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Purpose We investigated the effects of percutaneous valved stent implantation in the ascending aorta as an alternative treatment for aortic regurgitation in a canine model. Materials and methods A total of 16 healthy dogs weighing an average of 18.3 ± 2.1 kg were used for the establishment of animal models of chronic aortic regurgitation by percutaneous aortic valve perforation and balloon dilation. At 2 mo after successful model establishment, all experimental animals underwent valved stent implantation in the ascending aorta and then were followed up for 3 mo. Results Experimental models of chronic aortic regurgitation were successfully established in 10 dogs. Surviving dogs underwent successful valved stent implantation in the ascending aorta and were subsequently followed up for 3 mo. The level of instantaneous aortic regurgitation at 3-mo follow-up was significantly reduced compared with that before valved stent implantation (2.4 ± 0.9 versus 10.6 ± 2.1 mL/s, P < 0.05). The left ventricular ejection fraction was significantly increased (53.8 ± 4.2% versus 37.8 ± 3.7%, P < 0.05), and the left ventricular end-diastolic volume was also significantly reduced (30.3 ± 2.2 versus 40.1 ± 3.6 mL, P < 0.05). No paravalvular leak, stroke, atrioventricular block, or other complications occurred in dogs undergoing valved stent implantation. Conclusions Percutaneous valved stent implantation in the ascending aorta is feasible, effective, and safe as an alternative treatment for very high-risk aortic regurgitation in a canine model.

In recent years, some experimental and clinical studies on transcatheter aortic valve implantation (TAVI) have been conducted. TAVI is indicated in patients with calcified pure or predominant aortic stenosis. The risk of this technique is still high. Aortic valved stent implantation above the coronary ostia might avoid blocking the coronary ostia.Twenty healthy dogs were selected to establish a canine model of acute aortic valve rupture. The dogs were randomly divided into 2 groups: the rupture model group without any treatment and the valved stent group with percutaneous valved stent implantation above the coronary ostia. The 2 groups of animals were followed up for 3 months. Echocardiography and other tests were performed to assess aortic regurgitation and ventricular function. Acute aortic valve rupture models were successfully established in 16 of 20 dogs. In the rupture model group, the mean aortic regurgitation was 6.8 ± 1.9 ml/s; only 3 of 8 animals survived for 3 months. In the valved stent group, the mean aortic regurgitation was 7.0 ± 2.1 ml/s; valved stents were successfully implanted in 8 animals. Instant post-implantation anatomy showed that the stents were located appropriately. Seven dogs survived for 3 months.Percutaneous valved stent implantation above the coronary ostia is feasible and effective as a transitional treatment for acute aortic valve rupture.

Pulmonary regurgitation leads to progressive right ventricular dysfunction, susceptibility to arrhythmias, and sudden cardiac death. Percutaneous valve replacement has been developed in recent years, providing patients with an alternative option. Percutaneous pulmonary valve replacement has been recently introduced into clinical practice. The goal of this study was to evaluate the feasibility of percutaneous valve stent insertion to correct the pulmonary regurgitation in sheep using a cup-shaped valve stent.Pulmonary regurgitation was created by percutaneous cylindrical stent insertion in native pulmonary annulus of 8 sheep. One month after the initial procedure, the sheep with previous cylindrical stent implanted underwent the same implantation procedure of pulmonary valve stent. The valve stent consisted of a cup-shaped stent and pericardial valves. Hemodynamic assessments of the bioprosthetic pulmonary valve were obtained by echocardiography at immediately post-implant and at 2 months follow up.Successful transcatheter cylindrical stent insertion was performed in 7 sheep but failed in 1 sheep because the cylindrical stent was released to right ventricle outflow tract. After one month the 7 sheep with pulmonary regurgitation underwent valve stent implantation successfully. Echocardiography confirmed the stents were in desired position during the follow-up. No evidence of pulmonary valve insufficiency occurred in any animals. Echocardiography showed all heart function markers were normal.Percutaneous cylindrical stent insertion to induce significant pulmonary regurgitation in sheep was feasible, simple and reproducible. Percutaneous pulmonary valve stent implantation can reduce pulmonary regurgitation in a sheep model. Further development of animal model and clinical trials are warranted.

Valve replacement or repair is recommended in patients with tricuspid regurgitation when deterioration of their clinical status occurs as a consequence of right ventricular dysfunction. Percutaneous valve replacement was developed in recent years. To investigate the feasibility, effectiveness and long-term results of percutaneous tricuspid valve replacement, an experimental model with tricuspid regurgitation is needed. We developed a simple and reproducible percutaneous approach for the creation of tricuspid regurgitation in sheep.A specially designed grasping forceps were used to grasp chordae tendineae or the tricuspid valve leaflets through a catheter. Transcatheter creation of tricuspid regurgitation was performed on 7 healthy sheep. These sheep were followed up shortly after the procedure and at 6th month post-procedure with echocardiography. Additionally, all the sheep were sacrificed for anatomic evaluation at 6th month after the procedure.Creation of tricuspid regurgitation was successfully accomplished in all sheep. Necropsy confirmed that damage was done to the tricuspid valve apparatus in all animals (tearing of the anterior leaflet of the tricuspid valve in five animals and posterior leaflet of the tricuspid valve in two animals). At the six-month follow-up, there was no significant increase in the right ventricle dimension and ejection fraction measured by echocardiography. Autopsy examinations demonstrated the tearing of tricuspid valve leaflets.The creation of an animal model of tricuspid regurgitation via a percutaneous approach using forceps to sever one or more tricuspid leaflets is feasible and will allow investigation of devices designed replace the tricuspid valve via a percutaneous approach. Despite significant tricuspid regurgitation, the hemodynamics did not change during the follow-up period in this model.

