Door-to-ECG time in patients with chest pain presenting to the ED

Door-to-ECG time in patients with chest pain presenting to the ED

American Journal of Emergency Medicine (2006) 24, 1 – 7
www.elsevier.com/locate/ajem
Original Contributions
Door-to-ECG time in patients with chest pain
presenting to the ED
Deborah B. Diercks MDa,*, J. Douglas Kirk MDa, Christopher J. Lindsell PhDb,c,
Charles V. Pollack Jr. MA, MDd, James W. Hoekstra MDe,
W. Brian Gibler MDb, Judd E. Hollander MDf
a
Division of Emergency Medicine, University of California, Davis Medical Center, Sacramento, CA 95817, USA
Department of Emergency Medicine, University of Cincinnati, Cincinnati, OH 45267, USA
c
Institute for Health Policy and Health Services Research, University of Cincinnati, Cincinnati, OH 45267, USA
d
Department of Emergency Medicine, Pennsylvania Hospital, Philadelphia, PA 19104, USA
e
Department of Emergency Medicine, Wake Forest University, Winston Salem, NC, USA
f
Department of Emergency Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA
b
Accepted 1 May 2005
Abstract
Objective: To describe time to electrocardiogram (ECG) acquisition, identify factors associated with
timely acquisition, and evaluate the influence of time to ECG on adverse clinical outcomes.
Methods: We measured the door-to-ECG time for emergency department patients enrolled in
prospective chest pain registry. Clinical outcomes were defined as occurrence of myocardial infarction
or death within 30 days of the visit.
Results: Among patients with acute coronary syndrome (ACS), 34% and 40.9% of patients with non–
ST-elevation ACS and ST-elevation myocardial infarction (STEMI), respectively, had an ECG
performed within 10 minutes of arrival. A delay in ECG acquisition was only associated with an
increase risk of clinical outcomes in patients with STEMI at 30 days (odds ratio, 3.95; 95% confidence
interval, 1.06-14.72; P = .04).
Conclusion: Approximately one third of patients with ACS received an ECG within 10 minutes. A
prolonged door-to-ECG time was associated with an increased risk of clinical outcomes only in patients
with STEMI.
D 2006 Elsevier Inc. All rights reserved.
1. Introduction
Presented at the Society of Academic Emergency Medicine annual
meeting, St. Louis MO, May 2002.
T Corresponding author. Tel.: +1 916 734 4052; fax: +1 916 734 7950.
E-mail address: [email protected] (D.B. Diercks).
0735-6757/$ – see front matter D 2006 Elsevier Inc. All rights reserved.
doi:10.1016/j.ajem.2005.05.016
Recent guidelines for the management of patients with
acute coronary syndrome (ACS) due to suspected unstable
angina (UA) or non–ST-elevation myocardial infarction
(NSTEMI; collectively, NSTE ACS) recommend that an
electrocardiogram (ECG) be obtained within 10 minutes of
arrival to the emergency department (ED) in patients with
2
ongoing chest pain and as soon as possible in all others [1].
This recommendation is based in part on previous reports that
show a benefit from rapid ECG acquisition in patients with
STEMI [2,3]. Studies in the STEMI population suggest that a
prolonged time to ECG acquisition is a significant factor in
delayed administration of thrombolytic therapy [3,4].
There are, however, no studies that support a defined doorto-ECG time in the NSTE ACS population. Although there is
little evidence that immediate recognition of the NSTE group
presents a clear prognostic advantage, it is logical that early
identification of these patients can facilitate appropriate and
timely management. Furthermore, there are recommendations that support early aggressive treatment in high-risk
patients with NSTE ACS, including early percutaneous
coronary intervention (PCI) and advanced antiplatelet therapy [1]. In addition to the limited knowledge about the value
of an early ECG in this group, it is also unclear whether this
recommendation can be practically implemented in most
institutions. The temporal impact of urgent and timely
pharmacological or mechanical interventions on adverse
clinical outcomes is still being investigated in this patient
population. Likewise, the diagnosis of STEMI or UA/
NSTEMI is largely based on a combination of ECG parameters and clinical history; therefore, early ECG acquisition
is relevant in all patients who present with chest pain consistent with a potential cardiac etiology. Therefore, examining
our current ECG acquisition practice, identifying factors that
influence ECG adherence, and exploring their relationship to
adverse clinical outcome are prudent in all populations who
present with chest pain.
