Bradyarrhythmias: A Guide for Junior Doctors

Bradyarrhythmias, or slow heart rhythms, are a common presentation in the emergency department. Recognizing and managing these conditions promptly is crucial. This guide will help you navigate history taking, examination, investigation, and management of bradyarrhythmias, using insights from trusted sources like the Oxford Handbook of Emergency Medicine, WikEM, BMJ Best Practice, NICE guidelines, GPnotebook, and RCEM Learning.

History Taking

When assessing a patient with bradyarrhythmia, it’s essential to gather a thorough history. Here are the key questions to ask:

1. Symptoms:

   • Are you experiencing any dizziness or lightheadedness?

   • Do you have any episodes of syncope (fainting)?

   • Have you noticed palpitations or a slow heartbeat?

   • Do you feel short of breath or fatigued?

2. Medical History:

   • Do you have a history of heart disease, such as myocardial infarction, heart failure, or cardiomyopathy?

   • Are you currently taking any medications, particularly beta-blockers, calcium channel blockers, or digoxin?

   • Have you had any recent infections or surgeries?

3. Family History:

   • Is there a family history of heart disease or sudden cardiac death?

4. Lifestyle Factors:

   • Do you consume alcohol or use recreational drugs?

   • Have you had any recent changes in physical activity or stress levels?

Examination Findings

A focused physical examination can provide valuable clues in diagnosing bradyarrhythmias. Pay attention to the following:

1. Vital Signs:

   • Check the heart rate: Bradycardia is defined as a heart rate less than 60 beats per minute.

   • Blood pressure: Hypotension may indicate hemodynamic instability.

2. General Appearance:

   • Look for signs of distress: Pale, sweaty, or cyanotic appearance.

3. Cardiovascular Examination:

   • Inspect and palpate the chest: Look for any scars from previous cardiac surgeries or pacemakers.

   • Auscultation: Listen for any abnormal heart sounds or murmurs.

   • Peripheral pulses: Assess for the presence and regularity of peripheral pulses.

4. Neurological Examination:

   • Assess mental status: Confusion or altered mental status may suggest poor cerebral perfusion.

Investigations

To confirm the diagnosis and understand the underlying cause, the following investigations are essential:

1. Electrocardiogram (ECG):

   • Identify the type of bradyarrhythmia: Sinus bradycardia, atrioventricular (AV) block, or other forms.

   • Look for signs of ischemia: ST-segment changes that may suggest myocardial infarction.

2. Blood Tests:

   • Electrolytes: Check for imbalances (e.g., hyperkalemia).

   • Thyroid function tests: Hypothyroidism can cause bradycardia.

   • Cardiac enzymes: Elevated levels may indicate myocardial infarction.

3. Imaging:

   • Chest X-ray: To look for signs of heart failure or pulmonary conditions.

   • Echocardiogram: To assess cardiac structure and function.

4. Additional Tests:

   • Holter monitoring: Continuous ECG monitoring to detect intermittent bradyarrhythmias.

   • Tilt-table test: For patients with syncope, to assess for neurocardiogenic causes.

Atrioventricular (AV) Blocks

AV blocks are a type of bradyarrhythmia where the conduction between the atria and ventricles is impaired. Understanding the different types of AV blocks is crucial for appropriate management.

First-Degree AV Block

• Definition: Prolonged PR interval (>200 ms) with a consistent 1:1 relationship between P waves and QRS complexes.

• Symptoms: Usually asymptomatic; found incidentally.

• Management: No specific treatment is required if asymptomatic; address any underlying causes.

Second-Degree AV Block

1. Mobitz Type I (Wenckebach)

   • Definition: Progressive prolongation of the PR interval until a QRS complex is dropped.

   • Symptoms: May be asymptomatic or present with mild symptoms like dizziness.

   • Management: Usually no treatment needed if asymptomatic; monitor and address underlying causes.

1. Mobitz Type II

   • Definition: Sudden dropped QRS complexes without progressive PR interval prolongation.

   • Symptoms: More likely to be symptomatic with dizziness, syncope.

   • Management: More serious than Mobitz Type I; often requires pacemaker insertion due to risk of progression to complete heart block.

Third-Degree (Complete) AV Block

• Definition: Complete dissociation between atrial and ventricular activity; no relationship between P waves and QRS complexes.

• Symptoms: Symptoms are often severe, including syncope, dizziness, and heart failure.

• Management: Emergent treatment with transcutaneous pacing followed by permanent pacemaker insertion.

Management Plan

Management of bradyarrhythmias depends on the type and severity, as well as the patient’s symptoms and underlying cause.

1. Stable Patients:

   • Observation: If asymptomatic and heart rate is not critically low, monitor the patient.

   • Medication Review: Adjust or discontinue any medications that may be contributing to the bradycardia.

2. Unstable Patients:

   • Immediate Treatment:

     • Atropine: Administer 0.5 mg IV, repeat every 3-5 minutes up to 3 mg.

     • Transcutaneous pacing: If atropine is ineffective.

     • Adrenaline/Isoprenaline infusion: Consider if pacing is not available or not effective.

3. Long-term Management:

   • Permanent Pacemaker: Indicated for persistent symptomatic bradyarrhythmias, especially with high-degree AV block.

   • Treat underlying causes: Manage conditions like hypothyroidism or electrolyte imbalances.

Conclusion

Bradyarrhythmias can range from benign to life-threatening. A systematic approach to history taking, physical examination, investigation, and management is crucial for optimal patient outcomes. Always keep in mind the patient's stability and underlying causes while formulating your treatment plan.