Utility and safety of immediate exercise testing of low-risk patients admitted to the hospital for suspected acute myocardial infarction

Current Use of Cardiac Biomarkers in Various Heart Conditions

Biomarkers are increasingly recognized to have significant clinical value in early identification and progression of various cardiovascular diseases. There are many heart conditions, such as congestive heart failure (CHF), ischemic heart diseases (IHD), and diabetic cardiomyopathy (DCM), and cardiac remodeling, in which the severity of the cardiac pathology can be mirrored through these cardiac biomarkers. From the emergency department (ED) evaluation of acute coronary syndromes (ACS) or suspected acute myocardial infarction (AMI) with cardiac marker Troponin to the diagnosis of chronic conditions like Heart Failure (HF) with natriuretic peptides, like B-type natriuretic peptide (BNP), N-terminal pro-B- type natriuretic peptide (Nt-proBNP) and mid regional pro-atrial natriuretic peptide (MR- proANP), their use is continuously increasing. Their clinical importance has led to the discovery of newer biomarkers, such as the soluble source of tumorigenicity 2 (sST2), galectin-3 (Gal-3), growth differentiation factor-15 (GDF-15), and various micro ribonucleic acids (miRNAs). Since cardiac pathophysiology involves a complex interplay between inflammatory, genetic, neurohormonal, and biochemical levels, these biomarkers could be enzymes, hormones, and biologic substances showing cardiac injury, stress, and malfunction. Therefore, multi-marker approaches with different combinations of novel cardiac biomarkers, and continual assessment of cardiac biomarkers are likely to improve cardiac risk prediction, stratification, and overall patient wellbeing. On the other hand, these biomarkers may reflect coexisting or isolated disease processes in different organ systems other than the cardiovascular system. Therefore, knowledge of cardiac biomarkers is imperative. In this article, we have reviewed the role of cardiac biomarkers and their use in the diagnosis and prognosis of various cardiovascular diseases from different investigations conducted in recent years.

Physician discretion is safe and may lower stress test utilization in emergency department chest pain unit patients

INTRODUCTION

Chest pain unit (CPU) observation with defined stress utilization protocols is a common management option for low-risk emergency department patients. We sought to evaluate the safety of a joint emergency medicine and cardiology staffed CPU.

METHODS

Prospective observational trial of consecutive patients admitted to an emergency department CPU was conducted. A standard 6-hour observation protocol was followed by cardiology consultation and stress utilization largely at their discretion. Included patients were at low/intermediate risk by the American Heart Association, had nondiagnostic electrocardiograms, and a normal initial troponin. Excluded patients were those with an acute comorbidity, age >75, and a history of coronary artery disease, or had a coexistent problem restricting 24-hour observation. Primary outcome was 30-day major adverse cardiovascular events-defined as death, nonfatal acute myocardial infarction, revascularization, or out-of-hospital cardiac arrest.

RESULTS

A total of 1063 patients were enrolled over 8 months. The mean age of the patients was 52.8 ± 11.8 years, and 51% (95% confidence interval [CI], 48-54) were female. The mean thrombolysis in myocardial infarction and Diamond & Forrester scores were 0.6% (95% CI, 0.51-0.62) and 33% (95% CI, 31-35), respectively. In all, 51% (95% CI, 48-54) received stress testing (52% nuclear stress, 39% stress echocardiogram, 5% exercise, 4% other). In all, 0.9% patients (n = 10, 95% CI, 0.4-1.5) were diagnosed with a non-ST elevation myocardial infarction and 2.2% (n = 23, 95% CI, 1.3-3) with acute coronary syndrome. There was 1 (95% CI, 0%-0.3%) case of a 30-day major adverse cardiovascular events. The 51% stress test utilization rate was less than the range reported in previous CPU studies (P < 0.05).

CONCLUSIONS

Joint emergency medicine and cardiology management of patients within a CPU protocol is safe, efficacious, and may safely reduce stress testing rates.

Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association

The management of low-risk patients presenting to emergency departments is a common and challenging clinical problem entailing 8 million emergency department visits annually. Although a majority of these patients do not have a life-threatening condition, the clinician must distinguish between those who require urgent treatment of a serious problem and those with more benign entities who do not require admission. Inadvertent discharge of patients with acute coronary syndrome from the emergency department is associated with increased mortality and liability, whereas inappropriate admission of patients without serious disease is neither indicated nor cost-effective. Clinical judgment and basic clinical tools (history, physical examination, and electrocardiogram) remain primary in meeting this challenge and affording early identification of low-risk patients with chest pain. Additionally, established and newer diagnostic methods have extended clinicians' diagnostic capacity in this setting. Low-risk patients presenting with chest pain are increasingly managed in chest pain units in which accelerated diagnostic protocols are performed, comprising serial electrocardiograms and cardiac injury markers to exclude acute coronary syndrome. Patients with negative findings usually complete the accelerated diagnostic protocol with a confirmatory test to exclude ischemia. This is typically an exercise treadmill test or a cardiac imaging study if the exercise treadmill test is not applicable. Rest myocardial perfusion imaging has assumed an important role in this setting. Computed tomography coronary angiography has also shown promise in this setting. A negative accelerated diagnostic protocol evaluation allows discharge, whereas patients with positive findings are admitted. This approach has been found to be safe, accurate, and cost-effective in low-risk patients presenting with chest pain.

