IJCS | Volume 32, Nº6, November / December 2019

592 Silva & Butcher Scores for prediction of AF after cardiac surgery Int J Cardiovasc Sci. 2019;32(6):585-593 Original Article between the two groups. In addition, we did not observe any relation with the type of surgical procedure, nor in relation to the other intraoperative variables in the groups with and without POAF. Several studies have demonstrated the association between arrhythmia and adverse postoperative outcomes. 23,25 A meta-analysis 23 with over 69 thousand patients showed that the length of stay was significantly higher among patients with and without POAF (11.0 vs 8.9 days, respectively; p < 0.00001). In coherence with the literature data, POAF patients, in this study, remained hospitalized for longer periods. Nevertheless, mortality rates were higher among patients without POAF. These results were surprising, but some hypothesis can help us understand them. Short-term follow-up compared to other studies who had followed the patients after hospital discharge can contribute to decrease the number of new-onset and recurrent cases of POAF, as well as the number of deaths. In a meta-analysis, the recurrence rate of POAF ranged from 61% to 100% within two years. 26 With respect to the estimation of the predictive capacity of the scores, the cut-off values of the CHADS 2 and CHA 2 DS 2 VASc scores that best discriminated patients with and without POAF were > 0.5 and < 3.5, respectively. In otherwords, patientswouldbe at risk of developing POAF even if they had relatively few risk factors. In this situation, it is possible that the scoreswould not be very useful for identifying patients that should receive more intensive monitoring in the postoperative period or other prophylacticmeasures. Corroborating that perspective, the sensitivity of the CHADS 2 score increased, but specificitywas extremely low; and for CHA 2 DS 2 VASc, they remained far below adequate. When assessing the effect of LA size on the predictive capacity of these scores, although the sensitivity of the CHADS 2 score has decreased, all the other measures of specificity, PPV and NPV improved, but did not seem to be satisfactory. Similarly, for the CHA 2 DS 2 VASc score, in spite of a decrease in the specificity value, there was an improvement in all the other measures, which is not enough to ensure its adequacy. Moreover, the regression models failed to show that the scores, alone or in association with the LA, are predictors of POAF. Therefore, it can be asserted that the models analyzed in this study are not good predictors of POAF. The literature is controversial regarding the determination of the predictive capacity of the CHADS 2 and CHA 2 DS 2 VASc scores. 8,9,10,13 Some studies have shown that the risk of POAF increased as the CHADS 2 and CHA 2 DS 2 VASc scores increased, but they did not demonstrate their predictive capacity. 9,10 Recently, researchers 13 have analyzed the predictive capcity of different risk scores (Society of Thoracic Surgeons risk of mortality score, Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE)-AF score, POAF score and CHA 2 DS 2 VASc) and age for the new- onset of AF after coronary artery bypass graft operation. They noted that none of the variables analyzed performed well. The ROC area for CHARGE-AF was 0.6796 (CI 95%: 0.6672-0.6920), whereas for CHA 2 DS 2 VASc it was 0.5917 (CI 95%: 0.5782- 0.6052). Different results were obtained in another study, 8 which showed good estimations on sensitivity (84.21), specificity (84.54) and negative predictive value (97.23) of the CHA 2 DS 2 VASc score to predict the risk of AF after coronary artery bypass, with a ROC area of 0.87. The present study has limitations relating to sample size and to the fact that this is a single-center study. Furthermore, the short follow-up period did not allow for the identification of new- onset and recurring AF after hospital discharge, whichmight have contributed to poor score performance in predicting arrhythmia, since the items of both scores take into account chronic conditions that can affect myocardial structure and stability in the long term after cardiac surgery. Conclusion The CHADS 2 and CHA 2 DS 2 -VASc scores alone were not good predictors of POAF in patients undergoing coronary artery bypass graft and/or valvular surgery in this study. Although LA size has improved the estimation of sensitivity, specificity, PPV and NPV, it was not enough to improve the predictive capacity of the scores. Author contributions Conception and design of the research: Silva NA, Butcher RCGS. Acquisition of data: Silva NA. Analysis and interpretation of the data: Silva NA, Butcher RCGS. Statistical analysis: Silva NA, Butcher RCGS. Writing of the manuscript: Silva NA, Butcher RCGS. Critical revision of the manuscript for intellectual content: Silva NA, Butcher RCGS.