Fructose breath hydrogen tests in infants with chronic non-specific diarrhoea

Clear fluids high in fructose (e.g., apple juice) have been incriminated for symptoms of chronic non-specific diarrhoea (CNSD), in particular in children 1–4 years of age. H₂ breath tests were performed, after ingestion of fructose (1 g/kg), in 15 patients referred with CNSD and 35 controls. All 15 CNSD children (100%) had breath peak H₂ of 20 ppm versus 49% of the 35 controls (P=0.0005). Median peak H₂ in CNSD (90 ppm, range 31–136) was significantly higher than in controls (20 ppm, range 1–139) (P<0.001). Orocoecal transit time in children with positive tests was similar in both groups. Similary, median H₂ increases during the test period had the same distribution. We demonstrated fructose malabsorption in CNSD, but found a great overlap with the control group. Our results strongly discourage the use of fructose breath H₂ tests in children suspected of CNSD. A positive test has no diagnostic value and a negative test has no clinical implications.Conclusion For clinical practice, we suggest a dietary history and a trial of appropriate measures in infants with chronic nonspecific diarrhoea, instead of performing the fructose H₂ breath test.     

Influence of short- and long-term inhalation of salbutamol on lung function and β2-andrenoceptors of mononuclear blood cells in asthmatic children

Clinical observations have shown that some asthma patients develop tachyphylaxis to -sympathomimetic drugs. As down-regulation of the number of -adrenoceptors in different human tissues after exposure to catecholamines and -adrenergic drugs is well known, we investigated whether a interrelation exists between -adrenoceptor down-regulation and clinically detectable -adrenergic subsensitivity during -sympathomimetic treatment. The following results were obtained: 1. ₂-Sympathomimetic inhalation treatment with salbutamol in therapeutic doses led to a significant downregulation of ₂-adrenoceptors and consecutive cyclic adenosine monophosphate response to isoprenaline. This effect was already detectable after short-term treatment of 3–7 days in 9 asthmatic children. 2. In the long-term study over 6 months, salbutamol inhalation in 12 asthmatic children led to a significant down-regulation of -adrenoceptor binding sites on mononuclear blood cells (MNC) from 1539±91 to 1115±99 after 14 days, remaining in this range thereafter. 3. The mean airway resistance (R_aw) of these 12 patients decreased significantly within 14 days from 8.1±0.8 to 5.7±0.5 cm H₂O/l/s to remain stable throughout the 6 months of salbutamol treatment. The differences in R_aw before and immediately after inhalation of 0.2 mg salbutamol (2 puffs) were unchanged during the study period. It is concluded, that long-term inhalative treatment with salbutamol over a period of 6 months does not result in refractoriness to -adrenergic drugs in the airways of asthmatic children, even though a significant down-regulation of ₂-receptors on peripheral MNC occurs.     

Cerebrospinal fluid 309-1309-1309-1in neonates with central nervous system infections

Beta₂-microglobulin (₂m) determination in CSF of 72 neonates who underwent a spinal tap as part of a sepsis or meningo-encephalitis workup was performed to evaluate the usefulness of this test in the diagnosis of CNS infections. ₂m was measured by enzyme immunoassay. Sixty neonates had sterile culture and normal neurological status at discharge. Twelve infants had CNS infections: 8 bacterial meningitis, 3 TORCH infections (T=toxoplasmosis, O=others, R=rubella, C=cytomegalovirus and H=herpes simplex) and 1 viral meningitis. Neonates with CNS infection exhibited significantly higher CSF ₂m levels compared to neonates with sterile culture (6.24±2.66 vs 1.74±0.5 mg/l;P<0.0001). CSF ₂m levels did not correlate with the white cell count, total protein concentration or glucose level in CSF. When serum and CSF levels were measured simultaneously, the CSF ₂m level was significantly higher than the corresponding serum level in patients with CNS infection (6.98±2.5 vs 3.2±0.25 mg/l;P<0.01). Sensitivity, specificity, and predictive values were estimated for different cut-off points. The best operational diagnostic cut-off value was 2.25 mg/l. Receiver operating characteristic curve analysis showed an appropriate trade-off between specificity and sensitivity and indicated that CSF ₂m was accurate in distinguishing between neonates with and without CNS infection.Conclusion CSF ₂m may be a useful ancillary tool in neonates when CNS infection is suspected.Presented in part at the European Society for Paediatric Research Meeting, Edinburgh, September 1993     

