Disease and Clinical Features of MI

Question 1

Define an MI

Answer 1

Ischaemic necrosis of the myocardium as a result of acute occlusion of a coronary artery

Question 2

What is included in the clinical definition of MI?

Answer 2

1. Symptoms - characteristic of myocardial pain
2. ECG changes - characteristic of myocardial infarct/ischaemia
3. Cardiac enzymes - evidence for cardiac myocyte necrosis (without enzymes → Acute Coronary Syndrome)

Question 3

What is unstable angina and how should it be treated?

Answer 3

Change in character, duration, frequency, severity of chest pain

Treat as acute coronary syndrome

Question 4

Name some common causes of MI

Answer 4

Atheroma,

Hypercoagulability,

Aortic dissection - flap occlusion,

Coronary artery dissection/aneurysm

Question 5

What are the major symptoms of MI?

Answer 5

Chest pain - ususally sudden onset, crushing, >20 mins, may radiate

Sweating

Pallor

Nausea

Question 6

What are the signs of MI?

Answer 6

Excess sympathetic tone - Tachycardia, Hypertension

or Excess parasympathetic tone - Bradycardia and Hypotension

Impaired left ventricle function → hypotension, lung crackles, murmur

Question 7

What are the stages of ECG changes in MI?

Answer 7

ST depression - not always there - ischaemia + partial occlusion

T wave peaking - ischaemia (or hyperkalaemia)

ST elevation - ischaemia + total artery occlusion

T wave inversion - ST segment slowly → baseline

Q wave development

Question 8

What is indicative of a LBBB?

Answer 8

Wide QRS

Broad +/- notched R wave - prolonged upstroke in V5, V6 (and 1, AVL)

Left axis deviation may/may not be present

Question 9

What are the major cardiac enzymes implicated in MI?

Answer 9

Troponin (T or I)

Released within 4-6 hours, raised up 2 weeks after Infarction (but also rises in PE, septicaemia, renal failure, cardiac trauma)

Other enzymes: MB creatinine kinase, Lactate dehydrogenase-1

Question 10

What is the immediate treatment of MI?

Answer 10

AMONAC

Antiemetic, Morphine, O₂, Nitrate, Aspirin, Clopidogrel

Cyclizine, Morphine/Diamorphine, GTN, Aspirin, Clopidogrel

Question 11

What is the treatment for STEMIs?

Answer 11

Reperfusion therapy <12 hours

Immediate Percutaneous Coronary Intervention (PCI) - most effective <90 mins

or

Thrombolysis

Question 12

What does Percutaneous Coronary Intervention involve?

Answer 12

Balloon Angioplasty +/- stenting, with drugs:

Glycoprotein IIb/IIIa Inhibitors (Abciximab, Eptifibatide) - Antiplatelet - reduce risk of immediate vascular obstruction

Unfractioned Heparin

Question 13

What does thrombolysis involve?

Answer 13

Recombinant tissue plasminogen activator: Plasminogen → Plasmin → Break down fibrin

Telecteplase

Given with LMWH

Question 14

What is the treatment and management for an NSTEMI?

Answer 14

LMWH, or unfractioned Heparin

Take troponin 12 hours after onset

GRACE system >3% CV event risk → Coronary angiography +/- PCI (within 96 hours)

<3% → non-invasive ischaemia testing

Question 15

For confirmed MI, what drugs should be given?

Answer 15

MI5 (AABCS)

Aspirin - Antiplatelet

ACE inhibitor - Decrease BP and cardiac workload

Beta blocker - Bisoprolol - Slow HR and contractility

Clopidogrel - Antiplatelet

Statin - Lower cholesterol

Also warfarin/fondaparinux (anticoagulants) and Insulin if required