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An apparent life-threatening event is the sudden appearance of certain alarming symptoms (eg, apnea, change in color or muscle tone, coughing, gagging), typically in children < 1 yr. Causes may be digestive, neurologic, respiratory, cardiac, or metabolic. 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.

Etiology

The most common causes include

• Gastroesophageal reflux disease
• Neurologic disorders (eg, seizures, meningitis, brain tumors, abnormal brainstem neuroregulation of cardiorespiratory control)
• Infection

Less common causes include

• Cardiac disorders
• Metabolic disorders
• Upper airway obstruction

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

Diagnosis

Evaluation initially involves a thorough history, including

• Observations by the caregiver who witnessed the event (including description of changes in breathing, color, muscle tone, and eyes; noises made; and length of episode)
• 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 Table 1: Miscellaneous Disorders in Infants and Children: Diagnostic Tests for Causes of Apparent Life-Threatening Event (ALTE)) are done to check for possible causes. Some are routinely obtained and others done only based on history and physical examination findings.

Table 1
Diagnostic Tests for Causes of Apparent Life-Threatening Event (ALTE) Tests Possible Causes Typical Initial Testing Blood tests, typically including CBC and differential Electrolytes (Mg, Ca, Na, K), bicarbonate, and glucose Liver function tests Acidosis Anemia Dehydration Infection Liver disorders Metabolic disorders Chest x-ray Cardiomegaly Infection Cultures (blood, stool, urine) Infection ECG, and cardiac monitoring in hospital Arrhythmias QT abnormalities Lumbar puncture Meningitis Skeletal survey Fractures Toxicology screen Overdose Urinalysis Infection Additional tests based on clinical suspicion ABGs Acidosis Brain imaging Trauma, hemorrhage EEG Seizures Esophageal pH monitoring* Gastroesophageal reflux disease Nasal swab Respiratory syncytial virus infection Pertussis blood tests and cultures Pertussis Serum lactate Hereditary enzyme defects (eg, glycogen storage disease type I, fatty acid oxidation defects, multiple carboxylase deficiency, methylmalonicaciduria) Hypoxia 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

Prognosis depends on the cause of ALTE. That is, risk of death is higher if the cause is a serious neurologic disorder. The relationship of ALTE to 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 Back to Sleep campaign.

There seem to be no long-term effects on development.

Treatment

The cause, if identified, is treated. If infants have required resuscitation or if evaluation has detected any abnormalities, infants are hospitalized for evaluation and monitoring that includes respiratory and cardiac monitoring and some of the tests listed in Table 1: Miscellaneous Disorders in Infants and Children: 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 depending on risk of recurrent episodes. 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.

Last full review/revision March 2009 by Elizabeth J. Palumbo, MD

Content last modified March 2009