Ambulatory 24-hour electrocardiographic monitoring following total cavopulmonary connection.

A total of 72 patients (53 males, 19 females) in the age range 1-22 years (mean 6.4 years) who underwent univentricular repair between April 1990 and May 1997 at our institute were followed up from six months to seven years (mean 3.6 years). Twenty-four hours ambulatory electrocardiographic Holter monitoring was done in all the patients. Thirty-four out of 40 patients (85%) who underwent fenestrated total cavopulmonary connection and 25 out of 32 patients (78%) who underwent non-fenestrated total cavopulmonary connection had normal Holter recording; thus 59 out of 72 (82%) patients had normal findings. Among the fenestrated total cavopulmonary connections, three patients each had atrial tachycardia and sinus bradycardia. In the non-fenestrated group, two patients had atrial tachycardia, three had supraventricular tachycardia, one sinus bradycardia and one had intermittent ventricular tachycardia. No correlation was found between age at surgery, pre-operative morphology, cross clamp time or cardiopulmonary bypass time with post-operative arrhythmia. To conclude, post-operative arrhythmias following total cavopulmonary connection were not related to age at surgery, pre-operative morphology, cross clamp or cardiopulmonary bypass time. However, a larger patient pool and longer follow-up is required for evaluation of any definitive correlation.     

Reproducibility of heart rate measured in the clinic and with 24-hour intermittent recorders

This study was undertaken to assess the reproducibility of office versus ambulatory heart rates in 839 hypertensive subjects participating in the Hypertension and Ambulatory Recording Venetia Study (HARVEST). A 24-hour heart rate was recorded twice; this procedure was repeated three months later. Reproducibility was better for ambulatory than for office measurement, and was greater for 24-hour than for daytime heart rate, and lowest for night-time heart rate. Reproducibility of office heart rate was impaired above 85 bpm, and was poorer in subjects with more severe office hypertension. A small but significant decrease in average daytime (−1 bpm, P < 0.0001) and virtually no change in night-time heart rate (−0.3 bpm, NS) were observed at repeat recording. Heart rate reproducibility indices were related to the extent of the heart rate and blood pressure white-coat effect, but did not vary according to age, gender, body mass index, day-night blood pressure difference, or alcohol or tobacco use. Results indicate that heart rate recorded over the 24 hours has a better reproducibility than office heart rate, and could thus be a better prognostic indicator than traditional measurement of resting heart rate in the hospital setting.     

Meal-induced 24-hour profile of circulating glycated insulin in type 2 diabetic subjects measured by a novel radioimmunoassay

Increasing evidence supports a role for glycated insulin in the insulin-resistant state of type 2 diabetes. We measured 24-hour profiles of plasma glycated insulin, using a novel radioimmunoassay (RIA), to evaluate the effects of meal stimulation and intermittent fasting on circulating concentrations of plasma glycated insulin in type 2 diabetes. Patients (n = 6; hemoglobin A(1c) [HbA(1c)], 7.2% +/- 0.6%; fasting plasma glucose, 7.4 +/- 0.7 mmol/L; body mass index [BMI], 35.7 +/- 3.5 kg/m(2); age, 56.3 +/- 4.4 years) were admitted for 24 hours and received a standardized meal regimen. Half-hourly venous samples were taken for plasma glycated insulin, glucose, insulin, and C-peptide concentrations between 8 am and midnight and 2-hourly overnight. The mean plasma glycated insulin concentration over 24 hours was 27.8 +/- 1.2 pmol/L with a mean ratio of insulin:glycated insulin of 11:1. Circulating glucose, insulin, C-peptide, and glycated insulin followed a basal and meal-related pattern with most prominent increments following breakfast, lunch, and evening meal, respectively. The mean concentrations of glycated insulin during the morning, afternoon, evening, and night-time periods were 24.4 +/- 2.5, 28.7 +/- 2.3, 31.1 +/- 2.1, and 26.2 +/- 1.5 pmol/L, respectively, giving significantly higher molar ratios of insulin:glycated insulin of 18.0:1, 14.2:1, and 12.7:1 compared with 7.0:1 at night (P <.01 to P <.001). These data demonstrate that glycated insulin circulates at relatively high concentrations in type 2 diabetes with a diurnal pattern of basal and meal-stimulated release. A higher proportion of glycated insulin circulates at night suggestive of differences in metabolic clearance compared with native insulin.     

