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Off-Hours Presentation, Door-to-Balloon Time, and Clinical Outcomes in Patients Referred for Primary Percutaneous Coronary Intervention
Abstract
Objectives. Presentation with ST-segment-elevation myocardial infarction (STEMI) during off-hours may impact timely reperfusion and clinical outcomes. We investigated the association between off-hours presentation, door-to-balloon time, and in-hospital mortality in patients with STEMI referred for primary percutaneous coronary intervention (PCI). Methods.We included consecutive patients referred for primary PCI at the University of Ottawa Heart Institute between July 2004 and December 2017. The off-hours group included patients presenting on weekends, statutory holidays, or between 18:00 to 07:59 hours on weekdays. The on-hours group included patients presenting between 08:00 and 17:59 hours on weekdays. The primary clinical outcome was the adjusted in-hospital mortality. The primary quality-of-care indicator was door-to-balloon time. Results. A total of 5132 patients were included, with 3152 (61.4%) in the off-hours group and 1980 (38.6%) in the on-hours group. The median door-to-balloon time was longer in the off-hours group compared with the on-hours group (102 minutes vs 77 minutes; P<.001), while the median onset-to-door time was similar (P=.40). There was no difference in the rates of in-hospital mortality (3.5% vs 3.0%; P=.32) or in the adjusted mortality (odds ratio, 1.2; 95% confidence interval, 0.8-1.8; P=.44) between off-hours and on-hours groups. However, door-to-balloon time was an independent predictor of in-hospital mortality (P<.01) and off-hours presentation was an independent predictor of longer door-to-balloon time (P<.001), with an excess of 22.1 minutes. Conclusion. Patients treated with primary PCI during off-hours had longer door-to-balloon times. Treatment during off-hours was an independent predictor of longer door-to-balloon time and longer door-to-balloon times were associated with higher mortality.
J INVASIVE CARDIOL 2023;35(4):E185-E193. Epub 2023 February 24.
Key words: door-to-balloon time, mortality, myocardial infarction, off-hours, percutaneous coronary intervention
In patients presenting with ST-segment-elevation myocardial infarction (STEMI), timely reperfusion is critical. Several studies have documented that delay in time to reperfusion is associated with increased mortality in patients with STEMI who are referred for primary percutaneous coronary intervention (PCI).1-3 Current guidelines for primary PCI recommend first medical contact-to-balloon time of 120 minutes or less.4,5 While first medical contact-to-balloon time has been adopted as the metric for a STEMI system, hospital door-to-balloon time is widely used as an indicator of quality-of-care at the institutional level.6
The last 2 decades has witnessed the development of regional STEMI systems promoting primary PCI as the dominant reperfusion strategy over fibrinolytic therapy. Two key factors played a critical role in driving this change. First, primary PCI was demonstrated to improve clinical outcomes over fibrinolytic therapy and, second, the efficacy of primary PCI was found to be time dependent.7,8 However, given the unpredictable onset of a STEMI, patients can present to the hospital during “off-hours” (ie, outside of working hours during nights, weekends, and holidays). Contemporary data evaluating the clinical impact of the availability of the PCI team at the time of the patient’s hospital presentation are scarce and conflicting.9-15
A recent study evaluated the impact of off-hours presentation on mortality in patients treated with primary PCI, within the context of an organized STEMI network, and suggested that mortality was driven mostly by differences in the patient characteristics rather than the time of hospital presentation.16 However, an evaluation of the impact of critical time intervals in relation to time of presentation at the hospital has not been fully elucidated. Accordingly, we performed this study to further investigate the association between off-hours presentation, door-to-balloon time, and in-hospital mortality in patients referred for primary PCI within the context of a large contemporary STEMI system with consecutive patients.
Methods
Study population. We identified consecutive patients with STEMI referred for primary PCI between July 2004 and December 2017 to the University of Ottawa Heart Institute. This quaternary care center provides cardiac care to a region of more than 1.2 million people and features a highly standardized regional STEMI program.17,18 The center receives patients on a 24/7 basis for primary PCI from 2 sources within a 90-km radius: direct transfer from the prehospital setting by paramedics or via interhospital transfer from 9 surrounding community hospitals. During the study period, it was standard practice to refer immediately all patients presenting within this region for primary PCI. Patients from 5 hospitals outside the 90-km radius that routinely administered fibrinolytic therapy before transferring patients to the PCI center were excluded from the analysis.
