ABSTRACT: Background. A higher mortality rate for weekend myocardial infarction (MI) admissions has been reported and attributed to the lower availability of primary percutaneous coronary intervention (PCI) during off-hours. However, the data are conflicting and, furthermore, inapplicable to hospitals where primary PCI is invariably performed. Methods. This study was conducted in a tertiary hospital where primary PCI is routinely performed in all patients with ST-elevation myocardial infarction (STEMI). Patients admitted during on-hours (Monday through Friday 7 am–7 pm) where compared to off-hours patients (including weekends). The primary endpoint of in-hospital mortality, cardiogenic shock and recurrent MI was examined. A second analysis that excluded STEMI transfers, in-hospital mortality and reperfusion times was examined. Results. Between 2003 and 2007, 747 STEMI patients (46% on-hours vs. 56% off-hours) underwent primary PCI. Demographic characteristics were similar between on- and off-hours groups. However, off-hours STEMI admissions had significantly greater in-hospital mortality rates (8% vs. 3.7%; p = 0.01) and higher rates of cardiogenic shock (37% vs. 24%; p = 0.0001). Admission arrival time was an independent predictor of in-hospital mortality (hazard ratio [HR] 3.98, 95% confidence interval [CI] 1.10–14.38; p = 0.035). Longer door-to-balloon times (DTB) were observed during off-hours (134 vs. 109 minutes; p Methods
Study population. A total of 747 consecutive patients admitted to Massachusetts General Hospital (MGH) between January 1, 2003 and March 31, 2007 with a diagnosis of acute STEMI for primary PCI were included in the study. Patients were classified according to their hospital admission arrival time. “On-hours” included all patients admitted between Monday and Friday from 7 am to 7 pm. Patients admitted outside the scope of this time frame were classified as “off-hours” (including weekends). Time allocations were not established arbitrarily, but rather according to the practice performance pattern of the cardiac catheterization laboratory.
At our hospital, less than 2% of the patients admitted with acute STEMI undergo something other than primary PCI. These patients were not included in the analysis. The use of adjunctive antiplatelet and anticoagulant therapy before, during and after PCI was left to the discretion of the operator. The study was approved by our institutional review board.
Study endpoints. The primary endpoint of the study was all-cause in-hospital mortality, cardiogenic shock and recurrent MI. Secondary endpoints included procedural success and hospital length of stay. All study endpoints were analyzed and compared with respect to acute STEMI admissions during on-hours versus off-hours.
Definitions. STEMI was defined as the presence of at least one of the following electrocardiographic changes: 1) ST-segment elevation: new or presumed new ST-segment elevation at the J-point in ≥ 2 contiguous leads, with the cut-off points ≥ 0.2 mV in leads V1, V2 or V3, or ≥ 0.1 mV in other leads; or 2) the presence of new left bundle branch block. Cardiogenic shock was defined as a clinical state of hypotension or hypoperfusion requiring intravenous inotropic therapy or the use of an intra-aortic balloon pump (IABP) at any time during the patient’s hospitalization. Procedural success was defined as the achievement of a diameter stenosis of Results
First analysis. Study population. From the total study population of 747 patients, we identified 325 (44%) admitted during on-hours and 422 (56%) during off-hours. Both patient groups had similar baseline demographic characteristics (Table 1).
STEMI, angiography and procedural characteristics for both groups are summarized for comparison in Table 2. The time of symptom onset to first medical contact did not differ between on- and off-hours (p = 0.23). Baseline and peak troponin I levels were similar, and there were no differences in the use of adjunctive pharmacotherapy. The right coronary artery was more frequently the culprit vessel in both groups, followed by the left anterior descending artery and the left circumflex coronary artery. We observed no difference in preprocedural TIMI grade scores between on- and off-hour admissions. Coronary stenting was performed in the majority of cases, with drug-eluting stents used more frequently than bare-metal stents. The use of intra-coronary thrombectomy devices, number of stents and lesions treated did not differ between groups.
