The Björk-Shiley and Ionescu-Shiley Heart Valve Prostheses In Vitro Comparison of Their Hydrodynamic Performance in the Mitral Position

Abstract

Shiley Scientific Inc., are now manufacturing six types of prosthetic heart valves. There are four different models of the Björk-Shiley and two versions of the Ionescu-Shiley pericardial heart valve. The Björk-Shiley valves are those with a spherical disc, 60° and 70° opening convexo-concave discs, and the latest monostrut model. The Ionescu-Shiley valves are the original titanium stent model and the latest Delrin stent low profile model. The hydrodynamic performance of these valves in the mitral position all having a tissue annulus diameter of 29 mm, has been measured. Tests were performed in a pulse duplicator simulating sinus rhythm at heart rates of 60, 80 and 120 beats per minute (BPM) with a stroke volume (SV) between 69 and 73 ml and at a heart rate of 200 BPM with SV between 27 and 34 ml. The latter test condition simulates a situation of supraventricular tachycardia. Mean transmitral pressure, regurgitation, and transmitral energy loss for each valve under each set of conditions were compared. All the Björk-Shiley valves were tested in two orientations with the major flow orifice oriented either anteriorly (A) or posteriorly (P). For all valves, it was found that the major contribution to the total transmitral energy loss, most apparent at 200 BPM, was caused by regurgitation and that at 60, 80 and 200 BPM, the forward flow phase contributed only a small amount to the total energy loss. The small intentional leakage across the Björk-Shiley valves is minor compared to closing regurgitation but is a major contributor to transmitral energy loss. Posterior orientation of all Björk-Shiley valves reduced closing regurgitation and total transmitral energy loss to a small but measurable extent. The overall hydro-dynamic performance of the Ionescu-Shiley valves was better than the Björk-Shiley valves because of their superior regurgitation phase performance. All Björk-Shiley valves exhibited about the same total transmitral energy loss. The improved Ionescu-Shiley low profile valve has less forward flow and total energy loss than the standard model.