Emergency cardiac stress testing in the evaluation of emergency department patients with atypical chest pain

ORIGINAL CONTRIBUTION chest pain stress tests

From the Departments of Emergency Medicine* and Internal Medicine, Division of Cardiology,* Northeastern Ohio Universities College of Medicine and Akron City Hospital, Akron, Ohio.

Received for publication April 6, 1992. Revision received November 30, 1992. Accepted for publication December 7, 1992.

This study was supported by a grant from the Akron City Hospital Foundation.

Emergency Cardiac Stress Testing in the

Evaluation of Emergency Department Patients

With Atypical Chest Pain

John R Kerns, DO* Ted F Shaub, MD, FACC ~

Phil B Fontanarosa, MD, FACEP t

Study objectives: To determine the feasibility, safety, and reliability of emergency cardiac treadmill exercise stress testing (CTEST) in the evaluation of emergency department patients with atypical chest pain.

Design: Thirty-two patients with atypical chest pain, normal ECGs, and risk factor stratification having low-probability of coronary artery disease were evaluated prospectively using outpatient, emergency CTEST. Study patients were compared with a retrospectively selected sample of admitted patients diagnosed with atypical chest pain who met the study criteria and were evaluated with WEST as inpatients. All patients had f011ow-up at three and six months after evaluation.

Setting: University-affiliated community teaching hospital with 65,000 annual ED visits.

Results: All patients had normal CTEST. No patient had evidence of coronary artery disease, myocardial infarction, or sudden death during the follow-up period. The average length of stay was 5.5 hours for emergency CTEST patients versus two days for inpatients. The average patient charge was $467 for ED evaluation with emergency CTEST versus $2,340 for inpatient evaluation.

Conclusion: Emergency CTEST is a safe, efficient, cost-effective; and practical method of evaluating selected ED patients with chest pain. It is a useful aid for clinical decision making and may help to prevent unnecessary hospital admissions.

[Kerns JR, Shaub TF, Fontanarosa PB: Emergency cardiac stress testing in the evaluation of emergency department patients with atypical chest pain. Ann Emerg MedMay 1993;22:794-798.]

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CARDIAC STRESS TESTING Kerns, Shaub & Fontanarosa

INTRODUCTION

Acute chest pain is a common complaint of adults presenting to the emergency department. The evaluation of patients with chest discomfort may pose a significant challenge for emergency physicians because of the wide variety of potential causes for the pain. 1,2 The diagnosis is made even more problematic by the overlap of symptoms caused by ischemic cardiac disease and nonischemic etiologies, along with the lack of readily available diagnostic studies that enable precise identification of the cause of pain. 3-5

Within the clinical spectrum of acute chest pain is a subset of patients in whom the quality, duration, associated symptoms, and precipitating factors are not characteristic for cardiac pain. These patients usually have a nonspecific pattern of chest discomfort, a normal ECG, and a low clinical likelihood of cardiac disease, and they often are classified as having "atypical chest pain. ''6-1o Because the possibility of a cardiac disease cannot be excluded with certainty, patients with atypical chest pain usually are hospitalized for cardiac monitoring and further evaluation. As part of their diagnostic workup, patients with atypical chest pain routinely undergo cardiac treadmill exercise stress testing (CTEST).

We hypothesized that selected ED patients with atypical chest pain and a low pretest probability of coronary artery disease could be evaluated safely by emergency CTEST. We postulated that emergency CTEST would aid the emergency physician in distinguishing accurately between cardiac and noncardiac causes of acute chest pain in these patients, thereby avoiding hospitalization. Therefore, we designed this prospective, preliminary study with the objectives of determining the feasibility and usefulness of ED CTEST in the evaluation of selected patients with atypical chest pain and of comparing the safety, outcome, and cost of emergency CTEST with the inpatient evaluation of atypical chest pain.

