Bradycardia is a condition in which the heart beats slower than normal, typically below 60 beats per minute. While it can occur naturally in healthy individuals, such as athletes, it may also signal serious underlying problems with the heart or other body systems.
For respiratory therapists, understanding bradycardia is important because it is often associated with issues related to oxygenation, ventilation, or the effects of certain medications. This article explains what bradycardia is, why it matters, and its relevance in respiratory care.
What is Bradycardia?
Bradycardia is a cardiac rhythm characterized by a slower-than-normal heart rate. In adults, it is typically defined as a resting heart rate below 60 beats per minute (bpm). While some individuals, such as well-trained athletes, may naturally have a slower heart rate without health consequences, bradycardia can also signal an underlying problem with the heart’s electrical conduction system.
The condition may arise from intrinsic cardiac issues (such as sinus node dysfunction or heart block) or secondary causes, including medication effects, electrolyte imbalances, hypoxia, or increased intracranial pressure. Depending on the cause and severity, bradycardia can range from asymptomatic to life-threatening.
Signs and Symptoms
- Dizziness or lightheadedness
- Fatigue or weakness
- Shortness of breath
- Chest pain
- Syncope (fainting)
- Confusion or altered mental status
Note: In severe cases, bradycardia can progress to hypotension, shock, or cardiac arrest.
Why is Bradycardia Relevant to Respiratory Therapists?
Respiratory therapists are often at the bedside in acute and critical care settings, where continuous monitoring of heart rate, rhythm, and oxygenation is essential. Bradycardia is directly relevant to respiratory care for several reasons:
1. Impact of Hypoxemia on Heart Rhythm
Hypoxemia is a common cause of bradycardia, especially in neonates and pediatric patients. For respiratory therapists, this means that effective airway management, oxygen therapy, and ventilation support can be life-saving interventions when bradycardia is linked to inadequate oxygen delivery.
2. Association with Mechanical Ventilation
Patients receiving mechanical ventilation may develop bradycardia during procedures such as suctioning, intubation, or extubation due to vagal stimulation. Understanding this reflex response allows respiratory therapists to anticipate, recognize, and respond quickly to prevent complications.
3. Cardiac Monitoring in Emergencies
In resuscitation and advanced life support, respiratory therapists play a critical role in airway management and ventilatory support. Recognizing bradycardia on the monitor and knowing its potential causes (e.g., acidosis, medication effects) is essential in guiding rapid interventions alongside the medical team.
4. Medication Effects
Many drugs used in respiratory care, such as sedatives, opioids, or beta-blockers, administered in critical care, can depress cardiac function and cause bradycardia. Respiratory therapists must remain vigilant when managing patients under these therapies.
Clinical Relevance in Respiratory Care
Bradycardia is a vital sign that carries significant meaning in many areas of respiratory care. Understanding its clinical relevance helps respiratory therapists identify underlying problems quickly and respond with the appropriate intervention.
Here are some of the most important settings where bradycardia plays a key role:
- Neonatal Resuscitation: Bradycardia in newborns is often the first sign of inadequate ventilation. RTs must initiate positive pressure ventilation immediately to reverse hypoxemia and restore normal heart rate.
- Critical Care: In adult and pediatric ICUs, bradycardia may indicate worsening oxygenation or complications from procedures.
- Transport and Emergency Settings: RTs supporting patients during transfers or emergencies must monitor for bradycardia as an early warning sign of clinical deterioration.
Note: By recognizing bradycardia in these different clinical situations, respiratory therapists can take timely action to stabilize patients and prevent further complications.
