On-Hours vs Off-Hours: Presentation to ER with Acute Myocardial Infarction – Lower Survival Rate if Off-Hours
Reporter: Aviva Lev-Ari, PhD, RN
- Lauren Lapointe-Shaw, fellow,
- Chaim M Bell, associate professor
Author Affiliations
Never a good time, but some times are better than others
Acute myocardial infarction has high mortality, but early medical and surgical intervention can be lifesaving.1 2 3 4 5 6 Previous studies have shown that the time of day or day of the week when patients seek care can affect outcomes.5 7 8In most of these studies, patients presenting to hospital with an acute myocardial infarction during off-hours (evenings and weekends) wait longer for interventional treatments than those presenting during regular office hours and have a higher mortality. In a linked paper (doi:10.1136/bmj.f7393), Sorita and colleagues report the first systematic review of the effect of off-hour presentation on outcomes after acute myocardial infarction.9
The authors evaluated the literature on acute myocardial infarction and off-hour care. Outcomes included in-hospital and 30 day mortality, as well as door to balloon time for the subset of patients with ST elevation myocardial infarction. Using a random effects model, they reported pooled odds ratios for each outcome measure. The pooled results confirmed the presence of a 5% relative increase in mortality (both in-hospital and 30 day) as well as a delay of nearly 15 minutes in door to balloon time for patients presenting during off-hours. Meta-regression based on year of data showed an increase in the risk posed by off-hours care over time.
This novel systematic review advances knowledge on quality of care for patients with myocardial infarction, although it is limited by the studies it contains. In the absence of randomization, differences in patient characteristics between compared groups can introduce substantial bias into study results. Because patients cannot be randomized to present during or outside working hours, a common method of adjusting for baseline risk is needed to facilitate meaningful comparison between studies. If the included studies use different methods to control bias, heterogeneity is increased, which limits the conclusions that can be drawn from pooled analyses.10These are important considerations when undertaking any systematic review of observational studies.
The authors were further challenged by clinical and statistical heterogeneity. The definition of the off-hour time period differed across studies, and varying geographical settings are likely to lead to differences in case mix, time to presentation, physician practices, and hospital characteristics. Such heterogeneity makes it difficult to pool study results and generate a single measure of relative risk. Publication bias, as demonstrated by the absence of small negative studies in the funnel plot, may complicate interpretation still further, although, as the authors point out, there was no significant change in the pooled effect of off-hours presentation after accounting for the missing studies.
Confounding is always a problem in syntheses of observational studies. In Sorita and colleagues analysis it is particularly important to consider whether patients presenting out of hours are systematically different from other patients in such a way that increases their risk of death. They might be sicker, for example, or they may delay calling for medical help for longer. If the last case were true, then delayed presentation would lead to delayed treatment and potentially worse outcomes, which would have little to do with the quality of off-hour care. As the authors point out, the results as to whether time to presentation (delay before reaching hospital) differs significantly between patients presenting during off-hours and working hours are conflicting. If delay in presentation differs between groups, this could bias the measured relative mortality associated with off-hour care.
Although differences in underlying patient characteristics, including time to presentation, can significantly affect mortality, it is less clear how they would affect door to balloon time. Prolongation of door to balloon time is arguably a more robust measure of altered care during off-hours, because it is more likely to be directly controlled by the hospital and care providers. In this case, a process measure (door to balloon time) truly enhances the interpretation of an outcome measure (mortality), albeit for a subgroup of patients. The nearly 15 minute delay in percutaneous coronary intervention experienced by patients presenting with ST elevation myocardial infarction during off-hours provides a potentially causal link between the quality of off-hour care and patient outcomes.
Patients presenting during off-hours experience delays in urgent care and worse outcomes, and the gap seems to be increasing over time. As healthcare managers in many countries move toward performance based remuneration, patient outcomes are increasingly being used to gauge the quality of hospital care. Managers seeking to boost their hospital’s performance for patients with acute myocardial infarction should focus on improving their off-hour care, with the goal of providing consistently high quality care 24 hours a day and seven days a week.
