Dysrhythmia Any deviation from the normal rhythm of the

heart

Antidysrhythmics Drugs used for the treatment and prevention of

disturbances in cardiac rhythm

Inside the cardiac cell, there exists a net negative charge relative to the outside of

the cell.

This difference in the electronegative charge.

Results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane.

An energy-requiring pump is needed to maintain this uneven distribution of ions.

Sodium-potassium ATPase pump

A change in the distribution of ions causes cardiac cells to become excited.

The movement of ions across the cardiac cell’s membrane results in the propagation of an electrical impulse.

This electrical impulse leads to contraction of the myocardial muscle.

Four Phases The SA node and the Purkinje cells each have

separate action potentials.

System commonly used to classify antidysrhythmic drugs

Class 1 Class Ia Class Ib Class Ic

Class II Class III Class IV Other

Class I Membrane-stabilizing agents Fast sodium channel blockers Divided into Ia, Ib, and Ic agents, according

to effects

Class Imoricizine General Class I agent Has characteristics of all three subclasses Used for symptomatic ventricular and life-

threatening dysrhythmias

Class Iaquinidine, procainamide, disopyramide Block sodium channels Delay repolarization Increase the APD Used for atrial fibrillation, premature atrial

contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome

Class Ibtocainide, mexiletine, phenytoin, lidocaine Block sodium channels Accelerate repolarization Decrease the APD Used for ventricular dysrhythmias only

(premature ventricular contractions, ventricular tachycardia, ventricular fibrillation)

Class Icencainide, flecainide, propafenone Block sodium channels (more pronounced

effect) Little effect on APD or repolarization Used for severe ventricular dysrhythmias May be used in atrial fibrillation/flutter

Class IIBeta blockers: atenolol, esmolol,

petaprolol, propranolol Reduce or block sympathetic nervous system

stimulation, thus reducing transmission of impulses in the heart’s conduction system

Depress phase 4 depolarization General myocardial depressants for both

supraventricular and ventricular dysrhythmias

Class IIIamiodarone, bretylium, sotalol, ibutilide Increase APD Prolong repolarization in phase 3 Used for dysrhythmias that are difficult to treat Life-threatening ventricular tachycardia or

fibrillation, atrial fibrillation or flutter—resistant to other drugs

Sustained ventricular tachycardia

Class IVverapamil, diltiazem Calcium channel blockers Depress phase 4 depolarization Used for paroxysmal supraventricular

tachycardia; rate control for atrial fibrillation and flutter

Other Antidysrhythmicsdigoxin, adenosine Have properties of several classes and are not

placed into one particular class

Digoxin Cardiac glycoside

Inhibits the sodium-potassium ATPase pump

Positive inotrope—improves the strength of cardiac contraction

Allows more calcium to be available for contraction

Used for CHF and atrial dysrhythmias

Monitor potassium levels, drug levels, and for toxicity

adenosine (Adenocard) Slows conduction through the AV node Used to convert paroxysmal supraventricular

tachycardia to sinus rhythm Very short half-life Only administered as fast IV push May cause asystole for a few seconds Other side effects minimal

ALL antidysrhythmics can cause dysrhythmias!!

Hypersensitivity reactions Nausea Vomiting Diarrhea Dizziness Blurred vision Headache

Obtain a thorough drug and medical history.

Measure baseline BP, P, I & O, and cardiac rhythm.

Measure serum potassium levels before initiating therapy.

Assess for conditions that may be contraindications for use of specific agents.

Assess for potential drug interactions. Instruct patients regarding dosing

schedules and side effects to report to physician.

During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and breath sounds.

Assess plasma drug levels as indicated. Monitor for toxic effects.

Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses.

Patients who miss a dose should contact their physician for instructions if a dose is missed.

Instruct patients not to crush or chew any oral sustained-release preparations.

For class I agents, monitor ECG for QT intervals prolonged more than 50%.

IV infusions should be administered with an IV pump.

Patients taking propranolol, digoxin, and other agents should be taught how to take their own radial pulse for 1 full minute, and to notify their physician if the pulse is less than 60 beats/minute before taking the next dose of medication.

Monitor for therapeutic response: Decreased BP in hypertensive patients Decreased edema Regular pulse rate or Pulse rate without major irregularities, or Improved regularity of rhythm