Pediatric emergency medicine trisk 304

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 do 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