Antiarrhythmic Drugs (Konorev) Flashcards by Staci Thomas

Q

Cardiac _______ _______ is a sequence of ion fluxes through specific ion channels across the cell membrane (sarcolemma).

A

Action Potential

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Q

What components of cardiac muscle are involved in fast action potential?

A

- Ventricular contractile cardiomyocytes
- Atrial cardiomyocytes
- Purkinje fibers

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Q

What components of cardiac muscle are involved in slow (pacemaker) action potential?

A

- SA node cells

- - AV node cells

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Q

What fast action potential phase is being described?

– Voltage-dependent fast Na+ channels open as a result of depolarization; Na+ enters the cells down its electrochemical gradient.

A

Phase 0

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Q

What fast action potential phase is being described?

– K+ exits cells down its gradient, while fast Na+ channels close, resulting in some depolarization.

A

Phase 1

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Q

What fast action potential phase is being described?

– Plateau phase results from K+ exiting cells offset by and Ca2+ entering through slow voltage-dependent Ca2+ channels.

A

Phase 2

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Q

What fast action potential phase is being described?

– Ca2+ channels close and K+ begins to exit more rapidly resulting in repolarization.

A

Phase 3

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Q

What fast action potential phase is being described?

– Resting membrane potential is gradually restored by Na+/K+ ATPase and the Na+/Ca2+ exchanger.

A

Phase 4

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Q

What pacemaker action potential phase is being described?

– Slow spontaneous depolarization

A

Phase 4

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Q

For phase 4 of pacemaker action potential, there is poorly selective ionic influx of Na+ and K+, known as pacemaker current called ________ ________. This is activated by hyperpolarization.

A

Funny Current (If)

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Q

For phase 4 of pacemaker action potential, there is also slow Ca2+ influx via _______ channels.

A

T-type (transient)

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Q

What pacemaker action potential phase is being described?

– Upstroke of action potential due to Ca2+ influx through the relatively slow L-type (long-acting) Ca2+ channels.

A

Phase 0

***Remember, this occurs due to calcium and NOT sodium like in fast AP!

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Q

What pacemaker action potential phase is being described?

– Repolarization due to inactivation of calcium channels with increased K+ efflux.

A

Phase 3

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Q

Class 1 antiarrhythmic drugs are ________ channel-blockers.

A

Sodium

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Q

What are the Class 1A drugs?

A

- Quinidine
- Procainamide
- Disopyramide

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Q

What are the Class 1B drugs?

A

- Lidocaine

- - Mexiletine

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Q

What are the Class 1C drugs?

A

- Flecainide

- - Propafenone

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Q

Class 2 anti arrhythmic drugs are…

A

Beta blockers

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Q

What are the Class 2 drugs?

A

- Esmolol

- - Propranolol

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Q

Class 3 anti arrhythmic drugs are ________ channel-blocking drugs.

A

Potassium

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Q

What are the Class 3 drugs?

A

- Amiodarone
- Sotalol
- Dofetilide
- Ibutilide

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Q

Class 4 anti arrhythmic drugs are cardioactive ________ channel blockers.

A

Calcium

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Q

What are the Class 4 drugs?

A

- Verapamil

- - Diltiazem

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Q

This is an anti arrhythmic drug that is not in one particular class because it has characteristics of many of them.

A

Adenosine

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When a sodium channel is activated, Na+ current occurs down ________ and ________ gradients.

Electric | Concentration

Class 1A drugs block sodium channels, which slow impulse conduction and reduce automatism of ectopic pacemakers. Explain what this looks like on ECG.

Prolong QRS interval of ECG

Class 1A drugs reduce the slope of which phase?

Phase 0

Class 1A drugs can also block ________ channels, which prolongs the action potential duration.

Potassium

Since Class 1A drugs can also block potassium channels and thus prolong the action potential duration, what does this look like on an ECG?

Prolongs QT interval of ECG

This Class 1A drug, in addition to sodium channel block, can directly depress the activities of SA and AV nodes and possesses antimuscarinic activity. Also reduces peripheral vascular resistance and may cause hypotension.

Procainamide

This Class 1A drug is used infrequently due to its frequent dosing and common occurrence of lupus-related side effects.

Procainamide

This Class 1A drug has the following adverse effects: -- QT interval prolongation and induction of torsade de pointes arrhythmias and syncope -- Lupus erythematous syndrome -- Hypotension

Procainamide

This Class 1A drug is a natural alkaloid from Cinchona bark. Rarely used due to its cardiac and extra cardiac adverse effects and availability of better drugs.

Quinidine

This Class 1A drug, in addition to sodium channel block, affords antimuscarinic effect on the heart and may enhance AV conductance. This may cause hypotension and tachycardia.

Quinidine

This Class 1A drug has the following adverse effects: -- QT interval prolongation and induction of torsade de pointes arrhythmia and syncope -- GI side effects -- Cinchonism (tinnitus, hearing loss, confusion, delirium, psychosis, vision issues) -- Thrombocytopenia, hepatitis, fever

Quinidine

This Class 1A drug, in addition to the sodium channel block, affords strong antimuscarinic effect on the heart. It is used clinically for recurrent ventricular arrhythmias.

