Stentless Aortic Valve Research Articles

A Novel Stentless Mitral Valve

Stentless mitral valves have found little clinical utility to date due to difficulty in insertion. A new design for a stentless mitral valve, a modification of an existing aortic stentless prosthesis, is described. The new design mimics the native mitral physiology, and its insertion is easier than with existing stentless mitral valves. Commercially available stentless aortic valves were inserted into 2 pigs. The valves were modified so that the commissural posts were restrained. The valves were partially recessed into the left ventricular cavity, secured to the annulus, and anchored to the native papillary muscles. Both pigs were weaned from bypass successfully, and both valves functioned normally with trace regurgitation noted on echocardiography. This design affords the benefit of the reapproximation of native physiology. Preservation of papillary-annular continuity should allow maximal left ventricular function. Lack of a stent should allow avoidance of long-term anticoagulation.

Autografts, homografts, and xenografts: overview on stentless aortic valve surgery

Stentless valves, either human (autografts, homografts) or animal (porcine xenografts), were historically among the first substitutes to be used to replace the diseased aortic valve. Forty years after those pioneering days and 15 years after revival of such valves, stentless grafts have become a mainstay in aortic surgery. Although limitations associated with the use of autografts, homografts and xenografts remain, stentless valves have profoundly improved quality of life after aortic valve/root replacement. In addition, stentless surgery has greatly advanced the understanding of aortic root anatomy, physiology and pathology among surgeons.

Technique for implant of the stentless aortic valve Freedom Solo

In this presentation we provide a summary of aortic valve replacement with a supra-annular stentless aortic valve, the Freedom Solo prosthesis. Stentless valves were designed to provide more physiological flow and lower transvalvular gradient, which is offered by the novel design of the valve and by its implantation technique. The supra-annular stentless aortic valve implantation is demonstrated with a special emphasis on its surgical technique peculiarities.

The risk of thrombo-embolic events after stentless aortic valve replacement is not valve-related but patient-related

Introduction: This study analyses the incidence of thromboembolism (TE) during follow-up after aortic valve replacement using stentless valves.

Physiological function of stentless aortic valves is altered by trimming and removal of aortic wall components

Various techniques of stentless aortic valve implantation with or without wall components exist. We investigated the in-vitro performance of stentless valves without or with aortic wall removal mimicking root versus subcoronary implantation. Glutaraldehyde-preserved stentless aortic valves (gpSVG), cryo-preserved human homografts (cpHG), cryo-preserved xenografts (cpXG), and fresh xenografts (fXG) were used. Valves were mounted as full roots or trimmed in a mock circuit. Mean transvalvular gradient (MTVG, mmHg) was measured. Distensibility was quantified using post-systolic backflow volume (BV, ml) - after valve closure. Function was visualized by means of a high-speed camera. Glutaraldehyde-preserved valves exhibited higher MTVG than cryo-preserved or fresh substitutes. After trimming, cpHG, cpXG, and fXG demonstrated marked reduction of MTVG (cpHG: 7.6-5.2 mmHg; cpXG: 6.7-4.9 mmHg; fXG: 8.4-5.2 mmHg). In contrast, after trimming gpSVG exhibited a significant increase of MTVG (7.1-9.2 mmHg). BV remained constant. Visualization indicated maintained distension of all valves and types of all sizes after trimming. In fresh and cryo-preserved grafts, aortic wall trimming resulted in significantly improved systolic performance while glutaraldehyde-preserved stentless valves demonstrated systolic impairment after wall resection. Subcoronary implantation of fresh or cryo-preserved aortic valves may therefore be preferred. In contrast, glutaraldehyde-preserved valves are dependent on wall suspension and may therefore be implanted as a root.

A Repositionable Valved Stent for Endovascular Treatment of Deteriorated Bioprostheses

We report our animal experience of endovascular valve replacement (VR) of failed bioprosthesis (BP) using an original delivery catheter allowing repositioning of the valved stent (VS). Among the different devices designed for percutaneous VR, none has the potential for repositioning of a fully deployed VS. Five sheep underwent, on beating heart, tricuspid VR with a stented BP. Prolapse of 1 leaflet was induced by tearing. For the endovascular tricuspid VR, we used a VS constructed with a nitinol self-expandable stent and a porcine stentless aortic valve. We also used an original delivery catheter, allowing repositioning of the VS through a compression or relaxation mechanism of the stent. Epicardial echocardiography and right ventriculography showed severe tricuspid regurgitation, with a regurgitant jet extending to the inferior vena cava. After surgical exposure to the infrarenal inferior vena cava, the VS was successfully implanted inside the failed BP in all cases. Repositioning of the fully deployed VS was always possible. Echocardiographic and macroscopic studies revealed adequate VS positioning, excellent leaflet opening, and absence of any intraprosthetic or periprosthetic leak. Endovascular VR was easily performed in sheep with failed BP in the tricuspid position. The novel delivery catheter allowed adequate repositioning of our fully deployed VS before its definitive release. One may anticipate that the safety improvement conferred by this new technology will certainly favor the development of percutaneous VR in clinical practice.

