ACS and CABG

Part 1: The Acute Presentation – Recognition and Initial Response

The management of Acute Coronary Syndromes (ACS) is time-critical. Initial actions in the first minutes to hours profoundly influence outcomes. For the AMC CAT MCQ examination, understanding initial assessment and management pathways in both general practice and emergency settings is essential.

Section 1.1: Clinical Presentation & Initial Triage

Typical vs. Atypical Symptoms

• Typical: Retrosternal pressure, tightness, heaviness; radiation to arm/jaw; dyspnoea, diaphoresis, nausea.
• Atypical (Common in women/elderly/diabetics): Unexplained fatigue, indigestion, back pain, syncope, or isolated nausea/vomiting.

The “First 10 Minutes” Algorithm (GP & Paramedic Focus)

1. Immediate priority: Call emergency services (000). Advise patient not to drive.
2. Give Aspirin: 300 mg chewed/dissolved immediately (unless allergy).
3. Perform 12-lead ECG: Interpret within 10 minutes to identify occlusion patterns.
4. Pain Relief (GTN): Sublingual spray/tablet every 5 mins (up to 3 doses) if SBP >100 mmHg.
5. Oxygen: Only if hypoxic (SpO2 <93%; 88-92% if COPD).

Initial Emergency Department Assessment (A-to-G Approach)

• Airway/Breathing: Position comfortably; monitor oxygenation.
• Circulation:
  • Attach cardiac monitor immediately.
  • Establish IV access.
  • Draw bloods: FBC, UEC, baseline high-sensitivity troponin (hs-cTn).
  • Interpret ECG within 10 minutes of arrival.

Section 1.2: Diagnostic Tools

ECG Paradigms (ACOMI)

The 2025 guidelines emphasize Acute Coronary Occlusion MI (ACOMI). Watch for:

• Classic ST Elevation (STEMI).
• Posterior MI (ST depression in V1–V3; check V7–V9 for elevation).
• De Winter’s T-waves (Proximal LAD occlusion).
• New or presumed-new LBBB (Apply Sgarbossa criteria).

hs-Troponin 0/2-Hour Algorithm

1. T0: Baseline troponin on arrival.
2. Risk Score: Calculate TIMI or GRACE.
3. T2: Repeat troponin at 2 hours.
   • Rule-out: Low baseline and no change in low-risk patient.
   • Rule-in: Significant delta (rise) between T0 and T2.

Section 1.3: Differential Diagnosis of Chest Pain

Part 2: Revascularization Strategies

Section 2.1: STEMI/ACOMI Timing

• PCI-capable hospital: Door-to-balloon <60 minutes.
• Non-PCI hospital: First medical contact to balloon <90 minutes.
• Remote: If >90 min delay, give IV fibrinolysis immediately, then transfer for PCI within 24h.

Section 2.2: The Heart Team (PCI vs. CABG)

Decision based on anatomy and patient risk:

• SYNTAX Score: * 0–22: PCI or CABG.
  • ≥23: CABG favoured (especially if 3-vessel or high complexity).
• Diabetes/Multivessel Disease: CABG offers superior survival.
• Reduced LVEF (≤35%): CABG favoured (STICH trial).

Part 3: Post-ACS Pharmacology

Section 3.1: Dual Antiplatelet Therapy (DAPT)

• Standard: 12 months post-ACS.
• Post-PCI agents: Aspirin 100mg + Ticagrelor 90mg BD (preferred) or Prasugrel.
• Post-CABG update: Latest evidence (TACSI 2025) suggests aspirin monotherapy is often sufficient post-CABG as DAPT increased bleeding without MACE benefit.

Section 3.2: Secondary Prevention Targets

• LDL-C: <1.4 mmol/L AND >50% reduction from baseline.
• Algorithm: High-intensity statin $\rightarrow$ add Ezetimibe $\rightarrow$ add PCSK9 inhibitor.
• SAMS (Statin Myopathy): Dechallenge $\rightarrow$ Restart at lower dose/different agent $\rightarrow$ Consider intermittent dosing (twice weekly).

Part 4: AMC Exam High-Yield Summary

1. Safety First: If the pain pattern has changed, it is unstable.
2. Time Targets: ECG in 10 mins; Aspirin immediately.
3. Dissection Trap: Never give antithrombotics if tearing pain and BP differential are present—CT first.
4. Digoxin: Toxicity increased by hypokalaemia (e.g., from diuretics). Target level 0.5–0.9 ng/mL.

Works Cited (Refer to source file for full reference list 1-109)