From the Guidelines
The workup for bradycardia should begin with a thorough history and physical examination, followed by an electrocardiogram (ECG) to document the heart rate and rhythm, as recommended by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.
Initial Evaluation
The initial evaluation of a patient with suspected bradycardia should include:
- A thorough history and physical examination to identify potential causes of bradycardia
- An electrocardiogram (ECG) to document the heart rate and rhythm
- Basic laboratory studies such as complete blood count, comprehensive metabolic panel, thyroid function tests, and cardiac biomarkers to identify potential causes like electrolyte abnormalities, hypothyroidism, or myocardial injury
Further Evaluation
Further evaluation may include:
- Ambulatory cardiac monitoring (24-hour Holter or longer-term event monitoring) to document the heart rate and rhythm over a longer period
- Echocardiography to assess cardiac structure and function
- Exercise stress testing to evaluate chronotropic competence
- Electrophysiology study (EPS) in selected patients with suspected bradycardia or conduction disorders, as recommended by the 2018 ACC/AHA/HRS guideline 1
Management
For acute symptomatic bradycardia, atropine 0.5 mg IV every 3-5 minutes up to a total of 3 mg can be administered, as recommended by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. If atropine is ineffective, temporary transcutaneous pacing or infusions of chronotropic agents like dopamine (2-10 mcg/kg/min) or epinephrine (2-10 mcg/min) may be required. For patients with persistent symptomatic bradycardia due to sinus node dysfunction or atrioventricular block, permanent pacemaker implantation is often the definitive treatment, as recommended by the 2018 ACC/AHA/HRS guideline 1. The workup should also focus on identifying and addressing reversible causes such as medication effects (beta-blockers, calcium channel blockers, digoxin), increased vagal tone, sleep apnea, or infiltrative cardiac diseases.
From the FDA Drug Label
Atropine Sulfate Injection, USP in clinical doses counteracts the peripheral dilatation and abrupt decrease in blood pressure produced by choline esters 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 can be used to treat bradycardia by counteracting vagal cardiac slowing or asystole.
- Key points:
- Atropine can abolish reflex vagal cardiac slowing or asystole
- Atropine can prevent or abolish bradycardia or asystole produced by certain drugs or vagal stimulation
- Atropine may be used to treat bradycardia, but the label does not provide a comprehensive workup for the condition 2
From the Research
Workup for Bradycardia
The workup for bradycardia involves a thorough history and physical examination to identify possible causes of sinoatrial node dysfunction or AV block 3. The following steps are involved in the workup:
- A thorough history to identify possible causes of bradycardia, including symptoms, medical history, and medication use
- A physical examination to assess for signs of cardiac disease or other underlying conditions
- Electrocardiogram (ECG) to evaluate the heart rhythm and identify any abnormalities
- Laboratory tests to evaluate for underlying conditions such as electrolyte imbalances or thyroid dysfunction
Diagnostic Evaluation
The diagnostic evaluation for bradycardia may involve additional tests, including:
- ECG Holter monitoring to evaluate the heart rhythm over a longer period
- Transtelephonic monitoring of cardiac rhythm to evaluate the heart rhythm in real-time
- Electrophysiological investigation to evaluate the electrical activity of the heart
- Echocardiography or coronariography to evaluate for cardiac structural disease
Special Considerations
Certain medications, such as beta-blockers and sodium channel blockers, can cause bradycardia 4. In patients taking these medications, the workup should include evaluation for potential drug interactions and consideration of alternative medications. Additionally, underlying conditions such as renal failure and hyperkalemia can contribute to bradycardia 5. The workup should include evaluation for these conditions and consideration of their impact on the patient's symptoms and treatment.
Chronotropic Reserve
The chronotropic reserve of the heart can be evaluated using the atropine test and isoproterenol test 6. These tests can help identify patients with inadequate chronotropic reserves, who may require preventive pacemaker implantations.
Clinical Presentation
The clinical presentation of bradycardia can vary, and the workup should take into account the patient's symptoms, medical history, and physical examination findings 7. The therapeutic decision should be based on the type of arrhythmia, associated symptomatology, cardiac structural disease, and activity of the patient.