Outcomes with Toronto stentless porcine aortic valve: the Australian experience

The purpose of this study is to describe the Australian experience with TSPV in the aortic position in 543 patients followed for up to 8 years. Prospectively collected data were reviewed. The average age was 73.5 years, with 74.4% older than 70 years. Eighty-five percent of valves were calcified and 79.5% stenotic. Most valves implanted (79.3%) were sizes 25, 27, or 29 mm. Concomitant coronary bypass was performed in 45.3% of patients. Total cumulative follow-up for the 543 patients was 2131 patient years. At 6 years, 82.1% and at 8 years, 76.3% were in New York Heart Association class I, 55% had no aortic insufficiency. The average mean systolic gradient for all valves at 6 years was 7.4 mmHg. The effective orifice area varied from 1.7 cm(2) (23-mm valve) to 1.96 cm(2) (29-mm valve). Actuarial survival at 8 years was 79.3%. Freedom from valve-related deaths was 93.2%. There was one instance of primary tissue valve failure during follow-up, with 93.3% freedom from explant. The early hemodynamic benefits of the TSPV are well maintained during more than 8 years of follow-up, without evident significant valvular dysfunction. Longer follow-up time is required to validate durability.

Implantation of a Modified Freestyle Valve With a Single Inflow Suture Line: Technical Patterns and Advantages

Subcoronary implantation of stentless valves may be a surgical challenge in the small aortic root. In addition, calcifications of coronary ostia may interfere with the procedure. We present a technique to trim a Freestyle stentlesss root (Medtronic Inc, Minneapolis, MN) and facilitate implantation with a single inflow suture line.

Late iatrogenic coronary stenosis after selective intraoperative antegrade myocardial protection for stentless aortic valve replacement

Local injuries to the arterial wall induce periadventitial angiogenesis stimulating intimal thickening. Injuries of the arterial wall disrupt normal vascular hemostasis, promoting intimal hyperplasia. We report the case of a 59-year-old man with concomitant severe stenosis of the proximal iatrogenic left main trunk and right coronary artery ostium from selective intraoperative antegrade myocardial protection 10 years after aortic valve replacement (AVR) for aortic stenosis.

Impact of Stentless Aortic Valves on Left Ventricular Function and Hypertrophy: Current Best Available Evidence

Past four decades have seen a gradual evolution in aortic valve replacement surgery. The ideal valve substitute should combine central flow, low transvalvular gradient, low thrombogenicity, durability, easy availability, resistance to infection, freedom from anticoagulation, and easy implantability. Although there are several types of valves available to replace the diseased aortic valve-autograft, allograft, xenograft, mechanical, and bioprosthetic valves-none is ideal. On one end of the spectrum is the pulmonary autograft, which comes closest to achieving these goals, but creates a double valve procedure for single valve disease, while on the other end are the mechanical valves and stented tissue valves, which allow easy "off the shelf" availability as well as easy implantability but are limited by the potential drawback of causing intrinsic obstruction to some extent because of the space occupied by the stent and sewing ring. Stentless xenograft aortic valves have been developed as a compromise between these ends of the valve spectrum. Stentless aortic valves have been reported to provide more physiologic hemodynamic behavior and cause more timely and thorough regression of ventricular hypertrophy. This review article attempts to evaluate current best available evidence from randomized controlled trials to assess the impact of stentless aortic valves on left ventricular function and hypertrophy.

Stentless bioprostheses improve postoperative coronary flow more than stented prostheses after valve replacement for aortic stenosis

