Session 7 - Cardiac Arrhythmias And CVS Drugs

Question 1

What is ectopic pacemaker activity?

Answer 1

Damaged area of myocardium becomes depolarized and spontaneously active and dominates over SA node

Question 2

What are afterdepolarisations?

Answer 2

Abnormal depolarisations following the action potential

Question 3

What is sick sinus syndrome?

Answer 3

Intrinsic SA node dysfunction

Question 4

When are early after depolarisations more likely to happen?

Answer 4

If AP is prolonged // if longer QT interval

Question 5

When are delayed after depolarisations more like to happen?

Answer 5

High intracellular Ca2+

Question 6

What is the re entrant mechanism for generating arrythmias?

Answer 6

When there is incomplete conduction damage, excitation can take a long route to spread the wrong way through damaged area, setting up a circus of excitation

Question 7

How does re entrant circuits lead to atrial fibrillation?

Answer 7

Multiple re entrant circuits in atria causes many atrial fibrillation impulses and chaotic signals passes through AV node, causing rapid ventricular impulses

Question 8

How does AV nodal re entry occur?

Answer 8

Fast and slow pathways in AV node creates a re entry loop

Question 9

What is ventricular pre excitation?

Answer 9

Accessory pathway between atria and ventricles creates re entry loop

Question 10

What are 4 basic classes of anti arrhythmic drugs?

Answer 10

Na+ channel blockers
Beta adrenoceptor antagonist
K+ channel blockers
Ca2+ channel blockers

Question 11

What is an example of a voltage dependent-Na+ channel blocker?

Answer 11

Lidocaine

Question 12

How does Na+ channel blocker work?

Answer 12

Only blocks in open or inactive state, hence preferentially blocks damaged depolarized tissue and not normal tissue as it dissociates rapidly

Question 13

What is the effect of lidocaine?

Answer 13

Blocks Na+ channels, slows upstroke, shortens action potential and slows conduction velocity

Question 14

What are 2 examples of beta blockers?

Answer 14

Propranolol

Atenolol

Question 15

How do beta blockers work?

Answer 15

Block sympathetic action at beta 1 adrenoceptors in heart, decreases slope of pace,alter potential in sinoatrial node and slows conduction at AV anode

Question 16

What can beta blockers used to prevent?

Answer 16

Supraventricular tachycardia as it slows conduction in AVnode and can slow ventricular rate in patients with atria fibrillation

Question 17

What can beta blockers be used following?

Answer 17

MI as it often causes increased sympathetic activity, so beta blockers can prevent ventricular arrythmias

Question 18

What can K+ channel blockers do?

Answer 18

Prolong action potential and lengthen absolute refractory period

Question 19

What is an example of K+ channel blocker?

Answer 19

Amiodarone

Question 20

What can amiodarone be used for?

Answer 20

Treat tachycardia associated with Wolff-Parkinson-White syndrome

Question 21

What are 2 examples of non dihydropyridine Ca2+ channel blockers?

Answer 21

Verapamil

Diltiazem

Question 22

What do non-dihydropyridine Ca2+ channel blockers do?

Answer 22

Decrease slope of action potential at SA node, decrease AV nodal conduction, hence slowing heart rate and decrease force of contraction

Question 23

What does adenosine do?

Answer 23

Act on A1 receptors at AV node but has very short half-life, enhances K+ conductance hence hyper Polaris into cells of conducting tissue

Question 24

What can adenosine be used for?

Answer 24

Termination re entrant supraventricular tachycardia

Question 25

What are 2 conditions that ACE inhibitors can be used to treat?

Answer 25

Hypertension | Heart failure

Question 26

What is an example of ACE inhibitors?

Answer 26

Perindopril

Question 27

What is the mechanism of action of ACEi?

Answer 27

Angiotensin converting enzyme inhibitor, prevents conversion of angiotensin I to angiotensin II

Question 28

What does angiotensin II do?

Answer 28

Acts on kidney to increase Na+ and water reabsorption and causes vasoconstriction

Question 29

What is a side effect of ACEi?

Answer 29

Dry cough

Question 30

How does ACEi reduce blood pressure?

