Antiarrhythmics: Nursing pharmacology

Definitions & Key takeaways

Antiarrhythmic drugs are used to prevent and treat abnormal and irregular heart rhythms (arrhythmias). These drugs are classified into four major classes based on their physiological effect on the heart muscle.

First, there is Class I antiarrhythmics, which are sodium channel blockers. It includes drugs like quinidine and procainamide. Class I antiarrhythmics are subdivided into three smaller groups: class 1A, class 1B, and class 1C. Next comes class II antiarrhythmics which are beta-blockers. They include drugs like propranolol and esmolol. Class III antiarrhythmics consist of potassium channel blockers like amiodarone; and class IV antiarrhythmics which are calcium channel blockers, consisting of drugs like verapamil and diltiazem.

Chapters:

Watch video only

Introduction0:00–0:17

Antiarrhythmics, also called antidysrhythmics, are a class of medications that help control arrhythmias or abnormal heartbeats, such as supraventricular tachycardia, ventricular tachycardia and ventricular fibrillation.In general, antiarrhythmics act by altering electrical conduction pathways through the heart, and can be administered orally, intravenously, or intramuscularly.

Mechanism of action0:17–2:11

Now, based on their mechanism of action, they can be divided into four main classes. Class I antiarrhythmics are sodium channel blockers that inhibit sodium influx into cardiac cells, and can be further subdivided into three groups depending on how they affect conduction and repolarization.
Class IA antiarrhythmics, such as quinidine and procainamide, act by slowing conduction and prolonging repolarization. Class IB, like lidocaine and mexiletine, also act by slowing conduction, but they shorten repolarization.
And class IC, such as flecainide and propafenone, prolong conduction but have no effect on repolarization. Next, class II antiarrhythmics are beta-blocker medications, and include propranolol, esmolol, sotalol, and acebutolol.
These medications act by preventing the catecholamines norepinephrine and epinephrine from binding and activating them; ultimately decreasing heart contractility and slowing the conduction through the atrioventricular or AV node.
Moving onto class III antiarrhythmics, these are potassium channel blockers. The most important drug in this class is amiodarone, which acts by inhibiting potassium efflux from cardiac cells, ultimately prolonging repolarization and action potential duration.
Finally, class IV antiarrhythmics are calcium channel blockers, and include verapamil and diltiazem. These medications block calcium influx into cardiac cells, which ultimately helps decrease heart contractility and slow conduction velocity.
Unfortunately, antiarrhythmics can have several side effects. First of all, they can surprisingly cause arrhythmias!

Side Effects2:11–4:27

Additionally, they can cause bradycardia and hypotension as well as gastrointestinal disturbances, like nausea and vomiting.
Diving deeper into each class, class I antiarrhythmics, or sodium channel blockers, may cause hepatotoxicity. Quinidine can cause additional side effects like angioedema, and hematologic side effects like thrombocytopenia, agranulocytosis, and anemia, as well as cinchonism, which involves symptoms like tinnitus, vertigo, headaches, and visual changes.
Procainamide has a boxed warning for agranulocytosis and medication-induced systemic lupus erythematosus, and mexiletine has a boxed warning for acute liver injury.
Additionally, flecainide in particular has a boxed warning for ventricular proarrhythmic effects in clients with atrial fibrillation or atrial flutter.
On the other hand, class II antiarrhythmics, or beta blockers, can cause dizziness, fatigue, and bronchospasm, since they also block beta receptors that are in the lungs.
In addition, beta blockers have shown to cause certain metabolic changes like hyperglycemia, hypertriglyceridemia, and hyperkalemia; while clients with diabetes may experience hypoglycemia unawareness.
Finally, sotalol has a boxed warning for life-threatening proarrhythmia. Now, class III antiarrhythmics, or potassium channel blockers, can cause neurological side effects, and amiodarone in particular can cause thyroid problems, and a bluish skin discoloration, as well as skin rash and pruritus, and even toxic epidermal necrolysis.
In addition, amiodarone has a boxed warning for cardiac arrhythmias, pulmonary toxicity, and hepatotoxicity. Finally, class IV antiarrhythmics, or calcium channel blockers, can cause hyperprolactinemia, constipation, and peripheral edema.
As far as contraindications go, all antiarrhythmics should not be used in clients with pre-existing hypotension, heart failure, bradycardia, heart block, and torsade de pointes.

Contraindications4:27–6:20

In addition, antiarrhythmics should be used cautiously during pregnancy and breastfeeding, in children and elderly clients, as well as in clients with hepatic or renal disease.
Class IA antiarrhythmics in particular are contraindicated in clients with thrombocytopenia or thrombocytopenic purpura.
These medications should also be avoided in clients experiencing heart block that’s greater than first degree; as well as in those with idioventricular conduction delays who don’t have a functioning artificial pacemaker.
Other contraindications for class IA antiarrhythmics include myasthenia gravis, as well as clients adversely affected by anticholinergic medications, and those taking certain quinolone antibiotics that can prolong the QT interval.
On the other hand, the class IB antiarrhythmic lidocaine is contraindicated in clients with heart conditions like Adam-Stokes syndrome and Wolff-Parkinson-White syndrome, as well as severe degrees of heart block who don’t have a functioning artificial pacemaker.
Finally, lidocaine should be avoided in clients with corn allergy, as its premixed injection may contain corn-derived dextrose.
Next, beta blockers should be used with caution in clients with asthma and chronic obstructive pulmonary disease, or COPD, due to their bronchoconstrictive effect, as well as in clients with diabetes due to their hyperglycemic effect.
Finally, clients on potassium or calcium channel blockers must avoid consuming grapefruit, as their interaction can result in toxicity.
All right, if your client is prescribed an antiarrhythmic, start by assessing their vital signs and performing a baseline assessment, noting symptoms of arrhythmia like shortness of breath, palpitations, or chest pain.

