The effects of prearrival direct notification call to interventional cardiologist on door-to-balloon time in patients who required secondary diversion with ST-elevation myocardial infarction for primary percutaneous coronary intervention

Abstract

Background:

Rapid door-to-balloon times in ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention are associated with favorable outcomes.

Objectives:

We evaluated the effects of prearrival direct notification calls to interventional cardiologists on door-to-balloon time for ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention.

Methods:

A 24-h hotline was created to allow prearrival direct notification calls to interventional cardiologists when transferring ST-elevation myocardial infarction patients. In an urban, tertiary referral center, patients who visited via inter-facility or the emergency department directly were included. Clinical parameters, time to reperfusion therapy, and in-hospital mortality were compared between patients with and without prearrival notifications.

Results:

Of 228 ST-elevation myocardial infarction patients, 95 (41.7%) were transferred with prearrival notifications. In these patients, door-to-balloon time was shorter (50.0 vs 60.0 min, p = 0.010) and the proportion of patients with door-to-balloon time < 90 min was higher (89.5% vs 75.9%, p = 0.034) than patients without notifications. These improvements were more pronounced during “off-duty” hours (52.0 vs 78.0 min, p = 0.001; 88.3% vs 72.3%, p = 0.047, respectively) than during “on-duty” hours (37.5 vs 43.5 min, p = 0.164; 94.4% vs 79.4%, p = 0.274, respectively). In addition, door-to-activation time (–39 vs 11 min, p < 0.001) and door-to-catheterization laboratory arrival time (33 vs 42 min, p = 0.007) were shorter in patients with prearrival notifications than those without. However, in-hospital mortality was similar between the two groups (6.3% vs 6.8%, p = 0.892).

Conclusion:

Prearrival direct notification calls to interventional cardiologists significantly improved the door-to-balloon time and the proportion of patients with door-to-balloon time < 90 min through rapid patient transport in primary percutaneous coronary intervention scheduled hospital and readiness of the catheterization laboratory.

Keywords

Myocardial infarction angioplasty primary percutaneous coronary intervention door-to-balloon time

Introduction

Timely primary percutaneous coronary intervention (PCI) is the optimal reperfusion strategy for ST-elevation myocardial infarction (STEMI) patients.¹ Studies have shown that shortened treatment times for STEMI patients who underwent primary PCI, such as door-to-balloon (DTB) time and transfer time, are strongly associated with improved cardiac function and favorable outcomes.^2–4 STEMI patients presenting to a PCI-capable hospital should be treated with primary PCI within 90 min of the DTB time, while STEMI patients in non-PCI-capable hospitals should be transferred immediately for primary PCI if the time from the first medical contact (FMC) to device insertion is expected to be within 120 min.¹ To minimize the transfer time for rapid reperfusion and to achieve guideline-stated target DTB times, several authors have suggested various efficient and coordinated regional strategies, such as prehospital electrocardiographic diagnosis, early activation of cardiac catheterization laboratory (CCL), and direct referral to a PCI-capable center.^5–13 We evaluated the effect of prearrival direct notification calls to interventional cardiologists on DTB time when transferring STEMI patients for primary PCI.

Methods

Study population

Our study region was the southeastern city of South Korea, which consisted of 766 km2 and served a population of 3.6 million inhabitants. This prospective observational study was conducted at a university hospital—a 1200-bed, urban, tertiary referral center. From January 2009 to December 2010, we included consecutive patients presenting to the emergency department (ED) with a clinical history and electrocardiographic changes consistent with STEMI who were candidates for primary PCI. Patients were excluded if they visited by walking, were treated with fibrinolysis, delayed PCI due to comorbidities, refused PCI, or died before PCI.

Study setting and protocol

Our hospital’s CCL is available 24 h a day, 7 days a week. During weekdays (07:00–18:00), all members of the PCI team are physically present in the hospital, while during weekends and at nights, an on-call interventional cardiologist is available within 20 min.

Since January 2009, we have implemented a 24-h hotline system with the Emergency Medical Information Center (EMIC) in our city to ensure that an on-duty interventional cardiologist receives a direct notification call from the EMIC in order to reduce inter-hospital transfer delay.

