New methods for improved evaluation of patients with suspected acute coronary syndrome in the emergency department

Likelihood of acute coronary syndrome in emergency department chest pain patients varies with time of presentation

BACKGROUND

There is a circadian and circaseptal (weekly) variation in the onset of acute coronary syndrome (ACS). The aim of this study was to elucidate whether the likelihood of ACS among emergency department (ED) chest pain patients varies with the time of presentation.

METHODS

All patients presenting to the Lund ED at Skåne University Hospital with chest pain or discomfort during 2006 and 2007 were retrospectively included. Age, sex, arrival time at the ED and discharge diagnose (ACS or not) were obtained from the electronic medical records.

RESULTS

There was a clear but moderate circadian variation in the likelihood of ACS among presenting chest pain patients, the likelihood between 8 and 10 am being almost twice as high as between 6 and 8 pm. This was mainly explained by a variation in the ACS likelihood in females and patients under 65 years, with no significant variation in males and patients over 65 years. There was no significant circaseptal variation in the ACS likelihood.

CONCLUSIONS

Our results indicate that there is a circadian variation in the likelihood of ACS among ED chest pain patients, and suggest that physicians should consider the time of presentation to the ED when determining the likelihood of ACS.

Combination of copeptin and troponin assays to rapidly rule out non-ST elevation myocardial infarction in the emergency department

OBJECTIVES

The aim of this study was to analyze the diagnostic accuracy and the clinical usefulness of the combination of troponin I (cTnI) and copeptin measured at presentation with an automated assay to rapidly rule out non-ST elevation myocardial infarction (NSTEMI) in patients with suspected cardiac chest pain presenting to an emergency department (ED).

METHODS

This study was an ancillary analysis of a prospective observational study. Copeptin and cTnI levels were sampled at presentation in 641 consecutive patients admitted to the ED for chest pain with onset within the last 12 hours and without ST elevation on a 12-lead electrocardiogram (ECG). Copeptin was measured with an automated assay and troponin with conventional assay. The performance of a combination of cTnI and copeptin for NSTEMI diagnosis was studied, the clinical utility was assessed by multivariate analysis, and an area under the curve (AUC) calculation was used to determine accuracy.

RESULTS

NSTEMI was diagnosed in 95 patients (15%). The sensitivity and negative predictive value (NPV) of the combination of copeptin and cTnI measures were 90.4% (95% confidence interval [CI] = 88.2% to 92.7%) and 97.6% (95% CI = 96.4% to 98.7%) versus 55.3% (95% CI = 51.5% to 59.2%) and 92.8% (95% CI = 90.8% to 94.8%) with cTnI alone. The AUC of the combination of copeptin and cTnI was 0.89 (95% CI = 0.85% to 0.92%) and was significantly higher than the AUC of cTnI alone (0.77, 95% CI = 0.72% to 0.82%, p < 0.05). The patient classification was slightly improved when copeptin was added to the usual diagnostic tools used for NSTEMI management.

CONCLUSIONS

In this study, determination of copeptin, in addition to cTnI, improves early diagnostic accuracy of NSTEMI. However, the sensitivity of this combination even using a conventional troponin assay remains insufficient to safely rule out NSTEMI at the time of presentation.

Cardiac myosin binding protein-C is a potential diagnostic biomarker for myocardial infarction

