L13 - Antiarrythmics

Question 1

Early after depolarisations occur more often in extended action potentials, which disease are they particularly associated with

Answer 1

Long QT syndromes

Question 2

What are the four basic classes of antiarrythmic drugs, give an example of each

Answer 2

Nav channel blockers - lidocaine
Beta blockers - propanolol
K+ channel blockers - amiodarone
Calcium channel blockers (non-dihydropyridine)- diltiazem

Question 3

Afterdepolarisations are associated with damaged depolarised tissue that can cause re-entrant loops. Lidocaine preferentially blocks damaged depolarised tissue during depolarisation but dissociates in time for next AP thus preventing arrythmias - T/F?

Answer 3

T

Question 4

When would lidocaine be used?

Answer 4

Following MI only if patient shows signs of ventricular tachycardia

Question 5

How do B blockers work to prevent arrythmias?

Answer 5

Block B1 receptors thus slowing conduction through av node and thus slows HR

Question 6

Beta blockers are useful in preventing supraventricular tachycardia. They are useful for patients with AF to slow HR and following MI as MI’s are associated with increased SYM activity. What is a bonus of them too?

Answer 6

They reduce the myocardiums oxygen demand by slowing hr

Question 7

K+ channel blockers work by lengthening the refractory period through blocking k channels, why in theory are they actually often pro-arrythmic?

Answer 7

Extended QT interval is associated with early after depolarisations -> arrythmias

Question 8

Why is amiodarone not pro-arrhythmic?

Answer 8

Because it blocks other channels than just k ones

Question 9

What is first line treatment for suppressing ventricular arrythmias post MI and wolf-Parkinson white syndrome?

Answer 9

Amiodarone

Question 10

CCb’s have a three pronged effect, name each

Answer 10

1) decrease slope of action potential at sa node
2) decrease AV nodal conduction
3) decrease force of contraction

Question 11

Adenosine is produced endogenously but can also be administered IV as an anti-arrhythmic agent. What is it used for specifically?

Answer 11

Terminating supraventricular tachycardia

Question 12

Give an example of something which ACEi’s would be used for

Answer 12

Hypertension

Heart failure

Question 13

How do ACEi’s treat heart failure?

Answer 13

Decrease blood pressure and thus the afterload on the heart

Decrease fluid retention and thus the preload on the heart

Question 14

Ace inhibitors can cause a dry cough in users, why is this?

Answer 14

Also enhances production of bradykinin which causes a dry cough

Question 15

Angiotensin receptor blockers are used for heart failure and hypertension in patients who can’t tolerate ace inhibitors, give an example of one

Answer 15

Losartan

Question 16

What drugs are useful in treating hypertension and heart failure?

Answer 16

Diuretics
ARB’s
ACEI’s

Question 17

Are dihydropiridine calcium channel blockers effective in preventing arrythmias?

Answer 17

No but they act on smooth muscle and are useful in:

Hypertension/angina/superventricular tachycardias they work by reducing afterload on heart

Question 18

Digoxin is a cardiac glycoside (positive inotrope), they are useful in treating symptoms of heart failure but not affecting outcome, what is their primary mode of action?

Answer 18

Block Na/k atpase -> rise in IC Na -> loss of gradient to extrude ca -> accumulation -> increases in contractility

Question 19

When are cardiac glycosides useful and why?

Answer 19

Heart failure with AF - they also slow the HR

Question 20

Dobutamine is a B1 selective agonist, it stimulates receptors and sa and av node and ventricular myocytes, suggest a use

Answer 20

Cardiogenic shock

Acute heart failure (if reversible)

Question 21

Nitrates are useful in treating Angina, how do they work?

Answer 21

They are reduced endogenously to nitric oxide which is a vasodilator (mainly a venodilator)

Question 22

Specifically how does nitric oxide cause vasodilation?

Answer 22

Converts GTP to cGMP which activates PKG, which decreases IC calcium -> relaxation of smooth muscle

Question 23

NO from nitrates acts preferentially on the venous system and thus reduces preload on the heart (lowers oxygen demand), it also acts on coronary collateral arteries to improve o2 delivery to the myocardium, what does it not work on?

Answer 23

arterioles

Question 24

Give three drugs used for treatment of angina

Answer 24

Organic nitrates
B blockers
Ca channel blockers (non-dihydropyridine)

Question 25

Give two of the theee heart conditions that carry an increased risk of thrombus formation

Answer 25

AF
acute MI
Mechanical prosthetic valves

Question 26

What preventative drugs are used to prevent thrombosis - antithrombotics

Answer 26

Anticoagulants e.g. heparin or warfarin

Antiplatelets e.g. aspirin/clopidogrel