CHAPTER 63 ■ PALPITATIONS STEVEN C ROGERS, ANDREW T HEGGLAND INTRODUCTION Heart palpitations can most easily be characterized by the perception of an abnormal heartbeat or heart rate (HR) by the patient Descriptions commonly given include heart “racing,” “pounding,” “fluttering,” “beating irregularly,” or a sensation of the heart “stopping” intermittently In children, most etiologies of palpitations are benign but are often accompanied by significant anxiety Pediatric patients demonstrate great variability in sensitivity to changes in HR or rhythm A child who has trivial cardiac events may express severe symptoms while one with a significant arrhythmia may remain asymptomatic The challenge is to determine which complaint can be managed in the emergency department (ED) and which merits urgent consultation and/or further evaluation by a cardiologist PATHOPHYSIOLOGY The heart is innervated by the vagus nerve (cranial nerve X) and the sympathetic ganglia Cardiovascular reflexes (e.g., vasovagal bradycardia) are transmitted by the vagus nerve Pain sensation (e.g., related to myocardial ischemia) travels through afferent fibers associated with the sympathetic ganglia In most patients, the sensation of the heartbeat is not felt Children with documented arrhythmias, such as supraventricular tachycardia (SVT) and stable ventricular tachycardia (VT), may not complain of any symptoms Even patients with heart murmurs audible to the unassisted ear can learn to ignore this obvious cue Patients with palpitations often report a perception of increased force of cardiac contraction, tachycardia, or irregular heartbeat Increased force of the contraction is better detected when the patient is supine At times, it may be described as a rushing or pounding in the ears, particularly when the ear is pressed against a pillow Caffeine or alcohol consumption, illicit drug use, exercise, and emotional excitement can produce this same sensation Patients with premature contractions and a compensatory pause may describe the feeling that their hearts “flip-flop” or “stop.” Many patients with premature atrial or ventricular contractions notice the subsequent beat after the initial “short” beat because of the increased stroke volume ejected Other patients may complain of a choking or full sensation in the neck Jugular venous pulsation associated with right atrial contraction against a closed tricuspid valve (atrioventricular [AV] block with or without atrial tachycardia) can present in this way True cardiac arrhythmias arise from various mechanisms that are discussed in Chapter 86 Cardiac Emergencies DIFFERENTIAL DIAGNOSIS Many conditions may produce palpitations ( Table 63.1 ) Most children with palpitations not have significant cardiac pathology ( Table 63.2 ) However, there are some life-threatening conditions that may come to medical attention because of abnormal cardiac sensation ( Table 63.3 ) Wolff–Parkinson–White (WPW) syndrome and prolonged QT syndrome are two potentially lethal diseases that may be diagnosed on a resting electrocardiogram (EKG) A patient with palpitations during exercise should also raise concern for hypertrophic cardiomyopathy, SVT, VT, or myocardial ischemia In addition, palpitations in children with known congenital heart disease are more likely to be caused by a serious cardiac arrhythmia Diagnosis of noncardiac causes of life-threatening palpitations, including hypoxemia, hypoglycemia, hyperkalemia, and hypocalcemia, can be made by characteristic EKG changes, serum electrolyte determinations, rapid bedside glucose, and oxygen saturation measurements Hyperdynamic Cardiac Activity Increased HR and contractility are physiologic responses to catecholamine release, which may occur with exercise, emotional arousal, hypoglycemia, and pheochromocytoma Similarly, increased cardiac work accompanies conditions that increase the basal metabolic rate such as fever, anemia, and hyperthyroidism Sympathomimetic and anticholinergic drugs are groups of substances that directly modulate the autonomic nervous system, causing tachycardia, hyperdynamic cardiac activity, and palpitations ( Table 63.4 ) Postural orthostatic tachycardia syndrome (POTS) describes a form of orthostatic intolerance characterized by chronic fatigue, tachycardia (more than 40 beats per minute over baseline in patients 13 years of age and younger or more than 120 beats per minute for patients 14 years of age and older) typically without hypotension upon standing POTS is commonly seen in teenage girls and manifests as palpitations, dizziness, and tremulousness The diagnosis may be made when no other cause for symptoms is found and the patient has replication of symptoms with headup tilt table testing Management consists of a multidisciplinary approach including family education, avoidance of precipitating factors (e.g., sudden posture changes, large meals, or vasodilating drugs), adequate water and salt intake, and regular exercise Medications targeted at maintaining blood volume, avoiding vasodilation, or treating secondary symptoms may be required Sinus Bradycardia Low basal metabolic rate associated with hypothyroidism may present with a slow HR and sinus rhythm Similarly, in the absence of significant sympathetic nervous system input, the HR may be slow This state may be responsible for the sinus bradycardia associated with sleep or with ingestion of drugs such as clonidine, sedative-hypnotics, or narcotics Athletic training may result in a highly efficient heart with high ventricular ejection fraction and sinus bradycardia TABLE 63.1 DIFFERENTIAL DIAGNOSIS OF PALPITATIONS Hyperdynamic cardiac activity Anemia Anxiety/panic attacks/hyperventilation syndrome Drug induced ( Table 63.4 ) Emotional/sexual arousal Exercise Fever Hyperthyroidism Hypoglycemia Pheochromocytoma Postural orthostatic tachycardia syndrome Sinus bradycardia Athleticism/advanced physical training (e.g., marathon runners) Drug induced ( Table 63.4 ) Hypothyroidism Sleep True cardiac arrhythmias Irregular rhythm or bradyarrhythmia Complete heart block Postoperative cardiac repair (especially ventriculoseptal defect, atrioventricular canal repairs) Premature atrial contractions Premature ventricular contractions Sick sinus syndrome Sinus arrhythmia/respiratory variation Tachyarrhythmias (see Chapter 77 Tachycardia ) True Cardiac Arrhythmias SVT represents the most common tachyarrhythmia of childhood and often presents with a chief complaint of palpitations Possible underlying causes