American Journal of Emergency Medicine (2011) 29, 1117-1124

Original Contribution

The impact of prehospital activation of the cardiac catheterization team on time to treatment for patients presenting with ST-segment-elevation myocardial infarction^?,??

Teresa Camp-Rogers MD ^a, Siddhartha Dante BA ^b, Michael C. Kontos MD ^c, Charlotte S. Roberts MSN ^c, Laura Kreisa BSN ^d,

Michael Christopher Kurz MD MS-HES ^a,?

^aDepartment of Emergency Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, USA

^bSchool of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA

^cDivision of Cardiology, Department of Internal Medicine, Virginia Commonwealth University Medical Center,

Richmond, VA 23298, USA

^dOffice of Performance Improvement, Virginia Commonwealth University Medical Center, Richmond, VA 23298, USA

Received 8 June 2010; revised 10 August 2010; accepted 11 August 2010

Abstract

Objective: We sought to evaluate the accuracy of emergency medical services (EMS) activation of the cardiac catheterization laboratory for patients with ST-elevation myocardial infarction and its impact on treatment intervals from dispatch to reperfusion.

Methods: We conducted a before-and-after cohort study of patients presenting via EMS with prehospital electrocardiogram findings consistent with STEMI. Before August 20, 2007, percutaneous coronary intervention was initiated after patient arrival. Afterward, EMS providers could activate the CCL if the prehospital electrocardiogram automated interpretation indicated STEMI. All interval times from EMS dispatch to percutaneous coronary intervention were measured via synchronized timepieces.

Results: A total of 53 patients, 14 before and 39 after prehospital activation, were included. Emergency medical services CCL activation was 79.6% sensitive (95% confidence interval [CI], 65.2%-89.3%) and 99.7% specific (95% CI, 99.1%-99.9%). Mean door-to-hospital electrocardiogram and mean CCL-to- reperfusion times were unaffected by the intervention. Prehospital activation of the CCL significantly improved mean door-to-balloon (D2B) time by 18.2 minutes (95% CI, 7.69-28.71 minutes; P = .0029) and door-to-CCL by 14.8 minutes (95% CI, 6.20-23.39 minutes; P = .0024). Improvements in D2B were independent of presentation during peak hours (F ratio = 17.02, P b .0001). There were significant Time Savings reflected in all EMS intervals: 20.7 minutes (95% CI, 9.1-32.3 minutes; P = .0015) in

^? Previous presentations: 2008 ACEP Research Forum, Chicago, Ill (abstract). 2008 SAEM Mid-Atlantic Regional Meeting, Hershey, Pa (oral) (Best Resident Presentation). 2008 Inter-American Conference on Emergency Medicine, Buenos Aires, Argentina (oral) (First Prize). 2009 VACEP Hot Topics Conference, Hot Springs, Va (abstract) (McDade Research Award).

^?? Financial Support: None.

* Corresponding author. Virginia Commonwealth University, MCV Campus, PO Box 980401, Richmond, VA 23298-0401, USA. Tel.: +1 804 828 5250.

E-mail address: [email protected] (M.C. Kurz).

0735-6757/$ - see front matter (C) 2011 doi:10.1016/j.ajem.2010.08.005

mean dispatch-to-reperfusion time, 22.2 minutes (95% CI, 11.45-32.95 minutes; P = .0003) in mean first medical contact-to-reperfusion time, and 20 minutes (95% CI, 10.95-29.05 minutes; P = .0001) in recognition-to-reperfusion time.

Conclusions: Emergency medical service providers can appropriately activate the CCL for patients with STEMI before emergency department arrival, significantly reducing mean D2B time. Significant reduction is demonstrated throughout EMS intervals.

(C) 2011

Introduction

Despite a significant body of medical literature demon- strating that timely access to Primary percutaneous coronary intervention for patients presenting with ST-elevation myocardial infarction improves morbidity and mortality both immediately post-intervention and at 1 year, a minority of patients receive mechanical reperfusion within the American College of Cardiology/American Heart Association (ACC/AHA) 90-minute Door-to-balloon time (D2B) guideline [1-6].

