Initial clinical experience with the balloon-in-basket pulsed field ablation system: acute results of the VOLT CE mark feasibility study

AIMS

Pulsed field ablation (PFA) for the treatment of atrial fibrillation (AF) potentially offers improved safety and procedural efficiencies compared with thermal ablation. Opportunities remain to improve effective circumferential lesion delivery, safety, and workflow of first-generation PFA systems. In this study, we aim to evaluate the initial clinical experience with a balloon-in-basket, 3D integrated PFA system with a purpose-built form factor for pulmonary vein (PV) isolation.

METHODS AND RESULTS

The VOLT CE Mark Study is a pre-market, prospective, multi-centre, single-arm study to evaluate the safety and effectiveness of the Volt™ PFA system for the treatment of paroxysmal (PAF) or persistent AF (PersAF). Feasibility sub-study subjects underwent phrenic nerve evaluation, endoscopy, chest computed tomography, and cerebral magnetic resonance imaging. Study endpoints were the rate of primary serious adverse event within 7 days and acute procedural effectiveness. A total of 32 subjects (age 61.6 ± 9.6 years, 65.6% male, 84.4% PAF) were enrolled and treated in the feasibility sub-study and completed a 30-day follow-up. Acute effectiveness was achieved in 99.2% (127/128) of treated PVs (96.9% of subjects, 31/32) with 23.8 ± 4.2 PFA applications/subject. Procedure, fluoroscopy, LA dwell, and transpired ablation times were 124.6 ± 28.1, 19.8 ± 8.9, 53.0 ± 21.0, and 48.0 ± 19.9 min, respectively. Systematic assessments of initial safety revealed no phrenic nerve injury, pulmonary vein stenosis, or oesophageal lesions causally related to the PFA system and three subjects with silent cerebral lesions (9.4%). There were no primary serious adverse events.

CONCLUSION

The initial clinical use of the Volt PFA System demonstrates acute safety and effectiveness in the treatment of symptomatic, drug refractory AF.

Utility of a guiding catheter for conduction system pacing: An early multicenter experience

Background

Conduction system pacing (CSP), either as His bundle pacing (HBP) or as left bundle branch area pacing (LBBAP), may be superior to right ventricular apical or septal pacing.

Objective

The study sought to present acute results for a new guiding catheter (Biotronik Selectra 3D) designed for CSP implantations of a retractable screw-in lead (Biotronik Solia S).

Methods

The primary endpoint of the prospective, international nonrandomized BIO|MASTER.Selectra 3D study was freedom from catheter-related serious adverse device effects (SADEs) within 1 week of lead implantation.

Results

Of 157 enrolled patients, CSP was achieved in 147 (93.6%) patients. No SADEs occurred within 7 days. LBBAP was achieved in 82 patients (45 as crossover from an HBP attempt) and HBP in 65 (44.2%) patients. In centers considering both HBP and LBBAP, the CSP implantation success approached 99%. Successful CSP implantations lasted on average ∼50 minutes (fluoroscopy ∼6 minutes). Most procedures (87.9%) needed only 1 catheter, even after switch from HBP to LBBAP. The catheter's handling was rated largely positive. In patients without bundle branch block, mean QRS duration increased from 106 ms (intrinsic) to 122 ms (CSP) (P = .001). In patients with bundle branch block, mean QRS duration decreased from 151 ms (intrinsic) to 137 ms (CSP) (P = .004).

Conclusion

The Selectra 3D catheter is a valuable tool for HBP and LBBAP implantations of the stylet-supported pacemaker leads. When implanters considered both HBP and LBBAP, the success rate was ∼99%. Flexibility to change between different approaches may be advisable in heterogeneous and challenging areas, such as CSP implantations.

Safety and effectiveness of the first contact force ablation catheter with a flexible tip

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex Ablation Catheter, Sensor Enabled (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating fiber optics-based contact force-sensing technology with a flexible, laser-cut tip.

Objective

The study sought to evaluate the safety and effectiveness of the TactiFlex SE ablation catheter for treatment of drug-refractory PAF.

Methods

The TactiFlex AF investigational device exemption was a prospective, nonrandomized, multicenter clinical study. Enrollment began on June 26, 2020 and completed June 18, 2021. Subjects with PAF underwent de novo pulmonary vein isolation and, if indicated, ablation for typical atrial flutter. Subjects were followed for 12 months.

