9 Drugs of the CVS Flashcards
What is an arrhythmia?
Name 3 kinds of arrythmia
An abnormality of heart rate or rhythm
Atrial fibrillation, bradycardia, tachycardia, atrial flutter, ventricular fibrillation
List 2 causes of arrythmias
Ectopic pacemaker activity- damaged area of tissue fires action potentials faster than the SAN
Afterdepolarisations- abnormal depolarisations after the action potential
When is a delayed after-depolarisation more likely to happen?
If the intracellular Ca2+ concentration is high
How can an early afterdepolarisation be seen on an ECG?
Long QT interval.
What is a re-entry loop?
If there is a blockage in a neurone, the action potential takes a longer way around to depolarise the tissues. It can end up depolarising the wrong way.
What do re-entry loops cause?
Conduction delays
Accessory pathways
Atrial fibrillation
What is a Class I drug? Give an example
Drugs which block voltage-dependent Na+ channels
Lidocaine
What is a Class II drug? Give an example
B-adrenoreceptor blocker
Propranolol
How do Class II drugs decrease heart rate?
Increase the length of the funny current.
What is a Class III drug? Give an example
Drugs which block K+ channels
Sotalol
How do Class III drugs work?
Action potential is prolonged by blocking the K+ channels. The absolute refractory period is lengthened preventing many action potentials in a short amount of time
What is a Class IV drug? Give an example
Drugs which block Ca2+ channels
Verapamil
How do Class IV drugs work?
They decrease the slope of the pacemaker action potential at the SA node. The force of contraction is reduced. There is also some peripheral vasodilation.
How does Adenosine work?
Acts on A1 receptors in the AV node. It enhances K+ conductance and hyperpolarises cells of the conducting tissue.
List 4 ways drugs can effect the CVS?
Alter the rate and rhythm of the heart
Alter the force of contraction
Alter peripheral resistance and blood flow
Alter blood volume
What is heart failure?
Reduced heart contraction
Reduced cardiac output- does not meet body’s needs
What do cardiac glycosides do? Give an example
Increase myocardial contractility
Digoxin
How do cardiac glycosides work?
Block Na/K ATPase. Build up of Na+ in the cell. Na-Ca-exchanger decreases in activity and so Ca2+ levels increase. More Ca2+ is stored in the S/ER. On depolarisation, more Ca2+ can be released from intracellular stores causing a larger contraction.
What do B-adrenoreceptor agonists do? Give an example
Increase myocardial contractility
Dobutamine
What is an ACE-inhibitor? How do they work?
Drugs which reduce the workload of the heart.
Angiotensin I cannot be converted to angiotensin II. Angiotensin II is a vasoconstrictor that works in the kidneys. Less water is reabsorbed so the blood pressure and blood volume decreases.
What is angina?
Chest pain usually with exertion.
Name drug types that can be used to treat angina
B-adrenoreceptor blockers
Ca2+ channel antagonists
Organic nitrates
How do organic nitrates work in the CVS?
React with thiols (-SH) in vascular smooth muscle to release (NO2)-. It is then reduced to NO which is a powerful vasodilator.
Guanylate cyclase is activated. Increased cGMP. [Ca2+]i lowered. Muscle relaxes.
Where can organic nitrates NOT dilate? Where do they dilate instead to increase blood flow to an ischaemic area?
Arterioles
Collateral arterioles
What do antithrombotic drugs do?
Reduce the risk of thrombus formation
Name 2 types of antithrombotic drugs. Give an example for both
Anticoagulants- heparin, warfarin
Antiplatelet drugs- aspirin
Name 2 drug types used to treat hypertension
ACE-inhibitors
B-blockers
