Hemodynamic characterization of the Sorin Mitroflow pericardial bioprosthesis at rest and exercise.
ABSTRACT Although the long-term clinical outcome after aortic valve replacement (AVR) with the Sorin Mitroflow pericardial bioprosthesis has been well described, few data are available with regards to hemodynamic performance. On the basis of its specialized design, with the pericardium mounted on the outside of the stent, the Mitroflow valve is considered to provide optimal opening and orifice areas.
Between February 2006 and April 2007, a total of 127 patients (66 females, 61 males; mean age 77.6 +/- 5.2 years) underwent AVR with the Mitroflow valve at the authors' institution. Echocardiography was performed at discharge in 91 patients, while a six-month follow up examination was conducted in 78 (including ergometer hemodynamics in 25 cases).
The mean systolic pressure gradient (MPG) ranged from 19.7 +/- 3.3 mmHg (size 19 valve) to 12.4 +/- 2.4 mmHg (size 27 valve), and the mean effective orifice area (EOA) from 0.96 +/- 0.0 cm2 (size 19 valve) to 2.36 +/- 0.4 cm2 (size 27 valve). The incidence of mild-to-moderate and severe prosthesis-patient mismatch (PPM) was 33% and 10% at the six-month follow up. During exercise (25 W-100 W), the MPG increased from 17.1 +/- 3.6 mmHg to 23.6 mmHg in valve sizes 19 to 21, and from 12.2 +/- 3.6 mmHg to 15.9 +/- 2.5 mmHg in valve sizes 23 to 27. The effective orifice fraction (EOF = EOA/annulus area) was 38 +/- 7%.
The Mitroflow valve exhibits an adequate MPG and EOA, as might be expected for a pericardial bioprosthesis. Of note, the gradient increase during exercise was low, especially for the larger valve sizes. Due to its special design, the Mitroflow prosthesis shows a large opening, as demonstrated by the high EOF. These data relating to the EOA of all prosthesis sizes may help surgeons to select the minimum prosthesis size in order to prevent PPM.
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ABSTRACT: The hemodynamics in proximity to stented aortic bioprostheses still differ from that under physiological conditions. This may prevent desired cardiac remodeling and promote aortic diseases. Further improvements in prosthetic technology require an accurate survey of the flow conditions on the prosthetic level and in the ascending aorta. Cardiovascular magnetic resonance (CMR) may have the potential to provide more information by determining the prosthetic orifice area and visualizing the intravascular flow dynamics. We tested the feasibility to better characterize the hemodynamics of various stented bioprostheses in a pulsatile flow phantom by using CMR. The custom-made model consisting of a commercially available pump generating pulsatile flow, a tube system filled with a glycerin-water mixture, and a handcrafted bulbar-shaped cylinder holding the bioprostheses and simulating the aortic root, was located in a clinical 1.5T CMR system. In this study, 10 stented aortic bioprostheses were investigated (Perimount® 21, 23; Mitroflow® 19, 25; Hancock® 21, 23, 25; Mosaic® 21; Epic Supra® 21, 23). The prosthetic orifice area was visualized using steady-state free-precession cine imaging (spatial/temporal resolution 1.3×1.3×5 mm³/29 ms), quantified by manual planimetry and compared with published transthoracic echocardiographic data. Time-resolved three-dimensional phase-contrast flow mapping (1.8×1.8×3 mm³/45 ms) was applied to analyze the transprosthetic flow pattern. Visualization of the prosthetic orifice area and the transprosthetic flow pattern was feasible in all prostheses. All orifice areas obtained by CMR in vitro were within one standard deviation of the mean of the published reference values obtained by echocardiography in vivo. Turbulent flow with vortex formation occurred both in proximity to the prosthesis and on the 'ascending aortic' level. Larger prosthetic sizes led to decreased flow velocities, but not mandatorily to less turbulences. CMR allowed for a detailed interrogation of the fluid dynamics of various heart valve bioprostheses in a pulsatile flow model. It is an attractive tool to define proprietary reference values of the orifice area under standardized conditions and provides novel information regarding the flow pattern in proximity to the prosthesis.European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery 02/2011; 40(3):736-42. · 2.40 Impact Factor