In some randomized studies, stentless aortic valves have demonstrated hemodynamic advantages in comparison with stented prostheses. The effect of more physiologic flow dynamics on coronary artery flow has not been investigated yet. This study compares coronary perfusion after aortic valve replacement with stented or stentless porcine bioprostheses in a prospective randomized study. A total of 24 patients (73 +/- 6 years) referred for treatment of aortic stenosis were randomized to aortic valve replacement with stented (Medtronic Mosaic; (Medtronic Inc, Minneapolis, Minn) or stentless (Medtronic Freestyle; Medtronic Inc) prostheses. Coronary flow was measured by means of magnetic resonance imaging preoperatively, 5 days after the operation, and 6 months postoperatively, then with evaluation of coronary flow reserve. Echocardiography was performed to quantify transvalvular gradients and left ventricular mass regression. Coronary flow increased in both groups significantly (P < .001) after aortic valve replacement. This increase was higher in the stentless group compared with that seen in the stented group (343 +/- 137 vs 221 +/- 66 mL/min). Also, coronary flow reserve was higher for stentless valves (3.4 +/- 0.3 for stentless valves and 2.3 +/- 0.1 for stented valves). Mean pressure gradients for Freestyle valves were lower (10 +/- 4 and 8 +/- 3 mm Hg, respectively, vs 19 +/- 6 postoperatively and 15 +/- 4 mm Hg at follow-up for Mosaic valves, P < .05). Left ventricular mass regression was similar in both groups. Normalization of coronary artery flow after aortic valve replacement for aortic stenosis was more pronounced for stentless valves compared with stented valves. The fact that the stentless design also demonstrated a superior hemodynamic performance with lower pressure gradients might be explained by the design being closer to physiologic anatomy and thus the presence of lower turbulence levels in the sinuses of Valsalva.

Reduced distensibility of glutaraldehyde preserved stentless aortic valves impairs physiological function

Objectives: Physiological function of stentless aortic valve substitutes requires maintained distensibility of the cusps and sinuses. However, current glutaraldehyde-preservation techniques result in a marked increase of stiffness of valve tissue. In contrast, cryopreservation is considered to maintain physiological tissue pliability. The hemodynamic consequences are not yet fully elucidated.

Seven years of aortic valve replacement with stentless bioprostheses

Purpose: Due to the avoidance of an anticoagulation therapy and the hemodynamic advantages of stentless aortic valve bioprostheses, emotional and physical benefits are to be expected.

Normal coronary flow reserve after stentless aortic valve replacement – results from a prospective, randomized study

Introduction: Coronary perfusion is impaired in patients with aortic stenosis. Valve replacement (AVR) leads to improvement but not complete restoration. The following study investigates coronary flow and flow reserve in patients undergoing biological valve replacement with stentless or stented porcine prostheses in a prospective, randomized study.

Systolic hemodynamic properties of stentless aortic valves are determined by their flexible parts rather than annulus size

Systolic hemodynamic properties of stentless aortic valves are determined by their flexible parts rather than annulus size

Stentless Aortic Valves are Hemodynamically Superior to Stented Valves During Mid-Term Follow-Up: A Large Retrospective Study

Several studies have compared left venticular mass (LVM) regression and hemodynamic data for stentless versus stented aortic bioprostheses with conflicting results. The major limitations of these studies are their small sample size and short-term follow-up. We therefore compared midterm LVM regression, hemodynamic data, and survival in a large population of tissue aortic valve replacement (AVR) patients. All patients undergoing tissue AVR at our institution between 1998 and 2001 were included (n = 737). Patients were divided into two groups according to type of bioprosthetic implanted: stentless patients (total n = 310) (Toronto SPV [St Jude Medical, St Paul, MN], n = 146 and Freestyle [Medtronic, Minneapolis, MN], n = 164) and stented patients (total n = 427) (Perimount [Edwards Life Sciences Inc, Irvine, CA], n = 291 and Mosaic [Medtronic], n = 136). The two groups of patients had similar preoperative transvalvular gradients and LVM index (130 +/- 47 vs 130 +/- 42 g/m2 for stentless versus stented valves, respectively). Predischarge echos revealed that stentless patients had significantly lower mean transvalvular gradients (11 +/- 5 vs 15 +/- 6 mm Hg, p < 0.001) and larger effective orifice areas (1.32 +/- 0.52 vs 1.22 +/- 0.48 cm2, p = 0.01). Follow-up echocardiograms were obtained in 99% of surviving patients 28 +/- 22 (range, 0-79) months postoperatively. Stentless patients had significantly lower LVM index during follow-up (100 +/- 32 vs 107 +/- 32 g/m2, p = 0.005) and stentless valves were an independent predictor of LVM regression. Furthermore, a higher proportion of stented patients had residual LV hypertrophy during follow-up (28% vs 18%, p = 0.001). Stentless valves were associated with improved midterm survival by univariate analysis, but not by multivariable analysis. Midterm follow-up in a large number of patients reveals that stentless bioprostheses are hemodynamically superior to stented valves.

