Antiarrhythmics Pharmacotherapy Review

A set of practice flashcards in question-and-answer format covering antiarrhythmic medication classifications, mechanisms of action, dosages, toxicity signs, and nursing implications.

What is the primary therapeutic goal before initiating antiarrhythmic pharmaceutical therapy?

To decrease symptomatology and increase hemodynamic performance, ensuring treatable causes for arrhythmia (such as electrolyte replacement) are addressed before drug initiation.

Which three ions are utilized to produce cardiac action potentials in myocytes?

$\text{Na}^+$, $\text{K}^+$, and $\text{Ca}^{++}$

What are the five distinct phases of fast cardiac action potentials?

Phase 0: Depolarization, Phase 1: (Partial) repolarization, Phase 2: Plateau, Phase 3: Repolarization, and Phase 4: Stable potential.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class Ia antiarrhythmics?

Class Ia drugs act on the atrium and ventricle; representative drugs are Quinidine, Procainamide, and Disopyramide.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class Ib antiarrhythmics?

Class Ib drugs act on the ventricle; representative drugs are Lidocaine and Phenytoin.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class Ic antiarrhythmics?

Class Ic drugs act on the atrium and ventricle; representative drugs are Flecainide and Propafenone.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class II antiarrhythmics?

Class II drugs act on the AV node and ventricle; representative drugs are Propranolol, Esmolol, Metoprolol, and Atenolol.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class III antiarrhythmics?

Class III drugs act on the atrium and ventricle; representative drugs are Amiodarone and Sotalol.

Under the Vaughan-Williams classification system, what are the representative drugs and cardiac site of action for Class IV antiarrhythmics?

Class IV drugs act on the AV node; representative drugs are Verapamil and Diltiazem.

Which drugs are listed under Class V (Other) antiarrhythmics?

Adenosine and Digoxin.

Why are Class Ia antiarrhythmics referred to as a "Swiss Army Knife" antiarrhythmic, and why is their use infrequent?

They are effective in treating most types of tachyarrhythmias, but their use is infrequent due to a high propensity for organ toxicity and being proarrhythmic by increasing the QT interval.

How do Class Ib antiarrhythmics affect the sodium channels and action potential?

They block the fast inward sodium channel (slowing depolarization) and decrease the refractory periods (making the action potential thinner).

What is the preferred weight-based bolus dose for Lidocaine?

A $1.5\,\text{mg/kg}$ bolus.

What is the maintenance drip dosage for Lidocaine once conversion is achieved?

$$25 - 50\,\text{mcg/kg/min}$$

What signs and symptoms of Lidocaine toxicity are represented by the acronym SPAMS?

S: Slurred speech, paresthesia, numbness of lips and tongue. A: Altered mental status (drowsiness, dizziness, dysrhythmias, restlessness, confusion). M: Muscle twitching. S: Seizures, convulsions, respiratory depression, cardiac arrest.

In which patient population are the proarrhythmic effects of Class Ic antiarrhythmics most often seen?

Patients with structural heart disease.

What are the contraindications to Class II beta blocker therapy?

Pulmonary problems, conduction defects, or untreated severe CHF.

What general rule regarding Class III antiarrhythmics and heart rate does Amiodarone violate?

While effectiveness of Class III antiarrhythmics typically decreases as heart rate increases, Amiodarone is the exception to this rule.

What is the IV dosage of Amiodarone for pulseless ventricular tachycardia?

An initial bolus of $300\,\text{mg}$, followed by a $150\,\text{mg}$ dose $3 - 5\,\text{minutes}$ later if needed.

What long-term toxicity is associated with chronic Amiodarone use?

Pulmonary toxicity / pulmonary dysfunction, including Acute Respiratory Distress Syndrome (ARDS).

What are the brand names listed for Verapamil and Diltiazem?

Verapamil: Calan, Covera, Verelan. Diltiazem: Cardizem.

Why are Class IV calcium channel blockers contraindicated in ventricular tachycardias?

Because they reduce cardiac contractility, slow AV node conduction, and are specifically intended for slowing ventricular response rates to rapid atrial rhythms and AV nodal reentry tachycardias, not VT.

What is the dosage and administration interval for IV Adenosine?

An initial IV bolus of $6\,\text{mg}$, which may be followed by a $12\,\text{mg}$ bolus every $1 - 2\,\text{minutes}$ if necessary (maximum of 3 total doses).

How should Adenosine be administered due to its short half-life?

Push fast using a three-way stopcock to follow quickly with a flush.

At what blood concentration level does Digoxin toxicity occur?

Over $2\,\text{ng/ml}$.

What vital sign threshold must be met before administering Digoxin?

The apical pulse must be $60\,\text{bpm}$ or greater.