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Apparent Life-Threatening Event (ALTE)

by Elizabeth J. Palumbo, MD

An apparent life-threatening event (ALTE) is the sudden occurrence of certain alarming symptoms such as prolonged periods of no breathing (apnea), change in color or muscle tone, coughing, and gagging in children under 1 year of age.

  • Known causes include nervous system disorders and infections.

  • The diagnosis is based on a discussion with caregivers, a physical examination, and the results of certain laboratory tests.

  • The prognosis depends on the cause of the apparent life-threatening event.

  • Treatment is aimed at specific causes when they can be identified.

ALTE is not a specific disorder. It is a group of symptoms that occur suddenly in young children. Although ALTE would seem to be related to sudden infant death syndrome (SIDS—see Sudden Infant Death Syndrome (SIDS)), there is no clear relationship between the two disorders.


The most common causes of ALTE include gastroesophageal reflux disease, nervous system disorders (such as seizures or brain tumors), and infections (such as meningitis). Less common causes include heart disorders, metabolic disorders, child abuse, and narrowing or complete blockage of the airways. A cause cannot be determined in about 50% of cases.


An ALTE usually is characterized by an unexpected, sudden change in an infant’s breathing that alarms the parent or caretaker. Features of an event include some or all of the following:

  • Not breathing for 20 seconds or more

  • Color change, usually blue or pale, but sometimes red

  • Change in muscle tone, usually floppy

  • Choking or gagging


When an ALTE occurs, the doctor asks several key questions:

  • What was observed by the caregiver who witnessed the event (including a description of changes in breathing, color, muscle tone, and eyes, noises made, length of the episode, and symptoms that occurred before the ALTE)?

  • What interventions were taken (such as gentle stimulation, mouth-to-mouth breathing, or cardiopulmonary resuscitation [CPR])?

  • Did the mother use drugs while pregnant? Do members of the family currently use drugs, tobacco, and alcohol?

  • What was the child's gestational age (length of time spent in the uterus after the egg was fertilized)? Were there any complications at birth? Did the infant remain hospitalized for apnea?

  • While feeding, does the child gag, cough, or vomit? Has poor weight gain been an issue?

  • Has the child reached all age-appropriate developmental milestones?

  • Has the child had an ALTE before or experienced a recent injury?

  • Have there been any other ALTEs in the family or early death?

The doctor does a physical examination to check for obvious defects, particularly nervous system abnormalities, such as being too stiff (posturing) or being too floppy (poor muscle tone), and signs of injury.

The doctor may do laboratory tests (blood [including liver function], stool, urine, and spinal fluid studies), imaging tests (such as a chest x-ray or computed tomography [CT] of the head), electrocardiography, or a combination of tests based on the infant's examination findings. Other tests to check for possible seizure activity (such as electroencephalography―see Tests for Brain, Spinal Cord, and Nerve Disorders : Electroencephalography) also may be done.


The cause, if identified, is treated. Infants who have required CPR, have had any abnormalities identified during the examination or initial laboratory testing, or whose ALTE history is concerning to the doctor are hospitalized for monitoring and further evaluation.

Parents and caregivers should be trained in CPR for infants and in general safe infant care (such as putting infants to sleep on their back and eliminating exposure to tobacco smoke). Doctors sometimes recommend home apnea monitoring devices for a limited period of time. Monitors that can record the infants’ breathing pattern and heart rate are preferred to those that simply sound an alarm. Recording monitors may help doctors distinguish false alarms from real events.