Heart Flashcards
Define Acute plaque change.
It is the unpredictable and sudden conversion of a stable atherosclerotic plaque into an unstable and potentially fatal atherothrombotic lesion through rupture/ superficial erosion/ ulceration/ fissuring/ deep haemorrhage.
- It is usually associated with inflammation.
- Leads to formation of a superimposed thrombus.
- Partially /completely occludes they coronary artery
What is an Ischemic Heart Disease? What are its causes? Give examples.
IHD is a group of disordered which occur due to myocardial ischemia, which is due to imbalance between myocardial supply and cardiac demand for oxygenated blood.
Causes are:
- Decreased supply of blood:
- Atheromatous narrowing of one or more epicardia coronary arteries (CAD)
- Risk depends on: Extent and severity of occlusion, type of atheromatous plaque (vulnerable or stable), degree of stenosis (70% is critical), rate of development (slowly developing plaque allows time for collaterals to grow) - Increased demand : Cardiac hypertrophy, tachycardia
Examples of IHD: There are 4 types.
MI, Angina pectoris, Chronic IHD , Sudden Cardiac Death
What is a stable and a vulnerable plaque.
Stable plaque
- Dense collagenous fibrous cap
- Minimal inflammation
- Less foam cells and less necrotic core
- Not likely to rupture
Vulnerable plaque:
- Thin fibrous cap
- Lot of inflammation and foam cells, with extra cellular lipids
- Necrotic core is large
- Likely to rupture
Define angina pectoris. Types.
It is a type of IHD characterised by:
- Recurrent and paroxysmal attacks of
- Substernal or precordial chest pain
- Caused by transient (15s to 15 min) ischemia
- which is not sufficient to cause myocardial necrosis
Types: 3 types
1) Stable angina - substernal chest pain induced by exercise
2) Variant/Prinzmetal Angina - spasm of coronary artery having atherosclerosis, not related to physical activity, heart rate,
or blood pressure. Occurs during rest or sleep.
3) Unstable Angina (it is a type of Acute coronary syndrome)- rupture of an atherosclerotic plaque complicated by thrombosis/ embolization/vasospasm. May be a precursor of MI.
Define MI. What is the etiology/cause?
Coagulative necrosis of cardiac muscle due to prolonged severe ischemia.
Etiology:
- Coronary Arterial Occlusion: (90% cases) Due to Acute Plaque change
- Other causes (10% cases) : Vasospasm/Emboli in left atrium causing fibrillation/Amyloidosis etc.
Pathogenesis of M.I.
- Acute Plaque Change: Sudden conversion of stable plaque into a fatal atherothrombotic lesion. May be due to:
- Rupture/Fissure: Thrombogenic plaque contents released–> thrombus formation and occlusion
- Erosion: Thrombogenic subendothelial collagen exposed– thrombosis and occlusion
- Hemorrhage into plaque: It grows in size and occludes lumen - Platelet activation, adhesion and aggregation- formation of microthrombi- partial or complete occlusion
- Vasospasm: Due to TxA2 and other mediators released by platelets
- Coagulation: by tissue factor and other mediators - formation of a growing thrombus
- Complete occlusion: Usually within minutes
- Myocardial necrosis: Ischemic, coagulative necrosis of the area supplied by the occluded artery (Area at risk)
What are the myocardial response in MI with timing.
- Onset of ATP deception : within sec
- Loss of contractility: <2mins
- ATP reduced to 50% of normal: 10 mins
- ATP 10% of normal : 40 mins
- Irreversible injury: 20-40 mins
- Micro vascular injury: >1 hour
What is the TTC stain for gross examination of MI?
If MI is less than 12 hours old, TTC stain can be used.
TTC= Triphenyl Tetrazolium chloride
Tissue section immersed in TTC:
- Normal Myocardium appears red (LDH intact)
- Infarcted area appears white (LDH has leaked out and is lost)
