Unstented and partial stented bioprostheses for aortic valve replacement--up to 6 years of follow-up

Assessment of the influence of the compliant aortic root on aortic valve mechanics by means of a geometrical model

In recent years several researchers have suggested that the changes in the geometry and angular dimensions of the aortic root which occur during the cardiac cycle are functional to the optimisation of aortic valve function, both in terms of diminishing leaflet stresses and of fluid-dynamic behaviour. The paper presents an analytical parametric model of the aortic valve which includes the aortic root movement. The indexes used to evaluate the valve behaviour are the circumferential membrane stress and the stress at the free edge of the leaflet, the index of bending strain, the bending of the leaflet at the line attachment in the radial and circumferential directions and the shape of the conduit formed by the leaflets during systole. In order to evaluate the role of geometric changes in valve performance, two control cases were considered, with different reference geometric configuration, where the movement of the aortic root was ignored. The results obtained appear consistent with physiological data, especially with regard to the late diastolic phase and the early ejection phase, and put in evidence the role of the aortic root movement in the improvement of valve behaviour.

The Cryolife-O'Brien composite aortic stentless xenograft: surgical technique of implantation

The Cryolife-O'Brien (Cryolife International, Atlanta, GA; formerly the Bravo Cardiovascular Inc valve) stentless porcine aortic xenograft (model 300) is a composite valve of three noncoronary leaflets, symmetric in configuration with a broad coaptive leaflet surface. Because the valve has only a superior aortic wall cuff, a single continuous suture line of 3/0 Prolene provides a rapid, safe implantation. The ideal recipients are elderly patients, who benefit from a short cardiopulmonary bypass period and whose degenerative calcific valves are generally symmetric. The step-by-step technique of implantation is outlined, as are the principles of maintaining symmetry during implantation. The stentless valve has been used for aortic valve replacement in 55 elderly patients, with no deaths and minimal morbidity.

Stentless xenograft valve in a truncus arteriosus communis

We report the use of a recently developed stentless porcine valve in a 2-year-old child with truncus arteriosus communis (type I). The child had received no previous surgical palliation. Despite a markedly increased pulmonary arteriolar resistance the right ventricle was connected to the pulmonary artery with a homograft. The postoperative course was complicated at first by right ventricular failure due to pulmonary hypertension and secondarily by left ventricular failure caused by rapidly increasing truncal valve incompetence. Because we did not have a suitable homograft at hand we replaced the truncal valve with a stentless porcine xenograft valve.

Modern cardiac valve devices--bioprostheses and mechanical prostheses: state of the art

The choice of bioprostheses and mechanical prostheses as valvular substitutes for cardiac valve replacement surgery has existed for over 20 years. The extensive developments over the past three decades have been introduced to reduce or eliminate valve related complications, namely thromboembolism, anticoagulant related hemorrhage, and structural failure, as well as to optimize hemodynamic performance. The biological valvular prostheses, namely porcine aortic or bovine pericardium, have been developed with tissue preservation, together with stent designs, that contribute to preservation of anatomical characteristics and biomechanical properties of the leaflets. The mechanical prostheses have been developed to eliminate structural failure, to facilitate prevention of blood status and thrombus formation, to facilitate radiopacity for evaluation of prosthesis function, and to facilitate intraoperative leaflet positioning. The implantation of the various present generation bioprostheses and mechanical prostheses requires special considerations to avoid technical complications and support ventricular performance. The studies of biological and mechanical prostheses, both randomized and nonrandomized, as well as specific prosthesis assessments, have contributed to the establishment of indications for types of prostheses. Bioprostheses have a high risk of structural failure and reoperation, while mechanical prostheses have a high risk of thromboembolism and anticoagulant hemorrhage. Within the bioprostheses population, the risk factors for structural valve deterioration are younger age and mitral prosthesis. Older patients (> 65 years of age) have a greater risk of valve related complications with mechanical prostheses, while younger patients (< 40 years of age) are at greater risk with bioprostheses. Comparison of large bioprostheses and mechanical prostheses populations by age groups revealed that regardless of the differences in the freedom from structural valve deterioration, the freedom from treatment failure (valve related mortality and permanent impairment from thromboembolism, anticoagulant hemorrhage, and septal emboli from prosthetic valve endocarditis) is essentially the same for mechanical prostheses and bioprostheses at 10 years. The quality of life is superior with bioprostheses, while patient survival and total valve related morbidity/mortality are similar with both types of prostheses.