Over 8 million people seek emergency department (ED) attention every year for assessment of chest pain. The American Heart Association recently issued a scientific statement to give guidance on rapid, effective approaches to the assessment of such patients.
Conclusions
Most patients who present with chest pain to ED settings do not have acute ischemia: Less than 5% have an ST segment elevation myocardial infarction, and up to 25% can have a non–ST segment elevation event. Up to 7% of patients with chest pain after cocaine exposure have infarctions.
William E. Golden (left) and Robert H. Hopkins
At the same time, up to 2% of patients with acute coronary syndromes (ACS) are inadvertently discharged from EDs with potentially twice the risk-adjusted mortality of patients admitted for management of acute ischemia.
Symptom-limited treadmill stress testing is felt to be safe at 8-12 hours for low- and intermediate-risk chest pain patients who have normal baseline EKGs and capacity to exercise, and are not taking digoxin.
Ischemia induced during stress protocols for echocardiography or myocardial perfusion imaging (MPI) indicates impaired coronary perfusion in the face of increased oxygen demand. MPI also can be used to detect rest ischemia indicating impaired regional myocardial perfusion, a hallmark of the ACS.
Both stress echocardiography (sensitivity: 86%; specificity: 81%) and MPI (87%; 73%) are more effective in detecting coronary artery disease than exercise treadmill testing (70%; 75%). However, while MPI is an effective test, it is associated with considerable radiation exposure.
Use of pharmacologic agents can be substituted for exercise in patients unable to exercise according to modified Bruce protocols. Dobutamine increases myocardial demand. Vasodilators such as adenosine, dipyridamole, and regadenoson simulate exercise stress conditions by dilating coronary arteries and creating maldistribution of myocardial perfusion.
A major clinical trial is ongoing to assess the value of CT coronary arteriography, which has a very high negative predictive value, in assessing chest pain syndrome patients in the ED.
As many as 20%-25% of patients with negative chest pain unit evaluations present again for similar evaluations.
Implementation
The goal of ED evaluation of chest pain is the exclusion of ACS and other urgent conditions as appropriate diagnoses. Assessment of the presence of coronary artery disease is best handled in other settings. Experience with chest pain units and accelerated diagnostic protocols have provided effective evidence-based strategies for triaging these patients.
While classic anginal symptoms can aid in the evaluation of acute chest pain, ACS patients can present with atypical or confusing complaints and require care assessment by evaluating health professionals. Nausea and diaphoresis associated with severe chest pain are highly associated with acute ischemia, but elderly patients may have predominantly respiratory complaints.
Patients with sudden-onset, severe chest pain should be considered for pneumothorax, pulmonary embolus, or aortic dissection.
Patients at low risk for myocardial infarction (less than 5%) should be identified by current symptoms, past history, and a new electrocardiogram. These patients have normal EKGs, normal initial cardiac injury lab findings, and stable hemodynamics and cardiac rhythm. The Thrombolysis in Myocardial Infarction (TIMI) risk score is widely used, but has not performed consistently for low-risk populations.
Patients with acute ST segment elevation frequently have near-total or total coronary occlusion and are candidates for reperfusion interventions.
Patients who present during the first 6 hours of chest pain onset and who have negative cardiac markers should be retested after 8 hours to validate the negative results. Newer assays of troponin have good sensitivity and specificity, and are preferred over creatine kinase MB and myoglobin measurement. Laboratories should return results within an hour of specimen sampling or else point-of-service assessment should be considered. B-type natriuretic peptide, while useful for congestive heart failure evaluation, does not offer value in the assessment of acute ischemia.
For patients with indeterminant initial presentations, chest pain protocols can help structure observation. Exercise stress testing is optional in patients with cocaine-related chest pain after a negative period of observation and testing.
Patients who have no additional chest discomfort, undiagnostic initial and follow-up EKGs, and negative injury lab values can be discharged without stress testing for outpatient follow-up investigations.
Repeat treadmill stress testing has limited value in patients with a previous negative evaluation for chest pain in an emergency setting. These patients may eventually require coronary arteriography as negative cardiac caths, in comparison to noninvasive evaluation, reduce repeat ED chest pain evaluations by more than 50%.