Keywords
acute coronary syndrome - echocardiography - electrocardiogram - focused cardiac ultrasound
- regional wall motion abnormalities
Introduction
Acute coronary syndrome (ACS) is a major cardiovascular disease with high morbidity
and mortality worldwide.[1]
[2] Early diagnosis of ACS is critical in implementing effective treatment strategies
and improving patient outcomes. In this context, additional diagnostic tools are needed
to assist emergency physicians in diagnosing ACS, particularly in cases where standard
electrocardiogram (ECG) findings are equivocal.[3]
Focused cardiac ultrasound (FOCUS) has become increasingly accepted as a tool in emergency
medicine.[3]
[4]
[5] FOCUS is a noninvasive imaging modality that can be used quickly and effectively
in the emergency department. Specifically, it may be useful in the detection of left
ventricular (LV) regional wall motion abnormalities (RWMA), particularly in acute
myocardial infarction.[6]
[7] However, the sensitivity and specificity of FOCUS in detecting RWMA can vary between
emergency physicians with different levels of training and experience. This variation
may be a significant factor in the effectiveness and reliability of FOCUS use in the
emergency department.
The primary objective of this study was to evaluate the accuracy, sensitivity, and
specificity of FOCUS in detecting RWMA compared with standard echocardiography (ECHO).
The assessment by the emergency physician performing FOCUS was considered positive
if abnormal motion was detected in at least one wall of the LV and if these findings
were consistent with the results of standard ECHO performed by a cardiologist or with
specific anatomical site occlusions identified during cardiac catheterization. Standard
ECHO is defined as ECHO performed directly by a cardiologist or a cardiology fellow
under the supervision of a cardiologist. Secondary endpoints include determining the
sensitivity of FOCUS in detecting RWMA in patients with obstructive myocardial infarction
(OMI) confirmed by cardiac catheterization and assessing the sensitivity of cardiac
FOCUS in detecting RWMA in patients without OMI.
Materials and Methods
Design and Settings
This prospective observational study included 91 patients who presented to the emergency
department with suspected ACS within a specified time frame. The study was conducted
at the Emergency Department of Antalya Training and Research Hospital between June
1, 2023, and November 30, 2023. The Ethics Committee of Antalya Training and Research
Hospital approved the study, and all patients gave written informed consent before
participating.
Inclusion criteria were patients aged 18 years and older with suspected ACS who underwent
FOCUS in the emergency department. Exclusion criteria were patients with ST-segment
elevation on the ECG, patients who did not underwent percutaneous coronary intervention
within 72 hours, patients without records, patients for whom FOCUS cannot be performed,
and conditions unsuitable for FOCUS (e.g., severe respiratory failure).
FOCUS Application
Senior emergency physicians performed FOCUS examinations. It was performed by an emergency
assistant or specialist who works in the emergency department, has at least 2 years
of experience in ultrasonography (USG), and has basic USG and advanced USG certificates.
These doctors had different levels of expertise in performing FOCUS scans. They assessed
the presence of RWMA in each patient's LV.
Study Protocol and Data Collection
This study evaluated patients with suspected ACS based on ECG findings and clinical
features in our emergency department. Patients who met the criteria for ST-segment
elevation myocardial infarction (STEMI) on ECG were consulted with a cardiology specialist
and referred for coronary angiography (CA) without undergoing FOCUS.
Patients presenting with symptoms of ACS and suspected of having an OMI based on ECG
changes but not meeting STEMI criteria were assessed with FOCUS by the emergency physician
and with standard ECHO by a cardiologist. The emergency physicians recorded the FOCUS
data without reviewing the standard ECHO findings.
Data extracted from the hospital information system included the presence or absence
of RWMA on FOCUS or subsequent formal ECHO, cardiac catheterization results (if performed),
patient status, and survival. Data collectors remained blinded to outcome data.
