Late Results with Autogenous

Transcription

1 Late Results with Autogenous Tissue Heart Valves W. Sterling Edwards, M.D. ABSTRACT Five years of experience using unsupported and mounted fascia lata and pericardial heart valves in human beings is summarized. This experience as well as the experiences reported by others has led me to the conclusion that autogenous pericardium and fascia lata-because of the raw, exposed collagen surfaces-are not satisfactory tissues from which to construct heart valves. T he concept of using the patient s own pericardium or fascia lata for construction of heart valves offers several appealing advantages over other materials. It is autogenous tissue and therefore should not be subject to rejection; it is available in adequate quantity so that multiple valves may be replaced; and valve size is not a problem. There are no difficulties with procurement, sterilization, or storage, and leaflet valves can be constructed that have less flow resistance than do ball or disc valves. Primarily, it was hoped that thromboembolic problems would be eliminated and that these autogenous valves would remain viable and flexible for many years. From 1967 to 1968, a technique was developed in our laboratory for making complete mitral valves out of autogenous tissue, either pericardium or fascia lata [3]. A bicuspid valve was cut to pattern and the annulus of the new valve sutured to the annulus of the excised mitral valve. The two chordal attachments were brought through the appropriate papillary muscles, either back into the left atrium or to the outside of the ventricle, for proper adjustment and attachment. A competent mitral valve was produced each time using this technique. Fifteen patients had such valves constructed, 8 of pericardium and 7 of fascia lata. There were 4 early failures (within six months) that necessitated reoperation, 2 of pericardial and 2 of fascia1 valves. Failure was due to separation of the chordal attachment from the papillary muscle in 2 patients and to partial separation of the tissue from the annulus in the other 2. We were encouraged by the flexibility of the autogenous tissue at this early stage in the postoperative period and believed that these early failures were mechanical and therefore correctable. The technique was discontinued in 1968 when we began to frame-mount fascia lata. Senning s [8] encouraging reports of long-term function of fascia lata as an unsupported aortic valve led to efforts on our part to duplicate and From the Department of Surgery, The University of New Mexico School of Medicine, 2211 Lomas Blvd. NE, Albuquerque, N.Mex Presented at the Fifth Postgraduate Program, The Society of Thoracic Surgeons, Dallas, Tex., Jan. 17, VOL. 12, NO. 4, OCTOBER,

2 EDWARDS possibly improve on his technique and results. Senning reported two serious problems in his early work: some mechanical difficulty in constructing a dependably competent valve, and a 10% incidence of infection of the fascia in the early postoperative period. Experiments in our laboratory in 1967 [2] showed that we could produce a reliably competent aortic valve if (1) the free edges of the three leaflets were exactly equal to each other and to the outside diameter of the aorta at a point slightly above the natural commissures; and (2) the points of attachment of the commissures were placed at exactly equal distances around the circumference and 1 cm. higher than the natural commissures. A double row of sutures was used to provide firm fixation to the aortic wall. Five patients had aortic valves fashioned in this way, 2 of pericardium and 3 of fascia lata. Follow-up at two years revealed all to be doing well, without thrombotic complications and without evidence of valve degeneration. The real drawback to the operation was the length of time consumed in constructing the valve, about twice the time required to insert a prosthesis. This led to the next logical step: mounting the tissue on a stent before insertion. Weldon [lll, Angel1 [l], and Ionescu [6] and their colleagues had published work on the use of a cloth-covered stent to mount homograft and heterograft aortic valves to be used in either the aortic, mitral, or tricuspid position. No one had attempted construction of a semilunar valve of autogenous tissue on a stent when we began to experiment with this idea in late By September, 1968, the first 2 mounted fascia lata valves had been inserted in human beings, 1 in the aortic and another in the mitral position [4]. These valves were made of autogenous fascia and were constructed over a tricuspid semilunar mold while the chest was being opened and the patient prepared for bypass. Using the stent, insertion was as rapid as with a prosthesis; and if multiple valves were required, the second or third valve could be constructed while the first was being inserted. Ionescu and Ross [SI developed a similar technique and began their clinical series in April, Early Results There were 5 failures in the first 10 patients, 2 of whom had bare metal struts and 8, struts covered with a thin layer of Teflon cloth sutured over the stent by hand. One patient developed a severe staphylococcal infection in a hematoma in the thigh incision through which the fascia had been removed, This was followed by a bloodstream infection involving the valve which led to death three weeks after operation. Two other failures were due to detachment of the fascia from the cloth at the top of the posts, and 1 to a tear in the fascia at the point of insertion of implantation sutures. The second 10 valves, 6 mitral and 4 aortic, were implanted on commercial clothcovered stents, and there were no further early mechanical problems. 386 THE ANNALS OF THORACIC SURGERY

