Cardiac dysrhythmias in children with idiopathic dilated or hypertrophic cardiomyopathy

To assess the incidence and prognostic significance of cardiac dysrhythmias in children with idiopathic dilated or hypertrophic cardiomyopathy, the clinical course of 59 patients was retrospectively reviewed over a period of 27 years. Dilated cardiomyopathy (DCM) was diagnosed in 28 patients and hypertrophic cardiomyopathy (HCM) in 31 patients. The mean age at the time of diagnosis was 2.8 +/- 0.7 years in DCM patients and 6.7 +/- 0.8 years in HCM patients. Mean follow-up time after diagnosis of cardiomyopathy was 4.1 +/- 1.0 years in DCM patients and 6.6 +/- 0.8 years in HCM patients. Clinically significant cardiac dysrhythmias were found in 17 of 59 patients (29%): 7 of 28 patients (25%) with DCM and 10 of 31 patients (32%) with HCM. The initial diagnosis of a cardiac dysrhythmia was made by standard electrocardiography in 12 of 17 patients (71%) and by 24-hour Holter monitoring in 5 of 17 patients (29%). Ventricular dysrhythmias were present in 5 of 7 patients with dilated cardiomyopathy and in 5 of 10 patients with hypertrophic cardiomyopathy. During the followup time, death occurred in 18 of 59 patients (31%): 8 of 59 patients (14%) died from congestive heart failure and 10 of 59 patients (17%) died suddenly. Among the sudden deaths were 4 of 28 patients (14%) with dilated cardiomyopathy and 6 of 31 patients (19%) with hypertrophic cardiomyopathy. Cardiac dysrhythmias had been documented in 6 of the 10 patients dying suddenly (3 of 4 patients with DCM and 3 of 6 patients with HCM).(ABSTRACT TRUNCATED AT 250 WORDS)

Passive smoking in childhood

There is increasing interest in the effects of adult smoking on the health of infants and children. Although passive smoking is important in many childhood disorders, most attention has been paid to its effects on the respiratory tract and on infant mortality. Several studies have reported an increased risk of sudden infant death syndrome and respiratory illness in infants of mothers who had smoked during pregnancy. Post-natal exposure to passive smoking has been found responsible for an increased risk of acute respiratory illness morbidity and an increased occurrence of chronic respiratory symptoms. Maternal cigarette smoking aggravates asthma symptoms and bronchial responsiveness in children with an established diagnosis of the disease, and the possibility that passive smoking has a causal role in the aetiology of asthma is currently a matter of growing interest. In addition, several studies have shown small but significant reductions in lung function values of children exposed to passive smoking.

Retrograde axonal cytokine transport: a pathway for immunostimulation in the brain inducing hypoxia and sudden infant death?

The etiology and pathogenesis of sudden infant death syndrome (SIDS) remain unknown. A hypothesis for SIDS should explain three characteristic findings: (a) an age distribution peaking at 2-4 months; (b) frequent association with respiratory tract infections; and (c) occurrence during sleep. The diagnosis of SIDS is applied when death cannot be explained, and this syndrome therefore probably includes various underlying causes. Based on recent observations, however, we suggest a pathogenic pathway that might be common to most SIDS victims.

Bottle feeding and the sudden infant death syndrome

OBJECTIVE

To determine whether the risk of the sudden infant death syndrome is increased in bottle fed babies.

DESIGN

Population based case-control study matching for age and time.

SUBJECTS

All babies aged 1 week to 1 year dying of sudden infant death syndrome during November 1987 to April 1989 or February 1990 to June 1991 and two live controls.

SETTING

Avon and north Somerset.

MAIN OUTCOME MEASURES

Breast or bottle feeding, sleeping position, maternal smoking, parental employment, and length of gestation.

RESULTS

Compared with being fully breast fed, the crude odds ratio for sudden infant death in fully bottle fed babies was 3.1 and for mixed breast and bottle fed babies 1.5. These odds ratios fell to 1.8 (95% confidence interval 0.7 to 4.8) and 1.2 (0.5 to 2.7) respectively after maternal smoking, parental employment, preterm gestation, and sleeping position had been adjusted for. Sleeping position partly masked the effect of being bottle fed on sudden infant death as breast fed babies were more likely to have slept prone than bottle fed babies.

CONCLUSIONS

Bottle feeding is not a significant independent risk factor for the sudden infant death syndrome. Patterns of maternal smoking, preterm gestation, and parental employment status account for most of the apparent association with bottle feeding.