Patients were included if they met the following criteria: (1) presented with chest discomfort within 24 hours of onset; (2) had ST-segment elevation of ≥0.2 mV in leads V1 to V3 or ≥0.1 mV in 2 or more contiguous leads, or left bundle-branch block not known to be old; and (3) were referred within the 90-km primary PCI radius. We excluded patients who developed a STEMI while in hospital, who presented with out-of-hospital cardiac arrest, who did not undergo PCI, or who had missing data on arrival time or balloon time.
During the study period, standard practice was to administer 162 mg chewable aspirin, 600 mg clopidogrel or 180 mg ticagrelor, and 60 U/kg (up to a maximum 4000 U) intravenous unfractionated heparin before cardiac catheterization.
Patients were stratified into 2 groups based on the time of presentation at the hospital. The on-hours group included patients presenting during regular weekday hours, defined as between 08:00 and 17:59 hours on weekdays, which is based on the in-house availability of the interventional team. The off-hours group included patients presenting on weekends, statutory holidays, or between 18:00 to 07:59 hours on weekdays.
Data collection and outcomes. The primary clinical outcome was defined as the adjusted in-hospital mortality and the primary quality-of-care indicator was defined as door-to-balloon time. Secondary outcomes included unadjusted mortality, stroke, reinfarction, bleeding, cardiogenic shock, and peak creatine kinase during the index admission.
Stroke was defined as the occurrence of new neurological deficits lasting for >24 hours with evidenced of ischemia or hemorrhage demonstrated by computed tomography or magnetic resonance imaging. Reinfarction was defined as the recurrence of cardiac ischemia symptoms occurring at rest and lasting for >30 minutes in combination with re-elevation of ST-segment on an electrocardiogram and of cardiac enzymes (twice the upper limit of normal) or angiographic evidence of reocclusion of the infarct-related artery. Bleeding is reported as major and minor according to the Thrombolysis in Myocardial Infarction (TIMI) classification.19Cardiogenic shock was defined as a systolic blood pressure of ≤80 mm Hg needing intravenous pressor support. Door time was defined as the time of the first hospital encounter and balloon time as time of the first balloon inflation or device usage. Coronary flow was reported as per TIMI classification.19
Critical time intervals were obtained using ambulance call reports, emergency department triage sheets, and time stamps on qualifying electrocardiograms, medical charts, and catheterization laboratory reports. Data were extracted from electronic medical records using dedicated case report forms.
Ethical approval. The study was approved by the Ottawa Health Science Network Research Ethics Board.
Statistical analysis. Categorical variables are described as proportions and compared using Chi-square test or Fisher’s exact test, as appropriate. All normally distributed continuous variables are described as mean ± standard deviation and compared using the Student’s t test. Time intervals are described as median and interquartile range (IQR) and compared using the Wilcoxon test.
We constructed 3 models to explore the association between off-hours presentation, door-to-balloon time, and in-hospital mortality. Covariates entered in the 3 models included baseline characteristics with a P<.15, as well as variables deemed to be clinically important and based on existing literature.20 In the first model, we explored the association between off-hours presentation and in-hospital mortality using a multivariable logistic regression analysis. Similarly, we constructed a second model to assess the association between door-to-balloon time and in-hospital mortality. The final model was designed to assess the association between door-to-balloon time and presentation during off-hours compared with on-hours. A linear regression analysis was conducted to identify independent factors associated with door-to-balloon time. Calculated estimates are depicted as odds ratio (OR) with 95% confidence interval (CI) for models 1 and 2 and as point estimate with 95% CI for model 3.
Two-sided P-values <.05 were considered significant. All statistical analyses were done using SAS, version 9.4 (SAS Institute).
