Presentations of IHD (CAD)
- Multiple possible initial presentations of IHD
- Chronic stable angina
- Unstable angina
- Acute myocardial infarction
- Sudden death
- Ischaemic cardiomyopathy presenting as CCF
Definition of AMI
Evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischaemia.
Detectiong of a rise and fall in cardiac biomarkers - preferable cardiac troponin and CK-MB with at least one of:
- Symptoms of acute myocardial ischaemia
- New or presumed new ST-T changes or new LBBB
- Development of pathological Q waves
- Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
- Identification of intracoronary thrombus at angiography or autopsy
Pathogenesis of AMI
Part of acute coronary syndromes which share a common pathogenesis: rupture of a 'vulnerable' atherosclerotic plaque in a coronary artery.
Left anterior descending STEMI changes
anterior free wall and septum (V1-V4 +/- L1 and aVL)
Circumflex and branches STEMI
Lateral free wall (V4-V6, L1 and aVL)
Right coronary artery STEMI
Inferior +/- posterior (leads 2, 3 and aVF inferior infarct, marked ST depression V1-V3 reciprocal changes of true posterior infarct)
Sustained ischaemic discomfort.
Often SOB, nausea, dizzy, anxious.
Management of AMI in ER
ECG taken and read within 10'
O2, IV line, sublingual GTN, morphine if needed, continuous ECG monitoring.
ECG divides into STEMI or NSTEMI
History: sustained symptoms of ischaemia.
ECG taken and read within 10', IV, O2, exam
ST up = or > 2.0mm in 2 consecutive chest leads or = or > 1.0mm in 2 limb leads in a vascular territory then either to angio or thrombolyse if no contraindications.
Angioplasty: if presentation <60' then door to balloon time <90'
Thrombolysis: presentation less than 12 hours then door to needle time <30'
Contraindications to thrombolysis
Absolute: active bleeding, past cerebral harmorrhage, recent (<3 months) stroke, recent major surgery (last 2 weeks)
Relative: marked HTN, pregnancy, known bleeding diathesis, oral anticoagulants, diabetic or haemorrhagic retinopathy, prolonged CPR, recent invasive procedure.
Difference in STEMI and NSTEMI management
Reason for different management is that neither primary percutaneous intervention (PCI) nor thrombolysis have shown a clear cut survival advantage with NSTEMI whereas there is a very clear cut survival advantage with both in STEMI.
Primary PCI all other factors being equal is superior to thrombolysis and in hospitals equipped and staffed for PCI is the preferred treatment.
Complicatiosn of AMI
- Dysrhythmias VT, VF, AF, AV block
- Severe systolic dysfunction: cardiogemic shock and CCF
- Myocardial rupture
- Mitral regurgitation
- Dressler's syndrome