Acute Coronary Syndromes

Ryan Pohlkamp

Background

Coronary occlusion due to completely or partially occluding thrombus on a disrupted atherothrombotic coronary plaque leading to myocardial ischemia/infarction.

Less commonly due to embolism, dissection or vasospasm.

  • STEMI: Elevated troponin & elevation in ST segment or new LBBB with symptoms.
    • > 0.1 mV in at least 2 contiguous leads
    • Exception, in V2-V3:
      • > 0.2 mV in men older than 40 y/o
      • > 0.25 in men younger than 40 y/o
      • > 0.15 mV in women
    • Use Sgarbossa’s Criteria for MI with LBBB (≥3 points) or ventricular pacing.
      • Concordant ST-segment elevation ≥0.1mV in leads with a positive QRS complex (5 points).
      • Concordant ST-segment depression ≥0.1mV in leads V1, V2, or V3 (3 points).
      • Discordant ST-segment elevation ≥0.5mV in leads with a negative QRS complex (2 points).
  • NSTEMI: (Type I): Evidence of myocardial necrosis (elevated troponin) w/o ST segment elevation (ECG changes often present but not required for diagnosis).
    • ST depression of ≥0.5mV, in two or more contiguous leads.
    • New T-wave inversions of ≥1mV compared to previous ECGs.
    • Normalization of prior T-wave inversions suggestive of dynamic process of ischemia.
  • Unstable Angina: Angina without evidence of myocardial necrosis (normal troponin).
  • Non-ACS causes of myocardial injury (“Type II MI”): imbalance of oxygen demand and supply 2/2 fever, tachycardia, hypo-/hypertension, etc.

Presentation

  • Classic angina: retrosternal with characteristic radiation (e.g., left arm, neck, jaw) , pressure or vice-like quality, with associated symptoms (e.g., diaphoresis, dyspnea, nausea, abdominal pain, or syncope).
  • Change in pt’s baseline angina, especially onset at rest.
  • Physical Exam: sinus tachycardia, diaphoresis.
  • If large infarct, can present with symptoms of acute heart failure.

High sensitivity Troponin (hs-cTnT)

  • Reference values (sex specific ULN, 99th percentile): 14ng/L for adults assigned female at birth, 22ng/L for adults assigned male at birth, 19ng/L for unknown sex; above these limits are diagnostic of myocardial injury.
  • Acute myocardial injury: absolute delta change of ≥3ng/L for hs-cTNT values below the sexspecific percentile OR changes in hs-cTnT values of ≥20% when at least one of the values is above the 99th percentile.
    • hs-cTnT peaks within 12-48 hours and normalizes in 5-14 days.
  • Obtain ECG and compare to prior if available. Assess for:
    • New ST elevations à STAT call 1-1111 to activate STEMI alert
    • New ST depression, T wave inversions (not specific but more concerning if deep; > 0.3mV), Biphasic T waves and deep T wave inversions in leads V2 & V3 (Wellens sign [LAD]) → Obtain hs-cTnT (Order set: Initial + 3hr repeat + 6hr repeat) → Obtain serial ECGs Q2-6h hours to monitor for dynamic changes.
    • Nonischemic ECG → obtain hs-cTnT. Categorize the initial hs-cTnT result:
      • Low (≤6 ng/L) → Determine timing of symptom onset:
        • < 3hrs → Obtain 3hr repeat
        • > 3hrs → May discontinue troponin testing; however, if high suspicion for ACS despite normal initial markers obtain 3hr repeat.
      • Borderline (6-14 ng/L female, 6-22 ng/L male) → Order 3hr repeat.
        •  Δ < 3 ng/L → stop trending
        • Δ > 3 ng/L → obtain 6hr repeat, serial ECG, and monitor
          patient’s symptoms.
      • Elevated (>14 ng/L female, >22 ng/L male)
        • If clinically lower concern for ACS → obtain 3hr repeat
        • If clinically higher concern for ACS → obtain 3hr repeat,
          management per NSTEMI.

