The heart is one of the most vital and essential internal organs in the human body. The heart is continuously pumping out blood and the circulation system helps transport essential metabolites to individual cells of the body for their metabolism. It helps supply oxygen and needed metabolites to the cells and drain carbon-di-oxide and toxic metabolites from the cell and eliminates them. On the whole, without the heart, the survival of humans is difficult.
There are many cases where the heart fails. They can be divided into two, heart attack and heart failure. The different mechanisms that affect the conduction system of the heart cause heart attack whereas the mechanisms that affect the electrical system of the heart cause heart failure. Mostly heart attack (myocardial infarction) occurs due to the death of heart muscles due to depletion of oxygen. The primary cause of the depletion of oxygen is the block (fat deposition) in the valves that supply blood to the heart (coronary artery). The ultimate and final stage of treatment for a heart attack would be the replacement of heart valves with artificial implants.
So artificial heart valves play an important role in the treatment of an array of cardiac diseases. Hence it is essential to put importance on the design and development of such implants. This can be coined in a single terminology called ‘bench to bedside’. The following flowchart diagram represents the different steps required for the bench-to-bedside process of the development of biomaterial implants.
The first step is the selection of the ideal material for the implant. The implant of our concern is the heart valve. Since it is a device that would be in constant contact with that the blood, the different blood interaction properties have to be taken into consideration. The following are the properties needed for the selection of material for the heart valve:-
- Biocompatibility
- Hemocompatibility
- Cytotoxicity
- Ability to withstand high stress and pressure
- Good mechanical strength and characteristics
- Must not trigger foreign body reaction, rejection
- Must not activate leukocytes and macrophages
- Must not induce clotting or thrombosis (thrombogenicity)
- Anticoagulant
Metals like titanium and stainless steel can be used to develop mechanical valves. Chitin and chitosan can be used to develop heart valves since they are anticoagulants. Silicon, carbon, hydroxyapatite, and collagen are other suitable materials for artificial heart valves. Proper literature analysis has to be done and the above-mentioned properties have to be considered for material selection for heart valves. Coating with nanostructural elements can prevent foreign body reactions.
The next stage in the process is the development of the biomaterial. A prototype has to be built using a suitable material. Software analysis can be done to prepare the model. A suitable design of the material can be made using software like CAD, COMSOL multiphysics etc. and 3D bioprinting can be done to obtain the biomaterial implant. The implant usually consists of two leaflets and a metal ring surrounded by a ring of knitted fabric, which is sewn onto the heart in place of the original valve. This mechanical structure can be either constructed or the design can be made through software and 3D bioprinted.
The next stage in the process is preclinical and clinical testing. Preclinical testing nowadays can be done in several software. One of those is FEA (Finite Element Analysis) where the designed product can be tested under several conditions. The developed material must withstand high stress, and pressure and must wear for a long duration. The biomechanical parameters of the heart is considered and those are imparted and tested on the implant material. Any failure would result in alternate material selection and the development of the prototype.
The clinical testing mostly consists of in vitro and in vivo analysis. A test performed outside of the living organism by making use of the isolated tissues, organs, and cells is known as in vitro testing. This process of testing helps scientists to evaluate various biological phenomena in specific cells without disturbing any variables present in the whole organism. These in vitro methods play a crucial role in the biological safety assessment of medical devices as it helps in understanding cell and tissue compatibility prior to preclinical and clinical studies. Some of the in vitro testing methods are direct contact, agar diffusion, and elusion testing.
In vivo testing of a biomaterial refers to the methodology of testing a biomaterial in the living body of a plant or an animal. This is done in order to determine the biocompatibility of the biomaterial. There are several protocols for in vivo testing of medical devices. Animal models like pigs, sheep, and goats are used for in-vivo analysis. The porcine model is of interest due to its resemblance with that of a human heart valve.
Once the prototype is successfully tested, ethical rights can be claimed and the same can be tested on humans. On obtaining successful results, we can get marketing approval and license from the regulatory bodies (like FDA) and market the product. TTK Healthcare is the largest producer of artificial heart valves in Chennai.
Shree Chitra Heart Valve is one example of an artificial heart valve. It is known for the low cost of development. The valve consists of a cobalt alloy-based cage with ultra-high weight polyethylene and a polyester suture ring. This design consists of tilting disc valves and shows superior performance compared to other heart valves. Different types of heart valves are tricuspid, bicuspid, pulmonary, and aortic.
The three main components present in the Chitra heart valve are the frame, disc, and sewing ring. The frame is a metal that is pivoted with the tilting disc that is made of Ultra High Weight Polyethylene and the sewing ring is made up of polyester fabric.
Features
- Cobalt chromium alloy- mechanical strength, corrosion-resistant, wear and tear resistant
- polyethylene- silent operation and low cavitation
- polyester- stable in nature
- Stable, hemodynamic, structural integrity, free rotation, absence of cavitation
Hence Chitra heart valve is one of the life-saving low-cost medical devices that was developed by Indian scientists. This is indeed a proud moment for the Indians.
Social Media