Drugs Used in Cardiac Arrhythmias Flashcards by Kristina Assaf | Brainscape

Q

Class 1 Sodium Channel-blocking Drugs: 1A

A

– Quinidine (Cardioquin)
– Procainamide (Pronestyl)
– Disopyramide (Norpace)

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Q

Class 1 Sodium Channel-blocking Drugs: 1B

A

– Lidocaine (Xylocaine)

– Mexiletine (Mexitil)

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Q

Class 1 Sodium Channel-blocking Drugs: 1C

A

– Flecainide (Tambocor)

– Propafenone (Rythmol)

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Q

Class 2 Beta Blockers

A

– Esmolol (Brevibloc)

– Propranolol (Inderal)

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Q

Class 3 Potassium Channel-blocking Drugs

A

– Amiodarone (Cordarone)
– Sotalol (Betapace)
– Dofetilide (Tikosyn)
– Ibutilide (Corvert)

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Q

Class 4 Cardioactive Calcium Channel Blockers

A

– Verapamil (Isoptin)

– Diltiazem (Cardizem)

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Q

Miscellaneous agents

A

Adenosine (Adenocard)

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Q

Fast action potential in cardiac muscle: Which phase?

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

Fast action potential in cardiac muscle: Which phase?

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

A

Phase 1

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Q

Fast action potential in cardiac muscle: Which phase?

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

Fast action potential in cardiac muscle: Which phase?

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

A

Phase 3

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Q

Fast action potential in cardiac muscle: Which phase?

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

A

Phase 4

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Q

Effects of Class 1A drugs

A

Block sodium channels
Bind to open (ACTIVATED) sodium channels
Dissociate from channel with INTERMEDIATE kinetics
Block POTASSIUM channels
PROLONG AP duration **
Prolong QRS and QT intervals of the ECG **

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Q

Class 1A: Procainamide

Clinical Use?

A

• Used infrequently (frequent dosing is required,
common occurrence of lupus-related side effects)

• Is effective in sustained VENTRICULAR TACHYCARDIAS and arrhythmias associated with myocardial infarction (not
a first choice drug for these indications)

• Sidenote: it directly depresses the activities of SA and AV nodes

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Q

Class 1A: Procainamide

Adverse effects?

A

• Cardiac
– QT interval prolongation
– Induction of torsade de pointes
arrhythmias and syncope 
– Excessive inhibition of conduction

• Extracardiac
– Lupus erythematosus syndrome with arthritis, pleuritis, pulmonary disease, hepatitis and fever
– Nausea, diarrhea
– Agranulocytosis

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Q

Class 1A: Quinidine

Pharmacodynamics and clinical use?

A

– Affords antimuscarinic effect on the heart –> may ENHANCE AV conductance

– Exhibits beta-blocking activity (effect on PR interval is
variable)

– May cause HYPOTENSION –> tachycardia

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Q

Class 1A: Quinidine

Clinical use?

A

Rarely used because of cardiac and extracardiac adverse

effects and the availability of better-tolerated antiarrhythmic drugs

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Q

Class 1A: Quinidine

Adverse effects?

A

• Cardiac:
– QT interval prolongation
– Induction of torsade de pointes arrhythmia and
syncope
– Excessive slowing of conduction throughout the
heart

• Extracardiac:
– GI side effects (diarrhea, nausea, vomiting)
– Headache, dizziness, tinnitus (cinchonism)
– Thrombocytopenia, hepatitis, fever

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Q

Class 1A: Disopyramide

Clinical use?

A

Recurrent ventricular arrhythmias

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Q

Class 1A: Disopyramide

Adverse effects?

A

• Cardiac: QT interval prolongation, induction of torsade de pointes arrhythmia and syncope, negative inotropic effect – may precipitate heart failure, excessive depression of cardiac conduction

• Extracardaic: atropine-like symptoms – urinary
retention, dry mouth, blurred vision, constipation, exacerbation of glaucoma

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Q

Effect of Class 1B Drugs

A

Block sodium channels
Bind to INACTIVATED sodium channels (bind to depolarized cells)
Dissociate from channel with fast kinetics
SHORTEN the AP
Do NOT block potassium channels
Do NOT prolong AP or QT duration

Q

Class 1B: Lidocaine

Clinical use?

A

Termination of ventricular tachycardia in the setting

of acute myocardial ischemia

Q

Class 1B: Lidocaine

Adverse effects?

A

• The least toxic of all Class 1 drugs

• Cardiovascular: may cause HYPOTENSION in patients
with heart failure by inhibiting cardiac contractility, proarrhythmic effects are uncommon

• Neurological effects: paresthesias, tremor, slurred
speech, convulsions

Q

Class 1B: Mexiletine

Clinical use?

A

• Ventricular arrhythmias

• To relieve chronic pain, especially pain due to
diabetic neuropathy and nerve injury

Q

Class 1B: Mexiletine

Adverse effects?

A

Tremor
Blurred vision
Nausea
Lethargy

Q

Effect of Class 1C Drugs

A

Block sodium channels
Bind to open (ACTIVATED) sodium channels
Dissociate from channel with SLOW kinetics
Block certain potassium channels **
Do NOT prolong AP duration and QT interval duration of the ECG **
Prolong QRS interval duration **

Q

Class 1C : Flecainide

What channels does it block?

A

Blocks sodium and potassium channels

Q

Class 1C : Flecainide

Clinical use?

A

In patients with otherwise normal hearts who have

supraventricular arrhythmias

Q

Class 1C : Flecainide

Adverse effects?