Results

Of the 355 subjects enrolled at 37 sites worldwide, 334 underwent ablation with the TactiFlex SE catheter. The Kaplan-Meier estimate of 12-month freedom from AF/atrial flutter (AFL)/atrial tachycardia recurrence was 72.9% (95% confidence interval [CI] 95% CI 67.2%-77.8%) and clinical success was 83.6% (95% CI 95% CI 78.1%-87.2%). As-treated analyses compared subjects treated at high power (left atrium time-averaged power setting 40-50 W; n = 222) vs low power (<40 W; n = 97). The Kaplan-Meier estimate of 12-month freedom from AF/AFL/atrial tachycardia recurrence was 76.4% (95% CI 69.3%-82.0%) and clinical success was 83.9% (95% CI 77.5%-88.6%) in the high-power group compared with 66.8% (95% CI 56.1%-75.5%) and 80.7% (95% CI 70.8%- 87.5%), respectively, in the low-power group. The primary safety event rate in all treated subjects was 4.3%; 4.1% in the HP group and 5.2% in the LP group (P = .7671).

Conclusion

TactiFlex SE is safe and effective for treatment of drug-refractory PAF and concomitant AFL and enables more efficient procedures than previous generation catheters.

Hybrid Totally Thoracoscopic Maze and Catheter Ablation for Persistent Atrial Fibrillation: Initial Experience

Atrial fibrillation is now a pandemic in our ageing community. Although James L. Cox devised a surgical procedure with near-universal curative success in 1987, catheter-based interventions have flourished. For persistent atrial fibrillation (AF), however, an isolated endocardial approach has limitations: procedural times are long, carry risk, and the outcomes are not durable. By combining left atrial endocardial and epicardial interventions with staged mapping, we optimise the benefits of both approaches. Our initial series of hybrid ablation for persistent atrial fibrillation reports excellent early outcomes, freedom from complications and excellent success at follow-up.

321 UNMET NEEDS AFTER STROKE

Background

Unmet needs, such as lack of access to rehabilitation, support and information, are experienced by a high proportion of stroke survivors after discharge from acute and rehabilitation services. The UK guidelines on stroke (2016) recommend that all patients should be offered a structured health and social care review at 6 months post-stroke. However, no such clinics exist to date in Ireland. We aimed to explore the extent of unmet needs in the catchment area of a large teaching hospital.

Methods

A random selection of patients 6-months post-stroke were contacted by telephone and unmet needs were assessed using a validated tool, Post-Stroke Checklist. Following analysis of data, the need for a pilot clinic was identified. A separate random selection of patients discharged from acute services 6 months previously were invited to attend a review clinic. Patients were assessed using an adapted version of the Greater Manchester Stroke Assessment Tool. Assessments were conducted jointly by a physiotherapist and a speech and language therapist, and appropriate onward referrals were made.

Results

Telephone clinic: 51 patients completed the checklist. The most prevalent symptoms reported were fatigue (75%), reduced participation in hobbies and activities, decline in cognition (61%) and mobility problems (59%). Review clinic: 21 patients attended. The most prevalent symptoms reported were reduced memory/concentration (71%), low mood (71%), unintentional weight loss/gain (62%), and reduced mobility (43%). Onward referrals were made for in 16/21 (76%) cases; physiotherapy (n=12), occupational therapy (n=7), speech and language therapy (n=7), clinical nutrition (n=5), social work (n=7), psychology (n=5).

Conclusion

Data from this exploratory study supports previous research indicating a high number of stroke survivors with unmet needs. This highlights the importance of establishing post-acute stroke review clinics and pathways in the Irish setting.

Paroxysmal atrial fibrillation ablation with a novel flexible tip radiofrequency catheter incorporating contact force sensing: acute results of the TactiFlex AF IDE trial

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex™ Ablation Catheter, Sensor-Enabled™ (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip.

Purpose

To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF.

Methods

The TactiFlex AF IDE is a prospective, non-randomized, multi-center clinical study which enrolled 355 subjects worldwide. Enrollment in the main study began on June 26, 2020 and completed on June 18, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter.

Results

Subjects were divided into two as treated subgroups: High Standard Power (HSP, n=189), defined as subjects with 100% of left atrial lesions ablated at ≥40 W, and Low Standard Power (LSP, n=119), defined as subjects with at least one left atrial lesion ablated at &lt;40W. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 93.5% (175/186) and 84.5% (98/116) of HSP and LSP subjects, respectively (p=0.0104). Significant decreases in the HSP versus LSP procedures were also seen in total procedure time (112.0 min [89.0, 139.5] and 149.0 [115.0, 182.0], respectively [p&lt;0.001]), total RF time for PV ablation (14.0 min [11.0, 19.0] and 29.0 [19.0, 41.0], respectively [p&lt;0.0001]), total fluoroscopy time (4.0 min [0.0, 11.0] and 8.0 [3.0, 17.0], respectively [p&lt;0.0001]) and irrigation fluid volume (378.0 mL [310.0, 466.0] and 636.0 [476.0, 829.0], respectively [p&lt;0.0001]) (values given as Median [Q1, Q3]), see Figure 1. Both HSP and LSP subjects had a low rate of repeat procedures (1.6% [3/182] and 4.3% [5/115], respectively [p=0.2684]) and primary safety endpoint events (4.8% [9/189] and 4.2% [5/119], respectively [p=0.8182]) through 90 days post-index procedure.

