Relationships between left ventricular morphology, diastolic function and oxygen carrying capacity and maximal oxygen uptake in children.

Little attention has been paid to children with respect to factors controlling maximal oxygen uptake (V.O (2max)). This study was therefore specifically designed to examine the potential relationships between cardiac size, diastolic function and O (2) carrying capacity with maximal aerobic capacity. Specifically, body size indices (body surface area, lean body mass), resting left ventricular dimensions and filling characteristics, blood haemoglobin concentration as well as V.O (2max) established during a maximal cycle exercise test were assessed in a large cohort (n = 142) of healthy 10 - 11 year old boys and girls. Results were compared between groups of low (< 50, L), moderate (50 - 60, M) and high (> 60, H) V.O (2max) (ml . min (-1) . kg (-1) of lean body mass). Moreover, potential contributors to V.O (2max) variance were investigated using univariate and multivariate regression analyses over the overall population. The major results show no differences between the 3 groups for all diastolic and systolic function indices as well as blood haemoglobin and systemic vascular resistances (used as an index of afterload). None of these variables emerged from regression analyses as potential predictors of V.O (2max.) After accounting for body size variation, heart dimensions, and especially left ventricular internal dimensions, differed between H and M and L and were associated with higher cardiac filling and subsequently stroke volume. Strong relationships between V.O (2max) and heart dimensions were noticed, due primarily but not exclusively to the influence of body size. After adjusting for lean body mass, end-diastolic diameter contributed modestly (8 %) but significantly to V.O (2max) variance, which is biologically meaningful.

Cardiovascular responses to endurance training in children: effect of gender.

BACKGROUND: The aim of the present study was to determine in healthy children the effect of a well-controlled endurance training programme on cardiac function at maximal exercise and to define whether gender affects the training-induced cardiovascular response. The contribution of factors potentially involved in those adaptations such as cardiac dimensions and diastolic and systolic function was also investigated. METHODS: Thirty-five l0-11-year-old children took part in this study: 19 children (10 girls and nine boys) were assigned to participate in a 13-week endurance training programme (3 x 1 h week-1, intensity: > 80% HR max), and 16 (seven girls and nine boys) served as a control group. A resting echocardiographic evaluation and a maximal upright cycle test, including measurement of stroke volume (SV), cardiac output (Q) and blood pressure, were performed in all children before and after the study period. RESULTS: The training programme led to a rise in maximal O2 uptake (VO2max), brought about however, only by an increase in SVmax in both genders. Moreover, the boys increased their VO2max to a greater extent than the girls (boys: +15%; girls: +8%) only because of a higher SVmax improvement (boys: +15%; girls: +11%). No alterations were noticed in the SV pattern from rest to maximal exercise, indicating that the increase in SVrest was a key factor in the improvement of SVmax and thus VO2max. Regarding resting echocardiographic data, an increase in the left ventricular end-diastolic diameter, concomitant with an improvement in diastolic function, was observed after training and constituted an essential element in the rise in VO2max after training in these children. Moreover, during maximal exercise, a decrease in systemic vascular resistances, probably indicating peripheral cardiovascular adaptive changes, might also play an important role in the increase in VO2max. CONCLUSION: Whatever gender, aerobic training increases VO2max in children, mediated by an improvement in SVmax only. Similar mechanisms, including loading conditions and cardiac morphology, seem to be involved in both genders in order to explain such an improvement.

Physical training increases heart rate variability in healthy prepubertal children.

