ALTE is not a diagnosis. The term merely describes a common manner of presentation for many different disorders (Table 117A.2). In most studies of ALTE, a possible or likely cause of the event is discovered in approximately half of cases. The occurrence of an ALTE often reflects developmental immaturity in cardiorespiratory responses; these infants appear to experience an exaggerated response to commonly occurring stressors in an infant’s life. However, ALTE also may represent signs of sepsis, meningitis, poisoning, and other potentially life-threatening conditions. Thus, anything that can cause the appearance described in the NIH’s definition may be an underlying cause of ALTE.

Previously, an ALTE with no definable etiology was termed apnea of infancy. We find this term confusing, and prefer the designation ALTE of unknown etiology. In both term and
preterm infants, approximately 90% of unexplained ALTEs occur before the infant is 16 weeks old. Although apnea may be one component of an ALTE, central apnea is a normal finding at all ages; not all episodes of apnea, even if abnormal, are life-threatening; and not all ALTEs involve apnea. The role of apnea in the pathophysiology of ALTE is further complicated because some apnea is a component of the normal variability of breathing in nearly all infants. The absence of airflow, termed apnea, may be the result of absence of respiratory effort (central), obstruction of the airway (obstructive), or a combination of both mechanisms (mixed). Occasional short central apnea, typically of less than 20 seconds and usually preceded by a sigh, may be a normal finding at any age. When it is prolonged longer than 20 to 25 seconds, or is accompanied by bradycardia, cardiac arrhythmia, pallor, hypotonia, or cyanosis, it is termed pathologic apnea and warrants further investigation. Periodic breathing, recognized as alternating periods of apnea and regular breathing, is defined as three or more breathing pauses of more than 3 seconds’ duration, with less than 20 seconds of breathing between pauses. Short-duration episodes of periodic breathing occur normally during infancy. Central apnea events (of less than 20 seconds) often are misinterpreted by anxious parents as being dangerous, thus adding to the dilemma. Physicians caring for infants with an ALTE must be aware that variability in respiratory pattern, and even short central apnea, is common in otherwise perfectly healthy infants.

Our lack of understanding of the pathogenesis of SIDS, coupled with our inability to predict who is at risk for a sudden unexplained death, places the physician responsible for infants who experience an ALTE in a difficult position. Unfortunately, the limitations of our knowledge have resulted in confusion and controversy surrounding the management of infants who are perceived as being at risk of sudden death. This discussion focuses on a practical approach to the diagnosis and management of infants with ALTE, based on available data. As new information is added and clinical experience expands, these recommendations will undoubtedly change.

Although the European Society for the Study and Prevention of Infant Death (ESPID) published recommendations for evaluation of infants with ALTE in 2004 (see Suggested Readings), no comprehensive official guidelines exist for the evaluation and management of ALTE in the United States. General guidelines from U.S. sources may be pieced together from general statements in Consensus Conference Statement from the 1986 NIH Consensus Conference on Infantile Apnea and Home Monitoring and the 2003 Policy Statement from the American Academy of Pediatrics on Apnea, Sudden Infant Death Syndrome, and Home Monitoring (see Suggested Readings).

The first steps in evaluating these patients should focus both on ruling out treatable causes of life-threatening events and on determining if a life-threatening or dangerous event actually occurred. In many instances, parents have witnessed a normal physiologic variation that appears to be life-threatening to the inexperienced layperson. Normal infants can experience respiratory pauses lasting for up to 20 seconds during sleep. Many of these are not associated with color change or desaturation, and frequently they are preceded by a sigh. To a parent waiting for a baby to start breathing again, however, even 10 seconds can seem like an eternity. Thus, this infant may be brought to medical attention in an urgent fashion and labeled as abnormal. The physician is confronted by an anxious parent or caretaker who believes that he has witnessed an event that has endangered the child’s life. Somehow, the physician caring for this child must identify the infant at true risk.

A detailed history of the event is essential. Table 117A.3 summarizes the important features of this history. A description of the circumstances preceding the event is key. Was the patient awake or asleep? Events that occur when the child is awake are often found to be secondary to gastroesophageal reflux or a seizure. Was the event associated with body movements or unusual posturing? Again, this suggests a seizure disorder or gastroesophageal reflux. Was the child struggling to breathe (suggestive of airway obstruction), or were respiratory efforts absent?

An accurate description of the intervention required to reestablish normal breathing is important, because the need for vigorous resuscitation appears to correlate with increased risk of recurrent severe spells and even death. Recovery spontaneously or with minimal intervention (i.e., touching the infant) is reassuring and may suggest that what was witnessed was most likely a normal physiologic event. Information about the time required to reverse the event and the infant’s mental and physical status after the event also is important in planning subsequent evaluation and therapy.

Was the infant premature? Was the delivery difficult? Was respiration initiated in normal fashion at birth? Was there evidence of prior respiratory difficulties? Has the child’s growth and development been appropriate? These questions help to establish a predisposition to abnormalities in control of respiration and also help to identify a chronic condition.

A history of how the infant handles feeding is important. Dysfunctional swallowing is more common in preterm infants and can trigger reflex apnea and bradycardia by direct aspiration, stimulation of laryngeal chemoreceptors, or by reflux of formula into the nasopharynx. Apnea may be central or obstructive, and often occurs during feeding in preterm infants. However, if reflux occurs, apnea may occur at varying intervals after feeding.

Is there a family history of sudden unexplained death in other siblings or relatives? Multiple deaths in a family should make one suspicious about the potential for child abuse or an inherited metabolic disorder. Is there a family history of snoring or obstructive sleep apnea? This information suggests a possible familial predisposition to respiratory control disorders. Table 117A.3 highlights the essential components of the physical examination. An assessment of growth and development, along with a focus on cardiac, neurologic, and respiratory systems, is necessary to identify the subtle signs of chronic conditions that may predispose to life-threatening events. Similarly, evidence of an acute infection (sepsis, central nervous system, respiratory) should be sought so that appropriate therapy can be initiated.