Utility of observation units for young emergency department chest pain patients

The disutility of stress testing in low-risk HEART Pathway patients

BACKGROUND

The HEART Pathway identifies low-risk chest pain patients for discharge from the Emergency Department without stress testing. However, HEART Pathway recommendations are not always followed. The objective of this study is to determine the frequency and diagnostic yield of stress testing among low-risk patients.

METHODS

An academic hospital's chest pain registry was analyzed for low-risk HEART Pathway patients (HEAR score ≤ 3 with non-elevated troponins) from 1/2017 to 7/2018. Stress tests were reviewed for inducible ischemia. Diagnostic yield was defined as the rate of obstructive CAD among patients with positive stress testing. T-test or Fisher's exact test was used to test the univariate association of age, sex, race/ethnicity, and HEAR score with stress testing. Multivariate logistic regression was used to determine the association of age, sex, race/ethnicity, and HEAR score with stress testing.

RESULTS

There were 4743 HEART Pathway assessments, with 43.7% (2074/4743) being low-risk. Stress testing was performed on 4.1% (84/2074). Of the 84 low-risk patients who underwent testing, 8.3% (7/84) had non-diagnostic studies and 2.6% (2/84) had positive studies. Among the 2 patients with positive studies, angiography revealed that 1 had widely patent coronary arteries and the other had multivessel obstructive coronary artery disease, making the diagnostic yield of stress testing 1.2% (1/84). Each one-point increase in HEAR score (aOR 2.17, 95% CI 1.45-3.24) and being male (aOR 1.59, 95% CI 1.02-2.49) were associated with testing.

CONCLUSIONS

Stress testing among low-risk HEART Pathway patients was uncommon, low yield, and more likely in males and those with a higher HEAR score.

Guidelines for reasonable and appropriate care in the emergency department (GRACE): Recurrent, low-risk chest pain in the emergency department

This first Guideline for Reasonable and Appropriate Care in the Emergency Department (GRACE-1) from the Society for Academic Emergency Medicine is on the topic: Recurrent, Low-risk Chest Pain in the Emergency Department. The multidisciplinary guideline panel used The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the certainty of evidence and strength of recommendations regarding eight priority questions for adult patients with recurrent, low-risk chest pain and have derived the following evidence based recommendations: (1) for those >3 h chest pain duration we suggest a single, high-sensitivity troponin below a validated threshold to reasonably exclude acute coronary syndrome (ACS) within 30 days; (2) for those with a normal stress test within the previous 12 months, we do not recommend repeat routine stress testing as a means to decrease rates of major adverse cardiac events at 30 days; (3) insufficient evidence to recommend hospitalization (either standard inpatient admission or observation stay) versus discharge as a strategy to mitigate major adverse cardiac events within 30 days; (4) for those with non-obstructive (<50% stenosis) coronary artery disease (CAD) on prior angiography within 5 years, we suggest referral for expedited outpatient testing as warranted rather than admission for inpatient evaluation; (5) for those with no occlusive CAD (0% stenosis) on prior angiography within 5 years, we recommend referral for expedited outpatient testing as warranted rather than admission for inpatient evaluation; (6) for those with a prior coronary computed tomographic angiography within the past 2 years with no coronary stenosis, we suggest no further diagnostic testing other than a single, normal high-sensitivity troponin below a validated threshold to exclude ACS within that 2 year time frame; (7) we suggest the use of depression and anxiety screening tools as these might have an effect on healthcare use and return emergency department (ED) visits; and (8) we suggest referral for anxiety or depression management, as this might have an impact on healthcare use and return ED visits.

Pilot study of myocardial ischemia-induced metabolomic changes in emergency department patients undergoing stress testing

BACKGROUND

The heart is a metabolically active organ, and plasma acylcarnitines are associated with long-term risk for myocardial infarction. We hypothesized that myocardial ischemia from cardiac stress testing will produce dynamic changes in acylcarnitine and amino acid levels compared to levels seen in matched control patients with normal stress tests.

