What is the diagnosis and management approach for an adult with a history of cardiovascular disease or risk factors presenting with new, worsening, or rest chest pain, suspected of having unstable angina?

Diagnosis of Unstable Angina

Unstable angina is diagnosed by the presence of prolonged chest pain at rest (>20 minutes), accelerating tempo of ischemic symptoms, or new-onset severe angina (CCS Class III or IV within 2 weeks to 2 months), combined with ECG changes and negative cardiac biomarkers. 1

Clinical Presentation

The diagnosis requires recognition of three key patterns 2:

• Prolonged rest pain (>20 minutes) that is ongoing or recently resolved 2, 1
• Accelerating angina with increasing frequency, severity, or duration, or angina provoked at a lower threshold than previously 2
• New-onset severe angina (CCS Class III or IV) within the preceding 2 weeks to 2 months 2

The American Heart Association emphasizes that unstable angina represents acute severe chest pain at rest followed by recurrent symptoms in patients with recent normal functional capacity 1. This recurrent, fluctuating nature distinguishes it from stable angina 1.

Risk Stratification Framework

Immediate risk stratification is essential and determines management intensity. The ACC/AHA provides a validated three-tier system 2:

High-Risk Features (require urgent invasive evaluation)

• Pain characteristics: Prolonged ongoing rest pain (>20 minutes) 2
• History: Accelerating tempo of symptoms in preceding 48 hours 2
• Clinical findings: Pulmonary edema likely due to ischemia, new or worsening mitral regurgitation murmur, S3 gallop or new/worsening rales, hypotension, bradycardia, or tachycardia 2
• ECG: Angina at rest with transient ST-segment changes >0.5 mm, new or presumed new bundle branch block, or sustained ventricular tachycardia 2
• Cardiac markers: Elevated troponin T, troponin I, or CK-MB (TnT or TnI >0.1 ng/mL) 2

Critical distinction: If troponins are elevated, the diagnosis shifts from unstable angina to NSTEMI, though initial management remains identical 1, 3.

Intermediate-Risk Features

• History: Prior MI, peripheral or cerebrovascular disease, CABG, or prior aspirin use 2
• Pain: Prolonged rest angina (>20 minutes) now resolved with moderate/high likelihood of CAD, rest angina (<20 minutes) relieved with rest or sublingual nitroglycerin, nocturnal angina, or new-onset/progressive CCS Class III-IV angina in previous 2 weeks 2
• Age: >70 years (or >75 years in some classifications) 2, 4
• ECG: T-wave changes, pathological Q waves, or resting ST-depression <1 mm in multiple lead groups 2
• Cardiac markers: Slightly elevated troponin (TnT >0.01 but <0.1 ng/mL) 2

Low-Risk Features

• Pain: Increased angina frequency, severity, or duration; angina provoked at lower threshold; new-onset angina with onset 2 weeks to 2 months before presentation 2
• ECG: Normal or unchanged 2
• Cardiac markers: Normal 2

Diagnostic Workup

Immediate Evaluation (within 10 minutes)

All patients with suspected unstable angina require urgent transfer to the emergency department with immediate ECG within 10 minutes and cardiac troponin measurement as soon as possible. 1, 4

The ECG is critical to exclude STEMI (ST-elevation >1 mm requires immediate reperfusion therapy) 5. Patients without ST-elevation have a mixture of unstable angina and NSTEMI that cannot be distinguished until troponin results return 1, 3, 5.

Serial Assessment

• Cardiac biomarkers: Serial troponin measurements at presentation, 3-6 hours, and potentially 12 hours to definitively exclude NSTEMI 1, 3
• Continuous ECG monitoring: To detect transient ST-segment changes during recurrent pain episodes 2

Risk-Based Imaging Strategy

For high-risk patients (age >75, prior unstable angina, regional wall motion abnormalities on echo), proceed directly to invasive coronary angiography rather than non-invasive testing. 4 CT coronary angiography has no role when ischemic heart disease is already documented 4.

For intermediate- or low-risk patients, functional testing (stress echo or nuclear imaging) can be performed after stabilization to assess for inducible ischemia 5.

Key Diagnostic Pitfalls

Do not confuse unstable angina with stable angina that has worsened due to extracardiac precipitants (anemia, infection, thyrotoxicosis) 2. These patients have chronic stable angina with increased supply/demand mismatch and should be managed per stable ischemic heart disease guidelines once the precipitant is addressed 2.

Persistence of pain despite hospital admission and medical therapy is the single most important predictor of adverse outcomes (MI or death) and mandates urgent invasive evaluation 6, 7. Other clinical features have limited predictive value in isolation 6.

Regional wall motion abnormalities on echocardiogram suggest prior myocardial injury and ongoing ischemia, necessitating aggressive evaluation to prevent further events 4.

Management Algorithm Based on Risk

High-Risk Patients

1. Immediate medical therapy: Aspirin 162-325 mg loading dose, sublingual nitroglycerin for acute pain, heparin (unfractionated or low-molecular-weight), and high-intensity statin (atorvastatin 80 mg) 4, 5
2. Invasive coronary angiography within 24-48 hours 4, 5
3. Revascularization (PCI or CABG) based on anatomy 4, 8

Intermediate/Low-Risk Patients

1. Chest pain unit strategy with serial ECGs, cardiac markers, and functional testing 5
2. Safe discharge home if all testing is normal 5
3. Elective angiography or intensive medical therapy if testing is abnormal 5

Beta-blockers should be used cautiously in patients with bradycardia; consider long-acting nitrates as an alternative antianginal agent 4, 8, 9. Metoprolol can cause severe bradycardia, heart block, and cardiac arrest, particularly in patients with conduction disorders 9.