A quasi-Monte Carlo Metropolis algorithm

This work presents a version of the Metropolis-Hastings algorithm using quasi-Monte Carlo inputs. We prove that the method yields consistent estimates in some problems with finite state spaces and completely uniformly distributed inputs. In some numerical examples, the proposed method is much more accurate than ordinary Metropolis-Hastings sampling.     

Ventricular rate stabilization for the prevention of pause dependent ventricular tachyarrhythmias: results from a prospective study in 309 ICD recipients

Reviews of stored electrograms from ICDs revealed a 5-30% incidence of short-long-short intervals preceding the onset of recurrent ventricular tachyarrhythmias. Rate stabilization by dedicated antibradycardia pacing algorithms has, therefore, been suggested to prevent onset of pause dependent tachyarrhythmias. However, the clinical efficacy of this approach has not been studied systematically. In a prospective multicenter crossover study, patients were randomized to activation or deactivation of an implemented ventricular rate stabilization algorithm (VRS) after first implant of a dual chamber ICD. After 3 months, all patients were crossed over to the alternate programming. The rate of appropriate spontaneous VA episodes was compared between VRS On and VRS Off. Stored electrograms were reviewed for evaluation of the mode of onset of tachyarrhythmias. Overall efficacy analysis was based on 309 patients enrolled in the study. Forty percent (124/309) of the patients experienced 4,973 VA episodes. Based on an intention-to-treat analysis, VRS Off and On arrhythmia incidence was 10.2 and 6.6 normalized to 3 months, respectively (risk reduction 35%; P = 0.18) On an on-treatment basis, a reduction from 9.0 episodes to 8.1 episodes (10% risk reduction, P = 0.24) was seen. In an extended Cox model adjusting for confounding variables, the relative risk for recurrent episodes was 0.92 during VRS On compared to Off (95% CI: 0.58-1.48; P = 0.74). During VRS Off, pause dependent onset was documented in only 36 (8%) of 427 visually analyzed episodes. There was no significant reduction in the incidence of recurrent ventricular tachyarrhythmias with VRS On compared to the Off programming in this prospective study.     

Safety and efficacy of the supraclavicular approach to thoracic outlet decompression

BACKGROUND: Thoracic outlet syndrome (TOS) is a clinical diagnosis encountered by both thoracic and vascular surgeons. The goal of surgical therapy involves relieving compression of the neurovascular structures at the superior thoracic aperture. The traditional approach to thoracic outlet decompression has been transaxillary; however more centers are moving toward a more tailored approach through a supraclavicular incision. METHODS: The medical records of 67 patients who underwent surgical decompression between 1993 and 2001 for TOS were retrospectively reviewed. Patient demographics and early outcome were assessed through clinic follow-up. RESULTS: Seventy-two thoracic outlet decompressions were performed on 67 patients with the diagnosis of TOS. Five patients underwent bilateral thoracic outlet decompression. All operations in this time period were safely accomplished through a supraclavicular approach. The syndromes associated with thoracic outlet compression were neurogenic (n = 59), venous (n = 10), and arterial (n = 3). Forty-six of 72 (63.9%) operations resulted in complete resolution of symptoms, 17 cases (23.6%) had partial resolution, and 9 patients (12.5%) had no resolution. There were no deaths and morbidity was minimal with 6 complications (8.3%). CONCLUSIONS: The supraclavicular approach is a safe and effective technique in managing all forms of thoracic outlet compression.     

Negative charge distribution and density on the surface of oxygenated normal and sickle red cells

Negative charges on the external surface of red cells were visualized by colloidal iron hydroxide labelling of 50% of the membrane area after osmotic hemolysis and glutaraldehyde fixation. Counts were made over randomly selected areas on electron micrographs at 350,000 x magnification. Statistical analyses showed that at the 95% level of confidence there was no significant difference between oxygenated normal (AA) and sickle (SS) cells in either the distribution or the density of negative charges.     

Pulmonary lymphangitic spread of carcinoma: appearance on CT scans

Chest computed tomography (CT), including high-resolution CT with thin (1.5-mm) sections was used to evaluate proved (pathologically or clinically) lymphangitic spread (LS) of tumor in 12 patients. These appearances were compared with thin-section scans obtained in 11 healthy subjects. Thin-section CT demonstrated findings consistent with thickening of the normal lung interstitium. In all patients, thin sections showed an increase in the number of peripheral lines (1-2 cm in length) that were diffuse in generalized disease and localized in focal disease. Normal peripheral arcades were not increased in number, but the limbs forming the arcades were thickened in all patients. A diffuse increase in linear and curvilinear structures (reticular pattern) was seen toward the center of the lung. Polygonal structures 1-2 cm in diameter were seen in seven patients with LS but not in healthy subjects. Fissures were thickened in nine patients. Selected 1.5-mm-thick CT sections are recommended through abnormal areas (seen at CT or on chest radiographs) or if these are normal at three levels (midapex, hilus, and 3 cm above the diaphragm) when scanning patients with tumors known to cause LS.     