[Crib death in the eastern regions of Norway 1984-1992. A survey of risk factors]

Cot death is the most important cause of death during the first year of life after the newborn period in Norway. A case control study was performed by sending questionnaires to 188 cot death parents and 475 control parents with infants matched for age, sex and time of birth. 76% of the cot death parents and 79% of the control parents completed the questionnaires. The male/female ratio of the babies in both groups was 64/36. The age distribution showed a peak between two and four months. 65% succumbed during the winter months. During the winter 32% died outdoors. This was true for only 16% of those who died during summer. A higher proportion of the cot death cases than the controls were premature (more than eight weeks). 78% of the cot death victims usually slept prone, whereas this was true for only 50% of the controls (p < 0.01). 91% of the cot death victims were found dead in a prone position. When comparing live babies during the first three months of life, significantly more cot death mothers than control mothers had stopped breastfeeding. A larger proportion of the cot death victims than the controls had had apparent life threatening events (p < 0.01). Foam mattresses were equally frequent in both groups.

Gastroesophageal reflux and acute life-threatening episodes: role of a central respiratory depression

The aim of this study was to evaluate plasma levels of beta-endorphins in babies with gastroesophageal reflux (GOR) admitted for acute life-threatening episodes (ALTE). In case of ALTE (n = 15), beta-endorphin levels were significantly increased compared to sudden infant deaths syndrome siblings with GOR of a similar gravity evaluated for risk factors (n = 13). beta-Endorphin levels are decreased following successful treatment of GOR. Studies of ventilation suggest that changes in the central respiratory drive are associated with a reduction in plasma beta-endorphin levels.

Prenatal diagnosis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in a family with a previous fatal case of sudden unexpected death in childhood

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited disease with a carrier frequency of approximately 1:100 in most Caucasian populations. The disease is implicated in sudden unexpected death in childhood. A prevalent disease-causing point mutation (A985G) in the MCAD gene has been characterized, thus rendering diagnosis easy in the majority of cases. Since the clinical spectrum of MCAD deficiency ranges from death in the first days of life to an asymptomatic life, there are probably other genetic factors--in addition to MCAD mutations--involved in the expression of the disease. Thus, families who have experienced the death of a child from MCAD deficiency might have an increased risk of a seriously affected subsequent child. In such a family we have therefore performed a prenatal diagnosis on a chorionic villus sample by a highly specific and sensitive polymerase chain reaction (PCR) assay for the G985 mutation. The analysis was positive and resulted in abortion. We verified the diagnosis by direct analysis on blood spots and other tissue material from the aborted fetus and from family members.

Loss of neonatal hypoxia tolerance after prenatal nicotine exposure: implications for sudden infant death syndrome

Maternal cigarette smoking has a high correlation with sudden Infant Death Syndrome, a condition in which cardiorespiratory failure occurs during an hypoxic episode, as in sleep apnea. Pregnant rats were given nicotine infusions of 2 or 6 mg/kg/day throughout gestation, regimens that produce plasma nicotine levels spanning the range in smokers. The day after birth, animals in the high dose group displayed excessive mortality during hypoxic challenge. These animals were found to be deficient in an essential response component, namely adrenomedullary catecholamine release that is required to maintain neonatal cardiac rhythm during hypoxia; the defect was in adrenal cell function rather than in altered innervation or nicotinic receptor desensitization. We also examined brainstem and forebrain noradrenergic mechanisms that are involved in neonatal respiratory control. The nicotine group showed suppressed spontaneous neuronal activity, but were hyperresponsive to hypoxia. As these projections are inhibitory for respiration, the nicotine-induced sensitization would be expected to contribute to respiratory arrest during hypoxia. Prenatal nicotine exposure may thus provide a useful animal model with which to study the physiological mechanisms that underlie Sudden Infant Death Syndrome, while at the same time providing a biological explanation for the association of the syndrome with smoking.

[Case studies of sudden infant death cases (SIDS)]

Parents and attending physicians of 100 SIDS victims were interviewed applying a questionnaire especially designed for this purpose. Particular attention was focussed on the courses of pregnancy and birth, medical check-ups and the infants' unusual behaviour during the last days of their lives. As far as possible we compared our data with the results of the Rhenian Perinatal Survey 1990.

