Treatment Of Dysrhythmia

Question 1

Mention treatment of bradycardia

Answer 1

Atropine, cardiac pacing, isoprenaline (transiet)

Question 2

Mention the Vaughan Williams classification of dysrhythmic drugs with example

Answer 2

Class I: Na channels blockers (Ia: procainamide, Ib: lidocaine, Ic: propafenone)
Class II: beta-blockers
Class III: K channel blockers (amiodarone)
Class IV: Ca channel blockers (verapamil)
Non-classified: adenosine & digoxin

Question 3

Mention the effect of Na channel blockade & the effects specific to each subclass wuth resoect to strength if association

Answer 3

Dec Vmax & delay conduction. Dec phase 4 slope & dec automaticity. Inc ERP.
Ia, moderate dissociation rate, moderate conduction blockade, moderate dec of autorhythmicity
Ib, rapid dissociation from normal tissue, minimal effect
Ic, slow diss, marker effect

Question 4

Mention effect of subclasses of Na ch blockers on K channel

Answer 4

Ia, block K channels in both, thus increase APD & ERP
Ib, inc K efflux from fast fibers, thus dec ADP & ERP
Ic, no effect

Question 5

Mention effect of subclasses of Na ch blockers on AVN

Answer 5

Ia, inc ADP/ERP
Ib, no effect
Ic, inc ERP by BB action

Question 6

Mention effect of Na ch blockers on ADP/ERP

Answer 6

Ia, ^ADP/^^ERP
Ib, vvADP/vERP, as both effects affect ERP in opposite directions, while only one factor acts on ADP dec it, no effect in AVN
Ic, ADP/^ERP

Question 7

Mention effects of subclasses of Na ch blockers on ECG

Answer 7

Ia, prolong P-R, Q-T intervals & QRS
Ib, no effect on P-R, shortens QT
Ic, prolong P-R & QRS

Question 8

Mention autonomic effects of Class Ia agents & its clinical implication

Answer 8

Antimuscarinic, ganglion blockade, alpha blockade.

Paradoxical inc in AVN conduction res in ventricular tachycardia in AF (blocked by digoxin, BB, verapamil)

Question 9

Mention cardiac effects of Class Ia

Answer 9

Negative inotropic & prolonged QT sydrome

Question 10

Mention general adverse effects of Class Ia

Answer 10

Cardiotoxicity (hypotension, slow conduction, Trosade de Pointes
Thromboembolism
GIT disturbance

Question 11

GR: Class Ia may precipitate thromboemblism

Answer 11

Stagnation of blood in atria in long standing AF, RES in thrombus formation & showers of emboli on return to sinus rhythm & improvement of contractility

Question 12

Mention specific adverse effects of members of Class Ia

Answer 12

Procainamide, lupus like syndrome
Quinidine: thromobocytopenia & cinchonism
Disopyramidine: heart failure, urine retention & glaucoma

Question 13

Mention mechanism of action & uses of Lidocaine

Answer 13

Has minimal effects on normal tissue but selectively blocks inactivated sodium channels in ischemic & depolarized tissue —> marked conduction block & dec autorhythmicity
Used in V tachycardia in cardiac surgery or M. infarction & digitalis induced arrhythmia

Question 14

Mention adverse effects of lidocaine

Answer 14

1. Cardiac: it is the least cardiotoxic anti-arrhythmic drug, but still it may may precipitate cardiac arrest or worsen impared conduction
2. CNS: perioral parasthesias, dizzines, temors, convulsions.

Question 15

Mention therapeutic uses & adverse effects of propafenone

Answer 15

U: SV & V arrhythmias
AE: arrhthymias, AV block, heart failure, taste disturbances, constipation, bronchospasm, dizziness, blurred vision.

Question 16

Describe mechanism of action of BB in treatment of arrhythmia

Answer 16

Des SAN & AVN activity & slope of phase 4

Question 17

Mention therapeutic uses & adverse effects of BB

Answer 17

U:arrhythmias due to symp overactivity, arrhythmias following MI, IV esmolol for Termination (not control) of PSVT
AE: aggravate heart failure, heart block, aggravate bronchial asthma

Question 18

Describe mechanism of action of Class III agents (amiodarone)

Answer 18

K channel blockade: delays repolarization, blocks reentry
Na channel blockade: suppress ectopic foci, slow conduction
CCB: coronary & peripheral VD, dec sinus rate & AVN conduction

Question 19

Mention therapeutic uses of Class III

Answer 19

Broad-Spectrum, ventricular & SV arrhythmias including WPWS.

Question 20

GR: Amiodarone is given as a LD followed by maintainance dose.

Answer 20

Because full effect is reached after a lag period of 1-3 weeks as it has long t half.

Question 21

Mention two most prominent drug interactions of amiodarone

Answer 21

Displaces digoxin from PP

Inhibits warfarin metabolism

Question 22

Mention adverse effects of Class III agents

Answer 22

1. Cardiac: bradycardia, heart block, hypotension
2. Corneal microdeposits
3. Thyroid dysfunction
4. Inc liver enzymes
5. Pulmonary inflitrates & fibrosis
6. Peripheral neuropathy & myopathy
7. Photosensitivity

Question 23

Mention a drugs related to amiodarone, its advantage & uses & adverse effects

Answer 23

Dronedarone, devoid of iodine
Similar to amiodarone not used in NYHA class iv HF
Inc Torsade de Pointes

Question 24

Describe pharmacodynamic action of class vi agents and its uses

Answer 24

Block Ca++ current in slow fibers
Dec SAN & AVN activity
Dec phase 4 slope
U: Supraventricular arrhythmias: AF & Af, termination of PSVT

Question 25

Side effects of class vi agents

Answer 25

1. Paradoxical acceleration of conduction in WPW syndrome leading due to blockade of AV conduction
2. Aggravate HF
3. Adverse effects of CCBs

Question 26

Describe the pharmacodynamic action of adenosine & uses

Answer 26

Binds A1 receptors, opens K+ channel, hyperpolarization, dec Ca++ influx
Dec SAN rate & AVN conduction & inc ERP
U: Termination of PSVT

Question 27

Mention side effects of adenosine

Answer 27

1. Chest pain & dyspnea (A1 action, CI asthma)
2. Headache and flushing (A2 action, VD)
3. Sinus bradychardia, arrest or AV block (CI AV block)

Question 28

Write a note on broad therapeutic classification of antiarrhythmic drugs

Answer 28

For V arrhythmia, lidocaine, phenytoin, mexillitine
For SV arrhythmia, verapimil, adenosine, digoxin
For V & SV, caused by symp overactivity: BB
Broad-spectrum: class Ia & Ic & III [WPW syndrome]

Question 29

Uses of MgSO4

Answer 29

Digitalis induced arrhythmia associted with hypomagnesia

Torsades de Pointes

Question 30

AF & Af treatment

Answer 30

DC in hemodynamically unstable patients
In stable patient:
Pharmacological cardioversion:
Procainamide (+digoxin, BB or verapamil to block AVN)
Maintenance of rhythm after cardioversion
Propafenone (+verapimil), Amiodarone, sotalol
Ventricular rate control
BB, verapamil/diltiazem , digoxin
Anticoagulants: to avoid thromboembolism