Rox Medical’s Coupler Device Shows Promise for Treatment-Resistant Hypertension

Experts claim a new medical device which resembles a twisted paper clip could potentially save the lives of those at greatest risk from stroke, heart attacks and heart failure.

Inserted into the groin, the device controls and lowers the blood pressure of even the most hard-to-treat patients. The coupler creates a chamber between the artery and the vein in the upper thigh which appears to help lower resistance and bring blood pressure down.

According to a report published in the medical journal, The Lancet, the device was effective in two thirds of cases during a study of 83 patients.

It found that those who received the device experienced an immediate reduction in blood pressure; however, one third also developed swelling in their leg which needed treatment.

In the UK, high blood pressure affects one in three adults, creating strain on the vessels carrying blood around the body, and causing them to become clogged up or to weaken. Ultimately, this can lead to significant damage to the heart or brain and can result in death.

One in 20 of those affected suffer from resistant hypertension, which does not respond to medication.

The study, led by researchers Queen Mary University of London and funded by the manufacturers, ROX Medical in California, tested the device on 42 patients with high blood pressure which had not responded to at least three types of drug intervention.

They compared the effects with 35 patients who were given the standard treatment for uncontrolled high blood pressure.

The study found “significant reductions in blood pressure” in the group fitted with the device six months after it was implanted, with fewer hypertensive complications and fewer hospital admissions for high blood pressure emergencies. This cohort of patients were also able to reduce their medication.

However, the device did have some side-effects. In almost a third of patients (29%) swelling developed in the leg in which the coupler was inserted, resulting in the need for another procedure to insert a stent in the vein.

Lead author Dr Melvin Lobo, from Queen Mary University of London, acknowledged there was more to learn about the device:

“We need more research to explore the long-term effects of the coupler, better understand its safety and understand more about how it works within the body.

“We must find better means of treating high blood pressure as drugs do not work for everyone and the coupler is a big step forward in our search for alternative treatment.”

Prof Tom MacDonald, president of the British Hypertension Society, and professor of clinical pharmacology at the University of Dundee, said the device could be “a fantastic thing for patients”.

“It’s another potentially great advance in the treatment of hypertension. It’s not without its problems, but the beauty of it is you can reverse it, and it can be given to people on top of hypertension medication.

“We now need more rigorously controlled studies and a definitive trial before it can be funded for the NHS.”

The Advanced Design of TAVI

The CoreValve Platform was designed specifically to meet the clinical needs of your TAVI patients.

Over 25% Larger Potential Orifice Area
Supra-annular design maximizes blood flow. In a comparison, CoreValve has a larger potential orifice area when implanted in a degenerative surgical bioprosthesis.

Best Degree of Oversizing Varies by TAVR Device

Different degrees of oversizing result in varying outcomes between balloon-expandable and self-expanding TAVR devices, shows an observational study published online April 2, 2015, ahead of print in Catheterization and Cardiovascular Interventions.

Although the findings are “simply hypothesis generating,” study coauthor Jonathon Leipsic, MD, of St. Paul’s Hospital (Vancouver, Canada), told TCTMD in an email, they “should at least make operators pause and think about which device may be suited for a given patient’s anatomy and annular geometry.”

Dr. Leipsic and colleagues looked at 368 patients treated at 3 experienced TAVR centers who had undergone 3-dimensional multidetector CT to evaluate annulus geometry, including short and long diameter, annulus perimeter, and area. One-year follow-up was available for 78% of patients.

Patients were assigned to 2 groups based on whether their annular size would only allow for:

• Moderate oversizing (n = 190): 5%-20% by area or 2.5%-9.5% by perimeter, described by the researchers as the favorable Sapien XT (Edwards Lifesciences) zone
• Large oversizing (n = 178): 20.1%-35% by area or 9.6%-16.2% by perimeter, described as the favorable CoreValve (Medtronic) zone

Within the moderate group, 78 patients received Sapien XT and 112 CoreValve. All those implanted with Sapien XT had devices that were oversized moderately, but among the CoreValve recipients, only 15.2% had moderate oversizing and 84.8% had severe oversizing (> 35% by area or > 16.2% by perimeter).

Within the large group, 88 received Sapien XT and 90 CoreValve. All those implanted with CoreValve had large device oversizing, whereas among Sapien XT recipients, only 46.6% had devices that were largely oversized and 53.4% were mildly oversized (< 5% by area or < 2.5% by perimeter).