Conclusion

The acute data on the TactiFlex SE catheter demonstrates safe and effective treatment of PAF using either a HSP or LSP ablation strategy. Ablation procedures performed using a HSP strategy were shorter and required less irrigation fluid and fluoroscopy. It is anticipated these results will be reflected in the 12-month safety and effectiveness primary endpoints.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Abbott

Acute results of a novel flexible tip radiofrequency catheter incorporating contact force sensing

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex Ablation Catheter, Sensor-Enabled (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip. This is the first report of results from the TactiFlex IDE clinical study.

Purpose

To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF.

Methods

The TactiFlex IDE (NCT04356040) is a prospective, non-randomized, multi-center clinical study which enrolled 305 subjects worldwide in the main study. Enrollment in the main study began on June 26, 2020 and completed on June 8, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter.

Results

Acute procedural success was achieved in 98.6% (274/278) of the main study cohort who underwent an ablation procedure using the TactiFlex SE. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 89.6% (249/278) of subjects. This was a significant improvement versus the TactiSense IDE trial (TactiCath Ablation Catheter, Sensor-Enabled). Significant decreases were also seen in total procedure time (123 min [101.0, 163.5]), total PV ablation time (55.5 min [35.0, 81.0]), total fluoroscopy time (6.0 min [0.0, 13.0]) and irrigation fluid volume (450.0 mL [346.0, 636.0]) (values given as Median [Q1, Q3]), see FIGURE. All subjects have completed at least 90 days of follow-up. Only 2.6% (7/271) of subjects required a repeat procedure during the 90-day blanking period. The primary safety and effectiveness endpoints will be evaluated at 12-months. At 90 days, 4.3% (12/281) subjects had experienced a primary safety endpoint event.

Conclusions

The acute data from the TactiFlex IDE clinical study demonstrate safety and effectiveness of the TactiFlex SE catheter in the treatment of PAF. Ablation procedures performed using the next-generation TactiFlex SE catheter were shorter and had improved acute clinical effectiveness outcomes versus the TactiSense IDE. It is anticipated these results will also be reflected in the 12-month safety and effectiveness endpoints.

Physical activity and screen time among youth with autism: A longitudinal analysis from 9 to 18 years

LAY ABSTRACT

To date, studies using cross-sectional methodologies make up a majority of the literature surrounding children with autism spectrum disorders and participation in physical activity and screen time. Longitudinal studies are needed to examine how physical activity and screen time behaviors co-develop for children with and without an autism spectrum disorder. To address this research gap, this study compared how physical activity and screen time levels changed over time (from 9 to 18 years of age) between youth with autism spectrum disorder and youth with neurotypical development. Data on the levels of moderate-to-vigorous physical activity, light physical activity, television-, and video game-based screen time, collected as a part of the "Growing up in Ireland" study, were compared between youth with autism spectrum disorder and a propensity-matched sample of youth with neurotypical development (n = 88 per group; 176 in total). Robust regression analyses indicated that children with autism spectrum disorder became less active over time compared to children with neurotypical development and that video game screen time also differed significantly between the groups when children were 9 years old. These findings elucidate important disparities present between these groups of children during pivotal developmental times.

Quality of life measured in first-line therapy during the Cryo-FIRST study: a comparison between cryoballoon catheter ablation versus antiarrhythmic drug therapy

Background

By consensus statements, catheter ablation is a recommended treatment for patients with symptomatic drug-refractory paroxysmal atrial fibrillation (AF), as patients try to alleviate the burdensome AF symptoms that reduce the Quality of Life (QoL). Yet, first-line treatment of symptomatic patients via catheter ablation prior to initiation of antiarrhythmic drugs (AADs) is only a reasonable alternative (Class IIa). Clearly, more clinical data is necessary that compares catheter ablation to AAD therapy in treatment naïve patients.

Purpose

The Cryo-FIRST trial was designed to compare AAD treatment against pulmonary vein isolation (PVI) while using a cryoballoon catheter (Arctic Front Advance; Medtronic, Inc.). This current data analysis examines the QoL endpoints when comparing AADs to cryoballoon ablation in patients with symptomatic treatment naïve paroxysmal AF.