This study describes our current performance in obtaining
an ECG within a 10-minute period and factors associated
with early acquisition. It also evaluates the occurrence of
adverse clinical outcomes in patients whose ECGs were
obtained beyond the recommended 10-minute interval.
2. Methods
This is a secondary analysis of prospectively collected
data. The subjects in this study were enrolled in the Internet
Tracking Registry for Acute Coronary Syndromes (i*trACS),
a registry of undifferentiated patients with chest pain
presenting to 8 geographically dispersed EDs in the United
States and Canada. All patients older than 24 years in whom
an ECG was obtained in the evaluation of potential anginal
symptoms were included. Patients with chest pain associated
with cocaine use have been excluded. Three categories
of patients were defined based upon final ED diagnoses:
(1) STEMI, (2) UA/NSTEMI, and (3) noncardiac chest pain.
All patients within these groups fall under national guidelines
that advocate obtaining an ECG within 10 minutes of
presentation. Not all of the 8 institutions had established
written policies or procedures that were consistent with these
guidelines. Institutional review board approval was obtained
at all institutions.
D.B. Diercks et al.
Final diagnoses were assigned on a prospective basis
using information available to the emergency physician at the
time of ED disposition. In this study, STEMI was defined
using World Health Organization criteria (ST elevation,
classic progression of ST-segment changes, and typical rise
and fall of creatinine kinase–MB in patients with symptoms
consistent with a myocardial infarction) and included patients
with a new left bundle-branch block (LBBB) [5]. A final
diagnosis of UA was defined as dynamic ECG changes
consistent with myocardial ischemia (ie, ST depression
N1 mm, transient ST elevation not meeting fibrinolytic criteria, or clinical history, in the absence of a positive cardiac
injury marker). Non–ST-elevation myocardial infarction was
defined as the occurrence of a cardiac marker (creatinine
kinase–MB, troponin I, or troponin T) that exceeded the
institutional threshold definition for myocardial infarction in
patients without ST elevation, but in a patient with clinical
ACS. Patients with chest pain without objective evidence of
cardiac ischemia or infarction and no other identifiable cause
were classified as noncardiac chest pain.
Patient demographics and information on clinical history
(including cardiac risk factors), physical examination, and
medications administered in the ED (aspirin, nitroglycerin,
b-blocker, heparin, and platelet glycoprotein IIb/IIIa inhibitors) were prospectively collected by trained evaluators at
the time of the initial visit or by review of the medical record.
History of coronary artery disease (CAD) was based on
patient self-report of myocardial infarction, PCI, or coronary
artery bypass graft. Confirmation of self-reported CAD was
obtained through medical record review when possible.
Follow-up was completed on all patients by telephone contact, review of the medical record, or social security death
registry review. Only clinical outcomes occurring within
30 days were considered.
Patients’ time of arrival and time of initial ECG
acquisition were extracted from the database. The exact
mode of transport was not collected in the registry. An acute
cardiac ischemia time-insensitive predictive instrument
(ACI-TIPI) score [6] was calculated using extracted data to
estimate the risk of coronary ischemia at the time of arrival,
although this information was not necessarily available to
clinicians in real time. The ACI-TIPI was computed using
the most recently available parameter estimates to weight the
influence of age, sex, chest pain characteristics, and ECG
findings on the probability of cardiac ischemia; the
computations were the same as those used in commercially
available equipment for computing the ACI-TIPI score.
Important adverse clinical outcomes in hospital or during
follow-up were defined as either death (all-cause) or
recurrent myocardial infarction.
The data were summarized using the median and interquartile range for continuous data and frequencies and
percentage for categorical data. Patient demographics (age,
race, sex, payor) are summarized for the first visit only to
prevent bias due to inclusion of multiple visits for some
patients. All other variables are summarized for all visits.
