SYMPOSIUM ON CARDIOVASCULAR DISEASESEmergency Department and Office-Based Evaluation of Patients With Chest Pain
Section snippets
INITIAL RISK STRATIFICATION
The goal of the initial evaluation of a patient who presents to an outpatient setting with potential ACS has changed from diagnosis to risk stratification. In many cases, the approach is similar for patients being evaluated in the office and the ED and should include a history, physical examination, and ECG. Patients should be classified into 1 of 4 categories11: (1) those with evidence of ST-segment elevation on initial ECG; (2) those without ST-segment elevation but who are at high risk on
ELECTROCARDIOGRAPHY
Whether a patient presents to an office or an ED, the initial ECG is the easiest, simplest, most important tool for early risk stratification. Current recommendations indicate that it should be performed within 10 minutes of ED presentation11 and may best be considered one of the “vital signs” for patients with chest pain. All offices should have this capability as well as a mechanism to provide rapid interpretation. The presence of ST-segment elevation should prompt consideration for immediate
PATIENT HISTORY
Despite recent advances in newer diagnostic techniques, the history remains critically important in the initial evaluation of patients with chest pain. Because objective evidence of ACS is present in only a few patients, it is used to stratify them into higher- and lower-risk groups, allowing the appropriate level of additional diagnostic testing to be targeted.
Patients often do not consider their symptoms as “pain”; therefore, questions are better targeted at a description of their
PHYSICAL EXAMINATION
Findings on physical examination are usually normal in most low-risk patients undergoing an ACS evaluation. However, certain findings can be useful for risk stratification and for determining symptom etiology.11 Important findings identifying high-risk patients include chronic heart failure (CHF) and hemodynamic instability (low blood pressure, elevated heart rate). Abnormal vital signs are recognized high-risk findings included in a number of scoring systems that stratify patients with ACS for
BIOMARKERS
Current recommendations advise that all patients with suspected ACS should undergo serial cardiac biomarker sampling.11, 36, 37 If baseline data are negative, further sampling should be obtained 6 to 8 hours later depending on symptom onset. Creatine kinase and creatine kinase MB were the traditional markers for identifying patients with MI; however, because of their less than optimal sensitivity and specificity, current recommendations indicate troponin as the preferred biomarker. Troponin is
CLINICAL RISK SCORES
A recommended approach to risk stratification for patients with potential ACS is the application of scoring systems based on the history and initial clinical presentation. The simplest scheme relies on 1 set of cardiac markers, ECG findings, and history of CAD (Figure 1). If findings and history are unremarkable, the patient can be considered low risk, with a probability of MI of less than 5% to 6%.15 Some of the first validated chest pain algorithms were derived by Goldman and colleagues.15, 30
DIFFERENTIAL DIAGNOSIS
When patients present to the ED with chest pain, differentiating ischemic from nonischemic causes is difficult and frequently the major focus of the evaluation. Because morbidity is high if a cardiac etiology is not diagnosed early, the overlap of symptoms necessitates an initial diagnostic strategy that assumes symptoms are cardiac-related unless other causes are obviously apparent. However, a high awareness of the many other causes of chest pain is needed (Table 2) to guide the treatment of
ADDITIONAL INITIAL DIAGNOSTIC TESTING
Current American College of Cardiology (ACC)/American Heart Association (AHA) guidelines recommend that all patients with suspected ACS undergo ECG and cardiac biomarker testing. Recommendations from the American College of Radiology assigned a value of 9 (most appropriate) for chest radiographic evaluation of patients with acute chest pain who have a low probability of disease.68 Of the 5000 ED-obtained chest radiographs reviewed in one large study, including 629 obtained for a primary symptom
CHEST PAIN UNITS AND ADPs
Chest pain units were developed as a mechanism for the rapid assessment and exclusion of ACS in low-risk patients in a cost-effective manner that avoids routine admission and prolonged hospital stays. These units provide an integrated, protocol-driven approach to further stratify low-risk patients by short-term observation and serial assessment of clinical variables, ECG findings, and cardiac biomarker levels.9, 11, 15, 70 They are usually directed by an emergency physician, but their
EXERCISE TREADMILL TESTING
Standard exercise treadmill testing (ETT) is a cornerstone of risk stratification in CPUs.11, 71 Its advantages include relatively modest cost, availability, ease of performance, and its ability to provide important prognostic information. Criteria for selecting this test are the patient's ability to exercise and normal findings on a baseline ECG that allows interpretation of exercise-induced ST-segment alterations. If findings on ECG are not interpretable, the addition of cardiac imaging is
