When a patient comes in the emergency department with chest pain, the doctor, in the first ten minutes makes a provisional diagnosis of the cause of the chest pain.
Based on the history, physical exam, and immediate electrocardiogram he might diagnosis ST elevation myocardial infarction (STEMI).
The evidence might indicate likely non-ST elevation myocardial infarction (NSTEMI) or unstable angina. He won’t be able to say which until troponin blood tests are drawn and analyzed initially and hours later. If the troponin level is above normal, the patient is suffering a non-ST elevation myocardial infarction.
If the troponin levels are normal, then the patient has unstable angina.
The initial history, physical, and ECG may allow the doctor to determine that an Acute Coronary Syndrome (meaning a STEMI, an NSTEMI, or unstable angina) is very unlikely. Usually the doctor will not make this diagnosis unless there is strong evidence that the chest pain is not due to an Acute Coronary Syndrome.
If the doctor assigns patient to ST elevation myocardial infarction then he or she will be prepared for emergency coronary angiography and revascularization with angioplasty/stent or coronary artery bypass surgery.
If the doctor assigns the patient to the non-ST elevation myocardial/unstable angina group (he can’t know which of the two possibilities it is until the troponin results come back or other evidence point to NSTEMI or to unstable angina) then the following takes place:
Initial treatment consists of oxygen if the O2 saturation is less than 90%, nitroglycerin for pain, and/or morphine for severe pain.
The next step, usually done initially when the patient is getting his first ECG, is to draw blood tests. The blood tests include a troponin T or tronin I, a complete blood count, and a complete chemistry profile.
Other blood tests are often also ordered initially depending on what other concerns the doctor has. The BNP blood test can suggest heart failure if elevated . A high D-dimer blood test would suggest pulmonary embolus or deep vein thrombosis.
Because the ECG can change, repeated ECGs or continuous ST segment monitoring are indicated.
The ESC guidelines* recommend that every patient receive an echocardiogram, an ultrasound heart scan, to look for decreased pumping function of the heart and to look for structural heart abnormalties like heart valve disease.
The patient should be evaluated with the GRACE score which is available at
http://www.outcomes-umassmed.org/grace/acs_risk/acs_risk_content.html and gives an estimate of the patient risk of in-hospital death or in-hospital death and MI. The initial score also gives us the patient’s risk of death or death and MI at 6 months.
The GRACE risk model is repeated at discharge with some different parameters included that reflect the course of the patient’s hospital therapy.
The ESC guidelines also recommend calculating a CRUSADE registry bleeding risk score as bleeding markedly increases unfavorable outcomes in NSTEMI or unstable angina.
Mortality using the GRACE risk score at admission is classified as low (less than 1%), intermediate (1 to 3%), or high (greater than 3%).
Of course clinical judgment is also important in estimating the risk.
Patients who are at very high risk (continuing angina not responding to medical treatment, unstable vital signs, and dangerous heart rhythms) need immediate coronary angiography regardless of the troponin levels or ECG findings.
The ESC guidelines* summary for when and if coronary angiography is indicated based on risk follows:
“In summary, timing of angiography and revascularization should be based on patient risk profile. Patients at very high risk (as defined above) should be considered for urgent coronary angiography
(less than 2 h). In patients at high risk with a GRACE risk score of greater than 140 or with at least one major high risk criterion, an early invasive strategy within 24 h appears to be the reasonable time window. This implies expedited transfer for patients admitted to hospitals without on-site catheterization facilities. In lower risk subsets with a GRACE risk score of less than 140 but with at least one high risk criterion (Table 9), the invasive evaluation can be delayed without increased risk but should be performed during the same hospital stay, preferably within 72 h of admission. In such patients, immediate transfer is not mandatory, but should be organized within 72 h (e.g. diabetic patients). In other low risk patients without recurrent symptoms a non-invasive assessment of inducible ischaemia should be performed before hospital discharge. Coronary angiography should be performed if the results are positive for reversible ischaemia.”
According to Table 5 in the ESC guidelines low risk is less than 1% and corresponds to less than or equal to a score of 108. Intermediate risk is 1 to 3% and corresponds to a Grace risk score of between 109 to 140 points. High risk of in-hospital death is greater than 3% and corresponds to a Grace risk score of greater than 140 points.
The reason for the above paragraph is that the online Grace Risk Score Calculator will give you a morality % rather than the numerical risk score.
*ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation 2011 at http://www.escardio.org/guidelines-surveys/esc-guidelines/GuidelinesDocuments/Guidelines-NSTE-ACS-FT.pdf.