Biocompatibility Challenges in Structural Heart Device

Structural heart device design and manufacturing have evolved tremendously over the past few decades. The evolution of these devices is characterized by the functions these devices are required to perform. For example, a specialty suture needs to have the right profile for being re-absorbable, vascular prostheses such as grafts, patches, and stents need to have flexibility, high tensile strength can be extruded to fit within the thinnest catheters, and must have controlled porosity.

The design and manufacture of structural heart devices have evolved tremendously over the past few decades. The evolution of these devices is characterized by the functions these devices are required to perform. For example, a specialty suture needs to have the right profile for being re-absorbable, vascular prostheses such as grafts, patches, and stents need to have flexibility, high tensile strength can be extruded to fit within the thinnest catheters, and must have controlled porosity.

The heart is a complex and sensitive organ subject to electric, neuronal, biochemical and muscular controls. In-depth research alone will show how each material, with a specific functional profile, will act when used in a Structural Heart (SH) Device. This is why the biocompatibility (how well the material performs with host tissues) of materials used in Structural Heart Devices is of the utmost importance.

For any medical device to receive approval from the FDA, it will have to comply with the ISO 10993-1 standard. This includes biocompatibility tests and their results proving their safety and efficacy when in contact with living tissues. In essence, biomaterials must be non-toxic, non-thrombogenic, non-carcinogenic, non-antigenic, and non-mutagenic. Today, biomaterials must go further by providing positive effects such as enhancing the healing process, promote the formation of healthy tissue, prevent clotting and also integrate well with adjacent tissues.      

Types of biocompatibility issues with biomaterials:

In general, you’ll find three main classes of biomaterials in use today. Here is a general representation of the functionalities displayed by each class of biomaterials:

As you can see from the table above, it’s clear that the biomaterial selected for the manufacture of an SH device depends on how the structural heart device will be used.

For example: For permanent use – implants within the heart such as a valve or a stent. Implants will naturally require a much longer life span and will be required to function optimally alongside the tissues surrounding them.

Temporary uses such as grafts, guidewires, catheters, sheaths, etc. Temporary devices such as grafts and patches are usually designed to be bio-degradable or re-absorbable meaning that they will be naturally absorbed by the body (within the expected time span, enabling local healing) without any side effects. Guidewires and catheters can have various coatings for specific uses such as protecting the body from exposure to the catheter, protecting electrode tips, drug coatings used in drug-eluting stents – helps prevent adverse effects (such as clotting, occlusion of blood vessels, etc.) following an interventional procedure. 

Conclusion

Biocompatibility profiles for synthetic, bio-derived, metal, coatings (passive or bioactive), and nanomaterials differ considerably. Using the wrong grade of material in a structural heart device could have an array of negative effects such as cytotoxicity, pyrogenic reaction, immunogenic response, etc.

In your material selection quest, consult with a manufacturer who has experience in sourcing the best grades of materials and that have state-of-the-art research, engineering, and production capabilities, to produce a Structural Heart Device. Since the field of biomaterials and their biocompatibility profiles is a vast one, the manufacturer should have access to a wide array of research materials that contain the engineering and biological performance of materials used in implantable cardiovascular devices as well as information about compatible coatings and drugs and manufacturing processes. For example, the database from ASM International is comprehensive, cross-linked, and fully traceable (to original sources). The database can be used for information retrieval and selection of materials, drugs, and coatings for combination devices.

Current trends include the use of breakthrough biomaterials such as Nitinol and Palladium nano-powder.