Bradycardia In Preterm Infants Research Articles

A thickened formula reduces feeding-associated oxygen desaturation and bradycardia in preterm infants.

Although preterm infants often experience desaturation or bradycardia during oral feeding, specific guidelines for its management are lacking. This study aimed to investigate the effects of a commercial thickened formula (TF) on oxygen saturation and heart rate stabilization during oral feeding in preterm infants. This retrospective study included 122 infants born at a median (interquartile range [IQR]) 31+6 weeks (29+4 -34+6 weeks) of gestation weighing 1,725 g (1,353-2,620 g) and fed commercial cornstarch-containing TF due to feeding-associated desaturation or bradycardia. We excluded infants fed TF to treat symptomatic regurgitation. Desaturation and bradycardia events were compared between 3 days prior to the change and 3 days after the change to TF. Desaturation and bradycardia were defined as SpO2 <85% and heart rate <100 beats/min during or immediately after oral bottle feeding, respectively. The median (IQR) postmenstrual age and weight were 36+1 weeks (34+6-38+0 weeks) and 2,395 g (2,160-2,780 g), respectively, at the time of change to TF. The frequency of desaturation significantly decreased after TF feeding (median [IQR]: 2.3 [1.3-3.3] events/day vs. 0.3 [0-1.7] events/day, P< 0.001). Bradycardia also decreased after TF feeding (0.3 [0-1] events/day vs. 0 [0-0.7] events/day, P=0.006). There were no cases of diarrhea or electrolyte abnormalities after TF feeding. Defecation frequency decreased (P=0.037), and polyethylene glycol was prescribed to 27% of the TF-fed infants. In a subgroup analysis of 16 infants with bronchopulmonary dysplasia, the frequency of desaturation was reduced (2.3 [1.8-3.8] events/day vs. 0.5 [0-1.5] events/day, P=0.042), and weight gain improved (22.5 [3.1-36.3] g/day vs. 41.3 [28.1-55.1] g/day, P=0.019), after TF feeding. TF feeding significantly reduces oral feeding-associated oxygen desaturation and bradycardia in preterm infants. TF may be useful for stabilizing oxygen saturation and heart rate among preterm infants with difficulties in oral feeding.

Prediction of bradycardia in preterm infants using artificial neural networks

Bradycardia is common in preterm infants and associated with a range of adverse outcomes, including end organ damage and developmental problems. This paper proposes a method to develop a generalised model to predict the onset of bradycardia in preterm infants by monitoring vital signs using artificial neural networks (ANN). Data used for network development was collected from a study conducted at the Royal Hobart Hospital involving 31 preterm infants, and comprising 3591 h of electrocardiogram (ECG) and respiratory motion recordings. ANNs with a multilayer perceptron architecture were employed with features from the ECG and respiratory signals as inputs. The ANN was trained to predict bradycardia within a pre-bradycardia period beginning 15 s prior to each bradycardic event. The ANN’s prediction capability was assessed using the area under the curve (AUC) of the receiver operating characteristic. Heart rate variability and respiration patterns were found to be indicative markers of an impending bradycardic event. When applied to new infants, the ANN using only ECG features achieved a mean AUC of 0.63, and the ANN using both respiratory features and ECG features achieved a mean AUC of 0.69. This approach has improved on previous attempts to predict bradycardia and should be further investigated.

Real-Time Bradycardia Prediction in Preterm Infants Using a Dynamic System Identification Approach

AbstractChronic bradycardia, or slowing of heart rate, is common in preterm infants, and may often lead to neuropsychiatric disorders, developmental problems, and impaired cognitive functions in the long term. Therefore, early detection and treatment of bradycardia is important. To this end, we present a system identification-based approach to the prediction of bradycardia in preterm infants. This algorithm is based on the notion that the cardiovascular system can be treated as a dynamic system, and that under bradycardia, this system reacts abnormally due to temporal and spatial destabilization. This paper presents a proof-of-concept of the proposed methodology by testing its performance using electrocardiogram (ECG) data collected from ten preterm infants. We show that the proposed algorithm is correctly able to predict bradycardia occurrences (mean area under the receiver operating characteristic (ROC) curve = 0.782 and variance = 0.0039) while minimizing the training or burn-in period. The physical interpretation of the results using the system dynamics approach is discussed. The developed algorithm performs well on not only classifying normal to abnormal conditions, but also showing a trend of transition between the two conditions. Future work is also discussed to further improve the algorithm and implement the algorithm in the neonatal intensive care unit. Our proposed method is able to predict bradycardia using only ECG data with minimal training period and can be integrated into an automated system for bradycardia detection and treatment, and therefore, reduce the risks related to bradycardia in preterm infants.