Differences in Dilatation, Annular Rupture, Major Stroke

Patients in the moderate oversizing group had similar baseline characteristics, irrespective of whether they received Sapien XT or CoreValve. Those in the large oversizing group had a higher mean Society of Thoracic Surgeon score with Sapien XT than with CoreValve (6.7 vs 5.0; P = .002) as well as greater prevalence of chronic renal insufficiency (44.3% vs 18.9%; P < .001).

Most procedural characteristics and clinical outcomes were similar between the 2 device types within the moderate and large oversizing groups. Notably, there were no differences related to the degree of paravalvular leakage.

However, with moderate oversizing, CoreValve procedures were more likely to involve postballoon dilatation and resulted in higher rates of major stroke and the need for pacemaker implantation by 30 days. With large oversizing, Sapien XT cases carried higher risks of annular rupture, conversion to surgery, and acute kidney injury but—as in the moderate group—had a reduced need for pacemaker implantation at 30 days (tables 1 and 2).

“Optimal clinical performance of CoreValve and Sapien XT appears to be reached with different degrees of oversizing,” the researchers conclude. “Certain annular sizes that allow for only moderate or large oversizing, but not both, appear to benefit from a device-specific approach.”

Finding the Best Fit

Dr. Leipsic said the current study is just a starting point. “We need to continue to investigate and learn how to optimally treat each patient now with TAVR,” he noted. “With more devices available and growing experience, we have the opportunity to potentially individualize and optimize device selection.”

Appropriate oversizing, Dr. Leipsic added, can “help ensure the best clinical outcomes possible.”

Today’s clinicians have many resources at their disposal but also face challenges, he explained. “In the early days of TAVR, there were limited devices and limited sizes, thereby limiting the importance of preprocedural imaging. Now, with more [transcatheter heart valve] sizes and next-generation devices, the decisions are much more complicated and need to be taken in the context of many patient-specific factors.”

Study Provides Clarity While Reinforcing Current Practice

In an email with TCTMD, Isaac George, MD, of Columbia University Medical Center (New York, NY), praised the study as being “very informative.

“The sizing algorithms have been proposed before in the past but [their validation] is an important step in achieving better procedural outcomes,” he continued. “[The current study] reinforces our current practice for oversizing but also provides key information about how the performance of the Sapien XT and CoreValve valves [changes] at different sizing. This information could potentially be useful for patients who possess anatomic limitations for oversizing, which can thus guide the choice of valve.”

As the array of devices expands, it will be important to understand advantages and disadvantages, the ramifications of sizing, and the profile for each valve, Dr. George said, adding, “Having the ability to use multiple valves will only enhance our experience.”

While these data are a “good start,” he noted, more rigorous study of sizing will be provided by the PARTNER II and SURTAVI trials.

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Source:Dvir D, Webb JG, Piazza N, et al. Multicenter evaluation of transcatheter aortic valve replacement using either Sapien XT or CoreValve: degree of device oversizing by computed-tomography and clinical outcomes. Catheter Cardiovasc Interv. 2015;Epub ahead of print.

Dementia 'halted in mice brains'

Tweaking the brain's immune system with a drug has prevented mice developing dementia, a study shows.

The team at Duke University, in the US, showed immune cells which start attacking nutrients in the brain may be a trigger for the disease.

They say their findings could open up new avenues of research for a field that has not developed a single drug to slow the progression of the disease.

Experts said the findings offered new hope of a treatment.

The researchers indentified microglia - normally the first line of defence against infection in the brain - as major players in the development of dementia.

They found some microglia changed to become exceptionally adept at breaking down a component of protein, an amino acid called arginine, in the early stages of the disease.

As arginine levels plummeted, the immune cells appeared to dampened the immune system in the brain.

Stopping dementia

In mouse experiments, a chemical was used to block the enzymes that break down arginine.

They showed fewer of the characteristics of dementia such as damaged proteins collecting in the brain and the animals performed better in memory tests.

One of the researchers, Dr Matthew Kan, said: "All of this suggests to us that if you can block this local process of amino acid deprivation, then you can protect the mouse, at least from Alzheimer's disease.

"We see this study opening the doors to thinking about Alzheimer's in a completely different way, to break the stalemate of ideas in Alzheimer's disease."

