IJCS | Volume 31, Nº5, September / October 2018

517 Table 5 - Comparison of in-hospital outcomes between the Nighttime and Daytime Groups after the primary percutaneous coronary intervention Outcome Nighttime group n (%) Daytime group n (%) p value Combined MACE* 24 (15.1) 41 (14.3) 0.58 Death 15 (9.4) 23 (8.0) 0.61 New non-fatal AMI † 9 (5.6) 19 (6.6) 0.15 Statistical tests used: Pearson's chi-square test. * Death from all- cause in the in-hospital phase, new non-fatal AMI or CVA during hospitalization. MACE: major adverse cardiovascular events; AMI: acute myocardial infarction. Barbosa et al. Primary PCI at night time Int J Cardiovasc Sci. 2018;31(5)513-519 Original Article system is of utmost importance for health strategy policies, since about 50% of STEMI cases occur outside regular business hours. 18 Studies consistently suggest that PPCI may have different results, according not only to the total time of myocardial ischemia, 17,19,20 but also the time when it is performed. 21-26 Nighttime or weekends may show a PPCI procedure failure rate up to 81% higher, 21 a door- to-balloon time up to 21.3 minutes longer, 24 time from the electrocardiogram to arrival in the Hemodynamics unit 20.7 minutes longer 24 andmortality in 30 days up to 121% higher, 21 when compared to the business hours. In our study, the only statistically significant difference between the Nighttime and Daytime Groups was the rate of glycoprotein IIb/IIIa inhibitor use. The main hypothesis for this finding is the greater anxiety by the operator to optimize the anterograde coronary flow and to resolve the finding of intracoronary thrombi at nighttime. A Brazilian study showed that the delay associated with nocturnal PPCI was 18 minutes (102 ± 98 minutes vs. 84 ± 66 minutes, p < 0.01). The in-hospital mortality rate was 10.2% vs. 7.6%, and the one-year mortality rate was 12.6% vs. 9.5% (PPCI at nighttime vs. daytime), both showing no statistical significance. 25 The differences in results between the Nighttime and Daytime Groups in comparison to the data in our study can be explained by the presence of a regular on-duty interventionist cardiologist in our service, not one on-call regimen. We demonstrated that the strategy of having an on- duty Interventional Cardiology team at nighttime can shorten the delay in STEMI treatment at these times. Although this point is only one of the necessary care links, there is an increase in the possibility of performing PPCI in a timelymanner, being able to reach the recommended goals even at non-business hours and to avoid an increase in mortality. In a study by Nguyen et al., 27 the use of the 24-hour on-duty presence of the interventionist cardiologist led to a reduction of 57% in the door-to- balloon time, with a mean absolute reduction of 71 minutes, and a 54% reduction in hospital length of stay. The mean door-to-balloon time over 90 minutes observed in the present study was probably due to avoidable in-hospital delays and to the immaturity of the care system at the time, which still relied on the wait for non-medical staff who were on-call due to contractual issues. Also, the result reflects the practical difficulty of reaching the time goals recommended for STEMI treatment in our country. However, the nighttime schedule did not interfere in the total delay, demonstrating the feasibility of attaining adequate reperfusion times, aiming to improve the quality of care, with no harm to the patient as a result of the time of day when the event occurs. Limitations Although the present study is relevant, some limitations should be mentioned. The single-center characteristic limits the extrapolation of results to other populations. Clinical follow-up restricted to the in- hospital period, despite having the power to demonstrate differences between the two groups, underestimates the real impact of the time when the PPCI was performed on the results, by not evaluating outcomes in the medium or long term. Potentially relevant data, such as kidney dysfunction and hemorrhagic complications during the in-hospital evolution were not collected and evaluated in this study. The times used to divide the groups do not always accurately represent the business and non- business hours, whichwere the object of our study due to the potential difference regarding the speed and quality of medical care. As the study included only patients actually submitted to PPCI in a timely manner, some patients that were not transferred or were not diagnosed with STEMI were not analyzed, restricting the results to outcomes after the PPCI, and not all patients with STEMI. Conclusion The results of the primary percutaneous coronary interventions performed in the nighttime and daytime