Physiological instability after respiratory pauses in preterm infants.

The factors influencing the severity of apnea-related hypoxemia and bradycardia are incompletely characterized, especially in infants receiving noninvasive respiratory support. To identify the frequency and predictors of physiological instability (hypoxemia-oxygen saturation (SpO2 ) <80%, or bradycardia-heart rate (HR) < 100 bpm) following respiratory pauses in infants receiving noninvasive respiratory support. Respiratory pause duration, derived from capsule pneumography, was measured in 30 preterm infants of gestation 30 (24-32) weeks [median (interquartile range)] receiving noninvasive respiratory support and supplemental oxygen. For identified pauses of 5 to 29 seconds duration, we measured the magnitude and duration of SpO2 and HR reductions over a period starting at the pause onset and ending 60 seconds after resumption of breathing. Temporally clustered pauses (<60 seconds separation) were analyzed separately. The relative contribution of respiratory pauses to overall physiological instability was determined, and predictors of instability were sought in regression analysis, including demographic, clinical and situational variables as inputs. In total, 17 105 isolated and 9180 clustered pauses were identified. Hypoxemia and bradycardia were more likely after longer duration and temporally-clustered pauses. However, the majority of such episodes occurred after 5 to 9 second pauses given their numerical preponderance, and short-lived pauses made a substantial contribution to physiological instability overall. Birth gestation, hemoglobin concentration, form of respiratory support, caffeine treatment, respiratory pause duration and temporal clustering were identified as predictors of instability. Brief respiratory pauses, especially when clustered, contribute substantially to hypoxemia and bradycardia in preterm infants.

Bradycardias are associated with more severe effects on cerebral oxygenation in very preterm infants than in late preterm infants

BackgroundCommonly the magnitude and frequency of bradycardia is underestimated in the neonatal unit due to the long averaging time used in bedside oximeters. We aimed to assess the frequency and severity of bradycardia in preterm infants using the lowest averaging time (2 s) available on a clinical oximeter, compared with bradycardia detected using electrocardiogram (ECG), and whether bradycardia severity and postmenstrual age affected cerebral oxygenation. MethodsPreterm infants (10 M/9F) were studied longitudinally at 26–31 (very preterm) and 32–38 weeks (late preterm) postmenstrual age. Heart rate falls calculated from ECG were used to determine mild or moderate/severe (MS) bradycardias. Cerebral tissue oxygenation index (TOI, %) was recorded and fractional tissue oxygen extraction (FTOE) calculated. ResultsOf the 615 bradycardias scored using ECG criteria, 10% were not detected by oximetry. TOI falls associated with bradycardias were greater for MS bradycardias compared with Mild for both groups (p < 0.001 for both). The FTOE associated with MS bradycardias was higher for the very preterm compared with the late preterm group (p < 0.001). In very preterm infants 61% of MS and 35% Mild bradycardias were associated with TOI nadirs below 55%. ConclusionEven the most sensitive oximeter setting underestimates bradycardias. The cerebral effect from bradycardias in very preterm infants is more severe than in late preterm infants. Even the mild bradycardias are associated with falls in cerebral oxygenation. Routine NIRS monitoring of cerebral oxygenation in NICUs may increase staff awareness for interventions to reduce the repetitive falls in cerebral oxygenation in preterm infants.

