Clinical utility of troponin T levels and echocardiography in the emergency department

The diagnostic accuracy of cardiac ultrasound for acute myocardial ischemia in the emergency department: a systematic review and meta-analysis

BACKGROUND

Chest pain is responsible for millions of visits to the emergency department (ED) annually. Cardiac ultrasound can detect ischemic changes, but varying accuracy estimates have been reported in previous studies. We synthetized the available evidence to yield more precise estimates of the accuracy of cardiac ultrasound for acute myocardial ischemia in patients with chest pain in the ED and to assess the effect of different clinical characteristics on test accuracy.

METHODS

A systematic search for studies assessing the diagnostic accuracy of cardiac ultrasound for myocardial ischemia in the ED was conducted in MEDLINE, EMBASE, CENTRAL, CINAHL, LILACS, Web of Science, two trial registries and supplementary methods, from inception to December 6th, 2022. Prospective cohort, cross-sectional, case-control studies and randomized controlled trials (RCTs) that included data on diagnostic accuracy were included. Risk of bias was assessed with the QUADAS-2 tool and a bivariate hierarchical model was used for meta-analysis with paired Forest and SROC plots used to present the results. Subgroup analyses was conducted on clinically relevant factors.

RESULTS

Twenty-nine studies were included, with 5043 patients. The overall summary sensitivity was 79.3% (95%CI 69.0-86.8%) and specificity was 87.3% (95%CI 79.9-92.2%), with substantial heterogeneity. Subgroup analyses showed increased sensitivity in studies where ultrasound was conducted at ED admission and increased specificity in studies that excluded patients with previous heart disease, when the target condition was acute coronary syndrome, or when final chart review was used as the reference standard. There was very low certainty in the results based on serious risk of bias and indirectness in most studies.

CONCLUSIONS

Cardiac ultrasound may have a potential role in the diagnostic pathway of myocardial ischemia in the ED; however, a pooled accuracy must be interpreted cautiously given substantial heterogeneity and that important patient and test characteristics affect its diagnostic performance.

PROTOCOL REGISTRATION

PROSPERO (CRD42023392058).

Scoping review of echocardiographic parameters associated with diagnosis and prognosis after resuscitated sudden cardiac arrest

AIM

Current international guidelines recommend early echocardiography after resuscitated sudden death despite limited data. Our aim was to analyze published data on early post-resuscitation echocardiography to identify cardiac causes of sudden death and prognostic implications.

METHODS

We reviewed MEDLINE, EMBASE, and CENTRAL databases to December 2021 for echocardiographic studies of adult patients after resuscitation from non-traumatic sudden death. Studies were included if echocardiography was performed <48 hours after resuscitation and reported (1) diagnostic accuracy to detect cardiac etiologies of sudden death or (2) prognostic outcomes. Diagnostic endpoints were associations of regional wall motion abnormalities (RWMA), ventricular function, and structural abnormalities with cardiac etiologies of arrest. Prognostic endpoints were associations of echocardiographic findings with survival to hospital discharge and favorable neurological outcome.

RESULTS

Of 2877 articles screened, 16 (0.6%) studies met inclusion criteria, comprising 2035 patients. Two of six studies formally reported diagnostic accuracy for echocardiography identifying cardiac etiology of arrest; RWMA (in 5 of 6 studies) were associated with presumed cardiac ischemia in 17-89% of cases. Among 12 prognostic studies, there was no association of reduced left ventricular ejection fraction with hospital survival (v10) or favorable neurologic status (n = 5). Echocardiographic high mitral E/e' ratio (n = 1) and right ventricular systolic dysfunction (n = 2) were associated with poor survival.

CONCLUSION

This scoping review highlights the limited data on early echocardiography in providing etiology of arrest and prognostic information after resuscitated sudden death. Further research is needed to refine the clinical application of early echocardiographic findings in post arrest care.

Echocardiography in Detecting Mechanical Complications in Acute Coronary Syndrome

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ACS encompasses a wide variety of complex symptoms and presentations.

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The use of echocardiography in ACS assists in early clinical decision-making.

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Echocardiography can aid in detecting early and late mechanical complications of ACS.

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Early detection of complications of ACS on echocardiography can improve outcomes.

Feasibility and Reliability of Rapid Diagnosis of Myocardial Infarction

BACKGROUND

Prevailing hospital practice dictates a protracted phase of observation for patients with chest pain to establish or exclude the diagnosis of myocardial infarction. Early diagnosis of acute myocardial infarction may improve patient care and reduce both complications and hospital costs. A study was performed to investigate the feasibility of early diagnosis of myocardial infarction within the first 9 hours of the hospital stay.

METHODS

The records of all patients admitted with chest pain within one calendar year were analyzed. The timing of creatine kinase-MB (CK-MB) quantification was determined with reference to the initial phlebotomy (time 0). An enzymatic diagnosis of myocardial infarction was assigned if any determination of CK-MB exceeded the upper limit of normal, and the diagnosis of each patient at or before 9 hours (early diagnosis) was compared to the ultimate diagnosis at 14 to 24 hours (final diagnosis) beyond initial assessment.

RESULTS

Of the 528 included patients, 523 patients (99.1%) had identical early and final diagnostic outcomes; 5 patients (0.9%) had conflicting results. An early diagnosis of myocardial infarction was assigned to 195 of the 528 patients (36.9%). Of these, 190 achieved the diagnosis within 9 hours (sensitivity 97.4%). The negative predictive value was 98.5%.

CONCLUSION

Standard CK-MB mass measurements within 9 hours of arrival provided an accurate clinical assessment in > 99% of the cases. The high sensitivity and negative predictive values suggest that early diagnosis of myocardial infarction is feasible and reliable.

The use of extracorporeal life support in the treatment of influenza-associated myositis/rhabdomyolysis

A 13-year-old girl presented to the emergency department with fatigue, headaches and muscle stiffness after returning from a family camping trip. Within 24 h, she was transferred to ICU with general oedema and low saturations, where she had a cardio-respiratory arrest and was placed on veno-arterial extracorporeal membrane oxygenation (ECMO). The patient was successfully supported with ECMO for profound myocardial dysfunction and haemofiltration for rhabdomyolysis and acute renal failure.

Patients who present with profound myocardial dysfunction and myoglobinuria as a consequence of viral infection can be successfully supported with ECMO.

