What are the clinical features and management of unstable angina?

Clinical Features of Unstable Angina

Unstable angina presents in three distinct patterns: prolonged rest angina lasting >20 minutes, rapidly progressive crescendo angina worsening over ≤4 weeks, or new-onset severe angina causing marked limitation within 2 months of presentation. 1

Characteristic Symptom Patterns

Three Classic Presentations

• Rest angina occurs without provocation, lasting up to 20 minutes with characteristic substernal location and quality, representing 80% of unstable angina presentations 1

• Crescendo angina manifests as previously stable angina that progressively increases in severity, frequency, and occurs at lower exertion thresholds over ≤4 weeks 1

• New-onset severe angina presents as recent-onset symptoms (within 2 months) causing marked limitation of ordinary physical activity, meeting Canadian Cardiovascular Society Class III criteria 1

Pain Characteristics

• The discomfort is typically substernal, described as pressure, tightness, heaviness, strangling, constricting, or burning, and may radiate to the jaw, teeth, shoulder blades, arms, wrists, or fingers 1

• Episodes are more severe and prolonged than stable angina, may occur at rest, and are precipitated by less exertion than previously 1

• Duration typically ranges from several minutes to 20 minutes, distinguishing it from stable angina (which lasts <5 minutes) but chest pain lasting only seconds is unlikely to be angina 1

• Pain is usually relieved by rest and/or sublingual nitroglycerin within minutes, though relief may be less prompt than in stable angina 1

Atypical Presentations

High-Risk Patient Groups

• Atypical presentations are common in younger patients (25-40 years), older patients (>75 years), diabetic patients, and women 1

• These patients may present with epigastric pain, recent-onset indigestion, stabbing chest pain, chest pain with pleuritic features, or increasing dyspnea 1

Anginal Equivalents

• Some patients present without chest discomfort but with isolated symptoms in the jaw, neck, ear, arm, shoulder, back, or epigastrium 1

• Isolated unexplained new-onset or worsened exertional dyspnea is the most common anginal equivalent, especially in older patients 1

• Less common isolated presentations include nausea and vomiting, diaphoresis, and unexplained fatigue, particularly in older adults 1

• If these symptoms have clear relationship to exertion/stress or are relieved promptly with nitroglycerin, they should be considered equivalent to angina 1

Features NOT Characteristic of Unstable Angina

• Pleuritic pain (sharp or knifelike pain with respiratory movements or cough) 1

• Pain localized to a small portion of the left hemithorax or at the tip of one finger, particularly over the left ventricular apex 1

• Discomfort lasting several hours or days continuously 1

• Pain that is fully reproduced by palpation of the chest wall 1

• Very brief episodes lasting only seconds 1

Physical Examination Findings

Typical Examination

• Physical examination is most often completely normal, including chest examination, cardiac auscultation, heart rate, and blood pressure 1

High-Risk Physical Findings

• Pulmonary edema (most likely due to ischemia) indicates high-risk unstable angina 1

• New or worsening mitral regurgitation murmur may be apparent during ischemia 1

• Third or fourth heart sound (S3 or S4) may be heard during or immediately after an ischemic episode 1

• Signs of hemodynamic instability including hypotension, bradycardia, or tachycardia indicate high-risk features 1

• New or worsening rales suggesting pulmonary congestion 1

Electrocardiographic Features

Key ECG Findings

• ST-segment depression >1 mm in two or more contiguous leads during symptomatic episodes is the most reliable electrocardiographic indicator 1

• Transient ST-segment elevation occurring at rest that resolves spontaneously or with nitroglycerin suggests variant (Prinzmetal's) angina 1

• T-wave changes, particularly dynamic T-wave inversions, are reliable indicators of unstable coronary disease 1

• Comparison with previous electrocardiograms is extremely valuable, particularly in patients with left ventricular hypertrophy or previous myocardial infarction 1

Timing of ECG Assessment

• A 12-lead ECG should be obtained within 10 minutes of presentation for all patients with chest discomfort 1

• Ideally, tracings should be obtained when the patient is symptomatic and compared with tracings when symptoms have resolved 1

• Serial ECGs at 15-30 minute intervals should be performed if initial ECG is non-diagnostic but clinical suspicion remains high 1

Cardiac Biomarkers

• Cardiac troponin T or troponin I are the preferred markers for detecting minimal myocardial damage and should be measured in all patients 1

• Elevated troponin levels in the absence of CK-MB elevation indicate minimal myocardial damage and are associated with unfavorable clinical outcomes 1

• Patients with negative cardiac biomarkers within 6 hours of symptom onset should have biomarkers remeasured at 8-12 hours after symptom onset 1

• If clinical suspicion of instability exists, biochemical markers of myocardial damage such as troponin or creatinine kinase myocardial band should be employed to exclude myocardial injury 1

Risk Stratification Features

High-Risk Clinical Features

• Accelerating tempo of ischemic symptoms in the preceding 48 hours 1

• Prolonged ongoing rest pain (>20 minutes) 1

• Angina at rest with transient ST-segment changes >0.5 mm 1

• Elevated cardiac troponin T, troponin I, or CK-MB (e.g., TnT or TnI >0.1 ng/mL) 1

• New or worsening mitral regurgitation, S3 heart sound, pulmonary edema, hypotension, bradycardia, or tachycardia 1

• Bundle-branch block (new or presumed new) or sustained ventricular tachycardia 1

Intermediate-Risk Features

• Prior myocardial infarction, peripheral or cerebrovascular disease, or prior coronary artery bypass grafting 1

• Prolonged (>20 minutes) rest angina, now resolved, with moderate or high likelihood of coronary artery disease 1

• Age >70 years 1

• T-wave changes or pathological Q waves or resting ST-depression <1 mm in multiple lead groups 1

• Slightly elevated cardiac troponin (e.g., TnT >0.01 but <0.1 ng/mL) 1

Common Pitfalls to Avoid

• Do not dismiss atypical presentations in high-risk groups (elderly, diabetics, women), as acute myocardial ischemia was diagnosed in 22% of patients with sharp/stabbing chest pain and 13% with pleuritic features 1

• Do not rely solely on pain relief with nitroglycerin to confirm cardiac origin, as esophageal spasm may also respond to nitroglycerin 1

• Do not assume normal physical examination excludes unstable angina, as examination is typically normal in most patients 1

• Do not overlook variant angina, which may present with normal exercise tolerance and negative stress testing despite significant coronary disease 1