Asystoles during infancy recorded by home memory monitors: Benign events?

Objectives: To assess the frequency and clinical significance of asystole (sinus arrest ≤2.0 seconds) and the incidence of bradycardia in infants prescribed home cardiorespiratory monitors and to test the hypothesis that asystoles are more likely to occur in preterm infants. Design: Prospective, consecutive sample of monitor printouts. Methods: All 291 printouts from the memory monitors of 161 patients received during a 2-month period were analyzed. Setting: University hospital providing primary and referral care. Main Outcome Measures: Asystoles and bradycardias; clinical course of patients with asystoles. Results: Eight patients (5.0%) had 32 episodes of asystole lasting 2.0 to 4.3 seconds (group 1). Fifty-three patients (32.9%) had true bradycardia alarms but no asystoles (group 2). One hundred patients (62.1%) had neither asystoles nor bradycardias (group 3). Preterm infants constituted 88% of group 1 and 81% of group 2 but only 58% of group 3. Infants were more likely to be full-term in group 3 than in the other 2 groups (χ², P=.02). Birth weights were lower in group 1 than in group 3 (P<.05, 1-tailed t test). There were 479 true bradycardias; 72.2% lasted 10 seconds or less, 26.3% were longer than 10 seconds but no more than 20 seconds, and 1.5% were longer than 20 seconds. None of the 8 patients with asystoles required resuscitation for their asystoles; all survived and were tree of any life-threatening events after their monitors were discontinued and up until their first birthday. Conclusions: Asystoles occur more commonly in preterm infants; those pauses in the 2.0- to 4.0-second range seem to be benign. Studies of long-term recordings are needed to redefine asystole in both normal preterm and full-term infants. These data would help further refine current guidelines for pacemaker implantation during infancy.