Drug treatments for ischaemic heart disease Flashcards
(32 cards)
Define ischaemic heart disease
Narrowing of the lumen of the coronary arteries resulting in an imbalance between the supply of oxygen (and other essential nutrients) and the myocardial demand resulting in myocardial ischaemia and chest pain
What is the main problem of ischaemic heart disease?
The imbalance of oxygen supply and demand
Name an Endothelium-derived relaxing factor
Nitric oxide
Define stable angina
A predictable pattern of pain during exercise that is relieved by rest
What is the function of the drug treatment used in stable angina?
Drug treatment designed to decrease work done by the heart and/or increase blood supply and treat risk factors.
Name the drug treatment used in stable angina
Nitrates
What is the main effect of nitrates?
Decrease preload by dilating the veins
They will however dilate some coronary arteries and regulated some blood supply to the heart
Have a minor effect on arterioles to increase afterload
What are the side effects of nitrates?
Postural hypotension
Reflex tachycardia
Headache
Dizziness
What is reflex tachycardia and what can be used to prevent it?
Reflex tachycardia due to activation of sympathetic nervous system. If treatment causes reflex tachycardia, then should look to block effects of sympathetic nervous system using a beta blocker, such as bisopolol.
Why is reflex tachycardia an issue after giving someone nitrates?
The purpose of the nitrate is for the ischemic heart disease
Do not want to increase heart rate/ blood pressure
Which receptor do beta blockers inhibit?
Beta 1 receptors
What do beta blockers do?
Reduce frequency Reduce force of contraction Reduce cardiac output Also inhibit renin release from kidney Also inhibit RAAS Reduce the calcium coming from L type channels
State the side effects of beta blockers
Bronchoconstriction
Fatigue
Contraindicated in patients with peripheral vascular disease
What do CA2+ channel antagonists do?
Decrease frequency
Decrease force of contraction
Increased dilation of arterioles
These all lead to a decrease in cardiac workload
Describe how calcium channel blockers reduce force of contraction and reduce heart rate
CCBs can reduce heart beat by blocking L-type channels in the SA and AV-nodes. This will slow the rate of depolarisation and therefore reduce the rate of action potential generation. They also decrease the force of contraction of the ventricles by reducing calcium entry through L-type channels.
What does Ivabradine do?
Blocks the pacemaker current (Ih/f) in the nodal tissue of the heart.
What are the side effects of ivabradine?
Luminous phenomena (Ih) in retina
Blurred vision
dizziness
Describe how ivabradine causes a decrease in cardiac rate?
Ivabradine will reduce Na+ entry through If channels and so slow the rate of depolarisation of the SA node cells and reduce firing frequency and therefore heart rate. It will not alter the force of contraction of the heart
Name some alternatives to nitrates, beta blockers and calcium channel blockers for ischemic heart disease/angina
Long acting nitrates (isosorbide mononitrate) - Decrease preload
Nicorandil - Decreases afterload- Increases NO causing venous dilatation, opens K+ ATP channels in smooth muscle causing hyperpolarization of the muscle.
Ranolazine - Reduces work done by the heart
Trimetazidine - rebalances energy metabolism in the cell- heart muscle cells use glucose instead of fatty acids
Describe the action of treatment to reduce hypercholesterolaemia 2o Prevention
Drugs designed to either inhibit uptake from GI tract or reduce production in liver.
Frontline treatment are the STATINS e.g. simvastatin, atorvastatin
Describe the action of statins
Statins decrease the production of cholesterol in the liver by inhibiting the HMG CoA enzyme. This stimulates the liver cells to express LDL receptors and allows the liver cells to scavenge LDL cholesterol from the plasma. This reduces plasma LDL cholesterol levels.
List some secondary prevention of hypercholesterolaemia and its effects
Aspirin - Antiplatelet agents (aspirin/clopidpgrel)
ACE inhibitors (e.g. ramipril) - Decrease the workload on the heart
ARBs (losartan) - Decrease the workload on the heart
List the treatment for unstable angina, NSTEMI and STEMI
As for stable angina + antiplatelet
Aspirin; aspirin + clopidogrel (prasugrel, ticagrelor)
Describe the mechanism of action of some key antiplatelet agents
Platelet activation occurs when the endothelial cells become damaged. This releases ADP which acts on P2Y12 receptors to stimulate the platelet to express GPIIb/IIIa receptors. Fibrinogen binds to these receptors to cross link different platelets. Activation of COX also helps platelet activation through the production of Thromboxane A2. Aspirin inhibits COX irreversibly.. Clopidogrel and Prasugrel are ADP antagonists and block P2Y12 receptors.
