Antidysrhythmics- Chapter 25.pptx

Chapter 25 Antidysrhythmic Drugs  Antidysrhythmics  Dysrhythmia  Any deviation from the normal rhythm of the heart  Arrhythmia  “No rhythm” which implies asystole  Terms dysrhythmia and arrhythmia are used interchangeably with the term arrhythmia bei...

Chapter 25 Antidysrhythmic Drugs  Antidysrhythmics  Dysrhythmia  Any deviation from the normal rhythm of the heart  Arrhythmia  “No rhythm” which implies asystole  Terms dysrhythmia and arrhythmia are used interchangeably with the term arrhythmia being most commonly used.  Antidysrhythmics  Used for the treatment and prevention of disturbances in cardiac rhythm 2  Dysrhythmia  Can develop in association with many conditions  After MI, cardiac surgery, or as a result of CAD  Usually serious and may require treatment with antidysrhythmic drug or nonpharmacological therapies  Disturbances of cardiac rhythm are the result of abnormally functioning cardiac cells. 3  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 4  Resting Membrane Potential  An energy-requiring pump is needed to maintain this uneven distribution of ions.  Sodium-potassium ATPase pump  The RMP results from an uneven distribution of ions across the cell membrane.  Polarization 5  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  Action Potential (Cont.)  Five phases  Phase 0: upstroke Resting cardiac cell membrane suddenly becomes highly permeable to sodium ions; movement through sodium channels Depolarization  Phase 1 Begins a rapid process of repolarization that continues through Phases 2 and 3 to Phase 4, which is the RMP 7  Action Potential Duration  Interval between Phase 0 and Phase 4  Absolute or effective refractory period  Relative refractory period  Threshold potential  Automaticity or pacemaker activity 8  Aspects of Action Potential  SA node, AV node, and His-Purkinje cells all possess the property of automaticity.  SA node is the natural pacemaker of the heart.  SA node has an intrinsic rate of 60 to 100 bpm.  AV node has an intrinsic rate of 40 to 60 bpm.  Ventricular Purkinje fibers have an intrinsic rate of 40 or fewer beats per minute. 9  Electrocardiography  ECG or EKG  P wave  PR interval  QRS complex  ST segment  T wave 10  Common Dysrhythmias  Supraventricular dysrhythmias  Originate above the ventricles in SA or AV node or atrial myocardium  Ventricular dysrhythmias  Originate below the AV node in the His-Purkinje system or ventricular myocardium  Ectopic foci  Outside the conduction system  Conduction blocks  Dysrhythmias that involve the disruption of impulse conduction between the atria and ventricles 11  Common Dysrhythmias (Cont.)  Atrial fibrillation  AV nodal reentrant tachycardia (AVNRT)  Paroxysmal supraventricular tachycardia (PSVT)  Varying degrees of AV block  Premature ventricular contractions (PVC)  Ventricular fibrillation  Ventricular tachycardia 12  Antidysrhythmic Drugs  Categorized according to where and how they affect cardiac cells  Vaughan Williams classification  System commonly used to classify antidysrhythmic drugs  Based on the electrophysiologic effect of particular drugs on the action potential 13  Vaughan Williams Classification: Mechanism of Action and Indications  Class I  Class Ia  Class Ib  Class Ic  Class II  Class III  Class IV 14  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class I  Membrane-stabilizing drugs  Fast sodium channel blockers  Divided into Ia, Ib, and Ic drugs, according to effects 15  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class Ia: procainamide, quinidine, and 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 16  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class Ib: phenytoin, lidocaine  Block sodium channels  Accelerate repolarization  Increase or decrease APD  Lidocaine is used for ventricular dysrhythmias only.  Phenytoin is used for atrial and ventricular tachydysrhythmias caused by digitalis toxicity or long QT syndrome. 17  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.) 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 or flutter, Wolff- Parkinson-White syndrome, supraventricular tachycardia dysrhythmias 18  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class II: beta blockers  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; some used for heart failure 19  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class III: amiodarone, dronedarone, dofetilide, 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 that is resistant to other drugs 20  Vaughan Williams Classification: Mechanism of Action and Indications (Cont.)  