β2-mikroglobulin bei gesunden und nierenkranken Kindern

Zusammenfassung ₂-Mikroglobulin ist ein Plasmaprotein niedrigen Molekulargewichts (11800), das in geringen Mengen auch im Harn und Liquor vorkommt. Seine Serumkonzentration liegt bei gesunden Kindern bei 0,12±0,04 mg/100 ml, seine renale Ausscheidung bei 0,07±0,05 mg/24 Std. Bei glomerulärer Nephropathie sind die Serumspiegel bei eingeschränkter GFR erhöht, während bei tubulärer Nephropathie die Ausscheidung im Harn erheblich gesteigert ist. Es besteht eine enge Korrelation zwischen ₂-Mikroglobulin und der GFR.

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₂-microglobulin in healthy children and in children with renal diseases

₂ microglobulin is a plasma protein of low molecular weight (11800), which also appears in urine in small quantities and cerebrospinal fluid. Its serum concentration in healthy children is 0.12±0.04 mg/100 ml, its renal excretion is 0.07±0.05 mg/24 hrs. In glomerular nephropathy serum levels are augmented with diminished GFR, while in tubular nephropathy excretion in the urine is raised considerably. There is a close correlation between serum ₂ microglobulin and GFR.

     

Adrenocortical reserve of neonates born of long-term,steroid-treated mothers

Since corticosteroids have been shown to be transferred across the human placenta, prolonged administration of these drugs during gestation could be expected to suppress the response of the neonatal adrenal gland. Plasma cortisol levels, before and 30 min after the injection of ACTH (36 g/kg), were determined in six neonates who were exposed in utero to prolonged maternal administration of prednisone. The basal plasma cortisol levels of these neonates (6.15±2.57 g%; mean±SEM) were similar to values obtained in eight healthy neonates (5.19±1.36g%). The increment of cortisol levels after ACTH stimulation (16.4±2.07 g%) of the study patients was larger (P<0.01) than the change (10.3±0.82 g%) observed in six older controls. These results indicate a normal neonatal adrenal reserve after prolonged exposure to corticosteroids during fetal life.     

Fetal bile acids in congenital biliary atresia —production in the liver and clinical significance

The 1-hydroxy bile acids have been said to be fetal bile acids. These bile acids were evaluated in eight patients with congenital biliary atresia (CBA) using gas chromatography-mass spectrometry. At the time of operation 1,3,7,12-tetrahydroxy-5-cholan-24-oic acid (CA-1-ol) and 1,3,7-trihydroxy-5-cholan-24-oic acid (CDCA-1-ol) were 0.46 ± 34 g/ml and 0.72 ± 0.45 g/ml, respectively, which was significantly higher than in the control group. The percentage CA-1-ol of total bile acids showed a tendency to decrease as age advanced. The grade of hepatic fibrosis ranged from F₂ to F₃ and the values and percentages of CA-1-ol and CDCA-1-ol were relatively higher in F₂ than F₃ patients. The percentage of total bile acids gradually increased in patients without sufficient bile flow but fell sharply after Kasai's procedure in the patients with sufficient bile flow. It appears that fetal bile acids are produced in the livers of CBA patients in the same way as in fetal liver, and that production continues in patients without good bile secretion even after Kasai's procedure. These results suggest that these hydroxylases are reactivated in CBA patients.     

