Current status of valve prostheses

In vitro flow dynamics of a new mechanical cardiac valve prosthesis--"tricusp"

The hydrodynamic performance of a newly developed JCL-trileaflet mechanical heart valve prostheses (Tricusp) was measured and compared with some of the currently most used heart valve prostheses types. All experiments were performed in an electrohydraulic, computer-controlled pulse duplicator simulating the left side of the human circulatory system. Testing conditions were set according to a Food and Drugs Administration interlaboratory comparison protocol, with cardiac outputs 3.0, 4.5, 6.5 or 8.0 l/min and a constant heart rate of 70 beats/min. Mean systolic pressure differences, volume and energy losses, dimensionless pressure losses and energy loss coefficients were calculated from the recorded pressure, volume and flow tracings. The results with the Tricusp valve were found to be as good, or even better than those with the currently most used commercially available bileaflet valves.

Valve replacement in children: guidelines for selection of prosthesis and timing of surgical intervention

One hundred fifty-nine patients ranging from 3 months to 18 years old (mean, 8.1 +/- 3.7 years) underwent 162 primary valve implantations. A porcine valve was used in 104 patients, a St. Jude Medical valve in 40, and a Björk-Shiley valve in 18. The valve replaced was the aortic in 25 patients, the mitral (systemic atrioventricular [AV] valve) in 43, the pulmonary in 71, and the tricuspid (pulmonary AV valve) in 23. Hospital mortality was 6%. Patients with a Björk-Shiley valve received warfarin sodium anticoagulation, and those with a St. Jude Medical valve were given salicylates and dipyridamole. Follow-up is available on all patients 0.6 to 12 years postoperatively (mean, 6.3 +/- 2.6 years). New York Heart Association Functional Class improved in 62% and remained unchanged in 38% of the patients. Thromboembolic complications occurred in only 8 (57%) of 14 patients with a St. Jude Medical valve in the right (pulmonary) side and in 3 (12%) of 26 with the valve in the left (systemic) side of the circulation. Bacterial endocarditis developed in 3 patients, all with porcine valves. Early valve replacement, less than 2 years after detection of hemodynamic deterioration, resulted in improvement in the ventricular ejection fraction in 25 of 29 patients (from 81 +/- 14% to 90 +/- 12% of normal; p less than 0.05). In contrast, the ejection fraction remained abnormal in all 22 patients with delayed valve insertion (more than 2 years) (81 +/- 16% of normal preoperatively and 80 +/- 10% of normal following operation; p = not significant).

Clinical results after mitral valve replacement with the Björk-Shiley disc prosthesis

Between September 1971 and June 1985, 230 Björk-Shiley valves were implanted for mitral valve disease at the Department of Surgery, University of Turku. Concomitant cardiac surgical procedures were performed in 35.2% of the cases. The follow-up period was between 1 month-13 years 4 months, with a total follow-up of 986 patient years. The early mortality was 4% in patients with isolated MVR and 10% where concomitant procedures had to be performed. Since the use of cold cardioplegia there has been no mortality for isolated MVR and the mortality rate for patients with concomitant procedures has been 3.9%. During the follow-up the rate of thromboembolism was 0.4 per 100 patient years, that of thrombolic encapsulation 0.4 and anticoagulant-related haemorrhage 0.7. Ninety-five per cent of the patients were free from thrombotic or embolic complications at 5 and 10 years after surgery. The survival rate was 79% at 5 years and 72% at 10 years. Considering these results we still prefer the Björk-Shiley valve in mitral valve replacement.