MATERIALS AND METHODS

Patients presenting to the ED between March 1990 and February 1991 with acute chest pain were eligible for the study. Inclusion criteria were chest pain suggestive of cardiac origin but not typical for angina by virtue of quality, duration, precipitating factors, and associated symptoms; men between the ages of 18 tO 39 years and women between the ages of 18 to 4-9 years; none or one of the cardiac risk factors of more than a ten pack-year smoking history, prior documentation of total serum cholesterol of more than 260 mg/dL, or family history

(ie, grandparents, parents, siblings) of myocardial infarction occurring before the age of 60 years; and normal ECG as determined by the interpretation of the attending cardiologist and defined by the Minnesota Code Criteria. 11

Patients with any of the following criteria were excluded: moderate suspicion of acute myocardial infarction or ischemic heart disease (based on history or ECG findings); two or more cardiac risk factors; prior documentation of coronary artery disease; history of insulin-dependent or non-insulin-dependent diabetes mellitus; currently taking a-blockers, calcium channel blockers, or digoxin; prior treatment for hypertension or ED blood pressure readings revealing systolic pressure of more than 160 mm Hg or diastolic pressure of more than 95 mm Hg; cocaine use during the preceding 24 hours; or physical l{mitations precluding performance of CTEST, such as severe arthritis or lower extremity injuries. At our hospital, CTEST is available on weekdays between 8:00 AM and 5:00 PM. Eligible patients presenting to the ED at other times were considered for inclusion in the study if they consented to a period of ED observation until CTEST was available and their primary care physician was in agreement. Patients who presented to the ED on Friday or Saturday evenings or nights were excluded from the study.

After informed consent was obtained, the patient was transported to the cardiology laboratory. CTEST was performed using the Bruce protocol with age-predicted target heart rate. 12 After completion of CTEST, the patient was returned to the ED. The attending cardiologist interpreted CTEST and notified the emergency physician of the result. Patient disposition was determined by the emergency physician after discussion with the patient's primary care physician, cardiologist, or both. All patients, their primary care physicians, or both were contacted by telephone at three and six months after CTEST. A predesigned questionnaire was used to identify patients who subsequently were diagnosed with coronary artery disease by positive repeat stress test or cardiac catheterization, sustained myocardial infarction, or experienced sudden death.

To compare outpatient, emergency CTEST with the inpatient evaluation of atypical chest pain, a comparison group was identified using a computerized search of hospital medical records. The inpatient group consisted of patients who were hospitalized during the study period with a primary discharge diagnosis of atypical or noncardiac chest pain, met the inclusion and exclusion criteria for the emergency CTEST group, and had inpatient CTEST performed. The medical records of eligible patients were reviewed retrospectively for clinical findings, pattern of chest pain, risk factors, CTEST results, outcome, length

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CARDIAC STRESS TESTING Kerns, 5haub & Fontanarosa

of hospital stay, and patient charges. These patients, their primary care physicians, or both were contacted for telephone follow-up using the same questionnaire that was used in the study group.

This study was approved by the hospital medical research committee and investigational review board.

R E S U L T S

The study group consisted of 32 patients--20 men (62.5%) and 12 women (37.5%) (Table). Mean age was 35 years (range, 20 to 48 years). Fifteen patients (47%) had no cardiac risk factors, five (16%) were smokers, and one (3%) had a positive family history of coronary artery disease. Eighteen patients (67%) described their chest pain as pressure, heaviness, or tightness. Chest pain was nonexertional in 29 patients (91%), and the duration of pain ranged from five minutes to one week. All patients in the study group satisfactorily completed emergency CTEST, and all studies were interpreted as normal. No patient exhibited symptoms or ECG changes during or after the procedure that were suggestive of cardiac ischemia. The average patient charge, including CTEST, was $467. The average length of ED visit was 5.5 hours (range, 2.5 to 12 hours). For the majority of patients, CTEST added approximately 2.5 hours to their ED stay Patients who presented to the ED during the night and were observed until CTEST was available had an average of nine hours added to the ED stay.

After emergency CTEST, all patients were discharged from the ED and referred for follow-up with their primary care physician. At six-month follow-up, no patient had developed documented coronary artery disease, sustained myocardial infarction, o r experienced sudden death.

During the study period, 50 patients were hospitalized and discharged with a final diagnosis of atypical chest pain. Twenty-four of these patients were excluded from the comparison group because of more than one cardiac risk factor (12 patients), hypertension (eight), CTEST not performed (three), or exceeding age limits of the study (one).

