Table of Contents

 

1. Abstract
2. Case Presentation
3. Introduction
4. Critical Appraisal Of The Literature
5. Pathophysiology And Rhythm Analysis
   1. Sinus Node Dysfunction
   2. Atrioventricular Blocks
6. Etiology And Differential Diagnosis
   1. Ischemia- And Infarction-Related Causes
   2. Neurocardiogenic (Reflex-Mediated) Causes
   3. Metabolic, Endocrine, And Environmental Causes
7. Prehospital Care
8. Emergency Department Evaluation
   1. The Basics
   2. Focused History
   3. Physical Examination
9. Diagnostic Studies
   1. The Electrocardiogram
   2. Laboratory Studies
   3. Imaging Modalities
10. Treatment
    1. The Unstable Patient
       1. Technique For Transcutaneous Pacing
       2. Technique For Transvenous Pacing
       3. Goals Of Treatment For Unstable Patients
    2. The Stable Patient
    3. Drug Toxicity
11. Disposition
12. Summary
13. Risk Management Pitfalls For Bradydysrhythmias In The Emergency Department
14. Time- And Cost-Effective Strategies
15. Risk Management Pitfalls For Bradydysrhythmias In The Emergency Department
16. Case Conclusion
17. Clinical Pathway For Adult Bradycardia (With Pulse)
18. Tables and Figures
    1. Table 1. Categories Of Bradydysrhythmias
    2. Table 2. Differential Diagnosis For Bradydysrhythmias
    3. Table 3. Assessing The History Of The Patient With Bradydysrhythmia
    4. Table 4. American Heart Association Classification Of Recommendations
    5. Table 5. Specific Antidotes And Therapies For Toxicological Causes Of Bradydysrhythmias
    6. Figure 1. Sinus Bradycardia Electrocardiogram Tracing
    7. Figure 2. Sinus Arrest Electrocardiogram Tracing
    8. Figure 3. Tachy-Brady Syndrome Electrocardiogram Tracing
    9. Figure 4. First-Degree Atrioventricular Block Electrocardiogram Tracing
    10. Figure 5. Second-Degree Atrioventricular Block, Mobitz Type I, Wenckebach Electrocardiogram Tracing
    11. Figure 6. Second-Degree Atrioventricular Block, Mobitz Type II Electrocardiogram Tracing
    12. Figure 7. Third-Degree Atrioventricular Block, Complete Heart Block Electrocardiogram Tracing
    13. Figure 8. Osborn Waves Electrocardiogram Tracing
    14. Figure 9. Link For Demonstration Video Of Transcutaneous Pacing
    15. Figure 10. Link For Demonstration Video Of Transvenous Pacing
19. References

Abstract

Bradydysrhythmias represent a collection of cardiac conduction abnormalities that span the spectrum of emergency presentations, from relatively benign conditions to conditions that represent serious, life-threatening emergencies. This review presents the electrocardiographic findings seen in common bradydysrhythmias and emphasizes prompt recognition of these patterns. Underlying etiologies that may accompany these conduction abnormalities are discussed, including bradydysrhythmias that are reflex mediated (including trauma induced) and those with metabolic, environmental, infectious, and toxicologic causes. Evidence regarding the management of bradydysrhythmias in the emergency department is limited; however, there are data to guide the approach to the unstable bradycardic patient. When decreased end-organ perfusion is present, the use of atropine, beta agonists, and transcutaneous or transvenous pacing may be required.

Key words: bradydysrhythmia, sinus bradycardia, tachy-brady syndrome, heart block, atrioventricular block, sinoatrial block reflex-mediated bradycardia, relative bradycardia

Case Presentation

It is about 20 minutes into your shift when EMS arrives with a pleasant 80-year-old woman who has had a syncopal event. She describes standing in her home earlier today and becoming lightheaded and falling to the ground. She is now resting comfortably, and her vital signs are: blood pressure, 140/72 mm Hg; pulse rate, 74 beats/min; respiratory rate, 14 breaths/min; and oxygen saturation, 99% on room air. You have just begun to take her history when you are interrupted and called to your next patient...

You approach the bedside of a 27-year-old woman who is pale, diaphoretic, and writhing in pain. The only history you are able to obtain is that she has had mild lower abdominal pain for a few days that acutely worsened today. Initial vital signs are: blood pressure, 70/40 mm Hg; pulse rate, 58 beats/min; respiratory rate, 20 breaths/min; and oxygen saturation, 99% on room air. Your brief exam is significant for diffuse abdominal tenderness and guarding. You then hear a flurry of activity from the hallway...

Your next patient is being rushed down the hall on a stretcher. Brought in by a family member for intermittent lightheadedness and shortness of breath, this 64-year-old man is pale and diaphoretic, with depressed mental status. A quick check of his radial artery demonstrates a weak pulse with a palpable rate of approximately 40 beats/min. You quickly place him on the cardiac monitor and notice what appears to be a third-degree heart block. Initial vitals are: blood pressure, 82/40 mm Hg; pulse rate, 38 beats/ min; respiratory rate, 18 breaths/min; and oxygen saturation, 98% on room air.

These 3 cases represent some of the variable presentations of patients with bradydysrhythmias. The underlying pathology for these patients ranges from the benign to the life threatening. You approach each case in a systematic manner, knowing that prompt evaluation, recognition, and treatment can make the difference.

