Acute Coronary Syndrome

Introduction to Acute Coronary Syndrome

Spectrum of CAD comprising myocardial infarction with ST segment elevation (STEMI), or without ST segment elevation (NSTEMI) and unstable angina (UA) depending on clinical, ECG and enzyme changes.
Guidelines for management of acute coronary syndrome (ACS) are issued by ACC/AHA and ESC.

  • STEMI: Angina, ST ≥ 1 mm (in ≥ 2 adjacent Limb leads) or ≥ 2mm in 2 2 contiguous praecordial leads or New onset LBBB and Elevated Troponin
  • NSTEMI: Angina ST depression ≥ 1mm or T wave abnormalities, No ST segment elevation, Elevated Troponin level
  • Unstable angina: Rest Angina, ST or T wave abnormalities, No ST segment elevation, No rise in Troponin level

Clinical features of Acute Coronary Syndrome

  • Focused history
  • Chest pain similar in character to angina pectoris but greater in severity, longer in duration (30 mins), not relieved by nitrates, not specifically provoked by exercise or relieved by rest.
  • Autonomic disturbance: diaphoresis, vomiting, giddiness & anxiety
  • History of risk factors, previous MI/intervention, stroke/asthma/ bleeding tendencies.
  • Pulse: Tachycardia /bradycardia/ arrhythmia
  • BP: Normal /transient elevation/ hypotension
  • Pulmonary oedema

Differential diagnosis

  • Acute pulmonary embolism
  • Acute Pericarditis
  • Acute aortic dissection
  • Esophageal spasm
  • Peptic ulcer disease

Complications of Acute Coronary Syndrome

  • Arrhythmia
  • Pulmonary oedema.
  • Septal/chordae/myocardial wall rupture
  • Stroke
  • Ventricular aneurysm Pericarditis

Investigations

  • 12 lead ECG within 10 minutes of presentation with cheat pain. Serial
  • ECG if there is diagnostic uncertainty or change in clinical status.
  • In inferior wall MI: do a right sided
  • ECG (4VR) to exclude RV infarct (ST elevation >1 mm)
  • ECG diagnosis of STEMI in a setting of preceding LBBB is difficult but the followings are useful:
    • ST changes in the same direction
    • ST segment elevation > 7-8 mm
    • Coving of ST segment
    • Pathological Q wave in 2 consecutive leads and
    • Reciprocal changes
  • Cardiac enzymes:
    • Cardiac troponin I & T are released within 4 hrs of MI and remain elevated up to 2 weeks & is the most sensitive marker of myocardial damage. Useful in late presentation
    • MB-CK rises within 4-6 hour, peak in a day and disappears by the second day
  • Blood chemistry: Blood sugar, electrolytes (Na, K, Cl, Ca, Mg), urea, Cr, lipid levels, arterial blood gas
  • C-X ray: Cardiomegaly & Pulmonary
    oedema
  • Echocardiography: Regional wall motion abnormality, Pericardial effusion, septal/chordae/ papillary muscle rupture, MR, LV function, RV function, PAP
  • Coronary angiography: Delineate site(s) of lesion & number of vessels involved.

Management of Acute Coronary Syndrome

  • General
  • Oxygen (100% 2-4 L/min) via nasal
    prongs if SaO2 <90%
  • Set up an IV line
  • Dual antiplatelet therapy: ASA 300 mg stat; 75 mg daily + Clopidrogel 300 mg stat; 75 mg daily.
  • Short acting nitrates: Route: Sublingual (0.4 mg); Buccal (1-5 mg 6 hrly); Aerosol (400 ug per spray)
  • Long acting nitrates: Iso-sorbide dinitrate 10-20 mg tds. IV route: IV nitroglycerin (5-10 g/min)
  • Morphine: (2-4 mg) given slowly through IV canula
  • Lipid lowering drugs: statin 10-40 mg daily
  • ACEI: Captopril (6.25-12.5 mg daily),
    Lisinopril (2.5-10 mg daily depending on blood pressure status)
  • ARB: Valsartan (80 mg daily), lorsatan (12.5-25 mg daily). There is increased risk of hyperkalaemia, hypotension, and impaired renal function when angiotensin-II receptor antagonists are taken with ACE Inhibitors
  • Beta blocker: Carvedilol (6.25-12,5 mg daily) Metoprolol (25-50 mg daily).
  • CCB: Rate limiting such as verapamil (40 80 mg tds) & diltiazem (30-60 mg tds). Non rate limiting such as amlodipine (2.5-10 mg daily)
  • Anxiolytics: Diazepam 5mg daily
  • Stool softener: Liquid paraffin 15-30 mls nocte
  • Anticoagulant therapy
    • Heparin: Bolus of 60 units/Kg body weight followed by 12 units/Kg/hr. Heparin should not be given with streptokinase
    • LMWH: 1 mg/Kg given twice daily
  • Bed rest within the first 24 hours

Management of STEMI

  • Reperfusion therapy (pharmacological)
  • Indicated only in STEMI
  • Patient aged <75 years
  • Best benefit if given within 1-3 hours of AMI (“GOLDEN HOUR”). May be tried if patient report within 6-12 hrs thought benefits after 6 hrs is uncertain
  • Chances of successful reperfusion is about 50%
  • Streptokinase
    • Activates fibrinolytic system
    • Antigenic & dosage cannot be repeated until after at least 1 year
    • Dose 1.5 million units in 100 mls of normal saline given over 30-60 mins
  • Recombinant tissue plasminogen.
    activator (tPA)

    • Superior to and more expensive than streptokinase
    • Not antigenic
    • Preferred to SK if there is hypotension
    • Higher risk of intracerebral haemorrhage
  • Alteplase
    • Dose: 15 mg stat; then 0.75 mg/Kg (max: 50 mg) over 30 mins; then 0.5 mg/Kg (max: 35 mg) over 60 mins

Contraindications

  • Absolute Contraindications: Active bleeding, bleeding diathesis, stroke within 3 months, intracranial tumour.
  • Relative contraindications: Severe
    hypertension (> 180/110mm Hg), recent trauma/CPR/c surgery, Active peptic ulcer, Oral anticoagulant therapy, Advanced liver diseases, Active cavitation PTB and Pregnancy and within 1 week post-partum

Medical intervention

  • Refer to centres for percutaneous
    coronary intervention where available and affordable
  • Ballon angioplasty, Stenting (Bare metal Thrombectomy

Surgical intervention:

  • Refer for Coronary artery bypass graft (CABG) where available and affordable
  • Indicated in: Triple vessel disease, Proximal Left main coronary artery disease, Double vessel disease with proximal LAD lesion & Calcification

Adverse drug reactions

  • Nitrates may cause headache and
    tolerance.
  • Contraindicated in bradycardia and when SBP <90 mmHg
  • Beta blockers may precipitate
    bradycardia, Heart Failure, asthma and hypotension
  • Thrombolytic agents may cause bleeding
  • Heparin may induce thrombocytopenia

Prevention

  • Life style modifications including regular exercise, optimum weight, high fibre and low saturated fat diet; cessation of cigarette smoking and moderate alcohol intake
  • Treatment of hypertension, diabetes and hyperlipidaemia
  • Others
    • Educate on benefits, outcome and complications of patient’s condition and treatment modalities
    • Emphasize primary and secondary preventive measures as essential irrespective of treatment modality offered