On and Off: The Dilemma of Managing STEMI After Hours

It is well established that delays in door-to-balloon time for patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) are associated with increased mortality, even among patients treated within 90 minutes of admission.1–4 It is therefore imperative that this process be optimized and that patient subgroups in which delays might be anticipated are identified. One previously identified subgroup consists of STEMI patients presenting to a hospital outside of regular working hours. For this reason, Cubeddu et al sought to compare clinical outcomes in patients presenting to a tertiary referral PCI center with STEMI during working hours, as compared with non-regular working hours.5 Importantly, they distinguished patients transferred from other centers from patients directly admitted from the emergency department, arguing that the transfer patients were a heterogenous population with unpredictable door-to-balloon times that could not be controlled for by the tertiary referral center. Moreover, as the authors point out, STEMI transfers are more likely to occur during non-regular hours, potentially biasing the outcomes of the group of STEMI patients seen outside of regular working hours. Their results indicate that STEMI patients presenting in “off” hours had significantly higher rates of mortality and cardiogenic shock, and this correlated with longer door-to-balloon times in this group. When door-to-balloon times were further analyzed, it was found that the major driver was a delay in mobilization of the STEMI team. These differences were seen irrespective of whether patients were transferred from another institution or presented to the emergency department of the tertiary referral center. The authors conclude by suggesting that outcomes in patients presenting after hours might be improved by implementing an “in-house” STEMI team, therefore improving door-to-balloon times in this subset of patients. Although these findings are of important clinical relevance, they need to be interpreted with some caution. The relatively small numbers of patients in this single-center study may mask other important differences between groups. In particular, although not statistically significant, patients presenting during “off” hours had higher baseline troponin levels, suggesting longer ischemic times. It is conceivable that patients presenting in off-hours may be less aware of ischemic symptoms or less willing to come to the hospital, thereby presenting later and driving the observed clinical differences between groups. Moreover, the authors do not present data on periprocedural complications for either study group. Although it has been previously reported that STEMI patients presenting at night have similar outcomes compared with STEMI presenters during the day,6 it is still conceivable that patients intervened on after hours may have had more procedural complications due to operator fatigue (as the authors allude to) or the availability of fewer support staff in the catheterization laboratory. It may also be the case that there were post-PCI care differences between the study groups, which may have also contributed to adverse outcomes in STEMI patients presenting after hours. For example, it is unlikely that the same level of senior medical and nursing staff is available to STEMI patients presenting after hours compared with regular hours, potentially leading to failures in the diagnosis of adverse clinical events such as recurrent ischemia, cardiac failure or bleeding complications. Another potential “confounder” is the after-hours psychology of avoiding more complicated procedures such as placement of a percutaneous left ventricular assist device or even an intra-aortic balloon pump due to limited resources and other issues. Drug prescription errors or omissions might also be more common after hours. Thus, although the implementation of an in-house STEMI team is likely to be effective in reducing door-to-balloon times in patients presenting after hours, whether this alone reduces STEMI morbidity and mortality is debatable, particularly in view of other factors that may also adversely affect outcomes in this patient cohort, including a higher incidence of cardiogenic shock. Moreover, such an endeavor would be expensive, and it might be more cost-effective to invest in patient and physician education to improve early identification of ischemic symptoms and other similar strategies. It would also be useful to pinpoint exactly why the STEMI team “engagement time” was significantly longer after hours than during working hours. Was it simply due to the fact that the STEMI team had to travel to the hospital, or were there unforeseen delays in the emergency department such as availability of staff to transport patients safely from the emergency department to the catheterization laboratory? Detailed analysis of this process would be beneficial in determining where exactly delays are occurring and how they could be overcome. Implementation of a detailed audit program outlining these factors with feedback to both the emergency department and the interventional cardiology department would also be vital in streamlining this process.7,8 In fact, at our institution, without an in-house STEMI call team, we have been able to achieve > 98% door-to-balloon times of From the Division of Cardiovascular Medicine, Stanford University, Stanford, California. The authors report no conflicts of interest regarding the content herein. Address for correspondence: David P. Lee, MD, Division of Cardiovascular Medicine, Stanford University, 300 Pasteur Drive, Room H-2103, Stanford, CA 94305. E-mail: dplee@stanford.edu

1. Rathore SS, Curtis JP, Chen J, et al. Association of door-to-balloon time and mortality in patients admitted to hospital with ST-elevation myocardial infarction: National Cohort Study. BMJ 2009;338:b1807.

2. McNamara RL, Herrin J, Bradley EH, et al. Hospital improvement in time to reperfusion in patients with acute myocardial infarction, 1999 to 2002. J Am Coll Cardiol 2006;47:45–51.

3. McNamara RL, Herrin J, Wang Y, et al. Impact of delay in door-to-needle time on mortality in patients with ST-segment elevation myocardial infarction. Am J Cardiol 2007;100:1227–1232.

4. McNamara RL, Wang Y, Herrin J, et al. Effect of door-to-balloon time on mortality in patients with ST-segment elevation myocardial infarction. J Am Coll Cardiol 2006;47:2180–2186.

5. Cubeddu RJ, Cruz-Gonzalez I, Kiernan TJ, et al. ST-elevation myocardial infarction mortality in a major academic center “on” versus “off” hours. J Invasive Cardiol 2009;21:518–523.

6. Uyarel H, Ergelen M, Akkaya E, et al. Impact of day versus night as intervention time on the outcomes of primary angioplasty for acute myocardial infarction. Catheter Cardiovasc Interv 2009.

7. Lai CL, Fan CM, Liao PC, et al. Impact of an audit program and other factors on door-to-balloon times in acute ST-elevation myocardial infarction patients destined for primary coronary intervention. Acad Emerg Med 2009;16:333–342.

8. Ward MR, Lo ST, Herity NA, et al. Effect of audit on door-to-inflation times in primary angioplasty/stenting for acute myocardial infarction. Am J Cardiol 2001:87: 336–338.