The effects of local forearm heating and cooling on motor unit properties during submaximal contractions.

NEW FINDINGS: What is the central question of this study? How do temperature manipulations affect motor unit (MU) properties during submaximal contractions to the same relative percentage of maximal force? What is the main finding and its importance? MU recruitment patterns are affected by temperature manipulations at the forearm. However, the relationship between MU potential amplitude and recruitment threshold indicates no change to the order or recruitment. Additionally, the MU potential amplitude and firing rate relationship was affected by temperature, suggesting that smaller MUs are more affected by temperature changes than larger MUs. ABSTRACT: Temperature impacts muscle contractile properties, such that experiments with workloads based on thermoneutral values will produce different relative intensities if maximal force changes due to muscle temperature. We investigated how temperature affected motor unit (MU) properties with contractions performed at the same normalized percentage of maximal force. Twenty participants (10 females) completed evoked, maximal, and trapezoidal voluntary contractions during thermoneutral-, hot-, and cold-temperature conditions. Forearm temperature was established using 25 min of neutral (∼32°C), hot (∼44°C) or cold (∼13°C) water circulated through a tube-lined sleeve. Flexor carpi radialis MU properties were assessed with contractions at 30% and 60% MVC relative to each temperature using surface electromyography decomposition. Changes to contractile properties and electromechanical delay from the evoked twitch suggest that muscle contractility was changed from the thermal manipulations (effect size (d) ≥ 0.42, P < 0.05). Maximal force was not different between neutral and hot conditions (d = 0.16, P > 0.05) but decreased in the cold (d ≥ 0.34, P < 0.05). For both contraction intensities, MU potential (MUP) amplitude was larger and duration was longer in the cold compared to neutral and hot conditions (d ≥ 1.24, P < 0.05). Cumulative probability density for the number of MUs recruited revealed differences in MU recruitment patterns among temperature conditions. The relationship between MU recruitment threshold and firing rate or MUP amplitude was not different among temperature conditions (P > 0.05); however, the relationship between MUP amplitude and firing rate was (P < 0.05). Local temperature manipulations appear to affect MU recruitment patterns, which may act as compensatory mechanisms to the changes in muscle viscosity and contractile properties due to local temperature changes.

Dynamic Wrist Flexion and Extension Fatigue Induced via Submaximal Contractions Similarly Impairs Hand Tracking Accuracy in Young Adult Males and Females.

We evaluated the effects of muscle fatigue on hand-tracking performance in young adults. Differences were quantified between wrist flexion and extension fatigability, and between males and females. Participants were evaluated on their ability to trace a pattern using a 3-degrees-of-freedom robotic manipulandum before (baseline) and after (0, 1, 2, 4, 6, 8, and 10 mins) a submaximal-intensity fatigue protocol performed to exhaustion that isolated the wrist flexors or extensors on separate days. Tracking tasks were performed at all time points, while maximal voluntary contractions (MVCs) were performed at baseline, and 2, 6-, and 10-mins post-task termination. We evaluated movement smoothness (jerk ratio, JR), shape reproduction (figural error, FE), and target tracking accuracy (tracking error, TE). MVC force was significantly lower in females (p < 0.05), lower than baseline for all timepoints after task termination (p < 0.05), with no muscle group-dependent differences. JR did not return to baseline until 10-mins post-task termination (most affected), while FE returned at 4-mins post-task termination, and TE at 1-min post-task termination. Males tracked the target with significantly lower JR (p < 0.05), less TE (p < 0.05), and less FE (p < 0.05) than females. No muscle group-dependent changes in hand-tracking performance were observed. Based on this work, hand tracking accuracy is similarly impaired following repetitive submaximal dynamic wrist flexion or extension. The differences between male and female fatigability was independent of the changes in our tracking metrics.

A method for editing motor unit potential trains obtained by decomposition of surface electromyographic signals.

Rather than discarding motor unit potential trains (MUPTs) because they do not meet 100% validity criteria, we describe and evaluate a novel editing routine that preserves valid discharge times, based on decreasing shape variability (variance ratio, VR) within a MUPT. The error filtered estimation (EFE) algorithm is then applied to the remaining 'high confidence' discharge times to estimate inter-discharge interval (IDI) statistics. Decomposed surface EMG data from the flexor carpi radialis recorded from 20 participants during 60% MVC wrist flexion was used. There were two levels of denoising criteria (relaxed and strict) criteria for removing MUPs to decrease the VR and increase the signal-to-noise ratio (SNR) of a MUPT. In total, VR decreased 24.88% and SNR increased 6.0% (p's < 0.05). The MUP template peak-to-peak (P-P) amplitude and P-P duration were dependent on the level of denoising (p's < 0.05). The standard error of the estimate (SEE) of the mean IDI before and after editing using the relaxed criteria (3.2% versus 3.69%), was very similar (p > 0.05). The same was true for the SEE between denoising criteria, which increased only to 5.14% for the strict criteria (p > 0.05). Editing the MUPTs resulted in a significant decrease in MUP shape variability and in the measures extracted from the MUP templates, with trivial differences between the SEE of the mean IDI between the edited and unedited MUPTs.

