IJCS | Volume 32, Nº6, November / December 2019

587 Table 1 - Demographic and clinical characteristics recorded in the postoperative period of patients with (n = 72) and without (n = 72) postoperative atrial fibrillation With POAF Without POAF p-value Age, in years, mean (SD) 65.8 (10.7) 61.8 (13.3) 0.050* Male gender, n(%) 44 (61.1) 47 (65.3) 0.604† Skin color, n(%) 0.678† White 61 (84.7) 61 (84.7) Other 11 (15.3) 9 (12.5) Not informed 2 (2.8) Active smoking, n(%) 9 (12.5) 12 (16.6) 0.478† Preoperative echocardiographic data Left atrial size, in mm, mean (SD) 43.4 (6.6) 41.3 (6.3) 0.059* LVDd, mm, mean (SD) 53.3 (7.7) 52.1 (7.0) 0.359* LVEF %, mean (SD) 55.3 (12.4) 59.2 (10.6) 0.045* POAF: postoperative atrial fibrillation; SD: standard deviation; LVDd: left ventricular diastolic diameter; (*) Student’s t-test; (†) Pearson’s chi-square test. Silva & Butcher Scores for prediction of AF after cardiac surgery Int J Cardiovasc Sci. 2019;32(6):585-593 Original Article thromboembolism culminated with the publication in 2001 of this risk score. 12 The main purpose was to identify outpatients at risk who could benefit from treatment with oral anticoagulants. CHADS 2 , however, identifies high- risk patients. Nevertheless, due to the inherent risks of arrhythmia itself, as well as to the particular contribution of other risk factors for the onset of thromboembolism, the CHA 2 DS 2 -VASc score was proposed to identify real low risk patients who did not need anticoagulation. 5 The CHADS 2 score consists of four items that count for one point each (congestive heart failure, age > 75 years and diabetesmellitus) and one item that counts as 2 points (stroke and transient ischemic attack). The total score ranges from zero to six points. Originally, the higher the score, the higher the risk of thromboembolic phenomena. 12 The CHA 2 DS 2 -VAS c s c o r e i nc l ude s t h r e e additional factors (vascular disease, age 65-74 years and female gender); each additional factor counts as 1 point, while an age > 75 years was upgraded to two points. The total score ranges from zero to nine. Originally, the higher the score, the higher the risk of thromboembolic phenomena. 15 Data analysis Categorical variables were described by absolute and relative frequencies, and analyzed using Chi-square test and Fisher’s exact test. Quantitative variables were described by using central tendency and dispersion measurements and Student’s t-test. The cut-off values of the CHADS 2 and CHA 2 DS 2 -VASc sores and LA size were determined via decision tree. The predictive capacity of the scores alone and in combination with the LA size was determined by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and logistic regression models. The assumption of normality of the scores was not tested, because they are discrete variables. The adjustment of the models was evaluated by the area under (AUC) the Receiver Operating Characteristic (ROC) curve. All analyses were performed using the statistical software R 3.4.3. The significance level adopted was 5%. Results We selected 144 medical records of patients submitted to coronary artery bypass grafting and/or valvular surgery in 2015, half of whom had developed POAF. The demographic and clinical characteristics of interest, registered in the preoperative period, are described in Table 1. Although table 1 does not show statistically significant difference between patients with and without POAF, in relation to age, it is possible to consider that, clinically,