IJCS | Volume 33, Nº2, March / April 2020

DOI: 10.5935/2359-4802.20190085 Introduction Atrial fibrillation (AF) remains the most prevalent event in perioperative period of cardiac surgery, with an incidence varying from 20 to 50%, according to the electrocardiographic or cardiac monitoring method used. 1-4 Its incidence has continuously increased over recent decades despite advances of surgical and anesthetic techniques. 3 Postoperative AF (POAF) is associated with worse clinical outcomes, with great impact on health care costs. 1,4-10 Given the repercussions of AF, many investigations have been conducted to identify factors associated with the pathophysiology of AF, and thereby enable the development of preventivemeasures, guide the treatment of patients at greater risk, minimize the side effects of antiarrhythmic drugs and maximize the cost-benefit of the therapy. 6,11-13 Our group has previously published a study on risk factors for the development of POAF, including age over 70 years, mitral disease, non-use of beta-blocker therapy 158 ORIGINAL ARTICLE International Journal of Cardiovascular Sciences. 2020; 33(2):158-166 Mailing Address: Tiago Luiz Luz Leiria Av. Princesa Isabel, 395. Postal Code: 90620-000, Bairro Santana, Porto Alegre, RS – Brazil. E-mail: pesquisa.leiria@gmail.com ; drleiria@gmail.com Internal Validation of a Risk Score for Prediction of Postoperative Atrial Fibrillation after Cardiac Surgery Rafael de March Ronson i, T iago Luiz Luz Leiria , L eonardo Martins Pire s, M arcelo Lapa Krus e, Edemar Pereir a, Rogerio Gomes da Silva , G ustavo Glotz de Lim a Instituto de Cardiologia / Fundação Universitária de Cardiologia (IC/FUC), Porto Alegre, RS - Brazil Manuscript received on August 07, 2018; reviewed on June 11,2019; accepted on July 30,2019. Abstract Background: Postoperative atrial fibrillation (POAF) after cardiac surgery has great clinical and economic implications. Many attempts have been made to identify risk factors aiming at a better evaluation of prophylactic treatment strategies. Objective: To perform an internal validation of a risk score for POAF. Methods: A prospective cohort of 1,054 patients who underwent myocardial revascularization and/or valve surgery was included. The risk score model was developed in 448 patients, and its performance was tested in the remaining 606 patients. Variables with a significance level of 5% in the cohort were included and subjected to a multiple logistic regression model with backward selection. Performance statistics was performed using the c-statistic, the chi-square and the Hosmer-Lemeshow (HL) goodness-of-fit, Pearson's correlation coefficient. Results: Four variables were considered predictors of outcome: age (≥ 70 years), mitral valve disease, the non- use or discontinuation of beta-blockers and a positive water balance (> 1,500 mL). The ROC curve was 0.76 (95% confidenceinterval[CI]:0.72-0.79).Theriskmodelshowedagoodabilityaccordingtotheperformancestatistics– HL test x 2 = 0.93; p = 0.983 and r = 0.99 (Pearson's coefficient). Therewas an increase in the frequency of POAFwith the increase of the score: very low risk = 0.0%; low risk = 3.9%; intermediate risk = 10.9%; and high risk = 60.0%; p < 0.0001. Conclusion: The predictive variables of POAF allowed us to construct a simplified risk score. This scoring system showed good accuracy and can be used in routine clinical practice. (Int J Cardiovasc Sci. 2020; 33(2):158-166) Keywords: Atrial Fibrillation; Myocardial Revascularization; Heart Valves/surgery; Perioperative Care; Risk Score; Prevention and Control.