Workup for Unstable Angina
Patients presenting with suspected unstable angina require immediate hospitalization with continuous ECG monitoring, serial cardiac biomarkers (troponin) every 6-12 hours, a 12-lead ECG within 10 minutes of presentation, basic laboratory tests including complete blood count and metabolic panel, and risk stratification to determine the need for early invasive coronary angiography versus initial conservative management. 1
Immediate Assessment Upon Presentation
Initial Diagnostic Tests
- 12-lead ECG must be obtained within 10 minutes of presentation to identify ST-segment changes, T-wave abnormalities, or other ischemic patterns 2, 1
- Cardiac biomarkers (troponin I or T) should be measured immediately at presentation and serially every 6-12 hours to detect myocardial necrosis 3, 1
- Continuous ECG monitoring is mandatory to detect ongoing ischemia, arrhythmias, and sudden ventricular fibrillation, which is the major preventable cause of early death 2, 1
Essential Laboratory Work
- Complete blood count to assess for anemia or thrombocytopenia 1
- Basic metabolic panel including serum creatinine (important for anticoagulation dosing decisions) 2
- Lipid profile (can be obtained during hospitalization) 2
- Blood glucose, particularly in diabetic patients 2
Risk Stratification
Clinical Risk Assessment Tools
The TIMI Risk Score is a validated 7-point system that predicts adverse outcomes and guides management decisions 2. One point is assigned for each of the following:
- Age ≥65 years
- ≥3 coronary risk factors
- Prior angiographic coronary obstruction
- ST-segment deviation on ECG
- ≥2 angina events within 24 hours
- Aspirin use within 7 days
- Elevated cardiac markers
Risk of death, MI, or recurrent severe ischemia ranges from 5% (score 0-1) to 41% (score 6-7) 2.
High-Risk Features Requiring Early Invasive Strategy
Patients with any of the following should undergo coronary angiography within 48 hours, ideally as soon as possible 3, 1:
- Recurrent ischemia despite medical therapy
- Elevated troponin levels
- Hemodynamic instability
- Major arrhythmias (sustained ventricular tachycardia)
- Early post-infarction unstable angina
- Diabetes mellitus with other high-risk features 1
Low-Risk Patients
Patients without recurrent chest pain, without ST-segment changes, and with normal serial troponins may be considered for an initially conservative strategy with noninvasive testing 2.
Noninvasive Testing (For Low-to-Intermediate Risk Patients)
Stress Testing Options
For patients who stabilize on medical therapy and are not proceeding to immediate angiography 4, 5:
- Exercise stress testing with ECG monitoring can be performed before discharge or within 72 hours of presentation in low-risk patients 5
- Myocardial perfusion imaging (nuclear stress test) provides additional prognostic information beyond clinical variables 4
- Stress echocardiography can assess for inducible wall motion abnormalities 4
Important caveat: Stress testing should only be performed in patients who have been pain-free and clinically stable for at least 12-24 hours on medical therapy 5. Never perform stress testing in patients with ongoing symptoms or high-risk features.
Coronary Angiography Decision-Making
Indications for Urgent/Early Angiography
Coronary angiography should be performed during the initial hospitalization for 2:
- High-risk patients based on clinical features or risk scores
- Patients with recurrent ischemia despite optimal medical therapy
- Patients with hemodynamic instability or heart failure
- Patients with sustained ventricular arrhythmias
- Patients with prior revascularization (low threshold for angiography) 2
Conservative Strategy
Patients at low risk who remain stable on medical therapy can be managed conservatively with noninvasive testing, but should undergo angiography if they develop recurrent symptoms or have high-risk findings on stress testing 2.
Common Pitfalls to Avoid
- Do not delay treatment while waiting for cardiac biomarker results; initial troponin may be negative in early presentation 1
- Do not discharge patients prematurely; observation for at least 6-12 hours with serial ECGs and biomarkers is essential even in apparent low-risk patients 6
- Do not perform stress testing in patients with ongoing chest pain, hemodynamic instability, or high-risk features—these patients need angiography 5
- Do not assume normal coronary arteries exclude ACS; coronary vasospasm and microvascular dysfunction can cause unstable angina 6
- Do not use thrombolytic therapy in unstable angina/NSTEMI without ST-segment elevation, as it is not beneficial and may be harmful 6, 5
Post-Stabilization Evaluation
Once patients are stabilized on medical therapy, the workup should include 2:
- Assessment of left ventricular function (echocardiography)
- Evaluation for diabetes if not previously diagnosed
- Comprehensive lipid panel
- Assessment of other cardiovascular risk factors
The decision between early invasive strategy versus initial conservative management with selective angiography should be based on the patient's risk profile, with higher-risk patients benefiting from early angiography and revascularization 2, 1.