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Pharmacology · chapter 17 · Antidysrhythmic Drugs

Introduction to Dysrhythmias

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. Why bradycardia causes problems

    Bradycardia can occur due to the SA node incorrectly pacing too slowly or to the AV node conducting incorrectly, leading to AV block. Bradycardia can lead to problems because it decreases cardiac output, which is affected by both stroke volume and heart rate.

  2. Why tachycardia causes problems

    Tachycardia is problematic because at very high heart rates, the ventricles do not have enough time to fill with an adequate amount of blood in between contractions. Thus, the stroke volume and cardiac output are both decreased.

  3. Tachycardia and heart failure

    Tachycardia also increases the workload of the heart and can lead to a type of heart failure called tachycardia-induced cardiomyopathy.

  4. Common causes of sinus tachycardia

    Sinus tachycardia is often caused by exercise, pain, stress, anxiety, or dehydration.

  5. Atrial fibrillation on the ECG

    Because the atria are quivering because so many impulses are being formed, the individual’s ECG will show no distinguishable P waves; however, the baseline will appear wavy due to the presence of “fibrillatory” waves.

  6. Rhythm control versus rate control

    The aim of rhythm control is to cardiovert and then maintain normal sinus rhythm. Rate control is a strategy that allows the client’s rhythm to remain in atrial fibrillation but slows the rate of conduction through the AV node, thereby slowing the ventricular rate/heart rate.

  7. Atrial flutter on the ECG

    As in atrial fibrillation, there are no typical P waves on the ECG of a client with atrial flutter. Instead, there are “flutter waves” in a characteristic sawtooth pattern between QRS complexes.

  8. Sustained ventricular tachycardia

    Sustained ventricular tachycardia (lasting more than 30 seconds) can be serious and cause hemodynamic compromise necessitating advanced cardiac life support.

  9. Causes of ventricular tachycardia

    Ventricular tachycardia can occur due to abnormalities of electrolytes such as magnesium or potassium or to myocardial ischemia (oxygen deprivation in the heart muscle). It can devolve into ventricular fibrillation, described next.

  10. Torsade de pointes and the QT

    Torsade de pointes is a dangerous ventricular tachycardia associated with medications that prolong the QT interval (the time it takes the heart to contract and recover).

  11. Pulseless electrical activity

    In pulseless electrical activity (PEA), the client’s ECG shows electrical activity (possibly even sinus rhythm); however, it does not lead to ventricular contraction, and the client does not have a pulse.

  12. Lifestyle triggers of dysrhythmias

    Some lifestyle-related triggers of dysrhythmias include anger, physical activity and exercise, alcohol, caffeine, lack of sleep, and use of illicit stimulant drugs such as cocaine (Groh et al., 2019; National Heart, Lung, and Blood Institute, 2022).

  13. Antidysrhythmics are high-alert drugs

    It is noteworthy that the Institute for Safe Medication Practices considers the majority of antidysrhythmic drugs discussed in this chapter to be high-alert drugs due to their propensity for causing client harm when administered incorrectly.

  14. Older adults: hypotension and falls

    For example, beta-adrenergic blockers, quinidine, and procainamide can exacerbate the postural hypotension that is particularly prevalent in older adults, leading to falls.

Terms to know

Chemical cardioversion
When cardioversion is accomplished via drug administration, may be referred to as chemical cardioversion.
Atrial fibrillation
Atrial fibrillation is described as an irregularly irregular rhythm in which multiple areas of the atria generate spontaneous impulses such that the atria quiver at 400–600 beats per minute.
Premature ventricular contraction (PVC)
A premature ventricular contraction (PVC) represents the ventricle contracting earlier than it should during the cardiac cycle due to a spontaneous impulse from the Purkinje fibers (rather than from an impulse carried from the SA node).
Vagal maneuvers
Vagal maneuvers are physical manipulations that can increase parasympathetic activation to treat various arrhythmias.
Valsalva maneuver
The Valsalva maneuver is commonly referred to as “bearing down” and is the process of forced expiration against a closed glottis (Niehues Klovenski, 2022).
Off-label prescription drug use
Off-label prescription drug use means that the drug may not be specifically approved for a particular client or diagnosis, but health care providers may choose to use the drug anyway because the potential benefit outweighs the potential risks.