Class IV:  Calcium channel blockers Inhibit slow-channel (calcium-dependent) pathways  Depress Phase 4 depolarization  Reduce AV node conduction  Used for paroxysmal supraventricular tachycardia (PSVT); rate control for atrial fibrillation and flutter 21  Contraindications to the Use of Antidysrhythmic Drugs  Known drug allergy  Second- or third-degree AV block, bundle branch block, cardiogenic shock, sick sinus syndrome, and any other ECG changes depending on the clinical judgment of a cardiologist.  Other antidysrhythmic drugs 22 Antidysrhythmics: Adverse Effects  ALL antidysrhythmics can cause dysrhythmias!  Hypersensitivity reactions  Nausea, vomiting, and diarrhea  Dizziness  Headache and blurred vision  Prolongation of the QT interval 23 Antidysrhythmics: Drug Interactions  Coumadin: monitor international normalized ratio  Grapefruit juice: amiodarone, disopyramide, and quinidine 24  Procainamide (Pronestyl)  Class Ia  Uses: atrial and ventricular tachydysrhythmias  Significant adverse effects: include ventricular dysrhythmias, blood disorders, systemic lupus erythematosus (SLE)–like syndrome, nausea, vomiting, diarrhea, fever, leukopenia, maculopapular rash, flushing, and torsades de pointes resulting from prolongation of the QT interval  Contraindications: known hypersensitivity, heart block, and SLE 25  Quinidine (Quinidex)  Class Ia  Both direction action on the electrical activity of the heart and indirect (anticholinergic) effect  Significant adverse effects: cardiac asystole and ventricular ectopic beats  Others: cinchonism (tinnitus, loss of hearing, blurring vision, GI upset)  Black box warning: can cause torsades de pointes 26  Lidocaine (Xylocaine)  Class Ib  Action: raises the ventricular fibrillation threshold  Significant adverse effects: twitching, convulsions, confusion, respiratory depression or arrest, hypotension, bradycardia, and dysrhythmias  Contraindications: hypersensitive, severe SA or atrioventricular (AV) intraventricular block, or Stokes-Adams or Wolff-Parkinson-White syndrome 27  Flecainide (Tambocor)  Class Ic  First-line drug in the treatment of atrial fibrillation  Negative inotropic effect and depresses left ventricular function  Adverse effects: dizziness, visual disturbances, and dyspnea  Contraindications: hypersensitivity, cardiogenic shock, second- or third-degree AV block, and non–life-threatening dysrhythmias 28  Propafenone (Rythmol)  Class Ic  Similar action to flecainide  Mild beta-blocking effects  Use: life-threatening ventricular dysrhythmias, atrial fibrillation  Most common reported adverse reaction: dizziness  Others: metallic taste, constipation, headache, nausea, and vomiting 29  Atenolol (Tenormin)  Class II  Cardioselective beta blocker; preferentially blocks the beta1-adrenergic receptors that are located primarily in the heart.  Noncardioselective beta blockers block not only the beta1-adrenergic receptors in the heart but also the beta2-adrenergic receptors in the lungs and therefore can exacerbate pre-existing asthma or chronic obstructive pulmonary disease.  Uses: antidysrhythmic, hypertension, and angina  Contraindications: severe bradycardia, second- or third-degree heart block, heart failure, cardiogenic shock, or a known hypersensitivity 30  Esmolol (Brevibloc)  Ultrashort-acting beta blocker  Cardioselective, blocks beta1-adrenergic receptors  Use: acute treatment of supraventricular tachydysrhythmias; hypertension; post-MI tachydysrhythmias 31  Metoprolol (Lopressor)  Class II  Another cardioselective beta blocker commonly given after an MI to reduce risk of sudden cardiac death  Treatment of hypertension and angina 32  Amiodarone (Cordarone, Pacerone)  Class III  Markedly prolongs the action potential duration and the effective refractory period in all cardiac tissues  Blocks both the alpha- and beta-adrenergic receptors of the sympathetic nervous system  Uses: one of the most effective antidysrhythmic drugs for controlling supraventricular and ventricular dysrhythmias  Indications: management of sustained ventricular tachycardia, ventricular fibrillation, and nonsustained ventricular tachycardia  Drug of choice for ventricular dysrhythmias according to the Advanced Cardiac Life Support guidelines  Adverse effects: corneal microdeposits, which may cause visual halos, photophobia, and dry eyes; photosensitivity; pulmonary toxicity 33  Amiodarone (Cordarone, Pacerone) (Cont.)  