Acute Management of Myocardial Infarction

Acute Management of
Myocardial Infarction
Henry Yao
Intern, Royal Melbourne Hospital
• Stable angina
• Acute coronary syndrome
• Unstable angina
• Stable angina arise when lumen stenosis >70% →
impaired blood supply to heart only during on exertion or
increased metabolic demand
• Acute coronary syndrome arise when vessel becomes
occluded by thrombus
– Unstable angina – when atherosclerotic plaque shoot
of embolus downstream to cause microinfarct
– NSTEMI – when necrosis confined to endocardial
layers (most susceptible to ischaemia)
– STEMI – when full thickness necrosis of the
ventricular wall occurs
Stable angina – normal ECG, normal troponin
Unstable angina – normal troponin
NSTEMI – elevated troponin
STEMI – elevated ST segment
• Criteria for thrombolysis or PCI (i.e. STEMI)
– >1mm elevation in 2 contiguous limb leads
– >2mm elevation in 2 contiguous precordial leads
– New onset LBBB
• All causes central crushing chest pain or tightness radiating
to arm, neck and jaw
Stable angina usually last less than 20 minutes,
precipitated by exertion and relieved by rest or nitrates
ACS usually lasts more than 20 minutes, sudden onset
usually at rest and not relieved by rest
All associated with sx of ↓cardiac output – SOB, presyncope
or syncope, palpitations
All associated with sx of sympathetic activation – nausea,
vomiting, sweating, pale, clammy
All associated with risk factors – HTN, high cholesterol, DM,
smoking, family history
• Usually no signs
• Signs of precipitants (e.g. anaemia, infection,
thyrotoxicosis, arrhythmias), risk factors, other
atherosclerotic diseases (PVD, stroke), complications
(e.g. MR, CHF)
• Resting ECG (on arrival)
– Stable angina – normal
– Unstable angina or NSTEMI – ST depression or T
wave inversion
– STEMI – ST elevation → Q wave (permanent) → T
wave inversion (in this order)
• Cardiac enzymes – Troponin, CKMB/CK ratio, AST,
– Stable angina and unstable angina – normal
– NSTEMI, STEMI – raised
• FBE – anaemia, infection
• UECR, coagulation study – ability to take contrast and
undergo PCI
FBG, lipid profile (within 24h) – DM,
CXR – r/o aortic dissection, pneumonia, pneumothorax,
interstitial lung disease
• Note: Troponin vs CKMB
• CKMB – rise in 4hr, elevated for 72hr
• Trop – rise in 8hr, elevated for 5 days (trop I) and 10 days
(trop T)
If trop –ve → repeat in 8hr → last serial trop done 8hr
after sx resolves
• CKMB can be used to detect second infarcts
Acute Management
Oxygen therapy
GTN (½ sublingual tab)
Aspirin 300mg
IV morphine 2.5~5mg + IV metoclopramide 10mg
Hospital Management
• Aspirin, GTN, morphine, oxygen if not already given
• Monitor oximetry, BP, continuous ECG
• 12 lead ECG, IV access, cardiac enzyme
• Reperfuse ASAP (within 12hrs of onset of sx – i.e.
before MI is complete):
– Antiplatelet therapy (aspirin and clopidogrel ±
GPIIb/IIIa inhibitor)
– Anticoagulation agent (unfractionated heparin or
– Immediate PCI or fibrinolytic therapy –
PCI has higher reperfusion rate and is better if pt
present > 1hr but thrombolysis is gold standard if pt
arrive within an hour
• Subsequent management (start during this hospital admission)
– Statins, aspirin and clopidogrel, ACEI (or ARB), β-blocker (if
CI then CCB)
– Anticoagulation therapy to prevent thromboembolism
(warfarin for 6mos if large anterior MI, esp if echo show large
akinetic/dyskinetic area, aneurysm or mural thrombus)
– Nitrates PRN
– Cardiac rehabilitation
• Antiplatelet post stent
– Aspirin for life
– Clopidogrel for at least 6wks for metal stent
– Clopidogrel for at least 12mos for drug eluting stent
– Drug eluting stent have lower early re-stenosis rate c.f. bare
metal stent however have a problem of late thrombosis
Trop of 0.1
• Stabilize acute coronary lesion
– Anti-platelet (aspirin and clopidogrel ± GPIIb/IIIa inhibitor)
– Anti-thrombin (UFH or LMWH)
– Anti-ischaemia (β-blocker if CI then CCB, consider
nitrates, morphine)
High risk – urgent angiography ± PCI
Low risk – arrange stress tests
Subsequent management (start during this hospital
– Statins, aspirin and clopidogrel, ACEI (or ARB), βblocker (if CI then CCB)
– Nitrates PRN
– Cardiac rehabilitation
Risk Stratification
• TIMI Score (Para Sea)
• Historical
– PHx – known CAD (stenosis ≥ 50%)
– Age>65
– ≥3 RFs for CAD
– Aspirin use in past 7d
– ST segment deviation ≥0.5mm
– ↑cardiac enzymes
• Recent (≤24hr) severe angina
Risk Stratification
• Risk stratification of NSTEACS – “HEART DOC”
Haemodynaic compromise
ECG changes
Renal failure
Troponin rise
Diabetes mellitus
Ongoing chest pain
Cardiac bypass anytime or PCI in last 6months
Having 1 of these → high risk group
Stable Angina
• Statins, aspirin (or clopidogrel), ACEI, β-blocker
• Nitrates – sx relief or prophylaxis (patch or tablets but
must have 8h nitrate free period/day)
Wholistic care (all IHD):
• Lifestyle change – quit smoking, eat healthy, exercise
more, avoid excessive exertion or stress
Risk factor control – HTN, high cholesterol (keep
<4mmol/L), DM
• Assess depression, level of support
ECG, troponin, R/O DDx
Code AMI
Reduce time to PCI
Quiz 1 - Complications
• Early (0~48h)
– Any arrhythmias – worry about AF, VT, VF, CHB
– LVF → cardiogenic shock
Medium (2~7d)
– Any arrhythmias – worry about AF, VT, VF, CHB
– LVF → cardiogenic shock
– Rupture of papillary muscle (→MR), IV septum, LV wall → acute
cardiac failure → APO → death
Late (>7d)
– Any arrhythmias – worry about AF, VT, VF, CHB
– Cardiac failure
– LV aneurysm → mural thrombus → thromboembolism
– Dressler’s syndrome (3~8wk) – recurrent pericarditis following AMI
(Hence why β blockers given initially → prevents arrhythmia as well as
rupture of cardiac muscle)
Quiz 2
• Contraindication for thrombolysis
Past allergic reaction, past streptokinase use
Past stroke – haemorrhagic (ever), ischaemic (6mos)
Brain tumour/trauma
Recent bleeding or risk of bleeding – e.g. GI
bleeding, liver disease
– Recent surgery
– Hypertension
– Pregnancy
Quiz 3
– Advantage of PCI – less invasive, less peri-operative
stay, morbidity and mortality
– Advantage of CABG – higher chance of
– PCI over CABG – single or double vessel disease,
inability to tolerate surgery
– CABG over PCI – triple vessel disease or left main
disease, diabetes mellitus, failed PCI
© Copyright The University of Melbourne 2009