Studies of quality of care and patient outcomes highlight the challenges we face when trying to measure true hospital performance. Administrative data often do not capture all the factors that contribute to baseline patient risk. To properly evaluate the quality of healthcare delivered at all times, we must refine our methods of risk adjustment to include time to presentation and severity of illness. Future studies should try to identify specific deficits in the care pathway during off-hours, allowing differences in outcomes to be linked to differences in processes. We look forward to reading about innovative strategies to deal with this problem. Patients deserve the best possible outcome, at any given time, and on any given day.
Notes
Cite this as: BMJ 2014;348:f7696
- Atsushi Sorita, senior fellow in preventive medicine and public health1,
- Adil Ahmed, senior research fellow2,
- Stephanie R Starr, consultant physician3,
- Kristine M Thompson, consultant physician4,
- Darcy A Reed, consultant physician5,
- Larry Prokop, reference librarian6,
- Nilay D Shah, senior associate consultant7,
- M Hassan Murad, consultant physician1,
- Henry H Ting, consultant physician8
Author Affiliations
- Correspondence to: H H Ting Ting.Henry@mayo.edu
- Accepted 28 November 2013
Abstract
Objective To assess the association between off-hour (weekends and nights) presentation, door to balloon times, and mortality in patients with acute myocardial infarction.
Data sources Medline in-process and other non-indexed citations, Medline, Embase, Cochrane Database of Systematic Reviews, and Scopus through April 2013.
Study selection Any study that evaluated the association between time of presentation to a healthcare facility and mortality or door to balloon times among patients with acute myocardial infarction was included.
Data extraction Studies’ characteristics and outcomes data were extracted. Quality of studies was assessed with the Newcastle-Ottawa scale. A random effect meta-analysis model was applied. Heterogeneity was assessed using the Q statistic and I2.
Results 48 studies with fair quality, enrolling 1 896 859 patients, were included in the meta-analysis. 36 studies reported mortality outcomes for 1 892 424 patients with acute myocardial infarction, and 30 studies reported door to balloon times for 70 534 patients with ST elevation myocardial infarction (STEMI). Off-hour presentation for patients with acute myocardial infarction was associated with higher short term mortality (odds ratio 1.06, 95% confidence interval 1.04 to 1.09). Patients with STEMI presenting during off-hours were less likely to receive percutaneous coronary intervention within 90 minutes (odds ratio 0.40, 0.35 to 0.45) and had longer door to balloon time by 14.8 (95% confidence interval 10.7 to 19.0) minutes. A diagnosis of STEMI and countries outside North America were associated with larger increase in mortality during off-hours. Differences in mortality between off-hours and regular hours have increased in recent years. Analyses were associated with statistical heterogeneity.
Conclusion This systematic review suggests that patients with acute myocardial infarction presenting during off-hours have higher mortality, and patients with STEMI have longer door to balloon times. Clinical performance measures may need to account for differences arising from time of presentation to a healthcare facility.
Conclusions and policy implications
In conclusion, this meta-analysis suggests that mortality is higher for patients with acute myocardial infarction who present during off-hours compared with regular hours. This finding may be partially attributed to longer door to balloon times during off-hours for patients with ST elevation myocardial infarction. Future studies should explore the variation in the quality of care by time of day, such as number of staff, expertise of staff, and other structural and process attributes in systems of care during off-hours. Performance measures used for value based purchasing, such as the 30 day risk standardized mortality rate, may need to account for differences by time of presentation to a healthcare facility to assess the quality of care.76 Efforts to improve systems of care should ensure that comparable outcomes are achieved for patients regardless of the time of day or day of the week that patients present to the healthcare system.