Answer 30

It is a vasoconstrictor so it decreases vasomotor tone, hence decreasing after load

Question 31

How does ACEi reduce blood volume?

Answer 31

Reduce fluid retention and preload

Question 32

When are angiotensin II receptor blockers used?

Answer 32

If patients cannot tolerate ACEi

Question 33

What is an example of a ARB?

Answer 33

Losartan

Question 34

What are 2 conditions that diuretics treat?

Answer 34

Heart failure | Hypertension

Question 35

What are loop diuretics used for?

Answer 35

Congestive heart failure

Question 36

What are 2 examples of diuretics?

Answer 36

Furosemide | Thiazide diuretics

Question 37

What do dihydropyridine Ca2+ channel blockers do?

Answer 37

Act on vascular smooth muscle, decreases peripheral resistance, decreases arterial BP and reduces afterload

Question 38

What are 3 examples of dihydropyridine Ca2+ channel blockers?

Answer 38

Amlodipine Nicardipine Nifedipine

Question 39

What do positive inotropes do?

Answer 39

Increase contractility and thus cardiac output

Question 40

What are 2 types of positive inotropes?

Answer 40

Cardiac glycosides | Beta-adrenergic agonists

Question 41

What is an example of cardiac glycosides?

Answer 41

Digoxin

Question 42

What is an example of a beta-adrenergic agonist?

Answer 42

Dobutamine

Question 43

What is cardiac glycosides primary mode of action?

Answer 43

Block Na K ATPase, leads to rise in intracellular Na+, so NCX doesn’t work as well so intracellular Ca2+ increases and more is stored in SR, hence increasing force of contraction

Question 44

How does cardiac glycosides affect heart rate?

Answer 44

Increased vagal activity, slowing AV conduction, slowing heart rate

Question 45

What is an example of beta adrenoceptor agonist?

Answer 45

Dobutamine

Question 46

What do beat adrenoceptor agonists do?

Answer 46

Stimulate beta 1 receptors on SA AV node and ventricular myocytes

Question 47

What are 2 uses of beta adrenoceptor agonists?

Answer 47

Cardiogenic shock | Acute but reversible heart failure

Question 48

Are cardiac glycosides good treatment of heart failure?

Answer 48

It will relieve symptoms by making heart contract harder but no long term benefit, it’s better to reduce workload

Question 49

How does angina occur?

Answer 49

When O2 supply doesn’t meet its demand, causing ischaemia and hence chest pain

Question 50

How does nitrates work to treat angina?

Answer 50

Reaction of organic nitrates with thiols in vascular smooth muscle causes NO2- to be released and reduced to NO which is a powerful vasodilator particularly effective on veins

Question 51

What are 2 examples of organic nitrates and the difference between them?

Answer 51

GTN spray short acting | Isosorbide dinitrate longer acting

Question 52

How does NO cause vasodilation?

Answer 52

Activates guanylate cyclase, increase cGMP, lowers intracellular Ca2+ and hence relaxation of vascular smooth muscle

Question 53

Why do organic nitrates preferentially act on veins?

Answer 53

Less endogenous nitric oxide in veins

Question 54

What is the primary action of nitrates that help alleviate symptoms?

Answer 54

Venodilation reduces venous pressure, return of blood to heart, lowers preload, reducing workload of heart, heart fills less, reducing force of contraction, reducing O2 demand

Question 55

What is the secondary action of organic nitrates that help alleviate symptoms?

Answer 55

Dilate coronary collateral arteries improved O2 delivery to ischaemic myocardium

Question 56

What are 2 types of anti thrombotic drugs?

Answer 56

Anticoagulants | Antiplatelet

Question 57

What are 4 types of anticoagulants?

Answer 57

Heparin Fractionated heparin Warfarin Direct acting oral thrombin inhibitors

Question 58

How does heparin work as a anticoagulant?

Answer 58

Inhibits thrombin, used acutely for short term action

Question 59

What do antiplatelet drugs do?

Answer 59

Prevent platelet rich arterial thrombus formation

Question 60

What are 2 examples of antiplatelet drugs?

Answer 60

Aspirin | Clopidogrel