ABC | Volume 113, Nº5, November 2019

Original Article Congo et al. New-Onset atrial fibrillation in STEMI Arq Bras Cardiol. 2019; 113(5):948-957 myocardial infarction included consecutively in a national multicenter Portuguese registry on Acute Coronary Syndromes (ProACS). This Portuguese registry includes 25 cardiology departments and has received the approval and authorization from the National Committee of Data Protection (authorization number 3140/2010) and is registered at ClinicalTrials.gov with identification number NCT 01642329. We used the third universal definition of STEMI as a new ST‑segment elevation at the J point ≥ 0.1 mV in two contiguous leads or new left bundle branch block, for over 30 minutes, in a clinical setting consistent with acute myocardial ischemia. New-onset AF was defined as first occurrence of AF at the time of the myocardial infarction (MI) or any time after MI onset, in the absence of prior diagnosis. We divided the patients into 2 groups: Group 1 – Patients who did not develop AF during in-hospital stay for STEMI and Group 2 – Patients with new-onset AF during in-hospital stay for STEMI. We excluded patients with previous diagnosis of AF or previous anticoagulation therapy. In each patient, baseline clinical characteristics, including demographics and patient history (cardiovascular and non- cardiovascular comorbidities) were collected. Data relating to coronary angiography, percutaneous coronary intervention (namely, number of affected vessels and number of treated vessels) left ventricular function (assessed either by echocardiography, magnetic resonance, computed tomography, angiography or radionuclide imaging) and in-hospital and post-discharge medical therapy was also analyzed. The outcome variables studied were in‑hospital mortality and complications, namely: heart failure, cardiogenic shock, stroke, major bleeding, atrioventricular (AV) block, ventricular tachycardia, cardiac arrest, mechanical complications of AMI and need for invasive mechanical ventilation, Swan-Ganz catheter, transvenous cardiac pacing, intra-aortic balloon pump or ventricular assist device. We compared the defined outcomes in both groups and performed multivariate data analysis to assess independent predictors for new-onset AF and the impact of new-onset AF on in-hospital mortality. The study protocol is in accordance with the Declaration of Helsinki. Data analysis Categorical variables were characterized by absolute and relative frequencies, and numerical variables by means and standard deviations for symmetric distributions; for asymmetric distributions, medians and interquartile intervals were used. Normality was assessed by the Kolmogorov-Smirnov test. Comparisons between both groups regarding categorical variables were conducted using the chi-square Test or Fisher’s exact Test. For the continuous variables, unpaired t-tests were used to compare the means whenever possible, otherwise, the Mann-Whitney U test was used to compare the medians. Predictors were determined by adjusting the logistic regression model. Variables were selected to be included in the model using the stepwise (forward) method, together with the likelihood-ratio test. For each variable included in the regression model, adjusted odds ratio and 95% confidence interval (CI95%) were also estimated. The quality of the adjustment of the models was assessed by determining the area under the Receiver Operating Characteristic curve (AUC) and its sensitivity and specificity. A Kaplan-Meier estimate was obtained for time to death. Comparison of two survival functions was conducted by log-rank test. Statistical analyses were conducted using SPSS 19.0 ® at a 5% significance level for hypothesis-testing. Results A total of 6957 patients with primary diagnosis of ST‑segment elevation myocardial infarction were identified. We excluded 632 patients due to previous diagnosis of AF, previous anticoagulation therapy or missing information. A total of 6325 patients were enrolled (Figure 1). New-onset AF was found in 365 patients (5.8%). Overall baseline characteristics and of both groups are summarized in Table 1. Regarding patient demographics and comorbidities, patients who developed new-onset AF were older, with higher prevalence of female sex, higher prevalence of hypertension, diabetes mellitus, prior coronary artery bypass grafting (CABG), valvular heart disease, prior heart failure (HF), prior stroke, peripheral arterial disease, chronic obstructive pulmonary disease (COPD) and dementia. There was lower prevalence of smoking habits and family history of coronary disease in group 2. No difference between both groups was found regarding the other characteristics analyzed. Clinical data at admission is shown in Table 2. Patients in group 2 had higher heart rates and lower systolic blood pressure at admission. Patients in group 2 presented heart failure more frequently. Regarding therapy, reperfusion was successfully accomplished in both groups (Figure 2), with no significant difference. However, patients who developed AF had a longer time from symptom onset to reperfusion [median 243 (166-400) minutes vs. 267 (185-398) minutes, p = 0.033]. The number of patients who underwent coronary angiography or angioplasty was not statistically different. No difference in the number of affected vessels was found, although patients in group 2 had a higher prevalence of left main coronary artery disease (3.0% vs. 5.2%, p = 0.041), with no difference regarding other vessel disease. Patients in group 2 had implanted more bare-metal stents (25.1% vs. 35.4%, p = 0.003). Thrombectomy devices were more frequently used in patients in group 2 (32.5% vs. 42.9%, p < 0.001). Medical therapy during in-hospital stay and at discharge are shown in Tables 3, 4 and 5. Most patients developed new-onset AF on the first day [median 0 (0–1) days; mean 1.2 ± 3.5 days]. New-onset AF was associated with higher rate of in-hospital complications, namely: worse left ventricular function, higher prevalence of HF, cardiogenic shock, AV block, ventricular tachycardia, cardiac arrest, mechanical complications, stroke and major bleeding (Table 6). 949