Heart rate variability and apnea during sleep in Down's syndrome

Autonomic system dysfunction has been reported to occur frequently in patients with Down's syndrome (DS) and is constituted mainly by an imbalance between the sympathetic and vagal systems. The analysis of heart rate variability (HRV) during sleep is a quantitative reliable method for studying such a mechanism, but it has not yet been extensively and adequately applied in DS. In this study, HRV during sleep was evaluated in seven DS patients and in six normal controls, by also controlling for the presence of sleep apnea or arousal. The main results were an increased sympathetic function (low-frequency component of HRV) and a decreased vagal activity (high-frequency component of HRV) in DS with respect to normal controls, during apnea-free periods. Moreover, the presence of apnea, in DS, induced a further significant increase in low-frequency and very low-frequency components of HRV during sleep Stage 2. This study provides additional evidence of a brainstem dysfunctioning in DS, responsible for the abnormal imbalance between the sympathetic and vagal systems and confirms the brainstem involvement already suggested in the literature in order to explain brainstem-auditory evoked potential abnormalities and central sleep apnea in these patients.     

Childhood Discoid Lupus in Identical Twins

Abstract: We report the exceptional case of 11‐year‐old identical male twins who both developed discoid lupus erythematosus lesions. Although systemic lupus erythematosus has often been reported in identical twins, discoid lupus erythematosus has only ocassionaly been described, with only one other case in twin children, as far as we are aware.     

Adjusting Heart Rate During Sleep Using Activity Variance

In order to mimic the natural decrease in heart rate that occurs during sleep, an algorithm was devised to decrease the base rate to a programmable sleep rate. The algorithm was developed using activity and sinus rate data obtained from 18 normal subjects ranging in age from 22–80 years. The data were recorded in the event record of a "taped-on" pacemaker. The surface ECG signal was used to inhibit a pacer programmed to VVI at 45 ppm. The ECG documented the sinus rate while the accelerometer-based activity signals were recorded in an event record. An algorithm was used to estimate the smoothed acceleration variance every 26 seconds. The activity variance was stored in a histogram. Results : The lower 7/24ths of the histogram entries were primarily attributable to sleep. If the activity variance was entered into the lower 7/24ths of the histogram and the accelerometer reading was below rate responsive threshold, the base rate was switched to sleep rate. Using least mean squares to estimate optimal slope, base rate, and sleep rate, the root mean square error between activity derived heart rate and sinus rate was 12 beats/min. Conclusion : This study supports using an estimate of activity variance to automatically decrease pacing rate below programmed base rate. This decrease may be actuated during an afternoon nap or nighttime sleep.     

The independent metabolic effects of halo thane and isoflurane anaesthesia

Twelve healthy, unpremedicated women scheduled for total abdominal hysterectomy were given either isoflurane (n = 6) or halothane (n = 6) anaesthesia. They all general anaesthesia for a period of 3 h, with surgery being carried out only in the last hour. The anaesthesia consisted of thiopentone, pancuronium and a mixture of oxygen–enriched air (Fio₂ = 34%) supplemented with 1 MAC of either isoflurane or halothane. The patients were maintained normothermic, and with an arterial Sao₂ above 95% throughout the period of the study. The following measurements were made before, during and after anaesthesia (with and without surgery): oxygen consumption (Vo₂), carbon dioxide production (Vco₂); circulating concentrations of various hormones (insulin, growth hormone and Cortisol); various metabolites; selected amino acids and albumin; forearm arterio–venous concentration difference of glucose, lactate, free fatty–acids and selected amino acids (four patients in each group). Whole body Vo₂ decreased significantly by over 20% during anaesthesia (with or without surgery), P < 0.05). Although the circulating concentration of most amino acids showed little or no change during anaesthesia alone, there was a tendency for the flux of most metabolites to decrease, and this persisted during surgery (P < 0.05). During anaesthesia alone there was a twofold reduction in the plasma Cortisol concentration (P < 0.05), and a decrease in albumin concentration (P < 0.01). With the onset of surgery, plasma Cortisol concentration increased rapidly (in association with several other hormones and metabolites) but hypoalbuminemia persisted.     

Multigenetic lesions in infant acute leukaemias: correlations with ALL-1 gene status

The large majority of childhood B-precursor cell acute lymphoblastic leukaemia cases present IgH and TCRδ gene rearrangements. These rearrangements have been widely used as specific markers for monitoring minimal residual disease. However, their prognostic value still remains unclear. In order to determine whether IgH and TCRδ gene rearrangements have any influence on relapse and event-free survival (EFS), we analysed the clinical impact of these genetic characteristics in 51 B-precursor acute lymphoblastic leukaemia patients. 46/51 patients (90.2%) showed IgH gene rearrangements by Southern blot and/or polymerase chain reaction (PCR) analysis. No statistically significant associations were found between IgH gene rearrangement pattern and age, sex, WBC count, immunophenotype, risk factor, relapse or EFS. 27/41 patients (66%) showed Vδ₂Dδ₃ recombination by Southern blot and/or PCR analysis. At a median follow-up of 53 months the estimated 5-year EFS probability was 78 ± 3% for the whole group. The EFS probability among patients with a Vδ₂Dδ₃ recombination pattern in the TCRδ locus was 90 ± 3%, whereas for patients without Vδ₂Dδ₃ recombination was 39 ± 13% ( P  < 0.005).
IgH rearrangement patterns do not appear to influence relapse or EFS probability. However, TCRδ gene rearrangement patterns have a relevant impact on the relapse rate and the EFS probability. Patients with Vδ₂Dδ₃ recombination have better clinical outcome than patients without this recombination, independent of any other prognostic factors.