The comparison group consisted of the remaining 26 patients--13 men (50%) and 13 women (50%), with a mean age of 40 years (range, 30 to 48 years) (Table). Eight patients (31%) had no cardiac risk factors, nine (34%) were smokers, and seven (27%) had a positiv e family history of coronary artery disease. Eighteen patients (54%) described their chest pain as pressure, heaviness, or tightness. Chest pain was nonexertional i n 17 patients (65%). The duration of pain ranged from several minutes to one

week. All patients had normal CTEST. The average length of hospital stay was two days (range, one to five days), and the average patient charge, including CTEST, was $2,340. During the follow-up period, no patient developed documented coronary artery disease, sustained myocardial infarction, or experienced sudden death.

D I S C U S S I O N

Determining whether acute chest pain represents cardiac or noncardiac disease is one of the most difficult clinical challenges for emergency physicians. Chest pain of cardiac ischemia may produce a wide spectrum of symptoms and clinical findings. 13-15 Moreover , although many other acute conditions can cause chest pain that mimics ischemic cardiac pain, most represent less serious, lower- risk disorders that may be evaluated safely and adequately on an outpatient basis.2,15 Conversely, when acute chest discomfort is the result of cardiac ischemia or coronary artery disease, an accurate diagnosis is critical to reduce the substantial risks of morbidity and mortality, to insti- tute necessary therapy with thrombolytic agents or inva- sive cardiac procedures, and to use coronary care units and cardiac monitoring facilities appropriately.

Previous studies have examined a variety of diagnostic modalities to aid in the ED evaluation of patients with acute chest pain. Scoring systems and computerized pro- grams based on clinical findings and ECG interpretation

Table. Characteristics of ED patients with emergency CTEST and. admitted patients with inpatient CTEST

ED Study Group Inpatient Group (N = 32) (N = 26)

Mean age (yr)(range) Men Women Risk factors

None Smoking history Family history of myocardial infarction

Hypercholesterolemia 0haracter of pain

Tightness, heaviness, pressure Sharp Dull, knotlike Burning Not specified

Exertional pain Nonexertional pain Mean hospital stay (range) Average patient charge

35 (20 - 48) 40 (30 - 48) 20 (62.5%) 13 (50%) 12 (37,5%} 13 (50%)

15 (47%) 9 (31%) 5 (16%) 9 (34%)

1 (3%) 7 (27%) 11 (34%) 2 (8%)

18 (67%) 18 (54%) 5 (16%) 6 (23%) 4(12%) 2(11%) 2 (6%) 1 (4%) 3 (9%) 2 (8%) 3 (9%} 9 (35%)

29 (91%) 17 (65%) 5.5 hr(2.5- 12 hr) 2.0 days (1 - 5 days) $467 $2,340

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have been developed to identify high-risk patients with acute ischemic chest pain. ~6,17 Rapid assays for creatine kinase,18,19 creatine kinase-MB isoenzymes,2O, 2~ and serum myoglobin levels 22 appear promising as diagnostic aids for acute myocardial infarction but have limited usefulness as markers for noninfarction cardiac chest pain. Two-dimensional echocardiography, 2B thallium scintigra- phy, 24 and serum lipoprotein analysis 15 are among the other studies proposed to assist clinicians in the evaluation of acute chest pain, but these also have insufficient sensitivity for detecting coronary artery disease.

Despite the potential usefulness of these diagnostic and prognostic studies in aiding in the clinical assessment of patients with chest pain, CTEST remains the most readily available and most frequently used method of identifying patients with suspected coronary artery disease. 25 The usefulness and accuracy of CTEST as a diagnostic test for the presence of coronary artery disease depend on the patient population that is tested. 26-3o Even though CTEST may not identify all patients with coronary artery disease, it is sufficiently sensitive to detect patients with coronary artery disease severe enough to cause significant chest pain or unstable anginal syndromes. 26-30

In a recent report, Tsakonis and colleagues 3~ used CTEST to evaluate 28 patients with unexplained chest pain and normal ECGs. CTEST was performed within the first several hours after hospital arrival. All patients were admitted, discharged after a full inpatient workup, and followed for a mean of 6.1 months (range, one to 12 months). The authors suggested that CTEST "may assist the emergency physician with a discharge decision" and that "an exercise test administered during the ED visit which is negative can preclude unnecessary hospitalization," even though the study involved only admitted patients.

