HIV risk and prevention among clients of a delivery-based harm reduction service during an HIV outbreak among people who use drugs in northern rural Minnesota, USA

BACKGROUND

Since 2019, multiple HIV outbreaks occurred among people who inject drugs (PWID) in Minnesota. Syringe service programs (SSPs) are evidence-based programs that reduce the spread of HIV. We conducted an assessment of characteristics and HIV risk and prevention among clients of a delivery-based SSP near an HIV outbreak in rural, northern Minnesota.

METHODS

In the fall of 2021, we conducted a cross-sectional survey of clients of a mobile SSP based in Duluth, Minnesota. Survey topics included demographics, drug use, sexual behavior, HIV testing history, and HIV status. We conducted descriptive analyses and used univariate logistic regression to identify correlates of syringe sharing. The analysis was limited to PWID in the last six months.

RESULTS

A total of 125 people were surveyed; 77 (62%) were PWID in the last six months. Among these participants, 52% were female and 50% were homeless. Thirty-two percent reported sharing syringes and 45% reported sharing injecting equipment. Approximately one-half (49%) of participants had been tested for HIV in the past year, and none reported being HIV-positive. Individuals reported low condom usage (88% never used), and 23% of participants reported engaging in some form of transactional sex in the last six months. Incarceration in the last year was associated with sharing syringes (odds ratio = 1.4, 95% confidence interval 1.1-1.8).

CONCLUSION

HIV risk was high among PWID receiving services at this SSP. These data highlight a rural SSP that is engaged with people at risk for HIV and needs additional support to expand harm reduction services.

Barriers and facilitators to implementing a Pharmacist, Physician, and Patient Navigator-Collaborative Care Model (PPP-CCM) to treat hepatitis C among people who inject drugs

BACKGROUND

Direct-acting antivirals (DAAs) offer an unprecedented opportunity to eliminate hepatitis C virus (HCV) infection, yet barriers among people who inject drugs (PWID) remain. Having pharmacists provide care through collaborative drug therapy agreements (CDTAs) offers a promising solution. We developed and piloted a Pharmacist, Physician, and Patient Navigator-Collaborative Care Model (PPP-CCM) which utilized pharmacists to directly deliver HCV care at community organizations serving PWID. We conducted formative evaluation of the PPP-CCM pilot to characterize implementation experiences.

METHODS

The PPP-CCM was implemented from November of 2020 through July of 2022. Formative evaluation team members observed implementation-related meetings and conducted multiple site visits, taking detailed fieldnotes. Fieldnotes were iteratively reviewed to identify barriers and facilitators to implementation and used to inform 7 key informant interviews conducted with programmatic staff at the end of the pilot. All data were analyzed using a Rapid Assessment Process (RAP) guided by the Consolidated Framework for Implementation Research (CFIR). The formative evaluation team shared results with program stakeholders (pharmacists, physicians, and other site staff) to verify and expand on learnings.

RESULTS

Evaluation of PPP-CCM revealed 5 themes, encompassing all CFIR domains: 1) PPP-CCM was feasible but challenging to deliver efficiently; 2) the pharmacist role and characteristics (e.g., being flexible, available, and patient-centered) were key to PPP-CCM successes; 3) the PPP-CCM team met challenges engaging patients over time, but some team-based strategies helped; 4) community site characteristics (e.g., existing trusting relationships with PWID and physical space that enabled program visibility) were important contributors; and 5) financial barriers may limit PPP-CCM scale-up and sustainability.

CONCLUSION

PPP-CCM is a novel and promising approach to HCV care delivery for PWID who may previously lack engagement in traditional care models, but careful attention needs to be paid to financial barriers to ensure scalability and sustainability.

Supraglottic airway device to improve ventilation success and reduce pulmonary aspiration during cardio-pulmonary resuscitation by basic life support rescuers: a randomised cross-over human cadaver study

Objectives: Early airway management during cardiopulmonary resuscitation (CPR) prevents aspiration of gastric contents. Endotracheal intubation is the gold standard to protect airways, but supraglottic airway devices (SGA) may provide some protection with less training. Bag-mask ventilation (BMV) is the most common method used by rescuers. We hypothesized that SGA use by first rescuers during CPR could increase ventilation success rate and also decrease intragastric pressure and pulmonary aspiration.Methods: We performed a randomized cross-over experimental trial on human cadavers. Protocol A: we assessed the rate of successful ventilation (chest rise), intragastric pressure, and CPR key time metrics. Protocol B: cadaver stomachs were randomized to be filled with 300 mL of either blue or green serum saline solution through a Foley catheter. Each rescuer was randomly assigned to use SGA or BMV during a 5-minute standard CPR period. Then, in a crossover design, the stomach was filled with the second colour solution and another 5-minute CPR period was performed using the other airway method. Pulmonary aspiration, defined as the presence of coloured solution below the vocal cords, was assessed by a blinded operator using bronchoscopy. A generalized linear mixed model was used for statistical analysis.Results: Protocol A: Forty-eight rescuers performed CPR on 11 cadavers. Median ventilation success was higher with SGA than BMV: 75.0% (IQR: 59.8-87.3) vs. 34.7% (IQR: 25.0-50.0), (p = 0.003). Gastric pressure and differential (maximum minus minimum) gastric pressure were lower in the SGA group: 2.21 mmHg (IQR: 1.66; 2.68) vs. 3.02 mmHg (IQR: 2.02; 4.22) (p = 0.02) and 5.70 mmHg (IQR: 4.10; 7.60) vs. 8.05 mmHg (IQR: 5.40; 11.60) (p = 0.05). CPR key times were not different between groups. Protocol B: Ten cadavers were included with 20 CPR periods. Aspiration occurred in 2 (20%) SGA procedures and 5 (50%) BMV procedures (p = 0.44).Conclusion: Use of SGA by rescuers improved the ventilation success rate, decreased intragastric pressure, and did not affect key CPR metrics. SGA use by basic life support rescuers appears feasible and efficient.

