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

Evaluation of chest pain in low-risk patients presenting to the emergency department: the role of immediate exercise testing

STUDY OBJECTIVES

To determine the safety and utility of immediate exercise testing in the evaluation of low-risk patients presenting to the emergency department with chest pain and its applicability to a heterogeneous population of men and women.

METHODS

We conducted a prospective study of the safety and utility of immediate exercise testing in low-risk patients, as indicated by clinical and ECG criteria. The study group was large, heterogeneous, and included patients with a history of coronary artery disease. The patients were treated at a large, university medical center. Exercise testing (immediate exercise treadmill testing) was performed by internists, and cardiac serum enzyme levels were not measured before the exercise test.

RESULTS

A total of 212 patients (121 men, 91 women) underwent exercise testing with no adverse effects. Twenty-eight (13%) patients had positive results on exercise ECGs. Twenty-three of the latter had further evaluation that revealed evidence of coronary artery disease in 13 (57%). Fifty-nine percent (125/212) of patients had negative exercise test results and 28% (59/212) had nondiagnostic tests. All patients with negative test results and 93% with nondiagnostic test results were discharged directly from the ED. Thirty-day follow-up was achieved in 201 (95%) patients and revealed no mortality in any of the patients in the three groups. One patient with a positive exercise test result returned to the ED within 30 days with mild congestive heart failure.

CONCLUSION

Our results in this patient population support the safety and utility of immediate exercise testing of low-risk patients who present to the ED.

Panic disorder in coronary artery disease patients with noncardiac chest pain

In this study we address the following questions: (1) What percentage of coronary artery disease (CAD) patients that present with chest pain, but whose symptoms cannot be fully explained by their cardiac status, suffer from panic disorder (PD)? (2) How do patients with both CAD and PD compare to patients without CAD and to patients without either PD or CAD in terms of psychological distress? Four hundred forty-one consecutive walk-in emergency department patients with chest pain underwent a structured psychiatric interview (ADIS-R) and completed psychological scales. Fifty-seven percent (250 of 441) of these patients were diagnosed as having noncardiac chest pain and constituted this study's sample. A total of 30% (74 of 250) of noncardiac chest pain patients had a documented history of CAD. Thirty-four percent (25 of 74) of CAD patients met criteria for PD. Patients with both PD and CAD displayed significantly more psychological distress than CAD patients without PD and patients with neither CAD nor PD. However, they did not differ from non-CAD patients with PD. PD is highly prevalent in patients with CAD that are discharged with noncardiac diagnoses. The psychological distress in these patients appears to be related to the panic syndrome and not to the presence of the cardiac condition.

Dobutamine stress tele-echocardiography for evaluation of emergency department patients with chest pain

OBJECTIVES

The practically and accuracy of dobutamine stress tele-echocardiography (DSTE) were assessed in patients presenting to the emergency department with chest pain.

BACKGROUND

Many patients evaluated for chest pain in the emergency department (ED) are admitted to the hospital needlessly because of the difficulty in differentiating noncardiac chest pain from myocardial ischemia.

METHODS

One hundred sixty-three patients with no evidence of myocardial infarction on initial blood studies or the electrocardiogram who were recommended for hospital admission to rule out myocardial infarction or myocardial ischemia were enrolled in this four-phase study. Rest echocardiography was performed in the ED, and the images were transmitted to a cardiologist for interpretation. If the results were normal, DSTE was then administered by a trained nurse. In the first three phases, all patients were admitted for observation regardless of the results of DSTE. In the fourth phase, those having normal DSTE results were able to be released.

RESULTS

The test was completed within an average of 5.4 h of presentation to the ED. The sensitivity and specificity of DSTE versus clinical and cardiac catheterization findings were 89.5% and 88.9%, respectively, with a negative predictive value for DSTE of 98.5%. Patients experienced frequent mild side effects (54.7%), but few (6.3%) caused the test to be discontinued prematurely. In phase 4 of the study, 72% of those slated for hospital admission because of cardiac risk factors and chest pain suggesting myocardial ischemia were discharged after normal DSTE results.