Major outcomes. Patients admitted during off-hours had significantly higher mortality rates than on-hour patients (34/325 [8%] vs. 12/422 [3.7%], respectively; p = 0.01), and were more likely to develop cardiogenic shock (78/325 [24%] vs. 156/422 [37%]; p = 0.0001). No difference in recurrent in-hospital MI was observed (on-hours 5/325 [1.4%] vs. off-hours 7/422 [1.6%]; p = 0.89). The adjusted multivariate analysis identified admission arrival time as an independent predictor of in-hospital mortality (hazard ratio [H]R 3.98; 95% confidence interval [CI] 1.10–14.38; p = 0.035).
The secondary endpoint of procedural success was high, and no difference between the groups (93% on-hours vs. 91% off-hours; p = 0.55) was seen. Similarly, the median length of hospital stay did not differ between on- and off-hours (p = 0.94), and was approximately 4 days (interquartile range: 3–7).
Second analysis. Study population. Direct ED admissions comprised 42% (315/747) of the total population. Patients admitted during on-hours (n = 159) had similar baseline characteristics compared with those admitted during off-hours (n = 156). (Table 3) The mean time-to-symptom onset was Discussion
This study demonstrates that STEMI patients admitted to a tertiary hospital for gold-standard primary PCI still have a significantly increased risk of in-hospital death during off-hours when compared to on-hour patients. Similar findings were observed even after exclusion of the transfer subset population.
The shortfall of the medical-care system during non-regular working hours has been increasingly appreciated.3–5,8,9 Although several similar studies have been published on this topic, the data on patients with acute MI are controversial and derive primarily from a large, uncontrolled database involving: 1) multiple centers with different levels of care,2,6,8,10 inaccurate time variables (i.e., weekend vs. weekday, as opposed to on- vs. off-hours),3,6,8 both STEMI and non-STEMI,4,6,10variable treatment protocols (medical, interventional or both),5,6,11 all-comers (i.e., transfers and non-transfers).6,8,10
The results of this study are therefore important, and represent the first to distinctively evaluate the impact of admission arrival time in a specific cohort of STEMI patients treated with gold-standard primary PCI during on- and off-hours. Contrary to the results of Jneid et al,10 MI off-hour admissions were associated with a four-fold increased risk of in-hospital death. Furthermore, although the results are concordant with those of Kotis et al,6 our study suggests that the increased mortality observed during non-regular working hours (off-hours) does not solely relate to the provision of catheterization laboratory services, but rather the increased timing of primary PCI delivery during off-hours.
Up to 98% of STEMI patients admitted to our facility undergo primary PCI, regardless of the day and time of the week. Nevertheless, and despite similarities in patient baseline demographic, clinical and procedural characteristics, the in-hospital mortality rate was still remarkably greater during off-hours (8% vs. 3.7%). Admission arrival time proved to be an identified predictor of in-hospital mortality.
Although STEMI off-hour admissions were associated with an average time delay in DTB of close to 30 minutes (on-hours 109 minutes vs. off-hours 134 minutes; p Conclusions
In the specific and previously unknown cohort population of acute STEMI patients treated with gold-standard primary PCI, off-hour admissions are associated with increased mortality and cardiogenic shock. Delays in DTB times may partially explain our findings, even when achieved within the recommend 90 minutes. Strategies to optimize reperfusion time during off-hours need to be implemented14–16 including, perhaps, a 24/7 in-house “STEMI team.”
From the Massachusetts General Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts.
The authors report no conflicts of interest regarding the content herein.
Manuscript submitted March 25, 2009 and accepted May 27, 2009.
Address for correspondence: Igor F. Palacios, MD, Massachusetts General Hospital, Division of Cardiology, 55 Fruit Street, GRB 800, Boston, MA, 02114. E-mail: ipalacios@partners.org
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