Door-to-ECG time in patients with chest pain
Table 1
3
Demographics, medical history, and visit information for the 3 patient groups included in this study
Median age (IQR)
Race (%)
White
African American
Other
Sex (%)
Male
Female
Insurer (%)
Private
Medicare/Medicaid
Self-pay
Other or unknown
Medical history (%) Diabetes
Hypercholesterolemia
Angina
CAD
CHF
Family history
of CAD
Time of visit (%)
8 am to 8 pm (day)
8 pm to 8 am (night)
ECG within 10 min (%)
Median ACI-TIPI score (IQR)
Median time to ECG in min (IQR)
Number of clinical outcomes (%)
Disposition (%)
Home
AMA
Admitted
Expired in ED
Median time in ED (5%ile-95%ile)
All
(Npatients = 7488)
(Nvisits = 8425)
STEMI
(npatients = 361)
(nvisits = 477)
53 (43-65)
3260 (44)
3091 (41)
1137 (15)
3354 (45)
4127 (55.)
2384 (32)
2051 (27)
854 (11)
2199 (29)
1701 (23)
1977 (26)
1178 (16)
2031 (27)
611 (8)
3261 (38)
63 (51-75)
181 (50)
109 (30)
71 (20)
223 (62)
136 (38)
88 (24)
114 (32)
39 (11)
120 (33)
139 (29)
114 (31)
74 (20)
139 (29)
67 (18)
173 (36)
6527 (78)
1898 (22.5)
2596 (30.8)
26 (13-37)
20 (8-52)
114 (1)
3224 (38)
136 (2)
5053 (60)
4 (0)
5.3 (3.7-7.4)
347 (73)
130 (27.3)
195 (40.9)
38 (24-59)
14 (5-38)
29 (6)
45 (10)
2 (0)
425 (90)
2 (0)
3.8 (2.0-6.0)
Differences between subject groups were tested using the
Kruskal-Wallis H test for continuous variables and v 2 tests for
categorical variables.
UA/NSTEMI
(npatients = 1035)
(nvisits = 1267)
Non-ACS
(npatients = 6092)
(nvisits = 6681)
P
62 (52-73)
585 (57)
330 (32)
120 (12)
543 (53)
492 (48)
312 (30)
384 (37)
91 (9)
248 (24)
363 (29)
474 (43)
382 (35)
610 (48)
106 (10)
552 (44)
51 (42-62)
2494 (41)
2652 (44)
946 (16)
2588 (42)
3499 (57)
1984 (33)
1553 (26)
724 (12)
1831 (30)
1199 (18)
1389 (33)
722 (17)
1282 (19)
438 (10)
2536 (38)
.085
b.001
961 (76)
306 (24)
428 (34)
32 (25-49)
17 (7-37)
25 (2)
22 (2)
23 (2)
1221 (96)
1 (0)
5.0 (3.5-7.1)
5219 (78)
1462 (22)
1973 (30)
24 (12-32)
21 (9-56)
60 (1)
3157 (47)
111 (2)
3407 (51)
1 (0)
5.4 (3.8-7.6)
b.001
b.001
b.001
b.001
b.001
b.001
b.001
.039
.008
b.001
b.001
.019
b.001
b.001
b.001
To determine which factors influenced whether or not a
patient received an ECG within a 10-minute period, logistic
regression was used to compare patient variables (or groups).
