Transient episodes of apnea and bradycardia are common in preterm infants. Pronounced asystole or sinus arrest, however, is relatively rare and the clinical significance of such events is unknown. Objective: The purpose of our study was to: (1) evaluate the prevalence of severe bradycardic and asystolic events in infants studied with polygraphic cardiorespiratory monitoring, (2) characterize these events, and (3) correlate the events with other clinical findings. Methods: A total of 583 studies were performed in 454 preterm infants at a post-conceptional age 37.4 ± 2.5 (range 34-42 weeks). Asystolic pauses were defined as no QRS complex for ≥3 s consistent with a heart rate <20 beats per minute (bpm). Severe bradycardia was defined as no QRS for ≥2 s consistent with a heart rate of 21-30 bpm. Results: Eight infants (29.5 ± 3.9 weeks' gestational age, birth weight 1,283 ± 445 g) met the criteria of having had at least 1 asystolic event (heart rate ≤20 bpm). These infants had a total of 32 episodes of bradycardia ≤30 bpm, of which 22 episodes were classified as asystole. During the asystolic episodes, the P-R interval remained unchanged in 21 of 22 episodes and prolonged in 1. One patient had non-sustained ventricular tachycardia before resumption of normal sinus rhythm. All asystolic events were associated with apnea (mean duration of 17.7 ± 9.4 s) and O2 saturations fell by 10 ± 6%. A pH probe study was available in 9 of 22 asystolic events and 6 of 10 severe bradycardic events. Gastroesophageal reflux was temporally related to only one asystolic and two bradycardic events. Clinical follow-up of these infants at a mean age of 14 months (range 1-46) reveals no symptomatic sequelae; although 1 infant died from multisystem failure associated with multiple congenital anomalies. Conclusions: Asystolic pauses occur in 1.8% of a selected population of preterm infants who have been experiencing cardiorespiratory events, are related to respiratory pauses, and appear to have a benign long-term outcome, although future study should incorporate long-term neurodevelopmental outcome.
- Asystole/severe bradycardia, definition
- Asystolic events, characterization
- Asystolic/severe bradycardic events
- Gastroesophageal reflux events
- Preterm infants, asystole/severe bradycardia
- Respiratory events associated with asystolic events