What are the classifications of angina and the recommended management for each type?

Angina Classification and Management

Primary Classification Systems

Angina is classified into five major clinical types—stable angina, unstable angina, variant (Prinzmetal's) angina, microvascular angina (Syndrome X), and atypical angina—with severity graded using the Canadian Cardiovascular Society (CCS) functional classification system from Class I to IV. 1

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Stable Angina

Clinical Characteristics

• Predictable substernal chest pressure or heaviness triggered by specific exertion levels (walking uphill, cold weather, heavy meals, emotional stress) and consistently relieved within minutes by rest or sublingual nitroglycerin 2, 1
• Episodes last less than 10 minutes and have remained unchanged in pattern for at least 6 weeks 1, 3
• Pain may radiate to jaw, neck, shoulder, back, or arms 3

CCS Functional Classification

• Class I: Angina only with strenuous/rapid/prolonged exertion; can walk >2 blocks on level ground or climb >1 flight of stairs at normal pace without symptoms 2, 4
• Class II: Slight limitation; angina when walking 2 blocks on level ground or climbing 1 flight of stairs at normal pace, or walking rapidly/uphill 2, 4
• Class III: Marked limitation; angina when walking 1-2 blocks on level ground or climbing 1 flight of stairs at normal pace 2, 4
• Class IV: Inability to perform any physical activity without discomfort; angina may occur at rest 2, 4

Management Approach

• Acute episodes: Sublingual nitroglycerin (patient should sit down to avoid hypotension); seek immediate medical attention if pain persists >10-20 minutes despite rest and nitroglycerin 3
• Chronic therapy: Beta-blockers, long-acting nitrates, and calcium channel blockers as single or combination therapy 5, 6
• Lifestyle modifications: Smoking cessation, Mediterranean-style diet, weight reduction, and regular physical activity within tolerated limits 3
• Revascularization indications: Left main disease, three-vessel disease with large ischemia or poor ventricular function, two- or three-vessel disease including severe proximal LAD stenosis 2

Prognosis

• Annual mortality 0.9-1.4%; non-fatal MI incidence 0.5-2.6% 3
• Two-year rates: non-fatal MI 14.3% (men) and 6.2% (women); coronary death 5.5% (men) and 3.8% (women) 3

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Unstable Angina

Clinical Characteristics

Unstable angina requires immediate hospitalization and represents an acute coronary syndrome with three defining presentations: 2, 1, 4

1. Rest angina: Prolonged episodes (≥20 minutes) occurring without provocation; accounts for ~80% of presentations 2, 3
2. New-onset severe angina: Recent symptoms (≤2 months) causing marked limitation, meeting CCS Class III or IV criteria 2, 4
3. Crescendo angina: Previously stable angina that accelerates in frequency, duration, or occurs at lower thresholds, with ≥1 CCS class increase to at least Class III severity 2, 4

Diagnostic Features

• ST-segment depression >1 mm in two or more contiguous leads during symptoms is the most reliable ECG indicator 3
• Troponin I or T should be measured in all patients; modest elevations (>0.1 ng/mL) denote minimal myocardial injury and predict poorer outcomes 3
• Approximately 5% of patients have a completely normal ECG even during symptomatic episodes 3, 4
• Physical examination is often normal; presence of pulmonary edema signals high-risk presentation 3

Management Approach

• Immediate hospitalization with bed rest due to high-risk nature 3
• Mandatory risk stratification: Calculate TIMI risk score (0-7 points) predicting adverse outcomes from 5% (score 0-1) to 41% (score 6-7) 3
• High-risk features include accelerating symptoms within 48 hours, prolonged rest pain >20 minutes, and elevated troponin 3

Prognosis

• Short-term risk of acute coronary events substantially higher than stable angina 3
• Compared to NSTEMI, unstable angina has lower mortality but substantial morbidity 1

Critical Pitfall

• Do not discharge patients with rest angina or crescendo pattern even if initial examination and ECG are normal 3, 4
• Women may have non-obstructive coronary disease or normal angiogram 4

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Variant (Prinzmetal's) Angina

Clinical Characteristics

• Caused by coronary artery vasospasm from hypercontractility of vascular smooth muscle and/or endothelial dysfunction 2
• Occurs spontaneously at rest (not with exertion), typically at night or early morning 1, 7
• Characterized by transient ST-segment elevation during episodes 1

Management Approach

• First-line therapy: Oral long-acting nitrates (nitroglycerin, isosorbide dinitrate) effectively relieve coronary artery spasm 7
• Second-line therapy: Calcium channel blockers (nifedipine is prototype for antianginal activity; verapamil effective but limited by first-pass metabolism) 7
• Avoid beta-blockers: Studies show equivocal results with some reporting worsening of symptoms 7
• Combination therapy with nitrates and calcium channel blockers may be needed in refractory cases 7

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Microvascular Angina (Cardiac Syndrome X)

Clinical Characteristics

• Defined by the triad of: (1) typical exercise-induced angina (with or without resting angina/dyspnea), (2) positive exercise stress ECG or stress imaging, and (3) angiographically normal coronary arteries 2, 1
• Frequent anginal episodes (several times per week) with stable pattern 2
• Caused by coronary microvascular dysfunction from endothelial dysfunction or abnormal constriction of small intramural resistance vessels 2
• Frequently encountered in patients with hypertension, with or without left ventricular hypertrophy 2, 1

Atypical Presentation Pattern

• Pain often starts at rest from low intensity, slowly intensifies, remains at maximum for up to 15 minutes, then slowly decreases 2
• May occur after exertion rather than during, and poorly responsive to nitrates 2

Prognosis

• Favorable mortality prognosis but high morbidity with continuing chest pain episodes and hospital readmissions 2
• Impaired endothelial dysfunction may identify subgroup at risk for future atherosclerotic disease development 2

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Atypical Angina

Clinical Characteristics

• Chest discomfort meeting only two of the three typical angina characteristics (substernal location/quality, provoked by exertion/stress, relieved by rest/nitrates) 2, 1
• Symptoms include epigastric pain, indigestion-like complaints, or isolated dyspnea without classic chest pressure 1
• More common in elderly patients, women, and those with diabetes, chronic kidney disease, or dementia 1

Management Consideration

• Requires same diagnostic workup as typical angina given potential for myocardial ischemia 1

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Key Management Principles Across All Types

Differential Diagnosis Considerations

• Always exclude: Esophageal spasm, gastric ulcer, cholecystitis, pancreatitis, pulmonary embolism, pericarditis, aortic dissection 1
• Relief with nitroglycerin is not specific for angina (occurs with esophageal disorders) 1

Risk Factor Modification

• Major risk factors for coronary heart disease and unstable angina/NSTEMI are well established; clinical trials demonstrate that modification reduces events 2
• Secondary unstable angina occurs when precipitating conditions increase myocardial oxygen requirements (fever, tachycardia, thyrotoxicosis), reduce coronary flow (hypotension), or reduce oxygen delivery (anemia, hypoxemia) 2

Monitoring and Follow-up

• Use CCS classification to monitor progression; any change to CCS III-IV or instability requires immediate action 4
• Alternative systems (Duke Specific Activity Index, Seattle Angina Questionnaire) may offer superior prognostic capability 4