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712 PA R T I V / Pathophysiology and Management of Heart Disease
longevity has not been well proven. The main advantages of tissue
valves are the associated low rates of thromboembolism and the
subsequent decrease in patient morbidity when anticoagulant
therapy is not required. Nonthrombogenicity is particularly im-
portant for those patients in whom long-term anticoagulation
should be avoided, such as children, young adult women, those
older than 70 years, or those with a history of bleeding.
The Hancock porcine valve, the Medtronic Mosaic porcine
bioprosthesis (treated with -oleic acid to retard calcification),
and the Carpentier–Edwards porcine valve are xenografts using
porcine aortic valves preserved with glutaraldehyde under pres-
sure, mounted on a stent. 18 The Carpentier–Edwards pericardial
bioprosthesis is made of leaflets fashioned from bovine peri-
cardium fixed without pressure in glutaraldehyde.
Stentless bioprosthetic porcine xenograft valves such as the St.
Jude Medical-Toronto, the Medtronic Freestyle Stentless, and the
Edwards Prima Plus porcine bioprosthesis have been developed to
improve the durability and enhance the hemodynamic perform-
ance of porcine aortic valves. Stentless aortic biological valves were
developed secondary to the recognition that conventional bio-
prosthesis have limitations of long-term durability and residual
obstruction that may impede left ventricular mass regression. 19 ■ Figure 29-5 Illustration of Ross procedure. Suture line of pul-
Use of the stentless aortic bioprosthesis has resulted in enhanced monary homograft is shown. (From Elkins, R. C. [1998]. Valve repair
survival and hemodynamic superiority. 20 It is expected that re- and valve replacement in children, including the Ross procedure. In
ducing mechanical stress on valve leaflets, and the associated de- L. R. Kaiser, I. L. Kron, & T. L. Spray [Eds.], Mastery of cardiothoracic
surgery [p. 947]. Philadelphia: Lippincott-Raven.)
generation of the bioprosthesis, may be slowed.
Homografts or allografts from human cadavers are virtually free
of any associated thrombosis. They are especially useful in pa-
tients with small aortic roots or in patients with active endo- of technological advances, such as endoscopic and surgical equip-
carditis. Earlier homografts were preserved with glutaraldehyde ment, have been developed to evolve towards more complex,
and demonstrated early failure. Homografts are now stored video- and robot-assisted procedures. 25 Although patients under-
“fresh” after harvesting in an antibiotic solution and are then cry- going minimally invasive valve surgery still require cardiopul-
opreserved, increasing their longevity to at least 10 years. Valve monary bypass, classic median sternotomy may be avoided, thus
failure is uncommon and usually the result of progressive valve reducing pain, improving cosmetic results, and expediting recov-
incompetence. 21 Aortic allografts have demonstrated excellent ery. Endoscopic mitral and tricuspid repair is feasible even after
freedom from thromboembolism, endocarditis, and progressive previous cardiac surgery. 26 As minimally invasive valve surgery
valve incompetence. 21 Because of lack of availability, use of ho- continues to evolve, it will likely become a mainstay in the treat-
mografts has been limited. ment of valvular heart surgery.
In the Ross procedure (also known as pulmonary autograft), the Aortic valve replacement can be performed through an upper
aortic valve is replaced with a pulmonary autograft, and the native “T” ministernotomy without intraoperative difficulties. Postop-
pulmonary valve is replaced with a pulmonic allograft. Although this erative pain is reduced and recovery is expedited, with patients
procedure introduced by Donald Ross in 1967 was originally devel- discharged to home as early as postoperative day 3. 27 Compared
oped for pediatric application, it has been expanded to adult surgery with patients with median sternotomy, patients undergoing mi-
22
as well. In patients undergoing the Ross procedure, the native pul- tral valve replacement through the right parasternal approach
monary valve is excised and then implanted in the aortic position had a shortened length of stay and reduced direct hospital
(autograft); a pulmonary homograft (allograft) is implanted into the costs. 28 Most clinical series demonstrates that minimally inva-
pulmonic position (Fig. 29-5). The pulmonary autograft has been sive port-access approach to mitral valve surgery has low mor-
23
shown to be resistant to degeneration and calcification. The actu- bidity and mortality, with echocardiographic outcomes equiva-
arial freedom from pulmonary autograft valve replacement is 90% lent to conventional mitral valve surgery. 29 More recently,
22
3% at 13 years. The Ross procedure cannot be performed in pa- minimally invasive mitral valve surgery has evolved to include
10
tients with bicuspid aortic valves or dilated aortic roots. Although computer-assisted robotic techniques in current clinical trials.
the Ross procedure has limited acceptance due to the complexity of The da Vinci Surgical System allows the surgeon to operate from
the surgery and the replacement of both the aortic and pulmonic a console through an end-affecter using microwrist instruments,
valves, in young adults who wish to avoid anticoagulation, it offers which are mounted on robotic arms, inserted through the chest
an alternative with favorable midterm results. 24 wall. 30 For patients unsuitable for traditional aortic valve re-
placement due to comorbidities, percutaneous transarterial 31 or
Minimally Invasive Valve Surgery transapical aortic valve replacement are currently undergoing
investigation. Catheter-based mitral valve repair for mitral re-
Minimally invasive valve surgery is now used for both aortic valve gurgitation using clips that mimic the Alfieri stitch procedure
replacement and mitral valve repair and replacement. Minimally or annuloplasty devices placed in the coronary sinus are also
invasive surgical approaches are possible because a wide assortment currently under investigation. 32,33