Disopyramide

This Class 1A drug has the following adverse effects: -- QT interval prolongation and induction of torsade de pointes arrhythmia and syncope -- Negative inotropic effect (may precipitate heart failure) -- Atropine-like symptoms (tachycardia, urinary retention, dry mouth, blurred vision, constipation, exacerbation of glaucoma)

Disopyramide

Class 1B drugs also bind to inactivated sodium channels. What is the difference in conduction that they cause for normal vs. depolarized (damaged) tissue?

Normal tissue = no effect on conduction Depolarized (damaged) tissue = slows conduction (decreased slope for phase 0)

This subtype of Class 1 drugs may shorten the action potential, and are more specific for action on sodium channels. They do not block potassium channels, do not prolong action potential or QT duration on ECG.

Class 1B drugs

This Class 1B drug has an extensive first-pass metabolism and is used only by the intravenous route.

Lidocaine

What is the clinical use for Lidocaine (in terms of arrhythmia)?

Termination of ventricular tachycardia in the setting of acute myocardial ischemia

This Class 1B drug is the least toxic of all Class 1 drugs, proarrhythmic effects are uncommon.

Lidocaine

This Class 1B drug is the orally active congener of Lidocaine. It has electrophysiological and antiarrhythmic effects similar to Lidocaine as well.

Mexiletine

What is the clinical use for Mexiletine?

-- Ventricular arrhythmias -- Relieve chronic pain, especially due to diabetic neuropathy and nerve injury

This Class 1B drug has the following adverse effects: - - Tremor - - Blurred vision - - Nausea - - Lethargy

Mexiletine

This subtype of Class 1 drugs will block sodium channels, thus slowing impulse conduction. They also block certain potassium channels.

Class 1C drugs

This subtype of Class 1 drugs does NOT prolong action potential duration and QT interval duration of the ECG, but it does prolong the QRS interval duration.

Class 1C drugs ***Prolonged QRS means decreased slope of Phase 0, resulting in slower conduction.

What is the clinical use for Flecainide, a Class 1C drug?

-- In patients with otherwise normal hearts who have supraventricular arrhythmias -- Life-threatening refractory ventricular arrhythmias

Flecainide may cause severe exacerbation of ventricular arrhythmias when administered to what type of patients?

-- Patients with preexisting ventricular tachyarrhythmias -- Patients with previous MI -- Patients with ventricular ectopic rhythms

Propafenone has similar sodium channel blocking kinetics as Flecainide. It also possesses weak _________ activity.

Beta-blocking

What is the clinical use for Propafenone?

Supraventricular arrhythmias in patients without structural disease

T/F. Propafenone has similar side effects to Flecainide.

True. It also can exacerbate ventricular arrhythmias.

Briefly explain how sympathetics usually work on cardiac pacemaker cells.

Beta1-adrenergic receptor is a GPCR, which will activate cAMP then PKA. PKA will go on to activate the funny current (If) and the T- and L-type Ca2+ channels. This results in increased HR and contractility. ***Thus, Beta-blockers obviously block the receptor and prevent this from happening.

Sympathetics cause an (INCREASED/DECREASED) slope due to effects on funny current and T-type Calcium channels. There is also an (INCREASED/DECREASED) threshold due to effect on L-type Calcium channels.

Increased Decreased ***Increased slope means faster depolarization, and lowered threshold means reaching depolarization quicker as well. ***Beta blockers have the exact opposite effect!

Beta-blockers have anti arrhythmic actions that are mediated by the effects of these drugs on the pacemaker action potential. What do these drugs do to the SA node and AV node?

SA node -- decrease HR (increase RR interval) AV node -- decrease AV conductance (increase PR interval)

Beta-blockers will cause an (INCREASED/DECREASED) slope due to effects on funny current and T-type Calcium channels. They will also cause an (INCREASED/DECREASED) threshold due to the effect on L-type Calcium channels.

Decreased | Increased

What is the mechanism of action for Class 2 drugs?

Beta-blockers

This Class 2 drug is used clinically for cardiac arrhythmias associated with stress and thyroid storm.

Propranolol

Which Class 2 drug would be best suited for the following? - - Atrial fibrillation and flutter - - Paroxysmal supraventricular arrhythmias - - Arrhythmias associated with MI (decreases mortality)

Propranolol

This Class 2 drug is a short-acting selective Beta-1 blocker.

Esmolol

Esmolol has a half-life of _______ due to hydrolysis by blood esterases.

10 min

Which Class 2 drug would be best suited for the following? - - Supraventricular arrhythmias - - Arrhythmias associated with thyrotoxicosis - - Myocardial ischemia or acute MI with arrhythmias - - As adjunct drug in general anesthesia to control arrhythmias in preoperative period

Esmolol

What are adverse effects of beta-blockers (Class 2 drugs)?