"We'll be able to take care of ourselves" - A qualitative study of client attitudes toward implementing buprenorphine treatment at syringe services programs

BACKGROUND

Syringe services programs (SSPs) complement substance use disorder treatment in providing services that improve the health of people who use drugs (PWUD). Buprenorphine treatment is an effective underutilized opioid use disorder treatment. Regulations allow buprenorphine prescribing from office-based settings, potentially including SSPs although few studies have examined this approach. Our objective was to assess the attitudes among PWUD toward the potential introduction of buprenorphine treatment in an SSP. Methods: In this qualitative study, we recruited 34 participants who were enrolled at a New York City-based SSP to participate in one of seven focus group sessions. The focus group facilitators prompted participants to share their thoughts in five domains: attitudes toward (1) medical clinics; (2) harm reduction in general; (3) SSP-based buprenorphine treatment; (4) potential challenges of SSP-based treatment; and (5) logistical considerations of an SSP-based buprenorphine treatment program. Four researchers analyzed focus group transcripts using thematic analysis. Results: Of the 34 participants, most were white (68%), over the age of 40 years old (56%), and had previously tried buprenorphine (89%). Common themes were: 1) The SSP is a supportive community for people who use drugs; 2) Participants felt less stigmatized at the SSP than in general medical settings; 3) Offering buprenorphine treatment could change the SSP's culture; and 4) SSP participants receiving buprenorphine may be tempted to divert their medication. Participants offered suggestions for a slow intentional introduction of buprenorphine treatment at the SSP including structured appointments, training medical providers in harm reduction, and program eligibility criteria. Conclusion: Overall, participants expressed enthusiasm for onsite buprenorphine treatment at SSPs. Research on SSP-based buprenorphine treatment should investigate standard buprenorphine treatment outcomes but also any effects on the program itself and medication diversion. Implementation should consider cultural and environmental aspects of the SSP and consult program staff and participants.

Utilization patterns for oral oncology medications in a specialty pharmacy cycle management program

BACKGROUND

The cycle management program (CMP) was implemented in 2008 at a national specialty pharmacy with a focus on providing specialized counseling and monitoring for patients on select oral oncology medications. The program now includes nine medications: bexarotene, dasatinib, erlotinib, everolimus, nilotinib, pazopanib, sorafenib, sunitinib, and vorinostat. Patients receive frequent assessments to encourage adherence, identify adverse events, and track discontinuations through a pharmacist outreach at the initiation of therapy, day 10 and 20 of the first month, then monthly thereafter. The use of oral agents is increasing in cancer patients, shifting away from regimens exclusively involving intravenous chemotherapy. This offers advantages for patients in terms of convenience, but introduces risk as patients become more responsible for the administration and monitoring of the medications.

PURPOSE

To evaluate utilization patterns of the oral oncology medications in the CMP including adverse event occurrence, medication discontinuations, and adherence markers.

METHODS

This study is a retrospective review of patient-reported data from the CMP assessments completed in 2013. Data collected include adverse events and grades, adherence markers, and discontinuation rates. A total of 1163 assessments were reviewed from 557 patients. The assessments included in the analysis were the initial assessment, 10-day assessment, 20-day assessment, and the first monthly follow-up assessment, which encompasses the first two months of therapy.

RESULTS

A total of 1453 adverse events were reported. Adverse events were cited as the reason for 39% of discontinuations and 28% of missed/held doses. A total of 101 discontinuations were reported across the nine CMP medications based on the first two months of data. Missed or held doses were reported in 130 assessments.

CONCLUSIONS

Patient engagement and pharmacist interventions, through programs such as the CMP, are important to help patients manage these complex, high-risk medications.

Near valve flows and potential blood damage during closure of a bileaflet mechanical heart valve

Blood damage and thrombosis are major complications that are commonly seen in patients with implanted mechanical heart valves. For this in vitro study, we isolated the closing phase of a bileaflet mechanical heart valve to study near valve fluid velocities and stresses. By manipulating the valve housing, we gained optical access to a previously inaccessible region of the flow. Laser Doppler velocimetry and particle image velocimetry were used to characterize the flow regime and help to identify the key design characteristics responsible for high shear and rotational flow. Impact of the closing mechanical leaflet with its rigid housing produced the highest fluid stresses observed during the cardiac cycle. Mean velocities as high as 2.4 m/s were observed at the initial valve impact. The velocities measured at the leaflet tip resulted in sustained shear rates in the range of 1500-3500 s(-1), with peak values on the order of 11,000-23,000 s(-1). Using velocity maps, we identified regurgitation zones near the valve tip and through the central orifice of the valve. Entrained flow from the transvalvular jets and flow shed off the leaflet tip during closure combined to generate a dominant vortex posterior to both leaflets after each valve closing cycle. The strength of the peripheral vortex peaked within 2 ms of the initial impact of the leaflet with the housing and rapidly dissipated thereafter, whereas the vortex near the central orifice continued to grow during the rebound phase of the valve. Rebound of the leaflets played a secondary role in sustaining closure-induced vortices.

Two-dimensional FSI simulation of closing dynamics of a tilting disc mechanical heart valve

The fluid dynamics during valve closure resulting in high shear flows and large residence times of particles has been implicated in platelet activation and thrombus formation in mechanical heart valves. Our previous studies with bi-leaflet valves have shown that large shear stresses induced in the gap between the leaflet edge and the valve housing results in relatively high platelet activation levels whereas flow between the leaflets results in shed vortices not conducive to platelet damage. In this study we compare the result of closing dynamics of a tilting disc valve with that of a bi-leaflet valve. The two-dimensional fluid-structure interaction analysis of a tilting disc valve closure mechanics is performed with a fixed grid Cartesian mesh flow solver with local mesh refinement, and a Lagrangian particle dynamic analysis for computation of potential for platelet activation. Throughout the simulation the flow remains in the laminar regime and the flow through the gap width is marked by the development of a shear layer which separates from the leaflet downstream of the valve. Zones of re-circulation are observed in the gap between the leaflet edge and the valve housing on the major orifice region of the tilting disc valve and are seen to be migrating towards the minor orifice region. Jet flow is observed at the minor orifice region and a vortex is formed which sheds in the direction of fluid motion as observed in experiments using PIV measurements. The activation parameter computed for the tilting disc valve, at the time of closure was found to be 2.7 times greater than that of the bi-leaflet mechanical valve and was found to be in the vicinity of the minor orifice region mainly due to the migration of vortical structures from the major to the minor orifice region during the leaflet rebound of the closing phase.