Bradycardia Practice Questions
1. What is the medical term for a heart rate slower than 60 beats per minute?
Bradycardia
2. Which thyroid-related condition is a known cause of bradycardia due to insufficient hormone production?
Hypothyroidism
3. In adults, bradycardia is typically defined as a resting heart rate below how many beats per minute?
60 bpm
4. What type of individuals may naturally have a slower heart rate without experiencing any health issues?
Well-trained athletes
5. What part of the heart’s system is often involved when bradycardia is caused by intrinsic cardiac problems?
The electrical conduction system
6. Sinus node dysfunction and heart block are examples of what type of causes of bradycardia?
Intrinsic cardiac causes
7. Which of the following are secondary causes of bradycardia?
Medication effects, electrolyte imbalances, hypoxia, increased intracranial pressure
8. What can the severity of bradycardia range from?
Asymptomatic to life-threatening
9. Which hormone gives the heart an “energy boost” to increase its rate, and its deficiency can cause bradycardia?
Thyroid hormone
10. What cardiovascular condition can trigger a reflex bradycardia in response to elevated blood pressure?
Hypertension
11. What is the term for the reflex that slows the heart in response to high blood pressure?
Reflex bradycardia
12. Which medication is classified as a positive chronotropic agent used to treat bradycardia?
Atropine
13. Which other agents may be used if atropine is ineffective in managing bradycardia?
Epinephrine and dopamine
14. What should be performed immediately if a patient with bradycardia has no pulse?
CPR (Cardiopulmonary resuscitation)
15. What ECG finding helps identify bradycardia in adults?
Heart rate less than 60 beats/min with regular rhythm and normal PR interval
16. What is considered a prolonged R-R interval on an ECG?
Greater than 1 second
17. In bradycardia, what should you expect to see regarding the P waves and QRS complexes?
Normal P waves followed by regular QRS complexes
18. What are the clinical interventions for bradycardia caused by hypothermia?
Provide warm blankets and fluids
19. Which diagnostic tools should be used to evaluate bradycardia related to cardiac issues?
ECG and cardiac enzymes
20. What is sick sinus syndrome, and how is it related to bradycardia?
A dysfunction of the heart’s natural pacemaker that can cause bradycardia
21. Which serious cardiac condition may result in bradycardia during or after the event?
Myocardial infarction
22. What type of apnea monitoring is useful in neonates with recurrent episodes of bradycardia?
Cardiorespiratory apnea monitoring
23. What is one reason bradycardia in neonates must be taken seriously?
It can be associated with life-threatening oxygen desaturation
24. Name at least four potential causes of bradycardia.
Hypothyroidism, sick sinus syndrome, myocardial infarction, hypertension
25. Bradycardia may lead to death if associated with which additional conditions?
Infection, electrolyte disorders, and medication side effects
26. At what heart rate do signs and symptoms of pathologic bradycardia typically begin to appear?
Below 50 beats per minute
27. What are some of the important signs of pathologic bradycardia?
Fainting (syncope), dizziness, fatigue, and shortness of breath
28. What is another medical term for fainting?
Syncope
29. What diagnostic tool is used to plot the electrical activity of the heart in waveform patterns?
Electrocardiogram (ECG)
30. What is the first step in treating bradycardia?
Addressing the underlying cause
31. Which underlying issues may need to be corrected in the treatment of bradycardia?
Hypothyroidism and electrolyte imbalances (e.g., hyperkalemia)
32. In cases where medication and lifestyle adjustments are ineffective, what device may be used to regulate heart rate?
Pacemaker
33. What is sinus bradycardia?
A rhythm in which impulses from the SA node occur at a slower-than-normal rate
34. What is the defining characteristic of sinus bradycardia in terms of heart rate?
A sinus rhythm with a heart rate below 60 beats per minute
35. If a patient’s heart rate is measured to be less than 50 bpm, what condition do they most likely have?
Bradycardia
36. What may result if a patient with tachycardia is given an excessive dose of beta blockers?
Bradycardia
37. What medications may be used to treat sinus bradycardia under 60 bpm?
Atropine and isoproterenol
38. Which medication class should be withheld if it contributes to bradycardia?
Beta blockers
39. What is a non-pharmacological intervention used in persistent or severe bradycardia?
Pacemaker therapy
40. Which maneuvers may trigger bradycardia by stimulating the vagus nerve?
Carotid sinus massage and Valsalva maneuver
41. What conditions may cause asymptomatic bradycardia?
Hypothermia, hypothyroidism, and athletic conditioning
42. What are the three criteria for symptomatic bradycardia?
Slow heart rate, presence of symptoms, and symptoms caused by the slow heart rate
43. What heart rate is commonly associated with symptomatic bradycardia?
Less than 50 beats per minute
44. What are some symptoms associated with symptomatic bradycardia?
Syncope, chest pain, pale cool skin, weakness, angina, dizziness, confusion, shortness of breath
