Bradycardia is a heart rate below normal range for age with many etiologies. Bradycardia of <60 beats per minute (bpm) associated with poor systemic perfusion is clinically significant. Signs 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. Patients are irritable, lethargic, confused, or have decreased level of consciousness. Severe bradycardia may cause respiratory difficulty, decreased pulse pressure of >20 mm Hg, hypotension (decompensated shock), and decreased or no urine output. There are several types of bradyarrhythmias including sinus bradycardia, sinus node arrest with a slow junctional or ventricular escape rhythm, and atrioventricular (AV) block.
ECG is necessary to exclude second-degree or complete heart block (CHB), and findings include a slow heart rate with P waves that may or may not be visible. QRS duration is 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.
Figure 5.1 ▪ Sinus Bradycardia.
(A) 12-lead ECG showing a heart rate of 50 bpm. The patient is in sinus rhythm as every QRS is preceded by a P-wave, a QRS complex follows every P-wave, and the P-wave axis is normal. This could be a normal phenomenon in well-trained athletes. (B) An ECG from a different patient also with a slow heart rate. Note the P-wave axis in leads II, III, and aVF. The P-waves are inverted in these leads, suggesting this is not a sinus-rhythm. This patient is in an ectopic atrial rhythm, which is usually normal. (Photo contributor: Shyam Sathanandam, MD.)
Emergency Department Treatment and Disposition
Stabilize ABCs and observe and reassess patients with bradycardia not associated with evidence of poor systemic perfusion and admit for continued observation. Consult cardiology for asymptomatic bradycardia from drug ingestion, complete AV block, acquired or congenital heart disease (CHD), or patients with refractory bradycardia that require pacing.
If cardiorespiratory compromise is present, emergent intervention to establish a patent airway and assist breathing with delivery of 100% oxygen. Perform chest compressions if the patient fails to improve (patient remains unresponsive or flaccid with poor systemic perfusion), the heart rate remains <80 bpm in neonates or <60 bpm in infants and children. If there is no response to effective oxygenation and ventilation, give epinephrine. A continuous epinephrine, isuprel, or dopamine infusion titrated to effect may be required. For symptomatic bradycardia due to vagal stimulation, cholinergic drug toxicity, or primary AV block, give atropine as the drug of choice. Atropine usually is not effective for hypoxic-ischemic induced bradycardia. Vagally induced bradycardia usually resolves once the stimulation is withdrawn. Atropine is very effective if used prophylactically before vagal stimulation in procedures such as endotracheal intubation.
Figure 5.2 ▪ Differential Diagnosis of Bradycardia. Subarachnoid Hemorrhage (SAH) Presenting with Cushing Triad.
A noncontrast head CT scan shows hyperdensity in the basal cisterns in the area of circle of Willis, with blood in the fourth ventricle (findings typical of SAH) in an ...