Drug interactions: digoxin and warfarin  Contraindications: hypersensitivity, severe sinus bradycardia or second- or third-degree heart block 34  Ibutilide (Corvert)  Class III  Indicated for atrial dysrhythmias  Dosed based on body weight  Can cause ventricular dysrhythmias 35  Sotalol (Betapace)  Class III  Selective beta blocker  Similar antidysrhythmic properties similar to class III while exerting beta blocker or class II effects on conduction  For life-threatening ventricular dysrhythmias 36  Diltiazem (Cardizem, Others)  Class IV  Temporary control of a rapid ventricular response in patients with atrial fibrillation or flutter and PSVT  Contraindications: hypersensitivity, acute myocardial infarction, pulmonary congestion, Wolff-Parkinson-White syndrome, severe hypotension, cardiogenic shock, sick sinus syndrome, or second- or third-degree AV block 37  Verapamil (Calan)  Class IV  Inhibits calcium ion influx across the slow calcium channels in cardiac conduction time  Results in dramatic effects on the AV node  Used to prevent and convert recurrent PSVT and control ventricular response in atrial flutter or fibrillation  Other uses: treat angina, hypertension, and hypertrophic cardiomyopathy 38  Audience Response System Question #1 A patient has received an IV dose of adenosine, and almost immediately the heart monitor shows asystole. What should the nurse do next? A. Check the patient’s pulse. B. Prepare to administer cardiopulmonary resuscitation. C. Set up for defibrillation. D. Continue to monitor the patient. NOTE: No input is required to proceed. 39  Answer to System Question #1 ANS: D The half-life of adenosine is very fast—only 10 seconds—and the asystole only lasts for a few seconds. The nurse should continue to monitor the patient for therapeutic and adverse effects of the medication. 40  Unclassified Antidysrhythmic  Adenosine (Adenocard)  Slows conduction through the AV node  Used to convert PSVT to sinus rhythm  Very short half-life—less than 10 seconds  Only administered as fast intravenous (IV) push  May cause asystole for a few seconds  Other adverse effects are minimal. 41  Nursing Implications  Obtain a thorough drug and medical history.  Measure baseline blood pressure (BP), pulse, input and output, and cardiac rhythm.  Measure serum potassium levels before initiating therapy. 42  Nursing Implications (Cont.)  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. 43  Nursing Implications (Cont.)  During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, and heart and lung sounds.  Assess plasma drug levels as indicated.  Monitor for toxic effects. 44  Audience Response System Question #2 A patient is in the emergency department with an unspecified supraventricular dysrhythmia. The physician orders a dose of diltiazem (Cardizem) IV push. While the nurse administers the medication through the IV lock, the patient says she feels something wet spilling on her arm. Her heart rate was unchanged. What will the nurse do next? A. Assess the patient for diaphoresis. B. Check the IV lock to see if it is functioning properly. C. Repeat the dose of diltiazem (Cardizem). D. Restart the IV in another location. NOTE: No input is required to proceed. 45  Answer to System Question #2 ANS: B Because the heart rate was unchanged and the patient felt fluid on her arm, the IV lock is probably not working properly. Before anything else is done, the IV lock should be checked for proper functioning. Another dose would be wasted if the IV lock is not working. 46  Nursing Implications  Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses.  Instruct patients to contact their physicians for instructions if a dose is missed.  Instruct patients not to crush or chew oral sustained-release preparations. 47  Audience Response System Question #3 A patient is receiving oral quinidine. Which assessment finding is of most concern? A. Nausea B. Prolonged QT interval C. Diarrhea D. Occasional palpitations NOTE: No input is required to proceed. 48  Answer to System Question #3 ANS: B Patients taking quinidine need to be monitored for prolonged QRS and QT intervals, which may be a precursor to more serious dysrhythmia problems. 49  Nursing Implications  Monitor ECG for prolonged QT interval with use of antidysrhythmics, including amiodarone, procainamide, quinidine, dofetilide, bepridil, sotalol, and flecainide.  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. 50  Nursing Implications (Cont.)  Ensure that the patient knows to notify health care provider of any worsening of dysrhythmia or toxic effects  Shortness of breath  Chest pain  Edema  Gastrointestinal  Dizziness distress  Syncope  Blurred vision  Edema 51  Nursing Implications (Cont.)  Teach patients taking beta blockers, digoxin, and other drugs how to take their own radial pulse for 1 full minute and to notify their physicians before taking the next dose if the pulse is less than 60 beats/min. 52  Nursing Implications (Cont.)  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 53