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ABSTRACT: Heated debates revolve around the hemodynamic performance of stented aortic tissue valves. Because the opening area strongly influences the generation of a pressure gradient over the prosthesis, and the outer diameter determines which valve actually fits into the aortic root, it would seem logical that the valve with the greatest opening area in relation to its outer diameter should allow the best hemodynamic performance. Interestingly, neither of these 2 parameters is reflected by the manufacturing companies' size labels or suggested sizing strategies. In addition, it is known that valves with the same size label from different companies may differ significantly in their actual dimension (outer diameter). Finally, the manufacturer-suggested sizing strategies differ so much that expected differences from valve design may get lost because of differences in sizing. These size and sizing differences and the lack of information on the geometric opening area complicate true hemodynamic comparisons significantly. Furthermore, some fluid dynamic considerations regarding the determination of opening area by echocardiography (the effective orifice area) introduce additional obscuring factors in the attempt to compare hemodynamic performance data of different stented tissue valves. We analyzed the true dimensions of different tissue prostheses and the manufacturer-suggested sizing strategies in relation to published effective orifice areas. We have demonstrated how sizing and implantation strategy have much greater impact on postoperative valve hemodynamics than valve brand or type. In addition, our findings may explain the different opinions regarding valve hemodynamics of different tissue valves.The Journal of thoracic and cardiovascular surgery 06/2011; 142(5):1180-7. · 3.41 Impact Factor
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ABSTRACT: Since blood flow impairment by aortic valve prosthesis is characteristically dynamic, this dynamic component is best and thoroughly appreciated by exercise Doppler echocardiography. We sought to determine the haemodynamics of a new pericardial aortic bioprosthesis (Trifecta™, St Jude Medical, MN, USA; T-AVB) at rest and during exercise and a 10-min recovery period in comparison with alternative aortic valve prostheses, e.g. Ross operation (RO), stentless aortic valve (Medtronic Freestyle prosthesis, MF-AVB) and a healthy control group (CO). Haemodynamics at rest and during supine exercise stress testing and a 10-min recovery period were evaluated in 32 patients (mean age: 70.8 ± 6.7 years) with transcatheter aortic valve replacement (T-AVR) (mean follow-up: 5 ± 2 months), 49 with RO (mean age: 43.5 ± 13.7 years), 39 with an MF-AVB (mean age: 64.6 ± 9.4 years) and 26 healthy patients (mean age: 39 ± 9 years). Measurements included mean outflow tract gradient (δpmean, mmHg), effective orifice area index (EOAI, cm(2)/m(2)) and valvular resistance (vR, dyn s cm(-5)). Mean body surface area for T-AVB was 1.93 ± 0.24 m(2) (median 1.97 m(2)). Mean δpmean at rest was 7.2 ± 3.4 mmHg, mean EOAI 0.86 ± 0.23 cm(2)/m(2) and mean vR 50.7 ± 23.2 dyn s cm(-5). Supine stress testing did increase the mean EOAI to 0.98 ± 0.27 cm(2)/m(2), the mean vR to 62.6 ± 25.3 dyn s cm(-5) and the mean δpmean to 10.21 ± 4.7 mmHg, respectively (P < 0.05 for all comparisons). During the post-exercise recovery period, δpmean, EOAI and vR showed a prompt normalization within 5 min of cessation of exercise. At all the three measurement points, T-AVR and MF-AVB revealed low gradients, satisfactory EOAI and low vR. Compared with the RO and a healthy control group, both groups showed significantly inferior performance throughout the exercise and post-exercise study protocol (P < 0.05). In comparison with T-AVB, patients with an MF-AVB only showed significant inferior performance throughout series with respect to a higher vR, indicating a smaller increase in the EOAI during exercise. During the 10-min post-exercise period, T-AVB recovered significantly earlier than MF-AVB. When comparing two different types of aortic valve bioprostheses with a gold standard group (RO) and a healthy population, both aortic valve bioprostheses perform inferior but reveal promising haemodynamics during exercise. During post-exercise haemodynamic recovery, only the T-AVB revealed a nearly physiological recovery pattern compared with the RO and a healthy control group.European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery 07/2013; · 2.40 Impact Factor