Zsolt L. Nagy

Hydrodynamic function of the second-generation mitroflow pericardial bioprosthesis

BACKGROUND The hydrodynamic function of the smaller size Mitroflow Synergy stented pericardial bioprostheses has been studied in an in vitro fresh tissue aortic root model and compared with previous studies of free-sewn bioprostheses. METHODS Three valves of each of the sizes 19, 21, and 23 mm were sutured into fresh tissue aortic roots and tested in a pulsatile flow simulator using two different ventricular input impedance conditions. A high-speed camera was used to study the leaflet opening and closing configurations. Mean pressure difference as a function of root mean square forward flow, effective orifice area, regurgitant volumes, and total energy loss across the valves was measured. RESULTS Mean pressure difference with respect to root mean square forward flow decreased as the valve size increased. Thus effective orifice area increased as the valve size increased. The open leaflet configuration images showed that all three sizes of Mitroflow valves had a large circular orifice with minimal open leaflet deformation. All valves closed competently with no visible leakage and no closed regurgitant volume. The Mitroflow valves showed better effective orifice areas compared with previously tested frame-mounted porcine bioprostheses but lower effective orifice areas compared with porcine stentless bioprostheses; however, the open leaflet bending deformation was better than for any of the previously tested bioprosthetic valves. CONCLUSIONS The hydrodynamic function of the Mitroflow Synergy stented pericardial bioprosthesis shows potential for good in vivo hemodynamic performance. The good hemodynamic performance combined with relative ease of implantation technique makes the pericardial valve a good valve in the aortic position, particularly in older patients with small annuli.

The effect of sizing on the in vitro hydrodynamic characteristics and leaflet motion of the toronto SPV* stentless valve ☆ ☆☆ ★ ★★

OBJECTIVES We established an in vitro model to investigate the effects of valve sizing on the hemodynamic characteristics and leaflet motion of the Toronto SPV valve (St Jude Medical, Inc, St Paul, Minn). METHODS Nine valves were first implanted in fresh porcine aortic roots and then retested in glutaraldehyde-treated porcine aortic roots. Three valves were 1- to 2-mm oversized, 3 were 1- to 2-mm undersized, and there were 3 size-for-size implantations. The elasticities of the aortic roots and the composite roots were measured in the pressure range between 0 and 120 mm Hg, and the composite roots were then tested in a pulsatile flow simulator. The transvalvular gradient and regurgitation were measured and the effective orifice area and performance index were calculated for each root. Leaflet motion was recorded on videotape. RESULTS The external diameter of the fresh root increased by 35% as the hydrostatic pressure rose from 0 to 120 mm Hg, as compared with 11% for the glutaraldehyde-treated root. Valve implantation in the fresh root reduced the distensibility to 22% but did not change distensibility in the glutaraldehyde-treated root. The effective orifice area was dependent on the valve size, with the transvalvular gradient decreasing as the valve size increased. For the same size of valve the hydrodynamic parameters were slightly better if the valve was undersized by 1 mm. A significant difference in favor of the undersized valves was found in open-leaflet bending deformation. CONCLUSION Leaflet motion of the stentless porcine aortic valve in vitro is improved if the valve is slightly undersized, and this may be beneficial to the long-term durability of the prosthesis.

The Quantification of Pulmonary Valve Haemodynamics Using MRI

The optimum slice location within the pulmonary root to quantify pulmonary valve haemodynamics was examined using magnetic resonance (MR) phase velocity mapping. MRI was carried out on 15 patients with congenital aortic valve disease. Although the patients had aortic valve disease, all measurements were made on the pulmonary valve. Systolic (QSYS) and diastolic (QDIAS) blood flow volume and cardiac index (CI) were determined at four pulmonary artery locations. The change in diastolic flow volume relative to slice 1, closest to the pulmonary valve, was also calculated. For a change in axial position of 1.5 cm, i.e. from 0.5 to 2 cm from the annulus, there was a change in diastolic flow volume of 4.4 ml. There was a significant increase in the mean diastolic flow from 3.4 to 7.7 ml (p = 0.01) between slice positions 0.5 and 2 cm. However, there was no significant change in CI, 3.4–3.7 l/min/m2 (p = 0.14) over the same distance. We believe that two factors are responsible for these results. The first is that of compliance, whose effects can be minimized by placing the MR slice close to the valve, however, this will not account for the second factor, being that of valve motion, and hence diastolic pulmonary valve flow or regurgitant volume will be underestimated. The degree of underestimation may only be important at mild and moderate levels of regurgitation or if changes in regurgitation are to be temporally measured.

The effect of sizing on the hydrodynamic parameters of the medtronic freestyle valve in vitro

BACKGROUND An in vitro model has been established to investigate the effect of sizing on the hydrodynamic characteristics and leaflet motion of the Medtronic Freestyle valve. METHODS The valves were tested in fresh porcine aortic roots. Two or three different sizes of valves were implanted in the same aortic root one after the other. The compliance of the fresh aortic and the composite roots was measured in the pressure range of 0 to 120 mm Hg, and the composite roots were then tested in a pulsatile flow simulator. The transvalvular gradient and degree of regurgitation were measured and the effective orifice area and performance index were calculated. Leaflet motion was recorded on video. RESULTS The fresh aortic roots dilated by average 39.4% as the hydrostatic pressure rose from 0 to 120 mm Hg. Implantation of the Medtronic Freestyle valve did not change the distensibility of the aortic root significantly. The sizing protocol did not affect significantly the hydrodynamic performance. However, a significantly lower open leaflet bending deformation was found in the undersized valves. Regurgitation was found only at 2-mm undersized valves. CONCLUSIONS Leaflet motion of the Medtronic Freestyle valve in vitro was best if 1 mm undersized, and this may be beneficial to long-term durability.