When a patient with chest pain arrives at a community hospital without PCI capability and acute STEMI is suspected, the physician in the community hospital diagnoses acute STEMI based on cardiac biomarker values, symptoms, and electrocardiographic findings and calls the EMIC to transfer the patient immediately to a primary PCI-capable hospital. If our on-duty interventional cardiologist receives a notification call from the EMIC licensed provider, he or she decides whether or not to activate the PCI team with a single call for performing to prepare for emergency coronary angiography with or without primary PCI while the patient is enroute to our hospital. The on-duty interventional cardiologist and PCI team members are required to arrive in the CCL within 20 min after the activation call. When the patient arrives at our hospital, he or she is evaluated briefly in the triage area and transported rapidly to the CCL.

When a STEMI patient is transferred to our hospital without a notification call from the EMIC, or visits the ED directly, an emergency physician evaluates the patient briefly, calls the on-duty interventional cardiologist, and activates the PCI team with a single call.

Primary PCI is performed according to current treatment guidelines for STEMI patients, and other practices including hospital care and medications for the prevention of secondary events are followed. After discharge, all patients are prescribed medications and followed up by their clinicians regularly. Patients who developed angina-like symptoms undergo complete clinical evaluation. If deemed necessary, the patients receive hospital care and revascularization.

For comparison, the study population was classified into patients with a prearrival direct notification call to the interventional cardiologist (prearrival notification group) and those without such calls (no prearrival notification group). All medical data were collected by trained study coordinators using a standardized case report form and protocol. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki as reflected by prior approval for this study by the ethics committee of our hospital. Written informed consent for the use of data was obtained from each patient.

Definitions and study endpoints

The primary endpoint was DTB time. Secondary endpoints included the proportion of patients meeting the current guidelines of DTB time <90 min, symptom onset-to-door time, and components of DTB time. Furthermore, DTB times were compared between “on-duty” and “off-duty” hours. “On-duty” hours were defined as a period from 07:00 to 18:00 during Monday through Friday. “Off-duty” hours were all other times or days, including public holidays. “False-alarms” were defined as no lesion on coronary angiography or canceled the activation by decision of emergency physician or interventional cardiologist.

Statistical analysis

Sample size calculations with an effect size of 0.5, alpha-error probability of 0.05, and power of 0.9 require 172 subjects to detect significant effects (G*Power 3.1.9.2, University of Kiel).¹⁴ Taking into account a possible dropout rate of one-tenth, we considered a sample size of 189 subjects as appropriate to study effects. Categorical variables were expressed as numbers with percentages and compared using Chi-square’s test or Fisher’s exact test, where appropriate. Continuous variables were expressed as mean ± standard deviation or median with interquartile ranges and compared using the independent t-test or Mann–Whitney test, where appropriate. To adjust for known confounding factors, we performed the multivariate regression analysis with DTB time as a dependent variable. The adjusted covariates included age, gender, hypertension, diabetes mellitus, prior ischemic heart disease, Killip class, left ventricular ejection fraction, time of arrival (on-duty or off-duty hours), extent of coronary disease, culprit vessel location, lesion type, initial thrombolysis in myocardial infarction flow grade, and vascular access site. p < 0.05 was considered statistically significant. All analyses were performed using SPSS 17.0 for Windows (SPSS Inc., Chicago, IL).

Results

A total of 228 consecutive STEMI patients who underwent primary PCI during the study period were included in this study. Of these, 95 patients (41.7%) were referred with prearrival direct notification calls from the EMIC, and 133 patients (58.3%) were either transferred without such calls or visited the ED directly. No significant differences were noted in the baseline clinical characteristics between the two groups (Table 1). The prearrival notification call was more common during “off-duty” hours than during “on-duty” hours (81.2% vs 18.9%, p < 0.001). Angiographic and procedural characteristics did not differ between the two groups (Table 2). In addition, of 95 patients with prearrival notification, false alarms occurred in 14 patients (14.7%).

Table 1.

Baseline clinical characteristics.

