Improved performance characteristics of the von Willebrand factor ristocetin cofactor activity assay using a novel automated assay protocol

BACKGROUND, OBJECTIVES AND METHODS: An accurate, sensitive and precise assay for reliable determination of the ristocetin cofactor activity of von Willebrand factor (VWF:RCo) in plasma and von Willebrand Factor (VWF)-containing concentrates has been evaluated. The assay is based on a commercially available automated protocol with modifications including a combination of adding additional ristocetin and the use of two calibration curves for the high and low measuring ranges.

RESULTS

 Addition of extra ristocetin resulted in improved measurement of VWF recoveries from various VWF-containing concentrates that were underestimated using the standard automated protocol. The modifications resulted in improved assay performance over an extended measuring range (2.00-0.03 IUmL(-1) ). Accuracy was tested using VWF deficiency plasma spiked with the 1st international standard (IS) for VWF concentrate. Seven dilutions, ranging from 1.80 to 0.05IUmL(-1) , were analyzed and resulted in measured concentrations between 80% and 100% of the assigned potency of the standard. Linearity was determined from the regression plot of the same concentrate dilutions and resulted in a correlation coefficient of 0.998. The repeatability, expressed as coefficient of variation, was 2% in the normal range (0.90IUmL(-1) ) and 8% at the level of 0.05IUmL(-1) . The corresponding reproducibility results were 2% and 15% at the normal and low measuring ranges, respectively.

CONCLUSIONS

 Analysis of patients with von Willebrand disease (VWD) indicates that the modified automated BCS(®) protocol has a superior discrimination power compared with the standard protocol. This is especially true in samples with low VWF, as in patients with type 3 VWD.

Characterisation of a novel high-purity, double virus inactivated von Willebrand Factor and Factor VIII concentrate (Wilate)

This study summarises the biochemical and functional properties of a new generation plasma-derived, double virus inactivated von Willebrand Factor/Factor VIII (VWF/FVIII) concentrate, Wilate, targeted for the treatment of both von Willebrand disease (VWD) and haemophilia A. The manufacturing process comprises two chromatographic steps based on different performance principles, ensuring a high purity of the concentrate (mean specific activity in 15 consecutive production batches: 122 IU FVIII:C/mg total protein) and, thus, minimising the administered protein load to the patient (specification: < or = 15 mg total protein per 900 IU Wilate). The optimised solvent/detergent (S/D) treatment and prolonged terminal dry-heat (PermaHeat) treatment of the lyophilised product at a specified residual moisture (RM) provide two mechanistically independent, effective and robust virus inactivation procedures for enveloped viruses and one step for non-enveloped viruses. These process steps are aggressive enough to inactivate viruses efficiently, but yet gentle enough to maintain the structural integrity and function of the VWF and FVIII molecules, as proven by state-of-the-art assays covering the diverse features of importance. The VWF multimeric pattern is close to the one displayed by normal plasma, with a consistent content of more than 10 multimers, but a relatively lower portion of the very high multimers. The multimeric triplet structure is normal, underlining the gentle and effective manufacturing process, which does not require the addition of protein stabilisers at any step. The balanced activity ratio of VWF to FVIII is close to that of plasma from healthy subjects, rendering Wilate suitable also for the safe and effective treatment of patients with VWD.

[The time-course of action of rapacuronium and mivacurium after early reversal following equally lasting relaxation]

This study was designed to compare the time course of action and the safety profile of Rapacuronium and Mivacurium in day case dental surgery. After Ethics Committee approval 61 healthy adult patients, scheduled for dental day case surgery, were randomised in an assessor-blinded manner to receive either 1.5 mg/kg Rapacuronium with and without 0.05 neostigmine 5 min later (19 patients each) or a total of 0.25 mg/kg Mivacurium (n = 16). Anaesthesia was induced using Propofol 2 - 5.1 mg/kg and Remifentanil 24 - 73 mcg/kg/h and maintained with Desflurane in N2O/O2 (2/1). Endotracheal intubation was performed when maximum blockade was achieved and scored by a blinded intubator. Neuromuscular block was monitored using the train-of-four response to supramaximal stimuli at the ulnar nerve every 15 seconds using acceleromyography (TOF Watch SX). Onset time, clinical duration (reappearance of the third twitch of a TOF-stimulation) and recovery to T4/T1 > 0.9 were recorded. Speed of recovery was evaluated by the time difference between reappearance of the third twitch and T4/T1 > 0.9. The intubating conditions at the time of maximum block revealed no statistically significant differences between the three groups. Changes in blood pressure, heart rate and airway pressure were not significant. Onset time in subjects who received Rapacuronium (99 +/- 29 s) was faster compared to the onset time in those who received Mivacurium (157 +/- 36 s). Also clinical duration was significantly shorter following Rapacuronium without reversal (12 +/- 4 min) as well as with reversal (9 +/- 1 min) compared with Mivacurium (21 +/- 5 min)). Patients treated with Rapacuronium and reversal recovered faster (14 +/- 8 min)) compared to the other two groups (Mivacurium: 20 +/- 6 min, Rapacuronium without reversal: 31 +/- 9 min). The fraction of clinical duration of the total duration was highest following Mivacurium (51 %) when compared with Rapacuronium/Neostigmine (43 %) and Rapacuronium (28 %).

[Motor function during patient-controlled analgesia via a lumbar epidural catheter after major abdominal surgery. Ropivacaine-sufentanil vs. bupivacaine-sufentanil]

INTRODUCTION

The aim of the present study was to investigate postoperative motoric impairment during patient-controlled analgesia after major abdominal surgery with ropivacaine-sufentanil and bupivacaine-sufentanil via a lumbar epidural catheter.

METHODS

After approval of the local ethics committee, 40 patients scheduled for major lower abdominal surgery were randomly allocated to receive bupivacaine 0.25 % or ropivacaine 0.2 %, both with sufentanil 2 microgram/ml in a double blind manner. General anaesthesia (midazolam, etomidate, fentanyl, vecuronium, and desflurane in N2O/O2) and postoperative management of the patients were standardised. Postoperatively, the motoric function and ability for active early mobilisation was examined clinically (application of the Bromage scale, ability to leave the bed and ability to walk). Reduction of muscular force of the legs was measured postoperatively using a scale and compared with preoperative baseline values. To ensure a similar level of analgesia, a 10-cm visual analogue scale was applied at rest and while coughing.