Practice questions

Stuck on select-all-that-apply? How to take them one option at a time.

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Every question here, with the answer

  1. A client's ECG shows an irregularly irregular rhythm with no distinguishable P waves and a wavy baseline. Which dysrhythmia does the nurse recognise?

    1. Atrial flutter
    2. Sinus tachycardia
    3. Atrial fibrillation
    4. Asystole

    Answer: Atrial fibrillation

    Atrial fibrillation is irregularly irregular, with no distinguishable P waves and a wavy baseline from fibrillatory waves. Atrial flutter shows sawtooth flutter waves, sinus tachycardia has a P wave before each QRS, and asystole has no waveforms.

  2. The monitor shows an organised rhythm, but the nurse cannot find a pulse on the client. Which condition does the nurse recognise?

    1. Sinus bradycardia
    2. Premature ventricular contraction
    3. Pulseless electrical activity
    4. Atrial fibrillation with rapid ventricular response

    Answer: Pulseless electrical activity

    In pulseless electrical activity, the ECG shows electrical activity, possibly even sinus rhythm, but there is no ventricular contraction and no pulse; it requires advanced cardiac life support. The other rhythms produce ventricular contraction and a pulse.

  3. A client with atrial fibrillation is prescribed a rate control strategy. The client asks what this means. Which response by the nurse is accurate?

    1. The goal is to convert the heart back to normal sinus rhythm.
    2. The rhythm stays in atrial fibrillation, but conduction through the AV node is slowed to lower the heart rate.
    3. The atria will stop quivering completely.
    4. The heart will be paced by the Purkinje fibers.

    Answer: The rhythm stays in atrial fibrillation, but conduction through the AV node is slowed to lower the heart rate.

    Rate control lets the rhythm remain in atrial fibrillation while slowing AV node conduction and so the heart rate. Converting back to normal sinus rhythm is the aim of rhythm control, and the other options are not described.

  4. A client with recurrent dysrhythmias asks what everyday triggers to avoid or manage. Which should the nurse include? Select all that apply.

    1. Alcohol
    2. Caffeine
    3. Drinking water
    4. Lack of sleep
    5. Cocaine use

    Answer: Alcohol, Caffeine, Lack of sleep, Cocaine use

    Lifestyle triggers of dysrhythmias include anger, exercise, alcohol, caffeine, lack of sleep and illicit stimulant drugs such as cocaine. Drinking water is not listed as a trigger.

  5. A nurse is caring for an older adult starting an antidysrhythmic drug. Which concerns are supported for this age group? Select all that apply.

    1. Antidysrhythmics need less monitoring in older adults.
    2. Decreased metabolism and excretion can raise drug plasma levels.
    3. Some antidysrhythmics can worsen postural hypotension and lead to falls.
    4. Multiple medications increase the likelihood of drug interactions.
    5. Older adults are at lower risk for dysrhythmias.

    Answer: Decreased metabolism and excretion can raise drug plasma levels., Some antidysrhythmics can worsen postural hypotension and lead to falls., Multiple medications increase the likelihood of drug interactions.

    In older adults, some antidysrhythmics worsen postural hypotension and cause falls, polypharmacy raises interaction risk, and slower metabolism and excretion raise plasma levels, so extra vigilance is needed. The risk of dysrhythmia actually rises sharply after age 60.

  6. A client's heart rate is 160 beats per minute. The client is dizzy and weak. How does the nurse explain why a very fast rate lowers cardiac output?

    1. The SA node stops firing at high rates.
    2. A fast rate increases stroke volume too much.
    3. The atria contract harder and empty completely.
    4. The ventricles do not have enough time to fill with blood between contractions.

    Answer: The ventricles do not have enough time to fill with blood between contractions.

    At very high heart rates the ventricles do not have time to fill adequately between contractions, so stroke volume and cardiac output both decrease. The other explanations are not supported by the section.

Where every quote comes from

Section 17.1 Introduction to Dysrhythmias of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.