Acute Management of Myocardial Infarction

Introduction

• Stable angina• Acute coronary syndrome– STEMI– NSTEACS

• NSTEMI• Unstable angina

Introduction

• 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

Introduction

•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

History

• 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

Examination

• Usually no signs• Signs of precipitants (e.g. anaemia, infection,

thyrotoxicosis, arrhythmias), risk factors, other atherosclerotic diseases (PVD, stroke), complications (e.g. MR, CHF)

Investigations

• 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,

LDH– Stable angina and unstable angina – normal– NSTEMI, STEMI – raised

Investigations

•FBE – anaemia, infection•UECR, coagulation study – ability to take contrast and

undergo PCI•FBG, lipid profile (within 24h) – DM,

hypercholesterolaemia•CXR – r/o aortic dissection, pneumonia, pneumothorax,

interstitial lung disease

Investigations

• 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

STEMI

• 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

LMWH)

– 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

STEMI

• 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

UA and NSTEMI

• 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

admission)– Statins, aspirin and clopidogrel, ACEI (or ARB), β-blocker

(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

• Presentation– ST segment deviation ≥0.5mm– ↑cardiac enzymes

• Recent (≤24hr) severe angina

Risk Stratification

• Risk stratification of NSTEACS – “HEART DOC”– Haemodynaic compromise– ECG changes– Arrhythmia– 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

Summary

• MOAN• 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

• PCI vs CABG– Advantage of PCI – less invasive, less peri-operative

stay, morbidity and mortality– Advantage of CABG – higher chance of

revascularization– 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