Lehne Chapter 49: Antidysrhythmic Drugs
ANS: A Calcium channel blockade has the same impact on cardiac action potentials as does beta blockade, so these agents have nearly identical effects on cardiac function; that is, they reduce automaticity in the SA node, delay conduction through the AV node, and reduce myocardial contractility. Potassium channel blockers act by delaying repolarization of fast potentials. Sodium channel blockers block sodium channels to slow impulse conduction in the atria, ventricles, and His-Purkinje system.
1. Which two classes of antidysrhythmic drugs have nearly identical cardiac effects? a. Beta blockers and calcium channel blockers b. Beta blockers and potassium channel blockers c. Calcium channel blockers and sodium channel blockers d. Sodium channel blockers and potassium channel blockers
ANS: A Amiodarone has many toxic effects. Liver toxicity is rare but serious and should be reported and the drug discontinued. Dermatologic toxicity can occur, and sunblock helps protect the skin, which, with prolonged exposure to the sun, can turn bluish gray. Drinking grapefruit juice can increase amiodarone levels. Pulmonary toxicity is the greatest concern, and patients with pulmonary symptoms should report these to the provider.
10. A nurse is providing teaching to a patient who is admitted to the hospital for initiation of treatment with amiodarone [Cordarone] for atrial fibrillation that has been refractory to other medications. Which statement by the patient indicates a need for further teaching? a. "I may have itching, malaise, and jaundice, but these symptoms will subside." b. "I need to use sunblock to help keep my skin from turning bluish gray." c. "I should not drink grapefruit juice while taking this medication." d. "I should report shortness of breath and cough and stop taking the drug immediately."
ANS: D Torsades de pointes is a dysrhythmia that can occur with prolongation of the QT interval and can progress to fatal ventricular fibrillation. A prolonged QT interval does not signal the development of AV block, bradycardia, or SVT.
11. A patient is in the intensive care unit after a myocardial infarction. The nurse notes that the QT interval on this patient's electrocardiogram has been elongating. The nurse is concerned that which cardiac dysrhythmia may occur? a. AV block b. Bradycardia c. Supraventricular tachycardia d. Torsades de pointes
ANS: D Because dronedarone prolongs the QT interval by about 10 msec, it should not be used in patients with a QT interval of more than 500 msec. It does not have significant pulmonary or thyroid toxicity. It should not be used in patients with a PR interval of more than 280 msec.
12. A prescriber is considering prescribing the amiodarone derivative dronedarone [Multaq] for a patient with atrial flutter. The nurse should be concerned about which of the following? a. History of asthma b. History of hypothyroidism c. PR interval of 260 msec d. QT interval of 520 msec
ANS: A Calcium channel blockers, such as verapamil, can increase levels of digoxin, so patients taking these drugs may need to have their digoxin dose reduced. Increasing the dose of digoxin can result in digoxin toxicity. Verapamil does not affect warfarin levels.
13. A prescriber orders verapamil [Covera-HS] for a patient who is taking digoxin [Lanoxin] and warfarin. The nurse will expect the prescriber to ____ the dose of ____. a. lower; digoxin b. increase; digoxin c. lower; warfarin d. increase; warfarin
ANS: B Adenosine is used to terminate paroxysmal supraventricular tachycardia (SVT) and Wolff-Parkinson-White (WPW) syndrome, not to prevent symptoms. Adenosine suppresses action potentials in the SA and AV nodes. Because it has a very short half-life of 1.5 to 10 seconds, it must be given IV bolus, as close to the heart as possible. Adenosine is not active against atrial fibrillation, atrial flutter, or ventricular dysrhythmias.
14. A nurse is discussing adenosine with a nursing student. Which statement by the student indicates a need for further teaching? a. "Adenosine acts by suppressing action potentials in the SA and AV nodes." b. "Adenosine can be used to prevent paroxysmal supraventricular tachycardia and Wolff-Parkinson-White syndrome." c. "Adenosine has a half-life that lasts only a few seconds and must be given intravenously." d. "Adenosine is not effective for treating atrial fibrillation, atrial flutter, or ventricular dysrhythmias."
ANS: B Digoxin increases automaticity in the Purkinje fibers, which contributes to dysrhythmias caused by digoxin. Decreased automaticity in the AV node is a desired effect of digoxin. Digoxin does not increase automaticity in the SA node. It does not increase AV node conduction.
15. A nursing student asks a nurse how digoxin causes dysrhythmias. The nurse correctly states that digoxin: a. reduces automaticity in the AV node. b. increases automaticity in the Purkinje fibers. c. increases automaticity in the SA node. d. speeds up AV conduction.
ANS: D With ventricular fibrillation there is no cardiac output, because the pumping action of the heart stops. Treatment with electrical countershock is indicated to restore cardiac function. Atrial flutter, tachycardia, and first-degree heart block do not result in the lowest cardiac output.
