Acute Myocardial Infarction Flashcards
What is the cause of chronic stable angina?
Fixed stenosis
Demand led ischaemia
What is an acute coronary syndrome?
Any acute presentation of coronary artery disease
What are the two types of MI?
STEMI
NSTEMI
What are the causes of acute coronary syndrome?
- dynamic stenosis (subtotal or complete occlusion)
- supply led ischaemia
- unpredictable
- dangerous
What are the factors affecting plaque rupture/fissure?
- Lipid content of plaque
- Thickness of fibrous cap
- Sudden changes in intraluminal pressure or tone
- Bending and twisting of an artery during each heart contraction
- Plaque shape
- Mechanical injury
What are the stages in the platelet cascade?
- Initiation
- Adhesion
- Activation
- Release of activators
- Surface receptors
- Amplification of activation
- Inflammatory Cascade
- Fibrin rich thrombus formation
What ECG changes might you see?
ST elevation
T wave inversion
Q waves
What are the categories for diagnosis a STEMI?
> 1mm ST elevation in 2 adjacent limb leads
> 2mm ST elevation in at least 2 contiguous precordial leads
New onset bundle branch block
When will ST elevation be visible?
First few hours
When will Q wave formation and T wave inversion occur?
First day
What might be suggestive of an old MI?
Q waves +/- inverted T waves
What leads will be affected in an anterior MI?
V1-V6
What leads will be affected in an anteroseptal MI?
V1-V4
What leads will be affected in an anterolateral MI?
I, avL, V1-V6
What leads will be affected in an inferior MI?
II, III, AVF
Describe the use of CK enzymes?
- peaks in 24 hours
- also in skeletal muscle and brain
Describe the use of troponins?
- Highly specific for cadiac muscle damage
- Can detect tiny amounts of myocardial necrosis
What is the mode of action of aspirin?
Aspirin inhibits COX preventing the formation of TXA 2
What is the mechanism of clopidogrel?
Clopidogrel blocks the ADP receptor
What are the indications for thrombolysis or PCI?
1. Chest pain suggestive of acute myocardial infarction More than 20 minutes less than 12 hours 2. ECG changes acute ST elevation NEW left bundle branch block (LBBB) 3. No contraindications
What are the risks of thrombolysis?
-Failure to re-perfuse
-Haemorrhage – Minor
> Major
> Intracranial haemorrhage 0.5 –
2.0%
- Hypersensitivity
What is the early treatment of STEMI?
- Analgesia - diamorphine iv
- Anti-emetic - iv
- Aspirin - 300 mg and Clopidogrel 300 mg
- GTN-ifBP>90mmHg
- Oxygen - if hypoxic
- Primary angioplasty
- Thrombolysis – if angioplasty not available within 90 minutes
What are the complications of acute MI?
- Death
- Arrhythmic complications
- Structural complications
- Functional complications
What structural complications can occur from acute MI?
-Cardiac rupture
-Ventricular septal defect
-Mitral valve regurgitation
-Left ventricular aneurysm formation
-Mural thrombus +/- systemic emboli
-Inflammation
>Acute pericarditis
>Dressler’s syndrome