Introduction

During the course of practice, all emergency clinicians will be faced with evaluating and managing patients with bradydysrhythmias. These disorders result from a wide range of underlying pathologies that must all be considered in the evaluation of patients who present to the emergency department (ED) with bradydysrhythmias. Assessments will be focused on identifying cardiovascular etiologies, but the thorough evaluation should not overlook traumatic, intracranial, and intra-abdominal processes. Prompt electrocardiogram (ECG) analysis often represents a key point of the emergent evaluation, and familiarity with ECG patterns is critical to clinical decision-making.

There is always the risk that patients with bradydysrhythmias will be hemodynamically unstable upon arrival or that they will become unstable during the course of their evaluation and treatment. While these scenarios may not occur on a regular basis, emergency clinicians must be prepared to provide emergent interventions, as needed, to stabilize these patients. Familiarity with resuscitation techniques and medications as well as procedures (including transvenous pacer placement) is central to management. This issue of Emergency Medicine Practice provides a systematic review of the literature on bradydysrhythmias and presents recommendations based on the best available evidence.

Critical Appraisal Of The Literature

A review of the literature on bradydysrhythmias proved to be challenging due to the vast number of articles mentioning relevant terms. The review was initially performed through PubMed and Ovid MEDLINE®, using the keywords bradydysrhythmias, sinus bradycardia, sick sinus syndrome, tachy-brady syndrome, sinoatrial block, sinus arrest, first-degree heart block, second-degree heart block, Mobitz type I, Mobitz type II, Wenckebach, third-degree heart block, complete heart block, complete AV block, reflex-mediated bradycardia, relative bradycardia, and paroxysmal bradycardia. While several hundred randomized controlled trials were initially identified, most involved long-term pacemaker implantation for patients with known cardiac dysfunction. Very few large trials involving the treatment of bradydysrhythmias in the emergency setting could be identified.

The Cochrane Database of Systematic Reviews was searched for entries regarding arrhythmias, and a single review was found that investigated the long-term use of medications and pacemakers for reflex-mediated syncope, although the data were insufficient to produce a firm conclusion. The consensus guidelines, recommendations, and algorithms that have been developed were adapted primarily from statements by the American College of Emergency Physicians, the American College of Cardiology, and the American Heart Association, as published by the National Guideline Clearinghouse (www.guideline.gov). Overall, the literature is sparse regarding high-quality studies for the evaluation and treatment of bradydysrhythmias in the emergency setting, and many of the recommendations are extrapolated from larger studies investigating the long-term management of these patients.

Risk Management Pitfalls For Bradydysrhythmias In The Emergency Department

1. “The initial ECG looks fine, and I’m not that impressed with the history. I’m sure the patient is fine.”

Many bradydysrhythmias are transient and intermittent in nature. Upon initial evaluation, it is not uncommon to have a normal ECG and an asymptomatic patient. Don’t make any final decisions based on a single ECG. Two ECGs are better than one, and continuous monitoring in the ED is even better.

2. “I know she passed out at home, but she looks fine now, and she really wants to go home.”

It can be tempting to discharge an asymptomatic patient home, especially if she is eager to leave. Remember that the absence of symptoms now does not mean there will be no recurrence. Make sure that there is a clearly identifiable (and reversible or avoidable) cause of symptoms if you plan on discharging a patient home.

3. “I didn’t check the medical record because he said this has never happened before.”

With the pervasiveness of electronic health records, it is becoming difficult to justify failure to review a patient’s records of previous encounters. Patients may not be able to accurately answer whether they have had dysrhythmias in the past. A quick review of the record may uncover additional history that can make a big difference.

4. “I was so focused on the bradycardia that I totally missed the ST changes in the inferior leads.”

Inferior ischemia and myocardial infarction are frequently associated with bradydysrhythmias. Don’t forget to scan through the inferior leads of the ECG to make sure the patient doesn’t need emergent revascularization.

5. “It looks like second-degree type II block on the ECG. We can probably admit him to the floor.”

Even if the patient appears asymptomatic now and a majority of the beats are being conducted, remember that, in certain settings, second-degree type II blocks can rapidly degrade to complete heart block. Strongly consider admitting the patient to an intensive care unit for closer monitoring.

6. “I didn’t even think to ask about travel history or tick bites.”

Infectious causes of bradydysrhythmias, including Chagas or Lyme disease, may not be common if your ED is not within an endemic area; however, for patients who have lived in or traveled to endemic areas, asking about this may identify the underlying cause.

7. “We were so busy focusing on the therapy that I overlooked the fistula in the patient’s arm.”

Clues to the underlying cause of the conduction abnormality may be evident on examination. Make sure you look for evidence of dialysis catheters or fistulas if you are considering the likelihood of hyperkalemia.

8. “He said he had been on the same digoxin dose for the past few years, so I didn’t check.”

In the setting of digoxin therapy (which is known to cause bradydysrhythmias), don’t forget to check drug levels. If recognized as the offending toxin, antibody antidote therapy may be the only treatment for the dysrhythmia.

9. “A heart rate of 45 beats/min in a 25-year-old? I can’t find a reason for her to have any cardiac disease.”

Not all causes of bradydysrhythmias are cardiac in nature. Don’t overlook intra-abdominal pathology as a potential cause. Broaden your differential to include these reflex-mediated syndromes.

10. “I was so pleased I could explain the patient’s syncope with the sinus bradycardia that I completely missed the other injuries.”

Although the evaluation and identification of syncope are important to signal bradydysrhythmia as a potential factor in trauma, do not overlook other injuries the trauma patient may have sustained. Especially in the elderly, be sure to evaluate for extremity fractures, head trauma, and other injuries following syncope and falls.

Tables and Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study will be included in bold type following the reference, where available.

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