CONCLUSIONS

The use of DSTE in the evaluation of patients presenting with chest pain may improve screening for those who can be safely released from the ED.

Safety evaluation and confidence intervals when the number of observed events is small or zero

A common objective in many clinical studies is to determine the safety of a diagnostic test or therapeutic intervention. In these evaluations, serious adverse effects are either rare or not encountered. In this setting, the estimation of the confidence interval (CI) for the unknown proportion of adverse events has special importance. When no adverse events are encountered, commonly used approximate methods for calculating CIs cannot be applied, and such information is not commonly reported. Furthermore, when only a few adverse events are encountered, the approximate methods for calculation of CIs can be applied, but are neither appropriate nor accurate. In both situations, CIs should be computed with the use of the exact binomial distribution. We discuss the need for such estimation and provide correct methods and rules of thumb for quick computations of accurate approximations of the 95% and 99.9% CIs when the observed number of adverse events is zero.

Role of nuclear cardiology in the evaluation of acute coronary syndromes

Over the last 20 years, nuclear cardiology has become a mainstay in the evaluation of ischemic heart disease. In the setting of acute coronary syndromes (myocardial infarction or unstable angina), myocardial perfusion imaging has emerged as an important tool in assessing the functional significance of angiographic coronary stenoses, evaluating the efficacy of therapeutic interventions, and risk-stratifying patients in the postinfarction period. Recent literature has demonstrated the diagnostic and prognostic value, as well as the cost-effectiveness, of perfusion imaging in acute chest pain syndromes and the diagnostic superiority of perfusion imaging compared with two-dimensional echocardiography. Acute perfusion imaging is now being included in the algorithm for the triage and management of acute chest pain syndromes. Emergency physicians are increasingly using nuclear cardiac imaging modalities for aid in the evaluation of patients who present with chest pain of uncertain origin.

Rapid bedside coronary angiography with a portable fluoroscopic imaging system

The ability to perform coronary angiography rapidly at the bedside has multiple potential applications. This study was designed to determine whether a novel portable angiographic system (OEC Medical Systems, series 9600, Salt Lake City, Utah) is capable of producing high-quality angiograms. In 29 patients (70 vessels) undergoing elective catheterization in a conventional fixed laboratory (Siemens HICOR, Erlangen, Germany), we compared images obtained with the portable system to those from conventional fixed system. The portable system was 100% accurate in detecting both insignificant narrowing as well as significant stenoses (> 50% narrowing). There was complete concordance between systems for lesion location, TIMI flow, and collaterals. Thirty-two stenoses were analyzed in detail. Both quantitative and qualitative percent stenosis demonstrated similar value for lesion severity with both systems (R = 0.95, Kappa = 0.77, P < 0.001, respectively). Accuracy of lesion morphology by the portable system was similar to the fixed system (calcification 80%, eccentricity 92%). These findings demonstrate that a portable imaging system can produce high-quality coronary angiograms.

Differences between chest pain observation service patients and admitted "rule-out myocardial infarction" patients

OBJECTIVE

To compare and contrast the patient characteristics of ED patients at low risk for acute cardiac ischemia who were assigned to a chest pain observation service vs those admitted to a monitored inpatient bed for "rule-out acute myocardial infarction" (R/O MI).

METHODS

This was a retrospective, cross-sectional comparison of adult patients considered at relatively low risk for cardiac ischemia and who were evaluated in 1 of 2 settings: a short-term observation service and an inpatient monitored bed. All patients had an ED final diagnosis of "chest pain," "R/O MI," or "unstable angina" during the 7-month study period. Demographic features and presenting clinical features were examined as a function of site of patient evaluation.

RESULTS

Of 531 study patients, 265 (50%) were assigned to the observation service. Younger age (OR = 1.75, 95% CI 1.26, 2.44, for each decrement of 20 years), the complaint of "chest pain" (OR = 2.35, 95% CI 1.34, 4.12), and the absence of prior known coronary artery disease (OR = 1.64, 95% CI 1.13, 2.38) were the principal independent factors associated with assignment to a chest pain observation service bed.