METHODS

We analyzed targeted metabolomic profiles in a pilot study of 20 case patients with inducible ischemia on stress testing from an existing prospectively collected repository of 357 consecutive patients presenting with symptoms of Acute Coronary Syndrome (ACS) in an Emergency Department (ED) observation unit between November 2012 and September 2014. We selected 20 controls matched on age, sex, and body-mass index (BMI). A peripheral blood sample was drawn <1 hour before stress testing and 2 hours after stress testing on each patient. We assayed 60 select acylcarnitines and amino acids by tandem mass spectrometry (MS/MS) using a Quattro Micro instrument (Waters Corporation, Milford, MA). Metabolite values were log transformed for skew. We then performed bivariable analysis for stress test outcome and both individual timepoint metabolite concentrations and stress-delta metabolite ratios (T2/T0). False discovery rates (FDR) were calculated for 60 metabolites while controlling for age, sex, and BMI. We built multivariable regularized linear models to predict stress test outcome from metabolomics data at times 0, 2 hours, and log ratio between these two. We used leave-one-out cross-validation to estimate the performance characteristics of the model.

RESULTS

Nine of our 20 case subjects were male. Cases' average age was 55.8, with an average BMI 29.5. Bivariable analysis identified 5 metabolites associated with positive stress tests (FDR < 0.2): alanine, C14:1-OH, C16:1, C18:2, C20:4. The multivariable regularized linear models built on T0 and T2 had Area Under the ROC Curve (AUC-ROC) between 0.5 and 0.55, however, the log(T2/T0) model yielded 0.625 AUC, with 65% sensitivity and 60% specificity. The top metabolites selected by the model were: Ala, Arg, C12-OH/C10-DC, C14:1-OH, C16:1, C18:2, C18:1, C20:4 and C18:1-DC.

CONCLUSIONS

Stress-delta metabolite analysis of patients undergoing stress testing is feasible. Future studies with a larger sample size are warranted.

Provocative biomarker stress test: stress-delta N-terminal pro-B type natriuretic peptide

Objective

Stress testing is commonly performed in emergency department (ED) patients with suspected acute coronary syndrome (ACS). We hypothesised that changes in N-terminal pro-B type natriuretic peptide (NT-proBNP) concentrations from baseline to post-stress testing (stress-delta values) differentiate patients with ischaemic stress tests from controls.

Methods

We prospectively enrolled 320 adult patients with suspected ACS in an ED-based observation unit who were undergoing exercise stress echocardiography. We measured plasma NT-proBNP concentrations at baseline and at 2 and 4  hours post-stress and compared stress-delta NT-proBNP between patients with abnormal stress tests versus controls using non-parametric statistics (Wilcoxon test) due to skew. We calculated the diagnostic test characteristics of stress-delta NT-proBNP for myocardial ischaemia on imaging.

Results

Among 320 participants, the median age was 51 (IQR 44-59) years, 147 (45.9%) were men, and 122 (38.1%) were African-American. Twenty-six (8.1%) had myocardial ischaemia. Static and stress-deltas NT-proBNP differed at all time points between groups. The median stress-deltas at 2  hours were 10.4 (IQR 6.0-51.7) ng/L vs 1.7 (IQR -0.4 to 8.7) ng/L, and at 4  hours were 14.8 (IQR 5.0-22.3) ng/L vs 1.0 (-2.0 to 10.3) ng/L for patients with ischaemia versus those without. Areas under the receiver operating curves were 0.716 and 0.719 for 2-hour and 4-hour stress-deltas, respectively. After adjusting for baseline NT-proBNP levels, the 4-hour stress-delta NT-proBNP remained significantly different between the groups (p=0.009).

Conclusion

Among patients with ischaemic stress tests, static and 4-hour stress-delta NT-proBNP values were significantly higher. Further study is needed to determine if stress-delta NT-proBNP is a useful adjunct to stress testing.

The (Dis) Utility of a Change in Troponin I for Diagnosis of Non-ST-Segment Elevation Myocardial Infarction in an Observation Unit

BACKGROUND

Observation units (OUs) may be an efficient and effective setting to diagnose and risk stratify patients with coronary ischemia and myocardial infarction (MI). Given improved cardiac troponin I (cTnI) assays and expanded utilization of OUs, it is not uncommon for patients with mildly elevated cTnI to be evaluated in OUs. We investigated the serial cTnI results in OU patients to determine whether absolute or relative cTnI changes were useful for the diagnosis of MI.