What is already known on this topic
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Past studies suggest that patients with acute myocardial infarction may or may not have higher mortality when they present to hospital during off-hours (weekends and nights) compared with regular hours
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No systematic reviews or meta-analyses of this topic have been done
What this study adds
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Patients with acute myocardial infarction presenting during off-hours have higher mortality, and those with ST elevation myocardial infarction have longer door to balloon times
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Efforts to improve systems of care should ensure comparable outcomes for patients regardless of time of presentation to hospital
Introduction
Acute myocardial infarction remains a leading cause of death worldwide.1 Every year, approximately one million people in the United States have an acute myocardial infarction and 400 000 die from coronary heart disease.2 Previous studies have suggested that patients with acute myocardial infarction who present to the hospital during off-hours (weekends and nights) may have higher mortality.3 45 6 Higher mortality during off-hours may be attributed to a lower likelihood of receiving evidence based treatment or timely reperfusion therapies.6 7Furthermore, the number of hospital staff and their level of expertise may contribute to gaps in the quality of care during off-hours.4 8 9 Because of the high incidence and case fatality of acute myocardial infarction, small increases in the relative risk of mortality during off-hours can translate to important effects in the population.
Using data from the National Registry of Myocardial Infarction database, Magid et al showed that patients with ST elevation myocardial infarction (STEMI) who presented during off-hours had higher in-hospital mortality and longer door to balloon times.6Kostis et al examined an administrative database in New Jersey and found that weekend admissions for patients with acute myocardial infarction were associated with higher in-hospital, 30 day, and one year mortality.4 Conversely, Jneid et al reported no significant difference in mortality between off-hours and regular hours for acute myocardial infarction patients in the Get With the Guidelines-Coronary Artery Disease (GWTG-CAD) national database, despite longer door to balloon times in off-hours for patients with STEMI.10 Other studies have also reported inconsistent results.11 12 13 14 15 16
To date, no systematic reviews or meta-analyses of this literature have been done. Therefore, we aimed to synthesize the available evidence on the effects of off-hour presentation of patients on outcomes of acute myocardial infarction. Our primary outcome was the difference in-hospital or 30 day mortality for patients with acute myocardial infarction who presented during off-hours compared with those who presented during regular hours. The secondary outcome was door to balloon time for patients with STEMI.
Outcome definition and subgroup analyses
Mortality outcomes
We used in-hospital or 30 day mortality as the main outcome. For studies without in-hospital mortality results, we used 30 day mortality when available. We did the main analysis for all studies combined. We also separately analyzed each mortality outcome (in-hospital versus 30 day). For the main outcome, we did subgroup analyses by diagnosis of patient cohort (STEMI versus non-STEMI), type of off-hours (weekend and night versus weekend versus night), measured time of presentation (arrival versus admission versus start of percutaneous coronary intervention), data source (clinical registry versus administrative data), region (North America versus Europe versus others), and outcome adjustment (adjusted versus unadjusted). To evaluate the possibility of a time trend effect of mortality across studies, we did meta-regression using the mid-year of enrollment of the cohort as the independent variable and the natural log of the effect size as the dependent variable. Owing to concern about potential overlapping patient sets, we did sensitivity analyses by excluding each single cohort and by including only one cohort from each study. We also did sensitivity analyses by excluding studies that expressed results as a hazard ratio.
Door to balloon time
We analyzed the proportion of patients with STEMI whose door to balloon time was less than 90 minutes and the mean or median door to balloon times. For mean or median door to balloon times, we did subgroup analyses by type of off-hours determination, measured time of presentation, and region, as well as meta-regression using the mid-year of enrollment of the cohort to evaluate time trends in door to balloon times. We also did sensitivity analyses limiting to studies that included only patients who were directly admitted to the hospital and excluding interventional studies.
Discussion
This systematic review and meta-analysis shows that patients with acute myocardial infarction who presented during off-hours had higher mortality than did those who presented during regular hours. Higher mortality during off-hours was seen for both in-hospital and 30 day mortality. The difference in mortality may be larger for patients with a diagnosis of STEMI and for a non-North American location of the study and may have worsened in recent years.