RESULTS

The two groups did not differ with respect to the demographic data and postoperative levels of analgesia. Less reduction of motoric function at rest was observed in the ropivacaine group (p = 0,044). However, this did not lead to an increased ability to get up from bed (p = 0,57) or to walk around (p = 0,17). A high number of patients did not meet the requirements for early ambulation. Almost half of the patients of both groups were unable to leave their beds in the morning of the first postoperative day. On the second postoperative day about 25 - 30 % of the patients could not walk even when support was applied. Furthermore, median reduction (10th/90th percentile) of muscular strength was reduced to 50 % (37 %/76 %) in the ropivacaine group and to 48 % (31 %/61 %) in the bupivacaine group compared with preoperative values.

DISCUSSION

While quality of analgesia was similar, mobility of the legs at rest is better preserved with ropivacaine 0.2 % than with bupivacaine 0.25 %. However, despite the fact that high dose sufentanil was added to both local anaesthetics, there was marked motoric impairment in both groups probably due to the lumbar site of the epidural catheter. This was associated with an unacceptable high incidence of patients unsuitable for early postoperative mobilisation.

3D dosimetry study of 188Re liquid balloon for intravascular brachytherapy using bang polymer gel dosemeters

It has been suggested that the combination of intravascular brachytherapy and coronary stent implantation may result in further reduction of restenosis after percutaneous balloon angioplasty. The use of an angioplasty balloon filled with a 188Re liquid beta source for intravascular brachytherapy provides the advantages of accurate source positioning and uniform dose distribution to the coronary vessel wall. The effect of source edge and stent on the dose distribution of the target tissue may be clinically important. In BANG gels, the absorbed radiation produces free-radical chain polymerisation of acrylic monomers that are initially dissolved in the gel. The number of polymer particles is proportional to the absorbed dose. In this study, 3D dose distributions are presented for 188Re balloons, with and without stents, using a prototype He-Ne laser CT scanner and the proprietary BANG polymer gel dosemeters.

Encapsulation of isotope on novel beta-emitting poly(ethylene terephthalate) surfaces

Recent data indicate that intravascular betaa-irradiation from centrally located sources at the time of balloon angioplasty or stenting reduces proliferation of smooth muscle cells, neointima formation, and restenosis. In an effort to simplify radiation delivery, a novel beta-radiation source was developed based on the adsorption of 32P (phosphoric acid) by pH-sensitive chitosan hydrogel on a poly(ethylene terephthalate) balloon surface. To prevent the 32P-isotope desorption in the patient's blood, the adsorbed phosphoric acid was precipitated as CaHPO4 on the surface by a saturated Ca(OH)2/5% CaCl2 solution. Various polyurethanes were applied to seal the radioactive surface by the dip-coating method. The isotope off-rate results were determined. Optimal results were obtained by serially coating with two polyurethane solutions. This approach holds promise for simplifying and improving the safety, and minimizing the cost of intravascular brachytherapy.

Vertebral artery dissection in Turner's syndrome: diagnosis by magnetic resonance imaging

Aortic artery dissection is a rare but well-recognized complication of Turner's syndrome. Isolated carotid or vertebral artery dissection has not previously been reported. The authors report the clinical and magnetic resonance imaging findings in a 30-year-old woman with Turner's syndrome who developed a high cervical spinal cord infarction with a Brown-Sequard syndrome owing to bilateral vertebral artery dissection. The diagnosis and management of the case is reviewed.

Novel beta-emitting poly(ethylene terephthalate) surface modification

Restenosis after percutaneous interventions in coronary and peripheral arteries leads to repeat procedures and surgery in a significant number of patients. We have previously demonstrated that irradiation of an arterial site using an endovascular source (brachytherapy) is highly effective in preventing the restenotic process. To this end, a novel beta radiation delivery system was developed, based on the adsorption of (32)P (o-phosphoric acid) by pH-sensitive chitosan hydrogel on a poly(ethylene terephthalate) (PET) balloon surface. The PET balloon surface was treated with oxygen plasma and coated with chitosan hydrogel. Covalent bonds, ionic bonds, and hydrogen bonds all contribute to the adhesion between chitosan hydrogel and PET. In the aqueous phosphoric acid (PA) solution, the -NH(2) groups of chitosan were protonated by PA and the adsorption of PA occurred at the same time. The effect of PA concentration and temperature on adsorption efficiency and kinetics were studied. More than 70% PA was adsorbed on the sample surface in 0.2 mM PA solution. The surface of samples was also investigated by attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscopy. PET surface may be modified to carry high activity beta emitters; such materials may be useful in a therapeutic setting

William James and the unconscious: redressing a century-old misunderstanding

Contrary to received wisdom in psychology, William James did not oppose postulating unconscious processes. This mistaken belief stems from a misreading of a passage in his Principles concerned with disproving the metaphysical notion that mental states are composed of elementary mental units. The term unconscious had been co-opted by individuals who supported this position. Unconscious did not mean then what it means now. Analysis of the rest of the Principles, his later works, and his reactions to the works of others reveals that James actually supported what we would now term unconscious processes. He even contributed to their study with his notions of the "fringe," "habit," and "subconscious incubation." Causes and effects of this misunderstanding are discussed.

Stroke recurrence is more frequent in Blacks and Hispanics

This study was designed to measure recurrent stroke rates and identify their determinants in a mixed ethnic population. A cohort of 299 patients (110 black, 57 Hispanic and 132 white) admitted to a large urban hospital with an acute stroke between November 1, 1991, and July 1, 1993, was followed for a mean of 17.8 months. Demographic and historical data and stroke subtype and severity were recorded at the time of the index stroke. The main outcome measure was stroke recurrence. The unadjusted relative risk of stroke recurrence for blacks, relative to white, was 2.0 (95% CI: 0.9-4.4) and for Hispanics, relative to whites, it was 2.6 (95% CI: 1.08-60). Ethnicity appeared to be associated with recurrence risk only among first-ever strokes: the risk for blacks, relative to whites, was 2.4 (95% CI: 1.02-5.5) and for Hispanics it was 2.9 (95% CI: 1.2-7.4). None of the other putative risk factors for stroke recurrence identified at the time of initial hospitalization were associated with risk of recurrence.

Natural history of aortic arch atherosclerotic plaque

To define the natural history of aortic arch plaque, we used B-mode ultrasonography to perform sequential study of the aortic arch. Eighty-nine patients were studied for up to 18 months. There was no change in 67% of total plaques; 77% of simple plaque (<4 mm) and 48% of complex plaque (> or =4 mm) did not progress. Atherosclerosis of the aortic arch can be sequentially studied with B-mode ultrasonography, and most of these lesions remain unchanged after up to 18 months of observation.

Plaque morphology correlates with cerebrovascular symptoms in patients with complex aortic arch plaque

BACKGROUND

Studies of aortic arch plaques with transesophageal echocardiography have demonstrated that complex aortic arch plaques (CAPs) greater than or equal to 4 mm in thickness are associated with ischemic stroke. Recent studies have demonstrated that the morphological features of plaques may aid in the identification of aortic plaques that are more likely to be associated with embolic stroke.