[A review of recent studies investigating the relationship between sudden infant death syndrome and sleeping position]

Recent references (articles and letters) investigating relationship between sudden infant death syndrome (SIDS) and sleeping position are presented. There are many articles which have reported about this association, although repeated investigation or letters by the same researchers were contained. More than 10 epidemiological data in different area or countries were published. The vast majority of reports are retrospective case-control studies, and no study has found prone sleeping to be more common in control cases than in SIDS, although this relation has not always been statistically significant. In addition, a few intervention studies and one cohort study also showed prone sleeping position was associated with an increased risk of SIDS. The recent autopsy cases from Tokyo Medical Examiner's Office showed that most of SIDS infant whose position was recorded were found prone position, and the result was not conflict with reports from Europe and Oceania. Judging from the result of all epidemiological studies, I agree a link between the increased risk of SIDS and prone sleeping position. Health authorities in five developed countries (Netherlands, New Zealand, Australia, the UK and the USA) have advised parents not to place their infant prone to sleep. In these countries except the USA, the reduction of the incidence of SIDS has been reported. In the USA, the prone sleeping has been traditionally received and the incidence of SIDS is lower than in reports from other countries, so all SIDS researchers do not admit the risk of prone sleeping position. The reason of the association between SIDS and prone sleeping position is unknown, but some researchers have thought the mechanism is likelihood of suffocation by rebreathing or/and airway obstruction on particular type of cot, mattress, bedding or clothes. The medical examination system in Japan covers only four regions (the 23 wards in Tokyo, Yokohama, Osaka, Kobe). In almost all other regions, it is difficult to perform the reliable epidemiological study. However, we should collect more Japanese data, as far as possible, before we determine and recommend the "safer" sleeping position of Japanese infants. We need to get further information about not only sleeping position but also other infant care practices.

Relationship of sweat electrolytes to apparent life-threatening events (ALTE): a case control study

Twenty infants aged 25 days to 6 months who were consecutively investigated for apparent life-threatening events (ALTE) with negative results and 20 matched normal controls underwent an iontophoresis sweat test. A statistically significant elevated sweat potassium level (22.1 +/- 8.9 versus 12.4 +/- 6.5 mol/l) was noted in the ALTE patients compared with the control group (p < 0.001). No difference was found, however, between sweat sodium and chloride levels in the two groups. Na/K ratio in sweat was significantly different between the groups (p < 0.001). A between-groups discriminant analysis, using Na/K ratio as a discriminant variable, resulted in 80% accuracy in group assignment. A significant increase in sweat potassium concentration at night compared with day time was evident in ALTE patients. Elevated sweat potassium levels specifically characterized infants who experienced ALTE and may possibly indicate an underlying mechanism involving enhanced sympathetic activity.

The effect of nasal occlusion on the initiation of oral breathing in preterm infants

The ability to switch from nasal to oral breathing in response to nasal obstruction is crucial for survival, and has been suggested to be an important mechanism in preventing sudden infant death syndrome (SIDS). To know whether the ability to switch from nasal to oral breathing is uniformly present during the early neonatal period, we examined the effects of slow and fast nasal occlusions on the establishment of oral breathing in preterm infants. Slow occlusions were used to mimic more closely occlusions occurring spontaneously. We studied 17 healthy preterm infants [birth weight, 1830 +/- 27 g (mean +/- SE); study weight, 1800 +/- 109 g; gestational age, 32 +/- 1 weeks; postnatal age, 12 +/- 2 days]. We used a nosepiece with a nasal occluder and a flow-through system to measure ventilation. A CO2 sampling catheter at the mouth was used to detect oral breathing. Of 58 occlusions, 29 were slow [resistance increasing slowly from 0 to infinite (occlusion)], and 29 were fast (infinite elastance applied in < 1 sec). Oral breathing was always established following slow and fast occlusions. In 44% of the slow occlusions, oral breathing started before complete occlusion. Arousal was observed in 12/58 (17%) of all occlusions, occurring primarily after initiation of oral breathing. Oxygen saturation and respiratory rate decreased significantly following occlusions, from 96 +/- 0.6 to 87 +/- 1.2% and 49 +/- 2.8 to 38 +/- 2 breaths/min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The anaphylaxis hypothesis of sudden infant death syndrome (SIDS): mast cell degranulation in cot death revealed by elevated concentrations of tryptase in serum

A series of cases of sudden unexpected post-neonatal deaths from two centres in the UK have been investigated for evidence of mast cell activation using the biochemical markers tryptase and 9 alpha,11 beta-PGF2. Tryptase was selected as a possible marker because it is a component of mast cell secretory granules and, unlike histamine, it is not released from basophils. The prostaglandin 9 alpha,11 beta-PGF2 is an initial and pharmacologically active metabolite of PGD2, the major mast cell-derived cyclooxygenase product. This prostaglandin was chosen to serve as a marker of newly generated mediator release. In the study, unexplained infant deaths were associated with a higher concentration of tryptase in serum compared with cases of unexpected, but subsequently explained death. However, 9 alpha,11 beta-PGF2 was found to be an unsuitable post mortem marker in this situation. These results provide direct evidence that mast cell degranulation, possibly as a result of anaphylaxis, may be occurring around the time of death in some cases of cot death.