What is the diagnosis and initial management for a 70-year-old patient with left-sided chest pain, first-degree AV block, and ECG changes including ST depression in leads V4-V6?

Diagnosis: Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS)

This 70-year-old patient with left-sided chest pain, ST depression in V4-V6 (0.5-1 mm), and flattened/inverted T waves in lateral leads meets criteria for NSTE-ACS (unstable angina or NSTEMI depending on troponin results), requiring immediate antiplatelet therapy, anticoagulation, serial troponin measurements, and risk stratification for early invasive management. 1

Immediate Diagnostic Actions

ECG Interpretation

• ST depression of 0.5-1 mm in V4-V6 with T-wave changes in lateral leads indicates myocardial ischemia, not STEMI, and classifies this patient as NSTE-ACS 1
• The absence of ST elevation rules out STEMI; patients with ST depression alone are classified as either unstable angina or NSTEMI based on cardiac biomarkers 2
• Obtain posterior leads (V7-V9) immediately to exclude true posterior MI, which can present with isolated ST depression in V1-V4 but would show ST elevation in posterior leads 1, 2
• The first-degree AV block (PR 216 ms) is noted but does not alter acute management of the coronary syndrome 1

Serial Biomarkers (Critical)

• Measure cardiac troponin T or I immediately as the preferred biomarker 1
• Repeat troponin at 6-12 hours after symptom onset to detect myocardial necrosis 1
• If troponin is elevated, the diagnosis is NSTEMI; if troponin remains normal with ECG changes, the diagnosis is unstable angina 1
• Consider early markers (myoglobin) in conjunction with troponin if presentation is within 6 hours of symptom onset 1

Risk Stratification

This patient has HIGH-RISK features based on: 1

• Age 70 years (>70 years is intermediate-to-high risk)
• ST depression 0.5-1 mm in multiple leads (V4-V6)
• T-wave inversions in lateral leads
• Active chest pain at presentation

Initial Medical Management (Start Immediately)

Antiplatelet Therapy

• Aspirin 162-325 mg chewed immediately unless absolute contraindication 1, 3
• Clopidogrel 300-600 mg loading dose, then 75 mg daily (or ticagrelor if available) 1, 3
• Clopidogrel should replace aspirin only if hypersensitivity or major gastrointestinal intolerance to aspirin exists 1

Anticoagulation

• Start low-molecular-weight heparin (LMWH) or unfractionated heparin immediately 1
• Continue LMWH while awaiting and preparing for angiography 1

Anti-Ischemic Therapy

• Beta-blocker (unless contraindicated by heart failure, bradycardia, or hypotension) 1
• Sublingual or intravenous nitroglycerin for persistent or recurrent chest pain 1
• Calcium antagonists may substitute for beta-blockers if contraindications exist 1

Glycoprotein IIb/IIIa Inhibitors

• Initiate GPIIb/IIIa inhibitor (tirofiban or eptifibatide) in high-risk patients, continuing for 12-24 hours after PCI if performed 1

Observation Period and Monitoring (First 6-12 Hours)

• Continuous ECG monitoring for arrhythmias, recurrent ST changes, or hemodynamic instability 1
• Repeat 12-lead ECG if chest pain recurs or clinical status changes 1
• Serial ECGs at 15-30 minute intervals if symptoms persist 1
• Monitor for hemodynamic instability (hypotension, pulmonary rales) 1
• Watch for major arrhythmias (ventricular tachycardia, ventricular fibrillation) 1

Early Invasive Strategy (Coronary Angiography)

This patient qualifies for early invasive management based on: 1

• ST depression in V4-V6 (high-risk ECG finding)
• Age 70 years
• Active symptoms at presentation

Timing of Angiography

• Coronary angiography should be performed within 24-48 hours (not emergent, but urgent) 1
• Immediate angiography (within 1 hour) is reserved for: 1
  • Severe ongoing ischemia despite medical therapy
  • Hemodynamic instability
  • Major arrhythmias (sustained ventricular tachycardia/fibrillation)

Revascularization Decision

• Revascularization strategy (PCI vs CABG) depends on angiographic findings and coronary anatomy 1
• Continue GPIIb/IIIa inhibitor for 12 hours (abciximab) or 24 hours (tirofiban/eptifibatide) after PCI 1

Critical Pitfalls to Avoid

• Do not dismiss 0.5-1 mm ST depression as insignificant—this magnitude in multiple leads indicates high-risk ischemia 1, 4
• Do not delay troponin measurement or fail to repeat at 6-12 hours—up to 6% of ACS patients have normal initial ECG 1
• Do not overlook posterior MI—isolated ST depression in V1-V4 with tall R waves and upright T waves represents posterior STEMI requiring immediate reperfusion 2, 4
• Do not activate STEMI protocols for this presentation—ST depression without persistent ST elevation requires NSTE-ACS management 1, 2
• Do not discharge based on single normal troponin—serial measurements are mandatory 1

Additional Diagnostic Considerations

• Chest radiograph to evaluate for heart failure, pulmonary causes, or aortic pathology 1
• Echocardiogram to assess left ventricular function and exclude other causes of chest pain (pericarditis, valvular disease) 1
• Consider BNP/NT-proBNP for additional prognostic information 1