A triage algorithm for the rapid clinical assessment and management of emergency department patients presenting with chest pain

This article describes an algorithm for the rapid clinical assessment and evidence-based managemant of patients presenting to the Emergency Department (ED) with chest pain. While broadly applicable, it is specifically designed for use in an ED-based chest pain unit, and incorporates time-sensitive pathways for patients with acute coronary syndromes as well as observation protocols for patients in which the etiology of chest pain is less clear.

Efficacy of coronary revascularization in patients with acute chest pain managed in a chest pain unit

OBJECTIVE

To investigate the safety of discharge of patients deemed at low risk of cardiac events after evaluation in a chest pain unit and to determine the prognostic effect of revascularization of patients deemed at high risk.

PATIENTS AND METHODS

The study population consisted of 1088 patients presenting at the emergency department from January 15, 2001, to September 1, 2006, with chest pain but without ischemia on electrocardiography or troponin elevation. Patients were managed by a chest pain unit protocol that included early exercise testing. Three groups of patients were distinguished: (1) those discharged after exercise testing (424 [39%]); (2) those in whom unstable angina was ruled out after in-hospital evaluation (208 [19%]); and (3) those in whom unstable angina was confirmed or not ruled out (456 [42%]). Of the 456 patients in group 3, 183 (40%) were revascularized at the index episode. The primary end point was the occurrence of myocardial infarction or death within 1 year. Adjustments were made for patient characteristics and a propensity score for revascularization (c statistic [0.83]).

RESULTS

Groups 1 and 2 showed lower rates of the primary end point than group 3 (group 1: 7 [1.7%]; group 2: 1 [0.5%]; group 3: 62 [13.6%]; P=.001). In group 3, revascularization at the index episode did not reduce the primary end point in the univariate (22 [12%] vs 29 [11%]; P=.80) and multivariate (hazard ratio, 1.4; 95% confidence interval, 0.7-2.5; P=.40) analyses. In-hospital revascularization decreased the need for postdischarge revascularization (hazard ratio, 0.3; 95% confidence interval, 0.1-0.7; P=.01).

CONCLUSION

Chest pain unit protocols are associated with safe patient discharge. Although early revascularizations may decrease the need for postdischarge revascularizations, they may not improve 1-year outcomes by reducing the number of myocardial infarctions or deaths.

Unexplained chest pain: when is it panic disorder?

Noncardiac chest pain is a common costly phenomenon in the cardiology setting. Recent research suggests that panic disorder, a highly distressful yet treatable anxiety disorder, occurs in a significant proportion of noncardiac chest pain patients. This article reviews research on the prevalence of panic disorder in patients seen in cardiology settings for unexplained chest pain. Financial, psychosocial, and historical aspects of noncardiac chest pain are described. Panic disorder and the potential consequences of its nonrecognition by physicians are examined. Current psychological and pharmacologic treatments are reviewed. Recommendations on the management of panic patients in the cardiology setting are provided.

Yield of early rest and stress myocardial perfusion single-photon emission computed tomography and electrocardiographic exercise test in patients with atypical chest pain, nondiagnostic electrocardiogram, and negative biochemical markers in the emergency department

There are no studies in which diagnostic yield of early rest myocardial perfusion gated single-photon emission computed tomography (SPECT), electrocardiographic exercise testing, and stress SPECT were compared in patients with atypical chest pain, nondiagnostic electrocardiograms (ECGs), and negative markers of myocardial damage in the emergency department. A prospective study of 96 patients who presented with atypical chest pain and nondiagnostic ECG, but without elevated markers of necrosis, was performed. All underwent rest gated SPECT using technetium-99m methoxyisobutyl isonitrile within 6 hours after pain subsided followed by an electrocardiographic exercise test to obtain stress-rest SPECT images. After 1 year, there were no deaths and coronary artery disease was confirmed in only 5 patients. Negative predictive values of the 3 techniques were high (99%, 96%, and 100%, respectively), but positive predictive values were low (27%, 22%, and 14%, respectively). Sensitivities of early SPECT (80%) and stress SPECT (100%) were higher than for the electrocardiographic exercise test (40%). In conclusion, in patients with atypical chest pain, nondiagnostic ECG, and negative biochemical markers, negative predictive values of the 3 tests analyzed are very high. The sensitivity of radionuclide tests is higher, but their widespread use does not appear warranted because their positive predictive value and incidence of complications is low.

Usefulness of early exercise testing and clinical risk score for prognostic evaluation in chest pain units without preexisting evidence of myocardial ischemia

We investigated whether the result of early exercise testing yields prognostic information in addition to that afforded by a clinical risk score in patients who present with chest pain in the emergency department. The study group consisted of 340 patients without preexisting evidence of myocardial ischemia. A clinical risk score was calculated. Primary (mortality or myocardial infarction) and secondary (mortality, myocardial infarction, or rehospitalization due to unstable angina) end points at 1 year were defined. Patients with a positive exercise test result underwent invasive management. Frequencies of primary (7.4% vs 2.1%, p = 0.06) and secondary (9.3% vs 2.8%, p = 0.04) end points and risk score (1.6 +/- 1.0 vs 1.0 +/- 0.9 points, p = 0.0001) were higher in patients with a positive exercise test result. However, in multivariate analysis, clinical risk score was the only independent predictor for the primary (hazard ratio 2.0, 95% confidence interval 1.2 to 3.2, p = 0.004) and secondary (hazard ratio 1.9, 95% confidence interval 1.2 to 2.9, p = 0.003) end points. In conclusion, if a policy of invasive management is implemented for patients with positive exercise test results, the clinical risk score constitutes the main prognostic predictor of 1-year outcome.