Comparison with other studies
This review showed that patients with STEMI were less likely to receive percutaneous coronary intervention within 90 minutes and had longer door to balloon times during off-hours. An approximate 30 minute delay in door to balloon time is associated with a 20-30% relative increase in in-hospital morality for STEMI patients, regardless of the baseline door to balloon time up to 180 minutes.62 63Therefore, the 15 minute increase in door to balloon time observed during off-hours could increase mortality by as much as 10-15%, assuming linearity between door to balloon time and mortality. This is consistent with our point estimate of 12% increase in odds of mortality for STEMI, which suggests that the mortality increase in off-hours may well be partially explained by prolonged door to balloon times. Magid et al reported that the difference in mortality became non-significant when adjusted for reperfusion treatment time.6 Additionally, a lower rate of urgent percutaneous coronary intervention for STEMI patients may also partially explain higher mortality during off-hours.4 64
Difference in door to balloon times and rate of percutaneous coronary intervention is likely associated with availability of cardiologists, support staff for the cardiac catheterization laboratory, or both. An around the clock on-site cardiology service is not uniformly available. During off-hours, many institutions need to assemble on-call staff and cardiologists to activate the cardiac catheterization laboratory. This is well illustrated in Magid’s study,6 in which the increase in the time interval from obtaining an electrocardiogram to arriving at the catheterization laboratory explained nearly all of the increases in door to balloon time during off-hours.
Other potential attributes to the increase in mortality during off-hours are availability of skilled staff in the cardiac care unit, availability of diagnostic tests, number of physicians or nursing staff, and human factors such as sleep deprivation and fatigue.65 66 67 68 A recent study found that patients with acute myocardial infarction in regions with a low density of cardiologists had higher 30 day mortality than did patients in regions with a high density, suggesting that the availability of cardiologists in the regional system of care may affect the outcomes of patients with acute myocardial infarction.69 Holmes et al reported that a successful regional care model can reduce the disparity of care between off-hours and regular hours for patients with STEMI.27 Therefore, establishing a local healthcare delivery system to provide consistent quality of care during weekends and nights may be the key to closing the mortality gap between off-hours and regular hours.
An alternative explanation for the increase in mortality during off-hours may be that the case mix differs between off-hours and regular hours. Some studies included in the meta-analysis show that patients who present during off-hours tend to be sicker when measured by the presence of cardiogenic shock or Killip class,6 36 44whereas others suggest no difference.12 15 41 52 53 61 In studies that measured time from onset of symptoms to presentation at hospital, the pre-hospital delay during off-hours was shorter,30 36 54 longer,5 or not different,12 16 3133 35 37 44 48 53 57 compared with regular hours. In fact, past studies showed that the pre-hospital delay was shorter during off-hours in both STEMI and non-STEMI patients.70 71 Furthermore, in studies in which mortality outcomes were adjusted (see table 1⇑ for adjusted variables), the off-hours increase in mortality remained significant (table 2⇑). Although residual confounding resulting from the difference in case mix cannot be excluded, these results suggest that increased mortality during off-hours is associated with factors that arise after presentation at hospital.
In meta-regression, we noted a significantly higher difference in mortality between off-hours and regular hours in the most recent years. We postulate that this may be due to the increase in shift work or hand-offs for off-hour coverage or to disproportionate improvement in the application of evidence based treatment during regular hours compared with off-hours; however, this could be also a chance finding and is certainly subject to ecological bias. In contrast, the difference in door to balloon time between off-hour and regular hour presentation did not significantly change over time. This discrepancy between trends in mortality and door to balloon time may be due to high heterogeneity or may suggest that factors other than door to balloon times contribute to the difference in mortality between off-hours and regular hours. These results should be viewed against secular trends showing decreases in both the absolute mortality rate and door to balloon times,72 73 and thus call attention to the opportunity to improve quality of care provided during off-hours.
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