Impact of design parameters on bileaflet mechanical heart valve flow dynamics

BACKGROUND AND AIM OF THE STUDY

One significant problem encountered during surgery to implant mechanical heart valve prostheses is the propensity for thrombus formation near the valve leaflet and housing. This may be caused by the high shear stresses present in the leakage jet flows through small gaps between leaflets and the valve housing during the valve closure phase.

METHODS

A two-dimensional (2D) study was undertaken to demonstrate that design changes in bileaflet mechanical valves result in notable changes in the flow-induced stresses and prediction of platelet activation. A Cartesian grid technique was used for the 2D simulation of blood flow through two models of bileaflet mechanical valves, and their flow patterns, closure characteristics and platelet activation potential were compared. A local mesh refinement algorithm allowed efficient and fast flow computations with mesh adaptation based on the gradients of the flow field in the gap between the leaflet and housing at the instant of valve closure. Leaflet motion was calculated dynamically, based on the fluid forces acting on it. Platelets were modeled and tracked as point particles by a Lagrangian particle tracking method which incorporated the hemodynamic forces on the particles.

RESULTS

A comparison of results showed that the velocity, wall shear stress and simulated platelet activation parameter were lower in the valve model, with a smaller angle of leaflet traverse between the fully open to the fully closed position. The parameters were also affected to a lesser extent by local changes in the leaflet and housing geometry.

CONCLUSION

Computational simulations can be used to examine local design changes to help minimize the fluid-induced stresses that may play a key role in thrombus initiation with the implanted mechanical valves.

Evolvable work-centred support systems for command and control: creating systems users can adapt to meet changing demands

Military command and control (C2) organizations are complex socio-technical systems which must constantly adapt to meet changing operational requirements. We describe our experiences in developing a work-centred support system (WCSS) to aid weather forecasting and monitoring in a military airlift C2 organization as an illustrative case. As part of the development process we conducted field observations both before and after introduction of the WCSS in their operations centre. A striking finding was the constant changes that operations personnel faced (changes in goals and priorities, changes in scale of operations, changes in team roles and structure, and changes in information sources and systems). We describe the changes in workplace demands that we observed and the modifications we needed to make to the WCSS in response. For today's fielded systems, it is seldom possible to make changes that are responsive to users' changing requirements in a timely manner. We argue for the need to incorporate facilities that enable users to adapt their systems to the changing requirements of work and point to some promising directions towards evolvable work-centred support systems.

LRP5 gene polymorphisms and idiopathic osteoporosis in men

Mutations in the low-density lipoprotein receptor-related protein 5 gene (LRP5) have demonstrated the role of LRP5 in bone mass acquisition. LRP5 variants were recently reported to contribute to the population-based variance in vertebral bone mass and size in males. To investigate whether LRP5 variants are implicated in idiopathic male osteoporosis, we studied 78 men with low BMD (<2.5 T score or < -2 Z score) aged less than 70 years (mean +/- SD: 50 +/- 16 years) in whom secondary causes of osteoporosis had been excluded and 86 controls (51 +/- 10 years). Genotypes and haplotypes were based on LRP5 missense substitutions in exons 9 (c.2047G > A, p.V667M) and 18 (c.4037C > T, p.A1330V), and their association with osteoporosis evaluated after adjustment for multiple clinical and environmental variables using logistic regression. The presence of osteoporosis was significantly associated with LRP5 haplotypes (P = 0.0036) independent of age (P = 0.006), weight (P = 0.004), calcium intake (P = 0.002), alcohol (P = 0.005) and tobacco (P = 0.004) consumption. Accordingly, the odds ratio for osteoporosis was 3.78 (95% CI 1.27-11.26, P < 0.001) in male carriers of haplotype 3 (c.2047A-4037T, n = 20 cases and 12 controls) versus homozygous carriers of haplotype 1 (c.2047G-4037C, n = 42 cases and 61 controls). In conclusion, these data indicate beyond a significant role for environmental factors, an association between LRP5 variants and idiopathic osteoporosis in males, pointing to a role of LRP5 in this disease.

Detection of aneuploidies by paralogous sequence quantification

BACKGROUND

Chromosomal aneuploidies are a common cause of congenital disorders associated with cognitive impairment and multiple dysmorphic features. Pre-natal diagnosis of aneuploidies is most commonly performed by the karyotyping of fetal cells obtained by amniocentesis or chorionic villus sampling, but this method is labour intensive and requires about 14 days to complete.

METHODS

We have developed a PCR based method for the detection of targeted chromosome number abnormalities termed paralogous sequence quantification (PSQ), based on the use of paralogous genes. Paralogous sequences have a high degree of sequence identity, but accumulate nucleotide substitutions in a locus specific manner. These sequence differences, which we term paralogous sequence mismatches (PSMs), can be quantified using pyrosequencing technology, to estimate the relative dosage between different chromosomes. We designed 10 assays for the detection of trisomies of chromosomes 13, 18, and 21 and sex chromosome aneuploidies.

RESULTS

We evaluated the performance of this method on 175 DNAs, highly enriched for abnormal samples. A correct and unambiguous diagnosis was given for 119 out of 120 aneuploid samples as well as for all the controls. One sample which gave an intermediate value for the chromosome 13 assays could not be diagnosed.

CONCLUSIONS

Our data suggests that PSQ is a robust, easy to interpret, and easy to set up method for the diagnosis of common aneuploidies, and can be performed in less than 48 h, representing a competitive alternative for widespread use in diagnostic laboratories.

Two high throughput technologies to detect segmental aneuploidies identify new Williams-Beuren syndrome patients with atypical deletions

OBJECTIVE

To develop and compare two new technologies for diagnosing a contiguous gene syndrome, the Williams-Beuren syndrome (WBS).