Exercise testing in chest pain units: rationale, implementation, and results

Chest pain units are now established centers for assessment of low-risk patients presenting to the emergency department with symptoms suggestive of acute coronary syndrome. Accelerated diagnostic protocols, of which treadmill testing is a key component, have been developed within these units for efficient evaluation of these patients. Studies of the last decade have established the utility of early exercise testing,which has been safe, accurate, and cost-effective in this setting. Specific diagnostic protocols vary, but most require 6 to 12 hours of observation by serial electrocardiography and cardiac injury markers to exclude infarction and high-risk unstable angina before proceeding to exercise testing. However, in the chest pain unit at UC Davis Medical Center,the approach includes "immediate" treadmill testing without a traditional process to rule out myocardial infarction. Extensive experience has validated this approach in a large, heterogeneous population. The optimal strategy for evaluating low-risk patients presenting to the emergency department with chest pain will continue to evolve based on current research and the development of new methods.

Risk stratification of patients with acute chest pain and normal troponin concentrations

OBJECTIVE

To investigate the outcome of patients with acute chest pain and normal troponin concentrations.

DESIGN

Prospective cohort design.

SETTING

Single centre study in a teaching hospital in Spain.

PATIENTS

609 consecutive patients with chest pain evaluated in the emergency department by clinical history (risk factors and a chest pain score according to pain characteristics), ECG, and early (< 24 hours) exercise testing for low risk patients with physical capacity (n = 283, 46%). All had normal troponin concentrations after serial determination.

MAIN OUTCOME MEASURES

Myocardial infarction or cardiac death during six months of follow up.

RESULTS

29 events were detected (4.8%). No patient with a negative early exercise test (n = 161) had events versus the 6.9% event rate in the remaining patients (p = 0.0001). Four independent predictors were found: chest pain score > or = 11 points (odds ratio (OR) 2.4, 95% confidence interval (CI) 1.1 to 5.5, p = 0.04), diabetes mellitus (OR 2.3, 95% CI 1.1 to 4.7, p = 0.03), previous coronary surgery (OR 3.1, 95% CI 1.3 to 7.6, p = 0.01), and ST segment depression (OR 2.8, 95% CI 1.3 to 6.3, p = 0.003). A risk score proved useful for patient stratification according to the presence of 0-1 (2.7% event rate), 2 (10.2%, p = 0.008), and 3-4 predictors (29.2%, p = 0.0001).

CONCLUSIONS

A negative troponin result does not assure a good prognosis for patients coming to the emergency room with chest pain. Early exercise testing and clinical data should be carefully evaluated for risk stratification.

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.

Cost effectiveness of diagnostic strategies for patients with acute, undifferentiated chest pain

OBJECTIVES

Patients presenting to hospital with acute, undifferentiated chest pain have a low, but important, risk of significant myocardial ischaemia. Potential diagnostic strategies for patients with acute, undifferentiated chest pain vary from low cost, poor effectiveness (discharging all home) to high cost, high effectiveness (admission and intensive investigation). This paper aimed to estimate the relative cost effectiveness of these strategies.

METHODS

Decision analysis modelling was used to measure the incremental cost per quality adjusted year of life (QALY) gained for five potential strategies to diagnose acute undifferentiated chest pain, compared with the next most effective strategy, or a baseline strategy of discharging all patients home without further testing.

RESULTS

Cardiac enzyme testing alone costs pound 17 432/QALY compared with discharge without testing. Adding two to six hours of observation and repeat enzyme testing costs an additional pound 18 567/QALY. Adding exercise testing to this strategy costs pound 28 553/QALY. A strategy of overnight admission, enzyme, and exercise testing has an incremental cost of pound 120 369/QALY, while a strategy consisting of overnight admission without exercise testing is subject to extended dominance. Sensitivity analysis revealed that the results are sensitive to variations in the direct costs of running each strategy and to variation in assumptions regarding the effect of diagnostic testing upon quality of life of those with non-cardiac disease.

CONCLUSION

Observation based strategies incur similar costs per QALY to presently funded interventions for coronary heart disease, while strategies requiring hospital admission may be prohibitively poor value for money. Validation of the true costs and effects of observation based strategies is essential before widespread implementation.

[Value of early exercise stress testing in a chest pain unit protocol]

Early exercise testing (first 24 hours) was evaluated in the stratification of patients seen in the emergency room for chest pain. One hundred and forty-two consecutive patients without ischemia in the ECG or troponin I elevation were included. Ninety-two patients were discharged after the exercise testing (group I, 82 negative and 10 inconclusive test results) and 50 patients were hospitalized (group II, 29 positive and 21 inconclusive test results). In group I, cardiac events (unstable angina and non-fatal infarction) occurred in the next 30 days of follow-up in 2 patients with inconclusive test results; no cardiac events occurred in patients with negative test results. In group II, unstable angina was diagnosed in 30 patients and 3 presented recurrent angina. There were no complications during exercise testing. In conclusion, early exercise testing is safe and useful in the stratification of patients seen in the emergency room for chest pain. Only patients with negative test results should be discharged early.