Results
Characteristics of the patients. Among 5923 consecutive patients referred for primary PCI between July 2004 and December 2017, a total of 5132 patients met study criteria, with 1980 (38.6%) in the on-hours group and 3152 (61.4%) in the off-hours group (Figure 1). We excluded 93 patients presenting with in-hospital STEMI, 188 with out of–hospital cardiac arrest, 384 in whom no PCI was performed, and 126 with missing time data for either arrival or balloon time.
The baseline characteristics are shown in Table 1. The mean age was 62.2 ± 13.0 years in the off-hours group and 63.1 ± 13.1 years in the on-hours group (P<.01). The prevalences of diabetes mellitus (19.9% vs 17.1%; P=.01) and current smoking (42.2% vs 38.7%; P=.02) were higher in the off-hours group. Patients in the off-hours group had higher rates of Killip class II or greater (P=.01) and a higher mean systolic blood pressure (P<.01). Compared with the on-hours group, patients in the off-hours group were less likely to have been transferred directly to the PCI center from the field (36.7% vs 41.0%, respectively; P<.01).
Procedural and angiographic characteristics. Procedural and angiographic results are presented in Table 2. The rates of stent insertion, balloon-alone, and coronary bypass surgery within 24 hours were similar between off-hours and on-hours groups, respectively. The use of bivalirudin was lower among patients presenting during off-hours (66.7% vs 69.4%; P=.046), but there was no difference in the use of glycoprotein IIb/IIIa inhibitors between the 2 groups. Multivessel disease was more prevalent among patients presenting during off-hours (58.8% vs 55.4%; P=.02), but there was no difference in the rates of left main disease (4.2% vs 3.6%; P=.30). Baseline TIMI grade 3 flow was observed in 20.9% of patients in the off-hours group compared with 18.6% of patients in the on-hours group (P<.01). Following the catheterization procedure, the rates of TIMI grade 3 flow were similar in the 2 groups (93.5% vs 94.2%; P=.25).
Critical time intervals. Critical time intervals are presented in Table 3. Median door-to-balloon time was longer in the off-hours group (102 minutes; IQR, 76-133) compared with the on-hours group (77 minutes; IQR, 43-115; P<.001). Cumulative door-to-balloon intervals are shown in Figure 2A. Door-to-balloon time was achieved within 60 minutes of hospital presentation in 10.6% of patients presenting off-hours and in 43.8% of patients presenting during on-hours; and within 120 minutes of hospital presentation, in 72.8% and 84.0%, respectively (P<.001). There was no difference in the median onset of symptoms to hospital arrival time between the 2 groups (98 minutes vs 94 minutes; P=.40). The cumulative symptom onset to hospital arrival times are depicted in Figure 2B.
In-hospital clinical outcomes. In-hospital clinical outcomes are presented in Table 4. There was no difference in the unadjusted rate of in-hospital mortality between the off-hours group and the on-hours group (3.5% vs 3.0%; P=.32). There was also no difference in the rates of stroke, reinfarction, and TIMI bleeding. However, there was a trend toward a higher rate of cardiogenic shock in the off-hours group (5.4% vs 4.2%; P=.06), and the mean peak creatine kinase was significantly higher in the off-hours group (1856 U/L vs 1668 U/L; P<.001).
Medications on discharge. Cardiac medications prescribed on discharge were similar between the off-hours and on-hours groups (Supplemental Table S1). Aspirin and an additional antiplatelet agent were prescribed to over 98% and 95% of patients, respectively. Beta-blockers and statins were prescribed to over 90% and 96% of patients, respectively.
Regression analyses. Table 5 shows the regression analyses for the 3 models. The results for Model 1 indicate no significant difference in the adjusted in-hospital mortality in the off-hours compared with the on-hours group (OR, 1.2; 95% CI, 0.8-1.8; P=.44). In Model 2, door-to-balloon time (per 10 minutes) was found to be an independent predictor of in-hospital mortality after adjusting for the same covariates (OR, 1.02; 95% CI, 1.01-1.04; P<.01). In Model 3, off-hours presentation was an independent predictor of longer door-to-balloon time, (P<.001), associated with an excess of 22.1 minutes. Supplemental Tables 2–4 demonstrate the results of each model and the covariates included in the models.