Noninvasive cardiac imaging in suspected acute coronary syndrome. Nat Rev Cardiol. 2016;13:266-275. [PMID: 26911331 DOI: 10.1038/nrcardio.2016.18]

Noninvasive cardiac imaging has an important role in the assessment of patients with acute-onset chest pain. In patients with suspected acute coronary syndrome (ACS), cardiac imaging offers incremental value over routine clinical assessment, the electrocardiogram, and blood biomarkers of myocardial injury, to confirm or refute the diagnosis of coronary artery disease and to assess future cardiovascular risk. This Review covers the current guidelines and clinical use of the common noninvasive imaging techniques, including echocardiography and stress echocardiography, computed tomography coronary angiography, myocardial perfusion scintigraphy, positron emission tomography, and cardiovascular magnetic resonance imaging, in patients with suspected ACS, and provides an update on the developments in noninvasive imaging techniques in the past 5 years.

Reliable exclusion of acute coronary syndrome among hospitalized patients with elevated troponin

BACKGROUND

Elevated cardiac troponin I (cTnI) occurs in acute coronary syndrome (ACS) as well as various scenarios not associated with ACS.

HYPOTHESIS

Simple clinical criteria can reliably exclude ACS among hospitalized patients with elevated cTnI.

METHODS

Records for patients hospitalized from January to April 2011 with elevated cTnI (>0.29 ng/dL) and an available echocardiogram were retrospectively reviewed. Patients with ST-segment elevation myocardial infarction were excluded. Based on available clinical data, patients were classified as having ACS or elevation of cTnI unrelated to ACS (non-ACS). Median follow-up was 365 days.

RESULTS

Of 265 records meeting inclusion criteria, 82 (31%) had ACS and 183 (69%) had non-ACS. In multivariable analysis, odds ratios for non-ACS were 7.6 (95% confidence interval [CI]: 3.8-15.3) for peak cTnI <2 ng/dL, 6.3 (95% CI: 3.1-13.0) for absent wall-motion abnormality, and 4.4 (95% CI: 2.2-8.6) for no prior coronary artery disease history. The area under the receiver operating curve for amodel using these 3 variables was 0.86, with a 98% negative predictive value for excluding ACS. Patients who met these 3 criteria had no ACS-related deaths over 1-year follow-up.

CONCLUSIONS

Hospitalized patients with peak Tn level<2 ng/dL, no prior history of coronary artery disease, and no new echocardiographic wall-motion abnormality appear to have a very low likelihood of ACS. Prospective validation of these results is needed to determine whether additional diagnostic testing could be safely avoided in hospitalized patients meeting these simple clinical criteria.

Imaging strategies for acute chest pain in the emergency department

OBJECTIVE

Echocardiography, radionuclide myocardial perfusion imaging (MPI), and coronary CT angiography (CTA) are the three main imaging techniques used in the emergency department for the diagnosis of acute coronary syndrome (ACS). The purpose of this article is to quantitatively examine existing evidence about the diagnostic performance of these imaging tests in this setting.

CONCLUSION

Our systematic search of the medical literature showed no significant difference between the modalities for the detection of ACS in the emergency department. There was a slight, positive trend favoring coronary CTA. Given the absence of large differences in diagnostic performance, practical aspects such as local practice, expertise, medical facilities, and individual patient characteristics may be more important.

Circulating cardiac troponins levels and cardiac dysfunction in children with acute and fulminant viral myocarditis

OBJECTIVES

To study the correlation between cardiac troponins blood levels and degrees of cardiac dysfunction in children with acute and fulminant viral myocarditis and to study their prognostic role in predicting the outcomes and risk of having dilated cardiomyopathy.

METHODOLOGY

Troponin I & T blood levels were measured in 65 children with acute or fulminant viral myocarditis. The cardiac functions of RV & LV were assessed by Doppler echocardiography.

RESULTS

The levels of cTnI & CTnT were significantly higher in patients with fulminant myocarditis than in controls and children with acute myocarditis (p < 0.05 & <0.001* respectively). The cardiac functions were significantly impaired in fulminant myocarditis than in acute myocarditis (p < 0.001*). There were negative correlations between the cardiac troponins levels and the cardiac functions measured by echocardiography in children with acute and fulminant myocarditis. There were 3 deaths (7.5%), and 10 (25%) children developed dilated cardiomyopathy in acute myocarditis while there were eight deaths (32%) and one patient (4%) who developed dilated cardiomyopathy in fulminant myocarditis group.

CONCLUSION

Cardiac troponins levels can predict the severity of myocarditis and the prognosis on the short-term level. Fulminant myocarditis was associated with higher levels of both cTn I & cTn T than acute myocarditis. Despite that fulminant myocarditis has a more aggressive course, the risk of developing cardiomyopathy was less than in acute myocarditis.

Resting magnetocardiography predicts 3-year mortality in patients presenting with acute chest pain without ST segment elevation

OBJECTIVE

Magnetocardiography (MCG) as a noninvasive, noncontact and risk-free diagnostic method predicts ischemic coronary artery disease (CAD) in patients with acute chest pain at admission with high accuracy. However, it remains unclear whether MCG findings can add prognostic information.

METHOD

A cohort of 402 consecutive patients presenting at the intensive care unit (ICU) with acute chest pain without ST segment elevation (NSTEMI) were included in a prospective registry. In order to prove the prognostic value of MCG a head-to-head comparison of the admission MCG, ECG, TnI, and ECHO tests was made.

RESULTS

In 43 patients (10.7%) the MCG could not be analyzed due to insufficient signal-to-noise ratio. Complete follow-up over a period of up to 3 years was obtained in 355 out of the 359 patients (98.9%). Age at admission was 67.2 +/- 10.3 years, 59.7% males. In the group of patients with an abnormal MCG at admission, 43 out of 249 patients (17.3%) died in the follow-up period, while in the group of patients with a normal MCG at admission only 4 out of 106 patients died (3.77%). The relative risk was 4.58 (95% confidence intervals: 1.68-12.42). A multivariate regression analysis revealed the highest mortality risk for patients with diabetes mellitus and an abnormal MCG at admission (RR = 18.0; 95% CI: 2.49-133.3).

CONCLUSION

Resting MCG at hospital admission predicts 3-year mortality in patients presenting with acute chest pain without ST segment elevation in the ECG. MCG seems to be valuable in identifying chest pain patients at highest risk.

Should troponin and creatinine kinase be routinely measured after vascular surgery?

