Wk.8 L3 - Infarction

Question 1

LO

Answer 1

Myocardial Infarction and Stroke
* What is CVD
* Ischemia vs Infarction
* Types of stroke
* Types of MI
* Clinical manifestations and diagnostics
* Complications of MI and Stroke

Question 2

CVD

Answer 2

Impacts aussies more than any other disease (1/4 deaths)

Question 3

Ischemia vs Infarction

Answer 3

Ischemia:
- Oxygen supply-demand imbalance
- Occlusion of the coronary or cerebral arteries
- Reduced provision of oxygen & increased demand
- Outcomes depend on the time to resolve the mismatch
- Transient ischemic attack (TIA) Myocardial stunning
- Short and reversible injury (apoptosis)

Infarction:
- Irriversible tissue death from ischemia as cells have undergone necrosis

Question 4

Occluding events

Answer 4

Sudden and complete blockage leads to the onset of symptoms

Atherosclerosis + Thrombosis:
- Disruption of fibrous cap exposes fatty streak
- Fatty streak is thrombogenic & platelets promote clotting

Embolism:
- Material dislodges from a large vessel and lodges in a small vessel
- stroke or MI = Left atrial fibrillation enters systemic circulation
- pulmonary embolism = Venous or RA clot enters pulmonary circulation

Question 5

Cellular and Functional Consequences: Ischemia

Answer 5

Heart and brain require high energy

No nutrients or oxygen:
- heart: contraction ceases
- brain: neurotransmission ceases

Cardiomyocyte cell death:
- replaced with fibrous scar tissue

Neuronal cell death:
- cells not replaced by new networks
formed (“neuroplasticity”)

Question 6

MI and Stroke: Risk Factors

Answer 6

Modifiable:
* Tobacco and alcohol use
* Obesity and sedentary lifestyle
* Diabetes, dyslipidaemia
* Systemic Hypertension and Atherosclerosis

Non-modifiable:
* Age, race and ethnicity
* Familial history
* Male sex
* Clotting disorders

Question 7

Types of Stroke

Answer 7

Ischemic: Arterial blockage
- Thrombosis or embolism
- ~85% of strokes

Hemorrhagic: Arterial break
- Aneurysm
- ~15% of strokes

Important to confirm the type of stroke before treatment

Question 9

Clinical Manifestation and Diagnostics: Stroke

Answer 9

• Headache and confusion

Focal neurological defects:
- Unilateral weakness or paralysis
- Numbess/ weakness
- Blurred vision
- Slurred speach
- Difficulty understanding speach

Atherosclerotic plaques usually in:
- Internal carotid
- Middle cerebral artery

Question 10

Types of Myocardial Infarction

Answer 10

Divided into 5 subclasses
Type 1:
- Plaque rupture or thrombosis (Most common)

Type 2:
- Oxygen supply/demand mismatch

Type 3:
- Death w/o ischemic biomarkers

Type 4:
- Death following percutaneous coronary intervention

Type 5:
- Death following coronary artery bypass graft

Question 11

Clinical Manifestation and Diagnostics: MI

Answer 11

Majority of MI result from CAD
- Crushing chest pain
- Pain in jaw or left arm

Women may experience “atypical” symptoms (silent MI)
- Nausea, pallor and fatigue

Follow up with ECG and biomarker studies

Question 12

Left Ventricular Prominence

Answer 12

Atherosclerotic plaques are usually located in:

Left anterior descending (LAD):
- 40-50% cases

Right coronary artery (RCA):
- 30-40%

Left circumflex artery (LCx):
- 15-20%

All affecting LV wall, impacting the ability to pump O2 blood to body

Question 13

Complications following infarction

Answer 13

Death (cardiac or brain)

Stroke
* Seizures
* Persistent neurological deficit
* Hydrocephalus

Myocardial Infarction
* Arrhythmia
* Pericarditis
* Myocardial rupture
* Ventricular aneurysm
* Heart failure

Creates a greater risk of further stroke and MI