Immediate exercise testing to evaluate low-risk patients presenting to the emergency department with chest pain

OBJECTIVES

Our purpose was to determine the safety and accuracy of immediate exercise testing in low-risk patients presenting to the emergency department (ED) with chest pain suggestive of a cardiac etiology.

BACKGROUND

Safe, efficient management of low-risk patients presenting to the ED with chest pain is a continuing challenge. We have employed immediate exercise testing to evaluate a large, heterogeneous group of low-risk patients presenting with chest pain.

METHODS

Patients presenting to the ED with chest pain compatible with a cardiac origin and clinical evidence of low risk on initial assessment underwent immediate exercise treadmill testing in our chest pain evaluation unit. Indicators of low clinical risk included no evidence of hemodynamic instability, arrhythmias or electrocardiographic signs of ischemia. Serial measurements of cardiac injury markers were not obtained.

RESULTS

Exercise testing was performed to a sign- or symptom-limited end point in 1,000 patients (520 men, 480 women; age range 31 to 82 years) and was positive for ischemia in 13%, negative in 64% and nondiagnostic in 23% of patients. There were no adverse effects of exercise testing, and all patients with a negative exercise test were discharged directly from the ED. At 30-day follow-up there was no mortality in any of the three groups. Cardiac events in the three groups included: negative group, 1 non-Q-wave myocardial infarction (MI); positive group, 4 non-Q-wave MIs and 12 myocardial revascularizations; nondiagnostic group, 7 myocardial revascularizations.

BACKGROUND

Immediate exercise testing of patients presenting to the ED with chest pain and evidence of low clinical risk is safe and accurate for determining those who require admission and those who can be discharged to further outpatient evaluation.

Critical pathways for patients with acute chest pain at low risk

Critical pathways are predefined protocols that define the crucial steps in evaluating and treating a clinical problem to improve quality of patient care, reduce variability and enhance efficiency. Critical pathways have proliferated for a variety of diagnoses, including evaluation of patients with chest pain, a common and costly complaint. This review will outline the development, implementation, and assessment of critical pathways using as a paradigm our experience with a pathway for patients presenting to the Emergency Department with acute chest pain who are at low risk of myocardial ischemia. The goals of the pathway were to expedite evaluation of low-risk patients and reduce admission rates among these patients and in the cohort overall without compromising outcomes. The pathway was developed by a multidisciplinary team in an iterative process that considered published literature, as well as the experience and consensus of local opinion leaders. Patients at least 30 years old presenting to the Emergency Department of an urban teaching hospital who were pain-free without heart failure or ischemic changes on EKG, but who were not considered appropriate for discharge by the treating physician, were eligible for the critical pathway. The pathway involved one set of creatine kinase-MB enzymes drawn at least 4 hours after pain, a 6 hour observation period after the last episode of pain and exercise testing. Outcomes during evaluation and admission rates were assessed. Clinical outcomes at 7 days and 6 months after evaluation and patient satisfaction at 7 days were also measured. Of 1363 patient visits, 145 (10.6%) were triaged by the pathway: 131 (90.3%) were discharged, 14 (9.7%) were admitted. The overall admission rate decreased from 63% (2898/4595) to 60% (819/1363) [p < 0.05] in comparison to a cohort studied prior to pathway implementation. Pathway patients reported low rates of subsequent cardiac procedures. No deaths or myocardial infarctions were recorded. At 7 days, only 2 respondents (2%) reported going to an Emergency Department since their evaluation. Most respondents (83%) rated their care as very good or excellent. Critical pathways designed to enhance efficiency, reduce variability, and improve the quality of care are becoming increasingly common. Our pathway for evaluation of patients with chest pain at low risk of myocardial ischemia was feasible and safe and was associated with a decline in absolute admission rates. Because of the possibility of concomitant secular trends and the effects of a changing medical environment, further rigorous research on the efficacy of individual pathways is needed.

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.

Selective use of single-photon emission computed tomography myocardial perfusion imaging in a chest pain center

Emergency department chest pain centers (CPCs) vary in their approach to patients with chest pain and nonischemic electrocardiograms (ECG). Although single-photon emission computed tomography (SPECT) myocardial perfusion imaging has been evaluated in this setting, both acutely at rest and after stress, we questioned its application in all patients. We prospectively evaluated the utility of selective SPECT imaging in a CPC (i.e., rest SPECT for ongoing pain, stress SPECT if unable to undergo exercise electrocardiography) and its impact on the overall disposition of all emergency department chest pain patients. Over 3 years, 2,601 patients were evaluated in a CPC (2,211 [85%] were sent home, 390 [15%] were hospitalized). Of 390 CPC patients hospitalized, 182 (47%) were diagnosed with coronary artery disease at the time of hospital discharge. Only 28 patients (1.1%) had an acute myocardial infarction. After 3 years, the proportion of all chest pain patients hospitalized and those diagnosed as "rule-out myocardial infarction" decreased from 53% to 41% and 32% to 18% of all chest pain patients, respectively (both p <0.0001). Overall, 906 patients (35%) required SPECT imaging to complete the CPC evaluation. Had SPECT imaging not been performed selectively, and all 906 patients been admitted, 762 (29%) would have been hospitalized unnecessarily based on the final diagnoses. Alternatively, sending all these patients home would have resulted in 144 (6%) inappropriate discharges of patients with coronary artery disease. A CPC protocol using the selective use of SPECT imaging permits the complete evaluation of all patients in the CPC, significantly reduces hospitalizations for chest pain, and restricts hospital admission to more appropriate patients.