METHODS

The first proposed method, named paralogous sequence quantification (PSQ), is based on the use of paralogous sequences located on different chromosomes and quantification of specific mismatches present at these loci using pyrosequencing technology. The second exploits quantitative real time polymerase chain reaction (QPCR) to assess the relative quantity of an analysed locus.

RESULTS

A correct and unambiguous diagnosis was obtained for 100% of the analysed samples with either technique (n = 165 and n = 155, respectively). These methods allowed the identification of two patients with atypical deletions in a cohort of 182 WBS patients. Both patients presented with mild facial anomalies, mild mental retardation with impaired visuospatial cognition, supravalvar aortic stenosis, and normal growth indices. These observations are consistent with the involvement of GTF2IRD1 or GTF2I in some of the WBS facial features.

CONCLUSIONS

Both PSQ and QPCR are robust, easy to interpret, and simple to set up. They represent a competitive alternative for the diagnosis of segmental aneuploidies in clinical laboratories. They have advantages over fluorescence in situ hybridisation or microsatellites/SNP genotyping for detecting short segmental aneuploidies as the former is costly and labour intensive while the latter depends on the informativeness of the polymorphisms.

From PREDs and open reading frames to cDNA isolation: revisiting the human chromosome 21 transcription map

A supernumerary copy of human chromosome 21 (HC21) causes Down syndrome. To understand the molecular pathogenesis of Down syndrome, it is necessary to identify all HC21 genes. The first annotation of the sequence of 21q confirmed 127 genes, and predicted an additional 98 previously unknown "anonymous" genes (predictions (PREDs) and open reading frames (C21orfs)), which were foreseen by exon prediction programs and/or spliced expressed sequence tags. These putative gene models still need to be confirmed as bona fide transcripts. Here we report the characterization and expression pattern of the putative transcripts C21orf7, C21orf11, C21orf15, C21orf18, C21orf19, C21orf22, C21orf42, C21orf50, C21orf51, C21orf57, and C21orf58, the GC-rich sequence DNA-binding factor candidate GCFC (also known as C21orf66), PRED12, PRED31, PRED34, PRED44, PRED54, and PRED56. Our analysis showed that most of the C21orfs originally defined by matching spliced expressed sequence tags were correctly predicted, whereas many of the PREDs, defined solely by computer prediction, do not correspond to genuine genes. Four of the six PREDs were incorrectly predicted: PRED44 and C21orf11 are portions of the same transcript, PRED31 is a pseudogene, and PRED54 and PRED56 were wrongly predicted. In contrast, PRED12 (now called C21orf68) and PRED34 (C21orf63) are now confirmed transcripts. We identified three new genes, C21orf67, C21orf69, and C21orf70, not previously predicted by any programs. This revision of the HC21 transcriptome has consequences for the entire genome regarding the quality of previous annotations and the total number of transcripts. It also provides new candidates for genes involved in Down syndrome and other genetic disorders that map to HC21.

Laser Doppler velocimetry and flow visualization studies in the regurgitant leakage flow region of three mechanical mitral valves

Streak line flow visualization and laser Doppler velocimetry (LDV) were conducted in the regurgitant leakage flow region of 3 mechanical heart valve types: CarboMedics, Medtronic Hall, and St. Jude Medical. Streak line flow visualization identified regions of high regurgitant flow, and LDV measurements were focused on those locations. Maximum regurgitant flow velocities after valve closure ranged from 0.7 to 2.6 m/s, and maximum Reynolds shear stress after valve closure ranged from 450 to 3,600 dyne/cm2. These data indicate that leakage flows can generate turbulent jets with elevated Reynolds stresses even in bileaflet valves.

Integrating particle image velocimetry and laser Doppler velocimetry measurements of the regurgitant flow field past mechanical heart valves

This study investigates the transient regurgitant flow downstream of a prosthetic heart valve using both laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Until now, LDV has been the more commonly used tool in investigating the flow characteristics associated with mechanical heart valves. The LDV technique allows point-by-point velocity measurements and provides enough information about the temporal variations in the flow. The main drawback of this technique is the time consuming nature of the data acquisition process in order to assess an entire flow field area. The PIV technique, on the other hand, allows measurement of the entire flow field in space in a plane at a given instant. In this study, PIV with spatial resolution of 0 (1 mm) and LDV with a temporal resolution of 0 (1 ms) were used to measure the regurgitant flow proximal to the Björk-Shiley monostrut (BSM) valve in the mitral position. With PIV, the ability to measure 2 velocity components over an entire plane simultaneously provides a very different insight into the flow field compared to a more traditional point-to-point technique like LDV. In this study, a picture of the effects of occluder motion on the fluid flow in the atrial chamber is interpreted using an integration of PIV and LDV measurements. Specifically, fluid velocities in excess of 3.0 m/s were recorded in the pressure-driven jet during valve closure, and a 1.5 m/s sustained regurgitant jet was observed on the minor orifice side. Additionally, the effects of the impact and subsequent rebound of the occluder on the flow also were clearly recorded in spatial and temporal detail by the PIV and LDV measurements, respectively. The PIV results provide a visually intuitive way of interpreting the flow while the LDV data explore the temporal variations and trends in detail. This analysis is an integrated flow description of the effects of valve closure and leakage on the pulsatile regurgitation flow field past a tilting-disc mechanical heart valve (MHV). It further reinforces the hypothesis that the planar flow visualization techniques, when integrated with traditional point-to point techniques, provide significantly more insight into the complex pulsatile flow past MHVs.