	Prearrival notification group (n = 95)	No prearrival notification group (n = 133)	p
Age, year	62.43 ± 12.7	62.05 ± 11.9	0.815
Male gender	69 (72.6%)	101 (75.9%)	0.572
Medical history
Hypertension	42 (44.2%)	60 (45.1%)	0.893
Diabetes mellitus	21 (22.1%)	38 (28.6%)	0.272
Smoking	60 (63.2%)	76 (57.1%)	0.361
Hypercholesterolemia	12 (12.6%)	18 (13.5%)	0.842
Prior IHD	22 (23.2%)	42 (31.6%)	0.163
Prior PCI	3 (3.2%)	9 (6.8%)	0.368
Systolic blood pressure, mmHg	119.6 ± 27.5	117.3 ± 33.5	0.596
Killip class
I	75 (78.9%)	91 (68.4%)	0.227
II	10 (10.5%)	24 (18%)
III	7 (7.4%)	9 (6.8%)
IV	3 (3.2%)	9 (6.8%)
Infarct location in ECG			0.822
Anterior/lateral	50 (52.6%)	72 (54.1%)
Inferior	45 (47.4%)	61 (45.9%)
LVEF, %	49.9 ± 10.3	52.4 ± 10.4	0.221
Time of arrival			<0.001
During on-duty hours^a	18 (18.9%)	68 (51.1%)
During off-duty hours^b	77 (81.2%)	65 (48.9%)
Transferring distance, km	24.4 ± 11.5	25.1 ± 12.5	0.186

BP: blood pressure; ECG: electrocardiogram; IHD: ischemic heart disease; LVEF: left ventricular ejection fraction; PCI: percutaneous coronary intervention.

Values are represented as mean ± standard deviation or n (%).

On-duty hours: 07:00–18:00 during Monday through Friday.

Off-duty hours: all other times or days, including public holidays.

Table 2.

Angiographic and procedural characteristics.

	Prearrival notification group (n = 95)	No prearrival notification group (n = 133)	p
Angiographic diagnosis			0.685
1 vessel disease	41 (43.2%)	58 (43.6%)
2 vessel disease	29 (30.5%)	46 (34.6%)
3 vessel disease	25 (26.3%)	29 (21.8%)
Culprit vessel			0.975
Left anterior descending	46 (48.4%)	66 (49.6%)
Left circumflex	10 (10.5%)	13 (9.8%)
Right coronary	39 (41.1%)	54 (40.6%)
Lesion type			0.292
B1	8 (8.4%)	9 (6.8%)
B2	40 (42.1%)	70 (52.6%)
C	47 (49.5%)	54 (40.6%)
Initial TIMI flow grade			0.074
0	60 (63.2%)	71 (53.4%)
1	10 (10.5%)	31 (23.3%)
2	15 (15.8%)	15 (11.3%)
3	9 (10.5%)	16 (12.0%)
PCI type			0.242
POBA	2 (2.1%)	8 (6.0%)
Bare metal stent	23 (24.2%)	41 (30.8%)
Drug-eluting stent	70 (73.7%)	84 (63.2%)
Stent length, mm	23.98 ± 9.12	23.55 ± 9.49	0.778
Stent diameter, mm	3.32 ± 2.31	3.08 ± 0.38	0.264
Number of stents	1.17 ± 0.41	1.21 ± 0.43	0.531
Procedural success	94 (98.9%)	128 (96.2%)	0.405
Vascular access site			0.426
Radial	39 (41.1%)	47 (35.3%)
Femoral	54 (56.8%)	85 (63.9%)
Crossover to femoral access	2 (2.1%)	1 (0.8%)

PCI: percutaneous coronary intervention; POBA: plain old balloon angioplasty; TIMI: thrombolysis in myocardial infarction.

Values are represented as mean ± standard deviation or n (%).

The DTB time was significantly shorter in patients with prearrival notification compared to patients without it (Table 3). The improvement in DTB time was greater during “off-duty” hours than during “on-duty” hours (Table 3, Figure 1). The proportion of patients with DTB time <90 min was significantly higher in the prearrival notification group compared to the no prearrival notification group. The increase in the proportion of patients with DTB time < 90 min was greater during “off-duty” hours than during “on-duty” hours (Table 3, Figure 2).

Figure 1.

Comparison of door-to-balloon time.

Figure 2.

The proportion of patients with door-to-balloon time <90 min.

Table 3.

Comparison of door-to-balloon time and PCI stratified by door-to-balloon time.

