Requiem for a good mechanical heart valve: Farewell to the Medtronic Hall valve

Abstract

Advantage, Medtronic Hall and Hall Easy-Fit valves.’’ 1 When the company ceased production of its single-disc mechanical heart valve prosthesis, we, in Coimbra, acquired a stock of several hundred units of this device and have continued using them until today. This, alone, shows how much we trusted it, near to dependence. In fact, I strongly believe that this was the best mechanical heart valve ever produced! The Medtronic Hall valve was introduced to clinical use toward the end of 1977, initially with the designation of Hall‐Kaster, after the names of the surgeon (Karl V. Hall) and the engineer (Robert L. Kaster) who developed it. It was a succedaneum of the Lillehei‐Kaster (Medical Inc, Inver Grove Heights, Minn) prosthesis and came at the time when the Starr‐Edwards (Edwards Lifesciences, Irvine, Calif) ball valve and the standard 60 Bj€ (Shiley Inc, Irvine, Calif) tilting-disc valve dominated the mechanical heart valve scene. Both were hemodynamically inefficient because of the obstruction of the ball and the disc to central flow, and the latter would soon be plagued by complications, including strut fractures in successive alterations aiming at improving its efficiency, especially with the convex-concave model. As its creators put it, ‘‘the constructional ambition of the Hall-Kaster pivoting disc valve was to guarantee prosthetic longevity and to improve the hemodynamic prosthetic performance.’’ 2,3 This was achieved by innovations in the tilting axis, disc guidance mechanisms, and disc translational freedom, combined to improve flow through both orifices of the open valve. In addition, the disc was allowed to move downstream away from the housing during opening to reduce valve thrombosis. 4 Early intraoperative and postoperative studies revealed low transvalvular pressure gradients and large effective orifice flow areas, and satisfactory flow was observed through both the major and minor orifices of the prosthesis. In vitro flow studies indicated that it had improved pressure decrease characteristics compared with the Lillehei‐Kaster and the convexo-concave Bj€ tilting disc valves. 5 In a prospectively randomized study against patients receiving Bj€ aortic valves, Levang 6 demonstrated, by intraoperative measurements, better hemodynamic performance of the Hall‐Kaster valve forcorrespondingsizes.Thiswasallegedlytheconsequence not only of a better design, with a greater minor orifice size, but also of a less obstructivedisc, with its 70 opening angle in the mitral position and 75 in the aortic position, by comparison with the 60 opening of the Bj€ valve. 6-8