Regular Article Risk of bleeding in low-risk atrial fibrillation patients on warfarin waiting for elective cardioversion Daniela Poli a, ⁎, Emilia Antonucci b , Elisa Grifoni b , Oriana Paoletti c , Elena Rancan d , Francesco Dentali d , Sophie Testa c a Thrombosis Centre, Dept of Heart and Vessels Azienda Ospedaliero-Universitaria Careggi, Florence, Italy b Dept of Medical and Surgical Critical Care, University of Florence, Florence, Italy c Haemostasis and Thrombosis Centre, A O Istituti Ospitalieri of Cremona, Cremona, Italy d Dept of Clinical Medicine, University of Insubria, Varese, Italy abstract article info Article history: Received 31 March 2011 Received in revised form 27 June 2011 Accepted 15 August 2011 Available online 4 October 2011 Keywords: Atrial fibrillation bleeding risk cardioversion thromboprophylaxis Vitamin K antagonist Introduction: Systemic embolism is the most serious complication of cardioversion of atrial fibrillation (AF) and the immediate post-cardioversion period is associated with increased risk for thrombus formation. For this reason, treatment with vitamin K antagonist (VKA) is recommended for patients with AF. No information is available about bleeding risk related to this practice. Methods: We performed a prospective multicentre study on 242 low-risk AF patients (CHADS 2 score 0–1) that started on warfarin for elective cardioversion to evaluate their bleeding risk. Results: 178 were males (73.6%), mean age 63.9 ± 9.8 years, 60 patients (25%) were aged ≤59 years. Patients with CHADS 2 score = 0 were 73 (30%), those with CHADS 2 score = 1 were 169 (70%). Patients were on VKA treatment, maintained at INR intended therapeutic range 2.0-3.0, for a median time of 159 days (range 30– 631)total follow-up period 127 patient-years (pt-yrs). Quality of anticoagulation and occurrence of bleeding events were recorded. Patients spent 23%, 64% and 8% of time below, within and above the intended thera- peutic range, respectively. When we observed the INR levels, we found that 62 patients (25.6%) had INR N 4.5 at least in one occasion, and 23 (9.5%) in ≥2. During follow-up, 2 patients had major bleeds (rate 1.6% pt-yrs), one fatal. No embolic complications were recorded. Conclusion: Our results show that low-risk AF patients, treated with VKA for elective cardioversion, carry a not irrelevant risk of bleeding. Efforts are required to properly select patients who could benefit from this procedure, reducing the time of warfarin exposure. © 2011 Elsevier Ltd. All rights reserved. Introduction Systemic embolism is the most serious complication of cardiover- sion for atrial fibrillation (AF) and the immediate post-cardioversion period is associated with increased risk for thrombus formation, with an increased risk of stroke and systemic embolism. The efficacy of anticoagulation in reducing the risk of stroke after cardioversion has been documented [1]. For this reason, treatment with vitamin K antagonist (VKA) is recommended for patients with AF lasting ≥48 h or of unknown duration for 3 weeks before elective cardiover- sion and for at least 4 weeks after [2,3]. Usually patients should be exposed to VKA treatment overall for about 2–3 months to safely per- form cardioversion. Cardioversion is planned for rhythm control in several different conditions, also with patients who need prolonged thromboprophylaxis. However, the procedure is frequently done also with low risk patients, who are therefore exposed to thrombo- prophylaxis only for cardioversion itself. Little information is avail- able about bleeding risk related to this practice [4]. Thus, we performed a prospective multicentre study on low-risk AF patients (CHADS 2 score 0–1) [5], starting warfarin for elective cardioversion to evaluate their bleeding risk. Methods Three Centers affiliated with the Italian Federation of Anticoagula- tion Clinics (FCSA) participated in the study: Thrombosis Centre (Florence); Department of Clinical Medicine (Varese) and Haemostasis and Thrombosis Centre (Cremona). Patients were followed-up by peri- odic INR measurements and prescription of daily VKA dosages, clinical history was collected as previously described [6]. All patients were Thrombosis Research 129 (2012) 588–590 Abbreviations: AF, atrial Fibrillation; INR, International Normalized ratio; IQR, inter- quartile range; pt-yrs, patient-years; SD, Standard deviation; TTR, time in therapeutic range; VKA, Vitamin K antagonist. ⁎ Corresponding author at: Thrombosis Center, Azienda Ospedaliera Universitaria- Careggi, Viale Morgagni, 85–50134, Firenze, Italy. Tel.: +39 055 7945453; fax: +39 055 7946218. E-mail address: polida@aou-careggi.toscana.it (D. Poli). 0049-3848/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2011.08.031 Contents lists available at SciVerse ScienceDirect Thrombosis Research journal homepage: www.elsevier.com/locate/thromres