Recently, a number of professional groups, including the ACC D2B, An alliance for Quality, A Guidelines Applied in Practice Program (d2balliance.org), and the AHA Mission: Lifeline, have focused on reducing delays in performance of PCI in patients with STEMI [7]. Manyadvocate for emergency medical services (EMS) to obtain an electrocardiogram (ECG) and activate the cardiac catheterization laboratory (CCL) before the patient’s arrival [1,8]. Although the acquisition of a prehospital 12-lead ECG (PHECG) and its transmission to hospital stationed personnel (emergency physician [EP], cardiologist, registered nurse, etc) have been shown to improve D2B times, there is little literature independently examining the accuracy or impact of prehospital activation of the CCL on D2B or other interval times [2,9-11].

The objective of this study was to determine how accurately EMS activates the CCL for prehospital identified STEMI and its impact on D2B and other relevant associated intervals.

Methods

Study design

We conducted a before-and-after cohort study to evaluate the impact of prehospital activation of the CCL on time to treatment for patients arriving via EMS with a clinical history and prehospital ECG consistent with STEMI. The study was reviewed and granted expedited approval by our institutional review board.

Setting

Our investigation was conducted at a 766-bed tertiary care hospital in the Mid-Atlantic region of the United States. It is

the only large, public university hospital within a 60-mile radius. The emergency department (ED) has a yearly volume of 85 000 patients, of which approximately 65 patients present with STEMI. Approximately 60% of all STEMI cases arrive by EMS. The entire emergency medicine attending staff is board certified in emergency medicine and supports an emergency medicine residency.

Before the study, STEMI care at the institution was well optimized with multiple strategies to reduce D2B in place including EP activation of the CCL via a single page activation, CCL team ready in 30 minutes, consolidated “STEMI drug kits,” standardized order sets, prompt feedback to all stakeholders inclusive of EMS, Multidisciplinary team- based approach, and a senior management commitment. During the approximately 36-month investigation, the institution had only 2 quarters with less than 100% compliance with D2B less than 90 minutes (fourth quarter 2006, 86%; and third quarter 2007, 90%).

The institution is primarily served by 3 career EMS agencies, 2 of which are fire department based, and account for greater than 93% of EMS STEMI volume. All transport units in these agencies are staffed with paramedics and have had PHECG capability with automated interpretation for more than 5 years. Paramedic continuing education concerning acute coronary syndrome and ECG interpretation occurs at least biannually in each agency.

Selection of participants

Consecutive patients presenting to the ED via EMS from August 19, 2006, to June 4, 2009, with chest pain or other symptoms consistent with myocardial ischemia and a PHECG consistent with STEMI were eligible. After August 20, 2007, prehospital CCL activation was added to the inclusion criteria. A PHECG was considered indicative of STEMI if 1 mV (1 mm) ST elevation was present in 2 or more anatomically contiguous limb leads or 2 mV (2 mm) of ST elevation was present in 2 or more anatomically contiguous precordial leads. All PHECGs were reviewed by 2 study authors. Patients were clinically excluded if they were transferred from an outside hospital, appropriately did not receive PCI (N12 hours of symptoms, demonstrated a contraindication to PCI, had a valid do-not-resuscitate order, refused PCI, died before PCI could be attempted, etc), or had a significant appropriate treatment delay (evaluation for stroke or aortic dissection, cardiac arrest, emergent intubation upon arrival in ED, etc). Each STEMI

was confirmed by an appropriate rise and fall of cardiac biomarkers and emergent coronary angiography with PCI. Furthermore, reports from each PCI procedure were reviewed by a study physician to ensure symptom improvement and/or biomarker resolution with treatment of the culprit lesion.