Senior emergency physicians performed FOCUS examinations. It was performed by an emergency
assistant or specialist who works in the emergency department, has at least 2 years
of experience in USG, and has basic USG and advanced USG certificates. Physicians
participating in the study were experienced in defining RWMA and had previously received
training in certification programs. The LV walls were simplified as anterior, inferior,
lateral, and posterior. Formal ECHO used 17-segment guidelines, while FOCUS was performed
with parasternal long, parasternal short, apical four-chamber, and apical two-chamber
views. RWMA was considered positive if abnormalities were detected in one or more
regions. We did not assess the specific regions of wall motion abnormalities or the
exact location of the abnormalities.
Patient demographics, presenting symptoms, ECG results, and FOCUS findings were recorded
on admission. Each RWMA identified during FOCUS was documented for each patient. ECHO
and CA results performed by cardiologists were recorded by reviewing hospital system
reports.
Statistical Analysis
Descriptive statistics were used to summarize the data. Categorical variables were
presented as numbers and percentages, while continuous variables were summarized using
means and standard deviations and medians and interquartile ranges. Sensitivity, specificity,
positive predictive value (PPV), negative predictive value (NPV), and their 95% confidence
intervals (95% CIs) were calculated using binary categorical tables. Statistical analysis
was performed with SPSS version 29.
Result
Between June 1, 2023 and November 30, 2023, 91 patients considered at high risk of
ACS were enrolled in the study. All 91 patients underwent FOCUS procedures in the
emergency department. The presence or absence of RWMA was recorded for all 91 patients.
All 91 patients were included in the study for comparison with formal ECHO. The mean
age was 58, and 32% of patients were female. Additional patient characteristics are
shown in [Table 1].
Table 1
Demographic and clinical characteristics of the patients
|
Characteristics
|
Data[a]
|
|
Gender
|
Female
|
29 (32%)
|
|
Male
|
62 (65%)
|
|
Age (y)
|
Mean (SD)
|
58.5 (8.5)
|
|
Median (IQR)
|
58 (52–65)
|
|
History
|
Diabetes
|
23 (25%)
|
|
Hypertension
|
39 (43%)
|
|
Hyperlipidemia
|
24 (26%)
|
|
Congestive heart failure
|
18 (20%)
|
|
Coronary artery disease
|
44 (48%)
|
|
Door-FOCUS time (min)
|
Mean (SD)
|
20.6 (8.5)
|
|
Median (IQR)
|
20 (15–25)
|
|
Door-ECHO time (min)
|
Mean (SD)
|
127.5 (23)
|
|
Median (IQR)
|
120 (120–140)
|
|
PCI
|
OMI +
|
59 (65%)
|
|
OMI –
|
32 (35%)
|
Abbreviations: ECHO, echocardiography; FOCUS, focused cardiac ultrasound; IQR, interquartile
range; OMI, obstructive myocardial infarction; PCI, percutaneous coronary intervention;
SD, standard deviation.
a Data are frequency (%) unless otherwise specified.
Compared with the criterion standard of formal ECHO, the sensitivity of FOCUS performed
by emergency physicians for detecting RWMA was 85% sensitivity (95% CI, 73–92), the
specificity was 53% (95% CI, 36–69), PPV was 77 (95% CI, 65–85), NPV was 65 (95% CI,
46–81), and the overall accuracy was 74% (95% CI, 64–82).
All 91 patients underwent either emergency or nonemergency CA, and 65% were diagnosed
with OMI on CA. FOCUS, performed by emergency physicians, detected RWMA in 85% of
patients with OMI, confirmed by CA ([Table 2]).
Table 2
Comparison of FOCUS and PCI results
|
PCI
|
|
Acute OMI
absent
|
Acute OMI
positive
|
|
FOCUS
|
RWMA +
|
17 (53%)
|
9 (15%)
|
|
RWMA –
|
15 (47%)
|
50(85%)
|
Abbreviations: FOCUS, focused cardiac ultrasound; OMI, obstructive myocardial infarction;
PCI, percutaneous coronary intervention; RWMA, regional wall motion abnormalities.