OBJECTIVE

To identify aortic plaques that are more likely to be associated with embolic stroke by means of their morphological features.

METHODS

Transcutaneous B-mode ultrasonography was used to image aortic arch plaques in 500 consecutive patients. The criteria used to identify the morphological features of carotid artery plaques that are more likely to be associated with ischemic stroke (heterogeneous rather than homogeneous) were applied to aortic arch plaques. Statistical comparisons were made using the Fisher exact test.

RESULTS

Ischemic symptoms (eg, stroke, transient ischemic attack, and amaurosis fugax) were present in 38% of 104 patients with CAP and in 34% of 391 patients without CAP. Nineteen (51%) of 37 patients with heterogeneous CAP were symptomatic. Twenty-one (31%) of 67 patients with homogeneous CAP were symptomatic (P = .04).

CONCLUSION

Transcutaneous B-mode ultrasonography of the aortic arch can help to identify heterogeneous plaques that are more likely to be associated with ischemic stroke using morphological criteria derived from studies of carotid artery plaque.

Antiphosphatidyl serine antibodies are independently associated with ischemic stroke

OBJECTIVE

To determine whether elevated titers of antiphosphatidyl serine antibodies (aPS) are associated with an increased risk of ischemic stroke in a general stroke population.

BACKGROUND

aPS are members of the family of antiphospholipid antibodies that has been associated with increased stroke risk. Although aPS have been demonstrated to occur in 18% of a group of young patients with cerebrovascular symptoms, their prevalence in the general stroke population is unknown, and no controlled study to assess the strength of their association with ischemic stroke has been undertaken previously.

METHODS

A case-control study comparing 267 acute ischemic stroke patients and 653 community controls. Sera were obtained immediately after acute stroke in patients. Titers of IgG aPS >16 IgG phospholipid units or IgM aPS >22 IgM phospholipid units were considered positive. Odds ratios (ORs) were obtained by logistic regression, adjusting for age, gender, race/ethnicity, history of hypertension, diabetes mellitus, cardiovascular disease, and cigarette smoking.

RESULTS

The adjusted OR was 5.6 (95% confidence interval [CI] 1.8, 18.0) for IgG aPS and 2.9 (95% CI 1.6, 5.3) for IgM aPS. The adjusted OR for either an elevated IgG or IgM aPS was 3.2 (95% CI 1.8, 5.5).

CONCLUSIONS

This study demonstrates that elevated IgG and IgM antiphosphatidyl serine antibodies titers are associated with increased risk of ischemic stroke. The prevalence of these antibodies is lower, but the associated stroke risk is comparable with that of anticardiolipin antibodies.

Elevated anticardiolipin antibody titer is a stroke risk factor in a multiethnic population independent of isotype or degree of positivity

BACKGROUND AND PURPOSE

Previous studies have produced conflicting results regarding the putative association between anticardiolipin antibodies (aCL) and infarction in the general stroke population. These inconsistencies may be a function of sample size and methodological differences among the studies. The purpose of the present study, the largest case-control study of this issue to date, was to assess aCL status as an independent risk factor for ischemic stroke in a multiethnic, urban population.

METHODS

We obtained aCL titers in 524 hospitalized acute stroke patients and 1020 community controls enrolled in the Minorities Risk Factors and Stroke Study. The results were interpreted as negative (</=22.9 IgG phospholipid [GPL] or 10.9 IgM phospholipid [MPL] units), low positive (22.9 to 30.0 GPL or 10.9 to 15.0 MPL units), or high positive (>30.0 GPL or 15.0 MPL units). Odds ratios (ORs) were adjusted for age, sex, race/ethnicity, history of diabetes, hypertension, atrial fibrillation, coronary artery disease, and current cigarette smoking.

RESULTS

A positive aCL titer was present in 11% (111/1020) of controls and 34% (180/524) of cases. The adjusted OR for any positive aCL titer was 4.0 (95% CI, 3.0 to 5.5). For any positive IgG aCL titer this value was 3.9 (95% CI, 2.8 to 5.5), and for any positive IgM aCL titer it was 3.4 (95% CI, 2.1 to 5.5). There were no significant differences in ORs associated with high- or low-positive IgG or IgM aCL titers.

CONCLUSIONS

In the largest study of its kind to date, aCL antibodies were demonstrated to be independent stroke risk factors across the 3 ethnic groups studied, conferring a 4-fold increased risk of ischemic stroke. IgG and for the first time IgM aCL were each shown to be associated with increased stroke risk. The prevalence of these antibodies and the stroke risk associated appear greater than previously reported.

Radioactive beta-emitting solution-filled balloon treatment prevents porcine coronary restenosis

PURPOSE

Intracoronary gamma or beta radiation from centrally located sources at the time of overstretch balloon injury inhibits neointimal proliferation. In an effort to deliver homogeneous, centered radiation fields in a technically straightforward fashion, we studied the effects of a beta-emitting solution used as a balloon inflation fluid to deliver radiation at the time of coronary injury.

METHODS

Twenty-one coronary arteries in 13 juvenile swine underwent irradiation (control and 11 or 25 Gy media dose). Radiation was delivered using a perfusion balloon inflated with an Re-188 solution. Subsequently, overdilatation percutaneous transluminal coronary angioplasty was performed at the pretreated segment. Histopathologic and histomorphometric analysis was performed at 30 days after injury on the entire irradiated artery.

RESULTS

Balloon overdilation was associated with significant vascular injury and marked neointimal proliferation in control and low-dose (11 Gy)-treated arteries. High-dose radiation (25 Gy) significantly inhibited neointima formation compared with controls (neointimal area: 0.49 +/- 0.29 mm2 vs. 1.51 +/- 0.22 mm2, respectively; p = 0.02) and low-dose radiation (neointimal area 1.75 +/- 0.54 mm2, p > 0.1 compared with controls).

CONCLUSIONS

Liquid Re-188 is an effective beta-emitting vehicle to deliver intracoronary radiation and prevent restenosis in this model. Intracoronary radiation treatment using aqueous radioisotope sources is technically straightforward and provides the optimally achievable radiation dose distribution.

Drug therapy of neurovascular disease

The goal of therapy for acute stroke is immediate treatment to reduce the risk of permanent neurologic disability and death. For ischemic stroke, it is imperative to reestablish brain perfusion while at the same time trying to preserve neuronal function. Early treatment of hemorrhagic stroke, particularly subarachnoid hemorrhage, also may improve clinical outcome. Prevention of stroke still remains the most important treatment strategy. In this review, pharmacologic strategies to both prevent and treat thrombotic, embolic, and hemorrhagic strokes are discussed. Treatment modalities for other cerebrovascular disease entities, migraine syndrome, and vascular dementia also are reviewed.

