What is the diagnostic and treatment approach for unstable angina?

Diagnostic and Treatment Approach for Unstable Angina

Immediate Diagnosis and Risk Assessment

All patients with suspected unstable angina require immediate hospitalization with continuous ECG monitoring in a coronary care unit or specialized chest pain unit. 1, 2, 3

Key Diagnostic Features

The diagnosis is primarily clinical, based on three characteristic presentations 1, 4:

• Rest angina: Chest pain occurring at rest, typically lasting >20 minutes 3, 4
• New-onset severe angina: Angina beginning within the past 2 months that is severe and frequent 4
• Crescendo angina: Previously stable angina that has become more frequent, longer in duration, or occurs with less exertion 1, 4

Initial Diagnostic Workup

• 12-lead ECG during symptoms: Transient ST-segment changes (≥0.05 mV) that develop during chest pain and resolve when asymptomatic strongly indicate acute ischemia 1
• Cardiac biomarkers: Obtain troponin levels immediately; elevated cardiac-specific troponin (cTnT or cTnI) identifies approximately 30% of patients without CK-MB elevation and indicates higher risk 1
• Continuous ECG monitoring: Essential for detecting ischemia and arrhythmias 1, 3
• Exclude secondary causes: Search for precipitating factors including uncontrolled hypertension, thyrotoxicosis, anemia, fever, arrhythmias, pulmonary embolism, aortic stenosis, or hypertrophic cardiomyopathy 1

Risk Stratification

High-risk features requiring urgent intervention 1, 3:

• Persistent or recurrent ischemic pain despite intensive medical therapy
• ST-segment depression ≥1 mm or dynamic ST-segment changes
• Elevated troponin levels
• Hemodynamic instability or hypotension
• Pulmonary edema, new S3 gallop, or new/worsening mitral regurgitation
• Sustained ventricular tachycardia or high-degree AV block

Intermediate-risk features 1:

• Rest angina resolved with medical therapy
• Normal or unchanged ECG
• Age >70 years, prior MI, or known coronary disease

Low-risk features 1:

• No rest or nocturnal angina
• Normal or unchanged ECG
• No elevation of cardiac biomarkers

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Immediate Medical Management

First-Line Therapies (Administer Immediately)

Antiplatelet therapy 2, 3:

• Aspirin 162-325 mg: Administer immediately and continue 75-150 mg daily indefinitely 2, 3
• Clopidogrel: Give loading dose unless urgent CABG planned within 24 hours; continue 75 mg daily for at least 12 months 2, 3

Anticoagulation (choose one) 2, 3:

• Enoxaparin (preferred over unfractionated heparin unless CABG planned within 24 hours) 2
• Unfractionated heparin, fondaparinux, or bivalirudin are alternatives 3

Anti-ischemic therapy 1, 2:

• Nitroglycerin: Sublingual 0.4 mg every 5 minutes for total of 3 doses; if symptoms persist, start intravenous nitroglycerin 1
• Beta-blockers: Oral therapy should be initiated within first 24 hours in hemodynamically stable patients without heart failure signs, low-output state, increased cardiogenic shock risk, PR interval >0.24 seconds, second/third-degree heart block, or active asthma 1, 5
  • Critical warning: Never abruptly discontinue beta-blockers in coronary artery disease patients—severe exacerbation of angina, MI, and ventricular arrhythmias can occur 5
• Calcium channel blockers: Use nondihydropyridine agents (verapamil or diltiazem) only if beta-blockers are contraindicated 1

Supplemental oxygen: Administer if arterial saturation <90% or respiratory distress present 1, 3

High-intensity statin therapy: Initiate before hospital discharge to improve outcomes and increase long-term adherence 2, 3

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Invasive Strategy Selection

High-Risk Patients (Early Invasive Strategy)

Perform coronary angiography within 4-24 hours for patients with 1, 2, 3:

• Refractory angina or hemodynamic instability
• Electrical instability (sustained ventricular tachycardia)
• Elevated cardiac biomarkers
• Dynamic ST-segment changes
• Early post-infarction angina

Evidence: The TACTICS-TIMI 18 trial demonstrated that early invasive strategy reduced death, MI, or rehospitalization at 6 months (15.9% vs 19.4%) compared to conservative strategy 2

Intermediate-Risk Patients

Early invasive strategy within 12-24 hours is reasonable for initially stabilized patients with elevated troponin but without ongoing symptoms 1

Low-Risk Patients (Initial Conservative/Selective Invasive Strategy)

For patients without troponin elevation, ST-segment deviation, or rest pain within 12 hours 1:

• Perform noninvasive stress testing
• If high-risk features on stress test: proceed to coronary angiography
• If negative stress test: consider alternative diagnoses or continued observation 1

Contraindications to Early Invasive Strategy

Do not perform early invasive strategy in 1:

• Patients with extensive comorbidities (liver failure, pulmonary failure, cancer) where revascularization risks outweigh benefits
• Patients with low likelihood of acute coronary syndrome
• Patients who refuse revascularization regardless of findings

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Revascularization Decision-Making

Post-Angiography Management

CABG is preferred for 2, 4:

• Significant left main disease
• Three-vessel disease, particularly with depressed left ventricular function
• Diabetic patients with multivessel disease

PCI with stenting 2:

• Effective for single-vessel or two-vessel disease when combined with dual antiplatelet therapy
• Use bare metal stents if non-cardiac surgery planned soon after intervention 2

If CABG selected: Continue aspirin but discontinue clopidogrel 5-7 days before elective surgery 3

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Critical Pitfalls to Avoid

• Never administer fibrinolytic therapy: Fibrinolysis has no benefit in unstable angina/NSTEMI without ST-elevation and actually increases MI risk 1, 3
• Do not delay treatment waiting for biomarkers: Initial management should be based on clinical presentation 3
• Do not discharge prematurely: Observe patients with possible ACS for at least 6-12 hours with serial ECGs and cardiac biomarkers 3
• Do not abruptly stop beta-blockers: Gradual reduction over 1-2 weeks is essential to prevent severe angina exacerbation, MI, or ventricular arrhythmias 5
• Do not withhold invasive strategy from women: Despite some conflicting trial data, high-risk women with obstructed coronary arteries suitable for revascularization should receive invasive management 1

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Long-Term Management and Secondary Prevention

Pharmacological therapy 2, 4:

• Aspirin 75-150 mg daily indefinitely
• Clopidogrel 75 mg daily for at least 12 months
• Beta-blockers continued long-term, particularly post-MI
• High-intensity statins targeting LDL <100 mg/dL
• ACE inhibitors for patients with left ventricular dysfunction, hypertension, or diabetes 2

Lifestyle modifications 2, 4:

• Smoking cessation with referral to cessation programs
• Weight optimization and daily exercise
• Tight glucose control in diabetic patients
• Dietary modifications

Follow-up schedule 2, 4:

• High-risk patients: Return in 1-2 weeks
• Low-risk medically treated or revascularized patients: Return in 2-6 weeks