	Prearrival notification group (n = 95)	No prearrival notification group (n = 133)	p
Overall
DTB time, min	50.0 (31.0–69.0)	60.0 (35.5–88.5)	0.010
PCIs stratified by DTB time			0.034
<90 min	85 (89.5%)	101 (75.9%)
90–119 min	5 (5.3%)	15 (11.3%)
≥120 min	5 (5.3%)	17 (12.8%)
During on-duty hours^a	(n = 18)	(n = 68)
DTB time, min	37.5 (25.0–57.8)	43.5 (31.0–75.0)	0.164
PCIs stratified by DTB time			0.308
<90 min	17 (94.4%)	55 (80.9%)
90–119 min	0 (0%)	7 (10.3%)
≥120 min	1 (5.6%)	6 (8.8%)
During off-duty hours^b	(n = 77)	(n = 65)
DTB time, min	52.0 (34.5–72.5)	78.0 (49.0–92.0)	0.001
PCIs stratified by DTB time			0.027
<90 min	68 (88.3%)	46 (70.8%)
90–119 min	5 (6.5%)	8 (12.3%)
≥120 min	4 (5.2%)	11 (16.9%)

PCI: percutaneous coronary intervention; DTB: door-to-balloon.

Values are represented as median (interquartile range) or n (%).

On-duty hours: 07:00–18:00 during Monday through Friday.

Off-duty hours: all other times or days, including public holidays.

Concerning the components of DTB time, door-to-activation time and door-to-CCL arrival time were significantly shorter in the prearrival notification group than in the no prearrival notification group (Table 4). In the subgroup of both community and PCI-capable hospitals, DTB time, door-to-activation time, and door-to-CCL arrival time were still significantly shorter in the prearrival notification group than in the no prearrival notification group (Table 4). The negative value indicates that the PCI team activation had been completed before the patient arrived at the door of the ED. In multivariate regression analysis, the prearrival notification was associated with improved DTB time (p = 0.021). The in-hospital mortality did not differ between the two groups (6.3% vs 6.8%, p = 0.892).

Table 4.

Comparison of time components of percutaneous coronary intervention.

	Prearrival notification group (n = 95)	No prearrival notification group (n = 133)	p
Overall
Door-to-balloon time, min	50.0 (31.0–69.0)	60.0 (35.5–88.5)	0.010
Door-to-activation time, min	−39.0^a (–49.0–16.0)	11.0 (5.0–20.5)	<0.001
Door-to-consent time, min	13.0 (6.0–23.0)	20.0 (10.0–31.0)	<0.001
Door-to-ED departure time, min	28.0 (11.0–46.0)	35.0 (15.0–62.0)	0.007
ED-to-CCL arrival time, min	5.0 (3.0–5.0)	5.0 (3.0–5.0)	0.943
Door-to-CCL arrival time	33.0 (14.0–50.0)	42.0 (19.0–68.0)	0.007
CCL-to-puncture, min	5.0 (3.0–5.0)	5.0 (3.0–7.0)	0.409
CCL-to-balloon, min	15.0 (10.0–22.0)	16.0 (10.0–23.0)	0.785
Community hospital	(n = 57)	(n = 81)
Door-to-balloon time, min	49.5 (32.5–68.5)	59.0 (34.5–87.5)	0.012
Door-to-activation time, min	−39.5^a (–48.5–15.0)	12.5 (7.0–23.5)	<0.001
Door-to-consent time, min	12.5 (6.5–24.0)	19.0 (10.5–32.0)	0.011
Door-to-ED departure time, min	27.0 (10.0–45.5)	34.0 (14.0–60.5)	0.009
ED-to-CCL arrival time, min	5.0 (3.0–7.0)	5.5 (3.0–5.0)	0.746
Door-to-CCL arrival time	32.0 (13.0–48.5)	41.0 (18.0–66.5)	0.014
CCL-to-puncture, min	5.0 (3.0–5.5)	5.0 (3.0–6.5)	0.524
CCL-to-balloon, min	14.0 (10.0–20.5)	15.0 (10.0–22.0)	0.549
Non-PCI-capable hospital	(n = 38)	(n = 52)
Door-to-balloon time, min	50.7 (30.5–70.5)	60.5 (36.0–89.5)	0.008
Door-to-activation time, min	−38.5^a (–47.5–16.5)	10.5 (4.5–18.5)	<0.001
Door-to-consent time, min	13.5 (5.5–22.5)	20.5 (10.0–30.5)	<0.001
Door-to-ED departure time, min	28.5 (11.5–46.5)	36.0 (16.0–63.0)	0.005
ED-to-CCL arrival time, min	5.0 (3.0–5.0)	5.0 (3.0–5.0)	0.348
Door-to-CCL arrival time	33.5 (14.5–50.5)	42.5 (19.0–68.5)	0.006
CCL-to-puncture, min	5.0 (3.0–5.0)	5.0 (3.0–7.5)	0.294
CCL-to-balloon, min	15.5 (10.5–22.5)	16.5 (10.5–23.5)	0.467

CCL: cardiac catheterization laboratory; ED: emergency department.