A cSNP map and database for human chromosome 21

Single nucleotide polymorphisms (SNPs) are likely to contribute to the study of complex genetic diseases. The genomic sequence of human chromosome 21q was recently completed with 225 annotated genes, thus permitting efficient identification and precise mapping of potential cSNPs by bioinformatics approaches. Here we present a human chromosome 21 (HC21) cSNP database and the first chromosome-specific cSNP map. Potential cSNPs were generated using three approaches: (1) Alignment of the complete HC21 genomic sequence to cognate ESTs and mRNAs. Candidate cSNPs were automatically extracted using a novel program for context-dependent SNP identification that efficiently discriminates between true variation, poor quality sequencing, and paralogous gene alignments. (2) Multiple alignment of all known HC21 genes to all other human database entries. (3) Gene-targeted cSNP discovery. To date we have identified 377 cSNPs averaging ~1 SNP per 1.5 kb of transcribed sequence, covering 65% of known genes in the chromosome. Validation of our bioinformatics approach was demonstrated by a confirmation rate of 78% for the predicted cSNPs, and in total 32% of the cSNPs in our database have been confirmed. The database is publicly available at http://csnp.unige.ch or http://csnp.isb-sib.ch. These SNPs provide a tool to study the contribution of HC21 loci to complex diseases such as bipolar affective disorder and allele-specific contributions to Down syndrome phenotypes.

The case for large-size mutations

There are no laws of physics or chemistry that forbid large mutations. Therefore, the "size" of a random mutation should fit the mathematics of a Poisson point process: The number of mutations (N), versus mutation size (MS), should obey an exponential relationship. Three examples are examined: A simple 15-mutation sequence; actual experimental data involving a sequence of 56,611 random action potentials (rather than mutations); and a synthetic sequence of 65,535 random mutations. In the latter example, with an average MS of 2.22 units, the largest MS is a 25-unit giant that would be associated with major changes.

Observation and quantification of gas bubble formation on a mechanical heart valve

Clinical studies using transcranial Doppler ultrasonography in patients with mechanical heart valves (MHV) have detected gaseous emboli. The relationship of gaseous emboli release and cavitation on MHV has been a subject of debate in the literature. To study the influence of cavitation and gas content on the formation and growth of stable gas bubbles, a mock circulatory loop, which employed a Medtronic-Hall pyrolytic carbon disk valve in the mitral position, was used. A high-speed video camera allowed observation of cavitation and gas bubble release on the inflow valve surfaces as a function of cavitation intensity and carbon dioxide (CO2) concentration, while an ultrasonic monitoring system scanned the aortic outflow tract to quantify gas bubble production by calculating the gray scale levels of the images. In the absence of cavitation, no stable gas bubbles were formed. When gas bubbles were formed, they were first seen a few milliseconds after and in the vicinity of cavitation collapse. The volume of the gas bubbles detected in the aortic track increased with both increased CO2 and increased cavitation intensity. No correlation was observed between O2 concentration and bubble volume. We conclude that cavitation is an essential precursor to stable gas bubble formation, and CO2, the most soluble blood gas, is the major component of stable gas bubbles.

The osmotic swelling characteristics of cardiac valve prostheses

Several types of mechanical cardiac prostheses have been constructed with Delrin occluders, a material that is subject to osmotic swelling. The leaftets are designed to expand to specific tolerances when immersed in blood. The synthetic blood analogs commonly used in vitro contain hydrophilic compounds that can alter the osmotic expansion of the Delrin occluders. A static leak test chamber was employed to illustrate the effects of various test fluids on the sustained regurgitation phase of Delrin valves.

The scaling of the wall pressure fluctuations in polymer-modified turbulent boundary layer flow

Wall pressure fluctuations and integrated skin friction were measured beneath a turbulent boundary layer that was modified by adding drag-reducing polymer to the pure water flow. The measurements were performed on an axisymmetric model, equipped with an isolated cylindrical drag balance section, and placed in the test section of the 0.3048-m-diam water tunnel at ARL Penn State. Data were acquired at a free-stream velocity of 10.7 m/s with pure water and with polymer added to the water at concentrations of 1, 5, 10, and 20 weight parts per million. Nondimensionalization of the wall pressure fluctuation frequency spectra with traditional outer, inner, and mixed flow variables failed to adequately collapse the data. The mean square wall pressure fluctuations were found to scale linearly with the wall shear stress. Polymer addition had little effect on the characteristic time scale of the flow. These properties were used to develop a novel form of the nondimensional wall pressure fluctuation spectrum that provided the best collapse of the measured data.

Fluid dynamics of a pediatric ventricular assist device

The number of pediatric patients requiring some form of mechanical circulatory assistance is growing throughout the world because of new surgical procedures and the success of pediatric cardiac transplantation. However, the salvage rate for those patients requiring circulatory support may be as low as 25%. Despite the fact that Penn State's 70 cc pneumatic ventricular assist device has been used with a success rate of over 90% in more than 250 patients worldwide, efforts to scale down the pump have encountered difficulties. Animal experiments with a 15 cc version were unsuccessful, with explanted pumps showing extensive thrombus deposition within the pumping chamber. The materials used to fabricate the smaller pump as well as the basic operating principles are identical to the successful adult-sized version. It is therefore believed that reducing the size of the pump altered the internal flow field, and that fluid dynamic factors were responsible for the high degree of thrombus observed with the implanted devices. A dimensional analysis was conducted that revealed significant differences in both Reynolds (Re) and Strouhal (St) numbers between the successful and unsuccessful pumps. Two component laser Doppler velocimetry was then used to characterize the internal flow field quantitatively. Comparison with data from the 70 cc pump showed a reduction in wall shear stress and turbulence levels in the 15 cc pump that would yield an environment conducive to clot formation.

Flow visualization in mechanical heart valves: occluder rebound and cavitation potential

High density particle image velocimetry, with spatial resolution of O(1 mm), was used to measure the effect of occluder rebound on the flow field near a Bjork-Shiley Monostrut tilting-disk mitral valve. The ability to measure two velocity components over an entire plane simultaneously provides a very different insight into the flow compared to the more traditional point to point techniques (like Laser Doppler Velocimetry) that were utilized in previous investigations of the regurgitant flow. A picture of the effects of occluder rebound on the fluid flow in the atrial chamber is presented. Specifically, fluid velocities in excess of 1.5 m/s traveling away from the atrial side were detected 3 mm away from the valve seat in the local low pressure region created by the occluder rebound on the major orifice side where cavitation has been observed. This analysis is the first spatially detailed flow description of the effects of occluder rebound on the flow field past a tilting-disk mechanical heart valve and further reinforces the hypothesis that the rebound effect plays a significant role in the formation of cavitation, which has been implicated in the hemolysis and wear associated with tilting-disk valves in vivo.