Patient preferences for heart failure treatment: utilities are valid measures of health-related quality of life in heart failure

BACKGROUND

Current standards hold that cost-effectiveness analyses should incorporate measures of both quantity and quality of life, and that quality of life in this context is best measured by a utility. We sought to measure utility scores for patients with heart failure and to assess their validity as measures of health-related quality of life (HRQL).

METHODS AND RESULTS

We studied 50 patients with heart failure. We measured utilities with the time trade-off technique, exercise capacity with a 6-minute walk test, and HRQL with the Minnesota Living With Heart Failure questionnaire, the Medical Outcomes Study Short Form-36 (SF-36) questionnaire, and a visual analogue score. Validity was assessed by establishing correlation between utilities and these other measures. Mean utility score was 0.77 +/- 0.28. There were significant (P < .05) curvilinear relationships between utility score and visual analogue score, the physical function summary scale of the SF-36, 6-minute walk distance, and the Living With Heart Failure score. Utility scores on retest at 1 week were unchanged in a subset of 12 patients. Utilities did not vary systematically with age, sex, or ethnicity.

CONCLUSION

Utilities are valid measures of HRQL in patients with heart failure, and cost-effectiveness analyses of heart failure treatments incorporating utilities in the outcome measure can be meaningful.

Doppler pulse waveform analysis of carotid and middle cerebral artery flow in a patient with an intra-aortic balloon pump

A 60-year-old man with intractable congestive heart failure (CHF) had an intra-aortic balloon pump placed to augment coronary artery perfusion. During the evaluation prior to heart transplant, carotid and transcranial Doppler ultrasonography (TCD) was performed. The authors report the findings of Doppler waveform analysis and the presence of balloon pump artifact which caused difficulty in distinguishing between internal and external carotid arteries. Higher blood flow velocity during diastole and diastolic runoff characteristically seen while insonating the internal carotid artery enabled that distinction.

Gunshot wounds to the hand: management and economic impact

Low-velocity firearms represent the majority of civilian gunshot wounds to the hand, yet much of the literature is based on high-velocity injuries. The authors reviewed their treatment regimen for civilian gunshot wounds to the hand and offer a treatment algorithm that emphasizes early debridement and fracture stabilization. They also address the economic impact on society. The authors reviewed 121 fractures in 90 patients with gunshot wounds to the hand treated at an urban trauma center during the last 5 years. All patients were managed with irrigation and debridement, elevation, intravenous antibiotics, and early fracture stabilization. Sixty fractures were managed with rigid internal or external fixation: Kirshner wires (26%), miniplates (16%), and external fixation (8%). Fifty-six fractures were managed with closed reduction. Five fractures required amputation. There was one subsequent infection and two late amputations. The cost of hospitalization and operative care was more than $1.7 million. For gunshot wounds to the hand the authors advocate immediate irrigation and debridement, intravenous antibiotics, early fracture stabilization, and a low threshold for internal fixation. This regimen is supported by their low infection and complication rates.

Dose perturbations by high atomic number materials in intravascular brachytherapy

PURPOSE

In intravascular brachytherapy, use of high atomic number materials, such as contrast agents and metallic stents, can introduce significant dose perturbations, especially for low energy photons. The purpose of this study is to investigate dose perturbation at the interfaces of high atomic number materials and tissue.

METHODS

To investigate this issue, the radial dose functions across the interface between different materials and soft tissue were calculated by using Monte Carlo simulations. Various interfaces, including contrast agent to water, stainless steel to water, and bone (simulating a calcified plaque) to water, were investigated for photon energies between 20 keV and 1 MeV.

RESULTS

It was found that the dose to water near the interface is enhanced considerably by photons of energies between 0.020 and 0.200 MeV. For example, the maximum dose enhancement factors for the Hypaque-tissue interface ranged from 2.2 to 18.3 for photons in this energy range. The enhancement factor is almost equal to 1 for photon energy between 0.400 and 1.000 MeV. It appears that the maximum enhancement occurs around 60 keV. For 60-keV photons, the maximum dose enhancement factors are about 18.3, 18.7, 19.1, and 3.1 for Hypaque, Omnipaque, stainless steel, and calcified plaque, respectively. The dose enhancement decreases exponentially with distance from the interface. The affected tissue thickness is dependent on the photon energy. As expected, the higher the photon energy is, the larger is the affected tissue thickness. Depending on the type of interface and the energy of photons, the dose enhancement distance (defined as the thickness receiving more than twice the dose without interface) ranges from 1.3 to 72 microm for photons of energy from 0.020 to 0.100 MeV, respectively.

CONCLUSIONS

The existense of high atomic number materials could introduce significant dose enhancement at the interfaces between these materials and tissue. This dose enhancement can be higher than an order of magnitude for photon energies around 60 keV, and should be considered in evaluation of the efficacy of intravascular brachytherapy.

Endovascular beta irradiation for prevention of restenosis using solution radioisotopes: pharmacologic and dosimetric properties of rhenium-188 compounds

PURPOSE

Irradiation of the arterial wall with beta particles has been shown to be effective in inhibiting neointimal hyperplasia following percutaneous transluminal coronary angioplasty (PTCA). In this study, we describe the use of 188W/188Re generators to obtain 188Re (half-life 16.9 h, maximal beta energy of 2.12 MeV) as a new candidate radioisotope for endovascular irradiation. We have evaluated two [188Re]-compounds as candidates for use as solution-based radiation sources that would allow conventional liquid-filled balloon inflation for delivery of radiation to the vessel wall. While balloon rupture at nominal inflation pressures is a very rare event, (<1 per 10,000 at high pressure), radioisotope release could potentially result in significant dose to radiation-sensitive organs. We have thus evaluated the biodistribution, dosimetry, and kinetics of excretion in rats of two 188Re-labeled compounds that are proposed for intravascular therapy.

MATERIALS AND METHODS

Rhenium-188 was obtained as [188Re]-sodium perrhenate by saline elution of an alumina-based 188W/188Re generator system (>500 mCi). High specific volume solutions of the [188Re]-sodium perrhenate (>50 mCi/ml) were obtained by post-elution concentration of the generator bolus by passage through a tandem silver cation/anion column system. Rhenium-188-labeled benzoylthioacetyltriglycine (MAG3) was prepared by stannous ion reduction of [188Re]-perrhenate in the presence of the benzyl-MAG3 substrate, and was characterized as a single radioactive component. Rhenium-188-perrhenate and [188Re]-MAG3 were administered to separate groups of Fischer rats, which were sacrificed at various times and the tissue distribution of 88Re determined in the major organs. Excretory products were also collected daily from separate groups of rats for each agent over 7 days. The effects of perchlorate and iodide preblocking and postdisplacement of thyroid uptake of [188Re]-perrhenate were also evaluated.

