What is the initial evaluation and management approach for a patient presenting with symptoms suggestive of Acute Coronary Syndrome (ACS), including chest pain or discomfort and shortness of breath?

Initial Evaluation and Management of Suspected Acute Coronary Syndrome

Patients with symptoms suggestive of ACS—including chest pain, shortness of breath, or arm/jaw discomfort—require immediate 12-lead ECG within 10 minutes of presentation, aspirin 162-325 mg (chewed), and serial cardiac troponin measurements to guide risk stratification and treatment decisions. 1

Immediate Actions in First 10 Minutes

Call 9-1-1 and Transport

• Patients should call 9-1-1 immediately if chest discomfort is unimproved or worsening after 5 minutes, rather than self-transport or wait for symptom resolution 1, 2
• High-risk features mandating emergency transport include: chest pain lasting >20 minutes at rest, hemodynamic instability, syncope/presyncope, severe dyspnea, or palpitations 1, 2
• EMS transport allows for prehospital ECG acquisition (which reduces mortality), early aspirin administration, and defibrillation capability if cardiac arrest occurs 1, 3

Prehospital and ED Assessment

• Obtain 12-lead ECG within 10 minutes of first medical contact to differentiate STEMI from non-ST-elevation ACS 1, 4
• Administer aspirin 162-325 mg (chewed, non-enteric coated) immediately unless contraindicated by known allergy or active GI bleeding 1, 4
• Check vital signs and oxygen saturation; provide supplemental oxygen only if O2 sat <94% or respiratory distress present 1, 4
• Establish IV access and draw initial cardiac troponin (preferably high-sensitivity), electrolytes, and coagulation studies 1

Risk Stratification Based on Presentation

High-Risk Features Requiring Immediate Intervention

• Prolonged ongoing rest pain (>20 minutes), hemodynamic instability, pulmonary edema, or signs of shock indicate highest risk 1
• ST-segment elevation ≥1 mm in contiguous leads or new/presumably new left bundle branch block on ECG 1
• Elevated cardiac troponin above 99th percentile upper reference limit 1, 5
• Dynamic ST-segment depression or deep T-wave inversions strongly suggest active ischemia 1

Intermediate-Risk Features

• Prior history of MI, coronary artery disease, or revascularization (PCI/CABG) 1
• Age >70 years, diabetes mellitus, or chronic kidney disease 1, 4
• Rest angina >20 minutes that has now resolved 1
• ST-segment depression 0.5-1 mm or T-wave inversions on ECG 1

Symptoms Requiring Heightened Clinical Suspicion

• Classic presentation: Substernal chest pressure/tightness with radiation to left arm, neck, jaw, or back; associated with dyspnea, diaphoresis, nausea 1
• Atypical presentations (more common in women, elderly, diabetics): Isolated dyspnea without chest pain, unexplained fatigue, epigastric discomfort, or generalized weakness 1, 2, 4
• Unexplained dyspnea alone carries more than twice the mortality risk compared to typical angina presentations 1

Diagnostic Testing Algorithm

ECG Interpretation and Serial Monitoring

• If initial ECG shows ST-elevation or new LBBB: Activate STEMI protocol immediately for reperfusion therapy 1, 5
• If initial ECG shows ST-depression or dynamic T-wave changes: Treat as high-risk NSTE-ACS with serial troponins and early invasive strategy 1
• If initial ECG is nondiagnostic but symptoms persist: Obtain serial ECGs at 15-30 minute intervals to detect evolving changes 1, 4
• Consider supplemental posterior leads (V7-V9) if intermediate-to-high suspicion and nondiagnostic initial ECG 4

Cardiac Biomarker Strategy

• Measure high-sensitivity cardiac troponin immediately upon presentation as the preferred biomarker (>90% sensitivity, >95% specificity) 1, 5
• Repeat troponin at 3-6 hour intervals if initial result is negative but clinical suspicion remains 1, 4
• Do not use total CK alone (without CK-MB) or AST/ALT/LDH as primary markers—these lack adequate sensitivity and specificity 1
• For patients presenting within 6 hours of symptom onset, consider adding early markers (myoglobin) to late markers (troponin) for enhanced sensitivity 1