Table 2 Adjusted ORs and 95% CIs showing the relationship of patient demographics, medical history, and time of day on whether or
not an ECG was acquired within 10 minutes (the constant is not shown in the table)
Independent
Age
Male
African American
Other race
Medicare/Medicaid
Self-pay
Other or unknown
Diabetes
CAD
Hypercholesterolemia
Angina
CHF
Family history of CAD
Night
SBP N160 or SBP b90
HR N120
Reference
category
Female
White
Private
No history
Day
90 V HR V 160
HR V 120
STEMI
UA/NSTEMI
Non-ACS
OR
95% CI
P
OR
95% CI
P
OR
95% CI
P
1.00
1.08
0.35
1.07
0.91
2.39
2.34
1.19
1.21
1.62
1.27
0.98
0.73
0.95
0.94
0.70
0.98 -1.03
0.58 -2.01
0.18 - 0.67
0.44 -2.56
0.41-2.04
0.88- 6.50
1.04 - 5.29
0.67-2.09
0.68 -2.17
0.87-2.99
0.65 -2.48
0.45 -2.12
0.41-1.31
0.50 -1.80
0.51-1.73
0.14-3.41
.771
.820
.002
.887
.823
.088
.040
.558
.513
.127
.476
.954
.289
.875
.835
.662
1.01
1.18
1.20
1.43
0.85
0.71
1.04
0.96
1.31
1.17
1.07
1.20
0.94
1.10
0.81
1.17
1.00 -1.02
0.86 -1.62
0.86 -1.67
0.79 - 2.57
0.58 -1.25
0.39 -1.30
0.67-1.60
0.70 -1.32
0.95 -1.80
0.86 -1.60
0.77-1.47
0.74 -1.96
0.68 -1.29
0.77-1.58
0.58-1.12
0.44-3.10
.212
.302
.290
.236
.399
.270
.873
.801
.105
.321
.697
.454
.697
.603
.203
.758
1.01
1.24
0.83
1.38
0.83
0.90
1.27
1.04
1.28
0.90
1.03
1.05
1.02
1.13
0.91
1.22
1.00 -1.02
1.05 -1.46
0.70 -1.00
1.08 -1.78
0.67-1.03
0.66 -1.21
1.02 -1.57
0.87-1.24
1.07-1.53
0.76 -1.07
0.84 -1.27
0.80 -1.37
0.86 -1.20
0.94 -1.37
0.76-1.09
0.75-2.00
.011
.012
.047
.011
.097
.472
.030
.667
.008
.247
.768
.726
.842
.193
.287
.426
4
D.B. Diercks et al.
Fig. 1
Histogram showing the time to ECG for each of the patient groups.
Ten minutes was chosen as the standard, based on recent
recommendations for the management of UA/NSTEMI, and
therefore, time to ECG was entered as a dichotomous
variable [1]. For continuous covariates (eg, age, ACI-TIPI),
the change in the odds of receiving an ECG within 10
minutes for a unit increase in the variable value is calculated.
Logistic regression models were prespecified according to
the hypotheses. To determine if institution impacted the
results, initial models included this variable. To evaluate the
Table 3
relationship between time to ECG acquisition and the
occurrence of adverse clinical outcomes (all-cause death
and recurrent myocardial infarction), logistic regression
models were used with time to ECG as a predictor variable.
Results have been expressed as odds ratios (ORs) and 95%
confidence intervals (CIs) of the ORs. Significance levels are
indicated; P b .05 was prospectively set as the limit for
statistical significance. Analyses were performed using
SPSS for Windows v12.0 and SAS v8.0a.
Comparison of patients lost to follow-up and those with a follow-up completed
MI/LBBB
Age
ACI-TIPI
Female
Male
White
African American
Other
ECG within 10 min
History of diabetes
History of Hypercholesterolemia
History of angina
History of CAD
History of CHF
Family history of heart disease
UA/NSTEMI
CP-NOS
Lost to
follow-up
Follow-up
completed
Lost to
follow-up
Follow-up
completed
Lost to
follow-up
Follow-up
completed
63
37.9
174
237
202
132
79
170
122
101
62
121
60
156
64
34.6
21
29
29
12
9
21
13
10
9
16
6
14
61
31.6
513
576
601
382
107
368
308
423
319
525
89
468
61.5
31.6
62
68
64
35
31
47
42
39
41
63
14
66
51
24.0
3504
2543
2377
2742
933
1817
1086
1270
639
1151
404
2290
50
24.8
247
232
203
212
64
111
84
91
63
104
28
190
(51-75)
(24-59)
(42)
(58)
(49)
(32)
(19)
(41)
(30)
(32)
(20)
(29)
(19)
(57)
(54-77)
(23-57)
(42)
(58)
(58)
(24)
(18)
(42)
(26)
(25)
(23)
(32)
(15)
(39)
Values in bold italics are significantly different at the P b .05 level.
(51-72)
(25-49)
(47)
(53)
(55)
(35)
(10)
(34)
(28)
(45)
(34)
(48)
(9)
(59)
(53-72)
(24-52)
(48)
(52)
(49)
(27)
(24)
(36)
(32)
(35)
(37)
(49)
(13)
(70)
(42-63)
(12-32)
(60)
(42)
(39)
(45)
(15)
(30.)