RESULTS

Organ uptake values were modest for both agents [<0.25 % injected dose(ID)/gram of tissue at 6 h] for all organs evaluated except for the thyroid, with the intestines and intestinal contents showing the highest uptake values (0.72-1.97 %ID/gram). Whereas thyroid uptake of 188Re after injection of [188Re]-MAG3 was low (0.16 %ID/gram), uptake after injection of [188Re]-perrhenate was higher and could be blocked by pretreatment with perchlorate (intravenous [IV]) or displaced by perchlorate posttreatment. Also, oral or IV iodide pre- or postadministration could also significantly block or displace thyroid uptake of [188Re]-perrhenate. Both [188Re] agents were excreted primarily via the urinary bladder. The excretion half-life of [188Re]-perrhenate was about 7 h; in contrast, the [188Re]-MAG3 complex showed 50% excretion in less than 2 h. The large intestines received the most significant adsorbed dose, with values of 2.0 cGy/ mCi for [188Re]-perrhenate and 4.6 x 10(-3) cGy/mCi for [188Re]-MAG3.

CONCLUSIONS

Rhenium-188-MAG3 shows more rapid urinary bladder excretion in rats than perrhenate and both agents show low organ uptake. Thyroid uptake of free [188Re]-perrhenate can be blocked or displaced with oral perchlorate administration. For the projected use of [188Re]-MAG3 for balloon inflation required for irradiation of the arterial wall, calculated organ dose values are within acceptable limits in the unlikely event of low pressure balloon rupture. Rhenium-188-MAG3 in solution is thus a new candidate for balloon dilation providing uniform endovascular irradiation following PTCA for restenosis therapy.

Intracoronary radiation for prevention of restenosis: dose perturbations caused by stents

BACKGROUND

Intravascular irradiation with beta-emitters has been proposed for inhibition of restenosis in coronary arteries after balloon angioplasty or stent implantation. Previous studies have shown the effectiveness of gamma-radiation to prevent recurrent restenosis, even in the presence of an implanted stent. The limited range of beta-particles compared with gamma-radiation, however, opens the question of whether absorption and scattering of beta-particles by stent struts will cause significant perturbations in the uniformity and magnitude of the radiation dose, which may in turn compromise treatment.

METHODS AND RESULTS

Nine different stents were deployed with a balloon filled with a beta-emitting radioactive liquid. Dose distributions were measured with Gafchromic film. Stents varied significantly in their absorption of beta-particles. Some stents, constructed of fine meshed wires, produced minimal dose perturbations. Others, with thicker, high-atomic-number struts, induced cold spots in the dose distribution adjacent to the wires of </=35%. Average dose reduction varied from 4% to 14% in the presence of various stents.

CONCLUSIONS

Radiation strategy may have to be tailored to stent design. Stents that minimally perturb the dose distribution may be deployed before irradiation. Those that significantly alter the radiation dose might be better deployed after irradiation. Dose prescriptions may require modification if such perturbations prove clinically significant. Observed dose perturbations, however, decreased rapidly with increasing distance from the stent, which may mitigate the clinical impact of these findings. This, as well as the effects of stents on gamma-dose distributions, requires further investigation.

Intracoronary radiation using radioisotope solution-filled balloons

A substantial body of experimental evidence suggests that local application of radiation at sites of angioplasty or stent implantation prevents neointima formation. Recent initial clinical studies report a significant reduction in clinical restenosis rates when gamma emitting radiation sources are used to treat the site of coronary intervention. Because of the energy of therapeutic gamma sources and the shielding requirements, it would be far preferable to deliver ionizing radiation using a local beta emitter. This report discusses a number of the physical, biological, and technical parameters involved in radiation from a balloon angioplasty catheter filled with a beta emitting radioisotope solution.

A new noninvasive technique for imaging atherosclerotic plaque in the aortic arch of stroke patients by transcutaneous real-time B-mode ultrasonography: an initial report

BACKGROUND AND PURPOSE

Aortic arch atherosclerotic plaque is a probable source of atheroembolic stroke. Transesophageal echocardiography (TEE) has been used to image the aorta of patients with stroke to identify atherosclerotic plaque. TEE is moderately invasive and does not always visualize plaques present in the distal ascending aorta and proximal aortic arch.

METHODS

In the current study, transcutaneous B-mode ultrasonography was performed to image the aortic arch through a lateral supraclavicular window, and the results were compared with those of TEE in 20 patients. The aorta was subdivided into the proximal ascending (PAsc), distal ascending (DAsc), proximal aortic arch (PAA), and distal aortic arch (DAA) to be certain the plaques identified by each technique were the same. Plaques were characterized as simple (<4 mm thick) or complex (>4 mm thick).

RESULTS

In the PAsc, 8 simple plaques were identified with TEE but not with B-mode. In the DAsc, 1 complex plaque was identified with both techniques, and B-mode identified 1 additional complex and 1 simple plaque. In the PAA, 6 simple and 5 complex plaques were identified by both techniques, and TEE identified 1 additional complex plaque. In the DAA, TEE identified 2 simple and 2 complex plaques; B-mode identified 3 complex plaques.

CONCLUSIONS

B-mode imaging compared favorably with TEE in identification of plaques in the aortic arch and distal ascending aorta, although it could not identify simple plaques in the proximal ascending. B-mode could visualize plaques not seen by TEE in the distal ascending aorta. B-mode ultrasonography is complementary to TEE in performance of a comprehensive assessment of plaque in the aortic arch and provides a noninvasive method for sequential studies of plaques that can be visualized.

The Minorities Risk Factors and Stroke Study (MRFASS). Design, methods and baseline characteristics

African-Americans and probably Latinos are at increased risk of stroke compared with white, non-Latino Americans. This study seeks to determine if the known risk factors for stroke can account for this increased risk. In this case-control study controls (neighborhood volunteers) were group-matched to acute stroke cases by ethnicity in a ratio of approximately 2:1 for African-Americans and Latinos and 1:1 for whites. Extensive historical, clinical and laboratory data were collected on each subject. For each ethnic group cases were somewhat older and less well-educated than the volunteer controls. Patients in each ethnic group were similar with regard to time from stroke onset to hospital admission, stroke severity, length of stay, discharge disposition and mortality rate. With minor exceptions the distributions of stroke subtypes within each ethnic group appeared similar to those previously reported. Subject recruitment for this case-control study was completed in the manner and time frame planned. Analysis of risk factor information from this sample should provide valuable information regarding the relative risk associated with the major modifiable risk factors for stroke in the minority groups studied.