Nursing considerations & Client Education6:20–11:18

Next, review their laboratory test results, including CBC, electrolytes, cardiac enzymes and troponins, as well as renal and liver function tests.
Lastly, review their ECG test results.Next, explain to your client how the antiarrhythmic medication will help restore normal cardiac rhythm, and that they will need to be monitored closely during treatment.
If your client will be self-administering their antiarrhythmic, emphasize the importance of taking it as prescribed and to not stop taking it abruptly.
Teach your client how to take their pulse and blood pressure at home, and be sure they understand which readings warrant a call to their healthcare provider.
Then, advise your client to avoid consuming alcohol, since this could worsen hypotension, as well as caffeine and tobacco products, since these can increase their blood pressure and heart rate.
Also, explain the need to avoid over the counter products unless approved by their healthcare provider. Now, if your client is prescribed quinidine, instruct them to take their medication with meals.
Then, teach them about important dietary modifications they will need to incorporate while taking this medication. Let them know that they should avoid consuming grapefruit or drinking grapefruit juice, as well as consuming large amounts of foods that alkalize urine, such as dairy or vegetables, as these could increase the blood concentration of their medication, which may lead to serious arrhythmias like heart block.
In addition, instruct them to avoid large amounts of fruit juice or vitamin C, as these can make urine more acidic, which will increase the elimination of quinidine and decrease its blood concentration.
Lastly, remind them to follow a low sodium diet and avoid large daily variations in salt intake.Next, explain to your client that they may experience some common side effects while taking quinidine, such as hypotension, and encourage them to change positions slowly to offset the effects of orthostatic hypotension.
Also, teach your client to recognize symptoms of quinidine toxicity, such as tinnitus, vertigo, headaches, and visual changes, and if any of these occur, prompt them to notify their healthcare provider right away.
Okay, when administering an antiarrhythmic like amiodarone, be sure emergency equipment is readily available, ensure your client is on continuous ECG monitoring, correct any existing electrolyte imbalances, ensure correct IV catheter placement, and check your IV tubing for an in-line 2 micron filter.
Then, administer a medication bolus and titrate the maintenance infusion per your facility’s protocol, titrating the infusion based on the client’s condition and response to the medication.
During administration, monitor your client's ECG, vital signs, and fluid intake and output, and watch closely for the development of arrhythmias, such as AV block and sinus bradycardia.Now, if your client is discharged home on oral amiodarone, be sure to obtain baseline chest X-ray, thyroid function tests, potassium and magnesium blood levels, and liver function tests as ordered.
Also, schedule an ophthalmic examination to establish baseline vision function. Then, instruct your client to take their medication once daily, with or without food, at the same time each day.
Be sure they know to avoid grapefruit or grapefruit juice during therapy, as it will increase the effect of amiodarone. Next, let your client know about possible side effects that should be reported immediately to their healthcare provider, including symptoms of pulmonary toxicity like shortness of breath, cough, or chest pain; symptoms of cardiac toxicity like fatigue, exercise intolerance, and palpitations; and ophthalmic symptoms like changes in visual acuity or decreased peripheral vision.
Also, teach your client that photosensitivity is an important side effect of amiodarone, and encourage them to always use sunscreen and wear protective clothing when spending time outdoors, and avoid tanning beds or sunlamps.
Lastly, emphasize the importance of regular appointments for cardiac monitoring, chest X-ray and pulmonary function, measurement of thyroid hormone levels, as well as periodic ophthalmic examinations.Finally, when caring for a client taking an antiarrhythmic medication, keep a close eye out for side effects, including the development of arrhythmias, and monitor for the desired therapeutic effect of ECG stabilization.All right, as a quick recap… Antiarrhythmics help control arrhythmias, which are abnormal heartbeats.

Review11:18–12:48

There are four classes of antiarrhythmics that work in different ways to restore normal cardiac rhythm. Class I antiarrhythmics are sodium channel blockers and are subdivided into three groups, class 1A, class 1B, and class 1C, depending on how they impact conduction and repolarization.
Class II antiarrhythmics are beta-blockers, which work by decreasing contractility and slowing AV node conduction. Next, class III antiarrhythmics are potassium channel blockers that prolong repolarization and action potential duration.
And lastly, class IV antiarrhythmics are calcium channel blockers, which decrease contractility and slow conduction velocity.
Antiarrhythmics have many side effects, including arrhythmias, bradycardia, and hypotension. Contraindications to keep in mind when administering antiarrhythmics include hypotension, heart failure, bradycardia, heart block, and torsade de pointes.
Nursing considerations for antiarrhythmics involve performing a focused assessment before initiating therapy, as well as frequent assessments during therapy to watch for side effects and monitor the effectiveness of therapy.
Client teaching is focused on the purpose of the medication, safe self-administration, dietary modifications, and learning to recognize side effects
Antiarrhythmics: Video, Causes, and Symptoms | Osmosis