Pharmacology of the CVS Flashcards
What is angina pectoris caused by?
Local myocardial ischaemia
o Oxygen demand exceeds supply
o Often precipitated by exertion, reversible on rest
What are the symptoms of angina pectoris?
o Crushing chest pain
Also, in jaw, shoulder, arms
o Ischaemic products (e.g. Lactate, H + ) stimulate sympathetic nociceptive
afferents
o May also be associated with shortness of breath, sweating, nausea
What increases risk of an angina attack
Increased systolic blood pressure (afterload)
Increases heart rate
Increases contractility
Increased vasoconstriction
How is stable angina induced?
Exercise-induced – predictable
Not able to meet increased O 2+ demands due to atheroma in coronary arteries
How is stable angina relieved?
Relieved by rest and medication
What is unstable angina indduced by?
Exercise-induced with minimal exertion – unpredictable
What may unstable angina indicate?
May indicate thrombosis, plaque rupture
When do the symptoms express themselves in variant angina?
Symptoms at rest
Due to what reason is there a reduced supply of O2 in variant angina?
Decreased O 2 supply due to vasospasm (un-controlled vasoconstriction, decreasing
blood flow) downstream of occlusion
What are the aims of treatment of angina?
Improve Prognosis - Prevent MI & death - Reduce plaque progression - Stabilise plaque - Prevent thrombosis Minimise symptoms - Improve quality of life
Treatment of angina(Beta-blockers) What are the effects?
- Decreases rate
- Decreases contractility
- Decreased oxygen deman
Treatment of angina(Calcium channel blockers) What are the effects?
Dilate arteriolar vessels
Treatment of angina(Nitrates) What are the effects?
Dilate arteriolar vessels
What action do beta blockers reduce?
Reduce actions of sympathetic activity (noradrenaline & adrenaline) on β1
adrenoreceptors in the heart
What do beta blockers slow down?
Slow heart rate and AV conduction
o Increase diastolic time – increase coronary artery perfusion
What force does beta blockers reduce?
Reduce force of contractility
o Reduce myocardial work and oxygen consumption
What is atenolol more selective of?
Atenolol (more β1 selective – β2 found in vasculature and airways)
Side effects of beta blockers
bronchospasm, fatigue, postural hypotension
When are beta blockers contraindicated?
- Asthma – block β2 receptor can cause constriction & bronchospasm
- Heart block where atrial-ventricular conduction is poor – may block AV node
What do calcium ion channel blockers do?
Drugs which can block VGCC’s and prevent Ca 2+ entry thus reducing the force of
contraction in ventricular myocytes
What do calcium ion channel blockers cause?
This causes vasodilation in vascular smooth muscle
What changes do calcium ion channel blockers bring about?
Reduce Ca 2+ entry into cardiac myocytes / vascular smooth muscle cells – reducing
contractility
o Direct coronary vasodilation – more coronary blood flow
o Reduce TPR / BP / afterload – heart works less hard to eject blood
o Reduce force of contraction – less O 2 consumption
What are the 3 subtypes of Ca2+ channel blockers?
Dihydropyridines (vascular) – Amlodipine, Nifedipine
Benzothiazepines (cardiac) – Verapamil
Diphenylalkyamines (both) – Diltiazem
What can blocking Ca2+ channels alter?
blocking Ca 2+ channels in the heart may alter electrical conduction and contractility
What does NO form?
Forms PKG
How does PKG formed from NO reduce smooth muscle tone?
- Myosin light chain dephosphorylation
- Increase uptake of Ca2+ by SR causing a decrease in cytoplasmic levels
- Active K+ channels causing hyperpolarisation and closing VGCC
What does coronary artery dilation increase?
Increases collateral arteriole dilation to shunt blood from areas of good perfusion
to poor perfusion (between functional end-arteries)
What does venodilation decrease?
Decrease in venous return / pre-load
What does arteriole dilation decrease?
Decrease in TPR / afterload
What 2 factors reduce myocardial O2 demand?
A decrease in preload and afterload reduces myocardial O 2 demand
What happens when NO combines with viagra?
You also have to be careful when combined with Sildenafil (Viagra) because a PDE5 inhibitor
and nitrates can produce significant hypotension
What are other commonly prescribed anti-angina drugs?
Aspirin
Clopidogrel
Nicorandil
Statins
What does aspirin inhibit and decrease?
Inhibits COX
- Decreases thromboxane A 2 and platelet aggression
What does clopidogrel inhibit?
Inhibits ADP receptor on platelets, reduces aggregation
What do both aspirin and clopidogrel reduce?
Both of these drugs reduce thrombosis and can be used together as they have entirely
different mechanisms
What do nicorandil activate and causes what??
Potassium channel activator
Causes Hyperpolarisation
When is nicorandil used?
It is used if β-blockers, Ca 2+ channel blockers are insufficient
What do statins inhibit and lower?
HMG Co-A reductase inhibitor
Lowers cholesterol levels
What is Ivabradine a selective inhibitor of?
Selective inhibitor of I f (funny current) channel in the sino-atrial node
What does Ivabradine decrease?
Decreases pacemaker potential frequency
- Decreases heart rate to reduce myocardial O 2 demand