The current guidelines for the evaluation and prediction of adverse cardiovascular events (CVEs) following vascular surgery in high-risk patients recommends serial electrocardiograms (ECGs) but not biomarkers such as cTn-I and CK-MB. The objective of this study was to determine whether biomarkers should be routinely measured in high-risk patients undergoing vascular surgery. A multicenter, prospective study with investigators blinded to core laboratory results was conducted. cTn-I and CK-MB were obtained on the day of surgery, as well as 24 hours, 72 hours and 120 hours after surgery, 24 hours prior to planned hospital discharge and at the onset of symptoms of a suspected CVE. The CVE was adjudicated by an endpoint committee using ECG, biomarker and symptoms data and was defined as cardiac death or myocardial infarction (MI) occurring up to 30 days after surgery. A total of 784 patients, with a mean age of 70.1 (SD +/- 9.8), underwent vascular surgery. Of the 83 patients with a CVE, cTn-I was positive in 42 and CK-MB was positive in 29 on or before the day of the CVE. The number of patients not classified as having a CVE but positive for elevation of cTn-I or CK-MB was 64 and 20, respectively. cTn-I was more sensitive than CK-MB (50.6% versus 34.9%) for predicting a CVE. The optimum time for measuring cTn-I after surgery with the highest positive predictive value was 24 hours. In conclusion, these data support routine serial measurement of cTn-I after vascular surgery.

Rapid diagnosis of myocardial injury with troponin T and CK-MB relative index

BACKGROUND

Current hospital practice involves protracted observation of chest-pain patients to rule out myocardial infarction. Concurrent measurement of multiple biomarkers may increase sensitivity and make rapid diagnosis feasible.

OBJECTIVE

We sought to determine the optimal biomarker strategy for highly sensitive, early diagnosis of myocardial injury.

STUDY DESIGN

A prospective evaluation of 171 acute coronary syndrome patients admitted to a single university medical center was performed. Blood tests for creatine kinase (CK), CK myocardial band isoenzyme (CK-MB), and troponin T were obtained at 0, 3, 6, 8, and 16 hours after presentation to the emergency department. Myocardial injury was defined as a troponin T level of >or=0.03 ng/mL.

RESULTS

Troponin T had sensitivities of 79.7%, 95.7%, and 98.4% at the time of initial presentation, 3 and 6 hours after presentation, respectively. Using a combination of troponin T and CK-MB relative index, sensitivity on presentation was increased to 90.6%. The sensitivity was improved to 97.9% and 100% at 3 and 6 hours, respectively.

CONCLUSION

This study demonstrates that the diagnosis of myocardial injury can be accurately excluded within 6 hours of admission with high sensitivity using troponin T. The combination of troponin T and CK-MB relative index provided the largest improvement in diagnostic sensitivity at patient arrival. These results support the feasibility of rapid, efficient triage for the emergent presentation of patients with chest pain.

The diagnostic value of troponin T testing in the community setting

BACKGROUND

Many patients presenting with chest pain to their family physician are referred to the emergency room, in part, due to lack of accurate objective diagnostic tools. This study aimed to assess the diagnostic value of bedside troponin T kit testing in patients presenting with chest pain to their family physician.

DESIGN

Prospective, multi-center study.

METHODS

Consecutive subjects with chest pain were recruited from 44 community clinics in Jerusalem. Following clinical assessment by the family physician, qualitative troponin kit testing was performed. Patients with a negative clinical assessment and negative troponin kit were sent home and all others were referred to the emergency room. The final diagnosis at the time of hospital discharge was recorded and telephone follow up was performed after 60 days. Positive predictive value, negative predictive value, sensitivity and specificity of troponin kit for myocardial infarction diagnosis and of family physician for hospitalization, were assessed.

RESULTS

Of 392 patients enrolled, 349 (89%) were included in the final analysis. The prevalence of myocardial infarction was 1.7%. The positive and negative predictive values of the troponin kit for myocardial infarction diagnosis were 100% and 99.7%, respectively. The positive and negative predictive values of the family physician's assessment to predict hospitalization were 41.4% and 94.1%, respectively.

CONCLUSIONS

Troponin kit testing is an important tool to assist the family physician in the assessment of patients with chest pain in the community setting. Troponin kit testing may identify otherwise undiagnosed cases of myocardial infarctions, and reduce unnecessary referrals to the emergency room.

Acute coronary syndromes in the emergency department: diagnostic characteristics, tests, and challenges

Failure to diagnose patients who have acute coronary syndromes (ACSs)-either acute myocardial infarction (AMI) or unstable angina pectoris (UAP)-who present to the emergency department (ED) remains a serious public health issue. Better understanding of the pathophysiology of coronary artery disease has allowed the adoption of a unifying hypothesis for the cause of ACSs: the conversion of a stable atherosclerotic lesion to a plaque rupture with thrombosis. Thus, physicians have come to appreciate UAP and AMI as parts of a continuum of ACSs. This article reviews the state of the art regarding the diagnosis of ACSs in the emergency setting and suggests reasons why missed diagnosis continues to occur, albeit infrequently.

Echocardiography in the evaluation of patients in chest pain units

Using percutaneous angioplasty to induce the ischemic cascade in the cardiac catheterization laboratory, echocardiographic wall motion abnormalities have been documented to precede electrocardiographic abnormalities and angina. Therefore, detection of cardiac wall motion abnormalities is potentially more sensitive than the history, physical examination, and ECG for identification of myocardial ischemia. Echocardiography is highly reliable for assessing cardiac wall motion and, thus, it has been used for diagnosis and risk assessment in patients presenting to the emergency department (ED) with symptoms suggestive of myocardial ischemia. In patients who have acute ST-elevation myocardial infarction (MI), echocardiography is comparable to invasive left ventriculography for detecting wall motion abnormalities. However, the usefulness of echocardiography in the low-risk population that has chest pain of uncertain origin and a nondiagnostic initial presentation is less well established.

Predictors of short-term outcome in acute chest pain without ST-segment elevation

BACKGROUND

Management of acute chest pain in the emergency room constitutes a challenge.

METHODS

Seven hundred and one consecutive patients were evaluated by clinical history (chest pain score and risk factors), ECG, troponin I and early (<24 h) exercise testing in low risk patients (n=165). A composite end-point (recurrent unstable angina, acute myocardial infarction or cardiac death) was recorded during hospital stay or in ambulatory care settings for patients discharged after early exercise testing.

