Sinus bradycardia (SB) is a sinus rhythm with a rate less than 60 bpm i.e.
Rate: Slow (<60 bpm)
Rhythm: Regular
P waves: Normal (upright and uniform)
PR interval: Normal (0.12-0.2 seconds)
QRS: Normal (0.06-0.1 seconds)
Causes:
- Vagal stimulation, physiologic causes (in well-trained athletes), sleep
- Hypothyroidism, hypothermia, electrolyte imbalances (eg. hyperkalemia)
- Inferior wall myocardial infarction (MI)
- Sick sinus syndrome
- Medications (eg. beta blockers, calcium channel blockers,digoxin)
Treatment:
Sinus bradycardia can result in reduced cardiac output and breakthrough dysrhythmias. Treatment is guided by evaluation of the underlying cause and by whether symptoms are present.
- Drug therapy (including atropine and epinephrine) should be considered for patients who manifest signs of hypoperfusion or are symptomatic (dizzy, weak, or hypotensive).
- Pacemakers (temporary or permanent) may be required if drug therapy is ineffective.
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