Percutaneous aortic valve replacement is a promising strategy in the treatment of patients with aortic valve stenosis. And many kinds of valved stents have been implanted in selected patients worldwide. However, the clinical experience is still limited. We developed a W-model valved stent and evaluated the feasibility and safety of percutaneous implantation of the device in the native aortic valve position.A self expanding nitinol stent with W-model, containing porcine pericardium valves in its proximal part, was implanted in six sheep by means of a 14 French catheter through the right common iliac artery under guidance of fluoroscopy. During stent deployment the original aortic valve was pushed against the aortic wall by the self expanding force of the stent while the new valve was expanded. These sheep were followed up shortly after procedure with supra-aortic angiogram and left ventriculography. Additionally, one sheep was sacrificed after the procedure for anatomic evaluation.It was possible to replace the aortic valve in the beating heart in four sheep. The procedure failed in two sheep due to coronary orifice occlusion in one case and severe aortic valve regurgitation in the other case. One sheep was killed one hour after percutaneous aortic valve replacement for anatomic evaluation. There were no signs of damage of the aortic intima, or of obstruction of the coronary orifice.Percutaneous aortic valve replacement with a W-model valved stent in the beating heart is possible. Further studies are mandatory to assess safety and efficacy of this kind of valved stent in larger sample size and by longer follow-up period.

The purpose of this study was to determine the feasibility of transcatheter pulmonary valve replacement in sheep up to 6 months post procedure.Fresh sheep pericardium treated with a 0.6% glutaraldehyde solution for 36 hours was sutured to a valvular ring and then fixed onto a newly designed nitinol self-expandable stent. Thoracotomy was performed in sheep (23.5 +/- 3.1) kg under general anesthesia and the device was delivered into the native pulmonary valve of the sheep via the anterior wall of right ventricle by catheter and fooled for 6 months.One sheep died 4 months after the procedure due to in-stent thrombosis. Another 4 animals survived the 6-month observing period. Angiographic and hemodynamic measurements confirmed good positioning and function of the stents with a competent valve immediately post procedure and 6 months post the procedure in surviving animals.Implantation of the nitinol self-expandable stent in the pulmonary valve position by a transcatheter approach is feasible and good function of transcatheter implanted memory nitinol valved stents was shown after 6 months of implantation in sheep.

Background Various percutaneous valve replacement approaches have been reported in animals to replace the aortic and pulmonary valve. To broaden the indications of percutaneous approach to atrioventricular valves replacement, we developed a novel valved stent and evaluated the feasibility and safety of percutaneous implantation of the device in the tricuspid position. Materials and Methods A unidirectional semilunar valve of porcine pericardium was sutured to a valvular ring. Then the ring with pericardial valve was mounted on a double-edge nitinol stent to construct the tricuspid valved stent. Transcatheter tricuspid valved stent implantation was performed on 10 healthy sheep. These sheep were followed up shortly after procedure with echocardiography evaluation and 64-slice CT imaging examination during the periodical follow-up at 1 mo and at 6 mo post-implantation. Additionally, two sheep were sacrificed after the procedure for anatomic and histological evaluation one at 1 h and the other at 1 mo, respectively. Results Percutaneous valve implantation was successful in eight of 10 sheep. Two sheep died during the procedure due to migration of stent and fatal arrhythmia. The pressure of right heart did not significantly change after the procedure. Further echocardiography and imaging confirmed the stents were in desired position during the follow-up. The remaining six sheep with normal valvular and cardiac functionality survived for 6 mo after implantation. Conclusions The tricuspid stent with a valvular ring and pericardial valve can be implanted in tricuspid annulus percutaneous. The double-edge stent could substitute the native tricuspid valve chronically.