Discussions
Our study, a high-risk cohort of patients with high suspicion of ACS, demonstrated
that FOCUS used by emergency physicians accurately identified RWMA in a cohort undergoing
high-risk emergency cardiac catheterization. Notably, these findings were more definitive
in patients with OMI identified by cardiac catheterization. These data suggest that
the presence of RWMA in a patient with a high suspicion of ACS based on history, physical
examination, and ECG further increases the suspicion of OMI. However, the absence
of RWMA does not decrease the likelihood of OMI. These findings, together with other
studies, suggest that using FOCUS in cases of OMI without meeting STEMI criteria in
the emergency setting may benefit patients.[6]
[7]
[8] In such scenarios, activating the emergency catheterization laboratory requires
diagnostic tests beyond the ECG (e.g., serum troponin levels, ongoing ischemic symptoms,
etc.).[9] Therefore, the presence of RWMA in a cardiac region consistent with the ECG, even
if not meeting STEMI criteria, may be sufficient to activate the emergency catheterization
laboratory. However, further studies are needed.
Our study was conducted in patients undergoing emergency cardiological assessment
and urgent reperfusion. This reflects clinical practice (e.g., limited time for FOCUS,
difficult patient positioning due to noncooperation, etc.). Although this may have
affected the quality of the FOCUS results to a lesser or suboptimal extent, it made
the results more generalizable and reflective of the current clinical environment.
Given the different conditions that can cause RWMA in the absence of ACS, our study
practically investigated RWMA in cases of OMI confirmed by cardiac catheterization,
which is ultimately the cohort that emergency physicians aim to identify. Another
strength of our study was the inclusion of patients at high risk of ACS despite not
meeting STEMI criteria.[10-13] Using ultrasound in this population is important for emergency physicians and cardiology
teams in equivocal ECG situations and may aid in diagnosing OMI. This cohort of patients
represents a target group where delays to cardiac catheterization in current algorithms
for the management of ACSs may lead to increased mortality. Future studies should
investigate the performance characteristics of FOCUS performed by emergency physicians
in cases of non-STEMI but suspected OMI.[14] In such studies, those with STEMI on their ECG may be excluded due to door-to-balloon
time metrics and, in some cases, direct admission to the catheterization laboratory,
bypassing the emergency department entirely or rapidly.
Our study has several limitations. The limited use of FOCUS in many cases may further
limit its validity. A larger prospective study is needed to explore this issue further.
In addition, the emergency physicians performing FOCUS needed to be briefed on the
clinical information, particularly the ECG. This could lead to observer bias, particularly
in reporting regional wall involvement. However, this reflects current clinical practice,
where presentation and ancillary investigations are performed concurrently. Our important
limitation is that ECHOs performed by cardiology are performed by only one physician,
even if an expert or experienced person performs them. Another limitation is that
we should have specifically assessed the volume of FOCUS examinations performed by
our emergency physicians before they participated in this study. Clinicians with more
experience and comfort with FOCUS are more likely to perform and document ultrasound
more frequently, potentially reducing the generalizability of the study. In addition,
certain patient groups, such as obese individuals, those with chest wall abnormalities,
or those with positioning difficulties, may have been underrepresented or not included
in the study, potentially biased the data.
Similarly, image acquisition and interpretation are two different skills. If the clinician
performing FOCUS cannot obtain high-quality images, interpretation may be compromised.
In addition, this patient population may not be generalizable to patients with underlying
cardiac disease. Such patients (e.g., structural heart disease, conduction abnormalities,
etc.) may have abnormal wall motion defects, further limiting the usefulness of FOCUS
in diagnosing OMI. Finally, this study includes a population at high risk for acute
coronary occlusion. All patients in this study underwent cardiac catheterization,
and high rates of OMI were observed during cardiac catheterization. Therefore, these
results may not be generalizable to patients with low to moderate ACS risk.
Conclusion
Our study demonstrates the potential utility of FOCUS performed by emergency physicians
in detecting RWMA in patients with high suspicion of ACS. This may be particularly
beneficial in cases where the ECG is inconclusive, but the clinician maintains a high
suspicion for OMI and in patients without STEMI on ECG. The presence of RWMA in such
cases may lead to earlier activation of the emergency catheterization laboratory,
but this requires further investigation. While the presence of RWMA may help to identify
OMI, its absence should not rule it out. Further research is required to validate
these findings.