Hb Iraq-Halabja beta10 (A7) Ala-->Val (GCC-->GTC): a new beta-chain silent variant in a family with multiple Hb disorders

A patient originating from Iraq was referred to our laboratory upon suspicion of a hemoglobinopathy. Routine hematological tests revealed a microcytic and slightly anemic phenotype with an elevated HbA2 suggestive of beta-thalassemia. Samples were obtained for several members of the family which upon examination revealed highly heterogeneous phenotypes that prompted us to investigate the case further. Sequencing of the beta-globin gene and alpha cluster mapping in the propositus and his brother showed a previously undescribed beta-globin variant:Hb Iraq-Halabja, beta10(A7) Ala-->Val (GCC-->GTC), associated with beta0-thalassemia IVS-2 nt1 G-->A and either alpha-thal-2-3.7 kb deletion (brother), or alpha-globin gene triplication anti-3.7 kb type (propositus). Detailed functional studies of the variant gave a normal oxygenation curve, a normal heterotopic action of 2,3 DPG, and normal heat stability and isopropanol precipitation tests. The variant shows a clear difference in migration properties compared to normal beta-chain only when run on PAGE urea Triton. As expected, alpha/beta-globin mRNA ratios were influenced by the concomitant presence of an alpha-globin gene pathology and the beta0 thalassemia and not by the presence of the beta-globin variant which apparently is clinically silent.

Severe inclusion body beta-thalassaemia with haemolysis in a patient double heterozygous for beta(0)-thalassaemia and quadruplicated alpha-globin gene arrangement of the anti-4.2 type

We describe a new case of an association of alpha-globin gene quadruplication of the anti-4.2 type with beta(0)-thalassaemia. The patient, a young woman of mixed Brazilian-Portuguese origin, suffered from chronic haemolytic anaemia with splenomegaly. Bone marrow supravital staining with brilliant cresyl blue and electron microscopy studies showed large inclusion bodies in about 3% of erythroblasts. Upon immunofluorescent staining these inclusions reacted with a monoclonal antibody to alpha- but not to beta-globin. Analysis of alpha-globin cluster by Southern blotting showed the presence of pathologic fragments specific for the anti-4.2 alpha-globin gene quadruplication. Alpha/beta mRNA ratio was higher than in cases combining alpha-globin triplication and beta(0)-thalassaemia or in cases of beta(0)-thalassaemia heterozygous state alone (18, 14.7 and 10.1 respectively). Our data confirmed the hypothesis that the clinically detectable haemolysis in this beta(0)-thalassaemic patient was due to an unusually high amount of precipitated alpha-globin in erythroid precursors. This considerable excess of alpha-globin chains was due partly to the beta-globin deficit caused by the presence of the beta(0)-thalassaemic gene, but also to the presence of 6 active alpha-globin genes resulting from alpha-globin gene quadruplication in one chromosome.

In vitro studies of gas bubble formation by mechanical heart valves

BACKGROUND AND AIM OF THE STUDY

Recent clinical research using transcranial Doppler ultrasonography has shown the presence of emboli in the cranial circulation of some mechanical heart valve patients. Due to the high-intensity signals produced by these emboli, it has been suggested that they are small gas bubbles. Meanwhile, transesophageal echocardiography of mechanical heart valve patients has shown images of bright, mobile particles (also considered to be gas bubbles) near the valve. Motivated by these reports, a series of in vitro studies was performed to investigate the relationship between dissolved gas concentration and the incidence of bubble formation after valve closure.

METHODS

A mock circulatory loop was used to study a Medtronic Hall tilting disc valve in the mitral position of the Penn State Electrical Ventricular Assist Device (EVAD). The valve was videotaped as it operated in saline with various levels of dissolved CO2. A Doppler ultrasound probe served as a bubble detector on the outflow side of the EVAD. Measurements of vaporous cavitation intensity with a high-fidelity pressure transducer were also made. Similar experiments were then performed in porcine blood, using an imaging ultrasound transducer to detect bubbles.

RESULTS

Bubbles were seen moving off the valve in the retrograde direction just after closure. The ultrasound probe detected these bubbles downstream, indicating a bubble lifetime on the order of seconds. It was observed with high-speed video that bubble formation and cavitation are separate events and occur at different times during valve closure. Bubbles were more likely to be observed when CO2 levels were higher. Experiments in blood provided images of bubbles near the valve, predominantly at higher CO2 levels and high valve loading conditions.

CONCLUSIONS

These results show that stable gas bubbles can form during mechanical heart valve operation. The bubbles likely form from the combined effects of gaseous nuclei formed by cavitation, low-pressure regions associated with regurgitant flow, and the presence of CO2, a highly soluble gas.

A comparison of the cavitation potential of prosthetic heart valves based on valve closing dynamics

BACKGROUND AND AIMS OF THE STUDY

This study compares the cavitation potential of prosthetic heart valves based on valve closing dynamics.

METHODS

A laser sweeping technique measured valve closing dynamics (average closing velocity and deceleration) immediately before valve closure. A high-fidelity, piezoelectric pressure transducer was mounted proximal to the mitral valve and measured the high-frequency pressure fluctuations caused by cavitation bubble formation and collapse after valve closure. The band-pass filtered root mean squared (RMS) value of the mitral pressure signal was used as a measure of cavitation intensity. The combination of these two techniques allowed the direct correlation of valve dynamics and cavitation intensity for each valve closure. The effects of three parameters on prosthetic heart valve dynamics and cavitation were examined: valve geometry (Medtronic Hall and Björk-Shiley Monostrut), occluder material (pyrolytic carbon and Delrin), and gap width between the occluder and housing. A dimensional analysis was also performed to investigate the general form of the relationship between valve dynamics and cavitation intensity.