Methods

This randomized multicenter trial enrolled 220 patients from 18 sites in 9 countries (Europe, Australia, and Latin America) in a prospective open-blinded endpoint study design. Patients had not been administered a class I or III AAD for longer than 48 hours for inclusion into the study. Subjects were randomized (1:1) into a cohort that was administered AAD therapy or a cohort that received PVI via cryoablation. The prespecified QoL endpoint at 12 months was measured using the Atrial Fibrillation Effect on Quality of Life (AFEQT) scores, and QoL recordings were taken at baseline, 1, 3, 6, 9, and 12 months following the index treatment.

Results

Of the 218 patients randomized (age 52±13 years, 68% male) 86% completed the 12-month follow-up. Crossovers occurred in 9% of subjects (N=20), including: 1 subject in the cryoablation arm and 19 subjects in the AAD arm. At 12 months, 86.5% of the patients in the cryoablation arm and 70.4% of the patients in the AAD arm where without symptoms (EHRA score 1). The mean AFEQT summary score was more favorable in the catheter ablation group compared to the drug therapy group at 12 months (88.9 vs. 78.1 points, respectively). The adjusted difference was 9.9 points (95% CI: 5.5–14.2; P&lt;0.0001).

Conclusions

Cryoballoon ablation resulted in a significant improvement in QoL at 12 months compared to AAD therapy in treatment naïve patients with first-line symptomatic paroxysmal AF.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Medtronic International Trading Sàrl

Junctional ectopic tachycardia (JET)

Junctional ectopic tachycardia (JET) is a tachyarrhythmia arising from the atrioventricular node and His bundle area. Enhanced normal automaticity has been postulated as the mechanism of JET in the majority of patients. It is more common in children and can be seen as congenital or in postoperative settings. It is often a narrow complex tachycardia but can present as a wide complex tachycardia as a result of aberrant conduction. Its differentiation from other arrhythmias especially atrioventricular nodal reentrant tachycardia (AVNRT) can be challenging. Medical treatment of JET is difficult, and catheter ablation remains the mainstay of treatment in refractory cases with a high risk of atrioventricular block and recurrence.

Long-term longevity and clinical outcomes of Linox S/SD implantable cardioverter-defibrillator leads: a single-center experience

PURPOSE

Since the introduction of the Biotronik Linox S/SD leads in 2006, there have been multiple reports of premature lead failure. The purpose of this study was to investigate the longevity of the Linox S/SD leads and to identify the possible predictors of lead failure in a single tertiary implant center.

METHODS

We retrospectively reviewed patients who underwent implantation of Linox S/SD leads or Sorin Vigila 1CR/2CR leads (the same Linox S/SD leads marketed by Sorin) at our center. The cumulative lead survival was estimated using the Kaplan-Meier curve, and variables associated with lead failure were assessed by Cox proportional hazard model.

RESULTS

A total of 187 patients (154 (82%) male) underwent Linox S/SD or Vigila 1CR/2CR implantation between 2007 and 2013. During follow-up with a median time of 75 months, nine lead failures were identified (4.8%). The mean and median times from lead implantation to lead failure were 70.7 ± 21 months and 64 (45-111) months, respectively. The cumulative survival probability for the Linox S/SD at 5 years was 97.1% and at 12 years was 90.3%. Non-physiological high-rate sensing was the most common type of lead failure in patients. In two-thirds of these patients, this led to inappropriate shock. We did not find any significant relationships between patients' clinical and procedural characteristics and lead failure.

CONCLUSIONS

At our center, the 5-year lead survival of the Linox S/SD has been better than reports from other centers. The majority of lead failures presented as non-physiological high-rate sensing with subsequent inappropriate therapy.

Pacemaker-mediated arrhythmias

Pacemakers can be directly involved in initiating or sustaining different forms of arrhythmia. These can cause symptoms such as dyspnea, palpitations, and decompensated heart failure. Early detection of these arrhythmias and optimal pacemaker programming is pivotal. The aim of this review article is to summarize the different types of pacemaker-mediated arrhythmias, their predisposing factors, and mechanisms of prevention or termination.

Loss of cardiac resynchronization therapy in a patient with a biventricular implantable cardioverter-defibrillator

Here, we discuss the case of a man with a history of ischemic cardiomyopathy and cardiac resynchronization therapy defibrillator implantation, who presented to emergency department with decompensated heart failure due to the loss of resynchronization therapy. The reason for the malfunction was left ventricle upper rate interval lock-in due to inappropriate programming of the device.