However, the findings do not suggest that arginine supplements could combat dementia as the boosted levels would still be broken down.

'Hope'

Dr James Pickett, from the Alzheimer's Society said the study was "offering hope that these findings could lead to new treatments for dementia".

He added: "This study in animals joins some of the dots in our incomplete understanding of the processes that cause Alzheimer's disease, in particular around the role played by the immune system."

Dr Laura Phipps, from Alzheimer's Research UK, said the study was "interesting" and shed "more light on the mechanisms of immune system involvement in Alzheimer's".

But she cautioned clinical trials in people were still needed and that "the findings do not suggest that supplementation of the amino acid could mirror the benefits seen in these mice".

Facebook's Mark Zuckerberg hits back in Internet.org India row

Facebook boss Mark Zuckerberg has defended the aims of their Internet.org initiative after several Indian firms decided to pull out of the project.

In a blog post, Mr Zuckerberg argued that Internet.org's basic free services were not incompatible with net neutrality - the principle that all web services should be equally accessible.

"We fully support net neutrality," he wrote. "Universal connectivity and net neutrality can and must co-exist."

But critics were quick to respond.

Writing in the Hindustan Times, India's Save The Internet coalition maintained that Internet.org is "Zuckerberg's ambitious project to confuse hundreds of millions of emerging market users into thinking that Facebook and the internet are one and the same."

Distorting competition?

At the heart of the row is Internet.org's policy of "zero-rating", whereby telecoms providers agree not to pass on the costs of handling the data traffic so that consumers can receive services for free.

Critics argue this has a distorting effect on competition, making it difficult for publishers not signed up to Internet.org to reach the hundreds of millions of poorer people in developing economies who have no internet access at all.

But Facebook disagrees, pointing out that joining Internet.org is free for web publishers and app providers.

"We're open for all mobile operators and we're not stopping anyone from joining," says Mr Zuckerberg. "We want as many internet providers to join so as many people as possible can be connected."

However, India's leading mobile operator Bharti Airtel has also been applying zero-rating to its Airtel Zero service.

This means that consumers can access certain apps for free because the app provider picks up the data bill.

Smaller developers without the resources to do the same are at a commercial disadvantage.

Better than nothing?

Facebook chooses the services offered by Internet.org after consultation with "local governments and the mobile operators" in each country, says Mr Zuckerberg.

It is this hand-picking process that appears discriminatory to many within the industry.

But Mr Zuckerberg believes that "if someone can't afford to pay for connectivity, it is always better to have some access than none at all."

In India, Internet.org has rolled out its free basic services on the Reliance network in Tamil Nadu, Maharashtra, Andhra Pradesh, Gujarat, Kerala and Telangana.

And it has also launched in Indonesia on the Indosat network.

Boycott

This week a number of firms, including travel portal Cleartrip.com and media giant Times Group, withdrew from Internet.org

, claiming that the service conflicts with the principle of net neutrality.

The issue has certainly galvanised the Indian public - more than 800,000 people have sent emails to India's telecom regulator, Telecom Regulatory Authority of India, demanding a free and fair internet.

Indian telecoms companies have been putting pressure on the government to change the way so-called "over-the-top" mobile apps, such as Skype, WhatsApp, and Instagram, are licensed.

Such apps piggyback on the operators' networks and have benefited greatly from the proliferation of smartphones and the explosion in mobile content.

Operators want a bigger slice of the pie.

Wikileaks publishes hacked Sony emails and documents

Wikileaks has published hundreds of thousands of emails and documents from a cyber-attack on Sony Pictures Entertainment last year.

The archive apparently includes Sony conversations with Downing Street and with Hollywood figures.

In November, the entertainment company suffered a cyber-attack weeks before releasing The Interview, a film criticised by the North Korean regime.

Sony said it "strongly condemns" the Wikileaks release.

"We vehemently disagree with WikiLeaks' assertion that this material belongs in the public domain,'' the company said in a statement.

The Wikileaks dump includes more than 170,000 emails and over 20,000 documents.

After November's hack, an unknown organisation published the documents online, but it was not in an easily-searchable form.

Julian Assange, the founder of the website, justified the publication by saying the documents show the inner functioning of a multinational company and are "at the centre of a geo-political conflict".

The attack came just weeks before Sony was set to release the film about a fictional American plot to kill North Korean leader Kim Jong-un.

