two-channel 2-MHz probe in all patients lasting for 30 min before ECV and 30 min immediately after successive ECV Results: No ME were detected in 34 patients during the 30-min period during AF before ECV. Similarly, after ECV no ME were observed during 30-min monitoring in 27 patients who were converted to sinus rhythm. None of the patients presented with clinical signs or symptoms suggestive of manifest cerebral embolism either before or after ECV Conclusion: TCD monitoring did not disclose any evidence of microemboli in short-term anticoagulated patients with heparin before and immediately after TEE-guided ECV. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.