Hypozincaemia in febrile convulsion

To understand further the role of trace elements in the pathogenesis of febrile convulsions, serum zinc (Zn), copper (Cu), magnesium (Mg) and CSF Zn, Cu, Mg and protein levels were measured by spectrometry in patients with febrile convulsion (n=19), bacterial meningitis (n=9), viral CNS infection (n=16) and in the control groupn=10) which consisted of children with signs of meningeal irritation due to upper respiratory tract infection but normal CSF findings. Samples were obtained within 6 h after admission to hospital. Mean serum and CSF Zn levels in the febrile convulsion group were significantly lower than in the other groups (for serum Zn: 0.66±0.03 mg/l vs 0.98±0.07 mg/l, 1.06±0.08 mg/l, 1.05±0.09 mg/lP<0.05; for CSF Zn: 22.96±1.62 g/l vs 75.47 ±6.9 g/l, 50.32±5.235 g/l, 39.85 ±2.81 g/lP<0.05). A linear relationship was established between serum Zn and CSF Zn levels (P<0.001). Mean CSF Zn, Cu and protein levels in the bacterial meningitis group were significantly higher than in the other groups (for CSF Cu 63.94±6.33 g/l vs 38.77±2.70 g/l, 35.84±3.48 g/l, 33.86±2.88 g/lP<0.05; for CSF protein 0.80 ± 0.12 g/l vs 0.22±0.02 g/l, 0.53±0.08 g/l, 0.19±0.01 g/lP<0.05). In children with meningitis, the elevation of the mean CSF Zn and Cu levels may result from the breakdown of the blood-brain barrier and subsequent leakage of trace elements and protein from serum to CSF. There was no significant difference between the four groups in terms of mean serum Mg and mean CSF Mg levels.Conclusion Serum and CSF Zn levels are decreased in children with febrile seizures. Zinc deprivation may play a role in the pathogenesis of febrile seizures.     

Fruit juice malabsorption: not only fructose

Malabsorption of free fructose, when ingested in excess over glucose, is considered a significant factor in apple juice induced diarrhoea. Absorption of the carbohydrates in fruit juices was investigated by means of the hydrogen breath test in 15 healthy children aged 2.2-6.4 years, consuming 15 ml kg'of each juice with a maximum of 375 ml. Incomplete absorption was found following the ingestion of apple juice (5/5), grape juice (10/10) and bilberry juice (8/10), although the last two contain equivalent concentrations of fructose and glucose. When the same tests were repeated after yeast treatment of the juices, which leads to major reductions in fructose and glucose contents, malabsorption was found to persist. No symptoms were observed following any of the tests. Our results suggest a significant role for other carbohydrates than fructose, possibly those originating from the fruit skin, with respect to fruit juice-induced breath hydrogen excretion.     

Concurrent jejunal atresia with “apple peel” deformity in premature twins

Jejunal atresia with apple peel deformity is a rare congenital malformation that is generally believed to result from in utero vascular accidents. We report this case due to the rare occurrence of jejunal atresia with apple peel deformity affecting both members of a set of twins in whom no apparent cause for the atresia exists.     

Endorphin and cortisol responses to surgical stress in newborns and infants

The beta-endorphin (BE) response to surgical stress in newborns and infants and its relation to pituitary-adrenal dynamics during stress is still unknown. Nine newborns 5 h to 5 days of age, and 5 infants 5 to 10 months old undergoing surgery were studied. All patients were anesthetized with N₂O–O₂ and halothane. Blood samples for BE and cortisol determinations were taken preoperatively and 30 min, 12 h, and 24 h after operation for radioimmunoassay. Both BE and cortisol levels in newborns were not significantly different from those in infants preoperatively (196±85.2 pg/ml vs. 138±47.8 pg/ml for BE and 23.7±17.5 g/dl vs. 10.1±5.6 g/dl for cortisol, P >0.05). At 30 min after operation, no significant increase in BE (220±106 pg/ml) and cortisol (36.1±21.2 g/dl) was found in newborns, while significant increases (BE 493±281 pg/ml, cortisol 43.9±24.2 g/dl) were found in infants compared to preoperative levels (both P <0.05). A significant difference between groups was seen in BE but not cortisol levels 30 min after operation. Both BE and cortisol declined to preoperative values within 24 h after surgery. Our study showed significant BE and cortisol responses to surgical stress in infants, but not in newborns. Factors such as age-related differential responses to the same anesthetic technique, duration of operation, and developmental differences in stress response are considered responsible for the differences.Supported by the Research Grant of Chang Gung Memorial Hospital, CMRP No. 176.     