THYROTOXICOSIS SECONDARY TO ALEMTUZUMAB TREATMENT FOR MULTIPLE SCLEROSIS PRESENTING AS PULMONARY HYPERTENSION

Alemtuzumab has been approved for use in the treatment of relapsing multiple sclerosis. Despite its proven clinical efficacy acquired autoimmune disease remains a significant risk. In particular thyroid disease is common and robust surveillance mechanisms are required to identify disease at an early stage. We present the case of a 31-year-old female patient who presented with signs consistent with pulmonary hypertension as the presenting feature of thyrotoxicosis. 12-months after the first alemtuzumab treatment course the patient presented to clinic with a 2-week history of exertional dyspnoea, palpitations and headaches. On examination, she had a new pansystolic murmur loudest in the pulmonary area and bilateral pitting oedema to the knees. An echocardiogram demonstrated elevated right ventricular pressure (40 mm Hg) and tricuspid regurgitation consistent with pulmonary hypertension. A CT pulmonary angiogram did not demonstrate evidence of a pulmonary embolus. Thyroid function tests revealed profound thyrotoxicosis (free T4 37.3 pmol/l and TSH <0.02 mU/l), which was thought to be the likely cause. Carbimazole was started but discontinued due to a rash with euthyroidism eventually achieved with radio-iodine. Her symptoms have subsequently resolved. This case highlights the need for neurologists using Alemtuzumab to be vigilant of the varied and sometimes acute presentations of thyroid dysfunction; and the growing repertoire of induced autoimmunity.

Ambulatory tuberculosis treatment in post-Semashko health care systems needs supportive financing mechanisms

The tuberculosis (TB) control strategy in the Republic of Karakalpakstan, Uzbekistan, is being changed to decentralised out-patient care for most TB patients by the Government of Uzbekistan, in collaboration with the international medical humanitarian organisation Médecins Sans Frontières. Ambulatory treatment of both drug-susceptible and drug-resistant TB from the first day of treatment has been recommended since 2011. Out-patient treatment of TB from the beginning of treatment was previously prohibited. However, the current Uzbek health financing system, which evolved from the Soviet Semashko model, offers incentives that work against the adoption of ambulatory TB treatment. Based on the 'Comprehensive TB Care for All' programme implemented in Karakalpakstan, we describe how existing policies for the allocation of health funds complicate the scale-up of ambulatory-based management of TB.

Vagal nerve stimulation in children under 12 years old with medically intractable epilepsy

OBJECTIVE

This study aims to assess the efficacy and safety of vagal nerve stimulation (VNS) in children less than 12 years old operated on at the University Hospital Wales.

METHOD

Retrospective review of patients undergoing VNS insertion, over a 3-year period, was undertaken. All children had a minimum follow-up period of 2 years. Sixteen patients were identified via the paediatric epilepsy surgery database. A case note review and telephone evaluation was conducted. Seizure frequency using the McHugh classification was the primary outcome measure, with anti-epileptic drug (AED) use as a secondary outcome measure.

RESULTS

There were 10 males and 6 females. The mean time with epilepsy prior to surgery was 5.7 years and the mean age at the time of surgery was 7.6 years. Overall, nine (56 %) children experienced a reduction in their seizure frequency of 50 % or more. Of these, four (25 %) had a reduction of more than 80 %. Seven children (44 %) had no reduction in their seizure frequency, although two of these patients reported benefit regarding seizure control and post-ictal recovery. The VNS system was removed in two patients due to infection and no benefit, respectively. Half of the cohort (50 %) reduced the number of anti-epileptic drugs post-surgery, and there was an overall mean reduction of AED of 0.5.

CONCLUSION

This study suggests that VNS is a safe and effective adjuvant therapy in children under 12 years old, with over half reporting significant benefit. Further studies are needed to enable preoperative selection of patients in order to maximise the potential benefit.

Public health advocacy for the Berlin Declaration on tuberculosis in the former Soviet Union: The view of Médecins Sans Frontières

To assist international efforts to address major gaps in the availability and accessibility of quality diagnosis and treatment for multi-drug resistant tuberculosis, Médecins Sans Frontières has adapted an approach combining three sets of interlinked strategies: direct provision of medical care, operational research, and public health advocacy. The activities undertaken are reviewed each in turn, with stress on the ways that they impact upon and consolidate each other. In spite of new opportunities, including technologies which significantly improve diagnosis and new, more patient-centred approaches, a much broader international mobilization is needed in order to confront MDR-TB. It is also questionable as to whether existing technologies are successful enough to provide a solid basis for expanded national programs.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Composition and energy harvesting capacity of the gut microbiota: relationship to diet, obesity and time in mouse models

BACKGROUND AND AIMS

Increased efficiency of energy harvest, due to alterations in the gut microbiota (increased Firmicutes and decreased Bacteroidetes), has been implicated in obesity in mice and humans. However, a causal relationship is unproven and contributory variables include diet, genetics and age. Therefore, we explored the effect of a high-fat (HF) diet and genetically determined obesity (ob/ob) for changes in microbiota and energy harvesting capacity over time.