Comparison of ECG detected and oximetry detected bradycardia in preterm infants

Comparison of ECG detected and oximetry detected bradycardia in preterm infants

Myocardial function during bradycardia events in preterm infants

BackgroundTransient bradycardia episodes are common in preterm infants and often secondary to apnea. Decreased ventilation with resultant hypoxemia is believed to be the predominant mechanism. Sudden bradycardias without apnea are also reported, possibly due to vagal stimulation. Point of care ultrasound is used to diagnose and follow cardiovascular complications in preterm infants. Inadvertently, the operator would sometimes capture bradycardia events. This study reports on left ventricular function during such events. MethodsWe retrospectively reviewed our cardiac ultrasound database for bradycardia events. Apical four or three chamber images before, during and after a bradycardia event were analysed with speckle tracking software which provides systolic and diastolic parameters of myocardial motion, deformation and volume. ResultsOver a 2year period, 15 bradycardia events were noted in 14 patients with a median gestational age of 26weeks (range 23 to 29). Heart rate decreased by an average of 43% (171/min to 98/min). Myocardial velocity and longitudinal strain rate during the atrial component of diastole were reduced during bradycardia. Longitudinal strain during systole was increased and radial deformation was unchanged. Ventricular volumes and ejection fraction did not change. Most parameters returned to baseline values after the event. Longitudinal systolic strain rate remained lower and stroke volume was 12% higher compared to baseline. ConclusionParameters of systolic contractility and stroke volume were maintained and parameters of atrial contractility were reduced during mild to moderate bradycardia in preterm infants. Bradycardia reduces total cardiac output with a compensatory increase detected following the event.

A Randomized Controlled Trial on the Effect of Earmuffs on Intermittent Hypoxia and Bradycardia in Preterm Infants

Irregular breathing causing hypoxia and bradycardia is a common problem of preterm infants but its pathophysiology is incompletely understood. Agitation provoked by environmental noise may play a role. We wanted to know if earmuffs can at least halve the rate of intermittent hypoxia in premies. In this randomized controlled trial 31 infants (14 male; median [min.-max.] birth weight and gestational age: 1 323 g [560-1 990] and 30(1/7) weeks [25(5/7)-33(0/7)]) had the effect of earmuffs on the frequency of pulse oximeter desaturations (SpO(2) <80%) and bradycardia events (<80 beats per minute) tested, documented via a standard home monitor. Infants were measured 2 h each with or without earmuffs; the sequence of intervention was randomised. Measurement conditions were kept constant while a noise meter recorded sound pressure levels at a 1 Hz sampling rate. Median sound pressure level was 46.8 dB(A). In a pre-study, ear muffs yielded a sound reduction by 7.2 dB. 19 infants had a total of 474 desaturations. The median (25.-75. percentile) number of desaturations was 1 (1-10.5) without, and 1 (1-10) with earmuffs. The amount of infants with at least one desaturation was equal in both treatment protocols. Only 7 bradycardias occurred. The earmuffs had, in a rather quiet environment, no effect on intermittent hypoxia in these infants.

Cerebral Oxygenation during Intermittent Hypoxemia and Bradycardia in Preterm Infants

Background: Episodes of hypoxemia and bradycardia frequently occur with apnea of prematurity in preterm infants. Little is known about the impact of different event types on the brain. Objectives: To describe the influence of hypoxemia and bradycardia, either isolated or in combination, on cerebral oxygenation. Methods: In 16 preterm infants with intermittent hypoxemia and/or bradycardia, cerebral tissue oxygen saturation (StO₂, as measured by near-infrared spectroscopy), heart rate and pulse oximetric saturation (SpO₂) were recorded simultaneously for 16 h. Events were classified as isolated bradycardia (type 1), isolated hypoxemia (type 2) or combined (simultaneous, type 3; bradycardia first, type 4; hypoxemia first, type 5). Primary outcome was a score representing the area below baseline for cerebral StO₂ desaturation during an event. Secondary outcomes were duration and depth of cerebral desaturation. Results: Patients had a median (range) gestational age of 25.9 (22.6-30.4) weeks and a postnatal age of 32.5 (7-58) days. The median (quartiles) number of events was 49 (34-58). Isolated hypoxemias were the most frequent events (24; 9-36) and isolated bradycardias the least common (0; 0-1). Cerebral StO₂ baseline was not different between event types. Cerebral desaturation score, duration of event and depth of cerebral desaturation were smallest for isolated bradycardias and largest for combined events, especially for those starting with hypoxemia followed by bradycardia. Regardless of event type, 12/16 infants maintained cerebral StO₂ >60% despite severe SpO₂ desaturations. Conclusions: Isolated bradycardias had the lowest impact on cerebral desaturation, and combined events had the highest. Most infants preserved cerebral oxygenation >60% during events.

