Bradycardias

Sinus Bradycardia

Pathology:                  Sinus rhythm at a heart rate <60 beats per minute (bpm)

Aetiology:                     Normal: Sinus bradycardia can be found in athletes and in individuals during their sleep.

Secondary to drug therapy: Beta blockers, digoxin, calcium channel blockers, and anti-arrhythmics have all been known to cause sinus bradycardia.

Other: Myocardial infarction (MI), sick sinus syndrome, hypothyroidism, and hypothermia can also be potential causes.

Symptoms:                   In non-pathological conditions, sinus bradycardia can often be asymptomatic, but symptomatic patients may suffer from shortness of breath, pre-syncope, syncope, and chest pain.

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Signs:                               Physical signs of sinus bradycardia can include a slow, regular pulse, tachycardia, hypotension, and an audible third heart sound.

Investigations:          Bloods: A full blood count (FBC), thyroid function tests (TFTs), and digoxin levels can all be checked.

ECG: For a more detailed evaluation, a Holter monitor can be connected for a 24 hour recording.

Treatment:                  

• IV atropine
• Glucagon in the case of beta blocker overdose
• Digibind for digoxin toxicity
• Temporary pacing wire or permanent pacemaker for chronic cases

Complications:          Usually minimal or no complications.

Prognosis:                  Outlook is usually good.

Figure 1.7 Sinus Bradycardia