METHODS

Seven-week-old male ob/ob mice were fed a low-fat diet and wild-type mice were fed either a low-fat diet or a HF-diet for 8 weeks (n=8/group). They were assessed at 7, 11 and 15 weeks of age for: fat and lean body mass (by NMR); faecal and caecal short-chain fatty acids (SCFA, by gas chromatography); faecal energy content (by bomb calorimetry) and microbial composition (by metagenomic pyrosequencing).

RESULTS

A progressive increase in Firmicutes was confirmed in both HF-fed and ob/ob mice reaching statistical significance in the former, but this phylum was unchanged over time in the lean controls. Reductions in Bacteroidetes were also found in ob/ob mice. However, changes in the microbiota were dissociated from markers of energy harvest. Thus, although the faecal energy in the ob/ob mice was significantly decreased at 7 weeks, and caecal SCFA increased, these did not persist and faecal acetate diminished over time in both ob/ob and HF-fed mice, but not in lean controls. Furthermore, the proportion of the major phyla did not correlate with energy harvest markers.

CONCLUSION

The relationship between the microbial composition and energy harvesting capacity is more complex than previously considered. While compositional changes in the faecal microbiota were confirmed, this was primarily a feature of high-fat feeding rather than genetically induced obesity. In addition, changes in the proportions of the major phyla were unrelated to markers of energy harvest which changed over time. The possibility of microbial adaptation to diet and time should be considered in future studies.

Thermolability of mutant MMACHC protein in the vitamin B12-responsive cblC disorder

Methylmalonic aciduria and homocystinuria, cblC type, is the most common inborn error of cellular vitamin B12 metabolism. We previously showed that the protein carrying the mutation responsible for late-onset cblC (MMACHC-R161Q), treatable with high dose OHCbl, is able to bind OHCbl with wild-type affinity, leaving undetermined the disease mechanism involved [Froese et al., Mechanism of responsiveness, Mol. Genet. Metab. (2009).]. To assess whether the mutation renders the protein unstable, we investigated the thermostability of the wild-type and mutant MMACHC proteins, either unbound or bound to different cobalamins (Cbl), using differential scanning fluorimetry. We found that MMACHC-wt and MMACHC-R161Q are both very thermolabile proteins in their apo forms, with melting temperatures (T(m)) of 39.3+/-1.0 and 37.1+/-0.7 degrees C, respectively; a difference confirmed by unfolding of MMACHC-R161Q but not MMACHC-wt by isothermal denaturation at 35 degrees C over 120 min. However, with the addition of OHCbl, MMACHC-wt becomes significantly stabilized (Delta T(m max)=8 degrees C, half-maximal effective ligand concentration, AC(50)=3 microM). We surveyed the effect of different cobalamins on the stabilization of the wild-type protein and found that AdoCbl was the most stabilizing, exerting a maximum increase in T(m) of approximately 16 degrees C, followed by MeCbl at approximately 13 degrees C, each evaluated at 50 microM cofactor. The other cobalamins stabilized in the order (CN)(2)Cbi>OHCbl>CNCbl. Interestingly, the AC(50)'s for AdoCbl, MeCbl, (CN)(2)Cbi and OHCbl were similar and ranged from 1-3 microM, which compares well with the K(d) of 6 microM for OHCbl [Froese et al., Mechanism of responsiveness, Mol. Genet. Metab. (2009).]. Unlike MMACHC-wt, the mutant protein MMACHC-R161Q is only moderately stabilized by OHCbl (Delta T(m max)=4 degrees C). The dose-response curve also shows a lower effectivity of OHCbl with respect to stabilization, with an AC(50) of 7 microM. MMACHC-R161Q showed the same order of stabilization as MMACHC-wt, but each cobalamin stabilized this mutant protein less than its wild-type counterpart. Additionally, MMACHC-R161Q had a higher AC(50) for each cobalamin form compared to MMACHC-wt. Finally, we show that MMACHC-R161Q is able to support the base-off transition for AdoCbl and CNCbl, indicating this mutant is not blocked in that respect. Taken together, our results suggest that protein stability, as well as propensity for ligand-induced stabilization, contributes to the disease mechanism in late-onset cblC disorder. Our results underscore the importance of cofactor stabilization of MMACHC and suggest that even small increases in the concentration of cobalamin complexed with MMACHC may have therapeutic benefit in children with the late-onset, vitamin responsive cblC disease.