To explore the feasibility of autografting sinoatrial nodal cells heterotopic transplantation to construct an ectopia pacemaker for treating bradycardia.Sixteen healthy adult dogs were randomly divided into 2 equal groups: graft group and control group. The sinoatrial node (SAN) of the dogs in the graft group was harvested and digested into cell suspension in vitro, then injected to the autogenic right ventricular wall adjacent to heart apex. Commensurable culture medium was injected to the same position with the dogs in control group. Two week later, all dogs underwent transcatheter ablation of His bundle to create a complete heart block model and an electrophysiology study was carried out. In order to investigate the change of rhythm, isoproterenol and atropine was injected respectively to dogs of the graft group. Two weeks later the dogs were killed with their hearts taken out. Immunofluorescence histochemistry was used to investigate the survival of grafted cells and gap junction formed between grafted cells and ventricular myocytes. RESULTS The isolated cells from SAN retained active and beating. After ablation, the heart rate of the dogs of the graft group was (91 +/- 14) bpm, significantly higher than that of the control group, [(49 +/- 11) bpm, t = 6. 672, P0.01], and electrocardiography showed that these ventricular rhythms originated from the cell transplant sites. After the injection of isoproterenol the ventricular rate of the graft group was (118 +/- 15) bpm, significantly higher than that before the injection, (95 +/- 11) bpm, t = 3.491, P0.01), however, after the injection of atropine, the heart rate of the graft group was (101 +/- 17) bpm, not significantly different from that before the injection, [(95 +/- 11) bpm, t = 0.838, P0.05]. Immunofluorescence staining showed that the grafted autografting sinoatrial nodal cells all survived and that there was connexin-43 expression among the cells.Transplantation of autologous SAN cells into the right ventricular wall can boost the ventricular rhythm which is sensitive to isoproterenol but not to atropine. Grafted SAN cells can form gap junctions with adjacent myocytes.

Objective The goal of this study was to evaluate valvular functionality after transcatheter pulmonary valve replacement in sheep using a novel pulmonary valve stent. Methods Fresh porcine pericardium cross-linked with 0.6% glutaraldehyde was treated with L-glutamine to eliminate glutaraldehyde toxicity and sutured onto a valve ring before mounting on a nitinol stent to construct the pulmonary valve stent. Percutaneous femoral vein transcatheter pulmonary valve replacement was performed with the newly constructed valve stent. Pulmonary valve stents were implanted in 10 healthy sheep (6 males and 4 females) weighing an average of 25.7 ± 4.1 kg. Color Doppler echocardiography, 64-row computed tomography, and direct catheter examination were used to assess valvular function. Results Implantation was successful in 8 sheep. Shortly after surgery, all artificial valve stents exhibited normal open and close functionality and no stenosis or insufficiency. Heart rate was slightly elevated at this time, while all other hemodynamic parameters were normal. Six-month follow-up revealed no evidence of valve stent dislocation and normal valvular and cardiac functionality. There was no evidence of stent fracture. Repeated valve stent implantation was well tolerated as indicated by good valvular functionality 2 months postdelivery. Conclusion The novel pulmonary valve stent described herein can be delivered via percutaneous femoral vein transcatheter implantation and is highly efficacious at 6 months postdelivery. Furthermore, repeated valve stent replacement was successful.

Objective The purpose of this study was to investigate the feasibility and safety of pulmonary valve implantation via direct right ventricle puncture. Methods A standard thoracotomy and direct right ventricle puncture were performed in 8 healthy sheep to implant the pulmonary valve stents. Animals were followed up for 18 months. Results Three sheep died within the first 4 months after stent placement. The remaining 5 animals survived. After 18 months, examinations by color echocardiography, 64-slice computed tomography scan, and cardiac catheter showed an ideal position of each stent. The function of the pulmonary valves and hearts was not different compared with the preoperative conditions of the sheep. Anatomic examination revealed that the stent was covered by a layer of endothelial tissue with no stent fracture or valvular calcification. The histologic evaluation of the stent and surrounding tissue showed that the surface of the stent was smooth and covered by a complete layer of endothelial cells without obvious infiltration of inflammatory cells. The vascular wall was integrative without tear phenomenon in each layer of tissue. Conclusions These results show that pulmonary valve stents can be implanted via direct right ventricle puncture. Further studies evaluating xenograft valve material and the effect of implantation in vivo are needed.

Objective Percutaneous pulmonary valve replacement has been recently introduced into clinical practice. Patients with transcatheter pulmonary valve replacement will definitely face the problems of valve degeneration. In addition to surgical re-replacement of the degenerated bioprosthetic valves, we studied the replacement of degenerated bioprosthetic valves with transcatheter reimplantation of stent-mounted pulmonary valves. Methods Percutaneous pulmonary valve replacement was first performed in 6 sheep used a homemade valved stent. Two months after the initial procedure, the 6 sheep previously implanted with a valved stent underwent the same implantation procedure of a pulmonary valved stent. Hemodynamic assessment of the bioprosthetic pulmonary valve was obtained by echocardiography immediately post-implant and at 2 months follow-up. Results All 6 sheep had successful transcatheter stent-mounted pulmonary valve replacement in the first experiment. After 2 months, reimplantation was successful in 5 sheep but failed in 1 sheep because the first valved stent was pushed to the bifurcation of the pulmonary artery by the delivery sheath. Echocardiography confirmed the stents were in the desired position during the follow-up. The remaining 5 sheep with normal valvular and cardiac functionality survived for 3 months after implantation. Conclusion Transcatheter stent-mounted bioprosthetic pulmonary valve reimplantation is feasible in an animal model and more convenient than open chest reimplantation.