RESULTS

For all of the valves investigated in this study, the RMS pressure increased (signifying an increase in cavitation) as the average closing velocity and deceleration increased. In order to compare the cavitation potential of the valves, the RMS pressure was estimated at specific closing velocities using the linear regression of RMS pressure versus average closing velocity for each valve. The effects of valve geometry, occluder material and gap width were then examined at high valve loading conditions (closing velocity of 4.0 m/s). For both pyrolytic carbon and Delrin, the Medtronic Hall valves had significantly higher RMS pressures than did the Björk-Shiley Monostrut valves. For a given valve geometry, the pyrolytic carbon occluder had a significantly higher RMS pressure than the Delrin occluder. The valve gap width did not have a significant effect on RMS pressure. The dimensional analysis revealed the general relationship among average closing velocity, occluder material properties and cavitation intensity.

CONCLUSIONS

The results presented here contribute to our fundamental understanding of cavitation on mechanical heart valves.

Mean velocity and Reynolds stress measurements in the regurgitant jets of tilting disk heart valves in an artificial heart environment

Laser Doppler velocimetry, with a high temporal resolution (1 ms time windows), was used to measure the flow field in two regions (major and minor orifices) near the aortic and mitral valves (Bjork Shiley monostrut Nos. 25 and 27, respectively) of the Penn State artificial heart. The motion of each valve was also investigated using a 1000 frame/s video camera in order to estimate the valve's closing velocity. Fluid velocities in excess of and opposite to valve closing velocity were detected near the valve, providing evidence of "squeeze flow." Maximum Reynolds shear stresses of approximately 20,000 dyn/cm2 and time-averaged Reynolds shear stresses of approximately 2000 dyn/cm2 were observed during the regurgitant flow phase. These elevated Reynolds shear stresses suggest that regurgitant jets play a role in the hemolysis and thrombosis associated with tilting disk heart valves in an artificial heart environment.

Three-component laser Doppler velocimetry measurements in the regurgitant flow region of a Björk-Shiley monostrut mitral valve

Three-dimensional laser Doppler velocimetry measurements were acquired in a mock-circulatory loop proximal to a Björk-Shiley monostrut valve in the mitral position, and synchronous ensemble-averaging was applied to form an "average" beat. Two axial locations in the regurgitant flow region of the valve (in the minor orifice) were mapped, and maximum Reynolds shear stresses were calculated. A large spike in regurgitant flow was noted at the beginning of systole, which may be the squeeze flow phenomenon computed by other researchers. A region of sustained regurgitant flow 50 msec later was the focus of this study. Maximum velocities of approximately 3.7 mps were noted, and maximum Reynolds shear stresses of approximately 10,000 dyne/cm2 were calculated. Comparisons were made of two-dimensional (ignoring tangential component) versus three-dimensional shear stresses, and, in this case, in regions of high stress, the differences were insignificant. This suggests that the tangential component of velocity can probably be ignored in similar measurements where the tangential velocity is likely to be small.

Effects of tilting disk heart valve gap width on regurgitant flow through an artificial heart mitral valve

While many investigators have measured the turbulent stresses associated with forward flow through tilting disk heart valves, only recently has attention been given to the regurgitant jets formed as fluid is squeezed through the gap between the occluder and housing of a closed valve. The objective of this investigation was to determine the effect of gap width on the turbulent stresses of the regurgitant jets through a Björk-Shiley monostrut tilting disk heart valve seated in the mitral position of a Penn State artificial heart. A 2 component laser-Doppler velocimetry system with a temporal resolution of 1 ms was used to measure the instantaneous velocities in the regurgitant jets in the major and minor orifices around the mitral valve. The gap width was controlled through temperature variation by taking advantage of the large difference between the thermal expansion coefficients of the Delrin occluder and the Stellite housing of Björk-Shiley monostrut valves. The turbulent shear stress and mean (ensemble averaged) velocity were incorporated into a model of red blood cell damage to assess the potential for hemolytic damage at each gap width investigated. The results revealed that the minor orifice tends to form stronger jets during regurgitant flow than the major orifice, indicating that the gap width is not uniform around the circumference of the valve. Based on the results of a red blood cell damage model, the hemolytic potential of the mitral valve decreases as the gap width increases. This investigation also established that the hemolytic potential of the regurgitant phase of valve operation is comparable to, if not greater than, the hemolytic potential of forward flow, consistent with experimental data on hemolysis.

Electromagnetic field cancer scares

The internal electric current or power levels that a human is likely to encounter in a typical electromagnetic field environment are calculated. At 60 Hz, a reasonable value for maximum permissible exposure is an internal current density of 1 microA cm(-2). At this frequency, a 600 V m(-1) electric field results in a current density of 0.0002 microA cm(-2), while a 200 microT magnetic field results in 0.6 microA cm(-2). This should be compared with an action potential, which is associated with a current density of 800 microA cm(-2). The ANSI/IEEE C95.1-1991 standards, whose frequency range is 3 kHz to 300 GHz, are examined. Epidemiological studies are briefly considered. The conclusion is that it is highly unlikely that there is a link between electromagnetic fields and cancer.

In vivo observation of cavitation on prosthetic heart valves

In this study, a method to determine the existence of prosthetic heart valve cavitation in vivo is presented. Pennsylvania State University Left Ventricular Assist Devices (LVADs) were implanted in two separate calves for this study. Björk-Shiley Monostrut (Irvine, CA) 27 mm and 25 mm valves with Delrin occluders were used in the mitral and aortic positions, respectively. A high fidelity, piezoelectric pressure transducer was mounted approximately 1.25 cm proximal to the mitral valve and measured the high frequency pressure fluctuations caused by cavitation bubble formation and collapse after valve closure. The root mean square (RMS) value of the mitral pressure signal during a 5 ms interval after valve closure was used as a measure of cavitation intensity. The pressure signals observed in vivo were similar to ones observed in vitro with the same type of pressure transducer and were associated with the visually observed cavitation. The percentage of beats with cavitation increased from 20.3% to 67.7% when pump filling was decreased by increasing beat rate. A blood test conducted during post-operative days 1-3 showed a significant increase in plasma hemoglobin during the low filling condition. However, blood tests conducted later (post-operative days 7-44) did not show a significant change in plasma hemoglobin during low filling conditions.