The effects of subliminal symbiotic stimulation on free-response and self-report mood

Research has shown that subliminal presentation of MOMMY AND I ARE ONE (MIO) can help improve adaptive functioning. Two experiments tried to determine whether changes in mood, especially free-response mood, could help explain these findings. In one experiment, 20 men were randomly assigned to receive either a subliminal MIO or control stimulus. Results showed predicted effects on a free-response and no effects on a self-report mood measure. In the other experiment, 54 male subjects randomly received one of three subliminal stimuli. They evidenced the same pattern of mood results. Sentential semantics were shown to be relevant to the obtained results. Ascending threshold and 150 forced-choice discrimination trials demonstrated that subjects could not report stimulus content. It was concluded that MIO effects were attributable to unconscious processing of the entire message and that free-response mood may partly mediate these effects. Suggestions for future research were offered.

Transesophageal echocardiography-guided transvenous biopsy of a cardiac sarcoma

Transvenous endomyocardial biopsy is a well established procedure to diagnose rejection after heart transplantation as well as to assess for other cardiomyopathic processes. However, it is rarely used to obtain samples of unidentified cardiac masses. We report a case of a primary cardiac sarcoma in which the histologic diagnosis was provided by transesophageal echocardiography-guided transvenous biopsy. This procedure is accurate and can avoid the potential risk of a diagnostic thoracotomy.

Intracoronary irradiation for the prevention of restenosis

Restenosis after coronary angioplasty is a major limitation of an otherwise highly effective and safe procedure for the treatment of atherosclerotic coronary artery disease. Although the advent of coronary stenting has reduced restenosis rates for selected patients, an overall restenosis rate of 20% to 25% remains. Despite numerous trials, no effective pharmacologic therapy has been found. Intracoronary irradiation is a new technique proposed to prevent restenosis after angioplasty. In animal models of restenosis after balloon injury, there is marked reduction of neointimal proliferation when the injured vessel is irradiated, using a variety of radiation sources and delivery systems. Early human trials have underscored the importance of careful source calibration and dosimetry. A small, randomized, double-blind, placebo-controlled study of intracoronary irradiation to prevent recurrent restenosis recently reported striking reductions in angiographic restenosis as well as clinical event rates. A number of important issues remain unresolved, such as defining which component of the arterial wall serves as the target tissue for radiation, the minimal effective dose, the maximum tolerable dose, and user-friendly radiation delivery systems. Further studies are needed to define the safety, efficacy and the ultimate usefulness of intracoronary irradiation as an adjunct to current procedures in interventional cardiology.

Irradiation and stenting

Intravascular irradiation by both gamma and beta sources has been shown to prevent neointimal proliferation after balloon injury in the overstretch pig coronary model. A number of clinical studies are underway that involve brachytherapy from gamma sources in vessels that have been stented. The purpose of this review is to analyse the physical nature of the interaction of various forms of radiation with stent materials and to summarize the available experimental information for relevant clinical correlates of these effects. The ultimate use of vascular radiation in the presence of metallic stents will require knowledge of the possible dose alterations, and where possible, techniques to compensate for these effects.

Modulation of ischemic excitatory neurotransmitter and gamma-aminobutyric acid release during global temporary cerebral ischemia by selective neuronal nitric oxide synthase inhibition

Nitric oxide release during cerebral ischemia is the result of both neuronal and endothelial subclasses of nitric oxide synthase (NOS). In this study, we examined the role of specific neuronal NOS inhibition (nNOSI) on excitatory neurotransmitter and gamma-aminobutyric acid (GABA) release during global cerebral ischemia. Microdialysis probes were placed into the striatum of 24 rats. After probe stabilization, rats were randomized to receive 7-nitroindazole (7-NI), a selective nNOSI, in doses of 0, 5, 10, or 20 mg/kg. Temporary global forebrain ischemia was induced for 15 min, followed by 60 min of reperfusion. nNOSI administration did not produce detectable changes in neurotransmitter recovery prior to ischemia. There were significant increases in aspartate (ASP), glutamate (GLU), glycine (GLY), and GABA recovery during ischemia in the absence of nNOSI. 7-NI resulted in an attenuation in GLU, GLY, and GABA recovery during ischemia and reperfusion. No differences in ASP recovery were detected with nNOSI. Differences between the present study and other studies that examine the role of nonspecific constitutive NOSI during cerebral ischemia demonstrate the contribution of neuronal NOS on the modulation of ischemic excitatory neurotransmitter and GABA release.

Modulation of ischemic excitatory neurotransmitter and gamma-aminobutyric acid release during global temporary cerebral ischemia by local nitric oxide synthase inhibition

Systemic nitric oxide synthase inhibition (NOSI) decreases cerebral blood flow, which may worsen ischemic insults. To examine the local effects of NOSI without this confounding effect, we examined the role of a locally administered NOSI, NG-nitro-L-arginine-methyl-ester (L-NAME), on neurotransmitter recovery during cerebral ischemia. Rats were assigned to one of three groups: locally administered L-NAME via a striatal microdialysis probe (n = 11), systemic L-NAME (n = 5), or control (n = 11). Temporary global forebrain ischemia was induced for 15 min, followed by 60 min of reperfusion. L-NAME resulted in decreases of basal aspartate (ASP; 74% of basal) and glutamate (GLU; 60% of basal) recovery. While systemic L-NAME caused significant increases in ischemic ASP and GLU recovery (by 224% and 110%, respectively, compared with ischemic controls), local NOSI administration resulted in a significant attenuation of peak ASP, GLU, glycine, and gamma-aminobutyric acid recovery (43%, 38%, 53%, and 72%, respectively, compared with ischemic controls). We conclude that local NOSI attenuated ischemic neurotransmitter recovery during ischemia/reperfusion. Our results emphasize the importance of the systemic effects of NOSI and suggest both deleterious and beneficial effects of NOSI during ischemia/reperfusion.

Basic fibroblast growth factor as a biochemical marker of exercise-induced ischemia

BACKGROUND

Basic fibroblast growth factor (bFGF) is a mitogenic polypeptide that demonstrates enhanced expression and promotes angiogenesis in animal models of myocardial ischemia and infarction. Elevated levels of bFGF are present in the urine of humans with metastatic tumors, but its expression in human myocardial ischemia is unknown. Thus, we sought to determine whether urine levels of bFGF are altered by exercise-induced ischemia in humans.

