Hemodynamic performance of the St. Jude Medical Hemodynamic Plus valve

In Vitro Hydrodynamics of Four Bileaflet Valves in Mitral Position

Hydrodynamics of St. Jude Medical, Carbomedics, Advancing The Standard, and On-X bileaflet valves with an annular diameter of 25 mm were obtained using an in-vitro test system. Steady flow studies demonstrated different pressure drops due to differences in valve design, particularly the geometric orifice diameter and the opening angle. The On-X valve produced the least pressure drop, whereas the Carbomedics valve had the greatest pressure drop. In pulsatile flow experiments, the On-X and St. Jude Medical valves consistently produced the lowest mean positive pressure gradients, while the Carbomedics valve had the highest gradients. In spite of its parallel leaflets design, the On-X valve showed a closing volume as small as that of Carbomedics valve. The results indicate that a larger orifice diameter and greater opening angle can significantly reduce transvalvular pressure loss. This study also demonstrated that attempts to improve the hydrodynamic efficacy of the On-X valve were successful in reducing the pressure gradient as well as maintaining a low closing volume.

A comparison of the in vivo performance of the 19-mm St. Jude Medical Hemodynamic Plus and 21-mm standard valve

BACKGROUND

In the present study we analyzed the in vivo performance of the 19-mm St. Jude Medical Hemodynamic Plus aortic prosthesis (19HP), evaluated the midterm performance of 19HP in the aortic position, and compared the implantability and hemodynamic characteristics of this valve with those of the 21-mm standard St. Jude Medical valve (21SD) in adult patients with aortic stenosis and a narrowed aortic annulus.

METHODS

From February 1994 to December 1999, 60 patients who underwent isolated aortic valve replacement with either the 19HP (n = 31) or the 21SD (n = 29) were studied. Comparison between the two models included analysis of early and late mortality and morbidity. Pre- and postoperative echocardiography was performed in all patients to evaluate and compare the hemodynamic performance of both prosthetic valves. The postoperative serum lactic dehydrogenase activity was measured in both groups of patients as an indicator of hemolysis.

RESULTS

The mean body surface area was 1.46 +/- 0.16 m2 in the 19HP group and 1.49 +/- 0.13 m2 in the 21SD group (p = 0.1577). Other than female dominance in the 19HP group, there was no statistically significant difference between the two groups in terms of preoperative variables (age, preoperative pressure gradients, and New York Heart Association functional class). The average postoperative peak pressure gradient was 23.3 +/- 10.5 mm Hg in the 19HP group and 27.9 +/- 9.9 mm Hg in the 21SD group (p = 0.0666). There was no hospital death in either group. Six-year follow-up was completed in both groups of patients. Late death occurred in 1 patient in the 19HP group (1.09% per patient-year). Actuarial survival at 6 years was 92.3% +/- 7.4% in the 19HP group, and 100% in the 21SD group (p = 0.33). The linearized complication rate was 1.09% per patient-year and 1.02% per patient-year for thromboembolism, and 1.09% per patient-year and 1.02% per patient-year for anticoagulant-related hemorrhage in the 19HP group and the 21SD group, respectively. Freedom from all complications at 6 years did not show any significant difference between the two groups (p = 0.54). Although left ventricular mass indices decreased significantly after aortic valve replacement in both groups (19HP group, p = 0.0002; 21SD group, p = 0.0006), there were no significant differences in the two indices between the groups after aortic valve replacement (p = 0.999). There was no significant difference in the lactic dehydrogenase level between the two groups (p = 0.4915).

CONCLUSIONS

In vivo hemodynamic performance of the 19HP valve as well as the early and intermediate clinical outcome up to 6 years was satisfactory and corresponded closely to that of the 21SD valve in adult patients. The 19-mm Hemodynamic Plus model can be recommended in patients with a measured 19-mm annulus and this valve will minimize the need for the aortic annular enlargement procedure.

