CVR - Ischaemic heart disease & hypoxia Flashcards
What is ischaemic heart disease?
Heart problems caused by narrowed coronary arteries
What are the signs and symptoms of ischaemic heart disease?
- Angina/Chest pain
- Heart rhythm problems
- Nausea
- Fatigue
- Weakness or dizziness
- Diaphoresis
What are the non-modifiable risk factors of ischaemic heart disease?
- Gender
- Age
- Ethnicity
- Previous history of CVD
What are the modifiable risk factors of ischaemic heart disease?
- High BP
- Smoking
- Diet
- Sleep
- Stress
- BMI]
- Certain medication
What can obstruct coronoary blood flow?
- Atheroma
- Thrombosis
- Spasm
- Coronary embolus
- Coronary ostial stenosis
- Coronary arteritis
What can cause a general reduction in levels of oxygenated blood flow to the myocardium?
- Anameia
- Carboxyhaemoglobulinaemia
- Hypotension
Describe the pathophysiology of atherosclerosis
- Dysfunctional endothelial cells and retention of lipoproteins
- This leads to increased expression of monocyte interaction
- Other immune cells internalise the LDLs to form foam cells
- As this progresses a plaque forms and over time this can result in more infiltration and proliferation of the tunica media smooth muscle cells
- This protects the plaque
How does a plaque become stable?
The production of TGF-beta and T-reg cells and macrophages maintains the fibrous cap quality by being a potent stimulator of collagen production in the smooth muscle cells above
How is a vulnerable plaque formed and how does this lead to a thrombus?
- If the inflammatory status of the core of the plaque remains unresolved, it leads to thinning of the fibrous cap
- These thin areas are then more susceptible to rupture
- When they rupture, the plaque releases many pro-coagulant factors and also recruits many.
- This leads to a high number of platelets forming which clump and form a thrombus
What is the role of the collaterals in the heart for acute and chronic patients?
- When the heart is ischaemic or hypoxic, the collaterals respond to restore blood flow by dilating and angionesis
- In an acute episode, the blood flow is restored within a month
- In chronic atherosclerosit patients, slow occlusion-collateral vessels can develop at the same time while the atherosclerosis becomes more severe, but eventually the atherosclerosis can be worsening faster than the collaterals forming and dilating
What is myocardial infarction?
When, after an accute occlusion, the area of muscle has no or little blood flow which means that it cannot sustain cardiac muscle function
What occurs after an MI?
- Small amounts of collateral open and blood seeps into the infarcted area
- Local blood vessels dilate and area becomes overfilled with stagnant blood
- Muscle fibres use all the remaining oxygen , haemoglobin becomes deoxygenated, leads to bluish hue, and blood vessels appear engorged despite lack of blood flow
- Eventually cardiac muscle will die
What is systolic stretch?
In an MI, part of the heart stretches because the tissue is dead and cannot contract so pools with blood
This can lead to ventricular rupture
State the serum markers in patients with suspected acute MI
- Troponins
- Creatine kinase
- Lactate dehydrogenase
- Serum aspartate aminotransferase
What does an NSTEMI show on an ECG and therefore indicate?
- ST depression and T wave inversion
- Unstable angina
What does an STEMI show on an ECG and therefore indicate?
- ST elevation with T wave inversion
- Acute MI
How do you find out if someone has a stable angina?
- To see changes from normal ECG, do an exercise stress test
- During stress test might see an ST depression indicating IHD
What is a coronary angiography?
- Using a cather, iodine is put into the coronary vessels
- Then fluid is then seen through a radiographic fluoroscopic examination of the heart
What are the pharmocological treatments for angina and how do they work?
- HMG-CoA reductase inhibitors: lipid lowering drug
- Bile acid sequestrants: Increase the fecal loss of cholesterol
- Calcium channel blockers: Causes relaxation in cardiac smooth muscle and coronary vasodilation
- ACE inhibitors: Improve vascular endothelial function and vasodilate
- Beta-blockers: Inhibit sympathetic stimulation of the heart, reducing heart rate and contractility, reducing myocardial oxygen demand
- Antiangnal agents: Relieves ischaemia by reducing myocardial cellular sodium and calcium overload
- Platelet aggregate inhibitors: May exert protection agains atherosclerosis through inhibition of platelet function
- Nitrates: Causes systemic vasodilation which reduces myocardial oxygen demand
What is PCI?
Percutaneous coronary intervention:
Angiography and stent placement in affected vessel, stent compresses plaque
What is CABG
Coronary artery bypass grafting:
A vessel from another part of the body is used to create a graft which allows blood flow around the blocked or narrowed coronary artery