A

• May be very effective in suppressing premature
ventricular contractions, but may cause severe exacerbation of ventricular arrhythmias when administered to
– Patients with preexisting ventricular
tachyarrhythmias
– Patients with a previous myocardial infarction
– Patients with ventricular ectopic rhythms

Q

Class 1C : Propafenone

Clinical use?

A

Supraventricular arrhythmias in patients without structural disease

Q

Class 1C : Propafenone

Adverse effects?

A

Exacerbation of ventricular arrhythmias
A metallic taste
Constipation

Q

Class 2 Beta-Blockers

Effect on AP?

A

• Slow action potential
– Sinoatrial node – decrease HR (increase RR interval)

– AV node – decrease AV conductance (increase
PR interval)

Q

Class 2 Beta-Blockers:

Clinical use of propranolol in cardiac arrhythmias?

A

Arrhythmias associated with stress and THYROID storm
Atrial fibrillation and flutter
Paroxysmal supraventricular arrhythmias

• Arrhythmias associated with MI
– Decrease mortality in patients with MI

Q

Class 2 Beta-Blockers: Esmolol

Clinical use?

A

Supraventricular arrhythmias
Arrhythmias associated with thyrotoxicosis

• Myocardial ischemia or acute myocardial infarction
with arrhythmias

• As an adjunct drug in general anesthesia to control
arrhythmias in perioperative period

Q

Adverse effects of Beta-blockers?

A

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

Q

Contraindications to Beta-blockers?

A

– Asthma
– Peripheral vascular disease
– Raynaud’s syndrome
– Type 1 diabetics on insulin
– Bradyarrhythmias and AV conduction abnormalities
– Severe depression of cardiac function

Q

Class 3 Potassium Channel Blockers:

Effects of Class 3 drugs?

A

– Block potassium channels
– Prolong action potential duration
– Prolong QT interval on ECG
– Prolong refractory period

Q

Class 3 Potassium Channel Blockers: Amiodarone

Clinical use?

A

Recurrent ventricular tachycardia

* Atrial fibrillation

Q

Class 3 Potassium Channel Blockers: Amiodarone

Effects on heart rate and conduction?

A

Has calcium channel blocking activities
Causes bradycardia and slows AV conduction
Causes peripheral vasodilation (effect may be related to the action of the vehicle)

Q

Class 3 Potassium Channel Blockers: Amiodarone

Adverse effects?

A

• Cardiac
- AV block and bradycardia
- Incidence of torsade de pointes is low as compared to
other Class 3 drugs

• Extracardiac
- Fatal pulmonary fibrosis
- Hepatitis
- Photodermatitis, deposits in the skin, gives blue-grey
skin discoloration in sun-exposed areas
- Deposits of drug in cornea and other eye tissues, optical
neuritis
- Blocks the peripheral conversion of thyroxine to
triiodothyronine, also a source of inorganic iodine in the
body – may cause HYPO- OR HYPERTHYROIDISM

Q

Class 3 Potassium Channel Blockers: Sotalol

Clinical use?

A

• Treatment of life-threatening ventricular
arrhythmias

• Maintenance of sinus rhythm in patients with atrial
fibrillation

Q

Class 3 Potassium Channel Blockers: Sotalol

Adverse effects?

A

Depression of cardiac function

* Provokes torsade de pointes

Q

Class 3 Potassium Channel Blockers: Dofetilide

Clinical use?

A

• Restore sinus rhythm in patients with atrial
fibrillation

• Maintain the sinus rhythm after cardioversion in
patients with atrial fibrillation

Q

Class 3 Potassium Channel Blockers: Dofetilide

Adverse effects?

A

QT interval prolongation and increased risk of

ventricular arrhythmias

Q

Class 3 Potassium Channel Blockers: Ibutilide

Clinical use?

A

Conversion of atrial flutter and atrial fibrillation to sinus rhythm

Q

Class 3 Potassium Channel Blockers: Ibutilide

Adverse effects?

A

QT interval prolongation and increased risk of ventricular arrhythmias (patients require continuous ECG monitoring until QTc returns to baseline)

Q

Effect of Class 4 L-type calcium channel blockers

A

• Block both ACTIVATED AND INACTIVATED L-type
calcium channels

• Active in slow response cells

Decrease the slope of phase 0 depolarization
Increase L-type Ca2+ channel threshold potential
Prolong refractory period in AV node

• Slow sinoatrial node depolarization, cause
bradycardia

• Prolong action potential duration and conduction time in AV node

Q

Effect of Class 4 L-type calcium channel blockers:

Clinical use?

A

Termination and prevention of paroxysmal supraventricular tachycardia
Ventricular rate control in atrial fibrillation and flutter

Q

Effect of Class 4 L-type calcium channel blockers:

Adverse effects?

A

• Cardiac
– Negative inotropy 
– AV block 
– Sinoatrial node arrest 
– Bradyarrhythmias 
– Hypotension

• Extracardiac
– Constipation (Verapamil)

Q

Miscellaneous: Adenosine

Effects of Adenosine

A

– Activates potassium current and inhibits Ca2+ and
Funny currents, causing marked hyperpolarization and suppression of action potentials in slow cells

– Inhibits AV conduction and increases nodal refractory period

Q

Miscellaneous: Adenosine

Clinical use?

A

Conversion to sinus rhythm in paroxysmal supraventricular tachycardia

Q

Miscellaneous: Adenosine

Adverse effects?

A

• Shortness of breath

• Bronchoconstriction (both A1
and A2B adenosine receptors cause bronchoconstriction)

Chest burning
AV block
Hypotension