Applying a genetic risk score model to enhance prediction of future multiple sclerosis diagnosis at first presentation with optic neuritis

Optic neuritis (ON) is associated with numerous immune-mediated inflammatory diseases, but 50% patients are ultimately diagnosed with multiple sclerosis (MS). Differentiating MS-ON from non-MS-ON acutely is challenging but important; non-MS ON often requires urgent immunosuppression to preserve vision. Using data from the United Kingdom Biobank we showed that combining an MS-genetic risk score (GRS) with demographic risk factors (age, sex) significantly improved MS prediction in undifferentiated ON; one standard deviation of MS-GRS increased the Hazard of MS 1.3-fold (95% confidence interval 1.07-1.55, P < 0.01). Participants stratified into quartiles of predicted risk developed incident MS at rates varying from 4% (95%CI 0.5-7%, lowest risk quartile) to 41% (95%CI 33-49%, highest risk quartile). The model replicated across two cohorts (Geisinger, USA, and FinnGen, Finland). This study indicates that a combined model might enhance individual MS risk stratification, paving the way for precision-based ON treatment and earlier MS disease-modifying therapy.

Hyperglycaemia is a causal risk factor for upper limb pathologies

BACKGROUND

Diabetes (regardless of type) and obesity are associated with a range of musculoskeletal disorders. The causal mechanisms driving these associations are unknown for many upper limb pathologies. We used genetic techniques to test the causal link between glycemia, obesity and musculoskeletal conditions.

METHODS

In the UK Biobank's unrelated European cohort (N = 379 708) we performed mendelian randomisation (MR) analyses to test for a causal effect of long-term high glycaemia and adiposity on four musculoskeletal pathologies: frozen shoulder, Dupuytren's disease, carpal tunnel syndrome and trigger finger. We also performed single-gene MR using rare variants in the GCK gene.

RESULTS

Using MR, we found evidence that long-term high glycaemia has a causal role in the aetiology of upper limb conditions. A 10-mmol/mol increase in genetically predicted haemoglobin A1C (HbA1c) was associated with frozen shoulder: odds ratio (OR) = 1.50 [95% confidence interval (CI), 1.20-1.88], Dupuytren's disease: OR = 1.17 (95% CI, 1.01-1.35), trigger finger: OR = 1.30 (95% CI, 1.09-1.55) and carpal tunnel syndrome: OR = 1.20 (95% CI, 1.09-1.33). Carriers of GCK mutations have increased odds of frozen shoulder: OR = 7.16 (95% CI, 2.93-17.51) and carpal tunnel syndrome: OR = 2.86 (95% CI, 1.50-5.44) but not Dupuytren's disease or trigger finger. We found evidence that an increase in genetically predicted body mass index (BMI) of 5 kg/m2 was associated with carpal tunnel syndrome: OR = 1.13 (95% CI, 1.10-1.16) and associated negatively with Dupuytren's disease: OR = 0.94 (95% CI, 0.90-0.98), but no evidence of association with frozen shoulder or trigger finger. Trigger finger (OR 1.96 (95% CI, 1.42-2.69) P = 3.6e-05) and carpal tunnel syndrome [OR 1.63 (95% CI, 1.36-1.95) P = 8.5e-08] are associated with genetically predicted unfavourable adiposity increase of one standard deviation of body fat.

CONCLUSIONS

Our study consistently demonstrates a causal role of long-term high glycaemia in the aetiology of upper limb musculoskeletal conditions. Clinicians treating diabetes patients should be aware of these complications in clinic, specifically those managing the care of GCK mutation carriers. Upper limb musculoskeletal conditions should be considered diabetes complications.

Influence of family history on penetrance of hereditary cancers in a population setting

Background

We sought to investigate how penetrance of familial cancer syndromes varies with family history using a population-based cohort.

Methods

We analysed 454,712 UK Biobank participants with exome sequence and clinical data (data collected between March 2006 and June 2021). We identified participants with a self-reported family history of breast or colorectal cancer and a pathogenic/likely pathogenic variant in the major genes responsible for hereditary breast cancer or Lynch syndrome. We calculated survival to cancer diagnosis (controlled for sex, death, recruitment centre, screening and prophylactic surgery).