METHODS

This was a retrospective study of 260 patients placed in the OU from a single center in 2007, with an initial cTnI in the indeterminate range of 0.04-0.2 ng/ml (Siemens ultrasensitive), and a second cTnI was drawn at 6 hours. The diagnosis of MI was determined based on the third universal definition of MI by consensus review of 2 cardiologists, with adjudication by a third cardiologist in case of disagreement.

RESULTS

Of the 260 patients, 25 (9.6%) were determined to have MI at OU presentation. The optimal absolute and relative change in cTnI for MI diagnosis by receiver operating characteristic curve analysis were 0.02 ng/ml and 40%, respectively. There was initial cardiologist disagreement in 60% (15/25) of MI cases despite full review of serial cTnI and cardiac testing results. At 30 days, there were 3 adverse events: 2 deaths and 1 MI.

CONCLUSIONS

The diagnosis of MI in OU with low-level cTnI elevation is problematic. Furthermore, there is only marginal diagnostic utility of serial changes in cTnI in this patient population.

Diagnostic Yield of Routine Stress Testing in Low and Intermediate Risk Chest Pain Patients Under 40 Years: A Systematic Review

OBJECTIVE

Chest pain is one of the most frequent causes for presentation to emergency departments (EDs). The majority of patients will undergo diagnostic workup including stress testing to rule out an acute coronary syndrome, but very few patients will be diagnosed with a cardiac cause for their pain. Patients under 40 years represent a lower risk group in which routine stress testing may be of little benefit. This systematic review sought to determine the diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years.

METHODS

Electronic databases were searched for relevant studies. The quality of the included primary studies was assessed using the National Health and Medical Research Council evidence hierarchy and the McMaster Critical Appraisal Tool for Quantitative Studies. Descriptive statistics summarized the findings.

RESULTS

Five primary studies were included in the review (all level III-3 evidence); 7 additional sources of relevant data were also included. Diagnostic yield of routine stress testing in low- and intermediate-risk patients under 40 years is reported between 0% and 1.1%. Combined data from included primary studies demonstrated just 4 out of 1683 true positive stress tests (0.24%), only one of which was definitively confirmed by coronary angiogram; additional data sources identified just 1 out of 310 true positive stress tests (0.32%).

CONCLUSIONS

Diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years is low. However, better quality studies are required to be able to draw definitive conclusions.

The incremental value of stress testing in patients with acute chest pain beyond serial cardiac troponin testing

OBJECTIVE

In patients with acute chest pain and normal range cardiac troponin (cTn), accurate risk stratification for acute coronary syndrome is challenging. This study assesses the incremental value of stress testing to identify patients for angiography with a view to revascularisation.

METHODS

A single-centre observational study recruited patients with acute chest pain in whom serial cTn tests were negative and stress testing (exercise tolerance testing/dobutamine stress echocardiography) was performed. Stress tests were reported as negative, non-diagnostic or positive. The primary outcomes were revascularisation on index admission, or cardiac death and myocardial infarction over 1 year follow-up.

RESULTS

Of 749 patients recruited, 709 underwent exercise tolerance testing and 40 dobutamine stress echo of which 548 (73.2%) were negative, 169 (22.6%) were non-diagnostic and 32 (4.3%) were positive. Patients with positive tests (n=19 (59.4%)) were more likely to undergo index admission revascularisation than patients with non-diagnostic (n=15 (8.9%)) (p<0.001) tests who in turn were more likely undergo index admission revascularisation than those with negative tests (n=2 (0.4%)) (p<0.001). The risks of adverse events including cardiovascular death/acute myocardial infarction were low and were similar across stress test outcomes.

CONCLUSIONS

The incremental value of stress testing was the identification of an additional 34 (4.5% (95% CI 3.0% to 6.0%)) patients who underwent index admission revascularisation with a view to preventing future adverse events. Uncertainty in whether revascularisation prevents adverse events in patients with negative cTn means the choice to undertake stress testing depends on whether clinicians perceive value in identifying 4.5% of these patients for revascularisation.