METHODS AND RESULTS

Eighty-six patients underwent exercise thallium studies for evaluation of anginal symptoms. Urine levels of bFGF (corrected for urine creatinine) were determined by ELISA immediately before and between 2 and 4 hours after exercise. The change in urine bFGF level was compared between 43 patients with and 43 patients without exercise-induced ischemia. Patients with ischemia had an increase in urine bFGF compared with nonischemic patients (1052 +/- 245 versus -278 +/- 130 pg/g creatinine, P < .0001). Exercise, demographic, and clinical variables were assessed and analyzed for possible effect on bFGF response to exercise. By univariate analysis, a history of hypertension was negatively associated with a change in bFGF level (P < .05). No other variables were associated. By multivariate analysis, only bFGF response (P < .001) and age (P < .05) were independently related to exercise-induced ischemia.

CONCLUSIONS

Significantly increased levels of bFGF are detected in the urine within hours of exercise-induced ischemia. Further studies are warranted to determine whether bFGF might serve as a useful circulating marker of myocardial ischemia in humans.

[Drug onset time of atracurium after pancuronium priming in elderly patients]

Synergism occurs between some combinations of non-depolarising muscle relaxants. To test the effect of pancuronium as a priming dose of atracurium, 45 adults were anaesthetised with 25 micrograms/kg alfentanil. 75 micrograms/kg midazolam, and 0.25 mg/kg edomidate, O2/N2O and enflurane, and were randomised to one of three groups. After induction, 15 patients received 0.5 mg/kg atracurium, 15 were primed with 0.075 mg/kg atracurium and another 15 with 0.0125 mg/kg pancuronium and three minutes later 0.45 mg/kg atracurium. Neuromuscular response was monitored by adductor pollicis electromyogram (EMG) by stimulating in a TOF pattern. Times for tI reduction of 75, 50, 25 and 0% and tI recovery to 10% were taken. There were no differences between the two groups that received only atracurium. The pancuronium priming group showed a significantly faster onset of neuromuscular blockade (tI = 0%: control group I: 76.3 +/- 15.4 sec vs. pancuronium group III: 64.3 +/- 11.3 sec) and a prolonged recovery. Pancuronium priming can shorten the onset time of atracurium while atracurium priming alone showed no shortening. This suggests a synergism for pancuronium priming in combination with atracurium.

Intracoronary irradiation: dose response for the prevention of restenosis in swine

PURPOSE

Restenosis after percutaneous transluminal coronary angioplasty represents, in part, a proliferative response of vascular smooth muscle at the site of injury. We have previously shown that high-dose radiation (20 Gy), delivered via an intracoronary 192Ir source, causes focal medial fibrosis and markedly impairs the restenosis process after balloon angioplasty in swine. This study sought to delineate the dose-response characteristics of this effect.

METHODS AND MATERIALS

Forty juvenile swine underwent coronary angiography; a segment of the left coronary artery was chosen as a target for balloon injury. In 30 swine, a 2 cm ribbon of 192Ir was positioned at the target segment and 20, 15, or 10 Gy were delivered to the vessel wall (10 animals/dose). Subsequently, overdilatation balloon angioplasty was performed at the irradiated segment. In 10 control swine, overdilatation balloon angioplasty was performed without previous irradiation. Thirty-eight animals survived until sacrifice at 30 +/- 3 days. Histopathological analysis was performed by a pathologist in a blinded manner. The area of maximal luminal compromise within the target segment was analyzed via computer-assisted planimetry.

RESULTS

Neointimal area was decreased by 71.4% at 20 Gy and by 58.3% at 15 Gy compared with control animals (p < 0.05 for both). A stimulatory effect on smooth muscle cell proliferation was noted at 10 Gy, with a 123% increase in neointimal area compared with controls (p < 0.05). Mean percent area stenosis was also reduced by 63% at 20 Gy and by 74.8% at 15 Gy compared with controls (p < 0.05 for both).

CONCLUSIONS

Intracoronary irradiation prior to overstretch balloon angioplasty markedly reduces neointima formation; this effect is dose dependent, with evidence of a significant stimulatory effect at 10 Gy. The effective therapeutic dose range for the prevention of restenosis in this model begins at approximately 15 Gy delivered to the vessel wall.

Dosimetric considerations for catheter-based beta and gamma emitters in the therapy of neointimal hyperplasia in human coronary arteries

PURPOSE

Recent data indicate that intraluminal irradiation of coronary arteries following balloon angioplasty reduces proliferation of smooth muscle cells, neointima formation, and restenosis. We present calculations for various isotopes and geometries in an attempt to identify suitable source designs for such treatments.

METHODS AND MATERIALS

Analytical calculations of dose distributions and dose rates are presented for 192Ir, 125I, 103Pd, 32P, and 90Sr for use in intracoronary irradiation. The effects of source geometry and positioning accuracy are studied.

RESULTS

Accurate source centering, high dose rate, well-defined treatment volume, and radiation safety are all of concern; 15-20 Gy are required to a length of 2-3 cm of vessel wall (2-4 mm diameter). Dose must be confined to the region of the angioplasty, with reduced doses to normal tissues. Beta emitters have radiation safety advantages, but may not have suitable ranges for treating large diameter vessels. Gamma emitters deliver larger doses to normal tissues and to staff. Low energy x-ray emitters such as 125I and 103Pd reduce these risks but are not available at high enough activities. The feasibility of injecting a radioactive liquid directly into the angioplasty balloon is also explored.

CONCLUSIONS

Accurate source centering is found to be of great importance. If this can be accomplished, then high energy beta emitters such as 90Sr would be ideal sources. Otherwise, gamma emitters such as 192Ir may be optimal. A liquid beta source would have optimal geometry and dose distribution, but available sources, such as 32P are unsafe for use with available balloon catheters.

Dosimetry of a radioactive coronary balloon dilatation catheter for treatment of neointimal hyperplasia

Recent reports suggest that intraluminal irradiation of coronary arteries in conjunction with balloon angioplasty reduces proliferation of smooth muscle cells and neointima formation, thereby inhibiting restenosis. One possible irradiation technique is to inflate the balloon dilitation catheter with a radioactive solution. This has advantages over other proposed irradiation procedures, in that accurate source positioning and uniform dose to the vessel wall are assured. Several high-energy beta-minus emitters may be suitable for this application. We present experimental measurements and analytical calculations of the dose distribution around a 3-mm-diam by 20-mm-long balloon filled with 90Y-chloride solution. The dose rate at the surface of the balloon is approximately 0.14 cGy/s per mCi/ml (3.78 x 10(-11) Gy/s per Bq/ml), with the dose decreasing to 53% at 0.5 mm, and < 5% at 3.5-mm radial distance. 90Y and other possible isotopes are currently available at specific concentrations > or = 50 mCi/ml (1.85 x 10(9) Bq/ml), which enables the delivery of 20 Gy in less than 5 min. The dosimetric and radiation safety advantages of this system warrant further feasibility studies. Issues of concern include incorporating the beta-emitter into a suitable chemical form, and assessing organ and whole body doses in the (< 1 in 10(3)) event of balloon failure.