Evaluation of delta-aminolaevulinic acid excretion in random urine samples of children

Urinary delta-aminolaevulinic acid (-ALA) excretion was evaluated in random urine samples of 191 healthy children, aged 2–14 years, with blood lead levels <0.8 mol/l (mean ± SD: 0.34±0.13), erythrocyte zinc-protoporphyrin <70 mol/mol haem (mean ± SD: 50.4±8.0) and blood haemoglobin >6.8 mmol/l (mean ± SD: 8.2±0.5). It was found that uncorrected -ALA concentration and -ALA/creatinine ratio are age-dependent, whereas the ratio of -ALA/logarithm of creatinine concentration (mean ± SD: 55.3±13.5 mol/log mmol) is independent of age and sex. The authors recommend the use of this parameter for the assessment of -ALA excretion in random urine samples in children     

Fructose malabsorption and dysfunctional gastrointestinal manifestations]

BACKGROUND: Individuals with impaired intestinal absorption of fructose may exhibit recurrent abdominal discomfort after the ingestion of fructose-containing foods. We report on patients with this disorder in whom the diagnosis was made by the fructose hydrogen breath test. METHODS: We investigated 293 patients with recurrent abdominal pain, meteorism or diarrhea in connection with the ingestion of fruits, apple juice or soft drinks. Mixed expired air was collected before and at 30 minute intervals after a fructose load and analysed thereafter by a hydrogen sensitive electrochemical cell. Incomplete absorption of fructose was defined as a peak rise in breath hydrogen of > 20 ppm. RESULTS: 108 out of 293 patients showed an abnormal peak rise after fructose (mean 71.8 ppm, SD 31.4). This malabsorption of fructose was associated with clinical symptoms in 79 of them. Sensitivity and specificity of the fructose hydrogen breath test were 98 or 86 per cent respectively. 19 patients with an abnormal breath test and symptoms following fructose were reexamined after a load with equimolar concentrations of glucose and fructose. Hydrogen breath test was normal in all of them, none developed abdominal discomfort. CONCLUSION: A considerable number of individuals suffer from dysfunctional gastrointestinal problems due to fructose malabsorption. The fructose hydrogen breath test is a simple, sensitive and noninvasive method for the diagnosis for this disorder. Possible means of treatment are dietary fructose restriction or a modification of the diet in which fructose-containing foods are exchanged for those with equal concentrations of glucose and fructose.     

Analysis of pH dynamics in the distal esophagus utilizing pH histograms and acid clearance values