Immediate Medical Management

Pharmacologic Therapy

• Aspirin 162-325 mg chewed (non-enteric coated for faster absorption) unless contraindicated 1, 4
• Sublingual nitroglycerin 0.3-0.4 mg every 5 minutes (up to 3 doses) for ongoing chest pain, unless systolic BP <90 mmHg, heart rate <50 or >100 bpm, or recent phosphodiesterase-5 inhibitor use 1, 4
• Morphine IV titrated to pain severity if discomfort not relieved by nitroglycerin—reduces sympathetic activation and myocardial oxygen demand 1, 3
• Avoid NSAIDs for pain relief as they increase risk of major adverse cardiac events 4

Antiplatelet and Anticoagulation (Once ACS Confirmed)

• Initiate dual antiplatelet therapy with aspirin plus P2Y12 inhibitor (clopidogrel 300 mg loading dose, or ticagrelor/prasugrel) 4
• Start anticoagulation with low molecular weight heparin or unfractionated heparin 4

Reperfusion Strategy Based on ECG Findings

STEMI Management

• Primary PCI is preferred: Door-to-balloon time goal of ≤90 minutes (≤120 minutes acceptable if transfer required) 1, 5
• If PCI unavailable within 120 minutes: Administer fibrinolytic therapy with door-to-needle time ≤30 minutes, then transfer for PCI within 24 hours 1, 5
• Fibrinolytic options: Alteplase, reteplase, or tenecteplase at full dose for age <75 years; half dose for age ≥75 years 5
• Check fibrinolytic contraindications: Systolic BP >180-200 mmHg, diastolic BP >100-110 mmHg, history of intracranial hemorrhage, recent major trauma/surgery, active bleeding 1

NSTE-ACS Management

• High-risk patients (elevated troponin, dynamic ECG changes, hemodynamic instability): Early invasive strategy with coronary angiography within 24-48 hours reduces mortality from 6.5% to 4.9% 5, 6
• Intermediate-risk patients: Consider selective invasive strategy with angiography if high-risk features develop during observation 6
• Admit to coronary care unit with continuous cardiac monitoring for arrhythmia detection 1

Disposition and Ongoing Evaluation

Admission Criteria

• Any patient with elevated troponin, ischemic ECG changes, or high-risk clinical features requires hospital admission 1, 4
• Patients with hemodynamic instability, pulmonary edema, or ongoing ischemia require coronary care unit admission 1

Chest Pain Unit or Observation

• Patients with normal initial ECG and troponin but intermediate risk can be observed in chest pain unit with serial biomarkers and continuous ST-segment monitoring 1
• Perform stress testing (treadmill ECG or stress myocardial perfusion imaging) before discharge or within 72 hours if serial ECGs and troponins remain normal 4
• Obtain portable chest x-ray within 30 minutes to evaluate for alternative diagnoses 1

Critical Pitfalls to Avoid

Diagnostic Errors

• Do not rely on nitroglycerin response as diagnostic—esophageal spasm and other conditions also respond to nitrates 3
• Do not discharge based on single negative troponin—serial measurements over 3-6 hours are mandatory 4
• Do not assume young age excludes ACS—it can occur even in adolescents without traditional risk factors 3
• Do not evaluate patients solely over telephone—facility-based evaluation with ECG and biomarkers is required 1

High-Risk Populations Requiring Extra Vigilance

• Women frequently present with atypical symptoms (nausea, fatigue, dyspnea without chest pain) and are at risk for underdiagnosis 1, 2, 4
• Elderly patients (≥75 years) may present with isolated dyspnea, syncope, acute delirium, or unexplained falls without classic chest pain 1, 3
• Diabetic patients may have atypical presentations due to autonomic dysfunction 1
• Silent MI occurs in up to 50% of cases and is associated with 2.2-fold higher in-hospital mortality (23.3% vs 9.3%) 1

Treatment Delays

• Avoid consultation delays that postpone reperfusion therapy—these are directly associated with increased mortality 2, 4
• Each hour of delay in reperfusion reduces lives saved from 35 per 1000 (if treated within 1 hour) to 16 per 1000 (if treated at 7-12 hours) 3
• Do not delay transfer to ED for troponin testing in office settings when ACS is suspected 3

Life-Threatening Differential Diagnoses to Exclude

• Acute aortic dissection: Sudden-onset tearing/ripping pain radiating to back, blood pressure differential between arms >15 mmHg 1, 3
• Pulmonary embolism: Sudden dyspnea with pleuritic chest pain, especially with risk factors for thromboembolism 2, 3
• Tension pneumothorax: Sudden dyspnea, absent breath sounds, tracheal deviation 2
• Pericarditis with tamponade: Sharp positional chest pain, muffled heart sounds, pulsus paradoxus 2