What is the workup for bradycardia (abnormally slow heart rate)?

From the Guidelines

The initial work-up for bradycardia should include a thorough history, physical examination, and 12-lead ECG, with a focus on assessing hemodynamic stability and symptoms, as recommended by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. Key steps in the work-up:

• Obtain vital signs, including blood pressure and oxygen saturation.
• Perform a focused cardiac and respiratory examination.
• Order a 12-lead ECG to determine the type of bradycardia (e.g., sinus bradycardia, AV block).
• Check basic laboratory tests: complete blood count, electrolytes, renal function, and thyroid function.
• Review the patient's medication list for drugs that can cause bradycardia (e.g., beta-blockers, calcium channel blockers).
• Consider additional tests based on clinical suspicion:
  • Chest X-ray if respiratory causes are suspected
  • Echocardiogram if structural heart disease is suspected
  • Holter monitor or event recorder for intermittent bradycardia
  • Exercise stress test to assess chronotropic competence If the patient is unstable or symptomatic, be prepared to initiate treatment with atropine (0.5 mg IV, repeated every 3-5 minutes up to 3 mg) or temporary transcutaneous pacing while continuing the diagnostic work-up, as recommended by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. This approach allows for rapid assessment of the underlying cause of bradycardia, which could range from benign (e.g., athletic heart) to life-threatening conditions (e.g., complete heart block), and is supported by the most recent and highest quality study available 1.

From the FDA Drug Label

Atropine-induced parasympathetic inhibition may be preceded by a transient phase of stimulation, especially on the heart where small doses first slow the rate before characteristic tachycardia develops due to paralysis of vagal control Adequate doses of atropine abolish various types of reflex vagal cardiac slowing or asystole The drug also prevents or abolishes bradycardia or asystole produced by injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus.

The workup for bradycardia is not directly addressed in the provided drug label. However, atropine is mentioned as a treatment to abolish or prevent bradycardia caused by various factors, including reflex vagal cardiac slowing, choline esters, anticholinesterase agents, or other parasympathomimetic drugs 2.

• Key points:
  • Atropine can prevent or abolish bradycardia
  • Atropine works by paralyzing vagal control and inducing parasympathetic inhibition However, the initial workup and diagnostic approach to bradycardia are not specified in the label.

From the Research

Workup for Bradycardia

The workup for bradycardia, or an abnormally slow heart rate, involves several steps to determine the underlying cause and appropriate treatment.

• The initial approach to a patient with bradycardia is based on the history, physical examination, and 12-lead electrocardiogram (ECG) 3.
• A 12-lead ECG is the cornerstone for diagnosis and can provide valuable information about the heart's rhythm and potential underlying conditions 4, 5.
• The ECG can show various types of bradycardia, including high-grade AV block, sinus bradycardia, sinuatrial arrest, and bradycardic atrial fibrillation 6.
• The physical examination can provide important clues about the underlying cause of bradycardia, such as signs of cardiac disease or other conditions that may be contributing to the slow heart rate 3.
• Additional diagnostic tests, such as echocardiography or coronary angiography, may be necessary to evaluate the heart's structure and function 3.
• In some cases, further evaluation with ECG Holter monitoring, transtelephonic monitoring of cardiac rhythm, or electrophysiological investigation may be needed to diagnose and manage bradycardia 3.

Diagnostic Considerations

When evaluating a patient with bradycardia, it is essential to consider various potential causes, including:

• Primary disturbance of cardiac automaticity and/or conduction 6
• Adverse drug effects 6
• Acute myocardial infarction 6
• Pacemaker failure 6
• Intoxication 6
• Electrolyte disorders 6
• Other conditions, such as acute pulmonary embolism, which can present with symptomatic bradycardia 7

Management

The management of bradycardia depends on the underlying cause and the patient's symptoms.

• In some cases, bed rest may be sufficient to resolve symptoms 6.
• Intravenous drugs to increase ventricular rate may be necessary 6.
• Temporary or permanent pacing may be required in certain situations 6.
• Other treatments, such as atropine or catheter-directed thrombolysis, may be needed in specific cases 7.