Existing scoring systems for 24-h esophageal pH recording rely heavily on total duration of acid reflux; little is known or understood of the significance of dynamic aspects of esophageal acid clearance. The 24-h pH profile and rate of acid clearance in the lower esophagus was analyzed in children with clinical features of gastro-esophageal reflux (GER). Twenty-four-hour histograms of pH and time were developed with whole-pH data obtained by 24-h pH monitoring, and values for acid clearance were calculated from actual pH curves. The acid clearance value represented the average time in seconds to recover 1 pH unit from the lowest pH to pH 4.0. Clearance values greater than 100 s/pH were considered to be abnormal. Sixty-six recordings were analyzed. Five types of pH profile were characterized: (1) a normal pattern in which esophageal pH did not fall below pH 4.0 and the acid clearance value was 67.9 ± 41.1 s/pH (mean ± SD); (2) a long-tail pattern with a moderate number of reflux episodes and rapid acid clearance. The mean acid clearance value was 78.1 ± 46.4 s/pH; (3) an intermediate pattern with esophageal pH at or near 4.0 for prolonged periods where the mean acid clearance value was significantly delayed (285.6 ± 109.8 s/pH); (4) a pseudo-GER pattern with moderate reduction in pH during reflux episodes, but with prolonged acid clearance. The mean acid clearance value was 175.1 ± 93.0 s/pH; and (5) a GER pattern; this was associated with either infrequent acid reflux and delayed acid clearance, or frequent reflux episodes and rapid acid clearance. The mean acid clearance value was 160.3 ± 113.6 s/pH. Dynamic analysis of acid clearance in the esophagus may be useful therapeutically. Correspondence to: Y. Watanabe     

Reduced pancreatic insulin release and reduced peripheral insulin sensitivity contribute to hyperglycaemia in cystic fibrosis

Traditional opinion holds that patients with cystic fibrosis (CF) develop impaired glucose tolerance or diabetes due to insulinopenia caused by fibrosis of the pancreas. However, studies on the dynamics of insulin secretion and peripheral insulin action have yielded confliciting results. We studied 18 patients with CF (9 , 9 , age 15–29 years) and 17 healthy control subjects (8 , 9 , 20–32 years). Oral glucose tolerance tests and combined i.v.-glucose-tolbutamide-tests were performed on separate days in fasting subjects. Bergman's Minimal Model was used to quantitate both peripheral insulin sensitivity (S_I) and insulin-independent glucose disposal (glucose effectiveness; S_G). Based on National Diabetes Data Group criteria, 4 patients were classified as diabetic 922%; CF-DM), 3 patients (17%) had impaired glucose tolerance (CF-IGT) while glucose metabolism was normal in 11 patients (61%; CF-NGT). Irrespective of the degree of glucose tolerance, the insulin response to oral glucose was not reduced but delayed, up to 60 min in the CF-IGT/DM group. First-phase insulin release (0–10 min) after i.v.-glucose was significantly lower in CF patients (29% of healthy controls;P<0.0001), with no difference between the CF-NGT and CF-IGT/DM groups. Insulin release following tolbutamide injection was only marginally reduced in CF patients (64% of controls). In contrast, S_I was significantly reduced in the subgroup of CF patients with abnormal glucose metabolism (CF-IGT/DM: 0.97±0.16·10^–4 l/min/pmol; control group: 1.95±0.25;P<0.05).Conclusion The early insulin release is reduced in response to i.v.-glucose, while in the oral glucose tolerance test, insulin secretion is quantitatively preserved, but delayed. Reduced peripheral insulin sensitivity is a major factor for impaired glucose tolerance and diabetes mellitus in CF patients.     

Circulating thyroid antibodies and thyroid function studies in children and adolescents with insulin-dependent diabetes mellitus

Significant high titres (1400–125,600) of circulating thoroid microsomal antibodies (MCHA) were found in the sera of 5 out of 59 non-ketoacidotic, insulin-dependent diabetic (IDDM) patients (mean age 14.5 years). Among these five patients (four females, one male), all of whom were over 11 years, two also had thyroglobulin antibodies. Increased thyrotropin (TSH) response to TRH was found in 3/5 MCHA positive patients and in 3/54 without circulating MCHA. Serum thyroxine (T₄) and free T₄ (FT₄) average values were significantly lower (P<0.01 and P<0.001) in diabetics (7.1±1.8g/dl and 10.2±3.1 pg/ml, x±SD) as compared to normal sex and age matched controls (8.9±1.9 g/dl and 12.2±2.2 pg/ml, respectively). T₄ and FT₄ values were inversely related to the duration of the disease. Subnormal T₄ values were found in six (five females and one male) patients, four of whom had subnormal FT₄ values. No patient had low triiodothyronine (T₃) and high reverse T₃ (rT₃) values, i.e. none displayed the biochemical pattern of the low T₃ syndrome described with ketoacidotic status. This indicates also a satisfactory compensation of IDDM in all the patients. At the time of study no patient (including also those with circulating MCHA and TGHA and with TSH hyper-response to TRH) showed either thyroid size enlargement or clinical features of thyroid dysfunction including impaired growth and bone age retardation.Abbreviations MCHA thyroid microsomal antibodies - IDDM insulin-dependent diabetes mellitus - TSH thyrotropin - T₄ serum thyroxine - FT₄ free T₄ - T₃ triiodo thyronine - FT₃ free T₃ - rT₃ reverse T₃ - TGHA thyroglobulin antibodies - TRH thyrotrophin releasing hormone     

