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At least 649 records · Page 36Linked to original sources
PubMed1987

Fundamental differences between the standard 12-lead electrocardiograph and the modified (Mason-Likar) exercise lead system.

A comparison of the standard 12-lead electrocardiograph with the Mason-Likar lead system widely used for exercise stress testing shows that the two are not 'essentially identical' as was originally claimed. Placement of the limb electrodes onto the torso distorts the electrocardiograph causing a rightward shift of the mean QRS axis, a significant reduction in R-wave amplitude in leads I and aVL, and a significant increase in R-wave amplitude in leads II, III and aVF; the R-wave amplitude of the chest leads is also altered. The so-called 'inferior' leads on the exercise electrocardiography are probably modified anterior/inferior leads, since their R-wave amplitudes correlate closely with those of antero-lateral chest leads. The inferior surface of the heart is not represented in isolation on the exercise electrocardiograph, thus explaining the reported inability of the exercise test to predict the location of coronary artery disease and high incidence of false negative tests in patients with ischaemia limited to the inferior cardiac surface.

Coronary Disease↗
PubMed1996

Activated pyrolytic carbon tip pacing leads: an alternative to steroid-eluting pacing leads?

Pyrolytic carbon technology is known for its excellent mechanical properties and electrical conductivity; it is particularly biocompatible and does not require high production costs. The Sorin S100/4 lead is a ventricular passive fixation lead with a hemispherical electrode surface area of 4 mm2; the stimulating tip is made of a graphite core coated by a thin activated pyrolytic carbon layer. We evaluated the acute and medium-term performance of the unipolar version of this lead in 65 patients. At implantation, pacing threshold (at 0.5 ms) was 0.26 +/- 0.08 V; pacing impedance (at 5 V and 0.5 ms) was 537 +/- 94 omega and R wave amplitude was 15.0 +/- 5.5 mV. No lead related complications (dislodgment, perforation, exit block, etc.) occurred in any patient; one patient presented with a wire fracture after 26 months, due to subclavian crush syndrome. Follow-up procedures were performed at 1 week, and 2-, 10-, 18-, and 30-months postimplant. Since the leads were connected to pacemakers from different manufacturers, either voltage or duration thresholds were measured. In approximately two thirds of the patients, with an output of 2.5 V, a mean duration threshold of 0.16 +/- 0.13 ms at 1 week, 0.12 +/- 0.08 ms at 2 months, 0.11 +/- 0.06 ms at 10 months, 0.09 +/- 0.06 ms at 18 months, and 0.07 +/- 0.03 ms at 30 months, was measured. In the remaining one-third of the patients, a comparable voltage threshold trend was measured. The mean pacing impedance showed a transient drop at 1 week, and then increased to a plateau of about 600 omega reached after 10 months. No sensing defect occurred in any patient. Our data show good acute and intermediate-term results of the S100/4 lead; the early rise in threshold was remarkably blunted. Activated pyrolytic carbon tip leads might therefore be considered as a possible, inexpensive alternative to steroid-eluting leads.

Aged↗
PubMed1998

Bipolar active fixation atrial leads: comparison of two new lead models.

The purpose of the study was to examine the pacing and sensing characteristics of two bipolar active fixation atrial leads with a coaxial and a coradial conductor design, respectively. One group of ten patients received the ELA model S44F (4 mm2 vitreous carbon tip, coaxial multifilar coils, silicone). Nine other patients received the Intermedics ThinLine EZ 438-10 (8 mm2 iridium oxide-coated titanium tip, parallel-wound bifilar coil, polyurethane). Both lead models had electrically insulated corkscrews. Intraoperatively, pacing threshold (PT) at 0.50 ms, unfiltered atrial potential (AP), slew rate (SR) and pacing impedance (Z) at 2.5 V, 0.50 ms were measured using a Medtronic 5311 PSA. On the day of implant, and 2, 5, 10, 28, 90, 180, and 360 days after implant, minimum charge threshold (delta Qmin), atrial sensing threshold (Asen) and Z were measured via telemetry of the pacemaker (Intermedics 294-03 and 294-09). Z was significantly lower (P < 0.01) in the ThinLine EZ group at implant (419 omega vs 576 omega, mean values, 438-10 vs S44F) and at each follow-up (317-426 omega vs 492-613 omega). Five of nine patients with the 438-10 lead had Z values < 300 omega during follow-up (minimum 234 omega). There was no significant difference between the two leads with respect to PT (0.42 V vs 0.41 V), AP (3.75 mV vs 4.25 mV), SR (0.56 vs 1.06), delta Qmin (0.19-1.23 microC vs 0.18-1.35 microC) and Asen (3.4-4.5 mV vs 2.7-4.7 mV), respectively. Two patients developed pericardial effusions after implantation of a ThinLine EZ lead. One of them, who had a transient drop of blood pressure during implant, subsequently developed acute exsudative pericarditis. Therefore, both leads had acceptable sensing and pacing thresholds, but the 438-10 lead developed unusually low long-term lead impedance values. The high incidence of perforations in our small group of 438-10 patients has not been observed, thus far, in other studies.

