[1] He created this artificial bioprosthetic heart valve as a three-cusp structure made of chemically treated bovine pericardium attached to a Dacron cloth-covered titanium frame.
[2] The experimental and in vitro testing of this novel device took place in 1970, and in March 1971, Ionescu began, for the first time, the implantation of the pericardial valve in all three cardiac positions in humans.
It contained an optimal proportion of monomers and polymers and an ideal cross-link density was obtained by controlling the concentration and the pH of the solution as well as its temperature and exposure time of the tissue to its action.
The sewing rim was bolstered for better and safer attachment to the heart annuli and its shape was anatomically contoured into two different configurations to better fit in the aortic and the atrio-ventricular positions.
[5] The use of this valve generated a lot of interest expressed in several specialist symposia, academic meetings, and numerous scientific articles published over the years.
The appropriation and organisation of this enormous material and the classification and interpretation of data has been a very difficult and complex task, especially because - contrary to what it is claimed - there remains a great deal of variation in standards of reporting in all essential chapters of a scientific work.
One should however keep in mind that any single investigator should resist the temptation to write a review of such a complex matter as tissue heart valves, and to cover the subject completely and fairly.
Consequently, any scientific, logical way of establishing a therapeutic means for preventing such phenomena due to unknown or incompletely understood causes is doomed to remain empirical, and the end results uncertain.
The only solution, for patients and doctors alike, would be an artificial heart valve which carries a very low risk of clotting, and therefore would not require, in the majority of cases, anticoagulant treatment.
Anticoagulant related haemorrhage was extremely rarely reported because few patients received prothrombin depressants for long periods of time (Sublata Causa Tollitur Effectus).
The nosocomial nature of these infections is reflected in their primary microbial causes: coagulase-negative staphylococci, S. aureus, facultative gram negative bacilli, diphtheroids and fungi.
Epidemiologic evidence suggests that prosthetic valve endocarditis due to coagulase negative staphylococci that presents between 2 and 12 months after surgery is often nosocomial in origin but with a delayed onset.
As in most recent scientific reports, some descriptions of tissue valve endocarditis suffer from the same lack of clarity and standardization in the presentation of facts and do not give all relevant details for a better understanding of events and their causes.
From eight published articles of large series of patients with Ionescu-Shiley Pericardial valves, only one report presents a higher than average number of valvular bacterial infections.
It can also be considered that the minor variations occurring in the published reports are due to local hospital differences, surgical technique, general handling of the valves and other factors.
The causes for pericardial tears were described in detail[34][37] and can be summarised as an abrasive mechanism produced by the rubbing of the pericardium over the Dacron-covered margin of the supporting stent.
This explains the fact that there is no sudden catastrophic failure with the pericardial valve, except when the initial, obvious clinical signs and symptoms of incipient malfunction have been missed or disregarded by the treating physician or the patient.
There may be, in a minority of cases, some slightly different mechanisms of pericardial damage at points of three-dimensional flexure or perforation caused by the excessively long ends of sutures used in aortic valve replacement.
Valve calcification is a local representation of a general biologic phenomenon which occurs under specific conditions in various parts of the body, especially in younger individuals.
Gallo[44] conducted similar experiments using the same model as Jones and Ferrans and implanted Hancock porcine valves, with and without the T6 treatment, in the mitral and tricuspid positions of sheep.
Macro and microscopic pathology studies of failed porcine bioprostheses by Schoen and Cohn[45] showed in detail the process of tissue degeneration in valves with tears, calcification, or both.
Goffin[46] showed in a comparative histological study of explanted porcine and pericardial valves that the microscopic pathologic changes were similar in these two types of tissue.
Microscopic studies performed on porcine and pericardial valves, explanted because of failure between 12 months and 6 years, all showed gross histological changes in the structure of tissue.
Through this arrangement, the lower parts of the pericardial cusps exit from the supporting frame at its bottom, and therefore the pericardium does not bend over the upper margin of the stent, eliminating the possibility of abrasion during the closure phase of the valve.
The pericardial valve, the embodiment of the concept of 'man-made' devices, lends itself to an infinite permutation of changes of shape and physico-chemical interventions in order to improve its function, and indeed this is what happened.
The specialists at Mitral Medical Inc. retained the technique of mounting the pericardium outside the stent as in the original Ionescu valve, but found other ways of reducing abrasion.
The Sorin technicians devised yet another way of mounting the pericardium in a double layer so as to have the stent margin padded with a pericardial sheet (similar to one of Shiley's modifications[37]).
The description of clinical use and results of the 144 patients who received Sorin Pericarbon Pericardial Valves would have been of great interest, but a search through the relevant medical literature has not found any such publication from the surgical team.
In this respect, Ionescu made, in one of his early papers, a significant and rather prophetic statement: The physico-chemical and biological properties of the natural porcine aortic valve have been profoundly altered by various interventions in order to adapt it for therapeutic means.
[83] There are now more than 40 years since Doctor Ionescu introduced, for the first time, the glutaraldehyde treated bovine pericardium in clinical use in the form of a three cusp heart valve (The Ionescu-Shiley Pericardial Xenograft).