Cardiac myosin binding protein-C (cMyBP-C) is a thick filament assembly protein that stabilizes sarcomeric structure and regulates cardiac function; however, the profile of cMyBP-C degradation after myocardial infarction (MI) is unknown. We hypothesized that cMyBP-C is sensitive to proteolysis and is specifically increased in the bloodstream post-MI in rats and humans. Under these circumstances, elevated levels of degraded cMyBP-C could be used as a diagnostic tool to confirm MI. To test this hypothesis, we first established that cMyBP-C dephosphorylation is directly associated with increased degradation of this myofilament protein, leading to its release in vitro. Using neonatal rat ventricular cardiomyocytes in vitro, we were able to correlate the induction of hypoxic stress with increased cMyBP-C dephosphorylation, degradation, and the specific release of N'-fragments. Next, to define the proteolytic pattern of cMyBP-C post-MI, the left anterior descending coronary artery was ligated in adult male rats. Degradation of cMyBP-C was confirmed by a reduction in total cMyBP-C and the presence of degradation products in the infarct tissue. Phosphorylation levels of cMyBP-C were greatly reduced in ischemic areas of the MI heart compared to non-ischemic regions and sham control hearts. Post-MI plasma samples from these rats, as well as humans, were assayed for cMyBP-C and its fragments by sandwich ELISA and immunoprecipitation analyses. Results showed significantly elevated levels of cMyBP-C in the plasma of all post-MI samples. Overall, this study suggests that cMyBP-C is an easily releasable myofilament protein that is dephosphorylated, degraded and released into the circulation post-MI. The presence of elevated levels of cMyBP-C in the blood provides a promising novel biomarker able to accurately rule in MI, thus aiding in the further assessment of ischemic heart disease.

A pilot study to develop a prediction instrument for endocarditis in injection drug users admitted with fever

OBJECTIVE

Seeking to evaluate the feasibility of a prediction instrument for endocarditis in febrile injection drug users (IDUs), we determined (1) the frequency percentage of IDUs admitted with fever diagnosed with endocarditis and (2) whether individual or combinations of emergency department (ED) clinical criteria (patient history, physical examination findings, and laboratory tests) are associated with endocarditis in IDUs admitted to rule out endocarditis.

METHODS

The ED and inpatient charts of all IDUs with a diagnosis of rule out endocarditis admitted at 3 urban hospitals in 2006 were reviewed. Screening performance of individual criteria was determined, and the most sensitive combination of criteria was derived by classification tree analysis.

RESULTS

Of 236 IDUs admitted with fever, 20 (8.5%) were diagnosed with endocarditis. Lack of skin infection, tachycardia, hyponatremia, pneumonia on chest radiograph, history of endocarditis, thrombocytopenia, and heart murmur had the best screening performance. The classification tree-derived best criteria combination of tachycardia, lack of skin infection, and cardiac murmur had a sensitivity of 100% (95% confidence interval, 84%-100%) and negative predictive value of 100% (95% confidence interval, 88%-100%).

CONCLUSIONS

Using ED clinical criteria, a multicenter prospective study to develop an instrument for endocarditis prediction in febrile IDUs is feasible, with an estimated target enrollment of 588 patients.

Negative predictive value and potential cost savings of acute nuclear myocardial perfusion imaging in low risk patients with suspected acute coronary syndrome: a prospective single blinded study

BACKGROUND

Previous studies from the USA have shown that acute nuclear myocardial perfusion imaging (MPI) in low risk emergency department (ED) patients with suspected acute coronary syndrome (ACS) can be of clinical value. The aim of this study was to evaluate the utility and hospital economics of acute MPI in Swedish ED patients with suspected ACS.

METHODS

We included 40 patients (mean age 55 +/- 2 years, 50% women) who were admitted from the ED at Lund University Hospital for chest pain suspicious of ACS, and who had a normal or non-ischemic ECG and no previous myocardial infarction. All patients underwent MPI from the ED, and the results were analyzed only after patient discharge. The current diagnostic practice of admitting the included patients for observation and further evaluation was compared to a theoretical "MPI strategy", where patients with a normal MPI test would have been discharged home from the ED.

RESULTS

Twenty-seven patients had normal MPI results, and none of them had ACS. MPI thus had a negative predictive value for ACS of 100%. With the MPI strategy, 2/3 of the patients would thus have been discharged from the ED, resulting in a reduction of total hospital cost by some 270 EUR and of bed occupancy by 0.8 days per investigated patient.

CONCLUSION

Our findings in a Swedish ED support the results of larger American trials that acute MPI has the potential to safely reduce the number of admissions and decrease overall costs for low-risk ED patients with suspected ACS.