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Three Part Question

In patients with [Acute Myocardial Infarction] does a [pre-hospital ECG] shorten the [door to needle time without prolonging the overall pain to needle time]?

Clinical Scenario

Your department is put on standby for a forty year old man with cardiac chest pain. The ECG is diagnostic of acute myocardial infarct and you thrombolize him after twenty five minutes in the department. You wonder whether a pre-hospital ECG would have shortened the door to needle time, without excessive "on scene" times.

Search Strategy

Medline 1966-April 2004 and Embase 1980-April 2004 using the Ovid interface.
[exp Emergency medical service OR exp ambulance OR pre-hospital.mp OR paramedic mp OR exp emergency medical technicians OR exp emergency treatment OR exp pre-hospital] AND [EKG OR electrocardiogram.mp OR exp ECG OR ECG.mp OR exp electrocardiography OR exp EKG] AND [exp myocardial infarction OR myocardial infarction mp OR acute myocardial infarct$.mp OR AMI.mp OR MI.mp OR heart attack.mp]

Search Outcome

589 papers were found of which 35 were relevant. Nine papers directly addressed the question

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Karagoumis et al, 1990	N = 71 Patients with cardiac sounding chest pain, transported by EMS	PRCT	On scene times	ECG – 16.4+/- 9.7 min No ECG – 16.1 +/- 7 mins	Small numbers No power study
			Transport time	ECG 18.2 mins No ECG 17.6 mins
			Time to thrombolysis	ECG 48+/- 12 mins No ECG 68+/- 29 mins
Kareiakaes et al, 1992, USA	N = 132 Patients with cardiac chest pain in Emergency Department Or calling for 911 transport	Prospective Cohort	In hospital time delay from arrival to treatment (25th – 75th centile)	Walk In = 64 minutes (46-87 mins) Other ambulance = 55 mins (45-68) EMS – no ECG = 50 mins (38-81 mins) EMS with ECG = 30 mins (27-35 mins)	V small numbers actually randomized Randomization method not clear Lack of power in study therefore unable to demonstrate statistically significant differences
Aufderheide et al, 1994, USA	N = 680 All patients with chest pain (cardiac sounding)	Prospective Cohort	On scene times by Paramedics	Study 29 +/- 7 mins Control 25 +/- 6 mins	One third of eligible patients excluded High rate of failed transmissions (22%) Retrospective control group from 6 months before
			Time savings – from potential pre-hospital treatment	101 +/- 81 mins
Melville et al, 1998, UK	N = 100 Consecutive patients with chest pain suggestive of AMI over 3 month period	Prospective Cohort	Median door to needle time savings	Study – 22 mins Controls – 28 mins (6 minutes saved)	100 ECG's ?Convenient numbers Used historic control over 3 years previously Time saved not directly attributable to ECG's since bypassing A&E reduced time (DTN)
Canto et al, 1997, USA	Voluntary data base of patients with AMI – from participating hospitals2 year period N = 275,046	Retrospective Cohort	Pain to 1st ECG	ECG – 120 mins No ECG – 108 mins	Non consecutive patient enrolment group Pre-hospital ECG group included variable sources GP office to EMS Not all hospitals included in register Possible bias from rural/urban differences Small percent (5%) with pre-hospital ECG's. Groups significantly different
			Median door to PTCA time	ECG – 92 mins No ECG – 115 mins
			Median door to thrombolysis time	ECG – 30 mins No ECG – 40 mins
			Hospital morbidity & mortality	No significant difference
Brown and Galloway, 2000, Australia	Patients with suspected acute MI where studies looked at pre-hospital ECG usage	Systematic review	Door to needle times	Consistently improved	Only looked at Medline (single database) Conclusion not consistent with results No report on authors assessing validity of studies
			Pre-hospital delays associated with 12-lead acquisition	Minimal delays 1-3 mins
Ioannidis JP et al, 2001, Boston	Chest pain patients requiring an ECG	Meta-analysis	Clinical effect of pre-hospital thrombolysis coupled with pre-hospital ECG	Time reduction approx 50 mins Mortality not affected Left ventricular ejection fraction - not affected	Wide variety of methodology and different end points Heterogeneity in study results not fully explored
Foster DB et al, 1994, USA	N = 155 Consecutive patients who had cardiac sounding chest pain over14 months	Prospective Cohort	Door to needle times	ECG 22 +/- 13.8 mins Controls 51 +/- 50 mins	Historical controls Small numbers
			On scene times	ECG 14 +/- 5.1 mins Controls 11.5 +/- 4.9 mins
Miller-Craig et al, 1997, UK	Phase I N = 124 Phase II N = 123 Patients suspected of having acute MI	Prospective Controlled Study	Interval durations for call to thrombolysis and door to needle times	Call to needle time control vs test 154 vs 93 mins Door to needle time control vs test 97 vs 37 mins	Controls and test patients done during different phases of study – not done concurrently Not randomized The Phase II patients bypass A&E Dept therefore physically shortening DTN times

Comment(s)

In the last few years, appointment of specialized chest pain nurses and use of bolus lytic agents has brought about significant reductions in door to needle times. 76% of patients currently have door to needle times of 30 minutes, but only 48% have 20 minutes or less. 45% have a call to needle time of 60 minutes or less (M.I.N.A.P 2003 figures). All studies except Canto et al showed a shortened pain interval.

Clinical Bottom Line

Pre hospital ECG significantly shortens door to needle times without prolonging the overall call to needle time in patients with acute myocardial infarction.

References

1. Karagounis L, Ipsen SK, Jessop MR et al. of field-transmitted electrocardiography on time to in-hospital thrombolytic therapy in acute myocardial infarction Am J Cardiol 1990;66:786–91.
2. Kareiakes DJ, Gibler WB, Martin LH et al. Relative importance of emergency medical system transport and the prehospital electrocardiogram on reducing hospital time delay to therapy for acute myocardial infarction: a preliminary report from th Am Heart J 1992;123:835-40.
3. Auderheide TP, Lawrence SW, Hall KN. Pre-hospital 12-lead ECG reduce hospital based time to treatment in thrombolytic candidates. Acad Emerg Med 1994;1:A13–A14.
4. Melville MR, Gravy D, Hinchley M et al. The potential impact of pre-hospital ECG and telemetry on time to thrombolysis in a United Kingdom centre. ANE 1998;3(4):327–333.
5. Canto JG, Rogers WJ, Bowlby LJ et al. The prehospital 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. Brown SG, Galloway DM. Effect of ambulance 12-lead ECG recording on times to hospital reperfusion in acute myocardial infarction Med J Aust 2000;172(2):81–84.
7. Ioannidis JP, Salem D, Chew PW, et al. Accuracy and clinical effect of out-of-hospital electrocardiography in the diagnosis of acute cardiac ischemia: a meta-analysis Ann Emerg Med 2000;37:461–470.
8. Foster DB, Dufendach JH, Barkdoll CM et al. 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.
9. Millar-Craig MW, Joy AV, Adamowicz M, et al. Reduction in treatment delay by paramedic ECG diagnosis of myocardial infarction with direct CCU admission Heart 1997;78:456–461.