138. GENOME-WIDE LINKAGE SCAN FOR FAMILIAL DIZYGOTIC TWINNING

The tendency to conceive dizygotic (DZ) twins is a complex trait influenced by genetic and environmental factors. To search for new candidate loci for twinning we have conducted a genome-wide linkage scan in 525 families using microsatellite and single nucleotide polymorphism (SNP) marker panels. Non-parametric linkage analyses including 523 families containing a total of 1115 mothers of DZ twins (MODZT) from Australia and New Zealand (ANZ) and The Netherlands (NL) produced four linkage peaks above the threshold for suggestive linkage, including a highly suggestive peak at the extreme telomeric end of chromosome 6 with an exponential (exp)LOD score of 2.813 (P = 0.0002). Since the DZ twinning rate increases steeply with maternal age independent of genetic effects, we also investigated linkage including only families where at least one MODZT gave birth to her first set of twins before the age of 30. These analyses produced a maximum expLOD score of 2.718 (p = 0.0002), largely due to linkage signal from the ANZ cohort, however, ordered subset analyses indicated this result is most likely a chance finding in the combined dataset. Linkage analyses were also performed for two large DZ twinning families from the USA, one of which produced a peak on chromosome 2 in the region of two potential candidate genes. Sequencing of FSHR and FIGLA, along with INHBB in MODZTs from two large NL families with family-specific linkage peaks directly over this gene, revealed a potentially functional variant in the 5’ untranslated region of FSHR that segregated with the DZ twinning phenotype in the UT family. Work is continuing screening candidate genes. Our data provide further evidence for complex inheritance of familial DZ twinning.

Mechanism of vitamin B12-responsiveness in cblC methylmalonic aciduria with homocystinuria

Patients with the cblC vitamin B(12) (cobalamin, cbl) disorder are defective in the intracellular synthesis of adenosylcobalamin and methylcobalamin and have combined homocystinuria and methylmalonic aciduria. While other vitamin B(12) disorders are treatable with high dose cyanocobalamin (CNCbl) or hydroxocobalamin (OHCbl), cblC patients respond well to OHCbl but not to CNCbl. Patient mutations were introduced into recombinant MMACHC (cblC) protein and the binding of CNCbl and OHCbl was examined. Three mutations were analyzed: G147D, associated with early onset, vitamin B(12) unresponsive disease; R161Q, associated with late onset disease that is highly responsive to OHCbl; and H122A, selected to test the hypothesis that H122 is central to a proposed vitamin B(12) binding motif on MMACHC. We report here that wild-type MMACHC binds both OHCbl and CNCbl with similar, tight affinity (K(d)=5.7 microM). We also report that MMACHC binds CNCbl in the base-off form, with the dimethylbenzimidazole (DMB) base of cobalamin displaced from coordination with the cobalt. In this form, wild-type MMACHC is able to reductively decyanate CNCbl to cob(II)alamin requiring only the presence of NADPH and FAD. We demonstrate that MMACHC with the G147D mutation is unable to bind either CNCbl or OHCbl, providing a straight forward explanation for the absence of response to either vitamin form. However, we show that MMACHC containing the R161Q mutation binds OHCbl with wild-type affinity, but is disturbed in binding CNCbl and has impaired decyanation. Finally, we show that H122A has reduced binding, but like R161Q, it binds OHCbl more tightly than CNCbl, suggesting that this histidine is not absolutely required for binding. These studies suggest that the ability of mutant MMACHC to respond to vitamin therapy depends on its ability to bind the vitamin with significant affinity, and for CNCbl, also on its ability to bind in the base-off form to facilitate reductive decyanation. These studies emphasize the continued use of OHCbl with cblC patients for maximum therapeutic effect.

Aspirin esterase activity - Evidence for skewed distribution in healthy volunteers

BACKGROUND

Aspirin, with its analgesic, anti-inflammatory, antipyretic, and anti-platelet actions, is one of the most frequently used drugs. Although its use as prophylaxis against thromboembolism is well established, an optimal dose, conferring maximal anti-platelet action without increased risk of bleeding, remains elusive.

METHOD

We assessed the possible pharmacokinetic contribution to this problem in 107 healthy, non-medicated volunteers. Serum aspirin esterase activity was evaluated at 37 degrees C with 1 mM aspirin as substrate. On the basis of the report that most of aspirin esterase activity is accounted for by pseudocholinesterase, we additionally quantified the activity of this enzyme, with and without dibucaine as an inhibitor, using Ellman's reaction, in 41 of our volunteers.

