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Apparent Life-Threatening Event (ALTE)

By Elizabeth J. Palumbo, MD, The Pediatric Group, Fairfax, VA

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Patient Education

An apparent life-threatening event is the sudden appearance of certain alarming symptoms (eg, apnea, change in color or muscle tone, coughing, gagging, choking). The caregiver may fear that the child is dead or their life is in jeopardy. It typically occurs in children < 1 yr with peak incidence at 10 to 12 wk. Causes may be digestive, neurologic, respiratory, infectious, cardiac, metabolic, or traumatic (eg, resulting from abuse). Treatment is aimed at specific causes when identified.

An apparent life-threatening event (ALTE) is not a diagnosis but a group of symptoms that occur acutely in young children.


The most common causes include

  • Digestive: Gastroesophageal reflux disease or swallowing difficulty when associated with laryngospasm or aspiration

  • Neurologic: Neurologic disorders (eg, seizures, brain tumors, breath holding or abnormal brain stem neuroregulation of cardiorespiratory control, hydrocephalus, brain malformations)

  • Respiratory: Infections (eg, respiratory syncytial virus, influenza, pertussis)

  • Infectious: Sepsis, meningitis

Less common causes include

  • Cardiac disorders

  • Metabolic disorders

  • Upper airway obstruction (eg, obstructive sleep apnea)

  • Other (eg, drug-related, anaphylaxis, abuse)

Causes may be genetic or acquired. About 50% of cases are considered idiopathic. If an infant is under the care of one person and has repeated episodes with no clear etiology, child abuse should be considered.

Symptoms and Signs

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

  • Apneic episode

  • Color change

  • Change in muscle tone

  • Choking or gagging

Many infants appear well by the time they present. Ongoing symptoms are concerning but help suggest a cause and guide evaluation.


Evaluation initially involves a thorough history, including

  • Observations by the caregiver who witnessed the event, particularly a description of changes in breathing, color, muscle tone, and eyes; noises made; length of episode; and any preceding signs such as respiratory distress or hypotonia

  • Interventions taken (eg, gentle stimulation, mouth-to-mouth breathing, CPR)

  • Prenatal (maternal) and current family use of drugs, tobacco, and alcohol

  • Information about the infant’s birth (eg, gestational age, perinatal complications)

  • Feeding habits (whether gagging, coughing, vomiting, or poor weight gain has occurred)

  • Developmental history (eg, milestones)

  • Prior history of ALTE or recent trauma

  • Family history of ALTE, early deaths, or possible causative disorders

Physical examination is done to check for obvious malformations, neurologic abnormalities (eg, posturing, inappropriate head lag), and signs of infection or trauma (particularly including retinal hemorrhage on funduscopy).

Laboratory and imaging tests (see Diagnostic Tests for Causes of Apparent Life-Threatening Event (ALTE)) are done to check for possible causes. These tests should be done based only on history and physical examination findings, including whether the infant is still symptomatic or has required medical intervention.

Risk factors for child abuse should be sensitively assessed (see Overview of Child Maltreatment). Recurrent ALTEs that are concerning for abuse are those that occur only in the presence of a parent or caretaker but do not occur in the presence of hospital staff or when the infant is alone (eg, sleeping while attached to a monitor).

Diagnostic Tests for Causes of Apparent Life-Threatening Event (ALTE)


Possible Causes

Typical initial testing

Blood tests, typically including

  • CBC and differential

  • Electrolytes (Mg, Ca, Na, K), bicarbonate, and glucose

  • Liver function tests

  • Lactate





Liver disorders

Metabolic disorders

Chest x-ray




Cultures (blood, stool, urine, CSF)



Cardiac monitoring in hospital


QT abnormalities

Lumbar puncture


Skeletal survey


Toxicology screen




Additional tests based on clinical suspicion



Brain imaging (head CT, MRI)

Trauma, hemorrhage, tumor



Esophageal pH monitoring*

Gastroesophageal reflux disease

Nasal swab

Respiratory syncytial virus infection

Pertussis blood tests and cultures


Serum lactate

Hereditary enzyme defects (eg, glycogen storage disease type I, fatty acid oxidation defects, multiple carboxylase deficiency, methylmalonicaciduria)


Toxins (eg, salicylates, ethylene, glycol, ethanol, methanol)

Upper GI with radioisotope milk scanning*

Gastroesophageal reflux disease

*In infants with a history of spitting up, gagging, vomiting, coughing, or difficulty feeding.


Prognosis depends on the cause of ALTE. For example, risk of death is higher if the cause is a serious neurologic disorder. The relationship of ALTE to SIDS (see Sudden Infant Death Syndrome (SIDS)) is unclear. About 4 to 10% of infants who die of SIDS have a history of ALTE, and the risk of SIDS is higher if an infant has had 2 or more ALTEs. Also, infants who have had an ALTE share many of the same characteristics with infants who die of SIDS. However, incidence of ALTE, unlike that of SIDS, has not decreased in response to the Safe to Sleep® campaign.

There seem to be no long-term effects on development from the ALTE itself, but the causative disorder (eg, cardiac or neurologic) may have such effects.


  • Treatment of cause

  • Sometimes home monitoring devices

The cause, if identified, is treated. If the infant required resuscitation or if evaluation detected any abnormalities, the infant is hospitalized for evaluation that includes respiratory and cardiac monitoring and some of the tests listed in Diagnostic Tests for Causes of Apparent Life-Threatening Event (ALTE) as indicated.

Parents and caregivers should be trained in CPR for infants and in safe infant care.

Home monitoring devices may be considered for infants with the following increased risk factors for recurrence:

  • An ALTE episode requiring CPR

  • Prematurity

  • A sibling who died of SIDS

Monitors should be equipped with event recorders and used for a predetermined period of time. Parents should be taught how to use the monitor and be advised that home monitoring has not been shown to reduce the mortality rate. Also, exposure to tobacco smoke must be eliminated.

Key Points

  • ALTEs have many possible causes; often no etiology is found.

  • Respiratory, neurologic, infectious, cardiac, metabolic, and GI disorders as well as abuse should be considered, with testing done based on clinical findings.

  • Prognosis depends on cause; risk of death is increased in children with a neurologic disorder, who have had 2 or more ALTEs, who have experienced nonaccidental trauma, or who are > 6 mo and have had an ALTE of longer duration, especially if they have heart disease.

  • Children with abnormal examination findings or laboratory results or who required intervention or had a worrisome history are hospitalized.

  • Treatment is directed at the cause; home monitoring may be done but has not been shown to decrease mortality.

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* This is the Professional Version. *