3 Late Results Autogenous Tissue Heart Valves The late results with mounted and unmounted fascia lata valves were summarized at a workshop in Toronto in October, 1970, organized by Alan Trimble, M.D. The summary given here consists of quotations from different groups reporting at that meeting. Between 1962 and 1970, Senning [9] in Zurich reconstructed 100 aortic valves using fascia lata. Some of these were leaflet extensions, and more than half were total valve reconstructions. The early insufficiency rate after leaflet extension was so high that this procedure was discontinued fairly early in his series, and from then on he did only total valve replacements. His operative mortality was 13%. Fifty-three patients survived total aortic replacement; 8 of these developed insufficiency in the first six months, and another 8 in the next year. If the valve was functioning well at eighteen months, it usually continued to do so indefinitely. There were no postoperative thromboembolic complications and no instances of late calcification of the leaflets. In the early part of the series, infection occurred in 8 to 10% of the fascial valves in the early postoperative period: but this complication disappeared with more careful sterile technique and use of topical antibiotics on the fascia. Approximately 25 patients have survived longer than five years following total aortic valve replacement with fascia lata. Trimble [lo], using Ionescu s valve stent and valve construction technique, inserted 63 valves in 53 patients between November, 1969, and July, There were 6 postoperative deaths, only 1 of which was related to the valve. Eighteen patients who had had aortic valve replacement were carefully followed and recatheterized six months after operation. Only 2 had insufficiency murmurs at the time of discharge, but this number increased to 8 of the 18 at the end of six months. Sixteen of the 18 were found by angiography to have mild to moderate insufficiency at six months, but almost all were doing well clinically. Several of those restudied had moderate aortic pressure gradients. Trimble carefully followed and after six months restudied 8 patients who had undergone mitral replacement. There were 3 patients with insufficiency murmurs at the time of initial discharge, but all 8 had insufficiency murmurs at six months and clinically several were suffering from insufficiency and required reoperation. There was a strong impression that insufficiency had progressed in these patients. Gross and microscopical study of their fascial valves showed fibrin deposition on both sides of the fascial leaflets with a thicker layer on the shaggy outer layer. The free margin of fascia showed thickening and rolling inward, and there was shortening which retracted the leaflets away from their contact points, producing insufficiency. This was clearly progressive with time, being more advanced if the valve had been in place longer. VOL. 12, NO. 4, OCTOBER,

4 EDWARDS Trimble inserted tricuspid valves in 4 patients, and 3 had significant clinical and angiographic insufficiency at the end of six months. Pathological changes were the same as with the mitral valves but had appeared sooner and were more severe. Donald Ross [7] from London reported an eighteen-month follow-up of 162 frame-mounted fascial valves using the Ionescu stent. There were 52 aortic, 44 mitral, 44 mitral and aortic, 6 mitral and tricuspid, 3 isolated tricuspid, and 6 triple valve replacements. Ross thought that most of the patients who had had isolated aortic replacement were doing well clinically with no late deterioration over this period. In 7 patients, significant stenosis developed early which was thought to be due to the large, rigid frame in the aortic root. Two patients developed infection of the valve, and several had a problem with hemolysis without a perivalvular leak, an unusual finding in biological heart valves. Ross was less encouraged by his results with mitral valves. In his series of 44 patients who underwent isolated mitral valve replacement, there were 10 hospital deaths and 8 late, progressive insufficiencies that required reoperation. There was no infection or hemolysis with the mitral valves. Tricuspid valve replacement gave the most discouraging results of all. Ross reported 3 isolated tricuspid replacements and 12 combined with replacement of other valves, There were 5 long-term survivors, 3 of whom had florid insufficiency which eventually required reoperation. The only 2 patients who were doing well following tricuspid replacement had Ebstein s disease. Pathological observations of recovered fascial valves showed findings similar to those of Trimble: fibrin deposition on the leaflet surfaces and thickening and shortening of the leaflets, an apparent melting away of the tissue. The histological study showed dense sheets of connective tissue with revascularization at the base. It was believed by the pathologists in London and Toronto that the original fascial cells were replaced by new, fibroblastic cells which arose from the fibrin deposition on the leaflet surfaces. Trimble, Ross, and the others who participated in the Toronto workshop expressed the opinion that aortic valve replacement using fascia lata was satisfactory and should be studied further; that mitral valve replacement with stented fascia was unsatisfactory and should perhaps be discontinued; and that tricuspid replacement was disastrous and should without doubt be abandoned. Ross has concluded that the cause of late failure is turbulence leading to fibrin deposition, and that this could be minimized by returning to the use of unsupported fascia in both the aortic and mitral areas. Ross believed that the rigid frame in the aortic and mitral annulus and the unnatural semilunar tricuspid valve in the mitral area were the cause of this turbulence. He stated that he thought a bicuspid mitral valve of fascia with chordal attachments to the papillary muscles should produce minimal turbulence and reduce the problem of fibroblastic retraction. 388 THE ANNALS OF THORACIC SURGERY