Our preliminary study demonstrates that ED-initiated, outpatient exercise treadmill stress testing is a feasible, useful, and practical method of evaluating selected, low- risk, young patients with atypical chest pain. Patients in the study group safely completed emergency CTEST in a reasonably short time and were able to be discharged from the ED. During the six-month follow-up, no patient developed evidence of coronary artery disease, sustained myocardial infarction, or experienced sudden death. The data also suggest that CTEST is efficient and cost effective and may prevent unnecessary admissions to cardiac monitoring units. When compared with admitted patients evaluated for atypical chest pain, outpatient CTEST resulted in substantially shorter lengths of stay (5.5 hours versus two days) and lower patient charges ($467 versus $2,340).

This study had several limitations. First, for reasons of patient safety, we used specific entry criteria to reduce the pretest likelihood of coronary artery disease> Consequently, our study group has selection bias imposed by age restric- tions and number of cardiac risk factors. Combining inclusion criteria and risk factors with Bayes' theorem and multiple discriminant function analysis, we estimated that in these selected patients, the pretest probability of CAD was approximately 20% and that a normally interpreted CTEST represented a less than 10% likelihood of significant CAD. 28,32-34 Second, we included only patients with normal ECGs to reduce the likelihood of false-positive CTEST results.35, 36 We also excluded patients taking medications that could blunt a tachycardic response (eg, g-blockers, digitalis) and those with hypertension to reduce the likelihood of false-negative CTEST. Third, because the majority of study patients were enrolled during the CTEST availability (ie, daytime hours), we may have introduced some sample bias by excluding patients with nocturnal anginal syndromes. Finally, the use of a retrospectively selected comparison group limits its simi- larity with the study group and limits the extent of valid comparisons that can be drawn between the two patient samples. Selecting patients with a discharge diagnosis of atypical or noncardiac chest pain most likely excluded those with abnormal inpatient CTEST or other significant cardiac disorders.

However, despite these limitations and based on the data in our study, ED-initiated outpatient CTEST appears to be a useful technique for evaluating selected ED patients with atypical chest pain. Advantages of the procedure are that CTEST meets current medical standards for safely evaluating patients with atypical chest pain; is an efficient, cost-effective, and convenient procedure; can provide security and reassurance for the patient; and may help alleviate unnecessary admissions to coronary care and telemetry units. Even though the sample size is small, this study also demonstrates that an integrated, multi- disciplinary approach is a feasible and effective method of evaluating patients with atypical chest pain. Cooperation among cardiologists, emergency physicians, and primary care physicians, along with the availability of timely CTEST and its interpretation, are essential elements for the success of this assessment technique.

Future research examining the precise role of emergency CTEST in evaluating ED patients with chest pain is war- ranted. Studies evaluating patients with higher pretest probabilities for coronary artery disease, such as older patients and those with increased risk factors, would be of interest. Prospective investigations of CTEST in a deci-

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sion analysis model would help to establish the accuracy and usefulness of CTEST in identifying ED patients with atypical chest pain and significant coronary artery disease.

CONCLUSION

Thirty-two patients with atypical chest pain, no or one cardiac risk factor, and normal ECGs were evaluated prospectively with emergency CTEST. All patients had normal CTEST, and no patient demonstrated clinical evidence of coronary artery disease, myocardial infarction, or sudden death in the six-month follow-up period. Emergency CTEST is a safe, reliable, efficient, and cost- effective method for evaluating selected ED patients with acute chest pain. Although this procedure requires addi- tional effort and cooperation among cardiologists, emergency physicians, and primary care physicians, outpatient emergency CTEST is a useful aid for clinical decision making regarding ED patients with chest pain and may help to prevent unnecessary admissions and overuse of specialized hospital resources.

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Address for reprints:

Phil B Fontanarosa, MD, FACEP

Department of Emergency Medicine

Akron City Hospital

525 East Market Street

Akron, Ohio 44309

4 0 /7 9 8 ANNALS OF EMERGENCY MEDICINE 22:5 MAY 1993

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Emergency cardiac stress testing in the evaluation of emergency department patients with atypical chest pain