Findings

Women with a pathogenic BRCA1 or BRCA2 variant had an increased risk of breast cancer that was higher in those with a first-degree family history (relative hazard 10.3 and 7.8, respectively) than those without (7.2 and 4.7). Penetrance to age 60 was also higher in those with a family history (44.7%, CI 32.2-59.3 and 24.1%, CI 17.5-32.6) versus those without (22.8%, CI 15.9-32.0 and 17.9%, CI 13.8-23.0). A similar pattern was seen in Lynch syndrome: individuals with a pathogenic MLH1, MSH2 or MSH6 variant had an increased risk of colorectal cancer that was significantly higher in those with a family history (relative hazard 35.6, 48.0 and 9.9) than those without (13.0, 15.4 and 7.2). Penetrance to age 60 was also higher for carriers of a pathogenic MLH1 or MSH2 variant in those with a family history (30.9%, CI 18.1-49.3 and 38.3%, CI 21.5-61.8) versus those without (20.5% CI 9.6-40.5 and 8.3% CI 2.1-30.4), but not for MSH6 (6.5% CI 2.7-15.1 with family history versus 8.3%, CI 5.1-13.2). Relative risk increases were also observed both within and across conditions.

Interpretation

Individuals with pathogenic cancer syndrome variants may be at a less elevated risk of cancer in the absence of a first-degree family history, so in the context of results return, family history should be considered when counselling patients on the risks and benefits of potential follow-up care.

Funding

The current work is supported by the MRC (grant no MR/T00200X/1). The MRC had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

The effect of pregnancy vitamin D supplementation on offspring bone mineral density in childhood: a systematic review and meta-analysis

Systematic review and meta-analysis of the effect of moderate- to high-dose vitamin D supplementation in pregnancy on offspring bone mineralisation found a positive effect of vitamin D supplementation on offspring bone mineral density (BMD) at age 4-6 years, with a smaller effect on bone mineral content.

PURPOSE

A systematic review and meta-analysis was performed to assess the effect of pregnancy vitamin D supplementation on offspring bone mineral density (BMD) in childhood.

METHODS

A literature search was conducted for published RCTs of antenatal vitamin D supplementation with assessment of offspring BMD or bone mineral content (BMC) by dual-energy X-ray absorptiometry (DXA) using MEDLINE and EMBASE up to 13th July 2022. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool. Study findings were grouped in two age groups of offspring assessment: neonatal period and early childhood (3-6 years). Random-effects meta-analysis of the effect on BMC/BMD at 3-6 years was performed using RevMan 5.4.1, yielding standardised mean difference (SMD) (95% CI).

RESULTS

Five RCTs were identified with offspring assessment of BMD or BMC; 3250 women were randomised within these studies. Risk of bias was low in 2 studies and "of concern" in 3. Supplementation regimes and the control used (3 studies used placebo and 2 used 400 IU/day cholecalciferol) varied, but in all studies the intervention increased maternal 25-hydroxvitamin D status compared to the control group. Two trials assessing BMD in the neonatal period (total n = 690) found no difference between groups, but meta-analysis was not performed as one trial represented 96.4% of those studied at this age. Three trials assessed offspring whole-body-less-head BMD at age 4-6 years. BMD was higher in children born to mothers supplemented with vitamin D [0.16 SD (95% confidence interval 0.05, 0.27), n = 1358] with a smaller effect on BMC [0.07 SD (95% CI - 0.04, 0.19), n = 1351].

CONCLUSIONS

There are few RCTs published to address this question, and these are inconsistent in methodology and findings. However, meta-analysis of three trials suggests moderate- to high-dose vitamin D supplementation in pregnancy might increase offspring BMD in early childhood, but further trials are required to confirm this finding. (Prospero CRD42021288682; no funding received).

Genetically defined favourable adiposity is not associated with a clinically meaningful difference in clinical course in people with type 2 diabetes but does associate with a favourable metabolic profile

AIMS

Change in weight, HbA_1c , lipids, blood pressure and cardiometabolic events over time is variable in individuals with type 2 diabetes. We hypothesised that people with a genetic predisposition to a more favourable adiposity distribution could have a less severe clinical course/progression.

METHODS

We involved people with type 2 diabetes from two UK-based cohorts: 11,914 individuals with GP follow-up data from the UK Biobank and 723 from Salford. We generated a 'favourable adiposity' genetic score and conducted cross-sectional and longitudinal studies to test its association with weight, BMI, lipids, blood pressure, medication use and risk of myocardial infarction and stroke using 15 follow-up time points with 1-year intervals.

RESULTS

The 'favourable adiposity' genetic score was cross-sectionally associated with higher weight (effect size per 1 standard deviation higher genetic score: 0.91 kg [0.59,1.23]) and BMI (0.30 kg/m² [0.19,0.40]), but higher high-density lipoprotein (0.02 mmol/L [0.01,0.02]) and lower triglycerides (-0.04 mmol/L [-0.07, -0.02]) in the UK Biobank at baseline, and this pattern of association was consistent across follow-up. There was a trend for participants with higher 'favourable adiposity' genetic score to have lower risk of myocardial infarction and/or stroke (odds ratio 0.79 [0.62, 1.00]) compared to those with lower score. A one standard deviation higher score was associated with lower odds of using lipid-lowering (0.91 [0.86, 0.97]) and anti-hypertensive medication (0.95 [0.91, 0.99]).