- - Reduced CO - - Bronchoconstriction - - Impaired liver glucose mobilization - - Produce unfavorable blood lipoprotein profile (increase VLDL and decrease HDL) - - Sedation, depression - - Withdrawal syndrome associated with sympathetic hyperresponsiveness

What are contraindications for the use of beta-blockers (Class 2 drugs)?

- - Asthma - - Peripheral Vascular Disease - - Raynaud's Syndrome - - Type 1 diabetics on insulin - - Bradyarrhythmias and AV conduction abnormalities - - Severe depression of cardiac function

Class 3 drugs are _________ channel blockers, which regulates action potential.

Potassium

For Class 3 drugs, voltage-gated rapid and slow delayed rectifier K+ channels contribute to regulation of action potential. They are responsible for _________ of the cell membrane during action potential. They also limit the frequency of action potentials by regulating the duration of the ________ ________.

Repolarization | Refractory period

Class 3 drugs block potassium channels, thus prolonging the _______ _______ duration.

Action potential

Class 3 drugs will prolong the ________ on ECG, and prolong the refractory period.

QT interval

This Class 3 drug is one of the most widely used because it also has characteristics of Class 1, 2, and 4 drugs.

Amiodarone

What drug is being described by the following pharmacodynamics? - - Blocks potassium channels - - Prolongs QT interval and APD uniformly over wide range of heart rates - - Blocks inactivated sodium channels - - Possesses adrenolytic activity - - Calcium channel blocking activity - - Causes bradycardia and slows AV conduction

Amiodarone

What is the clinical use of Amiodarone?

- - Recurrent ventricular tachycardia | - - Atrial fibrillation

With the use of Amiodarone, the incidence of this adverse effect is much lower as compared to other Class 3 drugs.

Torsade de pointes

What are adverse effects of the skin that can occur with Amiodarone?

- - Photodermatitis - - Deposits in skin - - Blue-grey skin discoloration in sun-exposed areas

What are adverse effects of the eyes that can occur with Amiodarone?

- - Deposits of drug in cornea and other eye tissues | - - Optical neuritis

How can Amiodarone cause hypo- or hyperthyroidism?

Blocks peripheral conversion of thyroxine to triiodothyronine

Which class 3 drug would have these adverse effects? - - AV block and bradycardia - - Fatal pulmonary fibrosis - - Hepatitis

Amiodarone

This Class 3 drug prolongs APD, but also has Class 2 characteristics as a non-selective beta-blocker.

Sotalol

What is the clinical use for Sotalol?

- - Treat life-threatening ventricular arrhythmias | - - Maintenance of sinus rhythm in pts with A fib

What are the adverse effects of Sotalol?

- - Depression of cardiac function | - - Provokes torsade de pointes

These Class 3 drugs specifically block rapid component of the delayed rectifier potassium current.

Dofetilide | Ibutilide

What is the clinical use for the Class 3 drugs Dofetilide and Ibutilide?

-- Restore sinus rhythm in patients with A fib -- Maintain sinus rhythm after cardioversion in patients with A fib ***(Dofetilide ONLY)***

What are the adverse effects of Class 3 drugs Dofetilide and Ibutilide?

QT interval prolongation and increased risk of ventricular arrhythmias

Class 4 drugs block what channels?

L-type Calcium channels ***These are similar to Na+ channels in fast action potential -- this is pacemaker action potential

Class 4 drugs are active in cells exhibiting pacemaker potential. They will (INCREASE/DECREASE) the slope of phase 0 depolarization and (INCREASE/DECREASE) the L-type Calcium channel threshold potential.

Decrease | Increase

Overall, Class 4 drugs work by slowing the _______ ______ depolarization to reduce heart rate. This in turn prolongs conduction time and refractory period in the ______ ______.

SA Node | AV Node

These Class 4 drugs are used for: -- Termination and prevention of paroxysmal supraventricular tachycardia -- Ventricular rate control in atrial fibrillation and flutter

Verapamil | Diltiazem

The Class 4 drugs Verapamil and Diltiazem have the following cardiac effects: - - Negative inotrophy - - AV block - - SA node arrest - - Bradyarrhythmias - - Hypotension What is the extracardiac adverse effect of Verapamil?

Constipation

Adenosine is a miscellaneous drug agent used to activate A1 adenosine receptors, which is what type of receptor?

GPCR - Gi (inhibitory)

By activating the A1 adenosine receptors, this enhances the ________ current and inhibits _______ and ______ currents. This causes marked hyperpolarization and suppression of action potentials in pacemaker cells.

Potassium Calcium Funny

Adenosine also inhibits ______ conduction and increases _______ nodal refractory period.

AV | AV

This drug is used clinically for conversion to sinus rhythm in paroxysmal supraventricular tachycardia. It is given intravenously to provide rapid relief.

Adenosine

What are adverse effects of Adenosine?

- - SOB - - Bronchoconstriction - - Chest burning - - AV block - - Hypotension