5 Autogenous Tissue Heart Valves Recently, we have had an opportunity to obtain late follow-up on several of our own patients who underwent aortic and mitral valve replacement using unsupported autogenous tissue. Three of 8 patients with mitral valves constructed of unsupported pericardium and 2 of 7 patients with mitral valves of fascia have had reoperation from two and one-half to three years after the initial operation. The valves were bicuspid, were unsupported by frames, and had chordal attachments through the papillary muscles to the outside of the left ventricle. The reoperations were required because all 5 patients had symptoms of mitral stenosis. The tissue leaflets, both pericardial and fascial, were found to be thickened, inflexible, and fused together in a fibrous mass. There was microscopical but not gross calcification of the leaflets. Two of the 5 patients who had unsupported aortic valves have undergone reoperation or postmortem examination three to four years after valve insertion. One valve of pericardium and 1 of fascia had functioned well for two to three years but then developed symptoms of mixed stenosis and insufficiency. Pathological study revealed fibrotic thickening, loss of flexibility, and fusion of leaflets. Again there was microscopical but no gross calcification. There was a striking resemblance of pathological changes in the two valve areas-aortic and mitral-and in the two autogenous tissues used, whether pericardium or fascia lata. Comment One conclusion reached by all those working on fascial heart valves is that fascia lata functions longest in the aortic position. It is less satisfactory in mitral replacement and totally unsatisfactory in tricuspid valve replacement. Donald Ross [7] and Allen Yates [12] have become discouraged with stented fascial valves and are returning to aortic and mitral replacement with unsupported fascia. They believe that the fibrotic reaction of stented valves is due to unnatural turbulence around these valves, causing thrombus formation on the leaflets with secondary organization and contraction. The difference in success with the different valves, they believe, is explained by the different amount of turbulence in the aortic area, since the semilunar supported fascial valve closely resembles the natural aortic valve. The stented mitral valve is extremely unnatural and fails more rapidly because of greater turbulence. The rapid and uniform failure of stented tricuspid valves may be due to low pressures and low oxygen saturation as well as to excessive turbulence. My experience with unsupported valves of autogenous tissue leads me to believe that this is partly true, that turbulence does play at least a part in the failures. Our unsupported mitral valves functioned nicely for two and one-half to three years before becoming fibrotic, a great deal longer than the supported mitral valves which began to fail in six months. These unsup- VOL. 12, NO. 4, OCTOBER,

6 EDWARDS ported valves were made to duplicate the natural valve closely, which presumably resulted in less turbulence. The fact that these valves stiffened and fused at three years suggests that there must be an additional factor. I think this factor is the bare collagen surface that is exposed to the bloodstream when pericardium or fascia is used. It is well known that platelets accumulate on raw collagen surfaces, leading to active thrombus formation. The rougher shaggy outer surface of fascia always develops a microscopically thicker layer of deposited fibrin and platelets than does the smoother inner surface. Perhaps the more satisfactory long-term function of aortic homografts is due to the smooth endothelial lining of both sides of the leaflets, which discourages fibrin deposition. References 1. Angell, W. W., Wuerflein, R. D., and Shumway, N. E. Replacement with fresh aortic valve homograft. Surgery 62:807, Edwards, W. S. Aortic valve replacement with autogenous tissue. Ann. Thorac. Surg. 8:126, Edwards, W. S., and Holdefer, W. F., Jr. Partial and Complete Reconstruction of the Mitral Valve with Pericardium. In L. A. Brewer (Ed.), Prosthetic Heart Values. Springfield, Ill.: Thomas, P Edwards, W. S., Karp, R. B., Robillard, D., and Kerr, A. R. Mitral and aortic valve replacement with fascia lata on a frame. J. Thorac. Cardiovasc. Surg. 58:854, Ionescu, M. I., and Ross, D. N. Heart valve replacement with autologous fascia lata. Lancet 2:235, Ionescu, M. I., Wooler, G. H., Whitaker, W., Smith, D. R., Taylor, S. H., and Hargreaves, M. D. Heart valve replacement with reinforced aortic heterografts: Technique and results. J. Thorac. Cardiovasc. Surg. 56:333, Ross, D. N. Discussion at the First International Round Table on Fascia Lata Heart Valves, Oct , 1970, Toronto, Canada. 8. Senning, A. Fascia lata replacement of aortic valves. J. Thorac. Cardiovasc. Surg. 54:465, Senning, A. Discussion at the First International Round Table on Fascia Lata Heart Valves, Oct , 1970, Toronto, Canada. 10. Trimble, A. S. Discussion at the First International Round Table on Fascia Lata Heart Valves, Oct , 1970, Toronto, Canada. 11. Weldon, C. S., Ameli, M. M., Morarati, S. S., and Shaker, I. J. A prosthetic stented aortic homograft for mitral valve replacement. J. Surg. Res. 6:548, Yates, A. Discussion at the First International Round Table on Fascia Lata Heart Valves, Oct , 1970, Toronto, Canada. 390 THE ANNALS OF THORACIC SURGERY