North Korea denied involvement in the attack but praised it as a "righteous deed".

In December, a group calling itself the "Guardians of Peace" threatened 9/11-type attacks on cinemas showing the movie, spurring Sony to cancel the film's release.

Days later, amidst growing public pressure to show the film, Sony bosses appeared to change their minds and said they would give it a limited Christmas Day release.

In January, the US imposed new sanctions on North Korea in response to the attack. And, in April, President Obama ordered the creation of a programme that would allow the US government to sanction foreign hackers.

Mr Assange is currently seeking refuge at the Ecuadorian Embassy in London after two women in Sweden accused him of rape and sexual assault.

US schools seek refund over $1.3bn iPad project

Schools in Los Angeles are seeking compensation from Apple over a $1.3bn (£870m) iPad-based education project that has gone awry.

They have sent letters to Apple and its project partners seeking refunds.

The project began in 2013 and aimed to give iPads and other computers to about 650,000 students.

It hit problems when students were able to bypass security systems on the tablets and because the computer-based curriculum was incomplete.

Cutting ties

In the letters, the LA Unified School District (LAUSD) said it was "extremely dissatisfied" with the way the project has been handled, according to a report in the LA Times.

The scheme was intended to be a way for poorer pupils to keep up with wealthier peers who already enjoyed access to tablets and other computer-based study aids.

The LA school district initially bought 43,261 iPads loaded with a maths and English curriculum designed by educational and training firm Pearson. A further 77,000 iPads were bought to be used in standardised tests.

Teachers, school heads and administrators were also expected to use the gadgets to improve lessons and the way schools were run.

"While Apple and Pearson promised a state-of-the-art technological solution they have yet to deliver it," said the letters sent to the two firms this week.

Lawyers acting for the school district are also believed to be considering legal action against the two main suppliers. In addition, the schools have cut ties with the firms and do not want them to be involved in any future development.

The letters come after repeated demands from the LA school district that Apple and Pearson improve the way the scheme was being run. In its complaints, the district said only two schools were regular users of the iPad-based curriculum and those that used it intermittently reported frequent problems.

Apple has not responded to requests for comment about the complaints.

In a statement, Pearson said it was "proud of our long history working with LAUSD and our significant investment in this groundbreaking initiative to transform instructional practices and raise expectations for all students".

The statement acknowledged the "challenges" there had been in implementing the project but said it stood by the "quality of our performance".

The Pearson/Apple deal was one part of a $1.3bn programme that included spending $700m on improving internet access at schools.

The superintendent in charge of the LA school district who drew up and oversaw the costly programme resigned after the problems with the scheme came to light.

Is Google a fading force?

So here's a funny thing. The day after the EU accuses Google of abusing its dominance of the search market, new figures are published showing it's not quite so dominant after all.

Comscore reveals that Microsoft's Bing now has 20% of the desktop search market, Yahoo, which has a search alliance with Microsoft, has nearly 13%, and Google has a measly 64%.

So why is Europe making such a fuss? Well, I haven't been exactly upfront with you. Those figures only cover search in the US.

In Europe, Google is still virtually unchallenged, with between 90% and 95% of the desktop search market.

Why the difference? Well it may be to do with that Yahoo alliance. In the US, Yahoo was a much bigger presence than in Europe back in 2010 when it did that deal with Microsoft.

You need a certain scale in search to generate good results, particularly for more obscure queries - and in Europe, Bing has never had the volume of data it needs to really put a dent in Google's lead.

In the US, it seems that Microsoft has been able to build on the data shared with Yahoo to get some momentum behind Bing.

Of course, in Europe, Microsoft and the other companies which were party to the complaint to the European Commission, argue that Google has used its virtual monopoly to stop rivals gaining ground.

Outdated concern

Google's response has been that its desktop dominance is an outdated concern in the mobile internet era, when we are all using virtual assistants like Siri and Cortana, or typing queries into the Amazon or eBay search boxes.

But the EU's move to launch a new investigation into Android suggests that it doesn't buy the argument that Google is any less powerful in the mobile world.

With Android the market leader in mobile phones, and Google Now being promoted as an easy way to get instant information on any device, the company seems to have its mobile ducks in a row.

So what do the stats show?

Well the web analytics firm Stat Counter says Google has 95% of the mobile search market in Europe right now, and even in the US it has 85%.

In other words, the Californian firm shows no signs yet of being vulnerable in a world where our phones are our main means of gathering information or buying goods.

And that means that European regulators and a host of competition lawyers can settle in for many years of jousting over the business practices of an internet superpower.

Type loser.com on Ur browser, press enter and see for Ur self. It's a surprise!

And if that's not enough, go to Google images, type loser.com on the search box and see what comes out. Now, who did this?

RePneu Lung Volume Reduction Coil

The RePneu is a lung volume reduction coil which offers an alternative to traditional surgery. It is a new, minimally-invasive treatment designed to improve lung function, exercise capacity and quality of life for people with advanced emphysema. 

The coil acts by a simple mechanical action of tissue compression and the desired effects are therefore achieved without collateral ventilation interfering with treatment outcome.Most endoscopic treatment methods focus only on reducing lung volume by blocking or destroying parts of the emphysematous lung.

PneumRx’s approach was to develop a technique to help restore elastic recoil in healthier regions while simultaneously achieving lung volume reduction of highly diseased areas of the lung. The re-tensioning effects of the RePneu Coil also tether small airways, helping to hold them open and preventing airway collapse during exhalation. 

The manufacturer provides that the coils are made of Nitinol and programmed with shape memory which means that after being straightened for insertion into the lung, they gather up and compress the diseased lung tissue surrounding them as they return to their original shape. The coils improve lung function in three ways:-

- Coils compress diseased tissue which provides room for healthier tissue to function;

- Coils retension adjacent parenchyma helping to restore the lung’s natural elasticity enabling the lung to more efficiently contract during the breathing cycle;

- Coils tether open small airways preventing airway collapse during exhalationwhich reduces air trapping and hyperinflation.

Click here to read PneumRx's description on how the device works and to view an explanatory video

Click here to view the manufacture's brochure which provides full details about the device 

The Design of Interventional Devices: An Engineer’s Perspective

Background

The general notion of human beings developing tools to aid in the completion of tasks is not a new concept. But what has changed over the last 20 years is the onset of new technological breakthroughs, such as newer engineered materials and more precise processes, which have enabled better, more complex tools to come to fruition. The medical device industry has benefited from these new technologies, which have enabled physicians to discover improved concepts for instruments and treatments, improving both procedural outcome and quality of life for patients worldwide. Not since the day when Dr. Christiaan Barnard utilized the mechanical perfusion machine to enable the first human-to-human heart transplant2, have we seen such a convergence of physicians and tools for the advancement of cardiac procedures up to the levels that we see today. Yet, inasmuch as today’s interventionalist is a part of every device design, there was an engineer, or team of engineers, who helped make today’s devices a reality. How engineers go about bringing life to an interventional device can be described as part science, part “magic,” and generous amounts of innovation.

Thanks to the efforts of Dr. Sven-Ivar Seldinger in the early 1950’s3, the method for safe and reliable vascular access became a reality. The Seldinger technique opened the door for physicians to efficiently access blood vessels, allowing for direct access to vital organs without major surgery. With this new access procedure, physicians began to think of new ways to treat various disorders. Dr. Forssmann’s concept of the vascular catheter became the default vehicle by which everything from localized drugs to vascular stents and other implants made their way into patient anatomies. But as the procedures for vascular treatments evolved, the need for better performing catheters grew, in both scope and outcome. The simple plastic tube was no longer good enough to meet the needs of physicians with ever-growing skill-sets. Devices needed to be smaller in crossing profile, easier to advance, quicker to introduce and retract, more laterally flexible, and easier to visualize — all while maintaining hemostasis, sterility, tensile and compressive strength, and torque-ability, while being atraumatic. Skilled interventionalists, who were developing new ways to treat more vascular disorders, were now driving the need for modern catheter design. 

Engineering design challenges

Though we understand the methods and skills used every day in the cath lab, the technology that drives innovation in the design of new devices changes regularly, and we see the results of this change in the myriad of new products that become available. This is the nature and cycle of device design; what exists today as a device and procedure, tomorrow becomes the same device used in a different procedure, which then evolves into a next generation product, enabling the new procedure to become commonplace. So what then, from a designer’s point of view, are the critical points of interventional device design? 

Engineers commonly apply all of the tools available to them to advance the design of modern interventional devices. Everything from advanced physics, miniaturized mechanisms, engineering polymers, structural enhancements like braid and coil wires, electronics and intricate user controls, all have all been employed in successful devices. By combining a variety of these features in a device design, the engineer has the opportunity to “fine tune” the functionality of the design to meet the user needs. A good example of this is a guide catheter — an elongate tubular structure, having a proximal hub and a distal tip, and a working lumen by which drugs, implants, or other devices can be passed easily through. The considerations taken in the design of a guide catheter might include:

• What part of the anatomy will the device have to pass through?
• How tortuous is the required path of the device?
• What is the required maximum crossing profile of the device?
• How will the device be visualized?
• What will be passed through the device?

These questions can be used to identify some key aspects of the device design itself, such as:

• Device working length and flexibility to reach the required treatment site;
• Combinations of lateral flexibility and axial stiffness to maneuver through tortuous paths;
• Preset bends to accommodate device positioning and/or seating;
• As low a crossing profile as physically possible, to fit into required small diameter vessels and reach distal sites;
• The use of markers and components to enable ultrasonic and/or fluoroscopic visualization;
• The use of advanced materials such as PTFE4 and HDPE5 to provide the working lumen with lubricity, chemical resistance, and working lumen patency.

It is a primary goal of the engineer to leverage both design skills and materials technology to make these ideal features a reality. Every material offers specific properties, which enable characteristics like lubricity or flexibility in the device. The engineer uses his skills in process design to manipulate the material so that it can be extruded, bonded, folded or wrapped, collapsed or expanded, to become part of the device itself. 

As much as the materials in a device affect how it performs, the design of the user interface can mean the difference between an easy procedure and one fraught with complications. In effect, the translation of the device design and use with the end user should be both transparent and intuitive. The ideal device is self-explanatory, ergonomic, robust, and reliable in use.

Materials

The types of advanced materials used in today’s interventional devices are not so different from those used in fighter jets and aerospace vehicles. Metals such as nickel-titanium and chromium cobalt are seen regularly in implants like stents and vascular staples. Engineered polymers such as PTFE, HDPE, and Vestamid6 are used on catheter shafts and device handles. Advanced, engineered fiber such as Kevlar7, once known only for its bullet-stopping prowess, is now used in steerable catheter mechanisms and valvuloplasty balloon catheters. And advanced adhesives and thermal bonding methods allow for very low profile device joints, which can withstand the tensile, compressive and torsional forces seen by a device during clinical use.

The engineer will evaluate a specific design requirement and determine what material will yield that characteristic in the design, while still being safe, robust, easy to manufacture, and reliable. A prime example is the design of an over-the-wire balloon catheter having an inner member shaft. The inner member shaft must be lubricious to allow the device to slide over the guidewire with very low friction, even around tight radius bends. The inner member shaft must also be able to handle the inflation pressures required by the device, which means that the material used for the shaft must be able to reliably bond to both the balloon and to the proximal hub, to handle these very high pressures. The inner member shaft must also provide adequate hoop strength, so that the shaft does not kink as the device is advanced around a tight bend radius. As simple as an inner member balloon shaft is, it is easy to see that the component is required to meet or exceed many design requirements. 

In some situations, the engineer can leverage certain characteristics of a material to reduce costs, increase strength and reliability, reduce profile, or improve visualization. For example, many devices employ radiopaque marker bands, typically made of platinum/10% iridium, to act as fluoroscopic markers on the product for location and positioning purposes. But in some cases, the attachment of a metal marker band can add unwanted profile, stiffness, or additional bonding requirements to the product. In the case of a radiopaque distal tip marker, the engineer can replace the metal marker band with an engineered polymer such as polyether block amide, commonly known as Pebax8, which can be loaded with 70% tungsten. The material can be thermally formed into a shaft or ring-shaped component, which can then be thermally bonded to the catheter tip; the thermal bond reduces the profile of the joint and strengthens the attachment, while the tungsten filler provides needed radiopacity. This method also has a positive effect on the cost of the device; a platinum/10% iridium marker band can cost $3.50 a part in quantity, while the Pebax ring loaded with 70% tungsten can cost $0.45 a piece for the same quantity. 