The success of the Uttarakhand Cluster: a case study of organisational change towards disability inclusive development.

BACKGROUND: Persons with disability are often marginalised and excluded from international development efforts. This case study reviews the success of Uttarakhand Cluster of development NGOs in changing organisational behaviour towards being disability inclusive in their development (DID) activities. METHODS: A triangulation of qualitative research methods was used, including key informant interviews, focus group discussions and review of textual data. RESULTS: The results synthesise data into Kotter's framework for organisational change, explaining the different stages of change experienced by the Cluster as it moved towards DID. Development of a disability mission, sharing of capacity and resources, and presence of disability champions were key in the organisations' transition towards DID. CONCLUSION: This case study demonstrates that the Cluster, a low - cost network, was able to drive organisational change and promote DID.

Percutaneous complete repair of failed mitral valve prosthesis: simultaneous closure of mitral paravalvular leaks and transcatheter mitral valve implantation - single-centre experience.

AIMS: Structural deterioration and paravalvular leak (PVL) are complications associated with surgically implanted prosthetic valves, historically requiring reoperation. We present our experience of complete transcatheter repair of a degenerated mitral bioprosthesis. METHODS AND RESULTS: From March 2012 to October 2012, we reviewed consecutive, high-risk surgical patients (n=5) who underwent transcatheter repair of a failed mitral bioprosthesis with severe paravalvular regurgitation (PVR). Manufacturer valve sizes ranged from 27 to 33 mm, regurgitation (n=1), stenosis (n=1), or both (n=3). Percutaneous transapical and transseptal access were achieved with PVL closure performed transapically. An arteriovenous rail was created for transseptal delivery of a Melody valve. All patients had successful PVL closure with no residual PVR. Valve-in-valve (ViV) implantation was successful in four patients. Overall, mean transvalvular mitral gradient was 11.2 mmHg pre-procedure which improved to 5 mmHg post-procedure. Improvement of NYHA Class ≥2 was achieved in all patients (19±3 months). One patient had controlled Melody valve embolisation which required emergent surgical replacement. Inner valve diameter was 26 mm, too large for Melody valve implantation. CONCLUSIONS: Complete transcatheter repair of a degenerated mitral bioprosthesis with PVR can be performed in the high-risk patient. Accurate measurement is necessary prior to intervention, with concern for embolisation among the larger valve sizes (>31 mm).

Networking between community health programs: a team-work approach to improving health service provision.

BACKGROUND: Networking between non-government organisations in the health sector is recognised as an effective method of improving service delivery. The Uttarakhand Cluster was established in 2008 as a collaboration of community health programs in rural north India with the aim of building capacity, increasing visibility and improving linkages with the government. This qualitative research, conducted between 2011-2012, examined the factors contributing to formation and sustainability of this clustering approach. METHODS: Annual focus group discussions, indicator surveys and participant observation were used to document and observe the factors involved in the formation and sustainability of an NGO network in North India. RESULTS: The analysis demonstrated that relationships were central to the formation and sustainability of the cluster. The elements of small group relationships: forming, storming, norming and performing emerged as a helpful way to describe the phases which have contributed to the functioning of this network with common values, strong leadership, resource sharing and visible progress encouraging the ongoing commitment of programs to the network goals. CONCLUSIONS: In conclusion, this case study demonstrates an example of a successful and effective network of community health programs. The development of relationships was seen to be to be an important part of promoting effective resource sharing, training opportunities, government networking and resource mobilisation and will be important for other health networks to consider.

Self-expanding prostheses for transcatheter aortic valve replacement.

Transcatheter aortic valve replacement (TAVR) has emerged as an alternative to surgical aortic valve replacement in patients who are considered high surgical risk or inoperable due to advanced age and comorbidities. Randomized trial and registry data have demonstrated the safety and efficacy of TAVR in such patients. Currently available transcatheter heart valves (THVs) employ either balloon-expandable or self-expanding designs, and several new designs have shown promising early results. Differences in valve design may offer specific advantages for accurate deployment and minimizing complications. This article reviews several designs of self-expanding THVs that are currently available or have undergone successful implantation in humans. Additional studies are required to compare the relative performance of these devices.

CT angiography-fluoroscopy fusion imaging for percutaneous transapical access.