CONCLUSIONS

In individuals with type 2 diabetes, having more 'favourable adiposity' alleles is associated with a marginally better lipid profile long-term and having lower odds of requiring lipid-lowering or anti-hypertensive medication in spite of relatively higher adiposity.

A genome-wide association study identifies 5 loci associated with frozen shoulder and implicates diabetes as a causal risk factor

Frozen shoulder is a painful condition that often requires surgery and affects up to 5% of individuals aged 40-60 years. Little is known about the causes of the condition, but diabetes is a strong risk factor. To begin to understand the biological mechanisms involved, we aimed to identify genetic variants associated with frozen shoulder and to use Mendelian randomization to test the causal role of diabetes. We performed a genome-wide association study (GWAS) of frozen shoulder in the UK Biobank using data from 10,104 cases identified from inpatient, surgical and primary care codes. We used data from FinnGen for replication and meta-analysis. We used one-sample and two-sample Mendelian randomization approaches to test for a causal association of diabetes with frozen shoulder. We identified five genome-wide significant loci. The most significant locus (lead SNP rs28971325; OR = 1.20, [95% CI: 1.16-1.24], p = 5x10-29) contained WNT7B. This variant was also associated with Dupuytren's disease (OR = 2.31 [2.24, 2.39], p<1x10-300) as were a further two of the frozen shoulder associated variants. The Mendelian randomization results provided evidence that type 1 diabetes is a causal risk factor for frozen shoulder (OR = 1.03 [1.02-1.05], p = 3x10-6). There was no evidence that obesity was causally associated with frozen shoulder, suggesting that diabetes influences risk of the condition through glycemic rather than mechanical effects. We have identified genetic loci associated with frozen shoulder. There is a large overlap with Dupuytren's disease associated loci. Diabetes is a likely causal risk factor. Our results provide evidence of biological mechanisms involved in this common painful condition.

Genetic evidence that higher central adiposity causes gastro-oesophageal reflux disease: a Mendelian randomization study

Background

Gastro-oesophageal reflux disease (GORD) is associated with multiple risk factors but determining causality is difficult. We used a genetic approach [Mendelian randomization (MR)] to identify potential causal modifiable risk factors for GORD.

Methods

We used data from 451 097 European participants in the UK Biobank and defined GORD using hospital-defined ICD10 and OPCS4 codes and self-report data (N = 41 024 GORD cases). We tested observational and MR-based associations between GORD and four adiposity measures [body mass index (BMI), waist–hip ratio (WHR), a metabolically favourable higher body-fat percentage and waist circumference], smoking status, smoking frequency and caffeine consumption.

Results

Observationally, all adiposity measures were associated with higher odds of GORD. Ever and current smoking were associated with higher odds of GORD. Coffee consumption was associated with lower odds of GORD but, among coffee drinkers, more caffeinated-coffee consumption was associated with higher odds of GORD. Using MR, we provide strong evidence that higher WHR and higher WHR adjusted for BMI lead to GORD. There was weak evidence that higher BMI, body-fat percentage, coffee drinking or smoking caused GORD, but only the observational effects for BMI and body-fat percentage could be excluded. This MR estimated effect for WHR equates to a 1.23-fold higher odds of GORD per 5-cm increase in waist circumference.

Conclusions

These results provide strong evidence that a higher waist–hip ratio leads to GORD. Our study suggests that central fat distribution is crucial in causing GORD rather than overall weight.

Clinical Features and Genetic Risk of Demyelination Following Anti-TNF Treatment

BACKGROUND

Anti-TNF exposure has been linked to demyelination events. We sought to describe the clinical features of demyelination events following anti-TNF treatment and to test whether affected patients were genetically predisposed to multiple sclerosis [MS].

METHODS

We conducted a case-control study to describe the clinical features of demyelination events following anti-TNF exposure. We compared genetic risk scores [GRS], calculated using carriage of 43 susceptibility loci for MS, in 48 cases with 1219 patients exposed to anti-TNF who did not develop demyelination.