Discussion
Our study reports clinical outcomes in patients treated with primary PCI during regular hours and those treated during off-hours in a contemporary regional STEMI system using standardized protocols. More than 60% of the patients presented during off-hours. Although we found no difference in the adjusted in-hospital mortality between the 2 groups, patients treated during off-hours had significantly longer door-to-balloon times as compared with patients treated during regular hours, and longer door-to-balloon times were independently associated with increased mortality. These findings infer that delay to reperfusion during off-hours presentation could be associated with increased mortality.
As most patients with STEMI present outside of regular working hours, understanding the association between off-hours presentation and clinical outcomes is fundamental for resource allocation.9,10,16 Henriquez et al evaluated the circadian patterns of myocardial infarction in 1702 STEMI patients referred for primary PCI, and noted that as compared with hospital admission between 08:00 and 18:00 hours, admission between 18:00 and 08:00 hours was associated with a higher PCI failure rate and 30-day mortality.12 In our study, PCI success rate as defined by the achievement of postprocedure TIMI grade 3 flow was similar between the 2 groups. Similarly, using the National Registry of Myocardial Infarction database, Magid et al reported on 33,667 STEMI patients treated with primary PCI, and concluded that presentation during off-hours was associated with substantial delays for primary PCI but not for fibrinolytic therapy.13 In addition, patients presenting during off-hours had significantly higher adjusted in-hospital mortality compared with patients presenting during regular hours.13 However, the study was performed prior to the era of standardized STEMI systems and patients who initially presented to non-PCI-capable hospitals were excluded from the analysis.
In contrast to previous studies, our analysis included inter-hospital transfers as part of a regional STEMI system and was performed in the era of P2Y12 receptor antagonists and drug-eluting coronary stents. Our analysis did not demonstrate a difference in mortality between the off-hours and the on-hours groups. This could be due, at least partly, to the relatively low door-to-balloon times and high PCI success rates observed in our patient population treated within a standardized regional STEMI care system. This may have attenuated the difference in patient outcomes between the 2 groups.
Others who have developed STEMI systems have reported on this topic. Maier et al, using the Berlin Myocardial Infarction Registry, evaluated 2131 STEMI patients and reported a longer median door-to-balloon time for patients treated during off-hours (90 minutes vs 79 minutes, a difference of 11 minutes; P<.001) and higher in-hospital mortality. After adjustment, off-hour presentation remained an independent predictor for in-hospital mortality.14 Similarly, Casella et al evaluated 3072 STEMI patients treated with primary PCI within the STEMI Network of the Italian Region Emilia-Romagna and reported longer median door-to-balloon time for patients treated during off-hours (88 minutes vs 77 minutes, a difference of 11 minutes; P<.001); however; there was no difference in mortality.9
In the study by Latucca et al, a total of 2167 STEMI patients were evaluated who were referred for primary PCI.16 The median first medical contact-to-sheath insertion time did not differ between off-hours and on-hours admission (93 minutes vs 90 minutes; P=.58); given the minimal difference in these critical time intervals, it is not surprising that there was no difference in the in-hospital mortality. Of note, patients with out-of-hospital cardiac arrest were included, which likely contributed to a higher overall in-hospital mortality rate in this study. The inclusion of patients with out-of-hospital cardiac arrest may attenuate the impact of door-to balloon time as the extent of acute brain injury has a dominant effect on survival in such patients where time to return of spontaneous circulation is likely more clinically relevant.