OBJECTIVES: The aim of this proof-of-principle study is to validate the accuracy of fusion imaging for percutaneous transapical access (TA). BACKGROUND: Structural heart disease interventions, including TA, are commonly obtained under fluoroscopic guidance, which lacks important spatial information. Computed tomographic angiography (CTA)-fluoroscopy fusion imaging can provide the 3-dimensional information necessary for improved accuracy in planning and guidance of these interventions. METHODS: Twenty consecutive patients scheduled for percutaneous left ventricular puncture and device closure using CTA-fluoroscopy fusion guidance were prospectively recruited. The HeartNavigator software (Philips Healthcare, Best, the Netherlands) was used to landmark the left ventricular epicardium for TA (planned puncture site [PPS]). The PPS landmark was compared with the position of the TA closure device on post-procedure CTA (actual puncture site). The distance between the PPS and actual puncture site was calculated from 2 fixed reference points (left main ostium and mitral prosthesis center) in 3 planes (x, y, and z). The distance from the left anterior descending artery at the same z-plane was also assessed. TA-related complications associated with fusion imaging were recorded. RESULTS: The median (interquartile range [IQR]) TA distance difference between the PPS and actual puncture site from the referenced left main ostium and mitral prosthesis center was 5.00 mm (IQR: 1.98 to 12.64 mm) and 3.27 mm (IQR: 1.88 to 11.24 mm) in the x-plane, 4.48 mm (IQR: 1.98 to 13.08 mm) and 4.00 mm (IQR: 1.62 to 11.86 mm) in the y-plane, and 5.57 mm (IQR: 3.89 to 13.62 mm) and 4.96 mm (IQR: 1.92 to 11.76 mm) in the z-plane. The mean TA distance to the left anterior descending artery was 15.5 ± 7.8 mm and 22.7 ± 13.7 mm in the x- and y-planes. No TA-related complications were identified, including evidence of coronary artery laceration. CONCLUSIONS: With the use of CTA-fluoroscopy fusion imaging to guide TA, the actual puncture site can be approximated near the PPS. Moreover, fusion imaging can help maintain an adequate access distance from the left anterior descending artery, thereby, potentially reducing TA-related complications.

Percutaneous paravalvular leak closure.

Percutaneous paravalvular leak closure is increasingly being performed as an alternative to reoperation in patients with symptomatic prosthetic paravalvular regurgitation. This article reviews the pathogenesis of paravalvular leaks and percutaneous techniques for closure. Newer multimodality imaging techniques, including 3-dimensional (3D) transesophageal echocardiography and 3D/4D computed tomographic angiography, allow improved preprocedural planning and intraprocedural guidance. Specific techniques can be used for challenging patient anatomy and larger paravalvular leaks. Outcomes from experienced centers show acceptable rates of technical and clinical success, with lower procedural morbidity than reoperation.

Effect of race and ethnicity on outcomes with drug-eluting and bare metal stents: results in 423 965 patients in the linked National Cardiovascular Data Registry and centers for Medicare & Medicaid services payer databases.

BACKGROUND: Black, Hispanic, and Asian patients have been underrepresented in percutaneous coronary intervention clinical trials; therefore, there are limited data available on outcomes for these race/ethnicity groups. METHODS AND RESULTS: We examined outcomes in 423 965 patients in the National Cardiovascular Data Registry CathPCI Registry database linked to Medicare claims for follow-up. Within each race/ethnicity group, we examined trends in drug-eluting stent (DES) use, 30-month outcomes, and relative outcomes of DES versus bare metal stents. Overall, 390 351 white, 20 191 black, 9342 Hispanic, and 4171 Asian patients > 65 years of age underwent stent implantation from 2004 through 2008 at 940 National Cardiovascular Data Registry participating sites. Trends in adoption of DES were similar across all groups. Relative to whites, black and Hispanic patients undergoing percutaneous coronary intervention had higher long-term risks of death and myocardial infarction (blacks: hazard ratio, 1.28; 95% confidence interval, 1.24-1.32; Hispanics: hazard ratio, 1.15; 95% confidence interval, 1.10-1.21). Long-term outcomes were similar in Asians and whites (hazard ratio, 0.99; 95% confidence interval, 0.92-1.08). Use of DES was associated with better 30-month survival and lower myocardial infarction rates compared with the use of bare metal stents among all race/ethnicity groups except Hispanics, who had similar outcomes with DES or bare metal stents. CONCLUSIONS: Black and Hispanic patients undergoing percutaneous coronary intervention had worse long-term outcomes relative to white and Asian patients. Compared with bare metal stent use, DES use was generally associated with superior long-term outcomes in all racial and ethnic groups, although these differences were not statistically significant in Hispanic patients.