Aged↗
PubMed1997

Childhood Lead Poisoning in Russia: A Site-specific Pediatric Blood Lead Evaluation.

Lead poisoning in children is an international concern. Health effects vary according to a child's blood lead level. Historically, the problem of lead poisoning in Russia had been defined by analysis of hair samples. In Saratov, Russia, during the spring of 1996, the authors conducted the first evaluation of blood lead levels among Russian children. The mean blood lead level of 579 samples analyzed at the Centers for Disease Control and Prevention was 7.7 µg/dL (range 3.0 to 35.7 µg/dL). The sensitivity of hair analysis in identifying blood lead levels above 10 µg/dL was 50%. Most of the environmental samples evaluated (including water, dust, paint, and soil) were within acceptable U.S. remediation standards. Almost one-fourth of the Russian children evaluated during this site-specific investigation had blood lead levels capable of causing adverse health effects in children. Hair analysis is not an adequate method for identifying these children. Additional investigations in other Russian cities are necessary in order to determine the extent of lead poisoning in Russia's children.

Journal Article↗
PubMed1976

A comparison of two bipolar exercise electrocardiographic leads to lead V5.

ST-segment depression and slope were compared in three lead systems (V5, CC5, and CM5) and in two groups of patients using both visual analysis of electrocardiographic paper and computerized techniques. Bipolar lead CC5 was found to be comparable to lead V5 when visual analysis of electrocardiographic recordings was utilized. Bipolar lead CM5 was found not to be comparable to lead V5 and to be less sensitive if classic criteria for slope were used. The technique of computerized analysis mad measurements of slope and amplitude to a reproducible level not possible with the standard technique. Statistically significant differences were found between the exercise electrocardiographic leads utilizing computerized electrocardiographic analysis . We conclude that computerized techniques of electrocardiographic analysis require new criteria for defining an abnormal repolarization response. The criteria must be specific for different electrocardiographic leads if the repolarization changes in these leads are to have comparable diagnostic significance.

Adult↗
PubMed2002

[Comparison of pseudo Q wave occurrence and distribution on the body surface in New Zealand rabbit recorded by Wilson lead and head-chest lead].

OBJECTIVE: To compare the occurrence and distribution of pseudo Q wave on the body surface of rabbits recorded by Wilson lead with those detected by head-chest (HC) lead. METHODS: ECGs were recorded at each of the 70 points on the thoracodorsal regions of the body surface in 30 normal New-Zealand rabbits. The diagnostic value of the 2 lead systems was assessed on the basis of the detection of occurrence and distribution of pseudo Q wave. RESULTS: Pseudo Q wave was recorded at many points extensively in the thoracodorsal regions by Wilson lead, and only a few testing points on the upper dorsal surface showed pseudo Q wave activity while by HC lead. At the same testing point, the instances of pseudo Q wave detection by the two lead systems respectively were shown to be significantly different by X(2) test (P<0.05). CONCLUSION: HC lead is superior to Wilson lead in terms of its low occurrence rate and limited distribution regions of pseudo Q wave recorded on the body surface of normal rabbits.

Animals↗
PubMed1981

Detection of beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha(2 leads to 3)-sialyltransferase activity in fetal calf liver and other tissues.

Using a micromethodology based on methylation, the specificity of sialic acid transfer to asialo-alpha 1-acid [3H]-glycoprotein in various tissues was studied. CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha(2 leads to 3)-sialytransferase activity (an activity which has not been demonstrated before) was detected in fetal calf liver, embryonic chicken brain, human placenta, and several other tissues. With the exception of the placenta all tissues investigated showed a considerable additional activity of CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha (2 leads to 6)-sialytransferase. Rat and porcine liver also contained the latter enzyme, but were essentially devoid of the alpha(2 leads to 3)-sialytransferase. Mixed enzyme experiments indicated that the alpha(2 leads to 3)-sialytransferase activity is due to a separate enzyme, which is clearly distinguishable from the CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 3)N-acetylgalactosaminide alpha(2 leads to 3)-sialytransferase of porcine liver and submaxillary gland.

