Letter to the Editor Association between red blood cell distribution width and postoperative atrial fibrillation after cardiac surgery: A pilot observational study Panagiotis Korantzopoulos a, ⁎, Nikolaos Sontis a , Tong Liu b , Serafeim Chlapoutakis c , Sokratis Sismanidis c , Stavros Siminelakis c , Efstratios Apostolakis c a Department of Cardiology, University of Ioannina Medical School, 45110 Ioannina, Greece b Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, People's Republic of China c Department of Cardiothoracic Surgery, University of Ioannina Medical School, 45110 Ioannina, Greece article info Article history: Received 25 January 2015 Accepted 6 March 2015 Available online 10 March 2015 Keywords: Postoperative atrial fibrillation RDW Prognostic marker Cardiac surgery Coronary artery bypass grafting Valve surgery To the Editor: Postoperative atrial fibrillation (POAF) after cardiac surgery repre- sents a very common complication that seems to have a significant im- pact on both short- and long-term patient outcomes [1,2]. Several clinical and laboratory factors have been suggested to have predictive value in this setting [1]. On the other hand, red blood cell distribution width (RDW) has been independently associated with cardiovascular risk and mortality [3,4]. RDW is a marker of anisocytosis of erythrocytes and may be related to inflammation and oxidative stress. Apart from cardiac surgery-induced inflammatory and oxidative response, preop- erative oxidative and inflammatory status may also play a role in the pathogenesis of POAF [5,6]. Moreover, recent evidence suggests that RDW is associated with AF in non-surgical patients [7–9]. Thus, the aim of the present pilot study was to prospectively evaluate the poten- tial association of RDW with POAF as well as to examine its relative value compared to other conventional inflammatory indexes. Consecutive adult patients (N 18 years old) planned for elective car- diac surgery (on-pump coronary artery bypass and/or valve surgery) from June 2013 to August 2014 were prospectively screened. Exclusion criteria were emergency cardiac surgery, previous history of AF, chronic rheumatic and inflammatory conditions, thyroid dysfunction, hepatic dysfunction/liver diseases, alcohol overuse, electrolyte disturbances, in- take of anti-inflammatory drugs or antioxidant supplements, malignan- cies and hematologic dyscrasias, recent infection, recent acute coronary syndrome, and antiarrhythmic drug use (besides β-blockers). Patients with left atrial diameter N 50 mm, LVEF b 30%, or NYHA class N III were also excluded. Baseline demographic, clinical, echocardiographic, and laboratory pa- rameters were carefully recorded. Conventional inflammatory indexes such as white blood cell (WBC) count and C-reactive protein (CRP) were also assessed. In specific, the laboratory examinations including complete blood count and biochemical investigations were performed in the morning hours at the fasting state before the operation. The hema- tologic parameters including RDW and mean platelet volume (MPV) were determined using a Coulter counter. CRP levels were assessed using a high sensitivity immunonephelometric assay (Beckman Coulter/ IMMAGE Immunochemistry Systems, Behring Diagnostics Inc., Somer- ville, New Jersey, USA). The biochemical tests were accomplished using standard analytical methods. All measurements were performed blindly to patients' characteristics and treatment. A transthoracic echocardiographic examination was performed in each patient one day before the scheduled surgical operation using a GE Vivid 7 machine. The left ventricular ejection fraction (LVEF) was cal- culated by the Simpson's method. Left atrial (LA) diameter was deter- mined from the parasternal long-axis view at end-systole. The endpoint was the incidence of AF lasting more than 5 min during hospitalization (defined as POAF). The Local Ethics Committee approved the study protocol while written informed consent was obtained from all patients. The final study population consisted of 109 patients (79 men) with a mean age of 66.9 ± 9.5 years. Thirty four patients were not included ac- cording to the predefined exclusion criteria. The demographic and clin- ical characteristics were comparable between patients who developed POAF (n = 44) and those who remained in sinus rhythm (n = 65) (Table 1). However, there was a statistical trend for increased POAF in valvular surgery patients (p = 0.09). With regard to echocardiographic and laboratory parameters, no significant differences were observed apart from the RDW values that were greater in POAF patients and the E/E′ values (Table 2). The multivariate logistic regression analysis International Journal of Cardiology 185 (2015) 19–21 ⁎ Corresponding author. E-mail address: p.korantzopoulos@yahoo.gr (P. Korantzopoulos). http://dx.doi.org/10.1016/j.ijcard.2015.03.080 0167-5273/© 2015 Elsevier Ireland Ltd. All rights reserved. Contents lists available at ScienceDirect International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard