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MSPA- Cardiac Pharmacology > Antiarrhythmic Drugs > Flashcards

Antiarrhythmic Drugs Flashcards

1
Q

what are the phases of cardiac action potential ?

A

Phase 0: Rapid sodium influx through fast acting voltage gated Na+ channel.
Phase 01: inactivation of the voltage-gated Na+ channels along with the activation of transient outward potassium current causes a transient early repolarization.
Phase 02: Influx of L-type calcium channels matches the eflux of K+ through the rectifier K+ channels causing plateau of AP.
Phase 03: L-type calcium channel closes, but the rectfier K+ channels remain opens, this brings the membrane potential to -90 Mv causing repolarization.

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2
Q

What are the main conduction pathways from the SA node to the AV node ?

A
  • Anterior internodal pathway
  • Wenckebackh bundle or middle internodal pathway
  • Thorel’s bundle or posterior internodal pathway.
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3
Q

what is the pathway of SA nodal impulse propagation to the left atrium ?

A

Bachmann’s bundle.

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4
Q

What are the intrinsic rates of SA , AV node and Hiss-Purkinje system ?

A

SAN= 60-100
AVN= 40 -60
HPS= 20-40

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5
Q

What are the spinal levels of cardiac sympathetic nerves

A

T2 to T4.

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6
Q

What are the preventive and corrective therapies in Tachyarrhythmias?

A
  • Preventive: Medication. Catheter ablation.
  • Corrective: Resynchronization therapy (defibrillator)
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7
Q

What are the preventive and corrective therapies in Bradyarrhythmias?

A
  • Preventive: Medication.
  • Corrective: Pacemaker.
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8
Q

What are the Pharmacological aims of anti-arrhythmic therapy ?

A

Rhythm control and rate control

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9
Q

Explain the Vaughan Williams classification of anti-dysrhythmic drugs ?

A

Ia : Intermediate dissociation Na+ blocker
Ib : Fast dissociation Na+ blocker
Ic: Slow dissociation Na+ blocker
II: Beta adrenoreceptor antagonists.
III: K+ channel blockers
IV: Calcium channel blocker.

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10
Q

What is the action of Vughan Williams class 1a drugs ?

A

They work by blocking sodium channels in the open or inactivated state, thereby decreasing the rate of rise of the phase 0 depolarization, & slowing conduction velocity.
The examples are Disopyramide, Quinidine, Procainamide.

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11
Q

What is the action of Vughan Williams class II drugs ?

A

They are beta adreno-receptor antagonists such as propranolol. They inhibit phase 04 of the cardiac AP by negatively modulating pacemaker potentials.
*negative chronotropic: slower SA frequency
*negative dromotropic: slower AV conduction
*negative bathmotropic: lower excitability
leading to reduced cardiac work and metabolic needs.

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12
Q

What is the action of Vughan Williams class III drugs ?

A

They are drugs such as amiodarone and sotalol. They inhibit the opening of rectifier K+ channels at the phase III of the AP causing cardiac AP prolongation and effective refractory period of the cardiomyocytes.

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13
Q

What is the action of Vughan Williams class IV drugs ?

A

These are drugs such as delitiazam and verapamil they act on the the plateau phase ( Phase 03) of the cardiac AP. They inhibit the influx of calcium into the cardiomyocytes and reduce the force of contraction and HR.

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14
Q

What are the factors that determine the choice of anti-arrhythmic drugs ?

A

– Type of arrhythmia
– Cause of arrhythmia
– HF yes/no and type: HF with reduced ejection fraction or HF with preserved ejection fraction.
– Strategy (rhythm or rate control)
– Contra-indications

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15
Q

What are the mechanisms of arrhythmias ?

A

*enhanced automaticity: Abnormal automaticity (in SA node)
*Reentry: eg Wolf Parkinson White syndrome.
*triggered activity: after depolarization, triggers premature action potentials.

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16
Q

What is the action of Vughan Williams class 1b drugs ?

A

These are drugs that have fast association and dissociation to voltage gated sodium channels. They limit the maximum repetition rate of APs rather than changing the shape of a single AP, thus do not affect the normal heart function much. They are given IV in AMI example example lidocaine and mexiletine given PO for prevention.

17
Q

What is the action of Vughan Williams class 1c drugs ?

A

These are drugs such as Propafenone and Flecainide. They strongly block rapid sodium channels and have slow association and dissociation. Thereby slowing down the Phase 0 of the monophasic action potential and consequently the impulse conduction. They are indicated in AF patients without heart failure as they prevent ectopic beats.

18
Q

What are the indications for Beta blockers (Type II Vaughan Williams drugs) ?

A

*stable and unstable angina
*Myocardial infarction
*Heart Failure, arrhythmias

19
Q

What is the indication for Class III: Potassium channel blockers

A

To Interrupt re-entrant tachycardias.

20
Q

What are the side effects of Class III: Potassium channel blockers such as amiodorone, sotalol,

A

*Thyroid disorders and photosensitivity
* Liver damage and pulmonary alveolitis.
*Prolonged QT interval (>500 ms) can lead to torsades des pointes.

21
Q

What are the side effects of Class II drug beta blockers?

A

BBALDFISH
- Bronchoconstriction
- Bradycardia
- Arrhythmia
- Lethargy
- Disturbance in glucose metabolism
- fatigue
- Insomnia
- Sexual dysfunction
- Hypotension.

22
Q

What is Amiodarone ?

A

It is a class III: Potassium channel blockers. It is safe for patients with AF with or without HF. The side effects are Bradycardia, hepatotoxicity, thyroid dysfunction, pulmonary toxicity. Elimination takes > 6 months.

23
Q

What is Dronadrone ?

A

It is a class III: Potassium channel blockers. It is safe for patients with AF with or without HF. It has less thyrotoxicity as compared to Amiodarone.

24
Q

What is Sotalol ?

A

It is a class III: Potassium channel blockers with class II non-selective beta blocker action. Should be used with care as they can induce Torsades des pointes, renal dysfunction in HFrEF.

25
Q

What is the action of Verapamil and Dilitiazem ?

A

They are Class IV: Non-dihydropyridines Calcium channel blockers. They Shorten the plateau phase of the AP, limit the influx of Ca2+ ions and reduce force of contraction and slow down conduction in SA and AV nodes. They are indicated for the Tx of SVTs and to slow down the rate in acute and chronic AF.

26
Q

What is atropine ?

A

Atropine is the first-line therapy for symptomatic sinus bradycardia in the absence of reversible causes. It is an antimuscarinic that causes parasympathetic inhibition leading to increased HR and CO.

27
Q

What is the action of adrenaline in cardiac arrest ?

A

It is a Naturally occurring catecholamine with alpha and beta effects and is indicated to induce cardiac contraction in cardiac arrest.

28
Q

What is the indication for Isoprenline ?

A

It is a non-selective beta agonist used to reverse complete heart block.

29
Q

What is the indication for Digoxin ?

A

It is a cardiac glycoside derived from digitalis plant. It acts on the Na+/K+ ion pump that re-establishes ion concentrations and is indicated for aborting rapid AF. At high doses can precipitate VF.

30
Q

What is the indication for adenosin ?

A

Adenosine produces transient atrioventricular nodal block when injected as an intravenous bolus. Therefore, it is indicated to abort SVT.

31
Q

What is the indication for calcium chloride ?

A

It is indicated to treat VTAC due to hyperkalemia.

32
Q

What is the indication for Magnesium Chloride ?

A

VTAC and digoxin toxicity.

33
Q

What is the first line anti-arthymic Tx in HTN and HFpEF ?

A

beta blockers or ND-CCB

34
Q

What is the firstline Tx of HFrEF?

A

Beta blockers.

35
Q

What is the first line arrhythmic drug of choice in COPD and Asthma ?

A

ND-CCB

36
Q

What is the firstline Tx in pre-existing AF and VF ?

A

ablation.

37
Q

What is the second and third line anti-arthymic Tx in HTN and HFpEF ?

A

II: combine any two: Digoxin/ BB/ ND-CCB.
III: Combination of three drugs/ pacemakers/ ablation.

38
Q

What is the second and third line anti-arthymic Tx in HFrEF?

A

II: combine any two: Digoxin/ BB/ Amiodaron
III: Combination of three drugs/ pacemakers/ ablation.

39
Q

What is the second and third line anti-arthymic Tx in Asthma and COPD ?

A

II: ND-CCB and Digoxin
III: pacemakers/ ablation.

MSPA- Cardiac Pharmacology (3 decks)

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