IJCS | Volume 32, Nº6, November / December 2019

586 Silva & Butcher Scores for prediction of AF after cardiac surgery Int J Cardiovasc Sci. 2019;32(6):585-593 Original Article diagnosis. 5 In addition, cognitive changes, heart failure and worsened quality of life have been reported. 6,7 Having tools for predicting the risk of developingAF in the postoperative period of cardiac surgery (POAF) may contribute to the implementation of measures designed to prevent and improve the monitoring of patients at risk. Different models have been tested to that end, 4,8,9 such as the CHADS 2 and CHA 2 DS 2 -VASc scores. 9-11 Although these scores have been originally developed to assess the risk of thromboembolism in patients with AF, their items include risk factors for the onset of arrhythmia itself. 1,2,12 However, the results of studies that have evaluated the predictive capacity of the CHADS 2 and CHA 2 DS 2 -VASc scores in relation to POAF are controversial. 9,10,13 Recently, a study demonstrated that left atrial (LA) size was the best variable to discriminate between patients with or without POAF. 14 To our knowledge, no study has assessed the contribution of LA size evaluation to the predictive ability of those scores. The objectives of this study were to verify the predictive capacity of the CHADS 2 and CHA 2 DS 2 -VASc scores for the onset of POAF in patients submitted to coronary artery bypass grafting and/or valvular surgery; and to assess the contribution of LA size to the predictive capacity of these scores. Methods This is a retrospective cohort study. Data were collected in the period from June 2017 to October 2017 at the Heart Institute of the Clinics Hospital of the School of Medicine of the University of São Paulo (INCOR- HC-FMUSP). Population of interest and sample collection The population of interest for this study included patients submitted to coronary artery bypass grafting and/or valvular surgery, either alone or in combination, during the year 2015. The sample of the study was determined as 144 patients, considering an incidence of POAF as high as 50%, number of surgical procedures performed in 2015 at the institution, area of data collection and assuming type I error of 5%. We includedmedical records of patients aged 18 years or more, who had undergone coronary artery bypass grafting and/or valvular surgery. We excluded the medical records of patients diagnosed with pre- or intraoperative AF, from those who had undergone other types of associated surgeries or whose medical records were lacking information needed for the development of this study. We located medical records for 1,225 individuals in the hospital’s electronic records system. Out of these, 234 were excluded (188 belonged to patients with a diagnosis of pre-operative AF and 46, to patients who had undergone other surgical procedures concomitantly). The other medical records (n = 991) were revised and divided into two groups: with POAF (n = 148) andwithout POAF (n = 843) and, subsequently, they received codes which were used to draw the final sample. In order tominimize the interference of external factors in this study, six medical records were chosen from the group with POAF and six from the group without POAF every month, for a total of twelve per month. The draw was carried out electronically (sorteador.com ). Therefore, each group was composed of 72 patient records. The study was conducted in accordance with the principles of the Declaration of Helsinki and approved by the Ethics Committee in Research (approval number 1.957.400). The need for informed consent formwaswaived because all data were obtained from the patient records. Variables The clinical and demographic variables analyzed were: age, sex, skin color, smoking, CHADS 2 and CHA 2 DS 2 -VASc scores, preoperative echocardiographic data (left atrial size, left ventricle diastolic diameter and left ventricular ejection fraction), use of continuous medication in the preoperative period, intraoperative data (type of cardiac surgery, time of anesthesia, use of extracorporeal circulation (ECC) and the time of ECC); and postoperative data (POAF diagnosis, immediate postoperative laboratory tests, in the immediate postoperative, length of stay and death). Postoperative and POAF data were analyzed during the whole period of hospitalization. The onset of arrhythmia in the postoperative period, registered in electronic medical record system, was considered an episode of POAF. CHADS 2 and CHA 2 DS 2 -VASc TheCHADS 2 scorewasproposedafter scientific evidence suggest that certain factors other thanAF contributed to the onset of thromboembolic phenomena in these patients. 5 The identification of the major factors associated with