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*The authors acknowledge the special contributions of Binita R. Shah, MD, to prior edition.
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Bradycardia is defined as a heart rate below the normal range for age, and its various etiologies are mentioned in Table 5.1. Clinically significant bradycardia is defined as a heart rate <60 beats per minute (bpm) associated with poor systemic perfusion. Signs of circulatory impairment include poor skin perfusion with pallor; cyanosis; cool mottled extremities; prolonged capillary refill; thready, weak, or absent peripheral pulses; and discrepancy in volume between peripheral and central pulses. Patient is irritable, lethargic, and confused, or has decreased level of consciousness. Respiratory difficulty, decreased pulse pressure of >20 mm Hg, hypotension (decompensated shock), and decreased or no urine output can also be found when severe. The spectrum of bradyarrhythmias includes sinus bradycardia, sinus node dysfunction, sinus node arrest with a slow junctional or ventricular escape rhythm, and atrioventricular (AV) block.
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An ECG is necessary to exclude second-degree or complete heart block (CHB). Findings on ECG include a slow heart rate with P waves that may or may not be visible. QRS duration may be normal or prolonged (depending on the location of the intrinsic cardiac pacemaker). Dissociation of P waves and QRS is seen in CHB. P wave with a normal PR interval preceding each QRS complex is seen in sinus bradycardia.
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Emergency Department Treatment and Disposition
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Patients with bradycardia not associated with evidence of poor systemic perfusion need support of ABCs (airway, breathing, and circulation), observation, and reassessment. Hospitalize patient for continued observation, and consult cardiology for asymptomatic bradycardia from drug ingestion, bradycardia resulting from complete AV block or acquired or congenital heart disease (CHD), or patients with refractory bradycardia requiring pacing.
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