A hemodynamic comparison of Omniscience and Medtronic Hall aortic prostheses

Preliminary reports have suggested hemodynamic disparities between single leaflet tilting disc prostheses. We tested the hypothesis that similarities in prosthetic design may not necessarily indicate hemodynamic equivalence.

In a retrospective analysis, we compared the functional characteristics of two single tilting disc (Omniscience and Medtronic Hall) prostheses implanted in the aortic position in 30 patients matched for valve size and left ventricular systolic function.

Echocardiographic and Doppler analysis blinded to patient and valve type indicated similar quantitative left ventricular ejection fractions (64% +/- 6% for both) and cardiac outputs (4.8 +/- 1.2 vs. 4.6 +/- 1.2 l/min, p = 0.65) in the Onmiscience and Medtronic Hall groups, respectively. Transprosthetic instantaneous peak gradients were greater for Omniscience than for Medtronic Hall valves (44 +/- 8 vs. 35 +/- 11 mmHg, p < or = 0.02), as were the mean values (24 +/- 6 vs. 18 +/- 6 mmHg, p = 0.01). Even when 21 and 23 mm prostheses were analyzed separately to allow for unequal sewing ring diameters in the smallest valve sizes (Omniscience = 19 mm, Medtronic Hall = 20 mm), higher gradients were noted in the Omniscience prostheses. Effective orifice areas were smaller in the Omniscience than Medtronic Hall prostheses whether data from all prostheses (0.92 +/- 0.11 cm2 vs. 1.09 +/- 0.18 cm2, p < or = 0.05), or only data from 21 and 23 mm valves (0.94 +/- 0.11 cm2 vs. 1.10 +/- 0.18 cm2, p < 0.05) were included. Similarly, the dimensionless obstructive index, a parameter independent of left ventricular flow and annular size, was reduced in the Omniscience valves, indicating greater obstruction, whether all valves (0.31 +/- 0.04 vs. 0.36 +/- 0.07, p < or = 0.01) or only 21 and 23 mm valves (0.31 +/- 0.04 vs. 0.36 +/- .04, p < 0.001) were analyzed.

Despite prosthetic design similarities, resting hemodynamic assessment indicates greater stenosis in Omniscience than Medtronic Hall valves when placed in the aortic position. The long term effects of these differences in terms of ventricular diastolic and systolic function and mass regression requires further evaluation.