Biological Solutions in Cardiac Surgery

Cardiac surgery has achieved remarkable progress since the first heart-lung-machine operations were performed in the fifties of the last century. Safer techniques of anesthesia and postoperative care, improved extracorporeal circulation and myocardial protection and sophisticated surgical techniques are tools which have been instrumental in reducing hospital mortality and increasing the efficiency of cardiac operations. New surgical tools impose new surgical goals. Furthermore it must be considered the quality of life given to the patient and the socioeconomic impact of the surgical actions. Biological solutions like reconstructive valve surgery, stentless valves or stem cell therapy are good examples for this way of cardiac surgery. Nowadays mitral valve repair is preferred whenever technically feasible over valve replacement. Mechanical and biologic prosthetic heart valves have different well known disadvantages. Anticoagulation is required to prevent thromboembolic complications for mechanical valves, and porcine valves have a relatively short life expectancy (seven to 14 years). Longterm data, now past 15 years of follow-up, support the durability of mitral repair with a better preservation of ventricular function, lower risk of thromboembolic complications and less need for anticoagulation. Predictable results of aortic valve repair have been difficult to achieve because the closing mechanism of the aortic valve is more precise than that of the mitral valves. The cusps have less congestive surface than the mitral leaflets. Reoperation rate because of significant residual regurgitation and the rate of moderate insufficiency not requiring reoperation are significant higher than in mitral valve repair. The aortic valve repair is only indicated in a very selected group of patients. Stentless glutaraldehyde-preserved bioprosthetic valves for the aortic position were introduced into clinical practice in 1988. Their introduction coincided with the publication of several longterm observational studies of aortic homografts which showed superior freedom from structural valve damage compared to the first generation stented porcine bioprosthesis. There followed 15 years of intensive investigation into the haemodynamic characteristics of stentless valves. These studies have demonstrated superior haemodynamic features in terms of transvalvular pressure gradients, effective orifice area and more complete regression of left ventricular hypertrophy. Despite these adva