THE CHEST PAIN CENTER IN THE EMERGENCY DEPARTMENT

Despite the improvement of medical treatment for acute coronary syndromes throughout the 20th century, the authors believe that many cases of life-threatening coronary events could be avoided through early detection of CAD and the use of preventive strategies. Establishing chest pain units that are linked to the ED is one excellent strategy to risk-stratify patients with symptoms who are at risk for sustaining an AMI or having lethal arrhythmias. There is a need for more research on chest pain units to determine the value for cost and to further optimize strategies for ACI detection and screening. In EDs with high volumes of chest pain patients, or high pressures to avoid hospital admissions, a planned, systematic, and rapid approach to the treatment of AMI and the diagnosis of chest pain is a rewarding necessity.

Stress testing for risk stratification of patients with low to moderate probability of acute cardiac ischemia

In summary, this article focused on the use of stress testing to risk-stratify patients at the conclusion of their emergency evaluation for ACI. As discussed, those patients in the probably not ACI category require additional risk stratification prior to discharge. It should be kept in mind that patients in this category are heterogeneous, containing subgroups at both higher and lower risk of ACI and cardiac events. The patients with lower pretest probability for ACI may only need exercise testing in the ED. Patients with higher pretest probability should undergo myocardial perfusion or echocardiographic stress testing to maximize diagnostic and prognostic information. Prognostic information is the key to provocative testing in the ED. Prognostic information is the component that will help emergency physicians identify the patients who may be discharged home safely without having to worry about a 6% annual cardiac death rate and a 10% overall death rate over the next 30 months. Stress testing provides this key prognostic data, and it can be obtained in short-stay chest pain observation units in a safe, timely, and cost-effective fashion.

Provocative testing for chest pain

Since the first Chest Pain Center (CPC) was set up in 1981 to speed up the evaluation and treatment of patients with acute myocardial infarction, the original concept has been expanded to include rapid evaluation of chest pain patients with the appropriate streamlining of care and incorporation of the latest in technology. It has also been established that among patients presenting with acute chest pain, a very low-risk group with less than 5% probability of a coronary event can be identified. The recognition of this group could prevent unnecessary admissions, affording more appropriate patient care and improved cost-effectiveness. The efficient management of these chest pain patients requires that there be reductions in: (1) delays in therapy, (2) "soft" admissions, (3) inappropriate dispositions, and (4) cost. With time, provocative testing (PT) for chest pain patients has been brought forward to the frontline. PT methods are now being studied in hundreds of emergency department (ED) patients, followed up over several months to ascertain the predictive value of both positive and negative test results. More and more CPCs are now using PT as part of their management protocol, in terms of decision-making pertaining to prognostification, treatment and disposition. This could be in the form of the ECG graded exercise test (GXT), stress echocardiography (SE) and stress single-photon emission computed tomography (SPECT) radionuclide perfusion imaging. The GXT is fairly widely used currently, SE is gaining popularity and stress radionuclide perfusion imaging will perhaps gain more acceptance as the experience with its use as well as the number of randomized controlled studies increase. As we move into the new millennium, the emergency physicians must familiarize themselves with the latest in the state-of-the-art concepts and technology to render improved, up-to-date and more cost-effective patient care.

Utility and safety of immediate exercise testing of low-risk patients admitted to the hospital with acute chest pain

It is common practice to hospitalize patients with chest pain for a period of observation and to perform further diagnostic evaluation such as exercise treadmill testing (ETT) once acute myocardial infarction (AMI) has been excluded. This study evaluates the safety and efficacy of immediate ETT for patients admitted to the hospital with acute chest pain. One hundred and ninety non-consecutive low-risk patients admitted to the hospital from emergency department with acute chest pain underwent ETT using Bruce protocol immediately on admission to the hospital (median time 165+30 min). Fifty-seven (30%) patients had positive exercise electrocardiograms, 44 (77.2%) of whom had significant coronary narrowing by angiography. An uncomplicated anterior non-Q-wave AMI was diagnosed in one patient. One hundred and eleven (58.4%) patients had negative and 22 (11.6%) patients had non-diagnostic exercise electrocardiograms. Of these 133 patients, 86 (64.7%) were discharged immediately after ETT, 19 (14.3%) were discharged within 24 h, and 28 (21%) were discharged after 24 h of observation. There were no complications from ETT. During the 17+/-6 months follow-up no patients died, and only eight (7.2%) patients with negative ETT experienced a major cardiac event (one AMI and seven angina). In conclusion, our results suggest that immediate ETT of low-risk patients with chest pain who are at sufficient risk to be designated for hospital admission, is effective in further stratifying this group into those who can be safety discharged immediately and those who require hospitalization.

