Bradyarrhythmia

Objectives

To guide the management of patients presenting to medical facilities with bradyarrhythmia.

Scope

This guideline describes the resuscitation of critically unwell patients with bradyarrhythmia. It also considers prolonged casualty care and paediatric circumstances. The management of stable patients without adverse features is also described in brief. Further advice for stable patients should be sought from cardiology experts.

Audience

This guideline is intended for the use of registered healthcare professionals fulfilling a general role in forward medical locations or in an Emergency Department on deployed operations.

Initial Assessment & Management

Bradycardia is defined as a heart rate < 60 beats per minute. Physiological sinus bradycardia is prevalent at rest in deployed personnel due to high levels of fitness and physical conditioning. This is unlikely to be symptomatic. 

By contrast, the incidence of symptomatic or pathological bradycardia is likely be low in healthy, pre-screened deployed personnel. However, it may be encountered on operations due to undiagnosed cardiac conditions becoming unmasked, the presence of other unscreened persons working within the theatre of operations (e.g. civilian contractors or allied force personnel) or extrinsic causes e.g. electrolyte imbalance. 

Management will be guided by:

• Availability of recommended medications in the medical treatment facility
• Presence of adverse features
• Risk factors for asystole.

In an unresponsive patient, initially follow the Basic Life Support (BLS) algorithm to ensure the presence of a pulse. If there is no palpable pulse CPR should be started, proceeding to the delivery of Advanced Life Support (ALS) as soon as possible.

If there is cardiac output and an arrhythmia is suspected:

Assess the patient using the MARCH/ABCD approach. 

Correct hypoxia if present 

Record a complete set of observations and establish cardiac monitoring

Perform a 12 lead ECG as soon as possible

Obtain IV access

Consider other reversible causes (e.g. presence of electrolyte abnormalities) 

Assess for adverse features:

Shock (systolic BP <90mmHg)

Syncope (including recent collapse or transient loss of consciousness without other explanation)

Heart failure (pulmonary oedema causing respiratory failure)

Myocardial ischaemia (cardiac chest pain or evidence of ischaemia on ECG)

In addition, extremes of heart rate (<40 beats per minute) are often tolerated poorly. 

If there are no adverse features, assess for the risk of asystole using the following checklist: 

• Recent asystole
• Mobitz II AV block (see accordion content)
• Complete heart block with broad QRS (see accordion content)
• Ventricular pause > 3s (on a standard ECG at 25mm/sec, 5 large squares = 1 second)

If the patient is stable, additional historical factors include:

• Risk of electrolyte disturbance – medications, concurrent illness e.g. diarrhoea/vomiting
• Past history of syncope, presyncope, chest pain, breathlessness or oedema
• Family history of cardiac arrhythmia, unexplained sudden death or sudden cardiac death
• Drug history and allergies

No adverse features or risk of asystole

The patient can be observed. 

Adverse features

Apply defibrillation pads pre-emptively. If cardiac output is lost, commence ALS. 

Administer atropine 500mcg IV/IO and assess response (targeting a HR >60bpm and improvement in adverse features)

If response is unsatisfactory this can be repeated up to a maximum of 3 milligrams.  

No adverse features but risk of asystole present

Use interim measures depending on clinical risk assessment.

Treatment options are dependent on medication and equipment availability in forward medical environments. Continuous vital signs monitoring is required (if available).

Interim measures include:

Atropine to a maximum of 3mg

Transcutaneous pacing (see guidance)

Sympathomimetic drugs:

• Isoprenaline 5 micrograms / min IV
• Adrenaline 2-10micrograms / min IV 

Advanced Assessment & Management

The basic principles of managing bradycardia in deployed hospital locations are the same as outlined in the 'Initial Assessment & Management' above.

Alterative drugs of use, dependent on medical treatment facility, include:

• Aminophylline
• Glucagon (if bradycardia caused by beta blocker or calcium channel blocker) 
• Glycopyrrolate (can be used as alternative to atropine)

In deployed hospital locations, expert advice can be sought for consideration of transvenous pacing. 

Paediatric Considerations

Paediatric bradycardia is defined as:

• < 1 year < 80bpm

• > 1 year < 60bpm

If a child has weak/absent signs of cardiac output follow the Paediatric Advanced Life Support algorithm

If there is evidence of cardiac output, assess initially with MARCH/ABCD approach.

Recognise and treat reversible causes.

Record and correct SpO2 if < 94%, respiratory rate, heart rate, CRT, cardiac monitoring, BP (if possible) and AVPU score.

Establish IV access. 

Signs of decompensation include:

Reduced consciousness

Tachypnoea

BP < 5th centile*

CRT > 2 seconds

Weak or impalpable peripheral pulses 

Ensure optimal oxygenation with positive pressure ventilation if required.

If unconscious and HR < 60 beats per minute despite oxygenation, start chest compressions. 

*Systolic BP 5th Centile (mmHg)

1 month = 50mmHg

1 year = 70mmHg

5 years = 75mmHg

10 years = 80mmHg

If vagal stimulation is a possible cause:

Atropine 

• Up to 11 years: 20 micrograms/kg IV
• 12-17 years: 300 – 600 micrograms IV. Larger doses may be used in emergency. 

If no response to oxygenation or atropine consider:

Adrenaline

• 10 micrograms/kg, repeat if necessary

Pacing is rarely required and guided by aetiology.