Values are represented as median (interquartile range).

The negative value indicates that the decision had been completed before the patient arrived at the door of the ED.

Discussion

The major findings of this study are as follows. (1) In STEMI patients transferred for primary PCI, the DTB time was significantly shorter and the proportion of patients with DTB time <90 min was significantly higher in patients with a prearrival direct notification call to the interventional cardiologist compared with patients without such calls; (2) this improvement in DTB time and the proportion of patients with DTB time <90 min was more pronounced during “off-duty” hours than during “on-duty” hours; and (3) among the components of DTB time, the door-to-activation time and door-to-CCL arrival time was significantly shorter in patients with a prearrival direct notification call to the interventional cardiologist compared with patients without such calls. Based on our analyses, we support that the prearrival notification was strongly associated with better DTB time. Moreover, it can be postulated that the reduction of DTB time was mainly driven by the decreased door-to-activation time and door-to-CCL arrival time. We proved that prearrival notification may contribute to early activation, rapid CCL arrival, and timely reperfusion therapy.

Certain strategies have been suggested for reducing DTB time during primary PCI in STEMI patients. Ting et al.⁸ and Diercks et al.⁹ reported that prehospital ECG could result in the significant decrease in DTB time. Moreover, prehospital activation of the CCL¹⁰ or cardiologist,¹¹ prehospital diagnosis and direct transfer to the PCI center,⁷ and shorter interval from hospital arrival to STEMI diagnosis and CCL activation¹² were all associated with improvements in DTB time for STEMI patients undergoing PCI. Bradley et al.⁵ suggested six strategies that were significantly associated with faster DTB time, including the following: (1) emergency physicians activate the CCL (mean reduction in DTB time, 8.2 min); (2) a single call to a central page operator activates the laboratory (13.8 min); (3) the ED activates the CCL while the patient is enroute to the hospital (15.4 min); (4) the staff arrive in the CCL within 20 min after being paged (19.3 min); (5) an attending cardiologist is always on site (14.6 min); and (6) the staff in the ED and the CCL use real-time data feedback for ongoing training (8.6 min). Herein, if an emergency physician at a non-PCI-capable hospital identified a patient with suspected STEMI, he or she called the EMIC to seek the nearest primary PCI-capable hospital. Then, when the EMIC licensed provider directly called an on-duty interventional cardiologist at the PCI-capable hospital, the interventional cardiologist decided whether to activate the CCL staff members while the patient was enroute to the referral hospital. In our system, the cooperation between the emergency physician at the non PCI-capable hospital, the EMIC licensed provider, and the on-duty interventional cardiologist at the referral PCI-capable hospital was the key in reducing the DTB time. In our no prearrival notification group, the physicians at a non-PCI-capable hospital did not know about this prearrival notification system or thought that a direct transferring of acute STEMI patients would take a shorter time than the transferring after prearrival notification call to interventional cardiologist via EMIC. However, we showed that the prearrival notification call to interventional cardiologist was associated with improved DTB time. Thus, we are planning an extended use of this system in our city.

Other time interval parameters in STEMI patient care have been affected by new practices. Prehospital ECG by wireless systems, computing algorithms, and paramedics training have contributed to improvements in the time to reperfusion therapy, such as FMC-to-door time, door-to-ECG time, and ECG-to-balloon time.⁸ Moreover, a prehospital ECG and the subsequent direct transfer to a PCI-capable hospital are known to reduce FMC-to-door time, door-to-CCL time, and FMC-to-balloon time.^6,13 Rapid decision-making by prehospital PCI risk calculation would also be associated with improvements in reperfusion time. However, additional studies are needed to assess the effects of prehospital PCI risk calculation on time to coronary intervention. Herein, the inclusion of a prearrival direct notification call to the interventional cardiologist decreased various components of DTB time, including door-to-activation time and door-to-CCL arrival time. We postulate that a prearrival direct notification to the interventional cardiologist leads to a reduction in DTB time by early activation of the CCL team and rapid patient transport to the CCL in our hospital.

The effects of primary PCI during “off-duty” hours versus “on-duty” hours on DTB time and mortality have been inconclusive. Investigators have reported that longer DTB times and higher mortality are found in STEMI patients undergoing primary PCI during “off-duty” hours than during “on-duty” hours.^15,16 Holmes et al.¹⁷ and Casella et al.¹⁸ showed improvements in DTB time and mortality during “off-duty” hours by specialized STEMI network strategies. Herein, patients with a prearrival notification call had shorter DTB time and higher rates of patients meeting DTB time <90 min than those without such calls, particularly during “off-duty” hours.

