Angina Flashcards
What is the treatment for angina?
Vasodilator drugs
What are the characteristics of angina?
Episodes of pain/pressure in anterior chest
What is the most common cause of angina?
Coronary artery blockages by atheromatous plaques
What are the risk factors for angina?
Smoking Obesity Diabetes Lack of exercise Hyperlipidaemia
During ischaemic conditions, what is released?
Mediators
What accumulates in ischaemic conditions?
Metabolic waste products
What do metabolic waste products do?
Metabolites stimulate nerve endings in the muscle and outermost layer of coronary arteries
What metabolites stimulate the nerve endings?
Potassium
Kinins
Prostaglandins
Adenosine
What are the 3 types of angina?
- Stable
- Unstable
- Variant
What is stable angina?
3-5 mins on exertion
When greater than usual demand on heart
Most common
What is unstable angina?
More dangerous
Still manageable
Risk of MI
What is variant angina?
Rare
Occurs at rest
Same time everyday
Very painful - no blockage - artery spasm
Why is unstable angina dangerous?
Sustained ischaemia -> necrosis -> more unpredictable
How does unstable angina occur?
Plaque with fibrous cap
Cap ruptures
Blood clot forms around the rupture -> blocks artery
What are the treatment aims?
Treat pain
Treat blockage - intervene in coronary arteries
Reduce demand - reduce heart rate/ workload OR dilate blood vessels to increase delivery
Improve exercise tolerance
Reduce risk of MI
Deal with plaques and stop them advancing
Correct imbalance between oxygen demand/supply
Increase coronary flow
Decrease cardiac workload
What do vasodilators do?
Mainly act on venous side of arterioles (some coronary, but not focused here), peripheral blood vessels
What are the aims of treatment affected by?
- Preload- increased preload = increased workload
- Afterload- increased afterload = increased workload
- Contractility- increased contractility = increased workload
What is preload?
Extent of muscle stretch before contracting. More stretch = more contraction
starling’s law
What is starlings law?
Force of contraction is proportional to resting length of muscle fibres. The most the heart is filled, the greater the degree of fibres are stretched. Greater force of contraction - increase volume of blood ejected (stroke volume)
What is afterload?
Resistance against which blood is ejected from the heart
Increased resistance = smaller vessels = greater work = increased oxygen consumption
How do you reduce afterload?
Dilate arterioles
How do you reduce preload?
Venodilation
OR
Depress myocardial contractility (venal/arterial dilation)/heart rate
What are organic nitrates?
Venous side
Dilate peripheral veins and arterioles
What are the aims of organic nitrates?
Reduce oxygen demand by reducing work of heart muscle