In vitro investigation of opening behavior and hydrodynamics of bileaflet valves in the mitral position

The performance of four 25 mm bileaflet valves of different designs was evaluated in the mitral position of our own pulse simulator. With the aid of a high-speed video camera, it was demonstrated that both the St. Jude Medical (SJM) valve (Hemodynamic Plus [HP] Series, St. Jude Medical, Inc., St. Paul, MN, U.S.A.) and the CM valve (CarboMedics, Inc., Austin, TX, U.S.A.) were able to open fully and that the CM valve fluttered much more vigorously at the fully open position than did the SJM HP valve. Conversely, neither the ATS valve (ATS Medical, Inc., Minneapolis, MN, U.S.A.) nor the On-X valve (Medical Carbon Research Institute, Austin, TX, U.S.A.) exhibited movement to a fully open configuration. The overall average opening angles of the ATS and the On-X, on 3, 4, and 5 L/min flow rate for a heart rate of 70 bpm and 5, 6, and 7 L/min for 100 bpm, were 74.8 degrees and 81.6 degrees, respectively, whereas their design opening angles were 85 degrees and 90 degrees. Pressure drops across the CM and the ATS were consistently higher than those of the On-X and the SJM HP. Closing volumes for all the valves were below 8% for a heart rate of 70 bpm. This in vitro investigation yielded the following conclusions: The ATS and On-X valves are not able to open fully in the mitral position, but this does not impair their normal function; both a larger orifice diameter and a large opening angle can decrease the pressure drop; in general, the On-X valve achieves its design goals in this experiment (i.e., it produces a lower pressure drop and lower closing volume by virtue of its large orifice and high-profile design); however, the hinge flow in the non-fully open state should be investigated further.

Hemodynamic performance of small-size bileaflet valves: pressure drop and laser Doppler anemometry study comparison of three prostheses

Laser Doppler anemometry (LDA) is a single-point technique which is unparalleled to detect accurately the local properties of the velocity field in a turbulent flow, such as that generated by a prosthetic heart valve (PHV). We propose a correlation between the structure of the flow field in three 19 mm bileaflet PHVs (Sorin Bicarbon, St. Jude Standard, St. Jude HP), investigated at peak systole (6 L/min cardiac output [CO]) with LDA, in kinematic and geometric similarity, and the global parameter of transvalvular pressure drop measured in both steady and pulsatile conditions. The pressure transducers of the same apparatus were used to characterize pressure drops at different flow rates whereas the steady-flow case was studied with a highly accurate tester built in our laboratory. The 2 St. Jude models rank according to their internal orifice diameter (ID) with the standard model (with a smaller ID) providing higher pressure drops for each flow rate. Sorin Bicarbon, due to its leaflet geometry, generates a more complex flow field with respect to the 2 St. Jude flat-leaflet models and shows improved hemodynamical behavior in pulsatile conditions with respect to the stationary case due to differences in pressure recovery. This study can provide insights into a PHV's local flow structure and global hemodynamical parameters.

Left ventricular mass regression after implantation of St. Jude Medical cardiac valves in small aortic roots

In this study, we analyzed the extent of regression of left ventricular hypertrophy in patients who received small St. Jude Medical (SJM) aortic valves and compared the results with those of another group receiving larger valves. Eighty-eight patients received either 19 or 21 mm valves (Group 1, 25 patients) or either 23 or 25 mm valves (Group 2, 53 patients). Echocardiographic studies were done before the operation and 5 years postoperatively. At follow-up a significant reduction in the left ventricular mass was found for both patient groups (p < 0.0001). Doppler echocardiography derived pressure gradients for both groups were obtained during the follow-up period. As expected, the patients in Group 1 had higher peak pressure gradients than did those in Group 2. However, there was no significant difference between the 2 groups or any significant correlations between peak pressure gradients and body surface area (BSA). Actuarial survival was 84.7% at 15 years for Group 1 and 85.9% at 17 years for Group 2. Actuarial freedom from valve related events was 91.4% at 15 years for Group 1 and 82.7% at 17 years for Group 2. There was no significant difference in survival or valve related event free curves between the 2 groups. After implantations of SJM valves in small aortic roots, significant left ventricular mass regression was obtained, and the results were comparable to those for valves of other sizes. The long-term performance of aortic valve replacement with small valves was satisfactory as judged by improvement in the functional class of patients and survival statistics, the durability of the prosthesis, and valve related morbidity comparable to that of valves of other sizes.