Management

STEMI

  • STAT page Cardiology on call via Synergy (whether in VA or Vanderbilt). Rapid PCI within 120 mins is crucial.
  • ASAP: aspirin 325mg, heparin drip (high nomogram, with bolus).
  • Hold P2Y12 until discussed with Cardiology fellow.

NSTEMI

  • High risk: Medical management followed by left-heart catheterization within 48h.

Anti-Thrombotic Therapy

  • Antiplatelet agents:
    • ASA 325mg loading dose then 81mg daily after
    • Do not give P2Y12 receptor blocker until discussed with cardiology fellow.
    • Clopidogrel: prodrug metabolized by CYP219 to active form, irreversible inhibition.
    • Ticagrelor: reversible inhibitor, contraindicated in patients w/ severe hepatic disease, history of ICH, active pathological bleeding.
    • Prasugrel: prodrug but more rapidly metabolized than clopidogrel with less variation, irreversible inhibition, contraindicated if age > 75 or weight < 60 kg or prior TIA/CVA.
    • Cangrelor IV:, Integrilin IV
  • Anti-coagulants: Unfractionated heparin drip (ACS protocol)
  • Pain control: nitrates or opioids
  • Nitrates: SL nitroglycerin 0.4mg q5min PRN (short-acting); nitropaste, nitroglycerin gtt (shortacting but continuous), isosorbide dinitrate, isosorbide mononitrate (longer-acting).
    • Use with caution if inferior MI or hypotension.

Pre-Catheterization Care

  • New VUMC Policy: patients can have clear liquid diet starting 6 hours before left or right heart cath. Ensure patients have a clear liquid diet or NPO status after midnight.
  • Continue anticoagulation with heparin gtt
  • Cardiac cath request:
    • VUMC: Place cardiac catheterization request in cardiology context, proceduralist usually “surgeon generic.”
    • VA: Discuss with cardiology fellow cath request and/or call VA cath lab.

Post-Catheterization Care

Post-Catheterization Heparin

  • Medical management w/o intervention: stop heparin unless directed in report.
  • If indication for CABG (ex: Left main, proximal LAD), continue heparin gtt until surgery.
  • PCI placed: stop heparin and continue/start DAPT as directed by cardiology.
  • Other medical indication for anticoagulation (DVT/PE, atrial fibrillation): restart ~ six hours after catheterization.

Cath Site Checks

  • 6-8h post catheterization (typically can be signed out as 0000 cath check), only needed for femoral arterial access:
  • Look, listen, feel: evaluate for hematoma & pseudoaneurysm (thrill on palpation; bruit on auscultation); call fellow if concerned. Small amount of bruising and mild tenderness at the site is normal.
    • Listen above and below the site for a bruit; the area should be soft.
  • Hypotension after femoral access is concerning for RP bleed.
    • Apply pressure, STAT page interventional fellow, do NOT take pt to scanner prior to hearing back, order blood if needed, may need FemStop compression system (Call CCU to obtain if needed).
  • Femoral oozing: Page Cardiology fellow, will need to apply pressure (rule of thumb: 3 min of blood flow occluding pressure for each French of catheter used).
  • Radial oozing: instruct nurse to re-inflate the TR band and restart the clock on deflation.

Post ACS Care

  • TTE prior to discharge
  • DAPT: Aspirin 81 mg daily and P2Y12 agent (duration varies but usually specified in catheterization report).
    • If patient on long term AC for comorbid condition, consider P2Y12 inhibitor plus DOAC, given increased bleeding risk with triple therapy.
  • Beta blocker within 24 hours (new evidence suggests that majority of benefit seen in patients with LVEF < 40% though practice patterns vary).
  • High intensity statin (ex: rosuvastatin 40 or atorvastatin 80). See outpt lipids section.
  • ACEi/ARB if anterior STEMI, post-MI LV dysfunction.
  • Lifestyle Modification: weight loss, smoking cessation, diabetes control, hypertension management
  • Cardiac rehabilitation.

ACS Complications

  • VT/VF, sinus bradycardia, third-degree heart block, new VSD, LV perforation, acute mitral regurgitation, pericarditis, and cardiogenic shock.
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