ABC | Volume 111, Nº4, Octuber 2018

Original Article Rodrigues et al Predictors of late presentation in ST-elevation myocardial infarction Arq Bras Cardiol. 2018; 111(4):587-593 The study was carried out in accordance with the Guidelines and Norms Regulating Research Involving Human Subjects and was approved by the Institution's Research Ethics Committee. Logistics All patients were interviewed at the time of admission and followed during hospital stay, with clinical, angiographic and laboratory data being collected through a standard questionnaire. The occurrence of cardiovascular events was evaluated by the investigators in up to 30 days after the index event. Definitions STEMI was defined as typical chest pain at rest associated with ST-segment elevation of at least 1 mm of two contiguous leads of the frontal plane or 2 mm in the horizontal plane, or typical pain at rest in patients with a new, or presumably new, left bundle-branch block. 11 Late presentation was defined as a time interval until hospital arrival of more than 6 hours after the onset of the first STEMI related symptom. Previous heart disease was defined as prior STEMI or previous Percutaneous Coronary Intervention (PCI) or myocardial revascularization surgery (CABG). Major cardiovascular events (MCVE) were defined as a combination of all-cause mortality, new STEMI or stroke. 11 New STEMI was defined as recurrent chest pain, elevation of biological markers after the initial natural curve decline, with ST-segment elevation or new Q waves, according to the universal definition of myocardial infarction. Stroke was defined as a new focal neurological deficit with sudden onset, of presumably cerebrovascular cause, irreversible (or resulting in death) within 24 hours and not caused by another readily identifiable cause. The stroke was classified as ischemic or hemorrhagic. 11 Patient treatment The patients were treated according to the institution’s routines, and the researchers did not interfere with any of the applied treatments. All patients with STEMI were referred to coronary angiography and primary PCI (PCIp) as reperfusion therapy, when appropriate, as recommended by the guidelines. 12 Our institution is a tertiary referral center in cardiology, and the Hemodynamics department operates 24 hours/day, 7 days a week, performing approximately 3,000 coronary angioplasties/year. The emergency department is open to patients who spontaneously seek the hospital, whereas patients who are transferred from other health institutions in the city, the metropolitan region and the countryside of the state are also accepted. In our study, the decisions regarding patient referral from the emergency service to the Hemodynamic laboratory and the percutaneous therapy were left to the attending physicians. Decisions related to the procedure, such as access route, administration of glycoprotein IIb/IIIa inhibitors, aspiration thrombectomy, direct stenting, post-dilatation, models and number of stents used, were made at the discretion of the operators. The medications used in the initial care followed an institutional routine: aspirin (300 mg), clopidogrel (300 to 600mg) and anticoagulant (heparin 70 to 100U/kg) administered at the emergency department immediately after admission. Statistical analysis Data were analyzed using the Statistical Package for Social Sciences (SPSS), version 22.0, and the level of significance of p < 0.05 was considered for all the tests. The Kolmogorov‑Smirnov test was used to evaluate data normality. Continuous variables were expressed as mean and standard deviation for those with normal distribution, or as median and 25-75 percentiles. Categorical variables were described as absolute (n) and relative (%) numbers. The baseline characteristics of patients with late presentation were compared to those who arrived within the first 6 hours using the t-test for independent samples and chi-square test, as appropriate. Univariate and multivariate analyses were performed using the multiple logistic regression method, with late presentation as the dependent variable, and the variables with a p value ≤ 0.20 in the univariate analysis being included in the multivariate analysis. TheWINPEPI program, version 11.43, was used to calculate the sample size, which was calculated as 1,076 patients considering a statistical power of 90%, significance level of 5%, proportion of late presentation of 40% and odds ratio of 1.5 for the female gender as a risk factor. 13 An addition of 10% was made to control possible losses and refusals, and the final sample size consisted of 1,200 patients. Results Between December 2009 and November 2014, 1,297 individuals met the eligibility criteria and were included in the study. For 302 patients (23%), the time of arrival at the hospital since the chest pain onset was > 6 hours, being considered as late presentation according to the criteria defined in the study protocol. Table 1 shows the baseline characteristics of the population, according to the presence or not of late presentation. The median time of presentation was 3.0 [1.4-5.5] hours, being significantly higher in those considered as late presentation (8.5 [7.0-11.9] hours vs. 2.2 [1.0-3.7] hours). There was no statistically significant difference in relation to the mean age in the two groups. On the other hand, patients with late presentation were more often women of Black ethnicity with low income and lower educational level, when compared to those who arrived within the time window of the first 6 hours from pain onset. The two groups were overall similar regarding the presence of risk factors for coronary artery disease (CAD), but the percentage of patients with DMwas significantly higher among those with late presentation. Regarding the comparisons between pre-hospitalization diagnoses, we observed that patients with late presentation less often had a prior diagnosis of CAD (STEMI or myocardial revascularization) and chronic renal failure, and the frequency of other comorbidities was not statistically different. Regarding the atherosclerotic disease burden, we did not observe statistically significant differences between the groups related to the time of clinical presentation. 588