Intervention

Before August 20, 2007, the attending EP activated the CCL upon presentation of a patient with a history and ECG consistent with STEMI regardless of Method of arrival. Afterward, a standardized process was initiated for prehos- pital CCL activation for patients with STEMI. EMS providers were directed to acquire a PHECG on all patients with history and symptoms consistent with a potential acute coronary syndrome. If that PHECG was accompanied by the automated interpretation “?? ?? ?? ACUTE MI ?? ?? ??,” the EMS provider was instructed to contact our institution via normal communication channels and relay the ECG findings as early as possible. An attending EP would confirm the protocol and activate the CCL before the patient’s arrival. Although EMS providers were free to add additional clinical details or their own personal description of the PHECG during this field-to- EP communication, at no time was a PHECG transmitted to the EP for review before the patient’s arrival.

Methods of measurement

Time-to-treatment intervals used for comparison included the traditional composite D2B and other component intervals: door-to-ECG (D2E), door-to-laboratory (D2CCL), and laboratory-to-reperfusion (CCL2B) time. Door time was defined as the time the patient physically crossed the threshold of the ED as verified by electronic time stamp; the first documented balloon inflation beyond the culprit lesion was recorded as the reperfusion time. All other interval times were measured via computer clocks or electronic time stamp synchronized at least weekly. A patient’s arrival period was defined by their “door time” as either peak (Monday-Friday 7:00 AM-7:00 PM, excluding institutional holidays) or off-peak based on the need to call the cardiac catheterization team from home.

Each patient’s prehospital record was individually reviewed to document and calculate the EMS inclusive intervals of EMS dispatch-to-reperfusion (D2R), EMS patient contact-to- reperfusion (FC2R) and PHECG acquired and consistent with STEMI, or recognition-to-reperfusion (R2R) (Fig. 1).

Data collection

The collection of data for all patient characteristics and study outcomes occurred retrospectively via medical

Fig. 1 Timeline for the process of reperfusion. ?D2E = Door-to-ECG time interval.

Patients presenting to ED with STEMI during Study Period N = 175

EMS N = 130

Walk-in or Helicopter N = 45

Positive PHECG N = 99

Study Subjects N = 63

No or Normal PHECG

N = 31

Clinically Excluded N = 36

Before August 20, 2007 After August 20, 2007

No Prehospital Activation

N = 10

Activation of CCL after patient arrival N = 14

Prehospital activation of CCL N = 39

Fig. 2 Selection of patients by inclusion and exclusion criteria.

record review. Data were collected by a cardiology nurse practitioner or study physician using a standardized data collection form and definitions of intervals noted above. Correct data entry was electronically confirmed in all cases by a registered nurse certified in professional in health care quality (CPHQ). Data collection was overseen by an independent, blinded study physician. All data collected from paper primary source documents were again cross-checked where possible against comput- erized records.

Data analysis

All data were compiled into a spreadsheet and analysis was accomplished using statistical methods for calcula- tions provided within the software (Excel 2003, Microsoft, Redmond, Wash). Student t tests were used to calculate the mean difference of interval times for each cohort, as well as additional secondary outcome intervals as noted. A 2-way analysis of variance (ANOVA) was used to determine the influence of presentation time (peak vs off-peak) on measured intervals after the intervention.

Results

During the study period, a total of 175 STEMI patients were treated at our institution. Of these, 130 were brought in via ground EMS, 39 patients presented to the ED via triage (walk-in), and 6 presented by helicopter. Among the patients brought in by EMS, 31 had no or a normal PHECG and 36 of the remaining 99 with a positive PHECG were excluded on clinical grounds, including 12 cardiac arrests with return of spontaneous circulation (ROSC). Sixty-three patients had a positive PHECG and met the inclusion criteria, 14 before and

49 after implementation of the prehospital activation

Table 1 Distribution of enrolled patients by age, sex, and arrival time

Control		Activation
Age (mean)	55	58
Female	4 (29%)	15 (38%)
Arrival time
Peak	6 (43 %)	20 (51 %)
Off-peak	8 (57 %)	19 (49 %)

Time of presentation	Control	Prehospital activation		F ratio	P
Off-peak	75.4 (13.3)	55.5	(13.1)	17.02	b.0001
Peak	55.3 (17.7)	42.1	(14.3)
F ratio	17.4
P	b.0001	Correlation = 0 1

Fig. 3 The effect of prehospital activation on D2E and CCL- balloon intervals.