RESULTS

Overall, 39 [74%] cases were female. The median age [range] of patients at time of demyelination was 41.5 years [20.7-63.2]. The median duration of anti-TNF treatment was 21.3 months [0.5-99.4] and 19 [36%] patients were receiving concomitant immunomodulators. Most patients had central demyelination affecting the brain, spinal cord, or both. Complete recovery was reported in 12 [23%] patients after a median time of 6.8 months [0.1-28.7]. After 33.0 months of follow-up, partial recovery was observed in 29 [55%] patients, relapsing and remitting episodes in nine [17%], progressive symptoms in three [6%]: two [4%] patients were diagnosed with MS. There was no significant difference between MS GRS scores in cases (mean -3.5 × 10-4, standard deviation [SD] 0.0039) and controls [mean -1.1 × 10-3, SD 0.0042] [p = 0.23].

CONCLUSIONS

Patients who experienced demyelination events following anti-TNF exposure were more likely female, less frequently treated with an immunomodulator, and had a similar genetic risk to anti-TNF exposed controls who did not experience demyelination events. Large prospective studies with pre-treatment neuroimaging are required to identify genetic susceptibility loci.

Quality improvement project identifies factors associated with delay in IBD diagnosis

BACKGROUND

Delay in the diagnosis of inflammatory bowel disease (IBD) is common and contemporary UK studies are lacking.

AIM

To determine factors associated with, and the consequences of, a prolonged time to diagnosis in IBD.

METHODS

This quality improvement study included 304 adults with a new IBD diagnosis made between January 2014 and December 2017 across 49 general practices (GP) and gastroenterology secondary care services. Outcome measures were demographic, clinical and laboratory factors associated with a delayed time, defined as greater than upper quartile, to: (a) patient presentation (b) GP referral (c) secondary care diagnosis, and factors associated with a complicated disease course (hospitalisation and/or surgery and/or biologic treatment) in the year after diagnosis.

RESULTS

The median [IQR] diagnosis sub-intervals were: (a) patient = 2.1 months [0.9-5.1]; (b) GP = 0.3 months [0.0-0.9]; (c) secondary care = 1.1 months [0.5-2.1]. 50% of patients were diagnosed within 4 months and 92% were diagnosed within 2 years of symptom onset. Diagnostic delay was more common in Crohn's disease (7.6 months [3.1-15.0]) than ulcerative colitis (3.3 months [1.9-7.3]) (P < 0.001). Patients who presented as an emergency (P < 0.001) but not those with a delayed overall time to diagnosis (P = 0.35) were more likely to have a complicated disease course.

CONCLUSION

Time to patient presentation is the largest component of time to IBD diagnosis. Emergency presentation is common and, unlike a delayed time to diagnosis, is associated with a complicated disease course.

Genome-Wide Association Study of Microscopic Colitis in the UK Biobank Confirms Immune-Related Pathogenesis

BACKGROUND AND AIMS

The causes of microscopic colitis are currently poorly understood. Previous reports have found clinical associations with coeliac disease and genetic associations at the human leukocyte antigen [HLA] locus on the ancestral 8.1 haplotype. We investigated pharmacological and genetic factors associated with microscopic colitis in the UK Biobank.

METHODS

In total, 483 European UK Biobank participants were identified by ICD10 coding, and a genome-wide association study was performed using BOLT-LMM, with a sensitivity analysis performed excluding potential confounders. The HLA*IMP:02 algorithm was used to estimate allele frequency at 11 classical HLA genes, and downstream analysis was performed using FUMA. Genetic overlap with inflammatory bowel disease [Crohn's disease and ulcerative colitis] was investigated using genetic risk scores.

RESULTS

We found significant phenotypic associations with smoking status, coeliac disease and the use of proton-pump inhibitors but not with other commonly reported pharmacological risk factors. Using the largest sample size to date, we confirmed a recently reported association with the MHC Ancestral 8.1 Haplotype. Downstream analysis suggests association with digestive tract morphogenesis. By calculating genetic risk scores, we also report suggestive evidence of shared genetic risk with Crohn's disease, but not with ulcerative colitis.

CONCLUSIONS

This report confirms the role of genetic determinants in the HLA in the pathogenesis of microscopic colitis. The genetic overlap with Crohn's disease suggests a common underlying mechanism of disease.

Predictors of anti-TNF treatment failure in anti-TNF-naive patients with active luminal Crohn's disease: a prospective, multicentre, cohort study

BACKGROUND

Anti-TNF drugs are effective treatments for the management of Crohn's disease but treatment failure is common. We aimed to identify clinical and pharmacokinetic factors that predict primary non-response at week 14 after starting treatment, non-remission at week 54, and adverse events leading to drug withdrawal.