Animals↗
PubMed1998

Aggressive approach in the treatment of acute lead encephalopathy with an extraordinarily high concentration of lead.

OBJECTIVE: To report a case of a 3-year-old child with an extraordinarily massive lead concentration, 26.4 micromol/L (550 microg/dL), following environmental exposure to lead paint in the home. LITERATURE REVIEW: The relevant literature concerning the treatment of lead encephalopathy was reviewed during the treatment of this child and preparation of the manuscript. To our knowledge, the landmark article written by Julian Chisolm in 1968 is the only recent article that reported similarly high levels of lead concentration. This case, however, is the first in which 3 chelating agents were used for the treatment of lead encephalopathy. We also reviewed the literature on the use of whole bowel irrigation in heavy metal intoxications. CONCLUSIONS: In this case, aggressive gut decontamination with whole bowel irrigation and triple chelation therapy with British anti-Lewisite, EDTA, and oral succimer was well tolerated and seemed effective for rapidly deleading the child. The extent to which her lead concentration increased while being treated with oral succimer alone necessitated further chelation with EDTA. Further evaluation is necessary to determine if triple chelation therapy is an appropriate method for severe lead intoxication, and if the use of whole bowel irrigation should be considered in heavy metal intoxication.

Brain Diseases↗
PubMed1995

Updating about reductions of air and blood lead concentrations in Turin, Italy, following reductions in the lead content of gasoline.

Considering its well-know toxicity and the chronic human exposure to lead, international law-makers enforced some directives or laws calling for the reduction of lead content of gasoline. All of these legislative acts aimed to reduce health risks for the general population. The aim of this study was to consider the effectiveness of these laws on air lead levels and consequently on blood lead levels in a randomly selected urban Italian population. In particular, these markers were analyzed over the course of several years, corresponding to the periods just before and after enforcements of the reductions of lead in petrol. Data presented point out some considerations: (1) enforcement of legislative measures concerning the reduction of lead in petrol has reduced atmospheric levels of lead. This result demonstrates a major environmental success in primary prevention efforts. (2) This success is clear especially considering that the actual Pb-B levels can be extended to the urbanized populations. Pb-B levels were consistently higher for drinkers, for older adults, and for males. The mean of Pb-B level for the present urbanized population is higher than the U.S. overall population (6.4 vs 3 microgram/dl). This difference can be also explained considering the different historical period of enforcement of the restriction laws.

Adult↗
PubMed1981

Lead elimination of ICRF 158 in rats after chronic lead exposure.

Lead elimination by ICRF 158, a lipophilic derivative of ethylene-diaminetetra-acetate (EDTA), was investigated in rats after chronic lead exposure. The animals had received a lead concentration of 550 ppm in their drinking water for 140 days. Subsequent treatment with ICRF 158 for 30 days led to increased mobilization and elimination of incorporated lead, and the lead-induced inhibition of hemosynthesis was removed. ICR 158 produced no renal damage in excess of lead-induced tubular nephrosis. Separate toxicity tests in mice demonstrated that it is less toxic than CaNa2EDTA. ICRF 158 does not form stable complexes with lead ions in vitro. The mechanism of action of this lipophilic EDTA derivative is compared to that of its hydrophilic correspondent, the chelating agent CaNa2EDTA.

Animals↗
PubMed1991

The delta-aminolevulinate dehydratase polymorphism: higher blood lead levels in lead workers and environmentally exposed children with the 1-2 and 2-2 isozymes.

The erythrocyte delta-aminolevulinate dehydratase (ALAD) isozyme phenotypes and the blood lead levels were determined in a population of 202 lead factory workers in Germany and an environmentally exposed population of 1278 children in New York who had elevated free protoporphyrin levels. In both population, individuals with the ALAD 1-2 or 2-2 isozyme phenotype had levels of blood lead statistically higher than those individuals with the ALAD 1-1 isozyme phenotype (lead workers: P greater than 0.004; children: P greater than 0.0001). Homozygotes and heterozygotes for the ALAD2 allele who expressed the 2-2 or 1-2 isozyme phenotype had median blood lead levels that were about 9 to 11 micrograms/dl greater than similarly exposed individuals who were homozygous for the ALAD1 allele. These findings support the hypothesis that the ALAD2 polypeptide binds lead more effectively, and therefore that individuals with the ALAD2 allele may be more susceptible to lead poisoning.

Alleles↗
PubMed1989

Reducing bone lead content by chelation treatment in chronic lead poisoning: an in vivo X-ray fluorescence and bone biopsy study.

