Arrythmias And Drugs

Question 1

What is an Arrhythmia/ Dysrhythmia

Answer 1

An abnormal heart rate/ rhythm

Question 2

Identify 4 causes of tachycardia

Answer 2

Conduction delay-> A re-entry loop

Ectopic pacemaker activity from a damaged area of myocardium

Afterdepolarisations after the action potential (Triggered activity)

Atrial fibrillation/ flutter (Flutter- Regular tachycardia of atria, which also beat more frequently than ventricles)

Question 3

Identify 2 causes of bradycardia

Answer 3

Conduction block (Problem at AV node or His bundle)

Sinus bradycardia

Question 4

When are Delayed and Early after-depolarisations more likely to happen

Answer 4

Delayed- High intracellular Ca

Early- If Action Potential is prolonged (Longer QT)

Question 5

What are the 4 classes of Anti-Arrythmitic drugs

Answer 5

Class 1: Na+ channel blockers

Class 2: B-adrenoceptor antagonists

Class 3: K+ channel blockers

Class 4: Ca2+ channel blockers

Question 6

How do Na channel blockers work

Why is there little effect in normal tissue
Which tissue do they preferentially work in

Answer 6

Block Na+ channels if in OPEN or INACTIVE state

Little effect in normal cardiac tissue, as it blocks during depolarisation bu dissociates rapidly in time for next AP

Preferentially blocks damaged depolarised tissue (As more channels open)

Question 7

How do Beta-adrenoceptor antagonists work

How do they affect the slope of pacemaker potential at SA Node

How do they affect conduction at AV Node

Answer 7

Act at Beta-1 adrenoceptors in heart to block sympathetic action

Decreased slope of pacemaker potential
Slowed conduction at AV node

Question 8

Give 2 reasons Beta-blockers are used after an MI

Answer 8

1. Counter increased sympathetic activity (due to MI)

2. Reduce O2 demand, so reduced Myoarcidial Ischaemia

Question 9

Name 1 Na channel blocker and 2 Beta-adrenoceptor antagonists

Answer 9

Na channe blocker: Lidocaine

B-Adrenoceptor Antagonists: Propranolol, Atenolol (Beta blockers)

Question 10

How do K+ channel blockers work
Why are they not normally used

Name 1 exception and say when it is used

Answer 10

Prolong action potential, lengthening the Absolute Refractory Period

They prolong the QT interval, so can cause an arrhythmia

Amiodarone, used to treat tachycardia

Question 11

How do Ca channel blockers work in 4 ways

Answer 11

• Decrease slope of AP at SA node
• Decrease AV Node conduction
• Decreased Inotropy
• Vasodilation

Question 12

How do Non-dihydropyridine Ca channel blockers differ from dihydropyridine

Answer 12

Non-dihydropyridine: Don’t prevent arrhythmias, but act on vascular smooth ,uncle

Question 13

How does IV adenosine work in 2 ways

What is it used to treat
What is one con

Answer 13

Acts on A1 receptors at AV node and enhances K+ conductance.

Also, acts on Gi proteins-> Less cAMP-> Reduced ‘Funny current’

Terminating re-entrant Supraventricular Tachycardia
Short half life

Question 14

What are ACE Inhibitors used to treat

How in 2 ways?

Answer 14

To treat Hypertension and Heart failure

Vasodilation-> Reduced Afterload of heart

Decreased fluid retention-> Reduced Preload of heart as lower blood volume

(Reduced workload of heart)

Question 15

What is a side effect of using ACE inhibitors to treat Hypertension and Heart Failure

What drugs can be used instead

Answer 15

Dry cough due to Bradykinin buildup

Can use Angiotensin II receptor blockers instead

Question 16

What 2 things can Diuretics be used to treat

Answer 16

Heart failure and hypertension

Question 17

What kind of drugs are Cardiac Glycosides and B-adrenoceptor agonists

Name 1 of each

Answer 17

Positive inotropes

Cardiac Glycoside: Digoxin
B agonist: Dobutamine

Question 18

What can Cardiac Glycosides be used to treat

How do they work primarily in 3 steps

What is the second way they work

Answer 18

Heart failure accompanied by Afib

1. Inhibit the Na-K pump, so Intracellular Na+ Increases
2. Decreased NCX activity, so Ca2+ builds up SR
3. Positive Inotropy

Increasing vagal input to heart, reducing HR

Question 19

What are 2 used for Beta adrenoceptor agonists

Why are cardiac glycosides not usually used

Answer 19

Treating cardiogenic shock
Treating Acute but reversible heart failure

They make heart contract harder, increasing the workload, so worse in long-run

Question 20

What is Angina

What drugs can be used to treat this, how do they affect work load/ blood supply to heart

Answer 20

Insufficient supply of O2 to Myocytes, without death of the cells

Reduced workload: Organic nitrates, B antagonists, Ca blockers
Increased blood supply: Ca blockers, Organic nitrates

Question 21

How do Organic Nitrates work in 3 steps

Answer 21

React with -SH groups in vascular smooth muscle-> NO2- released

NO2- reduced to NO, released from endothelial cells

NO causes vasodilation

Question 22

Rank the effectiveness of Organic Nitrates on veins, arteries and arterioles

Answer 22

Veins- Most effective
Arteries
Arterioles- Least effective

Question 23

What is the Primary Action of Organic Nitrates

What is the Secondary Action

Answer 23

Venodilation lowers preload, so heart fills less and contracts less, so less O2 needed

Dilation of coronary arteries= Improved O2 delivery

Question 24

Name 3 conditions that have increased risk of thrombus formation

Name 2 drug types that can be given to treat

Answer 24

Atrial fibrillation
Acute MI
Valve disease

Anticoagulants
Anti-platelet drugs