Overview
Founded in 1949 as a medical repair shop, Medtronic Inc. has steadily grown to become a global leader in medical technologies, initially producing pacemakers before expanding to cover the variety of products available today. 40,000 employees in 120 countries, with 44 manufacturing facilities, and 25 research and development centres worldwide ensure they are always at the cutting edge in regards to R&D, producing products that comply with their mission of alleviating pain, restoring health, and extending life.
Cardiovascular and Cardiac Rhythm Disease Management make up over half the total revenue for the company with the evolution of new technologies such as continuous sinusoid technology (CST) for coronary stents, ensuring Medtronic remains as a leader in medical product development. We visited Medtronic’s manufacturing and technology development facilities in Galway, Ireland for a tour of how the R&D, operational processes, and quality assurance is combined to create the new Integrity Bare Metal Stent (BMS) and Resolute Integrity Drug Eluting Stent (DES), both utilising CST.
Continuous Sinusoid Technology (CST)
Coronary stents used by cardiologists in the treatment of coronary artery disease were originally limited to tubular mesh or slotted tube stent designs. Medtronic has historically been known for its modular stent technology, as is featured in their Driver stent. However, Medtronic have advanced this technology to the next level with the introduction of CST, which results in superior flexibility and deliverability compared with the Driver and also other commercially available stent platforms (Fig 1).1
The easiest way to imagine CST is with a slinky design (Fig 2), whereby a continuous piece of wire can flex easily in all planes. The wire involved in the construction is already round so therefore doesn’t require extensive polishing to remove any sharp edges which can lead to metal fatigue. The stents are also made with cobalt chromium alloy which when compared with stainless steel allows for a reduction in stent strut thickness (enhanced delivery and lower rates of stenosis), better radiopacity, and greater strength.
The continuous range of motion due to the wire-forming process and fusion pattern provide greater flexibility and conformability while maintaining radial strength. This is particularly apparent on tight bends or tortuous anatomy where the CST stent tracks very easily, whereas with traditional stents significant gaps can occur or edges can raise damaging the sensitive intimal lining of the artery being passed through.
Stent Diameters
Whilst there are a wide range of stents diameters available (2.25 to 4.0mm) in reality only two stent designs are manufactured for the Integrity platform. Each of the two stents manufactured are crimped onto the appropriate sized balloons, with the nominal diameter of the balloon determining the diameter of the stent once placed. This provides a much greater opportunity to post inflate the stent if it is determined the original placement was undersized.
Open Cell Design
One of the major advantages of the Integrity stent is its open cell design. Basically this relates to the perimeter of a cell between fusion points that can be expanded in the case of allowing for sidebranch access. This is particularly important for complex interventions, allowing accurate positioning and adequate wall coverage. The Resolute Integrity stent has a cell perimeter of 28.9mm (small vessel design), compared to other popular stents such as the Xience Prime with only 14.42mm.2
This increased cell perimeter is achieved through the specific fusion pattern determined by Medtronic’s engineers. Every 4th stent crown (medium vessel) and every 5th crown (small vessel) are fused.
The Manufacturing Process
The Future of Stents
CST gives rise to broad applications for the development of next generation BMS and DES. These include the development of drug-filled stents, which forgo the need for a polymer coating, and core wire stents for thinner struts, amongst other design benefits.
Factory Tour
Visiting the Medtronic manufacturing plant in Ireland is an amazing experience. The large amount of labour required working harmoniously alongside sophisticated automations makes you understand the value in the final product. The entire process is rigorously checked for quality, and the employees show pride in the products they make.
For more information visit www.medtronic.com
References:
1: Coronary Heart Publishing Ltd confirmed this on external models only.
2: Test data provided by Medtronic, Inc.