(18)
(33)
(17)
(19)
(11)
(57)
(41-62)
(13-32)
(52)
(48)
(42)
(44)
(13)
(23)
(18)
(31)
(21)
(22)
(9)
(57)
Door-to-ECG time in patients with chest pain
3. Results
The study sample comprised 7887 patients who made a
total of 8885 visits to the ED between June 1, 1999, and
October 1, 2001. Patients without chest pain were excluded
from analyses (399 patients), leaving 7488 patients with
8425 visits. Overall, 575 patients visited the ED twice;
124 patients visited between 3 and 5 times; 7 patients between
5 and 10 times; and 3 patients visited the ED 10 or more times
over the 2-year period. Of the 8425 patient visits, 477 (5.7%)
had STEMI; 1267 (15%) met the criteria for UA/NSTEMI
(1121 UA and 146 NSTEMI); and 6681 (79.3%) were
classified as noncardiac chest pain. The patient groups are
described in Table 1. All predictor variables are significantly
different between the 3 patient groups. Patients with the
diagnosis of STEMI and UA/NSTEMI were more likely to be
white (50.1% and 56.5% respectively), compared with the
noncardiac chest pain group (40.9%). There was a statistically significant difference in the time to ECG acquisition
between the specific institutions, but the institution was not
an independent predictor of clinical outcome after adjusting
for time to ECG, and it had no impact on identifying
predictors of ECG acquisition. At academic centers,
the median time to ECG was 22 minutes, whereas the
median time to ECG in the community-based hospital was
12.5 minutes. Complete 30-day follow-up was available in
91.5% of all patients (Table 2).
The median time to ECG acquisition was significantly
different among the 3 groups. For patients with STEMI, the
median time to ECG was 14 minutes. Time to ECG was
17 minutes for the UA/NSTEMI group and 21 minutes for
those with noncardiac chest pain. Most patients had an ECG
within 30 minutes. There was also a significant difference
between groups in the percentage of patients receiving an
ECG within 10 minutes: 40.9% for the STEMI group, 33.8%
for UA/NSTEMI, and 29.5% for those with noncardiac chest
pain (Table 1). Most patients had an ECG within 30 minutes
(Fig. 1). Determinants associated in logistic regression
analysis with whether or not a patient had an ECG performed
within the 10-minute time frame are shown in Table 3. For
patients with a final diagnosis of UA/NSTEMI, there were
no independent predictors of early ECG acquisition. For
the group of patients with STEMI, African American race
(0.35; 95% CI, 0.18-0.67; P = .002) and unknown insurance
status (OR, 2.34; 95% CI, 1.04-5.29; P = .04) were associated
with a delayed ECG. For patients with noncardiac chest pain,
predictors of delayed ECG were younger age, female sex,
African American race, uninsured, and no history of CAD.
The relationship between likelihood of ACS (quantified
using the ACI-TIPI score), time to ECG, and the occurrence
of an adverse clinical outcome within the 3 patient groups is
shown in Table 4. For patients with UA/NSTEMI and nonACS chest pain, time to ECG was not associated with
increased risk of adverse clinical outcome. In the STEMI
group, a door-to-ECG time greater than 10 minutes was
associated with increased risk of adverse clinical events
5
Table 4 Risk of the time to ECG on adverse clinical outcomes
(recurrent MI or death in or out of the hospital), corrected for
likelihood of ischemia by ACI-TIPI, occurrence of PCI, stent
placement or CABG, and treatment
Independent variable
STEMI
ECG N10 min
ACI-TIPI
Invasive therapy
Noninvasive treatments
History of diabetes
History of
hypercholesterolemia
History of angina
History of CAD
History of CHF
Family history
of heart disease
UA/NSTEMI
ECG N10 min
ACI-TIPI
Invasive therapyT
Noninvasive treatments
History of diabetes
History of
hypercholesterolemia
History of angina
History of CAD
History of CHF
Family history
of heart disease
CP-NOS
ECG N10 min
ACI-TIPI
Invasive therapy
Noninvasive treatments
History of diabetes
History of
hypercholesterolemia
History of angina
History of CAD
History of CHF
Family history
of heart disease
OR
95% CI
P
3.95
1.02
1.24
1.02
1.18
0.27
1.06 -14.72
0.99-1.05
0.32 - 4.77
0.10-10.07
0.33- 4.24
0.05-1.33
.040
.315
.753
.988
.801
.106
0.48
1.28
2.42
3.13
0.09-2.53
0.37- 4.41
0.52-11.24
0.77-12.76
.390
.691
.260
.112
1.13
1.03
0.40-3.17
1.00 -1.06
1.03
1.04
2.18
0.13-8.29
0.37-2.95
0.79- 6.05
.814
.023
.996
.977
.938
.133
0.60
0.39
2.59
1.75
0.19-1.85
0.13-1.16
0.78-8.58
0.59-5.16
.371
.090
.119
.309
1.36
1.01
7.77
0.56
0.78
0.63
0.68-2.72
0.99-1.03
3.01-20.10
0.25-1.23
0.36-1.69
0.29-1.39
.383
.198
.000
.149
.531
.254
0.67
1.10
3.68
1.15
0.25-1.78
0.53-2.28
1.71-7.96
0.58-2.28
.417
.789
.001
.686
T Because of small cell sizes, the parameters cannot be estimated.