Accuracy of commercial 24-hour electrocardiogram analyzers for quantitation of total and repetitive ventricular arrhythmias

The accuracy of 2 commercial 24-hour electrocardiogram analyzers was tested for quantitation of ventricular premature complexes (VPCs). Scanner 1 was the Cardiodata Systems Mark III and scanner 2 was the Avionics Trendsetter DCG VII. Twenty-four-hour electrocardiographic recordings from 19 consecutive ambulatory patients with frequent VPCs were analyzed by each device. Results were compared with those from hand counts of complete printouts of each of the 19 recordings. For total VPCs, scanner 1 had an average error of 13% (range 0 to 58%) and scanner 2 had an average error of 24% (range (1 to 80%). Scanner 1 had an error of more than 10% for 9 of the 19 recordings and scanner 2 more than 10% for 11 of the 19 recordings. For paired VPCs, scanner 1 had a mean error of 23% (range 4 to 77%), and scanner 2 of 56% (range 34 to 79%). For nonsustained ventricular tachycardia, scanner 1 had an average error of 20% (range 8 to 41%) and scanner 2 had an error of 56% (range 34 to 78%). Thus, when recordings from consecutive ambulatory patients with frequent VPCs were analyzed, neither device was consistently accurate for quantitation of total VPCs. Both analyzers had an unacceptable error for quantitation of repetitive VPCs. All currently available devices may have comparably large errors. This possibility is confirmed by recalculation of the reported data from a third scanner.     

Urinary normetanephrine and metanephrine measured by radioimmunoassay for the diagnosis of pheochromocytoma: utility of 24-hour and random 1-hour urine determinations

To validate the clinical usefulness of recently developed normetanephrine (NM) and metanephrine (M) RIA for the diagnosis of pheochromocytoma, urinary excretion of catecholamines and these metabolites were determined in 30 normal subjects, 40 patients with essential hypertension, 30 patients who were suspected to have but ultimately proven not to have a pheochromocytoma (pheochromocytoma-suspect), and 31 patients with a surgically verified pheochromocytoma. Abnormally high catecholamine excretion (epinephrine plus norepinephrine) was found in patients with pheochromocytoma compared with that in the normal subjects and the essential hypertension group. However, 3 of 31 patients with pheochromocytoma had urinary catecholamine excretion that overlapped the values in the pheochromocytoma-suspect group. Both urinary NM and M excretion also were elevated in patients with pheochromocytoma, but in 4 of 31 patients with pheochromocytoma urinary M excretion was within the range found in 1 or more of the other groups. Total M (NM plus M) excretion of more than 5485 nmol/day (as NM) was found in all patients with pheochromocytoma, and all patients had values that were higher than the highest values in the normal subjects or the patients with no evidence of pheochromocytoma. To save time and simplify the diagnostic work-up of patients suspected of having a pheochromocytoma, we also determined the NM and M concentrations in randomly voided 1-h urine samples in 24 patients with pheochromocytomas, 31 patients with essential hypertension, and 16 normal subjects. Abnormally high total M excretion was found in all patients with pheochromocytomas, and there was no overlap with the values in the patients with essential hypertension or the normal subjects. We conclude that total M measurements in both 24-h and random 1-h urine samples are useful in diagnosing pheochromocytomas.     

Effects of ranitidine 150 mg four times a day on 24-hour intragastric acidity and 24-hour plasma gastrin concentration

Twenty-four-hour integrated intragastric acidity and 24-hr integrated plasma gastrin concentration was measured twice in 23 healthy male volunteers on the seventh day of oral dosing with placebo or ranitidine 150 mg four times a day. The study was a randomized, double-blind, placebo-controlled, two-way crossover investigation. The mean integrated 24-hr intragastric acidity during dosing with ranitidine 150 mg four times a day decreased to 32% of the placebo value (placebo 825 mmol/hr/liter; ranitidine 265 mmol/hr/liter). The mean integrated 24-hr plasma gastrin concentration during dosing with ranitidine 150 mg four times a day was 904 pmol/hr/liter compared with placebo (410 pmol/hr/liter)—an increase of 122%. The median number of hours of pH>3 during dosing with placebo and with ranitidine 150 mg four times a day were 5 and 11 hr, respectively. Ranitidine 150 mg four times a day caused a significant decrease of mean integrated intragastric acidity for each meal-related interval and also during the night.     