Table 2 Results of 2-way ANOVA of the influence of time of presentation (peak vs off-peak) and prehospital activation of the CCL on mean D2B time presented as mean (SD)

protocol. Ten patients were excluded from the intervention cohort as the CCL was not activated prehospital. Thirty- nine patients with appropriate prehospital activation of the CCL for STEMI comprised the intervention cohort for comparison (Fig. 2).

Complete data were available for each patient except one (in the intervention cohort) where recognition time could not be determined and was excluded from the R2R interval analysis only. Among the 53 patients enrolled, the average age was 57 years, with 34 being men. They were equally likely to present during peak and off-peak hours when the cardiac catheterization team was called in from home (P =

.60). Table 1 describes the characteristics of each cohort.

Seven additional inappropriate prehospital activations of the CCL occurred during the interventional cohort for the following circumstances: 4 instances of protocol violations where EMS personnel incorrectly reporting the PHECG as “STEMI” without confirmed automated interpretation,

2 instances of incorrect automated interpretation by the device due to artifact, and 1 was indeterminate despite diligent investigation by the authors. During the intervention period, EMS inappropriately activated the CCL team 3 times and failed to activate the CCL 10 times yielding 79.6% sensitivity (95% CI, 65.2%-89.3%) and 99.7% specificity

(95% CI, 99.1%-99.9%).

120

ED Activation

Pre-Hospital Activation

100

80

60

40

20

0

D2R FC2R R2R D2L D2B

Fig. 4 The effect of prehospital activation on D2R, EMS FC2R, R2R, D2CCL, and D2B.

All patients in our investigation had a D2B of less than 90 minutes except one patient in the preintervention cohort with a D2B of 101 minutes. From the time of EMS dispatch to reperfusion, 7 time intervals noted above were calculated for comparison between the 2 groups (Fig. 1). Of the in-hospital intervals, mean D2E (7.2 vs 4.9 minutes [95% CI, -0.52 vs

5.30]; P = .13) and mean CCL2B (26.4 vs 23.8 minutes

[95% CI, -2.97 vs 8.17]; P = .37) were not significantly affected by prehospital activation of the CCL (Fig. 3).

The process of prehospital activation of the cardiac catheterization team significantly improved all other mea- sured intervals both prehospital and in-hospital (Fig. 4). Prehospital intervals of mean D2R, mean FMC2R, and mean R2R time improved by 20.7 minutes (109.0 vs 88.3 [95% CI, 9.1 vs 32.3]; P = .0015), 22.2 minutes (101 vs 78.8 [95% CI,

11.45 vs 32.95]; P = .0003), and 20 minutes (88.1 vs 68.1

[95% CI, 10.95 vs 29.05]; P = .0001), respectively. In addition, the mean composite D2B time improved by

18.2 minutes (95% CI, 7.69 vs 28.71; P = .0029) from

66.8 to 48.6 minutes and the mean D2CCL time was decreased by 14.8 minutes (95% CI, 6.20 vs 23.39; P =

.0024) from 40.4 to 25.6 minutes.

Improvements in the D2B seen during the intervention cohort were subjected to a 2-way ANOVA to determine the influence of peak vs off-peak presentation. Although all effects were found to be statistically significant, prehospital activation of the CCL improved D2B independent of peak vs off-peak presentation (prehospital activation F ratio of 17.02, P b .0001; peak presentation F ratio of 17.4, P b .0001). The interaction of the 2 variables was nonsignificant (F ratio of 0, P = 1.00) (Table 2).

Limitations

Several limitations are important to consider when interpreting these results. The use of a before-after study design model without a concurrent control cohort makes it difficult to determine if the reduction in D2B and FC2R is due to prehospital CCL activation or to other events temporally related but otherwise unmeasured. Although a contemporaneous control design may have minimized the potential influence of these unanticipated events, such a

cumbersome system would have been logistically infea- sible to implement at this institution and maintain meaningful data.