Sometimes, the use of a particular material can degrade the functionality of a device, or it can enable enhanced device functionality. In the case of a stent delivery catheter, for example, the inner surface of the stent delivery catheter may be lined with a lubricious material such as PTFE. PTFE, commonly known as Teflon, is an engineered fluoropolymer, which possesses the lowest coefficient of friction of any polymeric material. But the downside of PTFE is that it is so slippery that attaching it to any substrate is very challenging and can be very expensive. Also, PTFE can tear easily, and tends to be very notch-sensitive. This means that, as a liner for a stent delivery catheter, PTFE material requires that the stent itself, and anything else passing through the working lumen, be very smooth and atraumatic, or else risk tearing the catheter liner during delivery, causing the stent to become jammed within the delivery system lumen. In this case, the PTFE liner would be a challenge to use in this stent delivery device. If the implant possessed rough edges, sharp anchors or barbs, the engineer could leverage an engineered polymer such as nylon-12, commonly known as Vestamid, which is a very robust polyamide that also provides lubricity close to PTFE, while being tear-resistant and less expensive. This means that a catheter lined with Vestamid, or even made entirely of the material, can be more reliable, and also less expensive, than the PTFE-lined design, at least in this application. So it is easy to see how engineers balance material selection to design the optimum device.

Interface

In the most basic sense, the engineer is challenged with matching human to machine, user to tool, and ultimately device to patient. The interventional device becomes the bridge between physician and patient, enabling the physician to access the treatment site while minimizing trauma to other parts of the patient anatomy. In some instances, the interventional device becomes an extension of the physician’s own hands, allowing positioning and placement of implants, localized delivery of medications, or clearing/extraction of emboli. The intuitiveness of the device design, combined with reliable user controls that are easy to understand, can enhance patient outcome while minimizing complications or procedural time. Along with this intuitive functionality, the device must be easy to visualize, such that the physician can interpret the position and location of the device during clinical use.

The distal end of the device, where the actual treatment activity typically occurs, must feel like a one-to-one extension of the device proximal end. Whether the proximal end of the device is a simple luer, or an intricate electro-mechanical handle, the user must feel confident that whatever input he introduces into the device results in a direct, predictable output at the distal end of the device. If the physician pushes forward or pulls back, he expects the distal tip to advance or retract. If the physician twists the handle, he expects the distal tip to rotate axially. And if the physician pulls back on a deployment knob, he expects an implant to deploy. In an ideal world, these functions happen seamlessly, every time. But the engineer must contend with real-world physical variables, such as friction, tortuosity, extended working length, tight design tolerances, and patient variation, to name a few. In the design of the interventional device, the engineer must take into account limitations of every component and each type of material used in the design. There is a constant balancing act between leveraging the positive aspects of a material with the materials limitations. As an example, if a catheter must traverse over a very long distance, such as a neurovascular micro-catheter, the engineer might elect to employ a shaft support component, such as stainless steel braid, which can enhance pushability while also enhancing kink-resistance. But braid support can limit the lateral flexibility of the micro-catheter in very tortuous distal vasculature, and so the engineer can integrate a stainless steel coil support component to just the distal portion of the catheter, which enhances distal lateral flexibility while adding hoop strength for even better kink-resistance. In addition, the engineer can design the device to employ a hydrophilic coating, which adds lubricity to the outer surface of the catheter where it interfaces with the vessel wall, reducing friction and vessel trauma while further enhancing axial and rotational one-to-one movement.

What the physician holds in his hand during the procedure, whether it is a luer hub or a handle, is typically his only interface with the portion of the device that sits at the treatment site. Therefore, he must feel confident that his inputs into the device result in a level of tactile precision that yield predictable actions at the working end. Any amount of lag, delay, looseness, or wind-up can result in mispositioning or misalignment. In severe cases, lack of tactile precision can result in vessel trauma or vessel/organ perforation. To minimize these effects on the device, the engineer can employ advanced design techniques such as shape setting, pre-loading, advanced construction methods, support structures and hybrid materials to make up for various design shortcomings. Shape setting and pre-loading can be in the form of designing a catheter with a pre-defined distal bend, which enables the physician to access an angled vessel, and seat the distal tip portion of the guide at the vessel ostium, to prevent it from backing out of the vessel when a secondary device is advanced through it. The engineer can employ advanced construction methods such as braid wire support to enhance axial and torsional control of the catheter, reducing or virtually eliminating lag associated with push/pull or rotational input by the physician. Examples of hybrid materials include shafts, which are extruded using two or more materials, such as a catheter shaft with an inner layer of HDPE and an outer layer of Vestamid; the HDPE provides lubricity to the inner lumen, while the Vestamid provides axial and torsional stiffness needed for one-to-one control.