BACKGROUND: The aim of the present study was to evaluate the effect of an endurance training program on heart rate variability (HRV) in prepubertal healthy children and to determine the relationships between HRV components and training-induced cardiac adaptations. METHODS: Nineteen prepubertal children (aged 10-11 years old) took part in this study: 12 children were assigned to participate in a 13-week endurance training program (3 x 1 h week-1; intensity, > 80% HRmax) and 7 children served as a control group. Before and after the 13-week study period, all the children were tested for maximal oxygen uptake (V O(2max)), HRV was measured by spectral and time domain analysis of 5 h night ECG recordings, and left ventricular (LV) cardiac morphology and function were assessed by means of Doppler-Echocardiography. RESULTS: V O(2max) increased significantly (+15.5% +/- 12.1; P < 0.01) after the training program. All the frequency domain components (absolute values) increased after training except the low (LF) to high (HF) frequency ratio. Also, LF and HF did not change when expressed relative to total power. For the time domain components, only N-N intervals, the standard deviation of all N-N and the average of all 5 min standard deviations of N-N increased after training. Our training program induced also an increase in LV internal diameter and mass as well as an enhancement in early diastolic passive LV filling with a concomitant reduction in late diastolic active LV filling. These cardiac morphological and functional adaptations did not correlate however, with the autonomous nervous system modifications due to training. CONCLUSION: Our study shows that an endurance training program had a positive effect on aerobic potential, morphological and functional cardiac parameters and on nocturnal global HRV in healthy prepubertal children without inducing sympathetic and parasympathetic modifications.

Central and peripheral cardiovascular adaptations to exercise in endurance-trained children.

Stroke volume (SV) response to exercise depends on changes in cardiac filling, intrinsic myocardial contractility and left ventricular afterload. The aim of the present study was to identify whether these variables are influenced by endurance training in pre-pubertal children during a maximal cycle test. SV, cardiac output (Doppler echocardiography), left ventricular dimensions (time-movement echocardiography) as well as arterial pressure and systemic vascular resistances were assessed in 10 child cyclists (VO2max: 58.5 +/- 4.4 mL min-1 kg-1) and 13 untrained children (UTC) (VO2max: 45.9 +/- 6.7 mL min-1 kg-1). All variables were measured at the end of the resting period, during the final minute of each workload and during the last minute of the progressive maximal aerobic test. At rest and during exercise, stroke index was significantly higher in the child cyclists than in UTC. However, the SV patterns were strictly similar for both groups. Moreover, the patterns of diastolic and systolic left ventricular dimensions, and the pattern of systemic vascular resistance of the child cyclists mimicked those of the UTC. SV patterns, as well as their underlying mechanisms, were not altered by endurance training in children. This result implied that the higher maximal SV obtained in child cyclists depended on factors influencing resting SV, such as cardiac hypertrophy, augmented myocardium relaxation properties or expanded blood volume.

Effect of aerobic training and detraining on left ventricular dimensions and diastolic function in prepubertal boys and girls.

PURPOSE: The purpose of this study was to determine the effect of an aerobic training program on the left ventricular (LV) cardiac morphology and function of prepubertal children. METHODS: Twenty-nine 10-11 year old boys and girls (TG) participated in a 13-week running program (3 x 1 h/week, intensity: > 80% HRmax), 26, of the same age, served as a control group (CG). M-mode, 2-dimensional and pulsed-wave Doppler analyses were performed, during resting conditions, before and after the training period (T) as well as, for TG only, after 2 months of detraining (D). RESULTS: LV internal chamber dimension increased (+ 4.6 %, p < 0.01) while wall thicknesses concomitantly decreased (-10.7%, p < 0.05) as a result of T. All cardiac morphological parameters returned to pretraining values after D. Doppler-derived measurements of LV diastolic filling performance were also significantly altered by Tand D. A significant enhancement in the early diastolic passive LV filling with a concomitant reduction in the late diastolic active LV filling were in fact obtained after T. The training-induced bradycardia (-7 beats x min(-1), p < 0.01) was probably responsible for the changes in the late characteristics of the diastolic active filling. All diastolic filling indexes returned to pretraining values after D. Systolic function indexes were not modified after either T or D. No changes were obtained for the overall LV morphological and functional variables after 13 weeks of normal life for CG. CONCLUSION: These findings indicate that cardiac morphological adaptations can occur in prepubertal children after several months of aerobic training. These alterations differ however, in some areas, to those classically reported in adults following endurance training programs where both an increase in LV size and mass exist. Our data likewise demonstrate that endurance training is able to induce favourable LV diastolic filling modifications, directed principally towards an enhancement in the early rapid filling inflow and a corresponding reduction in the atrial contribution to the total diastolic inflow.

Pathogens isolated during treatment failures in otitis.