The proportion of “false alarms” in prehospital STEMI diagnosis and activation of CCL teams is substantial, although the definition of “false alarms” has been inconsistent in previous studies. Garvey et al.¹⁹ reported that in CCL activation at 14 primary PCI hospitals participating in a statewide STEMI reperfusion program, inappropriate CCL activations occurred in 596 (15%) of 3973 patients. McCabe et al.²⁰ observed that 146 false alarms (35.5%) occurred in 411 STEMI activations in patients with suspected STEMI at two primary PCI-capable hospitals. False alarms comprised approximately 15% of patients in our study although an interventional cardiologist decided whether to activate CCL after ECG information was imparted by the EMIC licensed provider. Concomitant transmission of the ECG to a cellphone could reduce the number of false alarms that activate CCL teams in advance.⁸

Reducing time to PCI in STEMI patients results in enhanced cardiac function and improved clinical outcomes. CADILLAC trial showed that early reperfusion contributed to the improved left ventricular function, microvascular reperfusion, and survival.⁴ McNamara et al.³ concluded that a longer DTB time was associated with increased in-hospital mortality. A recent study found that the DTB time improved significantly during 4 years of follow-up, however, in-hospital mortality remained unchanged.²¹ This study also demonstrated comparable in-hospital mortality between groups, although the DTB time reduced significantly in the prearrival notification group compared with the no prearrival notification group. The reason for no improvement of in-hospital mortality in our study may be attributable to no further reduction of the total ischemia time. Multimedia public education campaigns, feedback to every care provider, and continuous training and education to hospitals and care providers are important methods for reducing the overall ischemic time and achieving improved prognoses.^22,23

Limitations

This study has some limitations. First, the sample size was relatively small. Second, this study was limited to a single academic medical center with continuous availability of a CCL and staff. However, this study does serve as a feasibility study for other medical centers. Third, we did not compare the rate of “false alarms” accurately between the two groups. Bradley et al.²⁴ have reported that in top-performing hospitals, such “false alarms” occur rarely and are acceptable. Finally, the prearrival call to emergency physicians at a primary PCI-capable hospital might decrease the DTB time, but we could not evaluate the impact of prearrival call to emergency physicians on DTB time.

Conclusion

This study showed that prearrival direct notification calls to interventional cardiologists significantly reduced the DTB time and significantly increased the proportion of patients with DTB time <90 min through rapid patient transport in primary PCI scheduled hospital and readiness of the catheterization laboratory. These improvements were more pronounced during “off-duty” hours than during “on-duty” hours. Our results suggest that a regional network using prearrival notifications through an information center may be an effective community-wide strategy for timely reperfusion in STEMI patients, particularly during “off-duty” hours.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References

O’Gara

Kushner

Ascheim

et al . 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2013; 61(4): e78–e140.

Milavetz

Giebel

Christian

et al . Time to therapy and salvage in myocardial infarction. J Am Coll Cardiol 1998; 31(6): 1246–1251.

McNamara

Wang

Herrin

et al . Effect of door-to-balloon time on mortality in patients with ST-segment elevation myocardial infarction. J Am Coll Cardiol 2006; 47(11): 2180–2186.

Brodie

Stone

Cox

et al . Impact of treatment delays on outcomes of primary percutaneous coronary intervention for acute myocardial infarction: analysis from the CADILLAC trial. Am Heart J 2006; 151(6): 1231–1238.

Bradley

Herrin

Wang

et al . Strategies for reducing the door-to-balloon time in acute myocardial infarction. N Engl J Med 2006; 355(22): 2308–2320.

Terkelsen

Lassen

Nørgaard

et al . Reduction of treatment delay in patients with ST-elevation myocardial infarction: impact of pre-hospital diagnosis and direct referral to primary percutaneous coronary intervention. Eur Heart J 2005; 26(8): 770–777.

Le May

Dionne

et al

A citywide protocol for primary PCI in ST-segment elevation myocardial infarction. N Engl J Med 2008; 358(3): 231–240.