Although the possibility of unmeasured events influenc- ing our results cannot be excluded, its potential influence should be severely limited. A multidisciplinary hospital-wide initiative to improve D2B began 9 months before the beginning of this study. As such, the entire staff of each affected department (responding EMS agencies, ED, cardi- ology, and the CCL team) were aware of the increased institutional scrutiny on STEMI care. In the 9 months before this study, the mean D2B for all STEMI patients, inclusive of those with potential treatment delays otherwise excluded from this investigation, was 73 minutes. This unintended “wash-out” period should minimize any potential Hawthorne effect. Furthermore, prehospital activation of the CCL was the only structural change made to the activation cascade during the study period that has been previously reported to affect D2B [8].

Discussion

For patients with STEMI, reducing total Ischemic time has traditionally been limited to improving the D2B time. Within the D2B interval, the hospital-based health care team can directly improve mortality by rapidly delivering reperfusion therapy. Public awareness campaigns to reduce the symptom onset to health care access component of total ischemic time have met with little success [12]. Despite such campaigns, patients suspected of having myocardial infarc- tion continue to wait an average of 2 hours to seek care for their symptoms [13-15]. However, by improving STEMI systems of care, including EMS PHECG acquisition, EMS destination protocols, and prehospital activation of the CCL, further important inroads to reduce total ischemic time can be achieved.

The potential of PHECG and EMS activation of the CCL to substantially improve D2B has lead to recommendations from the National Heart Attack Alert Program, the ACC/ AHA Guidelines on Emergency Cardiac Care, and the ACC D2B Alliance [7,16,17]. The first studies of prehospital ECGs demonstrated an increase the frequency of diagnosis of STEMI and a decrease in time to reach that diagnosis [18,19]. Additional studies have examined the impact of transmission of the prehospital ECG both to the ED and directly to alternate CCL activation decision-makers [20,21]. Furthermore, EMS providers can accurately interpret the prehospital ECG for STEMI and make destination decisions [22-28] without markedly increasing transport times to the hospital [19,29-31]. Prehospital ECGs are similar in accuracy for diagnosing STEMI when compared to the Standard ECG obtained in the ED [32]. Simply acquiring the prehospital ECG has been shown to reduce overall D2B [7,27,33], and directly impact mortality [25,27]. With this

evidence, the 2004 AHA guidelines recommend that EMS obtain prehospital ECG’s as part of the management of patients with suspected AMI [1]. Recent literature has suggested improvements in D2B are possible with prehos- pital activation of the CCL [34,35]. Despite a significant and growing body of literature that demonstrates the value of the prehospital ECG in diagnosis and treatment of STEMI, it is used in less than 28% of patients with STEMI [4,13,36,37]. Although prehospital activation of the CCL and its impact on D2B has been described [8,11,35], to the authors’ knowledge, it has never been examined in isolation. Our investigation was specifically designed to isolate the accuracy and impact of prehospital communication to activate the CCL. Furthermore, our results occurred in the context of a well-optimized PCI center and EMS agencies with significant previous experience with prehospital ECG and extensive training to recognize STEMI long before implementing the change. The context of this study is important as these institutional improvements and simply having a positive prehospital ECG have previously been shown to decrease D2B [8,34,36,38] and potentially diluting

the impact of prehospital activation.

Our investigation confirms that EMS can activate the CCL accurately, independent of ECG transmission, and that this simple change in the STEMI treatment cascade can significantly reduce D2B even in a well-optimized PCI center. The 22-minute reduction in FMC2R and the 18.2- minute reduction in D2B were achieved because prehospi- tal activation of the CCL allows previously sequential treatment steps to occur in parallel (ie, CCL members may travel from home while the EMS unit delivers the patient from the field). Closer examination of this result localizes the time savings to the reduction in the D2CCL interval despite any significant change in the D2E interval suggesting the shorter D2B time resulted from the CCL being ready sooner. With adequate advanced notice, ideally the D2CCL interval would approach zero as stable STEMI patients could proceed directly to the CCL and have the necessary pre-procedure preparations (hospital registration, consent, laboratory studies, medication administration, etc) done in the suite.