CONCLUSIONS

Patients evaluated in a chest pain observation service appear to have different clinical characteristics than other individuals admitted to a monitored inpatient bed for "R/O MI." Investigators should address differences in clinical characteristics when making outcome comparisons between these 2 patient groups.

Evaluation of chest pain in the emergency department

The evaluation of chest pain in the emergency setting should be systematic, risk based, and goal driven. An effective program must be able to evaluate all patients with equal thoroughness under the assumption that any patient with chest pain could potentially be having an MI. The initial evaluation is based on the history, a focused physical examination, and the ECG. This information is sufficient to categorize patients into groups at high, moderate, and low risk. Table 14 is a template for a comprehensive chest-pain evaluation program. Patients at high risk need rapid initiation of appropriate therapy: thrombolytics or primary angioplasty for the patients with MIs or aspirin/heparin for the patients with unstable angina. Patients at moderate risk need to have an acute coronary syndrome ruled in or out expediently and additional comorbidities addressed before discharge. Patients at low risk also need to be evaluated, and once the likelihood of an unstable acute coronary syndrome is eliminated, they can be discharged with further evaluation performed as outpatients. Subsequent evaluation should attempt to assign a definitive diagnosis while also addressing issues specific to risk reduction, such as cholesterol lowering and smoking cessation. It is well documented that 4% to 5% of patients with MIs are inadvertently missed during the initial evaluation. This number is surprisingly consistent among many studies using various protocols and suggests that an initial evaluation limited to the history, physical examination, and ECG will fail to identify the small number of these patients who otherwise appear at low risk. The solution is to improve the sensitivity of the evaluation process to identify these patients. It appears that more than simple observation is required, and at the present time, no simple laboratory test can meet this need. However, success has been reported with a number of strategies including emergency imaging with either radionuclides such as sestamibi or echocardiography. Early provocative testing, either stress or pharmaceutic, may also be effective. The added value of these tests is only in their use as part of a systematic protocol for the evaluation of all patients with acute chest pain. The initial evaluation of the patient with chest pain should always consider cardiac ischemia as the cause, even in those with more atypical symptoms in whom a cardiac origin is considered less likely. The explicit goals for the evaluation of acute chest pain should be to reduce the time to treat MIs and to reduce the inadvertent discharge of patients with occult acute coronary syndromes. All physicians should become familiar with appropriate risk stratification of patients with acute chest pain. Systematic strategies must be in place to assure rapid and consistent identification of all patients and the expedient initiation of treatment for those patients with acute coronary syndromes. These strategies should include additional methods of identifying acute coronary syndromes in patients initially appearing as at moderate or low risk to assure that no unstable patients are discharged. All patients should be followed up closely until the cardiovascular evaluation is completed and, when possible, a definitive diagnosis is determined. Finally, this must be done efficiently, cost-effectively, and in a manner that will result in an overall improvement in patient care.

Feasibility of a rapid diagnostic protocol for an emergency department chest pain unit

STUDY OBJECTIVE

To evaluate the applicability of a short-stay protocol for exclusion of acute ischemic heart disease without hospital admission and to analyze these results in the context of a conceptual model.

METHODS

An observational study of patients who presented with chest pain to the emergency department of an 886-bed inner-city municipal hospital and who needed hospital admission to rule out acute myocardial infarction (AMI). Patients were assessed by ED attending physicians to determine eligibility for an alternative, 12-hour protocol in an ED chest pain observation unit (CPOU) followed by immediate exercise testing. Outcome measures were proportion of patients eligible for the short-stay protocol, risk factor profile, and reasons for exclusion.

RESULTS

Of 500 patients screened, 446 had sufficient data points to determine protocol eligibility. Of these, 238 (53.3%; 95% confidence interval [CI], 48.7% to 57.9%) were found to have low probability for AMI. After study exclusion criteria were applied to the patient cohort, 63 patients (14.1%; 95% CI, 10.9% to 17.3%) were eligible for the protocol. The most common reasons for exclusion were history of coronary artery disease (46%) and inability to perform an interpretable exercise tolerance test (42%).