Streamlining 24-hour pH study for GERD: Use of a 3-hour postprandial test

At present, the ambulatory 24-hr pH test has been used as a diagnostic tool to assess gastroesophageal reflux disease (GERD) in those patients with reflux symptoms and a normal endoscopy. However, patients poorly tolerate the prolonged nature of the 24-hr test. The aim of this study was to determine whether analyzing a 3-hr postprandial period from a full 24-hr study would be as sensitive as the longer test. Data were analyzed from a standard ambulatory 24-hr pH recording. A positive test was determined if the pH was <4 for more than 4% of the study period with the probe placed 5 cm above the lower esophageal sphincter for both groups. The data were then reanalyzed by determining the percent time of pH < 4 during a 3-hr postprandial period. The results of 50 patients with a positive 24-hr test were compared with 50 patients with normal tests. The meal that was used to study the 3-hr postprandial period occurred in the late afternoon or early evening. The 3-hr postprandial test had a sensitivity of 88% when compared to the 24-hour test and a specificity of 98%. The positive predictive value was 100% for the 3-hr test, and the accuracy of this shorter test when compared with the standard 24-hour test was 95%. In conclusion the 3-hr postprandial analysis is a highly sensitive and specific test for demonstrating GERD. By using the shorter test, patient discomfort may be reduced and compliance enhanced.     

Effects of ovarian steroids on energy balance in rats fed a highly palatable diet

The effects of progesterone and estradiol on body weight, energy intake, energy expenditure, body composition, and brown adipose tissue activity were investigated in female rats fed a highly palatable diet (association of chow and full milk with sugar), which, by itself, induced an increase in food intake and energy expenditure. Progesterone and estradiol were administered in the form of implants. Ovariectomized animals were used in the estradiol studies. Energy expenditure was assessed through oxygen consumption, body composition through carcass analysis, brown adipose tissue activity through measurements of uncoupling-protein, guanosine diphosphate (GDP) binding capacity, and assay of uncoupling-protein mRNA. Body weight and food intake were increased by progesterone and decreased by estradiol. Energy expenditure was not altered by progesterone. Indirect evidence showed that estradiol increased energy expenditure, but direct measurements showed no modification. Changes in body weight under progesterone or under estradiol were not due to brown adipose tissue activity. The results indicate that ovarian hormones act on energy balance mainly by altering food intake, and possibly in the case of estradiol by increasing energy expenditure. These effects persist in rats fed a highly palatable diet, despite increases in energy intake and expenditure induced by the diet alone.     

Day-to-day variation of 24-hour intragastric acidity

Twenty-four-hour intragastric acidity was measured continuously using an intragastric electrode in 13 normal volunteers studied four times. Subjects were studied twice in the hospital and twice as outpatients. The dietary conditions were strictly controlled and the replicate studies were compared to assess the variability of such recordings of acidity. The accuracy of the technique was assessed, and a detection limit for differences was calculated for commonly used time periods. Over 24 h, during the night, during the day, and during the evening the technique is able to detect consistent changes of pH of greater than 0.1 units. During separate 5-min periods the limits of detection were considerably greater. This study demonstrates the variability of 24-h intragastric acidity and confirms that continuous monitoring is able to detect important changes of acidity under both hospitalized and ambulant conditions.     