OBJECTIVES: A prospective study in the Paris region to evaluate the clinical and bacteriologic epidemiology of acute otitis media in infants in whom oral antibiotic therapy resulted in clinical failure. METHODS: The study included 186 children with a mean age of 17.5 +/- 13.1 months. Two-thirds of them attended a day-care center and 40.8% had a history of recurrent otitis media. The most frequently prescribed prior antibiotics were amoxicillin-clavulanic acid (43% of cases), an oral third generation cephalosporin (22.6%), erythromycin-sulfisoxazole (11.8%) and a first generation cephalosporin (10.2%). The average duration of antibiotic therapy was 6.9 +/- 2.65 days. Specimens for bacterial cultures included 188 samples of middle ear fluid obtained by tympanocentesis and 37 collected from otorrhea fluid. RESULTS: One hundred forty-one samples (62.7%) from 126 children yielded 170 bacterial isolates. In 60 children (32.3%) the culture of the ear pus was sterile. Among the 170 bacterial isolates: 67 (39.4%) were Streptococcus pneumoniae (59 patients), of which 77.6% had reduced susceptibility to penicillin (PRSP with penicillin MIC > or = 0.125 mg/l); 61 (35.9%) were Haemophilus influenzae (56 patients) of which 49.2% were beta-lactamase producers; and 8 were Moraxella catarrhalis (8 patients), of which 87.5% were beta-lactamase producers. Thirty-six patients were infected by S. pneumoniae with penicillin MIC > or =1 mg/l. In our study attending day-care center (P = 0.04), temperature >38 degrees C with signs of otalgia (P = 0.02), age <2 years (P = 0.048) and prior antibiotic treatment with erythromycin-sulfisoxazole (P = 0.006) were independently predictive risk factors for patients infected with penicillin-resistant S. pneumoniae. Pneumococcal serogroups 23, 14 and 19 were predominant (25.4, 25.4 and 23.8%, respectively). Penicillin resistance was mainly associated with serogroups 23 and 14. CONCLUSIONS: Penicillin-resistant S. pneumoniae isolates are frequently responsible for therapeutic failure in cases of acute otitis media in the Paris region.

Wuchereria bancrofti filariasis in French Polynesia: age-specific patterns of microfilaremia, circulating antigen, and specific IgG and IgG4 responses according to transmission level.

The age-specific patterns of microfilaremia, Og4C3 antigenemia, anti-Brugia malayi IgG and IgG4 were assessed in 3 villages of low, medium and high transmission level for Wuchereria bancrofti filariasis. The prevalence rates for each of the 4 markers were clearly age dependent and their patterns strongly associated with the transmission level. The antigenemia prevalence rate was consistently higher than the microfilaremia prevalence rate, in all age groups. The prevalences of anti-B. malayi IgG and IgG4 responses were very similar and much higher than those of microfilaremia or antigenemia. Antibody responses reached the plateau at an earlier age and at a higher prevalence with increased intensity of transmission. For all the markers, the prevalence rates were significantly higher in males than in females.

The anterior perineal approach for pull-through operations in high imperforate anus.

Recent widespread interest in a new approach to imperforate anus is ample testimony to the difficulty of the classical operations and to the unsatisfactory results. In the early seventies, Mollard began to use an anterior perineal approach to high imperforate anus as an alternative to the sacrococcygeal pull-through. It entails a semicircular retroscrotal incision allowing direct access and visualization of the urethra and puborectalis sling. Since 1976 we have switched to the anterior perineal approach. We now have experience with 30 patients, 27 males and 3 females. Two of the females had complicated cloacal anomalies, and three teenage patients were reoperated for incontinence following previous unsuccessful pull-throughs. Of the 27 primary operations, there were 17 with an uneventful early postoperative course. There were two major and eight moderate or minor complications. There was no mortality. A 3-year follow-up is available in 14 patients. The results are good in 8, fair in 4 and poor in 2. The advantages of this technique are threefold: it allows clear visualization and precise identification of the puborectalis sling; the dissection proceeds parallel to and with constant vision of the urethra, avoiding injury to it; and it obviates the need to change the position of the patient during the procedure. This operation is easier and safer than the sacral approach, it avoids cutting through the puborectalis sling as recently described, and, finally, it respects the criteria established by Stephens.