OUTPATIENT STRESS TESTING
Ideally, ADPs would be available at all times; however, this is not feasible for many institutions. An alternative strategy, recognized by ACC/AHA guidelines,11 approves outpatient ETT in selected low-risk patients with chest pain, provided they meet the following criteria: (1) no further ischemic chest discomfort, (2) normal or nonischemic findings on initial and follow-up ECG, and (3) normal cardiac biomarker measurements. Observational data have found this strategy to be safe, with no
ACUTE CARDIAC IMAGING
In some institutions, additional diagnostic imaging is used to rapidly stratify the risk of patients before completing serial marker sampling and provocative testing. These include acute rest MPI, computed tomographic coronary angiography (CTCA), echocardiography, and cardiac magnetic resonance imaging. The advantage of adding early imaging (MPI, magnetic resonance imaging, echocardiography) is that abnormal perfusion and wall motion occur within seconds of ischemia onset, so that MI can be
ACUTE MPI
Acute rest MPI using technetium agents has been shown to accurately identify low- and high-risk patients who present with chest pain.87 A perfusion defect indicates acute ischemia, acute infarction, or old infarction. Patients can be injected while they are experiencing symptoms and undergo delayed imaging after stabilization. The images obtained provide a “snapshot” of myocardial perfusion at the time of injection. Normal perfusion is associated with very low clinical risk, allowing patients
COMPUTED TOMOGRAPHIC CORONARY ANGIOGRAPHY
Compared with other imaging techniques, CTCA provides anatomic rather than functional information regarding coronary patency. Application of computed tomography (CT) to coronary artery imaging has become feasible with the advent of multislice CT. The acquisition of CT data is synchronized to the surface ECG and collected for 10 to 20 seconds while patients hold their breath during injection of contrast medium. As with the validation of other tests, most studies have examined the diagnostic
ECHOCARDIOGRAPHY
On the basis of its high degree of reliability for assessing cardiac wall motion, echocardiography has been used for diagnosis and risk assessment in patients presenting to the ED with symptoms suggesting ACS for more than 30 years. Regional wall motion abnormalities induced by ischemia are detected by echocardiography almost immediately after its onset and precede ECG alterations and symptoms.104 Factors that determine the diagnostic accuracy of rest echocardiography to detect ACS include
CARDIAC MAGNETIC RESONANCE IMAGING
Cardiac magnetic resonance imaging (CMRI) has superior image quality to most other noninvasive imaging, allowing assessment of perfusion, function, and valvular abnormalities during a single imaging session; however, imaging of coronary arteries remains inferior to CTCA.110 In patients with potential ACS, CMRI may provide “one-stop shopping.” If findings on initial rest imaging are negative, stress CMRI with adenosine could be performed immediately, eliminating the need for later testing. A
TRANSITION INTO THE OUTPATIENT SETTING
The chest pain evaluation may represent a potential “teachable moment,” as it may be the first and only contact with a physician for a number of years, particularly for the younger patient who is relatively healthy. Therefore, in patients in whom ACS has been excluded, focusing on primary prevention and addressing risk factors are important. Many patients who have undergone a CPU evaluation will have had lipids sampled; therefore, early follow-up with a primary care physician for subsequent
OUTPATIENT OFFICE MANAGEMENT
Patients who call the office reporting active chest pain, including those with atypical symptoms, should be directed immediately to an ED that can initiate reperfusion therapy. Although patients with CAD are more likely to be seen in cardiology offices, such patients are increasingly being seen by their primary care physician. Because patients may develop symptoms at the time of or shortly after arrival, all offices should have automatic external defibrillators and be capable of performing
CONCLUSION
The initial evaluation of the patient with acute chest pain should be prompt and include ECG, measurement of a set of initial cardiac markers, and history taking and physical examination that focus on hemodynamic variables and evidence of systolic dysfunction. In those in whom the risk is moderate to high on the basis of the preceding criteria, further evaluation in an inpatient setting (either step-down or intensive care unit) is usually required. For most patients in whom none of these
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On completion of this article, you should be able to (1) recognize common causes of troponin elevations not related to acute coronary syndrome, (2) identify characteristics associated with high and low risk of ischemic complications in patients with possible myocardial infarction, and (3) describe the advantages and disadvantages of imaging tests (rest myocardial perfusion imaging, computed tomographic coronary angiography, and cardiac magnetic resonance imaging) for the early diagnosis and risk stratification of low-risk patients with chest pain.