Every day, a healthy human heart pumps 2,000 gallons of blood through 60,000 miles of blood vessels. Given this demanding workload, it’s not surprising that people can suffer heart complications. People are living longer lives and the number of patients with cardiovascular disease is growing. As the average age and weight of the population increases, so does their propensity to develop cardiovascular disease. Significant advancements to minimally invasive cardiovascular treatments are improving physicians’ ability to treat heart disease, while specialized interventional cardiovascular techniques are becoming increasingly important to slow its progression.

Fig. 1 — Pellets, film, disk, and tubing made of thermoplastic polycarbonate-urethane are shown.
In a world where cardiovascular disease affects more of the global population than any other disease, pressures on healthcare systems and costs are soaring. Healthcare systems worldwide are faced with finding ways to offset these spiraling costs. Patients need hospitals and outpatient clinics to provide their clinicians with access to the latest advances in medical technology, while medical device manufacturers need access to the latest advancements in the biomaterials that are integral to the performance of those devices. Devices made from cutting- edge biomaterial technologies allow clinicians to provide highly sophisticated and less painful procedures as well as more targeted treatments.

Challenges of Navigating the Cardiovascular System

Cardiovascular therapies need to be robust and durable, yet delicate, due to the complex vasculature of the heart. The intricate network of vessels and the sensitive nature of endothelial surfaces in the cardiovascular system require simplified navigation and manipulation inside the body. Cardiovascular devices located in the blood stream require non-thrombogenic surface chemistry in order to prevent clot formation and blockages.

When foreign materials are implanted into the body there is always a risk of bacterial and fungal infections, particularly catheter-related infections, which significantly contribute to the increasing problem of nosocomial infections. To reduce the incidence of intravascular catheterrelated bloodstream infections, it is important that biocompatible material technology continues to advance so that its potential contribution to these complications can be reduced or eliminated.

In the face of these anatomical and operational challenges, medical device manufacturers are continuously searching for smaller components that enable the development of low-profile devices. These devices benefit not only clinicians who must maneuver the complicated anatomy of the cardiovascular system, but also patients seeking faster recovery times. One of the biggest trends in medicine and minimally invasive surgery (MIS) relies on innovative devices that are smaller and work well in complex vasculature.

Fig. 2 — ComfortCoat® hydrophilic coating is used on a balloon catheter to advance device deliverability.
Medical devices designed for MIS make procedures easier and less timeconsuming for clinicians, while also reducing the risk of tissue damage. Patients find value in MIS because it can mean reduced postoperative pain, hospitalization, and scarring, as well as a faster return to a normal life. MIS has evolved into the gold standard for efficient, low-risk cardiovascular procedures that reduce the possibility of error.

Driving the development of biomedical material solutions is a thorough understanding of how advanced materials can be used in the human body to strengthen or replace body parts and accurately deliver medicines. There are four major platforms of biomedical materials that are changing the way cardiovascular device manufacturers develop novel products — polyurethanes, coatings, fibers, and drug delivery technologies.

Polyurethanes

Biostable polyurethanes are a crucial component in cardiovascular medical devices and have a proven track record in human implantations. These specialized elastomeric materials are not only flexible, but also, strong, lightweight, durable, and interact safely with the human body making them ideal materials for long-term implantation. Polyurethanes, having extensive property and structural diversity, are one of the most biocompatible materials known today. These materials have played a major role in the development of a wide variety of cardiovascular medical devices ranging from central venous catheters to the total artificial heart. Properties such as durability, elasticity, fatigue resistance, compliance, and acceptance or tolerance in the body during healing are crucial given that the heart beats an average of 70 times per minute.

Additionally, the potential for bulk and surface modification with a hydrophilic and hydrophobic balance is possible through modification of the chemical end groups typical in a polyurethane structure. These end group modifications can be designed to mediate and/or enhance the acceptance and healing of the device or implant.

Biostable polyurethanes have diverse capabilities in cardiovascular applications because they can endure many different, innovative processing techniques that are used to manufacture complex devices. Polyurethanes can be processed by extrusion and injection molding techniques to become part of devices that feel and behave like natural tissue, giving them an important role in nextgeneration devices.

Fig. 3 — Examples of UHMWPE fibers.
Thermoplastic polycarbonate-urethane (PCU) is well known as a medical grade polymer due to its long-term durability in implants. PCU, shown in Figure 1, has many clinical applications because of its biostability, biocompatibility, and oxidative stability. When compared to conventional silicone elastomers, its abrasion resistance makes it ideal for use in pacemaker leads, heart pump membranes, and stent coatings. PCU also has the potential to replace porcine tissue in next-generation heart valves, which has the potential to reduce the risk of foreign material rejection.

Coatings

Medical-grade coatings have become an important feature in many catheter and guidewire tools used to deliver implants, such as stents, stent grafts, and heart valves. Catheters and guidewires used to deliver these devices require lowfriction, flexible, and durable delivery systems. Catheter delivery systems may require insertion through narrow pathways and the delivery system itself must not damage the surrounding vasculature, making it crucial that the coatings on guidewires and catheters drastically reduce friction.