PALPITATIONS

JAMES F. WILEY II, MD, MPH AND STEVEN C. ROGERS, MD

Palpitations represent a disagreeable perception of the heartbeat by the patient. Descriptions commonly given include “pounding,” “fluttering,” “jumping in the chest,” or a sensation of the heart “stopping.” In children, most etiologies of palpitations are benign but can cause a great amount of anxiety. Pediatric patients demonstrate a high degree of variation in their sensitivity to changes in the heart rate (HR) or rhythm. A patient who actually has trivial cardiac events may express severe symptoms while children with a significant arrhythmia may remain asymptomatic. The challenge to the emergency physician is to determine which complaint can be managed in the emergency department (ED) and which merits further consideration by a cardiologist.

PATHOPHYSIOLOGY

The heart is innervated by the vagus nerve (cranial nerve X) and the sympathetic ganglion. 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 relate an indirect perception of increased force of cardiac contraction, tachycardia, or irregular heartbeat. Increased force of the contraction is often 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 arousal 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 94 Cardiac Emergencies.

DIFFERENTIAL DIAGNOSIS

Many conditions may produce palpitations (Table 58.1). Most children with palpitations do not have significant cardiac pathology (Table 58.2). However, many life-threatening conditions can come to medical attention because of abnormal cardiac sensation (Table 58.3). Wolff–Parkinson–White (WPW) syndrome and the 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 frequently 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, like that 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 commonly available substances that directly modulate the autonomic nervous system, causing tachycardia, hyperdynamic cardiac activity, and palpitations (Table 58.4).

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