Interpretation of immediate exercise treadmill test: interreader reliability between cardiologist and noncardiologist in a chest pain evaluation unit

STUDY OBJECTIVE

To determine whether attending physicians in a chest pain evaluation unit (CPEU) can perform and interpret exercise testing with the same accuracy as cardiologists.

METHODS

Between January 1996 and November 1998, immediate exercise tests were performed and interpreted by internists with additional training in exercise testing who serve as attending physicians in a CPEU at a large university medical center. For quality assurance, all tests were overread by a cardiologist. Test results were compared for each reader, and all tests with discrepant readings were reinterpreted by an independent cardiologist who was blinded to the previous results. Patients' clinical course was monitored for at least 30 days after exercise testing.

RESULTS

The study group consisted of 645 patients (347 men, 298 women). Discrepant interpretations were found in 11 (1. 7%) patients. The agreement was 98.4% (kappa value 0.9618). The majority of discrepancies were insignificant and were based on subtle differences in the definition of a nondiagnostic test or the degree of ST-segment shift. Of the 11 discordant readings, the blinded cardiologist concurred with 5 (45%) of the CPEU interpretations and 4 (36%) of the cardiologist interpretations. In 2 cases, there was disagreement by all 3 interpreters. There was no cardiac morbidity or mortality of any patient with a discrepant reading.

CONCLUSION

Our results suggest that noncardiologists serving as attending physicians in a CPEU can accurately interpret exercise tests and overreading by cardiologists for quality assurance is unnecessary.

Cardiac troponin T in chest pain unit patients without ischemic electrocardiographic changes: angiographic correlates and long-term clinical outcomes

OBJECTIVES

We prospectively evaluated the relation between cardiac troponin T (cTnT) level, the presence and severity of coronary artery disease (CAD) and long-term prognosis in patients with chest pain but no ischemic electrocardiographic (ECG) changes who had short-term observation.

BACKGROUND

Cardiac TnT is a powerful predictor of future myocardial infarction (MI) and death in patients with ECG evidence of an acute coronary syndrome. However, for patients with chest pain with normal ECGs, it has not been determined whether cTnT elevation is predictive of CAD and a poor long-term prognosis.

METHODS

In 414 consecutive patients with no ischemic ECG changes who were triaged to a chest pain unit, cTnT and creatine kinase, MB fraction (CK-MB) were evaluated > or = 10 h after symptom onset. Patients with adverse cardiac events, including death, MI, unstable angina and heart failure were followed for as long as one year.

RESULTS

A positive (>0.1 ng/ml) cTnT test was detected in 37 patients (8.9%). Coronary artery disease was found in 90% of 30 cTnT-positive patients versus 23% of 144 cTnT-negative patients who underwent angiography (p < 0.001), with multivessel disease in 63% versus 13% (p < 0.001). The cTnT-positive patients had a significantly (p < 0.05) higher percent diameter stenosis and a greater frequency of calcified, complex and occlusive lesions. Follow-up was available in 405 patients (98%). By one year, 59 patients (14.6%) had adverse cardiac events. The cumulative adverse event rate was 32.4% in cTnT-positive patients versus 12.8% in cTnT-negative patients (p = 0.001). After adjustment for baseline clinical characteristics, positive cTnT was a stronger predictor of events (chi-square = 23.56, p = 0.0003) than positive CK-MB (>5 ng/ml) (chi-square = 21.08, p = 0.0008). In a model including both biochemical markers, CK-MB added no predictive information as compared with cTnT alone (chi-square = 23.57, p = 0.0006).

CONCLUSIONS

In a group of patients with chest pain anticipated to have a low prevalence of CAD and a good prognosis, cTnT identifies a subgroup with a high prevalence of extensive and complex CAD and increased risk for long-term adverse outcomes.

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.

An economic analysis of an aggressive diagnostic strategy with single photon emission computed tomography myocardial perfusion imaging and early exercise stress testing in emergency department patients who present with chest pain but nondiagnostic electrocardiograms: results from a randomized trial

STUDY OBJECTIVE

Conventional emergency department testing strategies for patients with chest pain often do not provide unequivocal diagnosis of acute coronary syndromes. This study was conducted to determine whether the routine use of single photon emission computed tomography (SPECT) imaging at rest and early exercise stress testing to assess intermediate-risk patients with chest pain and no ECG evidence of acute ischemia will lead to earlier discharges, more discriminate use of coronary angiography, and an overall reduction in average costs of care with no adverse clinical outcomes.

METHODS

All patients in this study had technetium 99m tetrofosmin SPECT imaging at rest and were randomly assigned to either a conventional (results of the imaging test blinded to the physician) or perfusion imaging-guided (results of the imaging test unblinded to the physician) strategy. Patients in the conventional arm were treated at their physician's discretion. Patients in the perfusion imaging-guided arm were treated according to a predefined protocol based on SPECT imaging test results: coronary angiography after a positive scan result and exercise treadmill testing after a negative scan result. Study endpoints consisted of total in-hospital costs and length of stay. Hospital costs were calculated using hospital department-specific Medicare cost/charge ratios. Length of stay was calculated as total hospital room days billed (regular and intensive care).