The difference in D2B among peak and off-peak presentations is this investigation congruent with an approximate 21-minute delay reported in the CADILLAC trial [39]. However, our study demonstrates the benefit of prehospital activation of the CCL is conferred independent of time of presentation, essentially negating the “off-peak” disadvantage and further reducing D2B for patients present- ing during business hours.

Not surprisingly, the time intervals of D2E and CCL2B were unaffected by the study intervention, reflecting the reliance of these intervals on an operator’s technical skill. Furthermore, with the ECG acquired and CCL activated by EMS prehospital, the urgency of acquiring the first ED ECG is lost as the rate-limiting step to providing rapid reperfusion has been eliminated.

Our investigation sought to determine which of the Prehospital time intervals were affected by prehospital activation. A remarkable reduction in FMC2R of 22.2 min- utes, bringing that interval below 90 minutes, was realized. The measurement of this “EMS inclusive” interval represents a significant step forward in reducing total ischemic time for patients with STEMI. The authors humbly advocate for the widespread adoption of quality intervals that include EMS providers as members of the health care team and recognize the potential of EMS to positively affect morbidity and mortality as part of larger STEMI systems of care. As early as 2004, the AHA/ACC guidelines suggested measuring FMC2R, which seems the logical universal benchmark for those patients with STEMI arriving by EMS [13,40,41].

The reduction in R2R and D2B achieved with prehospital activation of the CCL relies fundamentally on confidence in EMS to appropriately identify STEMI (in this investigation via automated interpretation) and appropriately communi- cate that interpretation independent of transmission of the ECG in question. Despite concern about the substantial cost of inappropriate EMS activations of the CCL, this event occurred only 7 times during our study during a 17-month period yielding a false-positive rate of 17%. However, if one eliminates the 4 inappropriate activations for protocol violations and assumes the others were due to an error by EMS, the false-positive rate drops to 8% consistent with other topical literature and similar to false-positive rates demonstrated by EPs [42,43]. These false-positive activa- tions underscore the importance of ongoing education and continuous quality assurance for all stakeholders, including EMS providers, involved in the STEMI process of care.

Conclusions

We found that prehospital activation of the CCL is associated with significant reductions in the composite D2R, FC2R, R2R, D2B, and the interval D2CCL. The improve- ment in D2B time experienced with prehospital activation occurred independent of when the patient with STEMI presented. Even relatively small improvements in composite D2B have become of critical importance with more recent literature demonstrating a direct relationship between D2B and mortality [5,6,44]. The Survival benefit imparted by reductions in time to reperfusion achieved in this study, when EMS providers are empowered to activate the CCL based on the prehospital ECG, has the potential to significantly improve outcomes for patients with STEMI.

References

1. Antman EM, Anbe DT, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction- executive summary. A report of the American College of Cardiology/

American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2004;44:671-719.

