Acute Myocardial infarction

Question 1

what is an MI?

Answer 1

Cell death secondary to ischaemia

Question 2

What commonly causes MIs?

Answer 2

Atherosclerotic plaque rupture followed by thrombosis formation, completely occluding the vessel.

(if atherosclerotic plaque grows slowly, collateral vessels may develop)

Question 3

Symptoms of MI?

Answer 3

Severe central crushing chest pain that radiates to left arm or jaw
Sweating, breathlessness, nausea, pallor

Question 4

Treatment of Acute MI?

Answer 4

O2
Aspirin 300mg
Cannulate and cardiac monitor
Diamorphine 2-5mg IV and metoclopramide 10mg
Thrombolysis (unless contraindicated)
    - rt-PA/Alteplase
    - Streptokinase
IV atenolol 5mg

Question 5

Contraindications for thrombolysis?

Answer 5

Previous haemorrhagic cerebrovascular event
Any cerebrovascular event in the last 6 months
Recent GI bleed
Bleeding diathesis (haemophilia, VW disease, OI, Turner’s, Down’s, Ehler’s Danlos syndrome, Factor XI deficiency……..)
Pregnancy
Operation or invasive procedure in the last month

Question 6

What investigations would you do for someone suspected of MI?

Answer 6

Blood tests - cardiac enzymes (CK-MB, Troponin)
U/E (for renal function in case of cardiogenic shock and hyperkalaemia that may need to be corrected)
Blood Glucose (may be diabetic)
FBC - anaemia and post-MI leucocytosis

ECG!!

Question 7

What ECG changes would you expect to see in someone with an MI?

Answer 7

ST elevation (may not be)
T wave inversion (after 24hrs)
Q waves (after 24hrs)

Question 8

Types of MI seen in ECG changes
Anterior (LAD)
Inferior (RCA, circumflex)
Lateral (circumflex)
Posterior (RCA, circumflex)
Anterolateral (proximal LAD)

Answer 8

Anterior - ST E in V1-4
Inferior - ST E in II, III, AVF
Lateral - ST E in V4-6
Posterior - ST depression in V1-2, R wave in V1-2
Anterolateral ST E in V1-6

Question 9

Complications of an acute MI (2-7 days)

Answer 9

Arrhythmia - VT, VF, SVT, Heart block
PE
Papillary muscle rupture > valve prolapse
Interventricular septum rupture
Free wall rupture

Question 10

Complications of an acute MI (>7 days)

Answer 10

Arrhythmias - VT, VF, SVT, Heart block
Cardiac failure
Dressler's syndrome
LV aneurysm
Mural thrombosis > systemic embolization