No device works 100% every time, and so the engineer must take into account variables in the device itself, along with patient variation, to ensure that safety and functionality work in tandem with each device deployed. Where user input is key in the operation of the device function, the user interface must also provide a level of control that enables the physician to react to variations in device function or patient variability, as well as provide a means of bail-out should complications arise. The engineer takes these variables into account, and may elect to include design features, which are meant to enable changes to the procedure in situ. These features might include controls or components which can be disconnected to allow for safe device retraction, additional lumens or working channels which enable the introduction of ancillary support devices, and device controls which have a dual function such as a deployment knob that also acts as an emergency outer sheath removal control interface. Ultimately, the well-versed engineer determines the final interface design after first-hand use in hands-on animal studies and bench testing. A good user interface must “feel” right in the hands, generate confidence, and require minimal instruction and support during use.

Final comment

The designing of interventional devices has made huge strides since the early days of investigational interventions by innovative physicians. Device design engineers leverage the use of advanced materials, advanced design processes, and innovations in interventional procedures to drive the evolution of today’s devices. Contrary to popular belief, engineers don’t typically invent medical devices on their own. The nature of every engineer is to enable and develop a physician’s idea into something tangible and useful — to make something that is not only functional, but something that is better than what was originally conceived. What comes from an engineer’s hands and mind is, more often than not, the product of clinical insight combined with engineering design methods. The most typical question that an engineer gets is “can you make something that does this?” It is from experience that the engineer can “make” something, but it is from clinical insight that a physician is able to know what he wants that something to be, and how that something should function. 

A famous Columbian bicycle frame builder, Tinno Hincapie, once said, “In order to build a great frame, you have to understand how a bike moves, how it reacts, and you have to know what it’s like to suffer when riding a bike”.9 Ultimately, the seasoned engineer must take the device in question into real-world testing, under real-world clinical conditions, for a first-hand evaluation to see how it performs and where it falters. Other than first-hand testing, the coordinated interaction between the physician and the engineer is the most efficient way to get to that successful design, and in turn, experience successful procedures with great patient outcome — something to consider the next time you perform an interventional procedure, and come up with a great new idea. 

Gil Laroya can be contacted at gillaroya@comcast.net.

References

1. The Nobel Prize in Physiology or Medicine 1956. André F. Cournand, Werner Forssmann, Dickinson W. Richards. Available online athttp://www.nobelprize.org/nobel_prizes/medicine/laureates/1956/forssmann.... Accessed February 15, 2013.
2. Encyclopedia of World Biography. Christiaan Barnard. Available online athttp://www.notablebiographies.com/Ba-Be/Barnard-Christiaan.html. Accessed February 15, 2013.
3. Greitz T. Sven-Ivar Seldinger. AJNR. 1999; 20: 1180-1181. Available online at http://www.ajnr.org/content/20/6/1180.full. Accessed February 15, 2013.
4. PTFE and Polytetraflouroethylene is a registered trademark of DuPont Corporation. Available online at http://www2.dupont.com/Teflon_Industrial/en_US/products/product_by_name/....html. Accessed February 15, 2013.
5. HDPE and High-Density Polyethylene is a registered trademark of Exxon Mobile Chemical. Available online at http://www.exxonmobilchemical.com/Chem-English/brands/polyethylene-hdpe-.... Accessed February 15, 2013.
6. Vestamid Nylon-12 is a registered trademark of Vestamid Corporation. Available online athttp://www.vestamid.com/sites/dc/Downloadcenter/Evonik/Product/VESTAMID/.... Accessed February 15, 2013.
7. Kevlar is a registered trademark of DuPont Corporation. Available online athttp://www2.dupont.com/personal-protection/en-us/dpt/kevlar.html. Accessed February 15, 2013.
8. Pebax is a registered trade name of Arkema. Available online athttp://www.pebax.com/sites/pebax/en/home.page. Accessed February 15, 2013.
9. Klaus. Steel is easy to love because it loves you back. Cycling Inquisition, November 2012. Available online at http://www.cyclinginquisition.com/2012/11/steel-is-easy-to-love-because-.... Accessed February 15, 2013.