RESULTS

The end-point occurred in 122 patients (17%). Multivariate analysis identified the following predictors: chest pain score > or =11 points (OR=1.8, 2-2.8, 95% CI, P=0.007), age > or =68 (OR 1.6, 1.1-2.4 CI 95%, P=0.03), insulin-dependent diabetes mellitus (OR 1.9, 1.1-3.4 CI 95%, P=0.02), a history of coronary surgery (OR 3.3, 1.5-7.2 CI 95%, P=0.003), ST-segment depression (OR 1.9, 1.2-3.0 CI 95%, P=0.009) and troponin I elevation (OR 1.6, 1.1-2.5, CI 95%, P=0.05). ST-segment depression produced a high end-point increase (31 vs. 13%, P=0.0001). Troponin I elevation increased the risk in the subgroup without ST-segment depression (20 vs. 11%, P=0.006) but did not further modify the risk in the subgroup with ST depression (31 vs. 28%, ns). Nevertheless, the negative ECG and troponin I subgroup showed a non-negligible end-point rate (16% when pain score > or =11 or 7% when pain score <11, P=0.004). Finally, no patient with a negative exercise test presented events compared to 7% of those with a non-negative test (RR=2.5, 2.1-3.1 95% CI, P=0.01).

CONCLUSIONS

Emergency room evaluation of chest pain should not focus on a single parameter; on the contrary, the clinical history, ECG, troponin and early exercise testing must be globally analysed.

Combining baseline clinical descriptors and real-time response to therapy: the incremental prognostic value of continuous ST-segment monitoring in acute myocardial infarction

BACKGROUND

Clinical descriptors and ST-segment recovery variables hold prognostic information for clinical outcome after thrombolysis for acute myocardial infarction (MI). We sought to define the incremental prognostic value of continuous 12-lead ST-segment monitoring variables to clinical risk descriptors identified by the Global Utilization of Streptokinase and TPA (alteplase) for Occluded Coronary Arteries (GUSTO-I) trial 30-day mortality analysis.

METHODS

Of 1,777 patients enrolled in continuous ST-segment substudies from the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI-9), GUSTO-I, Duke University Clinical Cardiology Study (DUCCS-II), Integrilin to manage Platelet Aggregation to Combat Thrombus in Acute Myocardial Infarction (IMPACT-AMI), Promotion of Reperfusion by Inhibition of Thrombin During Myocardial Infarction Evolution (PRIME), and Platelet Aggregation Receptor Antagonist Dose Investigation and Reperfusion Gain in Myocardial Infarction (PARADIGM) trials, 825 patients qualified for assessment of time to recovery. ST recovery variables analyzed were time to stable ST-recovery and late ST elevation. Patients who were at low clinical risk (n = 261) had no high-risk descriptors, and patients at high clinical risk (n = 564) had at least 1 of these high-risk descriptors: age >or=70 years, systolic blood pressure <or=110 mm Hg, heart rate >or=90 beats/min, anterior MI, or previous MI. High (n = 90), moderate (n = 318), and low (n =417) ST-risk groups were defined by the presence of both slow ST recovery and late ST elevation, one or the other, or neither, respectively. End points analyzed were inhospital death and combined death, reinfarction, or congestive heart failure.

RESULTS

There was a trend toward increased mortality rate in the high-clinical/high-ST-risk group. For the composite end point, ST subgrouping resulted in significant event stratification in both patients at low and high clinical risk. In multivariable analysis, age and heart rate were independent predictors of both mortality and the composite end point. Late ST elevation added incremental prognostic information.

CONCLUSION

Age, heart rate, and late ST elevation are powerful, independent predictors of adverse clinical outcome. Continuous monitoring allows noninvasive assessment of the response to therapy. Consequently, this technique will enhance the potential to risk-stratify individual patients in a real-time setting.

Diagnosis of acute cardiac ischemia

A better understanding of coronary syndromes allow physicians to appreciate UAP and AMI as part of a continuum of ACI. ACI is a life-threatening condition whose identification can have major economic and therapeutic importance as far as threatening dysrhythmias and preventing or limiting myocardial infarction size. The identification of ACI continues to challenge the skill of even experienced clinicians, yet physicians continue (appropriately) to admit the overwhelming majority of patients with ACI; in the process, they admit many patients without acute ischemia [2], overestimating the likelihood of ischemia in low-risk patients because of magnified concern for this diagnosis for prognostic and therapeutic reasons. Studies of admitting practices from a decade ago have yielded useful clinical information but have shown that neither clinical symptoms nor the ECG could reliably distinguish most patients with ACI from those with other conditions. Most studies have evaluated the accuracy of various technologies for diagnosing ACI, yet only a few have evaluated the clinical impact of routine use. The prehospital 12-lead ECG has moderate sensitivity and specificity for the diagnosis of ACI. It has demonstrated a reduction of the mean time to thrombolysis by 33 minutes and short-term overall mortality in randomized trials. In the general ED setting, only the ACI-TIPI has demonstrated, in a large-scale multicenter clinical trial, a reduction in unnecessary hospitalizations without decreasing the rate of appropriate admission for patients with ACI. The Goldman chest pain protocol has good sensitivity for AMI but was not shown to result in any differences in hospitalization rate, length of stay, or estimated costs in the single clinical impact study performed. The protocol's applicability to patients with UAP has not been evaluated. Single measurement of biomarkers at presentation to the ED has poor sensitivity for AMI, although most biomarkers have high specificity. Serial measurements can greatly increase the sensitivity for AMI while maintaining their excellent specificity. Biomarkers cannot identify most patients with UAP. Finally, diagnostic technologies to evaluate ACI in selected populations, such as echocardiography, sestamibi perfusion imaging, and stress ECG, may have very good to excellent sensitivity; however, they have not been sufficiently studied.

Independent value of tissue harmonic echocardiography for risk stratification in patients with non-ST-segment elevation acute chest pain

BACKGROUND

Clinical factors, electrocardiography, and cardiac troponins provide a satisfactory, although not ideal, means for risk-stratifying patients with non-ST-segment elevation acute chest pain. Tissue harmonic echocardiography enables improved assessment of wall motion abnormalities compared with fundamental echocardiography and may be a useful adjunct for the detection of myocardial ischemia and infarction. We aimed to determine the value of tissue harmonic echocardiography in relation to electrocardiographic and biochemical factors for risk stratification of these patients.

