Bradycardia Calcium channel blockers Clonidine Digoxin Narcotics Organophosphate pesticides Sedative-hypnotic agents β-Adrenergic blockers EVALUATION AND DECISION The ill-appearing child with palpitations requires rapid assessment for the presence of hypoxemia, shock, hypoglycemia, or an existing lifethreatening arrhythmia Further evaluation should include measurement of hemoglobin, serum glucose, electrolytes, calcium, and pulse oximetry or blood gas The presence of heart disease should be ascertained by a 12-lead EKG and rhythm strip, followed by continuous monitoring, frequent vital signs, and chest radiograph ( Fig 63.1 ) Specific arrhythmias should be treated as outlined in Chapter 86 Cardiac Emergencies The asymptomatic child with palpitations by history may also have an intermittent or continuing arrhythmia Continuous cardiac monitoring and a resting 12-lead EKG performed while the patient is in the ED increase the likelihood that this abnormality will be detected Patients with repeated episodes of palpitations may benefit from 24-hour ambulatory (Holter) or longer-term event monitoring, and warrant referral to a pediatric cardiologist Any patient with a history of syncope, congenital heart disease, or particularly, postoperative or exercise-induced palpitations is at greater risk for having a true cardiac arrhythmia as the cause of his or her symptoms Similarly, the presence of a short P-R interval with the typical delta wave morphology of WPW syndrome or a prolonged corrected Q-T interval (see Chapter 86 Cardiac Emergencies ) indicates the need for evaluation by a pediatric cardiologist The presence or recent history of fever or an upper respiratory infection should prompt the emergency physician to look for signs and symptoms of myocarditis or acute rheumatic fever Myocarditis describes inflammation of the muscle wall of the heart Multiple organisms can cause this