On 14 May at 15:00, in an open meeting of the Medical Promotion Council of Rīga Stradiņš University that will take place in Hippocrates lecture theatre (16 Dzirciema Street), Mr Mārtiņš Kalējs will defend his doctoral thesis Optimal mechanical parameters of structural elements of bio-prosthetic cardiac valves and choice of a proper replacing material.
Heart valve diseases are very common and potentially life-threatening. Around 2.5 % of the total population in economically developed countries are affected by these diseases. Searching for an optimal replacer for cardiac valve that has been damaged is a topical issue worldwide. Currently biological prostheses (bio-prostheses) are the most widely used for the replacement of damaged. Its leaflets are made of specially treated tissue from pig’s aortic valve or cattle’s pericardium and are integrated in a special case. Unfortunately these bio-prostheses have certain disadvantages, among which the following is the most crucial – bio-prostheses are subject to wear. It has been established that their durability is highly affected by changes in the mechanical properties of the leaflet material and the fixing case.
The aim of the study was to identify optimal parameters of the leaflet material of aortic valve bio-prostheses and mechanical parameters of their cases for the development of new, improved bio-prostheses. In addition to the theoretical aim, a practical aim was set as well – considering the identified mechanical parameters, to determine an optimal polymeric nanofiber material to be used as matrix for developing heart aortic prosthesis leaflets by means of tissue engineering.
The study successfully led to mechanical properties, which shall comply with the leaflet material of cardiac valve bio-prostheses. Data on optimal mechanical parameters of the fixing cases were also collected. This is significant information to be considered when developing new biomaterial in tissue engineering, developing new methods for the processing of biomaterials, and creating fixing cases both for conventional bio-prostheses, and for trans-catheter prostheses (prostheses, which are implanted by means of minimally invasive approach).
Several polymeric nanofiber materials were tested, but none of these did completely correspond to the pre-determined optimal parameters. However, in order to model the mechanical properties of non-treated aortic valves as exact as possible, a combined material of perpendicularly located gelatine and polyurethane fibres was recommended. The biocompatibility of these materials was successfully tested by growing connective tissue on these for a longer period. During these tests it was found that the combined material from gelatine and polyurethane fibres can potentially be used in tissue engineering of aortic valve leaflets due to its biocompatibility and slowly enough biodegradation.