1. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmic Agents

2. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics Dysrhythmia Any deviation from the normal rhythm of the heartAny deviation from the normal rhythm of the heartAntidysrhythmics Drugs used for the treatment and prevention of disturbances in cardiac rhythmDrugs used for the treatment and prevention of disturbances in cardiac rhythm

3. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Cardiac Cell Inside the cardiac cell, there exists a net negative charge relative to the outside of the cell.Inside the cardiac cell, there exists a net negative charge relative to the outside of the cell.

4. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Resting Membrane Potential: RMP This difference in the electronegative charge.This difference in the electronegative charge. Results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane.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.An energy-requiring pump is needed to maintain this uneven distribution of ions. Sodium-potassium ATPase pumpSodium-potassium ATPase pump

5. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Instructors may wish to insert: EIC Image # 61: Heart and Conduction System EIC Image # 63: Resting Membrane Potential of a Cardiac Cell

6. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Action Potential A change in the distribution of ions causes cardiac cells to become excited.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.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.This electrical impulse leads to contraction of the myocardial muscle.

7. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Action Potential Four Phases The SA node and the Purkinje cells each have separate action potentials.The SA node and the Purkinje cells each have separate action potentials.

8. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Instructors may wish to insert: EIC Image # 64: Action Potentials: Phases (SA Node) EIC Image # 65: Action Potentials: Purkinje Fiber EIC Image # 66: Action Potentials: Intervals

9. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification System commonly used to classify antidysrhythmic drugsSystem commonly used to classify antidysrhythmic drugs

10. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class 1Class 1 –Class Ia –Class Ib –Class Ic Class IIClass II Class IIIClass III Class IVClass IV OtherOther

11. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class I Membrane-stabilizing agentsMembrane-stabilizing agents Fast sodium channel blockersFast sodium channel blockers Divided into Ia, Ib, and Ic agents, according to effectsDivided into Ia, Ib, and Ic agents, according to effects

12. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class I moricizine General Class I agentGeneral Class I agent Has characteristics of all three subclassesHas characteristics of all three subclasses Used for symptomatic ventricular and life- threatening dysrhythmiasUsed for symptomatic ventricular and life- threatening dysrhythmias

13. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class Ia quinidine, procainamide, disopyramide Block sodium channelsBlock sodium channels Delay repolarizationDelay repolarization Increase the APDIncrease the APD Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndromeUsed for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome

14. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class Ib tocainide, mexiletine, phenytoin, lidocaine Block sodium channelsBlock sodium channels Accelerate repolarizationAccelerate repolarization Decrease the APDDecrease the APD Used for ventricular dysrhythmias only (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation)Used for ventricular dysrhythmias only (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation)

15. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class Ic encainide, flecainide, propafenone Block sodium channels (more pronounced effect)Block sodium channels (more pronounced effect) Little effect on APD or repolarizationLittle effect on APD or repolarization Used for severe ventricular dysrhythmiasUsed for severe ventricular dysrhythmias May be used in atrial fibrillation/flutterMay be used in atrial fibrillation/flutter

16. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class II Beta blockers: atenolol, esmolol, petaprolol, propranolol Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction systemReduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction system Depress phase 4 depolarizationDepress phase 4 depolarization General myocardial depressants for both supraventricular and ventricular dysrhythmiasGeneral myocardial depressants for both supraventricular and ventricular dysrhythmias

17. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class III amiodarone, bretylium, sotalol, ibutilide Increase APDIncrease APD Prolong repolarization in phase 3Prolong repolarization in phase 3 Used for dysrhythmias that are difficult to treatUsed for dysrhythmias that are difficult to treat Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugsLife-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs Sustained ventricular tachycardiaSustained ventricular tachycardia

18. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Class IV verapamil, diltiazem Calcium channel blockersCalcium channel blockers Depress phase 4 depolarizationDepress phase 4 depolarization Used for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutterUsed for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutter

19. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Vaughan Williams Classification Other Antidysrhythmics digoxin, adenosine Have properties of several classes and are not placed into one particular classHave properties of several classes and are not placed into one particular class

20. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics Digoxin Cardiac glycosideCardiac glycoside Inhibits the sodium-potassium ATPase pumpInhibits the sodium-potassium ATPase pump Positive inotrope—improves the strength of cardiac contractionPositive inotrope—improves the strength of cardiac contraction Allows more calcium to be available for contractionAllows more calcium to be available for contraction Used for CHF and atrial dysrhythmiasUsed for CHF and atrial dysrhythmias Monitor potassium levels, drug levels, and for toxicityMonitor potassium levels, drug levels, and for toxicity

21. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics adenosine (Adenocard) Slows conduction through the AV nodeSlows conduction through the AV node Used to convert paroxysmal supraventricular tachycardia to sinus rhythmUsed to convert paroxysmal supraventricular tachycardia to sinus rhythm Very short half-lifeVery short half-life Only administered as fast IV pushOnly administered as fast IV push May cause asystole for a few secondsMay cause asystole for a few seconds Other side effects minimalOther side effects minimal

22. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Side Effects ALL antidysrhythmics can cause dysrhythmias!! Hypersensitivity reactionsHypersensitivity reactions –Nausea –Vomiting –Diarrhea –Dizziness –Blurred vision –Headache

23. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications Obtain a thorough drug and medical history.Obtain a thorough drug and medical history. Measure baseline BP, P, I & O, and cardiac rhythm.Measure baseline BP, P, I & O, and cardiac rhythm. Measure serum potassium levels before initiating therapy.Measure serum potassium levels before initiating therapy.

24. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications Assess for conditions that may be contraindications for use of specific agents.Assess for conditions that may be contraindications for use of specific agents. Assess for potential drug interactions.Assess for potential drug interactions. Instruct patients regarding dosing schedules and side effects to report to physician.Instruct patients regarding dosing schedules and side effects to report to physician.

25. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and breath sounds.During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and breath sounds. Assess plasma drug levels as indicated.Assess plasma drug levels as indicated. Monitor for toxic effects.Monitor for toxic effects.

26. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses.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.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.Instruct patients not to crush or chew any oral sustained-release preparations.

27. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications For class I agents, monitor ECG for QT intervals prolonged more than 50%.For class I agents, monitor ECG for QT intervals prolonged more than 50%. IV infusions should be administered with an IV pump.IV infusions should be administered with an IV pump.

28. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications 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.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.

29. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved. Antidysrhythmics: Nursing Implications Monitor for therapeutic response: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