Drug treatments for cardiovascular disease 3 & 4 - ischaemic heart disease Flashcards
Complete the diagram on the imbalance in demand and supply is ischaemic heart disease
What compound is important in regulation of coronary blood flow?
Endothelium-derived relaxing factor (nitric oxide)
How does NO causes relaxation of coronary blood vessels?
- Sheer stress - the sheer stress caused by the flow of fluid against the walls of the BV (resistance) increases
- Causes influx of Ca2+ into endothelial cells
- Ca2+ acts as co-factor for nitric oxide synthase
- Converts arginine to NO
- NO is permeable to cell membranes - can pass from endothelium (where its made) to smooth muscle cells
- NO causes GPT -> Cyclic GMP
- Cyclic GMP increase causes relaxation
What systems regulate end diastolic volume (preload)?
Sympathetic system
RAAS, (contractility of venules, Na+ and H2O retention)
How does cGTN cause vasodilation of coronary vessels?
cGMP stimulates the enzyme that dephosphorylates myosin light chain
Leads to relaxation of smooth muscle
Complete the diagram on GTN spray action.
What is heart rate regulated by?
Sympathetic system/ Ca2+
What is contractility regulated by?
Sympathetic system/Ca2+
What is total peripheral resistance regulated by?
Sympathetic system, RAAS
What 4 factors affect regulation of cardiac workload?
- End Diastolic Volume (preload)
- Heart Rate
- Contractility
- Total peripheral resistance
What is the definition of stable angina?
A predictable pattern of pain during exercise that is relieved by rest
What 2 things are drug treatments for stable angina designed to do?
Drug treatment designed to decrease work done by the heart and/or increase blood supply and treat risk factors.
Complete the diagram on the actions of nitrates
What are the side effects of nitrates?
- Postural hypotension
- Headache
- Dizziness
What does GTN spray stand for?
E.g. Glyceryl trinitrate (GTN)
How do nitrates cause reflex tachycardia?
Due to activation of sympathetic nervous system.
Baroreceptors detect decrease in BP so release noradrenaline to increase HR to increase BP
How is reflex tachycardia treated?
If treatment causes reflex tachycardia, then should look to block effects of sympathetic nervous system using a beta blocker, such as bisoprolol.
What do beta blockers do?
Decrease frequency and force of contraction which decreases cardiac output.
Beta blockers also inhibit renin release from kidney and so inhibit RAAS.
What are the side effects of beta blockers?
- Bronchoconstriction
- Fatigue
Which patients are beta blockers contraindicated in?
Contraindicated in patients with peripheral vascular disease - Raynaud’s disease
Name an example of a beta blocker
Bisoprolol
What are the 3 types of calcium channel antagonists and what is the difference between them?
Phenyalkylamines/Benzothiazepines cause decrease in frequency and force of contraction
Dihydropyridines cause increased dilation of arterioles
What do calcium channel blockers do?
Decrease cardiac workload
What drug is used when beta blockers are contraindicated?
In asthmatics or other groups where beta blockers are contraindicated then cardiac selective calcium channel blockers can be used, such as verapamil and diltiazem.