790 Effect of Phototherapy on Episodes of Apnea and Bradycardia in Preterm Infants Breathing Spontaneously

Background and AimsWe asked whether rates of apnea and bradycardia increase during phototherapy in preterm infants breathing spontaneously.MethodsPreterm infants (n=60, median gestational age 29 weeks (range 24–32), birth weight 1205...

The Impact of Oral Sucrose on Apnea and Bradycardia in Preterm Infants: A Crossover Randomised Trial

Background and Aims: Apnea of prematurity is a common problem in preterm infants. Pain and stress promote its occurence. Oral sucrose has been shown to reduce pain in neonates. We aimed to investigate the effect of oral sucrose on the prevention of apnea and bradycardia.Methods: In this prospective, randomised controlled trial, 20 preterm infants with recurrent idiopathic apnea of prematurity treated with coffein and nasal CPAP were randomly assigned into 2 groups: Group 1 received 0.2 ml sucrose in the first night before every handling or clinically indicated diagnostic intervention and 0.2 ml sterile water in the second night, Group 2 in inverse order. Primary outcome were the occurence of desaturation events < 80% (Index of desaturation 80; DI 80) and of bradycardia < 80/min (Index of bradycardia 80, BI 80) per hour of monitor recording. Secondary outcome parameter was the apnea score (Poets C., Acta Paediatr. 2010) specified by nurses during the two nights (= 9 hours per night).Results: Neither the difference between sterile water and sucrose in the numbers of desaturations (p=0.8) and bradycardia (p=0.18) or the apnea score (p=0.8) was statistically significant.Conclusion: The administration of oral sucrose for the prevention of stress and pain did not reduce the incidence of apnea of prematurity.

Transpyloric tube feeding in very low birthweight infants with suspected gastroesophageal reflux: impact on apnea and bradycardia

OBJECTIVEOur aim was to assess safety and efficacy of transpyloric tube feeding as a therapeutic option to reduce apnea and bradycardia in hospitalized very low birthweight infants with clinical signs suggestive of gastroesophageal reflux.PATIENTS AND METHODSThis was a retrospective single center cohort study of VLBW infants hospitalized from 2001–2004 with signs of GER who received transpyloric enteral tube feedings. Apnea (>10 sec) and bradycardia (<100 bpm) episodes were compared before and after the initiation of transpyloric feedings. The Wilcoxon signed-rank test was used to compare differences between cardio-respiratory episodes before and after treatment at 1-day and combined 3-day intervals. Events recorded to assess safety of transpyloric feedings included death, sepsis, and necrotizing enterocolitis.RESULTS72 VLBW infants with a median birth weight of 870 grams (range 365–1435g) and gestational age of 26 weeks (23–31weeks) were identified. Median weight at initiation of transpyloric feedings was 1297 grams (820–3145g) and infants received transpyloric feeds for median duration of 18 days (1–86days). After initiation of transpyloric feedings, a reduction in apnea episodes from 4.0 to 2.5 (P=0.02) and a decrease in bradycardia episodes from 7.2 to 4.5 (P<0.001) was observed when comparing total number of episodes for the 3 days before and after treatment. Five (6.9%) of the infants developed necrotizing enterocolitis while receiving transpyloric feedings. None of the infants receiving human milk (P=0.07) and 36% of those receiving hydrolysate based formula (P<0.01) during transpyloric feeds developed NEC. No infants had late-onset culture proven sepsis. Seven (9.7%) infants died prior to hospital discharge.CONCLUSIONSTranspyloric feedings, especially when limited to human milk, may safely reduce episodes of apnea and bradycardia in preterm infants with suspected gastroesophageal reflux. Prospective randomized studies are needed to determine the biologic impact of bypassing the stomach, as well as the safety and efficacy of this intervention. Results of such studies could modify the current prevailing safety concerns regarding transpyloric feeding in this population.