METHODS

The personalised anti-TNF therapy in Crohn's disease study (PANTS) is a prospective observational UK-wide study. We enrolled anti-TNF-naive patients (aged ≥6 years) with active luminal Crohn's disease at the time of first exposure to infliximab or adalimumab between March 7, 2013, and July 15, 2016. Patients were evaluated for 12 months or until drug withdrawal. Demographic data, smoking status, age at diagnosis, disease duration, location, and behaviour, previous medical and drug history, and previous Crohn's disease-related surgeries were recorded at baseline. At every visit, disease activity score, weight, therapy, and adverse events were recorded; drug and total anti-drug antibody concentrations were also measured. Treatment failure endpoints were primary non-response at week 14, non-remission at week 54, and adverse events leading to drug withdrawal. We used regression analyses to identify which factors were associated with treatment failure.

FINDINGS

We enrolled 955 patients treated with infliximab (753 with originator; 202 with biosimilar) and 655 treated with adalimumab. Primary non-response occurred in 295 (23·8%, 95% CI 21·4-26·2) of 1241 patients who were assessable at week 14. Non-remission at week 54 occurred in 764 (63·1%, 60·3-65·8) of 1211 patients who were assessable, and adverse events curtailed treatment in 126 (7·8%, 6·6-9·2) of 1610 patients. In multivariable analysis, the only factor independently associated with primary non-response was low drug concentration at week 14 (infliximab: odds ratio 0·35 [95% CI 0·20-0·62], p=0·00038; adalimumab: 0·13 [0·06-0·28], p<0·0001); the optimal week 14 drug concentrations associated with remission at both week 14 and week 54 were 7 mg/L for infliximab and 12 mg/L for adalimumab. Continuing standard dosing regimens after primary non-response was rarely helpful; only 14 (12·4% [95% CI 6·9-19·9]) of 113 patients entered remission by week 54. Similarly, week 14 drug concentration was also independently associated with non-remission at week 54 (0·29 [0·16-0·52] for infliximab; 0·03 [0·01-0·12] for adalimumab; p<0·0001 for both). The proportion of patients who developed anti-drug antibodies (immunogenicity) was 62·8% (95% CI 59·0-66·3) for infliximab and 28·5% (24·0-32·7) for adalimumab. For both drugs, suboptimal week 14 drug concentrations predicted immunogenicity, and the development of anti-drug antibodies predicted subsequent low drug concentrations. Combination immunomodulator (thiopurine or methotrexate) therapy mitigated the risk of developing anti-drug antibodies (hazard ratio 0·39 [95% CI 0·32-0·46] for infliximab; 0·44 [0·31-0·64] for adalimumab; p<0·0001 for both). For infliximab, multivariable analysis of immunododulator use, and week 14 drug and anti-drug antibody concentrations showed an independent effect of immunomodulator use on week 54 non-remission (odds ratio 0·56 [95% CI 0·38-0·83], p=0·004).

INTERPRETATION

Anti-TNF treatment failure is common and is predicted by low drug concentrations, mediated in part by immunogenicity. Clinical trials are required to investigate whether personalised induction regimens and treatment-to-target dose intensification improve outcomes.

FUNDING

Guts UK, Crohn's and Colitis UK, Cure Crohn's Colitis, AbbVie, Merck Sharp and Dohme, Napp Pharmaceuticals, Pfizer, and Celltrion.

Signal Reconstruction of Pulmonary Vein Recordings Using a Phenomenological Mathematical Model: Application to Pulmonary Vein Isolation Therapy

Atrial fibrillation (AF), the most prevalent cardiac arrhythmia, is commonly initiated by ectopic beats originating from a small myocardial sleeve extending over the pulmonary veins. Pulmonary vein isolation therapy attempts to isolate the pulmonary veins from the left atrium by ablating tissue, commonly by using radiofrequency ablation. During this procedure, the cardiologist records electrical activity using a lasso catheter, and the activation pattern recorded is used as a guide toward which regions to ablate. However, poor contact between electrode and tissue can lead to important regions of electrical activity not being recorded in clinic. We reproduce these signals through the use of a phenomenological model of the cardiac action potential on a cylinder, which we fit to post-AF atrial cells, and model the bipolar electrodes of the lasso catheter by an approximation of the surface potential. The resulting activation pattern is validated by direct comparison with those of clinical recordings. A potential application of the model is to reconstruct the missing electrical activity, minimizing the impact of the information loss on the clinical procedure, and we present results to demonstrate this.

Treatment of supracondylar femoral fractures with a retrograde intramedullary nail

From August 1992 to January 1995, 24 patients with 26 supracondylar femoral fractures were treated with a retrograde intramedullary nail. There were 22 patients with 24 nails available for review. Eight fractures were open and 13 were intraarticular fractures. There were a significant number of associated injuries. The average followup interval was 18 months (range, 4-36 months). All fractures healed by 4 months, (average, 3 months). Only 1 patient required bone grafting. There were no implant failures or superficial or deep infections. One malunion occurred. Average knee range of motion was 104 degrees. A previously described rating scale was used to evaluate function. There were 4 excellent, 16 good, 2 fair, and 2 poor results. The supracondylar nail provides rigid internal fixation for rapid healing and comparable functional outcomes to lateral fixation devices with significantly less soft tissue dissection.