Monitoring of soluble HLA alloantigens and anti-HLA antibodies identifies heart allograft recipients at risk of transplant-associated coronary artery disease

The development of accelerated transplant-related coronary artery disease (T-CAD) is the major obstacle to long-term survival of cardiac allografts. We have investigated the role of various demographic and immunologic parameters as prognostic indicators of T-CAD in a population of 274 heart allograft recipients. Our data demonstrate that patients who experience more than 1 episode of acute rejection per year and/or develop antidonor HLA antibodies are at increased risk of developing T-CAD. Using HLA-A2 as a marker for the release of soluble HLA antigens from the donor, we established that recipients displaying circulating donor alloantigens for more than 26 weeks following transplantation are at increased risk of developing T-CAD (P=0.008). This association suggests that the release of alloantigens from the allograft is indicative of chronic injury and/or that it stimulates chronic rejection via the indirect allorecognition pathway. Our findings indicate that patients at risk of developing T-CAD can be identified by monitoring the release of donor alloantigens and production of antidonor HLA antibodies following transplantation.

Ultrasonography for diagnosis and management of carotid artery atherosclerosis. A position paper of the American Society of Neuroimaging

The importance of identifying patients with carotid artery stenosis has attained greater significance in light of recent treatment trials of the efficacy of medical and surgical treatment of both symptomatic and asymptomatic carotid stenosis. Doppler and B-mode ultrasonography can accurately diagnose and quantify stenosis at the cervical carotid artery bifurcation. The development of duplex color-flow instruments has enhanced the sensitivity and specificity of this examination. Ultrasonography should be employed as an initial examination to identify patients with carotid artery stenosis and determine whether further evaluation or treatment is necessary.

Nitric oxide modulates dopamine release during global temporary cerebral ischemia

Dopamine (DA) is released in large quantities from the striatum during cerebral ischemia. Along with excitatory neurotransmitters, DA plays a role in cellular neuronal ischemic injury. In this study we examined the role of nitric oxide (NO) in the ischemia-induced release of DA. A microdialysis probe was stereotactically placed into the corpus striatum of 16 Sprague-Dawley rats for DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) level determinations. After probe stabilization, the animals received either NG-nitro-L-arginine-methyl ester (L-NAME), a NO synthase inhibitor, or vehicle through the microdialysis probe. Temporary global forebrain ischemia was induced using bilateral carotid artery ligature tightening and controlled hemorrhagic hypotension for 15 min. L-NAME administration caused a reduction in ischemic estimated extraneuronal DA concentration by 60% (P < 0.005) compared with control. There was an increase in both DOPAC and HVA concentrations during the recovery period compared to baseline values in the control group (P < 0.05). L-NAME also caused a reduction in HVA concentration compared to vehicle administration during the latter part of recovery (P < 0.05). These data support the concept that ischemic dopamine release may be mediated by NO. This NO-modulated DA release may contribute to the previously reported deleterious neurotoxic effects of NO during ischemia.

Intracoronary irradiation markedly reduces neointimal proliferation after balloon angioplasty in swine: persistent benefit at 6-month follow-up

OBJECTIVES

This study examined the long-term efficacy of intracoronary irradiation for limiting neointimal proliferation after overstretch balloon angioplasty in a porcine model of restenosis. In addition, this study sought to identify any adverse late sequelae of this novel therapy for restenosis.

BACKGROUND

Restenosis after coronary angioplasty represents in part a proliferative response of vascular smooth muscle at the site of injury. We have shown previously that high dose intracoronary radiation induces focal medial fibrosis and markedly reduces neointimal proliferation early after balloon angioplasty in swine.

METHODS

Twenty-two juvenile swine underwent intervention at a target segment of the left coronary artery. In 11 swine, a 2-cm ribbon of iridium-192 was positioned at the target segment and 2,000 cGy was delivered to the vessel wall. Subsequently, overdilation balloon angioplasty was performed at the irradiated segment. In 11 control swine, overdilation balloon angioplasty was performed without previous irradiation. Twenty animals survived and underwent histopathologic analysis at 180 +/- 8 days.

RESULTS

Mean (+/- SD) neointimal area was 1.59 +/- 0.78 and 0.46 +/- 0.35 mm2 (p < 0.001) in control and irradiated animals, respectively. Mean percent area stenosis was 37.9 +/- 12.4% and 14.2 +/- 9.0% (p < 0.001) in the control and irradiated animals, respectively. Thus, by 6-month follow-up, intracoronary irradiation before balloon angioplasty had reduced the bulk of the neointimal lesion by 71.1% and reduced percent area stenosis by 62.5% compared with that in control animals. There was no evidence of radiation vasculopathy or myocardial damage at 6 months.

CONCLUSIONS

Intracoronary irradiation (2,000 cGy) produces persistent impairment of neointimal proliferation 6 months after balloon injury, with no evidence of late radiation sequelae.

Propofol prevents or elevates the threshold for lidocaine-induced seizures in rats

Hypothesizing that propofol's pro and anticonvulsant effects might be dose dependent, we determined the effect of 25, 50, and 100% of a previously determined anesthetic dose of propofol for rats on the amount of lidocaine required to induce seizures. Lidocaine was infused at 2.5 mg kg-1 min-1 into animals that were receiving either (a) 70% N2O balance O2 (n = 10), control group, (b) 2 mg kg-1 bolus followed by 12 mg kg-1 h-1 propofol infusion with 70% N2O (n = 10), group 2, (c) 4 mg kg-1 followed by 24 mg kg-1 h-1 propofol with 70% N2O (n = 20), group 3, (d) 8 mg kg-1 followed by 48 mg kg-1 h-1 propofol with 70% N2O (n = 10), group 4, or (e) 8 mg kg-1 followed by 48 mg kg-1 h-1 propofol without N2O (n = 10), group 5. Temperature PaCO2, and pH were maintained within normal limits until disturbed by seizure activity or lidocaine toxicity. The plasma concentration of lidocaine required to induce electroencephalographically (EEG) detected seizures was 8.7 +/- 0.7 micrograms ml-1 in control animals, 16 +/- 1.7 micrograms ml-1 in group 2, and 32 +/- 4 micrograms ml-1 in 13 animals from group 3 that experienced a seizure (p < 0.01). Seizures did not occur in seven of 20 group 3 rats.(ABSTRACT TRUNCATED AT 250 WORDS)