Data in this area from clinical trials are rather scarce. Selvaraj et al conducted a subgroup analysis of the effect of time of presentation on clinical outcomes among a population of a large contemporary randomized clinical trial, CHAMPION PHOENIX (Clinical Trial Comparing Cangrelor to Clopidogrel Standard of Care Therapy in Subjects Who Require Percutaneous Coronary Intervention).21 They analyzed clinical outcomes among a subset of patients with STEMI according to time of presentation (n = 1992). They demonstrated no difference in the primary composite outcome of all-cause mortality, myocardial infarction, stent thrombosis, or ischemia-driven revascularization at 48 hours between the off-hours and on-hours groups (OR, 1.00; 95% CI, 0.57-1.74; P=.99).21 In this study, patients in the off-hours group had a shorter median time from symptom onset to PCI (5.00 hours vs 5.98 hours; P<.001) and a shorter median time from admission to PCI (76.8 minutes vs 79.8 minutes; P<.001).21 This supports the notion that achieving timely reperfusion remains to be the most important factor to achieve favorable clinical outcomes.
Confounding factors and data heterogeneity make the interpretation of these studies more difficult. For instance, the baseline characteristics of the study by Maier et al suggest a sicker population and the study did not include all referring hospitals.14 The definition of time intervals also differs between studies. There are also region-specific logistical issues such as distances traveled to the PCI center by emergency medical services and PCI staff, which may account for differences in door-to-balloon times and clinical outcomes. In the meta-analysis by Sorita et al, patients presenting during off-hours had longer door-to-balloon time by 14.8 minutes and a higher mortality, but there was a significant degree of heterogeneity among included studies.15
It has been suggested that further efforts to reduce door-to-balloon time may not reduce mortality and that additional factors need to be targeted to accomplish this goal.22 Our study re-examined the importance of door-to-balloon time and is unique for several reasons. It was designed to assess the associations between: (1) time of hospital presentation and in-hospital mortality; (2) door-to-balloon time and in-hospital mortality; and (3) off-hours vs on-hours and door-to-balloon time. Although we did not demonstrate a difference in mortality between presentation during off-hours compared with on-hours, we were able to reaffirm the independent correlation between door-to-balloon time and in-hospital mortality. Finally, we showed that off-hours presentation was an independent predictor of longer door-to-balloon times, a variable that was associated with increased mortality. These findings should prompt a balanced re-evaluation of individual STEMI systems to find ways to close the time gap between on-hours and off-hours.
Pilot studies have shown that creating a 24/7 in-house interventional team is feasible and reduces door-to-balloon time.23,24 However, this approach needs to be carefully balanced against the potential staff burnout and limited resources.25 In our study, door-to-balloon time was expected to be longer during off-hours because catheterization laboratory personnel are usually off-site. Our results apply to many other jurisdictions where the staff is off-site during off-hours. Our study was done in the context of a highly standardized STEMI system and a high-volume PCI center, which applied contemporary strategies with experienced and high-volume operators.
Study limitations. Our study has several limitations. First, it is a retrospective cohort study based on registry data and confounding variables may have impacted on the results. We attempted to control for covariates using multivariable analyses. Second, although our study has a relatively large sample size, under-powering could have prevented us from reaching statistical significance to establish directly that off-hours was associated with an increase in mortality. The sample size to detect a minimal clinical difference in mortality would need to be much larger as many patients in either group had overlapping door-to-balloon times. We addressed this issue by showing that longer door-to-balloon times were associated with off-hours presentation, and that longer door-to-balloon times correlated with excessive mortality. Finally, selection bias may account for differences in outcomes in settings where physicians choose fibrinolytic therapy over primary PCI during off-hours.26 However, this was not likely to be the case in our study, as all of the sending hospitals were dedicated primary PCI referral centers.
Conclusion
We found that patients who were treated with primary PCI for STEMI during off-hours had significantly longer door-to-balloon times as compared with patients treated during regular hours. Treatment during off-hours was an independent predictor of longer door-to-balloon time and longer door-to-balloon times were associated with higher mortality. Given that most STEMI patients present during off-hours, new strategies may be needed to reduce reperfusion times during off-hours presentation.
Affiliations and Disclosures
From the 1Adult Cardiology Training Program, Queen’s University, Kingston, Ontario, Canada; and 2University of Ottawa Heart Institute, Ottawa, Ontario, Canada
Funding: This study was supported by the University of Ottawa Heart Institute Regional STEMI Program.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript accepted January 18, 2023.
Address for correspondence: Dr Michel Le May, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada. Email: mlemay@ottawaheart.ca
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