Asystole and Severe Bradycardia in Preterm Infants

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.

Apnoea and bradycardia in preterm infants following immunisation with pentavalent or hexavalent vaccines

There is a lack of data regarding the incidence and clinical significance of apnoea or bradycardia (AB) following immunisation with combination vaccines containing an acellular pertussis (Pa) component in respiratory stable preterm infants. Medical records of respiratory stable preterm infants who received a first dose of a combined diphtheria (D) and tetanus (T) toxoids, Pa, Haemophilus influenzae type b (Hib), inactivated poliovirus (IPV) vaccine with or without hepatitis B virus (HBV) in the neonatal intensive care unit (NICU) of the University Children's Hospital Basel between January 2000 and June 2003 were analysed. For each infant, clinical data were recorded for a 72 h period before and after immunisation. Of 53 infants with a mean gestational age of 28 weeks, 7 (13%) showed a transient recurrence of or increase in episodes of AB following immunisation. Five of these seven infants required intervention ranging from tactile stimulation to bag and mask ventilation. Regarding risk factors, children with recurrent or increased AB were indistinguishable from those without such events. The rate of fever (>38 degrees C) following immunisation was higher in affected infants compared to those without recurrence of or increase in AB (3/7 vs 2/46, P = 0.01). Although most infants tolerated immunisation well, the incidence of recurrent or increased apnoea or bradycardia in respiratory stable preterm infants following the first immunisation with penta- or hexavalent vaccines was 13%. Most apnoea or bradycardia events required intervention but did not have serious consequences. Monitoring of all preterm infants following immunisation in the neonatal intensive care unit is recommended.

Suivi du prématuré: prévention des malaises graves et de la mort subite. Place de la polysomnographie

Incidence and severity of apnea and bradycardia in preterm infants may be related to the immaturity of the respiratory control mechanisms. In addition, there is a steadily increasing risk for sudden death with decreasing birth weight or gestational age during the first year of age, justifying the search for a specific preventing strategy for very low birth weight (VLBW) infants. The purpose of this paper is to define practical preventive guidelines for VLBW infants at the time of discharge from the neonatal intensive care units. Polysomnography appears as a useful method to detect those among the VLBW infants who are at risk of life threatening events and may need home monitoring.

L'arrêt de l'alimentation orale favorise-t-il la survenue d'un bloc auriculoventriculaire chez les prématurés traités par diphemanil?

Background. — Bradycardia in preterm infants may require anticholinergic therapy (diphemanil methylsulphate). Such treatment may cause prolongation of QT interval and auriculoventricular block. Case reports. — Three premature infants born before 34 weeks of gestational age were given 6–8 mg/kg/d diphemanil because they suffered from bradycardic episodes. Aggravation and/or persistence of bradycardia required withdrawal of gavage feeding: heart block occurred within a few hours which subsided after cessation of diphemanil and oral refeeding. Diphemanil at progressive dosage was later reintroduced safely in two of these infants. Conclusion. — The short interval of time between the oral feeding withdrawal and occurrence of heart block justified therapy be stopped or transiently reduced whenever oral feeding must be interrupted.

Incidence of apnoea and bradycardia in preterm infants following triple antigen immunization.

Ninety-seven preterm infants were immunized with diphtheria-tetanus-pertussis (DTP) prior to discharge from hospital. The mean gestational age at birth was 28.1 weeks (range 24-34) and the mean age at immunization was 80.6 days (range 44-257). Nineteen (20%) infants developed apnoea or bradycardia within 24 h of immunization. The infants who developed apnoea and/or bradycardia had a younger gestational age at birth than those who did not (P = 0.03), were artificially ventilated for longer (P = 0.01) and were more likely to have a diagnosis of chronic lung disease (P = 0.006). In the majority of infants these events were not clinically significant. Two infants who developed concurrent upper respiratory tract infections required additional oxygen and one of them was treated with oral theophylline. In general, it is safe practice to immunize preterm infants with DTP unless otherwise contraindicated. However, it is recommended that cardiorespiratory function is monitored after immunization in very preterm infants who had prolonged ventilatory support and/or chronic lung disease.