1. Bachour F, Smith S, et al. Effect of prehospital catheterization lab activation on door-to-balloon time of STEMI patients presenting during normal workday hours vs. after hours. Circulation 2007;116:II527-8.
2. Cucherat M, Bonnefoy E, et al. primary angioplasty versus intravenous thrombolysis for acute myocardial infarction. Cochrane review. Chichester, United Kingdom: John Wiley and Sons; 2004.
3. Curtis JP, Portnay EL, et al. The pre-hospital electrocardiogram and time to reperfusion in patients with acute myocardial infarction, 2000- 2002: findings from the National Registry of Myocardial Infarction-4. J Am Coll Cardiol 2006;47:1544-52.
4. Nallamothu BK, Bradley EH, et al. Time to treatment in primary percutaneous coronary intervention. N Engl J Med 2007;357:1631-8.
5. De Luca G, Suryapranata H, Ottervanger JP, Antman EM. Time delay to treatment and mortality in primary angioplasty for acute myocardial infarction: every minute of delay counts. Circulation 2004;109:1223-5.
6. Door to Balloon Alliance. American College of Cardiology; 2006. Accessed June 2, 2008. http://www.d2balliance.org.
7. Bradley EH, Herrin J, et al. Strategies for reducing the door-to-balloon time in acute myocardial infarction. N Engl J Med 2006:2308-19.
8. Brown JP, Mahmud E, et al. Effect of pre-hospital 12-lead electrocardiogram activation of the cardiac catheterization laboratory and door-to-balloon time in ST-segment elevation acute myocardial infarction. Am J Cardiol 2008;101:158-61.
9. Rokos IC, Larson DM, et al. Rational for establishing regional ST- elevation myocardial infarction receiving center network. Am Heart J 2006;152:661-7.
10. Swor R, Hegerberg S, et al. Prehospital 12-lead ECG: efficacy or effectiveness? Prehosp Emerg Care 2006;10:374-7.
11. McGinn AP, Rosamond WD, Goff Jr DC, et al. Trends in prehospital delay time and use of emergency medical services for acute myocardial infarction: experience in 4 US communities from 1987-2000. Am Heart J 2005;150:392-400.
12. Leupker RV, Raczynski JM, et al. Effect of a community intervention on patient delay and emergency medical service use in acute coronary heart disease: the Rapid Early Action for Coronary Treatment (REACT) Trial. JAMA 2000;284:60-7.
13. Caldwell MA, Miaskowski C. Mass media interventions to reduce help-seeking delay in people with symptoms of acute myocardial infarction: time for a new approach? Patient Educ Couns 2002;46:1-9.
14. Kainth A, Hewitt A, et al. Systematic review of interventions to reduce delay in patients with suspected heart attack. Emerg Med J 2004;21: 506-8.
15. Garvey JL, MacLeod JL, et al. Pre-hospital 12-lead electrocardiogra- phy programs: a call for implementation by emergency medical services systems providing advanced life support. J Am Coll Cardiol 2006;47:485-91.
16. Ting HH, Krumholz HM, et al. Implementation and integration of prehospital ecgs into systems of care for acute coronary syndrome: a scientific statement from the American Heart Association Interdisci- plinary Council on Quality of Care and Outcomes Research, Emergency Cardiovascular Care Committee, Council on Cardiovas- cular Nursing, and Council on Clinical Cardiology. Circulation 2008; 118:1066-79.
17. Aufderheide T, Hendley G, et al. The diagnostic impact of pre-hospital 12-lead electrocardiography. Ann Emerg Med 1990;19:1280-7.
18. Aufderheide T, Hendley G, et al. A prospective evaluation of pre- hospital 12-lead ECG application in chest pain patients. J Electro- cardiol 1992;24:8-13.
19. Papouchado M, Cox H, et al. Early experience with transmission of data from moving ambulances to improve care of patients with myocardial infarction. J Telemed Telecare 2001;7:27-8.
20. Sekulic M, Hassunizadeh B, et al. Feasibility of early emergency room notification to improve door-to-balloon times for patients with Acute ST-segment elevation myocardial infarction. Catheter Cardiovasc Interv 2005;66:316-9.
21. Miller-Craig MW, Joy AV, et al. Reduction in treatment delay by paramedic ECG diagnosis of myocardial infarction with direct CCU admission. Heart 1997;78:456-61.
22. Pitt K. Pre-hospital selection of patients for thrombolysis by paramedics. Emerg Med J 2002;19:260-3.
23. Keeling P, Hughes D, et al. Safety and feasibility of pre-hospital thrombolysis carried out by paramedics. Br Med J 2003;327:27-8.
24. LeMay MR, Davies RF, et al. Comparison of early mortality of paramedic-diagnosed ST-segment elevation myocardial infarction with immediate transport to a designated primary percutaneous coronary intervention center to that of similar patients transported to the nearest hospital. Am J Card 2006;98:1329-33.
25. Foster DB, Dufendach JH, Barkdoll CM, Mitchell BK. Prehospital recognition of AMI using independent nurse/paramedic 12-lead ECG evaluation: impact on in-hospital times to thrombolysis in a rural community hospital. Am J Emerg Med 1994;12(1):25-31.
26. Morrison LJ, Brooks S, Sawadsky B, McDonald A, Verbeek PR. Prehospital 12-lead electrocardiography impact on acute myocardial infarction treatment times and mortality: a systematic review. Acad Emerg Med 2006;13(1):84-9.
27. Trivedi K, Schuur JD. Cone DC. Can paramedics read ST-segment elevation myocardial infarction on 12-lead electrocardiograms. Pre- hosp Emerg Care 2009;13(2):207-14.
28. Karagounis L, Ipsen SK, Jessop MR, Gilmore KM, Valenti DA, Clawson JJ. Impact of field-transmitted electrocardiography on time to in-hospital thrombolytic therapy in acute myocardial infarction. Am J Cardiol 1990;66(10):786-91.
29. Brown JL. An eight-month evaluation of Prehospital 12-lead electrocardiogram monitoring in Baltimore County. Md Med J 1997 (Suppl):64-6.
30. Swor R, Hegerberg S, Mc-Hugh-McNally A, Goldstein M, McEachin