The influence of size mismatch on the hemodynamic performance of the pulmonary autograft in vitro

OBJECTIVES We established an in vitro model to investigate the effect of size mismatch between the aortic and pulmonary root on the hydrodynamic performance and leaflet motion of the pulmonary autograft. METHODS Ten fresh porcine pulmonary roots (annulus diameter: 19-25 mm) were tested in a pulsatile flow simulator. The autografts then were implanted in fresh porcine aortic roots (annulus diameter: 19-30 mm) and retested in the flow simulator. Three roots were oversized by 21-39%, three were undersized by 32-45% and there were four size for size implantations. The external diameter of the roots and autografts was measured at the sinotubular junction at hydrostatic pressures of 0 - 120 mmHg. The transvalvular gradient and regurgitation were also measured and the effective orifice area was calculated. The leaflet motion was recorded on video. RESULTS The fresh pulmonary roots were more compliant than the fresh aortic roots (46 +/- 8.4% vs. 35 +/- 7.8% dilatation from 0 to 120 mmHg). The group of matching size autografts dilated by 43 +/- 4.9% in the same pressure range. The external diameter of the undersized autografts was 10 +/- 2.1% bigger than before implantation at 0 pressure and then the dilatation was 40 +/- 5.3% at 120 mmHg. The oversized implantation made the autografts 11 +/- 9.4% smaller in their relaxed state, but then they dilated by 65 +/- 11% as the pressure increased to 120 mmHg, resulting in a net dilatation of 54% over the original undilated state. The under or oversizing had little effect on the pressure gradient measured across the valves (5.6 +/- 2.57 mmHg before, 6.3 +/- 3.27 mmHg after implantation). Only the oversized valves showed significantly higher gradients than the native pulmonary valves. The effective orifice area of the undersized autografts was slightly bigger and the oversized autografts was slightly smaller after implantation, although the differences were not significant. The size mismatch did not cause regurgitation on the valves. The video images showed very low-open leaflet-bending deformation, both on the fresh pulmonary and the autograft valves. CONCLUSION Under or oversizing the pulmonary autograft up to 40% of the annulus diameter did not affect the hydrodynamic parameters significantly. The compliance of the autograft root was able to compensate for the size mismatch without adversely influencing the valve performance.

Repair of aortic atresia and hypoplastic left heart syndrome without using graft material

We present a modification of the Norwood stage 1 operation, where the neo-aorta was reconstructed without using graft material. After extensive mobilization of the descending aorta the ductus arteriosus was excised and an end-to-end anastomosis was created between the main pulmonary artery and the distal ductal-aortic junction. The proximal ascending aorta was anastomosed side-to-side to the neo-aorta. Finally either a direct side-to-side anastomosis was created or a 3.5-mm Gore-Tex graft was implanted between the innominate artery and the right pulmonary artery. The first three patients had a favourable outcome: echocardiography showed good ventricular function and acceptable saturation (85%) at the follow up.

Ross-műtét vagy mechanikus műbillentyű beültetés fiatalkori aorta vitiumos betegeknélr

UNLABELLED Clinical and echocardiographic data of young adults undergoing aortic valve replacement either by pulmonary autograft or mechanical prosthesis were analysed. Between 1995 and 2002 thirty-four consecutive patients (age 26.2 +/- 5.3 years) underwent aortic valve surgery by the authors (17 Ross procedures and 17 mechanical prostheses). Reasons for not doing a Ross procedure were size mismatch (3); anomalous coronaries (2); thin pulmonary sinuses (2); severe hypertension (2); poor LV function (2); active endocarditis (1); lack of suitable homograft (2) and the patients request (3). There was no early mortality detected, although all patients were followed up (64.4 +/- 26.8 months). Two late deaths occurred in the prosthetic valve group (1 sepsis secondary to endocarditis, 1 end-stage heart failure). During the follow-up time there were two cases of endocarditis and two anticoagulant-related complications in the mechanical valve group. In the Ross group, one patient required reoperation for early endocarditis secondary to an infected homograft. The only late complication after the Ross procedure was a minor pulmonary embolism. Echocardiography showed a competent autograft in all but one patient. LV end diastolic dimensions and wall thickness were significantly smaller in the autograft patients (p = 0.049 andp = 0.017, respectively). CONCLUSIONS Freedom from anticoagulation-related complications and unrestricted lifestyle as well as the more complete LV mass regression make the autograft a superior valve substitute in young adults; however it is not suitable for everyone.

Pulmonary valve quantification using MRI in patients with congenital aortic valve disease

The aim of the study was to determine whether pulmonary valve (PV) haemodynamics are affected by congenital aortic valve disease (CAVD). A large amount of retrograde to antegrade flow was seen in patients with a dilated MPA, which was also shown in the 3D velocity profiles. This would appear to suggest that PV haemodynamics downstream of the valve can be affected by CAVD. However, the normal cardiac index (CI), systolic and diastolic flow suggests that the PV is not compromised in patients with CAVD.