45. What type of bradycardia may be considered normal in healthy individuals such as athletes?
Asymptomatic bradycardia
46. What are the rhythm types commonly associated with bradycardia?
Sinus bradycardia, First-degree AV block, Second-degree AV block (Type I and II), and Third-degree AV block
47. What are the two goals when assessing a patient with bradycardia?
Primary: Recognize symptomatic bradycardia; Secondary: Identify the type of AV block
48. What is the definition of symptomatic bradycardia according to ACLS guidelines?
A heart rate under 60 bpm that produces symptoms due to the slow rate
49. What symptom of symptomatic bradycardia can affect a patient’s mental status?
Confusion and disorientation
50. Which common cardiovascular emergency may be caused by bradycardia if not treated?
Cardiopulmonary arrest
51. Which drugs are used in the treatment of symptomatic bradycardia?
Atropine, dopamine (infusion), and epinephrine (infusion)
52. What is the definition of bradycardia or bradyarrhythmia?
Any rhythm disorder with a heart rate less than 60 beats per minute
53. What defines symptomatic bradyarrhythmia?
It is bradycardia that causes signs and symptoms due to the slow heart rate
54. What are the three criteria that define symptomatic bradycardia?
The heart rate is slow, the patient has symptoms, and the symptoms are caused by the slow heart rate.
55. What are common symptoms of bradycardia?
Chest pain, shortness of breath, dizziness, fatigue, weakness, syncope, or presyncope
56. What are physical signs that may indicate bradycardia?
Hypotension, diaphoresis, pulmonary congestion, bradycardia-induced PVCs or VT, and postural blood pressure drop
57. What is the recommended IV dose of atropine for bradycardia?
0.5 mg bolus every 3–5 minutes, up to a total dose of 3 mg
58. What is the recommended dopamine infusion dose for bradycardia?
2–20 mcg/kg per minute, titrated to the patient’s response
59. What is the recommended epinephrine infusion dose for bradycardia?
2–10 mcg per minute, titrated to the patient’s response
60. What is the first step in evaluating a patient with bradycardia?
Determine if the heart rate is <50 bpm and assess if it is inadequate for the patient’s condition
61. What are the ABCD steps for treating bradycardia?
A: Maintain a patent airway, B: Assist breathing and give oxygen if hypoxemic, C: Monitor heart rate and BP, obtain a 12-lead ECG, and establish IV access, and D: Perform focused assessment and treat contributing causes.
62. What is the key clinical question in a bradycardia case?
Is the bradycardia causing the symptoms, or is another condition causing both the symptoms and the bradycardia?
63. What is the next step if a patient has poor perfusion due to bradycardia?
Administer atropine 0.5 mg IV, repeat every 3–5 minutes up to 3 mg
64. What should you do if atropine is ineffective in treating bradycardia with poor perfusion?
Use transcutaneous pacing or initiate dopamine or epinephrine infusion
65. Why is atropine not recommended for certain AV blocks (e.g., second-degree Type II or third-degree with wide QRS)?
These rhythms are often infranodal and unresponsive to atropine; pacing or beta-adrenergic support is preferred
66. In the absence of a reversible cause, what is the first-line drug for bradycardia?
Atropine
67. How does atropine work in the treatment of bradycardia?
It blocks vagal effects, increasing heart rate and AV node conduction
68. What alternatives to transcutaneous pacing (TCP) may temporarily stabilize a bradycardic patient?
Epinephrine or dopamine infusions
69. What is the maximum total dose of atropine for bradycardia?
0.5 mg IV every 3–5 minutes, up to a total of 3 mg or 0.4 mg/kg
70. What may occur if a dose of atropine less than 0.5 mg is given?
It may paradoxically worsen bradycardia
71. In which clinical scenario should atropine be used cautiously in the treatment of bradycardia?
In patients with acute coronary ischemia or myocardial infarction, as increased heart rate may worsen ischemia or infarct size
72. When should healthcare providers consider immediate pacing in a bradycardic patient?
In unstable patients with high-degree AV block when IV access is unavailable
73. How should the rate for transcutaneous pacing (TCP) be determined?
Set the rate to the lowest effective value based on patient symptoms and clinical response, minimizing myocardial oxygen demand