The relationship between bradycardia, apnea, and hypoxemia in preterm infants.

The pathogenesis of bradycardias in preterm infants is poorly understood. Because their pathogenesis may involve both apnea and hypoxemia, we set out to analyze the proportion of bradycardias that were associated with an apneic pause and/or a fall in arterial oxygen saturation (SaO2), and the temporal sequence of the three phenomena, in overnight tape recordings of SaO2 (Nellcor N100 in beat-to-beat mode), breathing movements, nasal airflow, and ECG in 80 preterm infants at the time of discharge from hospital. A bradycardia was defined as a fall in heart rate of > or = 33% from baseline for > or = 4 s, an apneic pause as a cessation of breathing movements and/or airflow for > or = 4 s, and a desaturation as a fall in SaO2 to < or = 80%. A total of 193 bradycardias were found in 46 (58%) of the recordings (median, three per recording; range 1-18). There was a close relationship between bradycardias, apneic pauses, and desaturations: 83% of bradycardias were associated with apneic pauses and 86% with desaturations. Where all three phenomena occurred in combination, the time from the onset of apnea to the onset of the fall in SaO2 was shorter (median interval, 0.8 s; range -4.9-+ 11.5 s) than that from the onset of apnea to the onset of bradycardia (median, 4.8 s; range -4.0-+ 14.0 s). Hence, most bradycardias (86%) commenced after the onset of the fall in SaO2. We conclude that bradycardia, apnea, and hypoxemia are closely linked phenomena in preterm infants.

Home monitor follow-up of persistent apnea and bradycardia in preterm infants.

We reviewed our experience with home monitor observations of 83 preterm infants (postconceptional age, 36 to 44 weeks) who had persistent apnea, bradycardia, or cyanosis. Polygraphic recordings before discharge showed that 92% of these infants had cardiorespiratory abnormalities that included prolonged (greater than 20 s) apnea, excessive periodic breathing (greater than 15%), bradycardia (greater than 80 beats per minute), feeding hypoxemia, or elevated carbon dioxide values. At home, 70 infants had either no alarms or alarms that resolved spontaneously, while 13 (16%) had more serious episodes that required parental intervention, including mouth-to-mouth ventilation in one infant. While polygraphic studies were helpful in documenting specific cardiorespiratory abnormalities, neither these abnormalities nor the clinical characteristics of the infants identified those infants experiencing subsequent home monitor alarms requiring parental intervention. Our data suggest that some preterm infants with persistent episodes of apnea, bradycardia, and cyanosis beyond 36 weeks of postconceptional age remain at risk for future serious episodes for several months.

Undetected Episodes of Prolonged Apnea and Severe Bradycardia in Preterm Infants

Twenty-four-hour tape recordings of ECG and breathing movement were made on 14 preterm infants with prolonged apneic episodes. Despite apnea monitoring systems, 136/203 (67%) apneic episodes greater than or equal to 20 seconds in duration, including 19 episodes greater than or equal to 50 seconds in duration, were not recorded by nursing staff. Of 120 apneic episodes greater than or equal to 30 seconds, 100 (89%) were accompanied by bradycardia less than or equal to 100 beats per minute. Episodes of more marked bradycardia (less than or equal to 80 beats per minute and up to seven minutes in duration) occurred without cessation of breathing movement in 10/14 infants studied. Treatment with theophylline or aminophylline was associated with a reduction in the number of episodes of apnea greater than or equal to 20 seconds accompanied by bradycardia less than or equal to 80 beats per minute (P less than .001). Many prolonged episodes of apnea and bradycardia are going unnoticed in neonatal intensive care units. Further studies are required to investigate and overcome the causes of these failures.