Antidysrhythmic Drugs Flashcards
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
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.
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.”
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.
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.”
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.
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.”
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.
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.
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.
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.”
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. Lupuslike 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 lupuslike symptoms and blood dyscrasias, blood tests need to be done weekly at first and then periodically thereafter.
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.
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.
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 does 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.
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 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.
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
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.
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 sun block 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.”
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 sun block 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.
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
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.
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
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.
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
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.
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.”
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
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.
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.