RESULTS

Eighty patients with non-ST-segment elevation chest pain were studied using tissue harmonic echocardiography and troponin-T and -I. Fifty-five (69%) patients had abnormal electrocardiograms and 47 (59%) patients had abnormal echocardiograms. Thirteen patients (17%) had elevated troponin-T levels and 17 (21%) had elevated levels of troponin-I. Twelve patients (15%) had a myocardial infarction as the presenting event and, of the remaining 68 patients, 24 sustained an adverse cardiac event during the follow-up period (3 cardiac deaths, 4 nonfatal myocardial infarctions, 17 revascularization procedures). Troponin-T (98%), troponin-I (97%), and echocardiography (97%) all had similar negative predictive values for myocardial infarction as the presenting event, but troponin-T was the only independent predictor of this endpoint (relative risk 230, 95% CI 22-2427). An abnormal echocardiogram was the only independent predictor of subsequent events. The independent predictors of all events were age, troponin-T, and echocardiography.

CONCLUSION

Tissue harmonic echocardiography provides independent information for risk stratification of patients with non-ST-segment elevation acute chest pain.

Prognostic value of 2D echocardiography in patients presenting with acute chest pain and non-diagnostic ECG for ST-elevation myocardial infarction

The purpose of the present study was to test the hypothesis that early detection of regional wall motion abnormalities (WMA) by 2D echocardiography (ECHO) accurately predicts further cardiac events in patients presenting with acute chest pain. A prospective analysis was performed in subjects admitted with the first presentation of acute chest pain and a non-diagnostic ECG for acute ST-elevation myocardial infarction. Patients with known coronary artery disease were excluded. All subjects were contacted by phone for a 30days follow-up regarding cardiac events defined as PCI/CABG, AMI, and death. In 132 consecutive patients (89 male, 43 female) complete data sets consisting of case history (H; abnormal: typical angina), ECG (abnormal: ST-depression, T-inversion, atypical ST-elevation, LBBB), serum markers (TnI; abnormal: elevation of troponin I=0.5 ng/ml), ECHO (abnormal: WMA) and follow-up were available. In 45 patients, 60 cardiac events occurred (three deaths, 24 AMI, 33 PCI/CABG). Positive (PPV; %) and negative predictive values (NPV; %) of ECHO were superior to all other diagnostic tests (P<0.05 each) for adverse cardiac events, evolving AMI or death, and superior to history and ECG for later need of revascularisation (PCI/ACVB). Multivariate analysis revealed that WMA in ECHO predict cardiac events independently of age, gender, and the common combination of investigations (H/ECG/TnI). A significant independent impact of ECHO was also determined for the prediction of AMI/death or PCI/CABG. The study shows that early 2D echocardiography provides superior prognostic information concerning the risk of subsequent complications in patients with acute chest pain and a non-diagnostic ECG for ST-elevation-AMI.

Cardiac troponins

Cardiac troponins I and T are proteins integral to the function of cardiac muscle. They are very sensitive markers for the detection of myocardial damage, and the ability to assay their serum levels accurately and quickly have revolutionized the concepts of minor myocardial injury and infarction. They are also powerful prognostic indicators of future adverse cardiac events. Limitations, more of troponin T than I, include decreased specificity in renal failure and skeletal muscle disease. Rapid, whole blood assays are now available that can be done at the patient's bedside. This review discusses the cardiac troponins, their biochemistry, the assays for them currently available, and their roles in the evaluation of cardiac disease in the Emergency Department (ED).

The effect of real time 2-D-echocardiography on medical decision-making in the emergency department

2-D Echocardiography (ECHO) represents an important tool for the evaluation of the Emergency Department (ED) patient with suspected cardiovascular (CV) pathology. The present study assesses the degree of effect of real time ECHO on Emergency Physician diagnosis, treatment, and disposition of CV patients and their level of confidence in these decisions. One hundred ED patients with suspected CV pathology were enrolled into this prospective, interventional study. Senior level physicians were asked their level of confidence regarding patient diagnosis, treatment, and disposition decisions before and after the ECHO was done and interpreted by a certified sonographer in the ED. Physicians were then asked if ECHO changed any of these decisions. Patient age was 56.4 +/- 15.8 (range 27-93) years. Chest pain (n = 45) and shortness of breath (n = 38) were the most common presenting symptoms. Eighty-six of the patients were admitted. There was a change in diagnosis in 37 patients, a change in treatment in 25 patients, and a change in disposition in 11 patients. Physicians indicated there was a change in confidence level post-ECHO in approximately 50% of patients. A significant change was seen in both a more and a less confident direction. Physicians were 3 times more confident regarding diagnosis, 7 times more confident regarding treatment, and 3 times more confident regarding disposition decision-making. Real time ECHO appears to have a significant level of impact on physician level of confidence and medical decision-making concerning patients with suspected cardiovascular pathology in the ED.

Acute ischemic syndromes. Chest pain center concept

CPCs have been developed to meet the clinical challenge posed by the diverse group of patients presenting to the ED with findings suggestive of a coronary event. Using a protocol-driven approach, high- and low-risk patients can be identified on presentation, facilitating urgent therapy in the former and triage of the latter to more deliberate management. Most CPCs focus on low-risk patients who are being increasingly managed by accelerated diagnostic protocols. These methods comprise systematic strategies that include innovative diagnostic approaches during a 6 to 12 hour period of observation with serial ECGs, continuous monitoring and cardiac biomarker measurements. A negative evaluation is usually followed by predischarge stress testing, and positive findings mandate admission. An essential aspect of the CPC strategy is continuity of care for patients with negative cardiac evaluations. Current data indicate that management of low-risk patients with chest pain in a CPC is safe accurate, and appears to be cost-effective.

Feasibility and reliability of rapid diagnosis of myocardial infarction

BACKGROUND

Prevailing hospital practice dictates a protracted phase of observation for patients with chest pain to establish or exclude the diagnosis of myocardial infarction. Early diagnosis of acute myocardial infarction may improve patient care and reduce both complications and hospital costs. A study was performed to investigate the feasibility of early diagnosis of myocardial infarction within the first 9 hours of the hospital stay.