74. When might TCP be ineffective even if electrical capture is achieved?
When the patient’s symptoms are not caused by bradycardia
75. Why is transvenous pacing often preferred over TCP?
Because TCP can be painful and unreliable, it is used as a temporary bridge until transvenous pacing is established
76. What should be done if transcutaneous pacing is ineffective or has inconsistent capture?
Start a dopamine or epinephrine infusion and prepare for transvenous pacing with expert consultation
77. What medications are commonly used to improve patient comfort and effectiveness during pacing?
Parenteral benzodiazepines for anxiety, narcotics for pain, and chronotropic infusions if available
78. Why must a patient’s fluid status be assessed before using epinephrine or dopamine?
Because these drugs are vasoconstrictors and can worsen hypoperfusion if the patient is hypovolemic
79. What effects does dopamine have at lower doses?
Primarily increases heart rate and contractility with limited vasoconstrictive effects
80. What is the primary decision point in the ACLS bradycardia algorithm?
Determining whether the patient has signs of adequate or poor perfusion
81. What should be done if a bradycardic patient is asymptomatic with stable perfusion?
Monitor the patient and search for reversible causes; no immediate pharmacologic treatment is necessary
82. What should be done if a bradycardic patient is symptomatic with poor perfusion?
Administer atropine, and if ineffective, initiate pacing or start dopamine/epinephrine infusion
83. What is the most reliable sign that transcutaneous pacing is capturing the heart effectively?
A corresponding pulse with electrical spikes and QRS complexes on the ECG
84. What is the major limitation of transcutaneous pacing in conscious patients?
It is often painful due to skeletal muscle contraction during pacing.
85. What should be documented after starting pacing in a bradycardic patient?
Capture confirmation, pacing rate, output settings, and the patient’s response
86. What is the mechanism of action of dopamine in bradycardia management?
It stimulates beta-1 receptors to increase heart rate and myocardial contractility.
87. When is epinephrine preferred over dopamine in bradycardia treatment?
When more potent beta-1 and alpha stimulation is needed or in severe hypotension
88. What is the key goal when using pharmacologic or pacing interventions for bradycardia?
To restore adequate perfusion and resolve symptoms related to the slow heart rate
89. What are some reversible causes of bradycardia that should be ruled out?
Hypoxia, hypothermia, drug overdose (e.g., beta-blockers), electrolyte imbalance, and myocardial infarction
90. What is the recommended approach for bradycardia caused by beta-blocker toxicity?
Administer glucagon or consider high-dose insulin therapy under expert guidance.
91. What common mistake should be avoided when treating bradycardia?
Delaying treatment in a symptomatic patient while waiting for a full diagnosis
92. What is the advantage of using a 12-lead ECG in bradycardia evaluation?
It helps identify the underlying rhythm and potential causes, like AV block or myocardial infarction.
93. What does a widened QRS complex in bradycardia suggest?
A possible infranodal conduction block, which may require pacing rather than atropine.
94. What is a common cause of sinus bradycardia in athletes?
Increased vagal tone due to enhanced parasympathetic activity
95. What effect does hypothyroidism have on heart rate?
It can lead to sinus bradycardia due to reduced metabolic demand and impaired autonomic function.
96. What is the best indicator that bradycardia is pathologic and not physiologic?
Presence of symptoms such as syncope, dizziness, or hypotension
97. Why might atropine be ineffective in high-degree AV block?
Because it does not affect infranodal conduction tissues, which are often involved in advanced blocks.
98. What is an example of a vagal maneuver that may induce bradycardia?
Carotid sinus massage or Valsalva maneuver
99. What type of AV block typically does not require pacing if the patient is asymptomatic?
First-degree AV block or Mobitz Type I (Wenckebach)
100. What is the ultimate goal of all bradycardia treatment algorithms?
To ensure adequate cardiac output and perfusion while treating underlying causes.
Final Thoughts
Bradycardia is not simply a slow heartbeat but a clinical sign that can reveal serious problems affecting both the heart and the lungs. For respiratory therapists, recognizing bradycardia and understanding its causes is vital to providing safe and effective care.
Whether it appears during neonatal resuscitation, mechanical ventilation, or critical care monitoring, timely recognition and intervention can prevent further complications and improve patient outcomes.
By staying alert to this condition, respiratory therapists play a key role in protecting patient safety and supporting overall cardiovascular and respiratory health.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Sidhu S, Marine JE. Evaluating and managing bradycardia. Trends Cardiovasc Med. 2020.