1、3/1Valve Prosthesis Mechanical types:caged-ball,tilting-disk,bi-leaflet advantage:durability limitation:thrombogenicity Bioprosthetic types:heterografts,homografts advantage:short term anticoagulation limitation:structural failure3/2Mechanical Valve Prosthesis Types caged-ball(Starr-Edwards)tilting-
2、disk(Medtronic-Hall)bileaflet(St Jude)Advantage:durability(1)Limitation:thrombogenicity1.N Engl J Med 1996;335:407-4163/3Bioprosthetic Heterografts advantage long term anticoagulation unnecessary(1)limitation:structural failure leaflet calcification&tissue degeneration leading to valvular regurgitat
3、ion stenosis is uncommon rate of porcine valve degeneration 26%(aortic),39%(mitral)in 10 yrs(2)1.N Engl J Med 1993;329:524-5292.Ann Thorac Surg 1990;49:370-3833/4Bioprosthetic Homografts 1956-first aortic valve homograft was used in the descending thoracic aorta for aortic regurgitation 1962-first s
4、ub-coronary use high incidence of post-op failure*(years)5101520survival rate(%)85665338re-operation(%)22628595*Circulation 1991;84(suppl 3):III81-III883/5Bioprosthetic Homografts early preservation techniques formaldehyde,chlorhexidine,propiolactone,ethylene oxide,-irridiation,freezing at-70oC graf
5、ts are nonviable high incidence of cusp rupture3/6Bioprosthetic Homograftsadvances Improving valve durability newer preservation techniques:cryopreservation by liquid nitrogen with low-dose antibiotics homovital grafts(fresh unpreserved)reduced time for graft procurement donor rather than autopsy sp
6、ecimens3/7Bioprosthetic HomograftsUniversity of Alabama 1981-1991 cryopreserved aortic grafts in 178 pts survival rate 91%at 1 year 85%at 8 years freedom from re-operation 95%at 8 yearsJ Thorac Cardiovasc Surg 1993;106:154-1653/8Bioprosthetic HomograftsPrince Charles Hsopital 1975-1994 cryopreserved
7、 aortic grafts in 680 pts hospital mortality 2.8%survival rate 77%at 10 year;45%at 20 years freedom from re-operation 69%at 15 yearsOBrian.Ann Thorac Surg 1996;60:S65-S703/9Homovital homograftsLondon grafts are harvested,stored in tissue culture medium,and used in 3 days 275 grafts implanted over 13
8、 years:147 subcoronary,128 aortic root no transmission of disease reported cumulative survival 85%at 10 yrs(94%in the aortic root gp)freedom from re-op:91%in 10 yrsJ Thorac Cardiovasc Surg 1995;110:186-1933/ 10Bioprosthetic Homograftsimplantation techniques Freehand scalloped technique retention of
9、minimal donor tissue technically challenging,require exact sizing to prevent regurgitation Cylinder technique retention of native aortic sinuses and sinotubular junction requires coronary reimplantationAnn Thorac Surg 1996;62:1069-10753/ 11Bioprosthetic Homograftsimplantation techniques Mayo Clinic
10、series 1985-1994implantation scalloped cylindernumbers59 78late mod-sev AR26%12%7 yr re-op rate24.2%11.5%Ann Thorac Surg 1996;62:1069-10753/ 12Bioprosthetic Homograftscylinder techniques improved outcome maintaining the natural valve geometry and structure ensures better aortic cusp coaptation reduc
11、es the risk of aortic regurgitationAnn Thorac Surg 1996;62:1069-10753/ 13The“Ross procedure”A double valve procedure transfer the patients native pulmonary valve into the aortic position insert a homograft into the resected pulmonary position long term follow-up of 131 pts 47%survival at 20 yrs(age
12、11-52)35%re-op(15%aortic,10%pulmonary)Circulation 1997;96:2206-22143/ 14Aortic Valve Homograft complications aortic regurgitation is the major mode of graft failure early aortic regurgitationtechnical factors(sizing,distortion)late aortic regurgitationcommissural malalignment,cuspal distortion,cuspa
13、l prolapse from root enlargement cuspal deterioration is less common3/ 15Aortic Valve Homograft endocarditis Low incidence of endocarditis affecting homografts:6%at 15 yrs(1)Treatment of choice for prosthetic valve endocarditis(PVE)mortality for PVE has been 20-50%hospital mortality reduced to 8.3%w
14、ith homografts in the treatment of PVE(2)1.Ann Thorac Surg 1995;60:S65-S702.Semin Thorac Cardiovasc Surg 1997;11:53-613/ 16Aortic Valve Homograft anticoagulation Mechanical valves risk of thromboembolism,major bleeding,stroke is approx 3%(1)with INR of 2.5-4.9 Aortic homografts anticoagulation is un
15、necessary1.N Engl J Med 1995;333:11-173/ 17Aortic Valve Homograft Conclusion Advantage of not needing anticoagulation Not yet a perfect valve Aortic regurgitaiton still occurs with modern preservation techniques structual failure also a limitation,particularly in the young patient3/ 18Aortic Valve H
16、omograft Conclusion In older patients(age 60),heterografts have a relatively low rate of structural failure,the advantage of homografts is minimal Surgical expertise required;may not be available at all institutions3/ 19Aortic Valve Homograft indications active endocarditis,particularly those with concomitant root abscess complex aortic pathology(aneurysm or dissection)when the valve is not amenable to repair or resuspension young patients(age 60)when long-term anticoagualtion is not desired or is contraindicated