(OR, 3.95; 95% CI, 1.06-14.72; P = .04). In the UA/NSTEMI
group, ACI-TIPI score increased the odds of an adverse
clinical outcome (OR, 1.03; 95% CI, 1.00-1.06; P = .023).
Further modeling shows that the relationship between the risk
of adverse events and door-to-ECG time is nonlinear. In the
UA/NSTEMI patient population, the proportion of patients
with an adverse event was relatively stable up to about
2 hours. After this time, the odds of an adverse event
increased significantly. If the ECG was delayed beyond
3 hours, the odds of an adverse event increased 7-fold. (Fig. 2)
When evaluating only patients who received an ECG
6
D.B. Diercks et al.
Fig. 2 Relationship between adverse events and door-to-ECG time for patients with UA or NSTEMI. For the ORs, the reference group is
the group with door-to-ECG time less than 5 minutes. Odds ratios are adjusted for disease severity, treatment, and history of CAD or diabetes.
within 2 hours, door-to-ECG time is of borderline statistical
significance in predicting adverse events (OR, 3.38; 95%,
CI 0.9-12.72; P = .07) among patients with STEMI.
4. Discussion
The National Heart Attack Alert Program demonstrated
that timely acquisition of an ECG is a critical time point (door,
data, decision, drug) in the management of patients with
STEMI who are undergoing fibrinolytic therapy [2]. Sagarin
et al [3] reported that a delay in ECG acquisition was
responsible for 25% of fibrinolytic treatment delays. Until
recently, however, this bdoor-to-dataQ time point has not been
emphasized in the patient with chest pain who does not have
STEMI. Recent guidelines, however, have recommended that
an ECG be obtained in all patients with suspected UA/
NSTEMI and ongoing chest pain within 10 minutes of
presentation and as soon as possible in all other patients [1].
This guideline was available at the development of this
registry, but in fact, early acquisition has been recognized as
an evaluation goal for all patients with chest pain for many
years. Recent improvements in treatment options for the
patient with UA/NSTEMI based on risk stratification,
including ischemic ECG changes, has resulted in an increased
urgency in identification of these patients. In addition, the
ultimate diagnosis of the undifferentiated patient with chest
pain is time dependent, and until an ECG has been performed,
the diagnosis of STEMI can not be excluded. This concept
supports the early acquisition of an ECG in all patients who
present to the ED with possible cardiac chest pain. Therefore,
this study examined the current practice in ECG acquisition,
identified factors that influenced adherence, and explored
their relationship to adverse clinical outcomes in all patients
who present to the ED.
The results of our study suggest that current ED practice of
obtaining an ECG falls short of the recommended guidelines
in all patients with chest pain. We found a median time of
14 minutes for door to data in patients with STEMI. This is
similar to the results reported by Jackson et al [7] in 1996,
who reported a median door-to-data time of 17 to 25 minutes
in patients who received fibrinolytic therapy for STEMI at
two institutions. Unlike patients with STEMI, patients with
UA/NSTEMI frequently do not have a diagnostic initial
ECG. The diagnosis is more often made by cardiac serum
markers, serial ECGs, or purely on clinical grounds, typically
after an extended evaluation. Despite the difficulty in separating this group of patients from the abundance of patients with
non-ACS chest pain at presentation, patients with a final
diagnosis of UA/NSTEMI had a median door-to-ECG time
of 17 minutes, compared with 21 minutes for patients with
noncardiac chest pain.