RESULTS

We enrolled 46 patients, 9 with acute myocardial infarctions. Patients randomly assigned to the perfusion imaging-guided arm had $1,843 (95% confidence interval [CI] $431 to $6,171) lower median in-hospital costs and 2.0-day (95% CI 1.0 to 3.0 days) shorter median lengths of stay but similar rates of in-hospital and 30-day follow up events as patients in the conventional arm.

CONCLUSION

An ED chest pain diagnostic strategy incorporating acute resting (99m)Tc tetrofosmin SPECT imaging and early exercise stress testing may lead to reduced in-hospital costs and decreased length of stay for patients with acute chest pain and nondiagnostic ECGs.

Emergency department triage strategies for acute chest pain using creatine kinase-MB and troponin I assays: a cost-effectiveness analysis

BACKGROUND

Evaluation of acute chest pain is highly variable.

OBJECTIVE

To evaluate the cost-effectiveness of strategies using cardiac markers and noninvasive tests for myocardial ischemia.

DESIGN

Cost-effectiveness analysis.

DATA SOURCES

Prospective data from 1066 patients with chest pain and from the published literature.

TARGET POPULATION

Patients admitted with acute chest pain.

TIME HORIZON

Lifetime.

PERSPECTIVE

Societal.

INTERVENTIONS

Creatine kinase (CK)-MB mass assay alone; CK-MB mass assay followed by cardiac troponin I assay if the CK-MB value is normal; CK-MB mass assay followed by troponin I assay if the CK-MB value is normal and electrocardiography shows ischemic changes; both CK-MB mass and troponin I assays; and troponin I assay alone. These strategies were evaluated alone or in combination with early exercise testing.

OUTCOME MEASURES

Lifetime cost, life expectancy (in years), and incremental cost-effectiveness.

RESULTS OF BASE-CASE ANALYSIS

For patients 55 to 64 years of age, measurement of CK-MB mass followed by exercise testing in appropriate patients was the most competitive strategy ($43000 per year of life saved). Measurement of CK-MB mass followed by troponin I measurement had an incremental cost-effectiveness ratio of $47400 per year of life saved for patients 65 to 74 years of age; it was also the most cost-effective strategy when early exercise testing could not be performed, CK-MB values were normal, and ischemic changes were seen on electrocardiography.

RESULTS OF SENSITIVITY ANALYSIS

Results were influenced by age, probability of myocardial infarction, and medical costs.

CONCLUSIONS

Measurement of CK-MB mass plus early exercise testing is a cost-effective initial strategy for younger patients and those with a low to moderate probability of myocardial infarction. Troponin I measurement can be a cost-effective second test in higher-risk subsets of patients if the CK-MB level is normal and early exercise testing is not an option.

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.

Immediate exercise testing of low risk patients with known coronary artery disease presenting to the emergency department with chest pain

OBJECTIVES

The purpose of this study was to demonstrate the safety and utility of immediate exercise treadmill testing (IETT) of low risk patients presenting to the emergency department with known coronary artery disease (CAD).

BACKGROUND

More than 70% of the two million patients admitted to U.S. hospitals annually for suspected acute myocardial infarction (AMI) are found not to have had a cardiac event. We have previously demonstrated the safety and efficacy of IETT of selected low risk patients without known CAD presenting to the emergency department with chest pain. This study extends this approach to selected patients with a history of CAD.

METHODS

One hundred patients evaluated by the chest pain emergency room to rule out AMI underwent IETT using a modified Bruce protocol upon admission to the hospital (median time <1 h).

RESULTS

Twenty-three patients (23%) had positive exercise electrocardiograms (ExECGs); an uncomplicated non-Q wave AMI was diagnosed in two patients. Thirty-eight patients (38%) had negative ExECGs and 39 patients (39%) had nondiagnostic ExECGs. Of these 100 patients, 64 were discharged immediately after IETT, 19 were discharged in less than 24 h after negative serial cardiac enzymes and stable electrocardiograms and 17 were discharged after further evaluation and treatment. There were no complications from exercise testing and no late deaths or AMI during six-month follow-up.

CONCLUSIONS

Immediate exercise treadmill testing of low risk patients with chest pain and known CAD is effective in further stratifying this group into patients who can be safely discharged and those who require hospital admission.

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.

Lessons learned from a community hospital chest pain center

The iterative lessons from our studies suggest that creation of a chest pain center alone will not change the practice of chest pain management by most physicians. In 1993 we established a chest pain center; in mid-1995 we established a patient management algorithm directing intermediate-risk patients to the chest pain center rather than admit them to the hospital. The creation of a chest pain center did not reduce the rate of chest pain admission by mid-1995. After the patient management algorithm was created, admittances dropped by a rate of 21% (p <0.001) and chest pain center usage increased by +1,726% (p <0.001). Among the 473 patients treated and discharged in the chest pain center after mid-1995, 333 (70%) were considered intermediate risk. No patient died after discharge from the chest pain center and there was 1 non-Q-wave myocardial infarction. We conclude that a chest pain management algorithm in a chest pain center can be safe, yet effective, for identifying high-risk patients for admission and low-risk patients for discharge.