RESULTS

Aspirin esterase activities in all of our volunteers (33.90 nmol/ml/min to 222.65 nmol/ml/min, median 103.45 nmol/ml/min) showed a continuous and skewed distribution with eight outliers. In the 41 subjects so studied, aspirin esterase activities correlated positively with both pseudocholinesterase activities (Spearman's rho=0.593, p<0.001) and dibucaine numbers (Spearman's rho=0.422, p<0.01).

CONCLUSIONS

Our results support previous observations that the rate of aspirin hydrolysis is not determined by aspirin esterase alone and that other factors are probably involved. Additionally, the skewed distribution of aspirin esterase activities makes a case for its possible contribution to the phenomenon of aspirin resistance.

Pseudocholinesterase polymorphism in an Irish population

BACKGROUND

Pseudocholinesterase polymorphism, as an example of pharmacogenetics with important clinical implications, has been widely studied and documented. However, data on a sample Irish population is lacking. We sought to provide this.

METHOD

In an assay involving Ellman's reaction, pseudocholinesterase activity, alone and with dibucaine or fluoride as an inhibitor, was quantified using propionylthiocholine iodide as substrate.

RESULTS

Pseudocholinesterase activities of 1.13-12.71 U/ml (mean +/- SD 6.74 +/- 2.04 U/ml) showed a normal distribution among our 116 healthy, non-medicated volunteers, aged 11-80 years (30.7 +/- 10.5 years) and weighing 46-114.6 kg (66.8 +/- 11.4 kg). However, dibucaine numbers from an inhibition study yielded a trimodal pattern consistent with the hypothesis of two allelic genes. Using an established nomenclature, 92 (79.3%) of our volunteers were homozygous for the usual form of the enzyme (E1uE1u). Of the 13 genotyped as E1uE1a, it is possible that 3 were misclassified and are probably E1kE1a. Only one volunteer was homozygous for the atypical form of the enzyme, with activity of 1.13 U/ml and dibucaine and fluoride number of 18.2 and 82.8, respectively.

CONCLUSION

The continuous variation in pseudocholinesterase activity and the trimodal pattern of dibucaine numbers are both in accord with observations in other population groups. Although dibucaine number yields a trimodal pattern, its use could lead to misclassification of some E1kE1a as E1uE1a.

Cytocompatibility of novel tin oxide thin films

The capacity of tin oxide films to support cell growth was investigated. Three substrates were used for the test: glass coverslips, glass coverslips spin coated with tin oxide and commercially available 316 stainless steel. The wettabilities and surface roughness of the three surfaces were measured before seeding 3T3 fibroblasts onto the samples. The behaviour of the cells grown on the tin oxide was compared to the uncoated glass and the steel and results showed that the cell growth on tin oxide compared favourably with the other substrates. The surface wettability appeared to have the strongest effect on cell adhesion to tin oxide.

Tube feeding controversial patients: what do dietitians think?

The use of tube feeding in some patients can be controversial, however, few studies have investigated dietitians' opinions on this subject. A cross-sectional survey of 345 members the Irish Nutrition and Dietetic Institute was conducted using a self-administered, anonymous, postal questionnaire. A 44% response rate was achieved. Mean number of years qualified was 9.3 (8.4). Eighty-one per cent of responders were involved in initiating tube feeding in stroke patients, and 8.5% in discontinuing tube feeding in a patient in a persistent vegetative state (PVS). Nine per cent felt that their input had no influence on the care plan of the patient with dementia and 67% felt that the information given to families (or other decision makers) concerning tube feeding was inadequate. The majority of respondents favoured tube feeding fictitious stroke and cancer patients, but less than half favoured tube feeding a fictitious patient in a PVS or a patient with dementia. When given similar scenarios involving themselves, fewer dietitians wanted to be tube fed.

Risk as social process: the end of 'the age of appealing to the facts'?

This paper utilises the notion of the risk society to argue that the ways in which technical practices, knowledge and rationality have become structured into governance are counter-productive and now instrumental to the proliferation of risk and destabilisation of governance. This problem is epitomised by how decisions have evolved to become a matter determined by 'facts' rather than by a determination of the community impact of outcomes and further compounded by the institutionally embedded blindness to wider social concerns that this entails. It is argued that what are required are processes integrating 'factual' technical and 'value-laden' societal concerns and avenues for this and their ramifications are elaborated and explored. Central to such developments will be a democratisation of technical practices and the institutions in which they are embedded. The broader political implications of these developments are examined and found to involve a radical extension of democracy involving an extensive reshaping of the topography of governance.