Prevention of venous thromboembolism in orthopaedics in the United States

The use of different types of antithrombotic prophylactics in various clinical settings was examined. A standardized questionnaire was mailed to 5000 randomly selected practicing orthopaedic surgeons that detailed practice profile, surgical case type and frequency, method of thromboembolism prophylaxis used, incidence of morbidity, and type of screening used. Twenty-one percent (n = 1046) of surgeons surveyed returned the questionnaire. Four of 5 surgeons performing elective hip arthroplasty used some form of thromboembolic prophylaxis for all of their patients, 13% used prophylaxis only for patients considered to be at high risk, and 3% of respondents never used prophylaxis. The rates of prophylactic use for patients undergoing elective knee arthroplasty were similar. A considerably lower rate of routine prophylactic use was seen among surgeons performing surgery for pelvic and lower extremity trauma. Except for cases involving neurologic compromise, most patients undergoing either elective or traumatic spinal surgery were not given prophylaxis. Low dose warfarin alone was the most commonly used prophylaxis modality. A comparison of the results of the current survey with those of past surveys showed that the use of aspirin has fallen. The use of routine pharmacologic prophylaxis against thromboembolism in hip and knee arthroplasty has become the standard of care in the United States. Among patients undergoing surgery for hip fracture and other lower extremity trauma, however, prophylaxis remains underused.

Gorham's disease: a literature review and case reports

Gorham's disease (disappearing bone disease, massive osteolysis, idiopathic osteolysis, essential osteolysis, progressive atrophy of bone, spontaneous absorption of bone, phantom bone, hemangiomatosis/lymphangiomatosis of bone, progressive osteolysis) is an extremely rare occurrence. There are fewer than 150 reported cases in the literature. This disorder can be characterized by spontaneous or posttraumatic progressive resorption of bone. The etiology is still very speculative, the prognosis unpredictable, and any effective therapy still unknown. This paper presents a review of the literature and two case reports of suspected Gorham's disease of the bones of the foot.

Postoperative infections in asymptomatic HIV-seropositive orthopedic trauma patients

In a retrospective study of 476 surgical orthopedic trauma patients, we compared postoperative infection rates between individuals seropositive for the human immunodeficiency virus (HIV) and with no associated clinical symptoms with HIV-seronegative patients. Overall, the surgical postoperative infection rate was 16.7% in seropositive patients and 5.4% in the seronegative group (Chi-square, p = 0.035). When open fractures were considered separately, the seropositive group had a 55.6% infection rate compared with 11.3% in the seronegative group (Fisher's exact test, p = 0.004). Similarly, seropositive patients also had significantly increased rates of postoperative non-wound infections and complications (Chi-square p < 0.001). Asymptomatic HIV-seropositive orthopedic trauma patients are at significantly higher risk for postoperative infections than their seronegative counterparts. For HIV-seropositive patients with open fractures, this risk is especially pronounced.

The influence of radiographic projection on the appearance of deformities

In a series of 100 malunions and nonunions, the authors found, on average, that the worst deformity visualized radiographically underestimated the true deformity by 14% (range of 0% to 41.4%). By recomputing the analysis as though four views (anteroposterior, lateral, both 45% obliques) had been obtained, the visualization error was reduced from 14% to 2.5%. The authors recommended either obtaining the aforementioned four views when planning a complex deformity correction, or, better yet, obtain the radiographic projection that shows each deformity in profile.

Pulse wave velocity and morphological changes associated with early atherosclerosis progression in the aortas of cynomolgus monkeys