Determinants of 24-hour Urinary Oxalate Excretion

Background and objectives: Higher levels of urinary oxalate substantially increase the risk of calcium oxalate kidney stones. However, the determinants of urinary oxalate excretion are unclear. The objective was to examine the impact of dietary factors, age, body size, diabetes, and urinary factors on 24-h urinary oxalate.Design, setting, participants, and measurements: We conducted a cross-sectional study of 3348 stone forming and non–stone-forming participants in the Health Professionals Follow-up Study (men), the Nurses’ Health Study (older women), and the Nurses’ Health Study II (younger women).Results: Median urinary oxalate was 39 mg/d in men, 27 mg/d in older women, and 26 mg/d in younger women. Participants in the highest quartile of dietary oxalate excreted 1.7 mg/d more urinary oxalate than participants in the lowest quartile (P trend 0.001). The relation between dietary and urinary oxalate was similar in individuals with and without nephrolithiasis. Participants consuming 1000 mg/d or more of vitamin C excreted 6.8 mg/d more urinary oxalate than participants consuming <90 mg/d (P trend < 0.001). Body mass index, total fructose intake, and 24-h urinary potassium, magnesium, and phosphorus levels also were positively associated with urinary oxalate. Calcium intake and age were inversely associated with urinary oxalate. After adjustment for body size, participants with diabetes excreted 2.0 mg/d more urinary oxalate than those without diabetes (P < 0.01).Conclusions: The impact of dietary oxalate on urinary oxalate appears to be small. Further investigation of factors influencing urinary oxalate may lead to new approaches to prevent calcium kidney stones.Approximately 80% of kidney stones contain calcium, and the majority of calcium stones consist primarily of calcium oxalate (1). Small increases in urinary oxalate have a major effect on calcium oxalate crystal formation (2), and higher levels of urinary oxalate substantially increase the risk for calcium oxalate kidney stones (3). Despite the importance of urinary oxalate in the pathogenesis of calcium nephrolithiasis, the determinants of urinary oxalate excretion are unclear.Because oxalate is a metabolic end-product and is excreted unchanged in the urine after absorption in the gastrointestinal tract, clinicians routinely recommend a low oxalate diet to patients with calcium oxalate nephrolithiasis (4). However, the effect of dietary oxalate on urinary oxalate is controversial. A large amount of urinary oxalate is derived from the endogenous metabolism of glycine, glycolate, hydroxyproline, and vitamin C (5,6), and estimates of the proportion of urinary oxalate derived from dietary oxalate vary widely (from 10% to 50%) (7). It is also uncertain whether stone formers have higher levels of intestinal oxalate absorption than non-stone formers (8,9).Additional factors (including body size and the intakes of calcium, magnesium, vitamin C, and vitamin B6) may influence urinary oxalate excretion by modulating endogenous oxalate production (5,6) or intestinal oxalate absorption (10), but the importance of these factors is also unclear. The results of many feeding studies may have limited applicability to free-living populations. For example, although 1000 mg of supplemental vitamin C consumed twice daily increases urinary oxalate excretion by 22% (11), the effect of lower, more commonly consumed doses of vitamin C on urinary oxalate excretion is uncertain. Previous population-based studies have been relatively small and provide conflicting results about the associations between vitamin C intake, body size, and urinary oxalate (12,13). No population-based study to date has examined the relations between urinary oxalate and the intake of individual amino acids (such as tryptophan, serine, and glycine) or specific carbohydrates (such as fructose) that may be important for oxalate synthesis (14). Finally, the impact of age and diabetes on urinary oxalate excretion is unknown.To examine the relations between specific demographic, dietary, and urinary factors and the 24-h urinary excretion of oxalate, and to determine whether these associations varied by kidney stone history, we conducted a cross-sectional study of 3348 individuals with and without a history of kidney stones from three cohorts: the Health Professionals Follow-up Study (HPFS) and the Nurses’ Health Studies I and II (NHS I and NHS II).     

Serum IRI in insulin-treated diabetics during a 24-hour period

Serum immunoreactive insulin extracted with acid ethanol (total IRI) and blood glucose were measured in two groups of diabetics and a control group during 24-hour periods. One group of diabetics had received insulin for less than 1 month, and none had yet developed insulin antibodies. The other had been treated with insulin for 2 years or more. The average level of total IRI in the diabetics without antibodies was similar to that in the normals, but highly elevated in diabetics with antibodies, although the blood glucose levels were similar in the two diabetic groups. The increase in total IRI after the insulin injections was more rapid in patients receiving quick-acting insulin and most pronounced in those with the highest levels of total IRI. The total IRI peaked in the afternoon and dropped during the night. The short-term insulin-treated patients showed a better degree of diabetes control than those treated for 2 years or more. No correlation was found however, between the total IRI level and the degree of control in the latter group. The patients with the highest levels of total IRI had the highest frequency of hypoglycemic episodes. This is in agreement with the concept that the insulin antibodies may function as a circulating depot, which releases insulin irrespective of the metabolic need.     