METHODS

The records of all patients admitted with chest pain within one calendar year were analyzed. The timing of creatine kinase-MB (CK-MB) quantification was determined with reference to the initial phlebotomy (time 0). An enzymatic diagnosis of myocardial infarction was assigned if any determination of CK-MB exceeded the upper limit of normal, and the diagnosis of each patient at or before 9 hours (early diagnosis) was compared to the ultimate diagnosis at 14 to 24 hours (final diagnosis) beyond initial assessment.

RESULTS

Of the 528 included patients, 523 patients (99.1%) had identical early and final diagnostic outcomes; 5 patients (0.9%) had conflicting results. An early diagnosis of myocardial infarction was assigned to 195 of the 528 patients (36.9%). Of these, 190 achieved the diagnosis within 9 hours (sensitivity 97.4%). The negative predictive value was 98.5%.

CONCLUSION

Standard CK-MB mass measurements within 9 hours of arrival provided an accurate clinical assessment in > 99% of the cases. The high sensitivity and negative predictive values suggest that early diagnosis of myocardial infarction is feasible and reliable.

Echocardiography, nuclear scintigraphy, and stress testing in the emergency department evaluation of acute coronary syndrome

There are between 3 and 5 million visits to EDs each year for complaints of chest pain. Of these, about one half of the patients have a noncardiac cause for their chest pain. Of the remainder, about 30% to 50% have significant coronary disease. It is quite clear that patients who are at high risk for a coronary event should be admitted to the hospital. For the low-to-moderate risk patients, the decision to admit or discharge the patient from the ED is not quite so easy. The emergency physician has to decide which tests can be helpful in the decision-making process, this can be undertaken in conjunction with a consultative cardiologist. It can be argued that if a patient does not have a normal test result whichever that evaluatory test is), then the patient should be admitted for further work-up and evaluation. The easiest test to perform in the ED setting is an echocardiogram. The images can be sent by telecommunication to a qualified echocardiogram reader for interpretation. This also has a reasonable NPV, although not necessarily as good as some of the other modalities available, unless interpreted in light of cardiac enzyme test results. If the index of suspicion is still high, then a stress echocardiogram can be considered. This has an excellent NPV and can be easily performed in [table: see text] most patients. This should not be undertaken in the face of an evolving MI, and patients should be observed for at least 8 hours after their initial presentation to the ED prior to undergoing a provocative test. Nuclear scintigraphy, another modality available for cardiac risk stratification, can be a logistical nightmare. The nuclear isotopes are strictly regulated by the Nuclear Regulatory Commission. The emergency physician may inject the isotopes, provided that he or she has undergone the necessary radiation training. Also, the patient must be removed from the ED to a radioisotope-approved area for the duration of the scan. One of the most difficult questions left open after review of all these analytical modalities is the duration of time these test results remain valid; when does an individual patient need to be reevaluated as to their specific pretest probability? The answer to this question lies in the presenting clinical scenario. If the patient presents with a similar inciting trigger for his or her symptoms, and the cardiac risk profile has not changed appreciably, then the previous study (whether a provocative stress test or even a cardiac catheterization) probably can be reliably counted. If the patient's risk profile has changed or the symptoms are new or more intense, the physician is compelled to pursue this encounter as a new, acute event. This can be true even in the setting of a previous cardiac catheterization that showed nonobstructive coronary disease, because plaque rupture can be acute and unpredictable. Ultimately, optimal care calls for each institution to develop a specific approach, in conjunction with their consultative cardiologist or critical care specialist, to enhance patient care, safety, and diagnostic outcome, while maintaining cost efficiency.

Accuracy of imaging technologies in the diagnosis of acute cardiac ischemia in the emergency department: a meta-analysis

STUDY OBJECTIVE

We sought to quantitatively evaluate the evidence on the diagnostic performance of imaging technologies (including rest and stress echocardiography and technetium-99m sestamibi scanning) for the diagnosis of acute cardiac ischemia and acute myocardial infarction in the emergency department.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. Both prospective and retrospective studies qualified for the assessment of diagnostic performance. Diagnostic performance was assessed by means of random-effect estimates of test sensitivity, specificity, and the diagnostic odds ratio and was summarized by using summary receiver-operating characteristic curves.

RESULTS

Diagnostic accuracy was evaluated in 10 studies of rest echocardiography, 2 studies of dobutamine stress echocardiography, and 6 studies of technetium-99m sestamibi scanning. However, only 3 rest echocardiography and 5 technetium-99m sestamibi studies evaluated patients strictly in the ED setting. Patient populations were often highly selected to represent low- or moderate-risk groups. When limited to ED studies, rest echocardiography showed excellent sensitivity of 93% (95% CI, 81% to 97%) and good specificity of 66% (95% CI, 43% to 83%). The results were similar when all studies were considered, including data from reports of admitted patients and patients sent to the cardiac care unit. There was insufficient literature on stress echocardiography in the ED to properly assess the technology. Technetium-99m sestamibi scanning also showed excellent sensitivity (range, 91.5% to 100%) and good specificity (range, 49.3% to 84.4%) for acute myocardial infarction; for acute cardiac ischemia, the random-effects pooled sensitivity was 89% (95% CI, 73% to 96%), and the pooled specificity was 77% (95% CI, 63% to 87%).

CONCLUSION

For selected low- and moderate-risk patient groups, echocardiography and technetium-99m sestamibi imaging appear to have very good diagnostic performance with a similar sensitivity and specificity profile. More evidence should be accumulated on their performance specifically in the ED setting.

Accuracy of biomarkers to diagnose acute cardiac ischemia in the emergency department: a meta-analysis

STUDY OBJECTIVE

We sought to evaluate quantitatively the evidence on the diagnostic performance of presentation and serial biochemical markers for emergency department diagnosis of acute cardiac ischemia (ACI), including acute myocardial infarction (AMI) and unstable angina.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. We examined the diagnostic performance of creatine kinase, creatine kinase-MB, myoglobin, and troponin I and T testing. Diagnostic performance was assessed by using estimates of test sensitivity and specificity and was summarized by summary receiver-operating characteristic curves.

RESULTS

Only 4 studies were found that evaluated all patients with ACI; 73 were found that focused only on a diagnosis of AMI. To diagnose ACI, presentation biomarker tests had sensitivities of 16% to 19% and specificities of 96% to 100%; serial biomarker tests had sensitivities of 31% to 45% and specificities of 95% to 98%. Considering only the diagnosis of AMI, presentation biomarker tests had summary sensitivities of 37% to 49% and summary specificities of 87% to 97%; serial biomarker tests had summary sensitivities of 79% to 93% and summary specificities of 85% to 96%. Variation of test sensitivity was best explained by test timing. Longer symptom duration or time between serial tests yielded higher sensitivity.