To determine the time course of changes in arterial stiffness and corresponding morphology during atherosclerosis progression, we determined pulse wave velocity (PWV) in cynomolgus monkeys fed atherogenic (test) and control diets over an 18-month period. At 6-month intervals, thoracic and abdominal aortic PWVs were determined with a pressure transducer retracted down the aorta in 5 cm increments. Iliac artery PWV was determined from the abdominal aortic pressure to a noninvasive femoral pulse. Groups of individual cardiac cycles, triggered by the ECGs, were sampled on a computer and the velocities (PWV) of the pulse wave fronts were calculated. There was no significant difference between groups until 18 months when test animal PWVs in the thoracic (7.44 +/- 0.83 m X s-1) and abdominal (8.52 +/- 0.67 m X s-1) aorta were significantly greater than those of controls (5.02 +/- 0.51 and 6.24 +/- 0.53 m X s-1, respectively), indicating increased arterial stiffness. There was no change in iliac PWV, 10.96 +/- 0.74 m X s-1 for 18-month test compared with 9.44 +/- 0.89 m X s-1 for controls. Constant infusion of nitroprusside and noradrenaline lowered and raised blood pressure and PWV in all groups, and PWV changes due to drug-induced pressure changes were greater in atherosclerotic than in control arteries. Systolic pressure of 18-month test and pulse pressure of 12- and 18-month test groups were significantly greater than controls under all drug conditions, also indicating increased vessel stiffness. Morphometric evaluation of histological aortic cross sections revealed early, noncomplicated atherosclerosis showing gradual increases in the ratio of intimal to medial cross-sectional area in the thoracic (1.24 +/- 0.30 after 18 months) and abdominal (1.70 +/- 0.42 after 18 months) aortas, compared with control ratios of essentially zero. The fraction of the internal elastic lamina covered with atherosclerotic lesions, and maximal intimal thickness also showed significant increases during the test diet period. These data show that early atherosclerosis resulted in aortic but not iliac stiffening which was detected by increased PWV before development of significant stenotic lesions.

Noninvasively and invasively measured pulsatile haemodynamics with graded arterial stenosis

Pulsatile haemodynamics associated with graded degrees of experimentally produced stenosis were studied in the canine femoral artery. Invasively determined pulsatile blood flow and noninvasively determined blood velocity with Doppler ultrasound were measured an average of 1.3 and 2.3 cm proximal to the stenosis, respectively. Pulsatile blood pressure was measured 0.6 cm proximal and 3.7 cm distal to the stenosis. With increasing severity of stenosis there were progressive increases in the femoral artery hydraulic input impedance moduli and in the ratio of the impedance moduli to the zero harmonic impedance (or total resistance). This resulted in: a) a progressive reduction in the Fourier harmonic moduli and pulsewave amplitudes of flow, velocity, and distal pressure; b) a progressive increase in the fifth-seventh proximal pressure harmonic moduli; but c) little change in mean proximal pressure or its first 4 harmonic moduli. The data confirm the well known phenomena of a 'critical stenosis' in that there is little decrease in resting mean blood flow until there is a 70 to 80 stenosis (area reduction). Also the oscillatory portions of the femoral artery data were more sensitive to the changes in stenosis than were the nonoscillatory parameters, which confirms previously reported findings from the thoracic aorta. However, the femoral artery haemodynamics exhibited a greater amount of frequency dependent behaviour than the thoracic aorta which is probably the result of a more complex interaction of reflections from the stenosis and from the periphery in the femoral artery than in the thoracic aorta. The sensitive changes in oscillatory haemodynamics may provide a useful basis for noninvasive and invasive physiological assessment of human peripheral atherosclerotic stenosis and of experimental stenosis in animals.

The role of coronary adrenergic receptors in the response to nitroglycerine and the regulation of large and small vessel resistance

The role of coronary adrenergic receptors in response to nitroglycerine and in the regulation of large and small coronary vascular resistance was evaluated in two separate studies involving fifteen anesthetized mongrel dog preparations, before and after alpha- and beta-adrenergic blockade, respectively. Coronary blood flow (CBF) was measured through the left anterior descending (LAD) coronary artery by a non-cannulating electromagnetic flow probe. Pressure catheters were inserted into the arch of the aorta and into a distal apical branch of the LAD coronary artery to measure, respectively, aortic pressure (coronary perfusion pressure (PA), peripheral coronary pressure )PC), and coronary artery pressure gradient (PG = PA -PC). End-diastolic resistances to flow were computed as: (a) large coronary end-diastolic resistance (RL = PG/CBF), and (B) small coronary end-diastolic resistance (RS = PC/CBF). Nitroglycerine (NG) alone increased RL to approximately 180--220% of control and reduced RS to about 60% of control, respectively. Following pharmacologic blockade with propranolol (PRO), NG increased RL to about 180% of control and reduced RS to about 60% of control. Following alpha blockade with phenoxybenzamine (PBZ), NG decreased RL to about 78% of control and decreased RS to about 56% of control. It is concluded that while the overall effect of NG on the coronary vascular resistance is one of vasodilation, RL appears to be increased transiently and RS transiently decreased. Alpha adrenergic blockade appears to abolish this response. The increase in RL in response to NG appears to be associated with the systemic hypotensive effect in response to NG. It is proposed that the observed increase in RL is produced by the increase in cardiac sympathetic nerve activity which is initiated by the systemic hypotensive effect of NG.