16. The nurse is teaching a class on dysrhythmias and associated therapy. The nurse asks the class, "Which cardiac dysrhythmia would result in the lowest cardiac output, and what treatment would be effective?" The class best demonstrates understanding by responding that ____ results in the lowest cardiac output, and treatment includes ____. a. atrial flutter; lidocaine b. tachycardia; atropine c. first-degree heart block; verapamil [Calan] d. ventricular fibrillation; defibrillation
ANS: C In the CAST, class IC dysrhythmic drugs were used to prevent dysrhythmias after MI. These drugs were found to actually double the rate of mortality. The antidysrhythmic drugs did not reduce mortality or the risk of a second MI. They should not be used for any MI patients with associated dysrhythmias unless the dysrhythmias are life threatening.
17. The nurse educator is providing patient education about the Cardiac Arrhythmia Suppression Trial (CAST). The nurse correctly explains that the trial demonstrated what effect from the pharmacologic suppression of dysrhythmias? a. It reduced mortality by 50% but increased morbidity. b. It significantly reduced the risk of a second myocardial infarction (MI). c. It doubled the risk of a second MI. d. It should be used in all patients who have had an MI, regardless of rhythm.
ANS: C Dofetilide is used for patients with severe, highly symptomatic atrial dysrhythmias because of its higher than usual risk of torsades de pointes. It is used only when other medications have not been effective. It is used for hospitalized patients with close ECG monitoring.
18. The nurse is teaching a group of nursing students about dofetilide [Tikosyn] to treat dysrhythmias. Which statement by a student indicates understanding of the teaching? a. "Dofetilide is a first-line medication to treat atrial flutter or atrial fibrillation." b. "Dofetilide carries a lower risk of causing torsades de pointes than other drugs." c. "Dofetilide is used for patients with severe symptoms of atrial dysrhythmias." d. "Dofetilide may be safely used as outpatient therapy to treat atrial fibrillation."
ANS: B Dysrhythmic activity in the atria does not significantly reduce cardiac output but can be dangerous when dysrhythmic impulses cross the AV node, causing ventricular dysrhythmias, which can be life threatening. Treating ventricular dysrhythmia helps improve ventricular pumping. These drugs do not restore normal sinus rhythm. To prevent stroke, an anticoagulant, such as warfarin, is used. Slowing ventricular contraction does not affect the rate of atrial contraction. Restoring normal sinus rhythm requires cardioversion, short-term treatment with amiodarone or sotalol, or RF ablation of the dysrhythmia source.
2. A patient with atrial fibrillation is taking verapamil [Calan]. The patient has read about the drug on the Internet and wants to know why a drug that affects the rate of ventricular contraction is used to treat an abnormal atrial contraction. What will the nurse tell the patient? a. "Drugs that treat ventricular dysrhythmias help to restore normal sinus rhythm." b. "Atrial dysrhythmias can have life-threatening effects on ventricular function." c. "Treating ventricular dysrhythmias helps prevent the likelihood of stroke." d. "When ventricular contraction slows, atrial contraction is also slowed."
ANS: A After cardioversion for atrial flutter, patients may continue to need long-term therapy with either a class IC agent or a class III agent to prevent recurrence. Patients undergoing DC cardioversion need to take warfarin 3 to 4 weeks before the procedure and for several weeks afterward. Beta blockers are not indicated for postprocedural prophylaxis. Class IC and class III agents are antidysrhythmic drugs.
3. A nurse is teaching a patient who is about to undergo direct-current (DC) cardioversion to treat atrial flutter. The patient has been taking verapamil and warfarin for 6 months. Which statement by the patient indicates understanding of the teaching? a. "I may need long-term therapy with another cardiac medication after the procedure." b. "I should stop taking warfarin a few days before the procedure." c. "I will need to take a beta blocker after the procedure to prevent recurrence of atrial flutter." d. "I will not have to take antidysrhythmia medications after the procedure."
ANS: A Because antidysrhythmic drugs have prodysrhythmic actions, they can exacerbate existing dysrhythmias or generate new ones. Most adverse effects are cardiac related. There is evidence of increased mortality with many of these drugs. Use of these drugs should be limited to situations in which there is a clear benefit and only if that benefit outweighs any risks.
4. A nurse is teaching a group of nursing students about antidysrhythmic medications. Which statement by a student indicates understanding of the teaching? a. "Antidysrhythmic drugs can cause new dysrhythmias or worsen existing ones." b. "Adverse effects of these drugs are mainly noncardiac in nature." c. "For most antidysrhythmic drugs, there is evidence of reduced mortality." d. "Use of these drugs may be necessary even if the benefits are unknown."
ANS: D Quinidine widens the QRS complex by slowing depolarization of the ventricles. As cardiotoxicity develops as a result of quinidine toxicity, the QRS complex widens excessively. Any widening of the QRS complex of 50% or more warrants notifying the provider, so the nurse should withhold the medication and contact the provider. Widening of the QRS complex by more than 50% of baseline indicates cardiotoxicity. Quinidine can double digoxin levels, so it is not likely that the digoxin dose would need to be increased, and an increase in the QRS complex does not indicate a need for more digoxin. The quinidine dose should not be increased, because the findings indicate cardiotoxicity from the quinidine.