CONCLUSION

The limited evidence available to evaluate the diagnostic accuracy of biomarkers for ACI suggests that biomarkers have very low sensitivity to diagnose ACI. Thus, biomarkers alone will greatly underdiagnose ACI and will be inadequate to make triage decisions. For AMI diagnosis alone, multiple testing of individual biomarkers over time substantially improves sensitivity, while retaining high specificity, at the expense of additional time. Further high-quality studies are needed on the clinical effect of using biomarkers for patients with ACI in the ED and on optimal timing of serial testing and in combination with other tests.

Markers of myocardial damage and inflammation in relation to long-term mortality in unstable coronary artery disease. FRISC Study Group. Fragmin during Instability in Coronary Artery Disease

BACKGROUND

In patients with unstable coronary artery disease, there is a relation between the short-term risk of death and blood levels of troponin T (a marker of myocardial damage) and C-reactive protein and fibrinogen (markers of inflammation). Using information obtained during an extension of the follow-up period in the Fragmin during Instability in Coronary Artery Disease trial, we evaluated the usefulness of troponin T, C-reactive protein, and fibrinogen levels and other indicators of risk as predictors of the long-term risk of death from cardiac causes.

METHODS

Levels of C-reactive protein and fibrinogen at enrollment and the maximal level of troponin T during the first 24 hours after enrollment were analyzed in 917 patients included in a clinical trial of low-molecular-weight heparin in unstable coronary artery disease. The patients were followed for a mean of 37.0 months (range, 1.6 to 50.6).

RESULTS

During follow-up, 1.2 percent of the 173 patients with maximal blood troponin T levels of less than 0.06 microg per liter died of cardiac causes, as compared with 8.7 percent of the 367 patients with levels of 0.06 to 0.59 microg per liter and 15.4 percent of the 377 patients with levels of at least 0.60 microg per liter (P=0.007 and P=0.001, respectively). The rates of death from cardiac causes were 5.7 percent among the 314 patients with blood C-reactive protein levels of less than 2 mg per liter, 7.8 percent among the 294 with levels of 2 to 10 mg per liter, and 16.5 percent among the 309 with levels of more than 10 mg per liter (P=0.29 and P=0.001, respectively). The rates of death from cardiac causes were 5.4 percent among the 314 patients with blood fibrinogen levels of less than 3.4 g per liter, 12.0 percent among the 300 with levels of 3.4 to 3.9 g per liter, and 12.9 percent among the 303 with levels of at least 4.0 g per liter (P=0.004 and P=0.69, respectively). In a multivariate analysis, levels of troponin T and C-reactive protein were independent predictors of the risk of death from cardiac causes.

CONCLUSIONS

In unstable coronary artery disease, elevated levels of troponin T and C-reactive protein are strongly related to the long-term risk of death from cardiac causes. These markers are independent risk factors, and their effects are additive with respect to each other and other clinical indicators of risk.

Crack cocaine, myocardial infarction, and troponin I levels at the time of cesarean delivery

IMPLICATIONS

During the peripartum period, cocaine-abusing women are highly susceptible to myocardial infarction. This report describes a case of myocardial infarction diagnosed by increased troponin I levels in a pregnant patient with a history of recent crack cocaine use and severe preeclampsia.

Evaluation of chest pain suspicious for acute coronary syndrome: use of an accelerated diagnostic protocol in a chest pain evaluation unit

Management of patients presenting to the emergency department with chest pain suggestive of acute myocardial infarction (AMI) remains a continuing challenge. A low threshold for admission has been traditional because of concern for patient welfare and the litigation potential associated with the inadvertent discharge of patients with ischemic events. Because of this approach, < 30% of patients admitted for chest pain ultimately are found to have an acute coronary syndrome. To reduce unnecessary admissions, maintain patient safety, and enhance cost-effectiveness, innovative strategies have been applied to the management of patients with chest pain. It is now recognized that a low-risk group can be identified by the clinical presentation and initial electrocardiogram. Chest-pain centers have been developed to provide further risk stratification and systematic management of these patients. We employ an accelerated diagnostic protocol based on immediate exercise treadmill testing to evaluate low-risk patients. Moderate-risk patients are assessed over a 6-hour observation period with serial electrocardiograms and evaluation of cardiac-injury markers. Patients with positive evaluations are admitted. Those with negative results undergo either exercise echocardiography or rest myocardial perfusion imaging utilizing technetium-99m sestamibi. Patients with positive functional tests are admitted. Those with negative studies are discharged with outpatient follow-up. These strategies have provided a safe and accurate means of patient disposition from the emergency department with the potential for vital cost savings.

Utility of cardiac troponin I, creatine kinase-MB(mass), myosin light chain 1, and myoglobin in the early in-hospital triage of "high risk" patients with chest pain

OBJECTIVE

To evaluate the use of cardiac troponin I (cTnI), creatine kinase-MB(mass) (CK-MB(mass)), myosin light chain 1 (MLC 1), and myoglobin in identifying "high risk" patients with chest pain who will experience serious cardiac events (SCEs) in hospital.

DESIGN

Prospective study.

SETTING

University affiliated medical centre in Philadelphia, USA.

PATIENTS

208 patients with chest pain, at > 7% risk of acute myocardial infarction (MI), but without new ST segment elevation on their presenting ECG.

INTERVENTIONS

cTnI, CK-MB(mass), MLC 1, and myoglobin concentrations were obtained on admission (0 hour) and at 4, 8, 16, and 24 hours.

MAIN OUTCOME MEASURES

The sensitivity, specificity, positive and negative predictive value, and pre- and post-test probabilities of patients suffering an SCE in hospital were determined. SCEs included cardiac death, acute MI, cardiac arrest, life threatening cardiac arrhythmia, cardiogenic shock, and urgent coronary revascularisation.

RESULTS

Admission concentrations of all markers were poor predictors of SCEs in hospital but improved substantially at subsequent timepoints. cTnI and CK-MB(mass) were consistently the most useful prognostic indicators. If both were negative at 0, 4, and 8 hours, then 99% (95% confidence interval 96% to 100%) of patients remained free from SCEs. The only SCEs not thus predicted were revascularisation procedures and associated complications. Additional tests after 8 hours, or the inclusion of additional markers, did not improve predictive accuracy further.