Effects of a 24-hour fast on cigarette smoking in humans

The effects of 24 hours of food deprivation on cigarette consumption, smoke exposure and mood were studied in seven research -volunteers. A within-subjects design was used in which subjects smoked low-yield (0.1 mg nicotine) and high-yield (0.7–1.1 mg nicotine) cigarettes in both a fed and a fasting state. Each of the four experimental conditions–FED/LOW-YIELD, FED/HIGH-YIELD, FAST/LOW-YIELD, FAST/HIGH-YIELD–was enacted twice according to a randomized block design. Cigarette consumption was measured during the 24-h period before experimental sessions. The session included a 60-min smoking period, in which number of puffs per cigarette, number of cigarettes smoked, carbon monoxide (CO) exposure and mood were assessed. Although cigarette consumption during the 24 h prior to sessions did not vary as a function of feeding condition, CO levels at the end of this 24-h time period were slightly, but significantly, higher in the FAST condition (mean CO level: 30.3 ppm) than in the FED condition (mean CO level: 28.1 ppm). During the laboratory session, amount of smoking and CO exposure were similar across feeding conditions. Interactions between feeding condition and dose were obtained on several mood measures that reflected sedation and arousal: in the high-yield condition, subjects were more sedated after fasting, whereas in the low-yield condition, they reported being less sedated after fasting. We conclude that fasting does not alter cigarette consumption but may increase smoke exposure during ad libitum smoking, perhaps via a change in some aspect of smoking behaviour not measured in the present study (e.g. puff volume).     

Heart rate-dependent alteration of the frequency and coupling interval of ventricular arrhythmias as measured by 24-hour ECG monitoring.

Twenty-four hour ECG recordings of 132 patients with frequent (greater than 1000/day) ventricular premature contractions (VPCs) were analyzed using a computerized system, designed to evaluate the relationships between 1) the VPC frequency and heart rate (HR) (VPC-HR relation), 2) the coupling interval (CI) of VPCs and HR (CI-HR relation), and 3) the incidence of ventricular tachycardia (VT) and HR (VT-HR relation). The patterns of the VPC-HR relation included: 1) an increase in VPCs with increasing HR (positive correlation, 43 patients), 2) an increase in VPCs at low HR range and a decrease at high HR range, with increasing HR (bidirectional correlation, 74 patients), 3) a decrease in VPCs with increasing HR (negative correlation, 7 patients) and 4) constant VPCs over all HRs (flat correlation, 8 patients). Patients were divided into 2 broad categories according to whether they had a positive correlation (P group, 43 patients) or the other correlations (non-positive or NP group, 89 patients). Of 132 patients, the CI-HR relation was negative in 129 (98%) and positive in only 3 (2%). Patients with frequent VTs (10 or more events over 24h) were significantly more frequent in the P (9 patients, 21%) than in the NP group (7 patients, 8%, p less than 0.05). However, mean HR, mean CI, total VPC counts and the slope of CI-HR relation were not significantly different between the groups. The VT-HR relation observed in 16 patients with frequent VTs were positive in 9 of the P group and in 2 of the NP group and non-positive in 5 of the NP group.(ABSTRACT TRUNCATED AT 250 WORDS)     

The 24-hour growth hormone secretion in a boy with giantism

The endocrinological and radiological findings in a 7.5-year-old boy with giantism are reported and compared with an age and sex matched normal tall boy. A 24-h GH profile demonstrated a persistently elevated GH concentration (mean GH concentration: giant 19.3 mU/l; tall boy 5.4 mU/l) with loss of the dominant GH periodicity of 3 h seen in the boy with tall stature and substitution with one of 8 h. These data support the view that giantism and acromegaly are similar diseases occurring prior to and following epiphyseal fusion, respectively.