Safety and immunogenicity of a Shigella flexneri 2a Invaplex 50 intranasal vaccine in adult volunteers

Shigellosis is a leading cause of diarrhea worldwide prompting vaccine development. The Shigella flexneri Invaplex 50 is a macromolecular complex containing IpaB, IpaC, and LPS, formulated from an aqueous extract of virulent Shigella delivered via nasal administration. Preclinical vaccine testing demonstrated safety, immunogenicity and efficacy. An open-label dose-escalating phase 1 study evaluated a 3-dose (2-week intervals) regimen via nasal pipette delivery. Thirty-two subjects were enrolled into one of four vaccine dose groups (10, 50, 240, or 480 μg). The vaccine was well tolerated with minor short-lived nasal symptoms without evidence of dose effect. Antibody-secreting cell (ASC) responses were elicited at doses ≥50 μg with the highest IgG ASC, Invaplex 50 (100%) and S. flexneri 2a LPS (71%), as well as, serologic responses (43%) occurring with the 240 μg dose. Fecal IgA responses, Invaplex 50 (38.5%) and LPS (30.8%), were observed at doses ≥240 μg. The Invaplex 50 nasal vaccine was safe with encouraging mucosal immune responses. Follow-on studies will optimize dose, delivery mechanism and assess efficacy in a S. flexneri 2a challenge study.     

Serum Unconjugated Bile Acids and Small Bowel Bacterial Overgrowth in Pediatric Intestinal Failure: A Pilot Study

Background: We determined qualitative and quantitative serum unconjugated bile acid (SUBA) levels among children with history of intestinal failure (IF) and suspected small bowel bacterial overgrowth (SBBO). Methods: This was a single‐center, case‐control pilot study conducted at Cincinnati Children's Hospital Medical Center. Children with history of IF and suspected SBBO were enrolled as subjects. Age‐matched children without IF or suspected SBBO served as controls. All participants underwent small bowel fluid sampling for microbial culture analysis. Additionally, serum fractionated and total bile acids were measured by liquid chromatography‐mass spectrometry at enrollment and following treatment for SBBO. Results: SUBA concentrations were elevated in IF subjects (median 1.16 μM, range 0.43–10.65 μM) compared with controls (median 0.10 μM, range 0.05–0.18 μM, P = 0.001). Among SUBA, chenodeoxycholic acid (CDCA) was significantly elevated in subjects (median 0.8 μM, range 0–7.08 μM) compared with controls (median 0 μM, range 0–0.03 μM, P = 0.012). When controls were excluded from analysis, IF subjects with positive aspirates for SBBO demonstrated higher concentration of CDCA (median 7.36 μM, range 1.1–8.28 μM) compared with IF subjects with negative aspirates (median 0.18 μM, range 0–1.06 μM, P = 0.017). Treatment for SBBO did not alter SUBA concentration. Conclusions: SUBA concentrations are elevated in children with history of IF and presumed SBBO compared with non‐IF controls. CDCA was more prevalent in IF subjects with positive aspirates for SBBO compared with IF subjects with negative aspirates. The determination of SUBA concentration may be a useful surrogate to small bowel fluid aspiration in the diagnosis of SBBO in children with history of IF.     

Kr-81m ventilation imaging: clinical utility in suspected pulmonary embolism

The results of Kr-81m/Tc-99m ventilation-perfusion (VP) lung scintigraphy were correlated with the results of pulmonary angiography for 74 patients suspected of having pulmonary embolism (PE). Among patients having a diagnostic scan, the sensitivity and specificity of scintigraphy were 91% and 94%, respectively. Also, 157 consecutive cases of Kr-81m/Tc-99m VP lung scintigraphy were reviewed, and the frequency of an indeterminate scan was found to be 22%. A similar frequency was found for VP scintigraphy with xenon-133. Of eight patients who had indeterminate scans due to the presence of a single VP mismatch, four were demonstrated to have PE by angiography. Kr-81m is an excellent agent for VP scanning in cases of suspected PE, offering accuracy in diagnosis as well as favorable physical properties.