What are the clinical features and management of acute coronary syndrome?

Clinical Features of Acute Coronary Syndrome

Acute coronary syndrome presents most commonly with prolonged anginal chest pain at rest (>20 minutes) in 80% of patients, but atypical presentations without chest pain occur in up to 40-48% of cases, particularly in women, elderly patients (>75 years), diabetics, and younger patients (25-40 years). 1

Typical Clinical Presentations

The three classic presentations include:

• Prolonged anginal pain at rest (>20 minutes) - observed in 80% of patients 1
• New onset severe angina (Class III CCS) - observed in only 20% of patients 1
• Crescendo angina - recent destabilization of previously stable angina with at least CCS III characteristics 1

The typical ischemic cardiac pain is described as deep, poorly localized chest or arm discomfort that may be described as pain, pressure, tightness, or burning, and may radiate to the arms, jaw, neck, back, or epigastric region. 1

Atypical Presentations (High-Risk Populations)

Atypical presentations are common and occur frequently in women (48% present without chest pain), elderly patients >75 years, diabetics, and younger patients 25-40 years of age. 1

Atypical symptoms include:

• Dyspnea alone or combined with chest discomfort - affects approximately 40% of men and 48% of women 2
• Epigastric pain or recent onset indigestion 1
• Stabbing chest pain - acute myocardial ischemia diagnosed in 22% of ED patients with sharp/stabbing pain 1
• Chest pain with pleuritic features - ischemia diagnosed in 13% of these patients 1
• Pain predominantly at rest 1

Features NOT Characteristic of Myocardial Ischemia

The following features make ACS less likely but do not exclude it:

• Pleuritic pain (sharp or knifelike pain provoked by respiration or cough) 1
• Pain localized by one fingertip, particularly at the LV apex 1
• Pain reproduced with palpation of chest wall - only 7% of these patients had ACS 1
• Brief episodes lasting seconds 1
• Pain radiating to lower extremities 1

Physical Examination Findings

Physical examination is most often completely normal in ACS patients. 1

The purpose of examination is to:

• Exclude non-cardiac causes - pneumothorax, pulmonary embolism, pericarditis, valvular disease 1
• Identify signs of hemodynamic instability - hypotension, tachycardia 1
• Detect left ventricular dysfunction - S3 gallop, pulmonary rales 1

Electrocardiographic Features

A 12-lead ECG must be obtained within 10 minutes of presentation and is the key diagnostic tool for initial assessment. 1, 3, 2

ECG Changes in Non-ST-Elevation ACS:

• ST-segment depression ≥1 mm in two or more contiguous leads - most reliable indicator 1
• Transient ST-segment elevation 1
• T-wave inversion - particularly deep and symmetrical T-wave inversions in anterior leads indicate critical proximal coronary stenosis 1, 3
• Flat T waves or pseudo-normalization of T waves 1
• Normal ECG - occurs in approximately 41% of NSTE-ACS patients 2

The ECG should be repeated with any recurrence of symptoms or at regular intervals during observation, and compared with previous tracings when available. 1, 3

ECG Changes in ST-Elevation ACS:

Persistent ST-segment elevation (>20 minutes) indicates complete coronary occlusion (STEMI) and requires immediate reperfusion therapy. 1

Cardiac Biomarkers

Cardiac troponin T or I are the preferred markers for myocardial necrosis and must be measured serially - a single measurement is insufficient to exclude myocardial infarction. 1, 3

Key points about biomarkers:

• Obtain troponin immediately and repeat at 6-12 hours from symptom onset - myocardial injury may not be detectable in the first hours 3
• Elevated troponin with at least one value above the 99th percentile upper reference limit defines myocardial infarction when combined with clinical evidence of ischemia 1
• Troponin elevation without CK-MB elevation represents "minimal myocardial damage" and is associated with unfavorable outcomes 1
• High-sensitivity troponin measurements are the preferred test for evaluating NSTEMI 2

Pathophysiology Underlying Clinical Features

The clinical spectrum reflects:

• Atherosclerotic plaque rupture or erosion with superimposed thrombosis 1
• Varying degrees of coronary occlusion - complete occlusion causes STEMI, partial/intermittent occlusion causes NSTE-ACS 1, 2
• Distal embolization causing focal areas of myocardial necrosis 1
• Vasoconstriction from platelet-released substances (serotonin, thromboxane A2) 1

High-Risk Clinical Features Requiring Urgent Management

The following features mandate urgent coronary angiography within 24-48 hours: 3

• Recurrent or persistent ischemic chest pain despite medical therapy 3
• Dynamic ST-segment changes 3
• Hemodynamic instability 3
• Major arrhythmias 3
• Diabetes mellitus 3
• Early post-infarction unstable angina 3

A small subset with severe ongoing ischemia, cardiogenic shock, or malignant arrhythmias requires coronary angiography within the first hour. 3

Initial Diagnostic Algorithm

1. Obtain 12-lead ECG within 10 minutes - differentiates STEMI from NSTE-ACS 1, 3, 2
2. Measure cardiac troponin immediately and at 6-12 hours 3
3. Assess for high-risk features - ongoing pain, ST changes, hemodynamic instability 3
4. Repeat ECG with symptom recurrence or at regular intervals 1, 3
5. Compare with previous ECG when available - particularly valuable in patients with LVH or prior MI 1