CONCLUSION

Although most admitted patients with chest pain (53%) were at low probability for AMI, only a minority (14%) were eligible for a short-stay protocol that required patients to be free of known coronary artery disease and able to perform an exercise tolerance test. Factors affecting the operations and efficiency of a CPOU include clinical characteristics of the target patient population, protocol tests used, and hospital occupancy and reimbursement patterns.

Cost-effectiveness of mandatory stress testing in chest pain center patients

STUDY OBJECTIVE

To determine whether emergency patients with acute chest pain and low suspicion of acute myocardial infarction (AMI) can be managed cost-effectively and safely in a dedicated chest pain center (CPC) that incorporates mandatory stress testing.

METHODS

We assembled a prospective observational case series of consecutive adult patients transferred from the emergency department to a nine-bed, 23-hour CPC in a 564-bed community hospital from January 13 through May 31, 1994. In our institution, all emergency patients with acute nontraumatic chest pain of unclear origin, suggestive of myocardial ischemia but with a low probability of AMI, are transferred to the CPC for further evaluation. All patients in whom AMI is ruled out undergo individually appropriate cardiac diagnostic testing in accordance with CPC clinical guidelines. Patients with end-stage coronary artery disease transferred to the CPC for a "rule-out" protocol only did not undergo further diagnostic testing. Admitted and discharged patients were followed through chart review and telephone survey, respectively.

RESULTS

Of the 502 patients transferred to the CPC, 477 (95%) completed follow-up at 14 days. Four hundred ten (86%) were discharged home. Those discharged after diagnostic evaluation yielded negative findings had 100% survival and zero diagnosis of AMI at 5-month follow-up. Overall mortality and incidence of AMI on long-term follow-up for all patients transferred to the CPC were .4% and .2%, respectively. Sixty-seven patients (13%) were admitted from the CPC, of whom 44 (66%) had a final diagnosis of ischemic heart disease (IHD) or AMI. Twenty-four patients with IHD (55%; 6% of stress-tested group) were identified only on further stress testing. Of these patients, seven underwent percutaneous transluminal coronary angioplasty or coronary artery bypass grafting during hospitalization. All were discharged home without major morbidity. Four hundred twenty-four patients (84%) underwent stress testing. The cost of mandatory stress testing to identify one patient with IHD after AMI was ruled out was $3,125. An average cost-per-case savings of 62% was achieved for each patient transferred to the CPC who would have been hospitalized before the inception of the CPC.

CONCLUSION

Mandatory stress testing is a safe, cost-effective, and valuable diagnostic and prognostic tool in CPC patients.

The feasibility of dobutamine stress echocardiography in the emergency department with telemedicine interpretation

Dobutamine stress echocardiography (DSE) was performed on 26 patients admitted for chest pain deemed at low risk for myocardial infarction. Pharmacologic stress in the emergency department on a 24-hour basis was administered by nurses and echocardiographic ultrasonographers with electrocardiograms and echocardiograms being interpreted through telemedicine relay by an off-site cardiologist. Target heart rate was achieved in 84% of patients with an average peak dobutamine dose of 48 microg/kg/min. Echocardiographic transmission to the cardiologist over standard telephone lines took 9 minutes per quad-screen cine-loop display. The entire protocol added 2.2 hours to the emergency room evaluation. The one patient out of 26 who had incipient myocardial infarction was diagnosed by resting echocardiography. The remaining 25 patients were found clinically to have no infarction or ischemia. Of these, 22 out of 25 had normal DSE in the emergency department; three had wall motion abnormalities on peak stress images. Another three patients had other cardiac diseases documented by echocardiography. Evaluation of chest pain on a 24-hour basis with DSE with telemedicine interpretation appears to be a rapid and safe means of screening patients at low risk in the emergency department. Further experience with this modality is needed before all patients should be enrolled or early discharge of patients on the basis of DSE can be advised.