CC. Prehospital 12-lead ECG: efficacy or effectiveness. Prehosp Emerg Care 2006;10(3):374-7.

1. Ioannidis JL, Salem D, Chew PW, Lau J. Accuracy and clinical effect of prehospital electrocardiography in the diagnosis of Acute cardiac ischemia: a metaanalysis. Ann Emerg Med 2001;37:461-70.
2. Eckstein M, Pratt FD, et al. Impact of paramedic transport with out-of- hospital 12-lead ECG on door-to-balloon times for ST-segment myocardial infarction patients. Ann Emerg Med 2007;50: S56.
3. Bachour FA, Smith SW, et al. Effect of prehospital cath lab activation on door to balloon time of STEMI patients presenting during normal workday hours vs. after hours. Circ 2007;116:II527-8.
4. Smith SW, Hildebrandt DA, et al. Paramedic pre-hospital cath lab activation for STEMI, without ECG transmission, dramatically reduces door-to-balloon time. Circ 2007;116:II430.
5. Canto JG, et al. The pre-hospital electrocardiogram in acute myocardial infarction: is its full potential being realized? National Registry of Myocardial Infarction 2 Investigators. J Am Coll Cardiol 1997;29:498-505.
6. Diercks DB, Kontos MC, Chen AY, 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. JACC 2009;53(2): 161-6.
7. Bradley EH, Curry LA, et al. Achieving rapid door-to-balloon times: how top hospitals improve clinical systems. Circ 2006;113:1079-85.
8. Sadeghi HM, Grines CL, Chandra HR, Mehran R, Fahy M, Cox DA, et al. Magnitude and impact of treatment delays on weeknights and weekends in patients undergoing primary angioplasty for acute myocardial infarction (the CADILLAC Trial). Am J Cardiol 2004; 94:637-40.
9. Seipmann DB, Mann NC, et al. Association between prepayment systems and emergency medical services use among patients with acute chest discomfort syndrome. For the Rapid Early Action for Coronary Treatment (REACT) Study. Ann Emerg Med 2000;35: 573-8.
10. Ornato JP. The ST-segment-elevation myocardial infarction Chain of survival. Circulation 2007;116:6-9.
11. Feldman JA, Brinsfield K, et al. Real-time paramedic compared with Blinded physician identification of ST-segment elevation myocardial infarction: results of an observational study. Am J Emerg Med 2005; 23:443-8.
12. Kudenchuk PJ, Maynard C, et al. Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes. J Am Coll Cardiol 1998;32:17-27.
13. McNamara RL, Wang Y, et al. Effect of door-to-balloon time on mortality in patients with ST-segment elevation myocardial infarction. J Am Coll Cardiol 2006;47:2180-6.