Long-Term Value of Stress Echocardiography in the Triage of Patients with Atypical Chest Pain Presenting to the Emergency Department

The purpose of this study was to assess the use of stress echocardiography in the triage of patients presenting to the emergency department with atypical chest pain. We hypothesized that a negative stress echocardiogram would identify patients with a very low risk for future cardiac events, thus reducing the requirement for unnecessary hospitalizations. Stress testing was performed in 105 patients presenting with atypical chest pain, no prior history of coronary artery disease, a nondiagnostic electrocardiogram (ECG), negative serial creatine phosphokinase level at 0 and 4 hours, and baseline normal echocardiograms. Cardiac stress was invoked using an exercise protocol in 75 (71%) patients and intravenous dobutamine in 30 (29%) patients, with ECG and echocardiography results analyzed separately. Cardiac events (myocardial infarction, coronary revascularization, and cardiac death) were noted in 7 (7%) patients with a mean follow-up of 2.8 +/- 1.3 years. Univariate analysis identified five predictors of future cardiac events, but only stress-induced wall motion abnormalities were found to be predictive with multivariate analysis. Kaplan-Meier estimate of cumulative event-free survival for cardiac events at 3 years was 99% for a negative stress echocardiogram (no stress-induced wall motion abnormalities) compared with 95% for stress ECG (< 1-mm ST segment depression). The event-free rate of a positive stress echocardiogram and stress ECG was 25% and 63%, respectively. We conclude that stress echocardiography can be performed safely in patients presenting with atypical chest pain. A negative stress echocardiogram carries an excellent 3-year prognosis and thus identifies patients who may forgo hospital admission and further cardiovascular workup.

Use of electron-beam computed tomography in the evaluation of chest pain patients in the emergency department

STUDY OBJECTIVE

We sought to determine whether electron-beam computed tomography (EBCT) could be used as a triage tool in the emergency department for patients with angina-like chest pain, no known history of coronary disease, normal or indeterminate ECG findings, and normal initial cardiac enzyme concentrations.

METHODS

We conducted a prospective observational study of 105 patients admitted between December 1995 and October 1997 to the ED of a large tertiary care hospital with 70,000 annual ED visits. The study group was comprised of women aged 40 to 65 years and men aged 30 to 55 years who presented with angina-like chest pain requiring admission to the hospital or chest pain observation unit. All patients underwent EBCT of the coronary arteries, along with other cardiac testing as deemed necessary by staff physicians.

RESULTS

Of the 105 patients, 100 underwent other cardiac testing during hospitalization. Evaluation included treadmill exercise testing in 58, coronary angiography in 25, radionuclide stress testing in 19, and echocardiography in 11. Results of EBCT and cardiac testing were negative for both in 53 patients (53%), positive for both in 14 (14%), positive for tomography and negative for cardiac testing in 32 (32%), and negative for tomography and positive for cardiac testing in only 1 patient. This positive test result, on a treadmill exercise test, was ruled a false positive by an independent staff cardiologist. Two other female patients with normal exercise sestamibi or coronary angiography and EBCT findings also had false-positive treadmill exercise results. The sensitivity of EBCT was 100% (95% confidence interval, 77% to 100%), with a negative predictive value of 100% (95% confidence interval, 94% to 100%). Specificity was 63% (95% confidence interval, 54% to 75%).

CONCLUSION

EBCT is a rapid and efficient screening tool for patients admitted to the ED with angina-like chest pain, normal cardiac enzyme concentrations, indeterminate ECG findings, and no history of coronary artery disease. Our study suggests that patients with normal initial cardiac enzyme concentrations, normal or indeterminate ECG findings, and negative results on EBCT may be safely discharged from the ED without further testing or observation. Larger studies are required to confirm this conclusion.

Cardiac troponin I as a predictor of major cardiac events in emergency department patients with acute chest pain

OBJECTIVES

We sought to evaluate the diagnostic and prognostic value of cardiac troponin I (cTnI) in emergency department (ED) patients with chest pain.

BACKGROUND

Although cTnI has been shown to correlate with an increased risk for complications in patients with unstable angina, the prognostic significance of this assay in the heterogeneous population of patients who present to the ED with chest pain is unclear.

METHODS

cTnI and creatine kinase-MB fraction (CK-MB) mass concentration were collected serially during the first 48 h from onset of symptoms in 1,047 patients > or =30 years old admitted for acute chest pain. Sensitivity, specificity and receiver operating characteristic curves were calculated for cTnI and CK-MB collected in the first 24 h.

RESULTS

The sensitivity, specificity and positive predictive value of cTnI for major cardiac events were 47%, 80% and 19%, respectively. Among patients were who ruled out for myocardial infarction, cTnI was elevated in 26% who had major cardiac complications compared with 5% for CK-MB; the positive predictive value for an abnormal cTnI result was 8%. Elevated cTnI in the presence of ischemia on the electrocardiogram was associated with an adjusted odds ratio of 1.8 (95% confidence interval 1.1 to 2.9) for major cardiac events within 72 h. Among patients without a myocardial infarction or unstable angina, cTnI was not an independent correlate of complications.

CONCLUSIONS

In patients presenting to the ED with acute chest pain, cTnI was an independent predictor of major cardiac events, However, the positive predictive value of an abnormal assay result was not high in this heterogeneous cohort.