Myocardial Infarction Flashcards
What is the main peri-infarct cause of death?
Ventricular arrhythmias
How long post MI do myocardial wall and muscle rupture generally occur?
4-7 days post infarction
What is the most likely cause of a Q wave MI?
Completely occlusive thrombus
Evolving changes of Acute MI
First few hours = ST elevation
First day = Q wave formation and T wave inversion
Old MI = Q waves +/- inverted T waves
What ECG changes must be present to diagnose a STEMI?
> 1mm ST elevation in 2 adjacent limb leads OR
2mm ST elevation in at least 2 contiguous precordial leads OR
New onset bundle branch block
Which ECG leads are affected in an inferior infarction?
II, III and aVF
Which ECG leads are affected in an anterior infarction?
V1-V6
Which ECG leads are affected in an anteroseptal infarction?
V1-V4
Which ECG leads are affected in an anterolateral infarction?
I, aVL, V3-V6
Early treatment of STEMI
Morphine IV Oxygen Nitrates Aspirin 300mg, Clopidogrel 300mg IV anti-emetic Primary angioplasty or thrombolysis
What is Aspirin’s mode of action?
Inhibits the COX enzyme, preventing the production of prostaglandin and thromboxane A2 from arachidonic acid
Thromboxane A2 would normally aid the expression of the GP IIb/IIIa binding site on the platelet, allowing for fibrinogen binding
What is Clopidogrel’s mode of action?
Inhibits ADP-induced platelet aggregation by irreversibly binding to the ADP platelet receptor
ADP is usually necessary for activation of the G IIb/IIIa receptor
Risks of thrombolysis?
Failure to perfuse
Haemorrhage
Hypersensitivity
Complications of Acute MI?
Death
Arrhythmic
Structural
Functional
What arrhythmic complications might arise from an MI?
Ventricular fibrillation
What structural complications might arise from an MI?
Cardiac rupture Ventricular septal defect Mitral valve regurgitation Left ventricular aneurysm formation Mural thrombus +/- systemic emboli Inflammation Acute pericarditis Dressler's syndrome
What functional complications might arise from an MI?
Acute ventricular failure (left, right or both)
Chronic cardiac failure
Cardiogenic shock
What do troponins measure?
Embolisation
Microvascular circulation
Myonecrosis
Almost absolute myocardial specificity/high sensitivity
Four Phases of Cardiac Rehab
1 - In Patient
2 - Early post discharge period
3 - Structures exercise programme (usually hospital based)
4 - Long term maintenance of physical activity and lifestyle change (usually community based)
What is the first stage in the development of atherosclerosis?
Endothelial dysfunction triggered by damage to the endothelium (e.g. smoking, hypertension, hyperglycaemia)
What types of early changes occur to the endothelium in the development of atherosclerosis?
Pro-inflammatory
Pro-oxidant
Proliferative
Reduced nitric oxide bioavailability
What is the role of LDL in the development of atherosclerosis?
After initial changes to the endothelium, LDL moves into the subendothelial space, causing fatty infiltration
What is the role of macrophages in the development of atherosclerosis?
Macrophages phagocytose oxidised LDL in the sub endothelium, and slowly turn into large foam cells
The death of these macrophages further propagates inflammatory processes
What is the role of smooth muscle cells in the development of atherosclerosis?
Smooth muscle proliferation and migration from the tunica media into the intimate results in formation of a fibrous capsule covering the fatty plaque formed from the macrophage foam cells