CONCLUSIONS

Patients with high risk clinical features on admission who have negative cTnI and CK-MB(mass) concentrations at 0, 4, and 8 hours later have a favourable in-hospital prognosis and could be considered for early triage out of coronary care units.

The sensitivity of cardiac markers: an evidence-based approach

The aim of this study was to determine whether, using an evidence-based approach, the results of the papers found in the literature are valid and sufficiently scientifically rigorous to be used to definitely address the problem of cardiac marker sensitivity in detection of acute myocardial infarction. In particular, the diagnostic sensitivities of myoglobin, creatine kinase (CK)-MB isoenzyme, determined as mass concentration, CK-MB isoforms, and of the two cardiac troponins, troponin I and troponin T, were reviewed using a priori formulated inclusion/exclusion criteria for judging the eligibility of studies to be included in the analysis. A clear final message derived from this systematic analysis is the unacceptably poor diagnostic sensitivity of all evaluated markers at patient admission, with substantial failure rate to rule out myocardial infarction at this time. Myoglobin is at present the most sensitive of the markers studied for excluding early AMI with an optimum timing of sampling at patient presentation and approximately 4 h later. However, this marker cannot be used by itself as a proportion of patients admitted to the hospital with a late infarction could be missed. The early rate of rise of CK-MB mass and troponin T is similar. Maximum sensitivity of these two parameters is achieved by the analysis of a second sample 6 to 12 h after admission. Additional larger studies are needed to address the question which troponin shows earlier release after myocardial damage, and to clarify the role of CK-MB isoforms as a possible early marker of myocardial infarction.

Chest pain emergency units

Each year in the United States, more than 2 million patients are hospitalized with chest pain suggestive of myocardial ischemia, with fewer than 20% of these patients having an acute coronary event. Chest pain emergency units have been created to facilitate urgent therapy for patients with a serious cardiovascular event and to triage lower risk patients to less intensive, more cost-effective inpatient care or discharge to home. The clinical history, physical examination, and initial electrocardiogram are key to initial stratification of patients for further management, but additional methods are necessary to clearly distinguish patients with inconclusive findings at presentation as high- and low-risk. Innovative electrocardiographic methods have increased sensitivity for detecting myocardial ischemia. Accelerated diagnostic protocols with new cardiac serum markers can detect myocardial ischemia or infarction with increasing accuracy. Early echocardiographic, scintigraphic, and treadmill stress protocols can further evaluate patients who have nondiagnostic electrocardiograms and negative serum markers. This review presents the current status of chest pain emergency units and the evolving management strategies they encompass.

Evaluating the chest pain patient. Scope of the problem

With an understanding of the pathophysiology of ACS and an increasing number of early therapeutic options, there has been a shift in focus from ruling-out MI to identifying and stratifying risk in all patients with potential ACS. The presenting symptoms and ECG still remain the cornerstone of immediate diagnosis and triage. Through the application of new technologies, such as the cardiac troponins, and a reassessment of techniques, such as perfusion imaging and echocardiography, the clinician has an increasing selection of methods to rapidly assess chest pain of potential ischemic etiology. Coinciding with the evaluation of technology has been the development of the concept of the CPU and associated rapid diagnostic protocols. These protocols, whether they utilize the assistance of mathematic predictive instruments or represent simple triage schemes, form the backbone of a system to improve the care of patients with ACS in the current milieu of cost containment.

Role of Echocardiography in the Emergency Department for Identifying Patients with Myocardial Infarction and Ischemia

Echocardiography is a valuable, noninvasive diagnostic tool that can provide information on systolic function and valvular abnormalities and can provide alternative explanations for causes of chest pain. Experimental as well as clinical studies have shown that wall motion abnormalities have a high sensitivity for predicting myocardial infarction. More recent studies, performed in the emergency department on patients evaluated for myocardial ischemia, have reported similar results. An important aspect is that necrosis is not necessary to cause wall motion abnormalities; therefore, echocardiography can also be used to identify patients with ischemia without infarction. Importantly, sensitivity is significantly higher than that for electrocardiography and is comparable to that for myocardial perfusion imaging. Newer developments, such as digital transmission over telephone lines, may lead to more widespread routine use in the emergency department. Acute emergency department echocardiography appears to be a promising tool when used in the evaluation of patients with chest pain.

Clinical Use of Ischemic Markers and Echocardiography in the Emergency Department

We searched the medical literature for articles containing markers of cardiac ischemia and echocardiography in the evaluation of patients presenting to the emergency department to determine their combined clinical use. Several published articles indicate two-dimensional echocardiography is a useful and cost-effective imaging technique for the evaluation of patients with chest pain in the emergency department. New studies are emerging that evaluate ischemic markers in combination with echocardiography to assess patients presenting to the emergency department with chest pain. We searched the MEDLINE Database for English-language articles published from December 1980 to August 1998 using the key words troponin, echocardiography, myocardial infarction, and emergency. These key words were crossed referenced to determine publications in this area. Pertinent trials and reviews were selected from the database. There were six articles evaluating biochemical markers of ischemia and echocardiography to assess patients presenting with acute coronary syndromes in the emergency department. Very few studies combined the information obtained from novel ischemic markers and echocardiogram analysis to help delineate potential cardiac etiologies of acute coronary syndromes. However, the limited studies available indicate that echocardiography is both sensitive and specific for detecting acute myocardial infarction. The presence of regional wall motion abnormalities increases the chance of in-hospital complications and likelihood of developing congestive heart failure after admission for unstable angina. The combined use of troponin T levels and echocardiographic imaging was a more powerful predictor of adverse events than were isolated results. Myocardial scarring with ventricular wall thinning or aneurysm may allow for rapid diagnosis of 'occult' coronary artery disease in a patient presenting with chest pain who does not have a previous history of a cardiovascular event. Echocardiography may also help identify other cardiovascular causes of chest pain, such as aortic dissection, aortic stenosis, cardiac tamponade, pericarditis, and hypertrophic cardiomyopathy. The clinical use of combining ischemic markers of disease with echocardiographic imaging seems justified given their unique clinical advantages. Future clinical trials are needed to determine whether the combination of novel ischemic markers and echocardiography can provide for a more expedient and accurate diagnosis, resulting in improved patient care and a safe reduction in unnecessary hospitalization.