Mitral heart valve cavitation in an artificial heart environment

BACKGROUND AND AIMS OF THE STUDY

The formation and subsequent collapse of vaporous cavities in the fluid around mechanical heart valves at valve closure can create stresses large enough to damage both the valve itself and blood cells. Improved understanding of cavitation mechanisms should lead to a reduction in the cavitation potential of future valve designs.

MATERIALS AND METHODS

This study compares eight mechanical mitral valves of two different geometries (Monostrut and Medtronic Hall), occluder housing gaps (tight, medium, and leaky), and occluder materials (Delrin and pyrolytic carbon). The valves were evaluated in a model ventricle of the Penn State Electric Ventricular Assist Device (EVAD) operating within a mock circulatory loop. The EVAD represents one half of a total artificial heart. The mock loop consisted of silicone tubing connected to elements designed to mimic the compliant and resistant properties of the natural circulation. Cavitation was controlled by varying the degree of filling of the ventricle: low filling caused higher valve closing velocities resulting in greater cavitation intensities than complete filling of the ventricle. The intensity of cavitation was quantified using a parameter derived from the high frequency fluctuations in the mitral pressure that occur around the valve during cavitation events. The shape of the cavitation pressure signature and that of the power spectrum of the cavitation pressure signature were used in addition to the cavitation intensity parameter to make comparisons between valves.

RESULTS

Of the three valve characteristics studied, occluder material showed the most significant influence on cavitation intensity: valves with pyrolytic carbon occluders demonstrated greater cavitation than did those with Delrin discs.

CONCLUSION

It is hypothesized that the dominant form of cavitation on the valves studied is related to vortex formation and that occluder material influences the intensity of cavitation through the strength of the tension wave generated at valve closure, while geometry and gap have only secondary effects. Future studies are planned to incorporate this technique in an in vivo environment.

Alterations in brain monoamines and GABAA receptors in transgenic mice overexpressing TGF alpha

This study investigated the possibility that overexpression of transforming growth factor alpha (TGF alpha) changes those neurotransmitter systems that have been associated with behaviors found to be altered in the transgenic TGF alpha CD-1 mice. The female TGF alpha mice showed elevated levels of norepinephrine (NE) in the hypothalamus and serotonin (5-HT) in the cortex and brain stem when compared with nontransgenic CD-1 females. The concentrations of monoamines were not altered in the male transgenic brain. The 5-hydroxyindoleacitic acid (5-HIAA)/5-HT ratio was significantly reduced in the brain stem of the male TGF alpha mice and frontal cortex in the female transgenics. The binding of the [3H]GBR 12935-labeled DA transporter was lower in the frontal cortex in the transgenic male TGF alpha mice than in the female TGF alpha mice. No gender difference in dopamine (DA) transporter binding was noted between the nontransgenic male and female mice. Serotonin and GABAA receptors were measured only in males. No differences in the number of 5-HT1A and 5-HT2 receptors were found in the cortex or hippocampus. Maximal GABA stimulation of [3H]flunitrazepam binding in the forebrain hemispheres and cerebellar binding of an imidazobenzodiazepine, [3H]Ro 15-4513, were not different between transgenic and nontransgenic male mice. However, forebrain [35S]TBPS binding in male TGF alpha mice was less affected by the blockade of the GABA agonist sites by the specific GABAA antagonists SR 95531 and bicuculline than the binding of the controls, suggesting either altered endogenous GABA concentrations or a change in receptor populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Luteal phase defects and ectopic pregnancy

OBJECTIVE

To determine whether luteal phase defect (LPD) may be an etiologic factor in ectopic pregnancy (EP).

DESIGN

All patients who were seen over a 6-year period with the chief complaint of infertility underwent an extensive infertility workup and were followed prospectively. The diagnoses of the causes of infertility were assigned retrospectively.

SETTING

Two hospital-based tertiary care reproductive endocrine-infertility units.

PATIENTS

A total of 1,077 infertility patients were evaluated. Of the 633 who became pregnant, the infertility had been due to LPD in 51 and to anovulation in 210.

MAIN OUTCOME MEASURES

All the infertility patients who became pregnant were followed to determine whether they miscarried, developed an EP, or had a viable birth. The incidence of EP and miscarriage in the patients whose infertility was found to be due to LPD were compared with a control group in whom the infertility was due to anovulation.

RESULTS

The EP rate in the patients with LPD was significantly higher than in a control group whose infertility was due to anovulation (6 of 51 pregnancies versus 6 of 210 pregnancies, respectively). The spontaneous abortion rate in LPD cases also was highly significantly greater than in the control group (19 of 51 pregnancies versus 12 of 210 pregnancies, respectively). The EP and spontaneous abortion rates also were higher in patients with LPD who were untreated than in those who were treated.

CONCLUSIONS

This study suggests that there is a significantly increased incidence of tubal EP in patients with LPD and that when patients with LPD become pregnant early ultrasound should be performed to rule out EP. The study also indicated that spontaneous abortion occurs in a significantly high percentage of LPD cases.

A method for real-time in vitro observation of cavitation on prosthetic heart valves

A method for real-time in vitro observation of cavitation on a prosthetic heart valve has been developed. Cavitation of four blood analog fluids (distilled water, aqueous glycerin, aqueous polyacrylamide, and aqueous xanthan gum) has been documented for a Medtronic/Hall prosthetic heart valve. This method employed a Penn State Electrical Ventricular Assist Device in a mock circulatory loop that was operated in a partial filling mode associated with reduced atrial filling pressure. The observations were made on a valve that was located in the mitral position, with the cavitation occurring on the inlet side after valve closure on every cycle. Stroboscopic videography was used to document the cavity life cycle. Bubble cavitation was observed on the valve occluder face. Vortex cavitation was observed at two locations in the vicinity of the valve occluder and housing. For each fluid, cavity growth and collapse occurred in less than one millisecond, which provides strong evidence that the cavitation is vaporous rather than gaseous. The cavity duration time was found to decrease with increasing atrial pressure at constant aortic pressure and beat rate. The area of cavitation was found to decrease with increasing delay time at a constant aortic pressure, atrial pressure, and beat rate. Cavitation was found to occur in each of the fluids, with the most cavitation seen in the Newtonian fluids (distilled water and aqueous glycerin).