1. Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. CHAPTER 23 Antidysrhythmic Drugs

2. 2 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Antidysrhythmics  Dysrhythmia  Any deviation from the normal rhythm of the heart  Antidysrhythmics  Used for the treatment and prevention of disturbances in cardiac rhythm

3. 3 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Cardiac Cell  Inside the resting cardiac cell there is a net negative charge relative to the outside of the cell  This difference in electronegative charge results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane  Resting membrane potential (RMP)

4. 4 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Resting Membrane Potential (RMP)  An energy-requiring pump is needed to maintain this uneven distribution of ions  Sodium-potassium ATPase pump

5. 5 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Action Potential  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 an electrical impulse spreading across the cardiac cells  This electrical impulse leads to contraction of the myocardial muscle

6. 6 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Action Potential (cont’d)  Four phases  The SA node and the Purkinje cells each have separate action potentials

7. 7 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

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10. 10 Action Potential Duration  Absolute or effective refractory period  Relative refractory period  Threshold potential  Automaticity or pacemaker activity

11. 11 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

12. 12 Electrocardiography  ECG or EKG  P wave  PR interval  QRS complex  ST segment  T wave

13. 13 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

14. 14 Common Dysrhythmias  Supraventricular dysrhythmias  Ventricular dysrhythmias  Ectopic foci  Conduction blocks

15. 15 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification  System commonly used to classify antidysrhythmic drugs  Based on the electrophysiologic effect of particular drugs on the action potential

16. 16 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification (cont’d)  Class I  Class Ia  Class Ib  Class Ic  Class II  Class III  Class IV  Other

17. 17 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action  Class I  Membrane-stabilizing drugs  Fast sodium channel blockers  Divided into Ia, Ib, and Ic drugs, according to effects

18. 18 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications  Class I: moricizine  General class I drug  Has characteristics of all three subclasses  Used for symptomatic ventricular and life-threatening dysrhythmias

19. 19 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class Ia: quinidine, procainamide, disopyramide  Block sodium (fast) channels  Delay repolarization  Increase APD  Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome

20. 20 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class Ib: phenytoin, lidocaine  Block sodium channels  Accelerate repolarization  Increase or decrease APD  Used for ventricular dysrhythmias only Premature ventricular contractions, ventricular tachycardia, ventricular fibrillation Premature ventricular contractions, ventricular tachycardia, ventricular fibrillation

21. 21 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class Ic: 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, Wolff- Parkinson-White syndrome, supraventricular tachycardia dysrhythmias

22. 22 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class II: beta-blockers: atenolol, esmolol, metaprolol, 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  Also used as antianginal and antihypertensive drugs

23. 23 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class III: amiodarone, sotalol*, ibutilide, others  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 Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs Sustained ventricular tachycardia Sustained ventricular tachycardia *Sotalol also exhibits Class II properties

24. 24 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Mechanism of Action and Indications (cont’d)  Class IV: verapamil, diltiazem  Calcium channel blockers Inhibit slow-channel (calcium-dependent) pathways Inhibit slow-channel (calcium-dependent) pathways  Depress phase 4 depolarization  Reduce AV node conduction  Used for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutter

25. 25 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Vaughan Williams Classification: Other Antidysrhythmics  Digoxin, adenosine  Have properties of several classes and are not placed into one particular class

26. 26 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Unclassified Antidysrhythmic  adenosine (Adenocard)  Slows conduction through the AV node  Used to convert paroxysmal supraventricular tachycardia to sinus rhythm  Very short half-life—less than 10 seconds  Only administered as fast IV push  May cause asystole for a few seconds  Other adverse effects minimal

27. 27 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Antidysrhythmics: Adverse Effects  ALL antidysrhythmics can cause dysrhythmias!  Hypersensitivity reactions  Nausea  Vomiting  Diarrhea  Dizziness  Blurred vision  Headache

28. 28 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications  Obtain a thorough drug and medical history  Measure baseline BP, P, I&O, and cardiac rhythm  Measure serum potassium levels before initiating therapy

29. 29 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Assess for conditions that may be contraindications for use of specific drugs  Assess for potential drug interactions  Instruct patients to report dosing schedules and adverse effects to physician

30. 30 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and lung sounds  Assess plasma drug levels as indicated  Monitor for toxic effects

31. 31 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses  Instruct patients to contact their physician for instructions if a dose is missed  Instruct patients not to crush or chew oral sustained-release preparations

32. 32 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  For class I drugs, monitor ECG for QT intervals prolonged more than 50%  Administer IV infusions with an IV pump  Solutions of lidocaine that contain epinephrine should not be given IV—they are to be used ONLY as local anesthetics

33. 33 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Ensure that the patient knows to notify health care provider of any worsening of dysrhythmia or toxic effects  Shortness of breath  Edema  Dizziness  Syncope  Chest pain  GI distress  Blurred vision  Edema

34. 34 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Teach patients taking beta-blockers, digoxin, and other drugs 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

35. 35 Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Monitor for therapeutic response  Decreased BP in hypertensive patients  Decreased edema  Decreased fatigue  Regular pulse rate  Pulse rate without major irregularities  Improved regularity of rhythm  Improved cardiac output