Aortic pulse wave velocity, elasticity, and composition in a nonhuman primate model of atherosclerosis

Aortic pulse wave velocity was determined in Macaca fascicularis monkeys fed either atherogenic or control diets for 36 months. The foot-to-foot velocity and apparent phase velocities of the second through seventh Fourier harmonics at a given diastolic pressure in the atherosclerotic monkeys were 1.5 to 2.0 times the values for the control animals. More than 80% of the aortic intimal surface of the atherosclerotic monkeys was covered with fibrous or fatty plaque, which approximately doubled wall thickness and wall thickness to radius ratio. Angiochemical evaluations showed no difference in collagen or elastin concentration (as a fraction of lipid and mineral-free dried aorta), but the atherosclerotic aortas were 1.5 to 2.0 times that of control in collagen and elastin content (defined as the absolute quantity beneath a square centimeter of intimal surface). Total cholesterol and calcium concentrations in the atherosclerotic aortas were more than 10 times the values for the control aortas. The static circumferential distensibility of the excised atherosclerotic aortas was significantly less than control, but there was no difference in incremental (Young's) modulus of elasticity. The in vitro pressure-strain elastic modulus of the atherosclerotic aortas was more than twice that of control, which was predicted from the enhanced wave velocity. The significantly increased stiffness of the atherosclerotic arteries appeared to be due mainly to the increased wall thickness caused by the atherosclerotic plaques rather than to material changes described by Young's modulus. Extensive medial damage, however, also was present and could have had a major influence on stiffness. Atherosclerosis therefore can result in increased aortic stiffening, detectable by pulse wave velocity, even if there is no change in the overall Young's modulus of elasticity.

Microvascular control in intestinal mucosa of normal and hemorrhaged rats

The mucosal microcirculation in innervated and denervated small intestine was studied using anesthetized rats. Denervation did not cause significant (P greater than 0.05) diameter changes in the precapillary vasculature; however, venules did constrict significantly. These results indicate minimum neural control in the precapillary vasculature during the resting state. The innervated precapillary vasculature constricted during both the carotid occlusion reflex and hemorrhagic hypotension. The diameter of the denervated precapillary vasculature was unchanged during the carotid occlusion reflex and dilated during hemorrhage. The responses of innervated and denervated precapillary vasculatures were attributed to increased neural activity and autoregulatory mechanisms, respectively. Neither innervated nor denervated venules responded during the carotid occlusion reflex. During hemorrhage, however, innervated venules constricted and denervated vessels dilated. The vasoconstriction of the innervated vasculature during hemorrhage contributed to a stoppage of blood and epithelial detachment; these responses did not occur in the dilated, denervated vasculature. Therefore, neural vasoconstriction, qualitatively similar to that in normal animals during the baroreceptor reflex, is a contributing cause to the vascular and tissue impairment in the intestinal mucosa during hemorrhage.

Amantadine hydrochloride: alteration in peripheral circulation

Livedo reticularis and peripheral edema often have been observed in patients receiving amantadine hydrochloride, suggesting alterations in the responsiveness of peripheral vessels. To investigate this possibility, five patients with Parkinson's disease who had either livedo reticularis or peripheral edema while being treated with amantadine (100 mg twice daily) were evaluated before and after the drug was discontinued. Finger and toe temperatures were significantly lower when patients received the drug than when it was discontinued, and plethysmographic studies showed increased flow in the lower limbs in three patients when the drug was stopped. It is concluded that amantadine therapy may be associated with peripheral vasoconstriction in some patients.

Baroreceptor reflexes and autorregulation of cerebral blood flow in the dog

Cerebral venous outflow was measured in anesthetized dogs at the confluence of the sagittal and straight sinuses, with the lateral sinuses occluded. Denervation of the carotid bifurcation increased systemic arterial pressure (+25.8; SE ±7.7 mm Hg) and decreased cerebral vascular conductance (-0.018; SE ±0.005 ml/min · mm Hg); stimulation of the carotid sinus nerve decreased systemic arterial pressure and increased cerebral vascular conductance. Graded constrictions of the common carotid arteries induced transient responses of the cerebral blood flow that were characteristic of an autoregulatory process. Plots of the steady-state pressures and flows during the decreases of perfusion pressure were concave toward the pressure axis, were similar before and after denervation of the carotid bifurcation, and were indicative of autoregulation.

We conclude that pressoreceptors in the carotid bifurcation or other pressoreceptors in systemic vessels upstream from the carotid bifurcation are not necessary for the control of the "tone" of the cerebral vasculature or in the mechanism of the autoregulation of cerebral blood flow.