CHAPTER 102

Palpitations

Robin Winkler Doroshow, MD, MMS, MEd, FAAP, and Nefthi Sandeep, MD

The term palpitations, which is currently used more by medical personnel than by patients, refers to a sensation of increased awareness of the heart beating faster, harder, or less evenly than expected. Frequently used lay terms for this perception are “racing,” “fluttering,” or “pounding of the heart.” Some patients simply report a sudden unexplainable feeling of being afraid, or they may interpret the symptom as pain or other indescribable discomfort in the chest.

Epidemiology

The prevalence of palpitations is unknown. Palpitations are a fairly common reason for referral of pediatric patients to cardiologists, although it is a significantly less common reason than murmurs or chest pain. Because articulating this complaint requires significant verbal skills as well as bodily awareness, it is not usually reported before age 3 or 4 years; beyond this threshold, it may occur at any age. Cardiac arrhythmia, which is the most likely significant cause of this symptom, occurs at any age—even in utero—but the presenting symptom in younger patients usually reflects secondary or tertiary physiological changes, such as altered mental status, color change, syncope, or respiratory distress.

Clinical Presentation

As with chest pain, patients’ descriptions of symptoms of palpitations are quite varied. Palpitations are almost always episodic, with a sudden sensation of the heartbeat taking the child by surprise. Because this feeling may be alarming or at least disconcerting (even to adults), the patient may not have been a reliable observer and thus, the report of the episode or episodes may be lacking in clarity or detail. The sense of alarm may stem from the unexpected nature of onset of the palpitations, interpretation in an older child or an adult observer that a dangerous cardiac event (eg, heart attack) is occurring, or misinterpretation of a rapid heartbeat as a reflection of fear. It is also not unusual to see a child entirely unconcerned about this symptom accompanied to the visit by an extremely concerned parent.

Almost all patients with palpitations report its occurrence in the absence of other medical issues, as in the case study at the beginning of this chapter.

Pathophysiology

Palpitations are a subjective symptom and may reflect a cardiac issue (most commonly arrhythmia), anxiety, or simply increased somatic awareness. Only the first of these issues has a significant component of abnormal physiology.

The degree to which cardiac function may be compromised in cases of arrhythmia depends on the nature of the rhythm, heart rate, duration of the episode, and presence or absence of underlying cardiac disorders, whether congenital or acquired. In ventricular tachycardia (VT), the heart rate is usually in the range of 150 to 180 beats per minute, and filling is not seriously impaired; however, loss of atrioventricular synchrony and inefficient ventricular emptying result in poor cardiac output in most cases. In addition, VT can deteriorate to ventricular fibrillation, with essentially no functional cardiac output, which is a life-threatening situation. Supraventricular tachycardia (SVT) is by far the most frequently diagnosed sustained arrhythmia in the pediatric population. It is characterized by a substantially higher heart rate (often >250 beats per minute), with relatively less time in diastole and more in systole. This increased heart rate results in compromise of ventricular filling and secondarily of the cardiac output, as well as an unfavorable myocardial supply-demand ratio, which may cause angina-like chest pain. Atrioventricular block is uncommon in otherwise healthy children and is more likely to produce presyncope or syncope than palpitations; however, the latter may also occur. Atrial ventricular block impairs cardiac output by a decrease in ventricular rate and loss of atrioventricular synchrony.

Some patients report erratic, very brief pounding sensations caused by single premature ventricular contractions (PVCs), whereas other patients are unaware of this common arrhythmia (Figure 102.1). Those patients who do perceive them are sensing the increased cardiac output of the immediate post-PVC beat as a “thump” and rarely experience associated symptoms. Premature atrial contractions are quite common but are rarely perceived by the patient.

Palpitations related to anxiety disorders often are associated with other catecholamine-induced symptoms, such as dyspnea or tremor; these somatic symptoms may dominate over psychiatric symptoms and divert the physician’s attention from the pursuit of a psychological cause.

Differential Diagnosis

The differential diagnosis of palpitations is summarized in Box 102.1. In cases of sudden onset of isolated rapid pounding of the heart, SVT (which includes reentrant SVT, junctional tachycardia, ectopic atrial tachycardia, and atrial flutter) is the most common cardiac cause of such pounding (Figure 102.2). One study found that 35 of 238 consecutive children whose rhythms were transmitted transtelephonically during palpitations had SVT; no other significant arrhythmias were found in the other 203 patients. Despite the rarity of them, other tachyarrhythmias and bradyarrhythmias must be considered, however, because of the poorer prognosis associated with them and the importance of instituting therapy to manage them.

Sinus tachycardia in the absence of anxiety may be experienced by individuals with decreased stroke volume, such as patients with myocarditis or cardiomyopathy, either of which may manifest with palpitations. Children undergoing stimulant therapy for attention-deficit/ hyperactivity disorder experience palpitations with surprising infrequency, perhaps because their slight overall increase in heart rate is chronic rather than episodic. Cardiac arrhythmias in this setting are no more common than in the general pediatric population. However, stimulants in the form of so-called energy drinks are becoming increasingly popular in the adolescent and preadolescent population and may result in inappropriate sinus tachycardia. Caffeine is the main active ingredient in most energy drinks. Other beverages, including guarana, also have inotropic and chron-otropic properties. Use of drugs, such as amphetamines, likewise may result in sinus tachycardia, but patients rarely experience symptomatic discomfort. Hyperthyroidism is associated with sustained sinus tachycardia, which patients occasionally report and can also progress to significant cardiac arrhythmias.

Figure 102.1. Electrocardiogram showing premature ventricular contractions (arrows).

Psychogenic palpitations are quite common in childhood, occurring in approximately 50% of pediatric patients with anxiety disorders and panic disorder. Such palpitations may be the presenting symptom and should not be dismissed by the physician as unimportant. For patients in whom anxiety disorders are ruled out, diagnosing somatic hyperawareness, such as is often seen in healthy adolescents (eg, “My heart speeds up when I take a test”), may reassure the patient that there is no underlying cardiac disease.

Figure 102.2. Electrocardiogram showing supraventricular tachycardia at 257 beats per minute. Note ST depression (arrow) caused by relative myocardial ischemia.

Evaluation

The history and documentation of cardiac rhythm are critical to the evaluation of children with palpitations. The history guides the physician in determining which direction to pursue and, in particular, how extensive an arrhythmia workup is required. When arrhythmia is suspected, documentation (ie, “capturing” the arrhythmia) is essential prior to intervention.

Obtaining a complete history and physical examination helps the pediatrician establish a level of concern about the likelihood of cardiac causes for the palpitations. That, in turn, guides elective referral to a cardiologist, emergent referral to an emergency department (ED) or hospital, elective referral to a psychologist or psychiatrist, or, alternatively, management of the condition without further referral.

History

It is important to obtain as much descriptive information as possible directly from the child as well as any witnesses (Box 102.2). Language such as “very fast” may be interpreted differently by different people and, thus, is not helpful. A witness can also report whether the patient had a change in color, respiratory pattern, or mental status.

Palpitations of abrupt onset and offset are more likely to reflect paroxysmal cardiac arrhythmias, while sinus tachycardia resulting from stimulants or anxiety is more likely to have a gradual onset and resolution. Some arrhythmias may be triggered by certain events or actions, such as exertion, emergence from anesthesia, or exposure to stimulants (eg, β agonists).

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