CLINICAL TRIAL REGISTRATIONS

ACTRN1260900028327, ACTRN12611001069943.

False-positive rates of provocative cardiac testing in chest pain patients admitted to an emergency department observation unit

Emergency department observation units (EDOUs) typically perform routine cardiac stress testing or coronary computed tomography (CCTA) to rule out ischemic cardiac chest pain. Some have questioned the utility of routine stress testing and advanced anatomic imaging in the low-risk chest pain patients. EDOU chest pain patients undergoing stress testing or CCTA prior to cardiac catheterization between June 1, 2009 and May 31, 2012 were studied in a prospective, observational manner. Baseline data, EDOU-related outcomes, and testing results were recorded. Stress tests were treadmill echocardiogram or myocardial perfusion stress tests and were considered positive if a "positive" or "equivocal" interpretation by the reviewing cardiologist prompted cardiac catheterization. CCTA was considered positive if it led to subsequent cardiac catheterization. Cardiac catheterization was considered positive if subsequent stent placement, coronary artery bypass graft (CABG), or change in medical management occurred. Of 1276 patients evaluated, 112 (8.8%) underwent cardiac catheterization of which 56 underwent some modality of prior testing. Forty-two of 56 were subject to stress testing (30 stress echo and 12 myocardial perfusion) and 14 underwent CCTA prior to catheterization. False-positive rate overall was 62.5% (35/56, 95% CI, 48.5%-74.7%). False-positive rate for stress testing was 75% and 66.7% for perfusion and stress echo respectively. False-positive rate for CCTA was 42.9%. It must be acknowledged that while these findings do not directly impugn the utility of stress testing or CCTA, it may indicate the need for more appropriate patient selection to avoid unnecessary cardiac catheterization among EDOU chest pain patient cohorts.

Low-risk chest pain patients younger than 40 years do not benefit from admission and stress testing

BACKGROUND

A number of studies have suggested clinical decision rules for patients age <40 who are at low risk for acute coronary syndrome (ACS) and may be safe for discharge from the emergency department. Despite this, many such patients continue to be admitted for observation in low-risk observation units. We hypothesized that patients age <40 without coronary artery disease, with a nonischemic electrocardiogram (ECG), and normal initial troponin I (TnI) who are admitted to a CPU are at very low risk (<1%) for ACS or 30-day major adverse cardiac event (MACE) and would not benefit from observation care.

METHODS

This was a prospective, observational study of consecutive patients admitted to the CPU in a large-volume academic urban emergency department. Eligibility criteria included age >18 but <40, American Heart Association low-to-intermediate risk, nonischemic ECGs, and normal initial TnI. Standard descriptive statistics were used for demographics, cardiac comorbidities, and risk scores. Our primary outcomes were CPU ACS rate and 30-day MACE. MACE was defined as death, nonfatal AMI, revascularization, or out of hospital cardiac arrest. A sample size of at least 400 was chosen to have 1% precision about an expected outcome rate of 0.3% (based on prior CPU data of patients of all ages). Confidence intervals (CIs) were calculated using the refined Wilson simple asymptotic method with continuity correction. All patients were called at 30 days. All charts on index visit and any subsequent visit within 30 days were reviewed using standardized chart abstractions forms by 2 trained abstractors blinded to the hypothesis of the study. A Social Security Death Index search was performed on all patients.

RESULTS

Three hundred eighty-four patients accounting for 403 CPU admissions were enrolled over a 28-month period. Mean age was 34.3 ± 4.5; 42% were women; and 89%, 8%, 2%, and 1% had Thrombolysis in Myocardial Infarction scores of 0, 1, 2, and 3, respectively. No patient had an abnormal TnI. The ACS rate was 0 (95% CI, 0-0.8%). The 30-day MACE rate was 0 (95% CI, 0-0.8%). Forty-two percentage of these patients received stress testing but 0 (95% CI, 0-1.8%) were positive.

CONCLUSIONS

Patients age <40 with a normal ECG and normal first biomarker have <1% risk of ACS or 30-day MACE, such that admission and stress testing are of no benefit.