A stained-glass artist with longstanding exposure to lead presented with neuropsychiatric symptoms. He was evaluated before and after chelation treatment by the CaNa2 EDTA lead mobilization test, iliac crest bone lead measurement, and in vivo tibial X-ray fluorescence (XRF). The three methods showed a progressive fall in body lead stores during chelation therapy in association with improvement in symptoms and a fall in blood lead and zinc protoporphyrin levels. In vivo tibial XRF is a safe, rapid, and noninvasive technique for detecting excessive body lead burdens. XRF measurement of bone lead content is a practical method for monitoring the efficacy of therapy as well as for establishing the diagnosis.

Biopsy↗
PubMed1997

Maintenance of elevated lead levels in drinking water from occasional use and potential impact on blood leads in children.

The variation in lead concentration was measured by thermal ionisation mass spectrometry isotope dilution in household tap water throughout the day when the plumbing system was not fully flushed. After collection of an initial 125-ml water sample containing 119 micrograms/l and a 2-l sample, 125-ml samples were collected at hourly intervals for 8 h. The concentrations in the hourly samples remained in the range 35-52 micrograms/l compared with 1.7 micrograms/l for fully flushed water. High precision lead isotopic measurements showed that approximately 50% of the lead in these water samples derives from the tap 'housing' compared with the overall household system. A health risk assessment was performed employing the US Environmental Protection Agency Integrated Exposure Uptake Biokinetic Model. Predicted blood lead levels in infants only exceeded the 'levels of concern' of 10 micrograms/dl when 100% of the water consumed contained 100 micrograms Pb/1. It would appear that unless the infant consumed 100% of first flush water at lead concentrations of approximately 100 micrograms/l, the blood lead would not exceed the recommended 'level of concern'. However, if more than 0.51 was consumed in drinks and formulae using first flush water, then the blood lead could easily exceed the recommended level. Likewise, a pregnant mother could be at risk of consuming considerably more than the 0.51/day first flush water of the concentrations measured, or throughout the day, if the system were not fully flushed.

Adult↗
PubMed2005

Reexamination of lead(II) coordination preferences in sulfur-rich sites: implications for a critical mechanism of lead poisoning.

Recent studies suggest that the developmental toxicity associated with childhood lead poisoning may be attributable to interactions of Pb(II) with proteins containing thiol-rich structural zinc-binding sites. Here, we report detailed structural studies of Pb(II) in such sites, providing critical insights into the mechanism by which lead alters the activity of these proteins. X-ray absorption spectroscopy of Pb(II) bound to structural zinc-binding peptides reveals that Pb(II) binds in a three-coordinate Pb(II)-S(3) mode, while Zn(II) is known to bind in a four-coordinate mode in these proteins. This Pb(II)-S(3) coordination in peptides is consistent with a trigonal pyramidal Pb(II)-S(3) model compound previously reported by Bridgewater and Parkin, but it differs from many other reports in the small molecule literature which have suggested Pb(II)-S(4) as a preferred coordination mode for lead. Reexamination of the published structures of these "Pb(II)-S(4)" compounds reveals that, in almost all cases, the coordination number of Pb is actually 5, 6, or 8. The results reported herein combined with this new review of published structures suggest that lead prefers to avoid four-coordination in sulfur-rich sites, binding instead as trigonal pyramidal Pb(II)-S(3) or as Pb(II)-S(5-8). In the case of structural zinc-binding protein sites, the observation that lead binds in a three-coordinate mode, and in a geometry that is fundamentally different from the natural coordination of zinc in these sites, explains why lead disrupts the structure of these peptides and thus provides the first detailed molecular understanding of the developmental toxicity of lead.

Binding Sites↗
PubMedDate not supplied

Lead, zinc, and erythrocyte delta-aminolevulinic acid dehydratase: relationships in lead toxicity.

A lead-intoxicated patient with extremely high blood lead levels and unexpectedly mild symptoms was studied prior to and following treatment with calcium disodium edetate (ethylenediaminetetraacetic acid) and then prior to and following oral administration of zinc sulfate. During chelation therapy, erythrocyte (delta)-aminolevulinic acid dehydratase (ALAD) activity decreased as blood lead levels fell. Urinary excretion of zinc increased and was more than 3.5 times greater than that of lead. The ratio of blood lead to serum zinc was greatest (1.47) when ALAD activity was lowest. Oral administration of zinc sulfate following chelation therapy resulted in a significant increase in mean ALAD activity. In vitro additions of zinc chloride to the patient's erythrocytes resulted in reactivation of ALAD activity. These studies suggest that zinc is an important element in the ALAD system in man. Zinc may play a protective role in lead toxicity, and zinc supplementation may be a useful adjunct to chelation therapy for lead toxicity.