IL-1β induces an exaggerated pro- and anti-inflammatory response in peritoneal macrophages of children compared with adults

Children have a lower incidence of acute lung injury (ALI) compared with adults. Because ALI appears to be the end result of systemic hyperinflammation, children may either have 1) an attenuated pro-inflammatory response or 2) an augmented anti-inflammatory response compared with adults. The purpose of this study was to determine the IL-1-induced pro- and anti-inflammatory response of pediatric vs. adult peritoneal macrophages (PMs). We hypothesized that pediatric PMs would have an enhanced anti-inflammatory response compared with adult PMs. Human PMs were collected during elective laparoscopic procedures, cultured, and stimulated with IL-1. IL-6, IL-8, IL-10, and TNF production were determined by ELISA. Statistical analyses were by ANOVA; a P <0.05 was significant. Our results showed that IL-1 induced an 11-fold increase in IL-10 production in pediatric PMs (659±103 vs. 60±25 control, P <0.05). There was no IL-10 production in IL-1-stimulated adult PMs. IL-1-induced TNF production was greater in children compared with adults (2152±166 vs. 592±188, P <0.05). Similarly, IL-1-induced IL-6 production was greater in pediatric PMs compared with adults (532±3 vs. 444±52, P <0.05). There was no difference in IL-1-induced IL-8 production in children compared with adults. The IL-10:TNF ratio after IL-1 stimulation was 0.306±0.056 in pediatric macrophages and 0.020±0.015 in adult macrophages ( P <0.01). In conclusion, IL-1-induced IL-6 and TNF production were greater in pediatric than adult PMs. Furthermore, pediatric PMs had an 11-fold increase in IL-1-induced IL-10 production, while adult PMs did not produce IL-10. Therefore, IL-1 induces both a pro- and an anti-inflammatory response in pediatric PMs, whereas adult PMs produce only pro-inflammatory cytokines in response to IL-1. The exaggerated anti-inflammatory IL-10 response in children may be an important factor in the observed differences in ALI between children and adults.Presented at the International Symposium for Pediatric Surgical Research, Marseille, France, 3 October 2003Research supported by NIH Trauma Center Grant #P50GM49222–10 and NIH Training Grant T32 GM08315–12     

Focal necroses,fatty degeneration and subendocardial nuclear polyploidization of the myocardium in newborns after β-sympathicomimetic suppression of premature labor

It has been well documented in laboratory animals that -sympathicomimetics, such as isoprenalin, can cause myocardial lesions. Other so called ₂-selective symphaticomimetic drugs, which nevertheless induced ₁-cardiostimulatory side effects, are now widely used for suppression of premature labor. We examined the hearts of 25 newborns whose mothers had been treated with -sympathicomimetics for various lengths of time (24 h to 8 weeks). Three types of lesions were detected: (1) focal subendocardial necroses (3 cases), similar to isoprenalin-induced myocardial necroses in animal experiments, (2) diffuse fatty degeneration of myocardial cells (3 cases), and (3) nuclear polyploidization in the subendocardial layer of the right ventricular wall (14 cases). However, the immediate causes of death could not be directly related to the tocolytic treatment in any of the cases.Supported by Deutsche Forschungsgemeinschaft, Grant No. Bo 395/5     