5. A patient is taking digoxin [Lanoxin] and quinidine to treat sustained ventricular tachycardia. Before giving medications, the nurse reviews the patient's electrocardiogram (ECG) and notes a QRS complex that has widened by 50% from the baseline ECG. What will the nurse do? a. Administer the medications as ordered, because this indicates improvement. b. Contact the provider to discuss reducing the digoxin dose. c. Contact the provider to request an increase in the quinidine dose. d. Withhold the quinidine and contact the provider to report the ECG finding.
ANS: B Blood dyscrasias are a rare but potentially fatal side effect of procainamide and are an indication for withdrawing the drug. Procainamide should be taken around the clock at evenly spaced intervals. Lupus-like symptoms may occur; inflammation of the joints is one manifestation and should be reported so that antinuclear antibody (ANA) titers can be monitored. Because of the risk of lupus-like symptoms and blood dyscrasias, blood tests need to be done weekly at first and then periodically thereafter.
6. A nurse provides teaching for a patient who will begin taking procainamide [Procanbid] for long-term suppression of a dysrhythmia. Which statement by the patient indicates a need for further teaching? a. "I need to take this drug at evenly spaced intervals around the clock." b. "I may have increased bruising, but this is a temporary side effect." c. "I should report pain and swelling in my joints when taking this drug." d. "I will need to have blood tests at regular intervals while taking this drug."
ANS: B This patient is showing signs that are common with high therapeutic levels of lidocaine. Because lidocaine is rapidly degraded, slowing the rate of infusion can help remove excess drug from the circulation. Seizures are possible with toxic doses; diazepam should be used to control seizures. It is not necessary to discontinue the infusion, because this patient is showing signs common to high therapeutic doses. Respiratory arrest is possible with toxic doses; mechanical ventilation may be needed.
7. A nurse is caring for a patient in the intensive care unit who is receiving intravenous lidocaine. The patient is drowsy and confused and reports numbness of the fingers and toes. Which standing order will the nurse initiate at this time? a. Administer diazepam. b. Reduce the rate of infusion. c. Discontinue the infusion. d. Prepare for mechanical ventilation.
ANS: C Mexiletine is an antidysrhythmic medication that can also cause dysrhythmias. It is used to treat the pain associated with peripheral neuropathy in diabetic patients, but it is contraindicated in diabetic patients with heart disease, and so it should be stopped now that this patient has developed a heart disorder. Because it is contraindicated, the nurse will not teach the patient about side effects with other agents. It can exacerbate cardiac symptoms, so it should not be used to treat dysrhythmias in diabetic patients. There is no indication for tests of renal and hepatic function.
8. A patient with diabetes develops ventricular tachycardia and is in the hospital for evaluation of this condition. The nurse reviews the history and learns that the patient takes mexiletine [Mexitil] for pain caused by peripheral neuropathy. What should the nurse do? a. Discuss common side effects associated with taking mexiletine with cardiac agents. b. Understand that this drug will help with both peripheral neuropathy and dysrhythmias. c. Notify the provider to request that another drug be used for peripheral neuropathy pain. d. Request an order for renal function and hepatic function tests.
ANS: A Propranolol is contraindicated in patients with asthma, because it is a nonselective beta-adrenergic antagonist and can cause bronchoconstriction and exacerbate asthma. It is used to treat tachyarrhythmias and paroxysmal atrial tachycardia evoked by emotion, so it is not contraindicated for patients with these conditions. It lowers blood pressure, so it would be helpful in patients with hypertension.
9. A prescriber has ordered propranolol [Inderal] for a patient with recurrent ventricular tachycardia. The nurse preparing to administer this drug will be concerned about what in the patient's history? a. Asthma b. Exercise-induced tachyarrhythmias c. Hypertension d. Paroxysmal atrial tachycardia associated with emotion
ANS: C, E Phenytoin is an antiseizure medication used to treat digoxin-induced dysrhythmias. Because digoxin-induced dysrhythmias can be caused by hypokalemia, it is appropriate to evaluate the serum electrolyte levels. Amiodarone, diltiazem, and quinidine increase digoxin levels.
A patient is taking digoxin [Lanoxin] and develops a dysrhythmia. The nurse reports this finding to the prescriber, who will most likely order what? (Select all that apply.) a. Amiodarone b. Diltiazem c. Phenytoin [Dilantin] d. Quinidine e. Serum electrolytes
ANS: A, C, E Amiodarone has many potential toxic side effects, including pulmonary toxicity, ophthalmic effects, and thyroid toxicity, so these systems should be evaluated at baseline and periodically while the patient is taking the drug. A complete blood count is not indicated. Renal function tests are not indicated.
A patient will be taking amiodarone [Cordarone]. Which baseline tests are necessary before this medication is started? (Select all that apply.) a. Chest radiograph and pulmonary function tests b. Complete blood count with differential c. Ophthalmologic examination d. Renal function tests e. Thyroid function tests