Stability of an artificially seeded endothelial cell layer on aortic bioprostheses in a heterotopic sheep model

Introduction: The stability of an endothelial cell (EC) layer established on stentless aortic bioprostheses was evaluated under in-vivo conditions in a sheep model. Methods: EC and fibroblasts were harvested from the external jugular vein of seven sheep. After fluorescence labelling (PKH-26), the cells were seeded onto pretreated (citric acid) stentless aortic valves (Freestyle, Medtronic). Three unseeded prostheses served as controls. The valves were implanted into the descending aorta. Using an aorto-left atrial shunt, systolic/diastolic movements of the leaflets were achieved and documented by direct intraoperative sonography. Postoperatively, the animals received no anticoagulative therapy. After three months, the chests were reopened and the valves were explanted. Specimen for immunohistochemical staining and scanning electron microscopy (SEM) were taken prior to implantation and after explantation. Results: All animals survived surgery. One animal of the study group died on the first postoperative day. A still confluent EC layer of labelled cells covered the the surface of this valve. The other valves were explanted after three months. Control group: Neointimal covering of the first 0.5cm of the prostheses. Structural degeneration with evident leaflet retraction and thrombus formation was found in all sinuses. No EC layer was seen on the cusps. Study group: Degeneration was similar. In contrast, leaflets and sinuses were covered with EC as was proven with immunohistochemical stainings and by SEM. No thrombus was found in the sinuses of these valves. The EC layer established on stentless biological valves remained stable and seemed to suppress thrombus formation thus increasing biocompatibility.

Impact of full root implantation of stentless aortic valves on clinical outcome: A propensity score analysis

Purpose: We assessed the effect of full root implantation technique of the Freestyle stentless bioprosthesis on clinical outcome, while adjusting for patient and disease characteristics by a propensity score.

Up to 16 years follow-up of aortic valve reconstruction with pericardium: a stentless readily available cheap valve?☆

There is lack of information regarding the long-term behavior of aortic valve reconstruction with pericardium (AoR). A 16-year follow-up is reported here. Between 1988 and 1995, 92 consecutive patients had AoR with bovine (Group I, n=27) or glutaraldehyde-treated autologous pericardium (Group II, n=65). The mean age was 30 years (range 12-68). There were 65% males, 92% in sinus rhythm, 84% had rheumatic etiology and 36% had 'other valve' surgery. Mitral valve replacement with a mechanical prosthesis is a contraindication to the operation. Hospital mortality was 2%. The reconstructed aortic valve performed well with excellent hemodynamics. The mean follow-up interval was 10.5+/-4 years, range 9-16 years (longer for group I,12 versus 10 years) with 4% late deaths and seven patients lost to follow-up. Survival rate was 85+/-4%. There were no episodes of thromboembolism. Freedom from reoperation for the whole group was 68+/-5% at 10 years and 47+/-6% at 16 years. For group I, it was 68+/-9% at 10 years and 48+/-10% at 16 years, while for group II it was 72+/-6 and 45+/-8% at 10 and 15 years, respectively. Excluding endocarditis (one in group I and seven in group II) and 'other' reasons for reoperation (two in group I and three in group II), the freedom from structural valve degeneration (SVD) at 10 and 16 years was 78+/-1 and 55+/-10% for group I. For group II, it was 80+/-5% at 10 years and 58+/-9% at 15 years. The mean interval at which the valve degenerated was 8.8 years+/-3.6 and did not differ between the two groups. AoR is feasible with good hemodynamics, low mortality and thromboembolic rate. Its behavior at 10 years is comparable to that of stentless aortic valve bioprosthesis. It can be performed with either xenopericardium or glutaraldehyde-treated autologous pericardium, but the latter has the advantage of being inexpensive and readily available.

Aortic Leaflet Replacement With the New 3F Stentless Aortic Bioprosthesis

Purpose Clinical trials with the new 3F stentless aortic bioprosthesis began October 2001, and as one of the first centers to implant this prosthesis in humans, we would like to present our experiences with this new device. Description The 3F aortic bioprosthesis is a stentless biological heart valve fabricated from three equal leaflets of equine pericardium, assembled in a tubular shape, and implanted in the native aortic root to replace the patient's diseased aortic leaflets. Between January 2002 and August 2002, 24 3F aortic bioprostheses were implanted at our institution. Effective orifice area, mean gradients, and ejection fraction were evaluated by echocardiography at discharge and at 12-month follow-ups after surgery. Evaluation At 12-month follow-ups, the 3F bioprosthesis showed a good hemodynamic performance with a significant drop of mean gradients to 10.3 mm Hg, a mean effective orifice area of 1.7 cm 2, and a mean ejection fraction of 61.5%. Conclusions The clinical performance of the new 3F aortic bioprosthesis is comparable with regular stentless aortic valves. However its unique design facilitates implantation.