Neutrophil chemotaxis in infants delivered by caesarean section

We evaluated polymorphonuclear leucocyte (PMN) chemotaxis and cortisol levels in cord blood from 15 healthy term infants delivered by caesarean section and from 15 healthy vaginally delivered term infants. Mean neutrophil chemotaxis was significantly higher in infants delivered by caesarean section (78.3±23.4m) than in vaginally delivered infants (57.8±16.6 m;P=0.01). Mean blood cortisol level was significantly lower in infants delivered by caesarean section (9.14±2.76 g/dl) than in infants born by vaginal delivery (20.71±6.98 g/dl;P=0.0001). No relationship was found between PMN chemotaxis and blood cortisol level. The higher neutrophil chemotactic activity observed in infants delivered by caesarean section could be related to general maternal anaesthesia.     

Atypical phenylketonuria with “dihydrobiopterin synthetase” deficiency: Absence of phosphate-eliminating enzyme activity demonstrated in liver

An assay for the phosphate-eliminating enzyme (PEE) activity in liver was developed which required only 5–10 mg tissue. PEE catalyses the elimination of inorganic triphosphate from dihydroneopterin triphosphate, which is the second and irreversible step in the biosynthesis of tetrahydrobiopterin (BH₄). In the presence of substrate, magnesium, NADPH, and a sepiapterin reductase fraction from human liver, PEE catalysed the formation of BH₄ which was measured by HPLC and electrochemical detection. In adult human liver, a PEE activity of 1.02±0.134 U/mg protein (mean ±1 SD; n=5) was observed. In liver needle biopsy material from five patients with defective biopterin biosynthesis, no PEE activity was found (less than 2% and 6% of the control values, respectively). The presence of an endogenous inhibitor was excluded. In a patient who died without definite diagnosis and in a patient with -thalassaemia liver PEE activity was increased. Sepiapterin reductase activity was present in all cases. Results indicate that in dihydrobiopterin synthetase deficiency, the most frequent of the rare BH₄-deficient variants of hyperphenylalaninaemia, the molecular defect consists in a defect of PEE.Abbreviations PEE Phosphate eliminating enzyme - DHBS Dihydrobiopterin synthetase - HPLC High pressure liquid chromatography - BH₄ tetrahydrobiopterin     

Effects of β-Adrenergic Antagonists on the QT Measurements from Exercise Stress Tests in Pediatric Patients with Long QT Syndrome

It has been proposed that -adrenergic antagonist protection against cardiac events in patients with long QT syndrome (LQTS) may be related to a decrease in baseline QTc dispersion. To determine the effects of -blocker therapy on QT measurements, we evaluated the exercise tests of 25 pediatric patients with LQTS. Measurements were made of the maximum QTc interval and QTc dispersion during the various segments of the exercise test. There was no statistically significant difference between the pre--blocker and post--blocker maximum QTc interval during the supine (0.473 ± 0.039 vs 0.470 ± 0.038 sec), exercise (0.488 ± 0.044 vs 0.500 ± 0.026 sec), or recovery (0.490 ± 0.031 vs 0.493 ± 0.029 sec) phases of the exercise stress test. There was also no statistically significant difference between the pre--blocker and post--blocker QTc dispersion during the supine (0.047 ± 0.021 vs 0.058 ± 0.033 sec), exercise (0.063 ± 0.036 vs 0.063 ± 0.028 sec), or recovery (0.045 ± 0.023 vs 0.052 ± 0.026 sec) phases of the exercise stress test. Therefore, the protection that -blockers offer appears not to be related to a reduction of the baseline QTc interval or a decrease of QTc dispersion. Paper presented at the Third Annual World Congress of Pediatric Cardiology and Cardiac Surgery, Toronto, Canada, May 2001