Ting

Krumholz

Bradley

et al . Implementation and integration of prehospital ECGs into systems of care for acute coronary syndrome: a scientific statement from the American Heart Association Interdisciplinary Council on Quality of Care and Outcomes Research, Emergency Cardiovascular Care Committee, Council on Cardiovascular Nursing, and Council on Clinical Cardiology. Circulation 2008; 118(10): 1066–1079.

Diercks

Kontos

Chen

et al . Utilization and impact of pre-hospital electrocardiograms for patients with acute ST-segment elevation myocardial infarction: data from the NCDR (National Cardiovascular Data Registry) ACTION (Acute Coronary Treatment and Intervention Outcomes Network) Registry. J Am Coll Cardiol 2009; 53(2): 161–166.

10.

Camp-Rogers

Dante

Kontos

et al . The impact of prehospital activation of the cardiac catheterization team on time to treatment for patients presenting with ST-segment-elevation myocardial infarction. Am J Emerg Med 2011; 29(9): 1117–1124.

11.

Strauss

Sprague

Underhill

et al . Paramedic transtelephonic communication to cardiologist of clinical and electrocardiographic assessment for rapid reperfusion of ST-elevation myocardial infarction. J Electrocardiol 2007; 40(3): 265–270.

12.

McCabe

Armstrong

Hoffmayer

et al . Impact of door-to-activation time on door-to-balloon time in primary percutaneous coronary intervention for ST-segment elevation myocardial infarctions: a report from the Activate-SF registry. Circ Cardiovasc Qual Outcomes 2012; 5(5): 672–679.

13.

Mumma

Kontos

Peng

et al . Association between prehospital electrocardiogram use and patient home distance from the percutaneous coronary intervention center on total reperfusion time in ST-segment-elevation myocardial infarction patients: a retrospective analysis from the national cardiovascular data registry. Am Heart J 2014; 167(6): 915–920.

14.

Faul

Program G*Power, version 3.1.9.2 Kiel:University of Kiel, 2018, http://www.gpower.hhu.de/ on March 2018.

15.

Magid

Wang

Herrin

et al . Relationship between time of day, day of week, timeliness of reperfusion, and in-hospital mortality for patients with acute ST-segment elevation myocardial infarction. JAMA 2005; 294(7): 803–812.

16.

Sorita

Ahmed

Starr

et al . Off-hour presentation and outcomes in patients with acute myocardial infarction: systematic review and meta-analysis. BMJ 2014; 348: f7393.

17.

Holmes

Jr Bell

Gersh

et al . Systems of care to improve timeliness of reperfusion therapy for ST-segment elevation myocardial infarction during off hours: the Mayo Clinic STEMI protocol. JACC Cardiovasc Interv 2008; 1(1): 88–96.

18.

Casella

Ottani

Ortolani

et al . Off-hour primary percutaneous coronary angioplasty does not affect outcome of patients with ST-segment elevation acute myocardial infarction treated within a regional network for reperfusion: the REAL (Registro Regionale Angioplastiche dell’Emilia-Romagna) registry. JACC Cardiovasc Interv 2011; 4(3): 270–278.

19.

Garvey

Monk

Granger

et al . Rates of cardiac catheterization cancelation for ST-segment elevation myocardial infarction after activation by emergency medical services or emergency physicians: results from the North Carolina Catheterization Laboratory Activation Registry. Circulation 2012; 125(2): 308–313.

20.

McCabe

Armstrong

Kulkarni

et al . Prevalence and factors associated with false-positive ST-elevation myocardial infarction diagnoses at primary percutaneous coronary intervention–capable centers: a report from the Activate-SF registry. Arch Intern Med 2012; 172(11): 864–871.

21.

Menees

Peterson

Wang

et al . Door-to-balloon time and mortality among patients undergoing primary PCI. N Engl J Med 2013; 369(10): 901–909.

22.

Pitta

Myers

Bjerke

et al . Using prehospital electrocardiograms to improve door-to-balloon time for transferred patients with ST-elevation myocardial infarction: a case of extreme performance. Circ Cardiovasc Qual Outcomes 2010; 3(1): 93–97.

23.

Jacobs

Antman

Ellrodt

et al . Recommendation to develop strategies to increase the number of ST-segment-elevation myocardial infarction patients with timely access to primary percutaneous coronary intervention. Circulation 2006; 113(17): 2152–2163.

24.

Bradley

Roumanis

Radford

et al . Achieving door-to-balloon times that meet quality guidelines: how do successful hospitals do it? J Am Coll Cardiol 2005; 46(7): 1236–1241.