Adult↗
PubMedDate not supplied

Behavior of lead and zinc in plasma, erythrocytes, and urine and ALAD in erythrocytes following intravenous infusion of CaEDTA in lead workers.

To evaluate the effect of calcium disodium ethylenediamine tetraacetate (CaEDTA) on concentrations of lead and zinc in plasma, erythrocytes, whole blood, and urine, we administered CaEDTA by intravenous infusion for 1 hr to seven lead workers with blood lead concentrations of 46-67 micrograms/100 g (mean 54 micrograms/100 g). The plasma lead concentration (PPb) and the mobilization yield of lead in urine by CaEDTA were highest during the period between 1 and 2 hr after the infusion was started. In contrast, the lead concentration in erythrocytes (EPb) and in whole blood (BPb) remained unchanged during the 24 hr following infusion. Plasma zinc concentration (PZn) also fell rapidly following CaEDTA infusion; the decline was followed by a gradual rise in the zinc concentration in erythrocytes (EZn) without alteration in the zinc in whole blood. The mobilization yield of zinc in urine by CaEDTA (MZn) reached its highest level within 1 hr after the start of the infusion. Delta-aminolevulinic acid dehydratase (ALAD) activity in erythrocytes gradually increased for 5 hr following CaEDTA infusion. These observations suggest that (1) PPb concentration is a more sensitive indicator of the body burden of chelatable lead than is either BPb or EPb; (2) MZn is mobilized mostly from plasma during the first several hours following the start of CaEDTA infusion, and the fall in PZn concentration following infusion is compensated first by a rise in EZn concentration and then by an immediate redistribution of zinc in other organs to the blood; and (3) Pb-inhibited ALAD activity is reactivated by the increased EZn during and shortly after CaEDTA infusion.

Body Burden↗
PubMed1999

An evaluation of worker lead exposures and cleaning effectiveness during removal of deteriorated lead-based paint.

We evaluated worker lead exposures and cleaning effectiveness during initial cleanup of 19th-century buildings with highly deteriorated lead-based paint. Eighteen rooms of similar size and condition in two university-owned buildings were selected for a pilot project to compare three methods for removing loose paint, paint chips, and dust. The methods used were: dry scraping followed by dry sweeping (no engineering or work practice controls); wet scraping and high-efficiency particulate air (HEPA) vacuuming; and the latter method with the addition of a portable HEPA-filtered exhaust fan in the room providing about 40 air changes per hour. The final step for all methods was wet-mopping once with tri-sodium phosphate solution. During a single day 18 rooms were cleaned; each of three two-person work crews cleaned six rooms, two with each method. Air and surface samples were collected before, during, and after cleaning. All of the methods were potentially hazardous to workers: 44 percent of the method-based exposures (range: 5.0-360 micrograms/m3) and one of five full-shift exposures exceeded the OSHA PEL (range 9.4-110 micrograms/m3). Lowest worker exposures were during the wet scraping and vacuuming method (mean: 24 micrograms/m3). Providing general ventilation in rooms did not reduce worker exposures and appeared to increase them (mean: 73 micrograms/m3). Overall, the mean floor surface lead levels were reduced 50 percent after cleaning (from 2,600 to 1,300 micrograms/ft2), but the effectiveness of the three methods in reducing floor lead levels did not differ significantly. Overall, the method, mean paint lead concentration, pre-cleaning surface lead concentration, and work crew were significantly associated with the mean worker exposures during cleaning (p = 0.023), but not with the post-cleaning surface lead concentrations (p = 0.13).

Air Pollutants↗
PubMed1988

Bone lead, hypertension, and lead nephropathy.

There is considerable clinical evidence that excessive lead absorption causes renal failure with hypertension and predisposes individuals to hypertension even in the absence of detectable renal failure. Recent analyses of transiliac bone biopsies indicate that unsuspected elevated bone leads may reflect the cause (or contributing cause) of end-stage renal disease in 5% of the European dialysis population. In these patients, bone lead levels were four times higher than in unexposed cadavers (6 micrograms/g wet weight) and approximated levels found in lead workers (30 micrograms/g). At present, the most reliable index of the body lead burden is the CaNa2 EDTA lead mobilization test. In vivo tibial X-ray-induced X-ray fluorescence (XRF) is a more practical noninvasive technique for assessing bone lead, which should find widespread application as a diagnostic tool and for epidemiologic studies.

Bone and Bones↗