Prior studies have evaluated potential predictors of a delay
in acquisition of an ECG. Lambrew et al [4] reported that sex
and mode of transportation were factors affecting the time to
ECG in patients with STEMI. Soumerai et al [8] examined the
care provided to the elderly between health maintenance
organizations or fee-for-service insurance providers and
found no difference in time to ECG acquisition. Our findings
demonstrate that race and insurance status are predictors of
a timely ECG acquisition in patients with STEMI, but that
in patients with UA/NSTEMI, there were no independent
predictors of an ECG being performed within 10 minutes
of presentation.
Rapidly obtaining an ECG is intuitive in any patient with
possible coronary ischemia or infarction, and in many
institutions, it is part of triage policy and standard ED intake
procedure. However, our results suggest that although it may
be intuitive, it is not occurring. A broad-based protocol incorporating a triage ECG could help to correct this. Multiple
studies have shown that protocol-driven evaluation of patients with STEMI improves time to ECG and treatment
[9-12]. Graff et al [12] derived a triage ECG rule for a rapid
5-minute ECG based on chief complaint, age, and vital signs.
The use of this rule decreased the time to ECG from 10 to
6.3 minutes in patients with STEMI, suggesting that a
Door-to-ECG time in patients with chest pain
protocol-driven approach could correct the inadequate doorto-ECG times evidenced here, especially in the UA/NSTEMI
population [12].
We found that delayed ECG acquisition was predictive of
adverse events only in patients with STEMI, with a 3-fold
increase in risk for adverse events in those with an ECG over
10 minutes. This was not noted in patients with UA/NSTEMI
where only ACI-TIPI was associated with adverse events. We
found that this risk of delayed ECG was apparent predominantly above a 2-hour delay in the ECG. It is possible that an
atypical presentation of STEMI and UA/NSTEMI resulted in
delays in ECG acquisition, subsequently increasing the
possibility of adverse outcomes.
This study has several limitations. It is a retrospective
analysis of prospectively collected data. Additional data that
addressed impediments to ECG acquisition would have been
useful and would have provided additional clinical insight
into the challenges faced in the ED. For example, we can not
account for the physical appearance of patients that may have
led to an early ECG. This may have significantly factored into
the earlier acquisition in patients with STEMI. It should be
noted that we did not account for variability in institutional
policies and protocols, although we feel the multicenter format is a strength of this study and improves the generalizability of the results. We also were unable to account for ED
overcrowding as a factor that can delay ECG acquisition.
Another limitation is the possibility that there may be a
discrepancy between the clocks in the ECG machines and ED
clocks. This could affect the number of patients having an
ECG performed within 10 minutes. We did not account for
other comorbidities that may affect ECG acquisition time as
well adverse clinical outcome. In addition, we are not able to
account for the mode of transportation on door-to-ECG time.
Because of the retrospective nature of our study, we could not
determine which patients had active pain at the time of
presentation or recurrent pain during the visit or those patients
with atypical presentation that can lead to delayed ECG
acquisition. Including patients with a new LBBB in the
STEMI group may have resulted in misclassification of
lower-risk patients in this group. This explains why 45 patients were discharged home from the ED with a diagnosis of
STEMI. Lastly, because we used ED discharge diagnosis to
group patients, we may have had classification error in the
patients initially identified as noncardiac chest pain who later
were diagnosed with having a myocardial infarction based on
subsequent laboratory testing.
In summary, our study shows that some EDs are not
meeting the goal for ECG acquisition in patients with UA/
NSTEMI and STEMI and suggests that this may affect
adverse clinical outcomes. There appears to be no consistent
7
predictor of delayed ECG acquisition across all patient
categories studied. Recognition of factors that we found
to influence time-to-ECG may help others improve performance. However, improving door-to-ECG time may be
dependent upon changing triage criteria and ECG acquisition
protocols. This should be followed by further studies to
demonstrate if these strategies are effective in changing
practice and improving clinical outcome.
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