Animal model considerations to evaluate prosthetic tricuspid valve implants.

AIMS: Determining tricuspid valve comparative anatomy and appropriate animal models for preclinical evaluation of prosthetic tricuspid valve implants. METHODS AND RESULTS: We described and measured 81 heart specimens: 12 humans, 22 dogs, 21 sheep and 26 pigs. Tricuspid annulus circumference varied in humans from 109 to 149 mm, in pigs from 85 to 140 mm, and were ≤125 mm in dogs and sheep. Tricuspid leaflet demarcation in dogs is similar to humans, while in pigs and sheep we observed three distinct leaflets. In humans, sheep and pigs, papillary muscle positions are similar. In dogs they are all based on the septum. A moderator band was observed in all species, but was of consistent thickness only in sheep. CONCLUSIONS: Sheep and pigs are relevant animal models for evaluating prosthetic tricuspid valve implants. Seventy to 90 kg pigs have a tricuspid annulus size comparable to that in a dilated human heart, but due to possible fast growth leading to sizing incompatibilities, this represents a model for short-term study. Sheep are more stable in size for long term study, however, their tricuspid annulus size is the most similar to that in a healthy, non-dilated human heart. Dogs are not a suitable model due to their significantly different sub-valvular anatomy and smaller size.

Anticoagulation With an Inhibitor of Factors XIa and XIIa During Cardiopulmonary Bypass.

BACKGROUND: Exposure of blood to polyanionic artificial surfaces, for example, during cardiopulmonary bypass (CPB), induces a highly procoagulant condition requiring strong anticoagulation. Unfractionated heparin (UFH) is currently used during CPB but can lead to serious bleeding complications or development of a hypercoagulable state culminating in life-threatening thrombosis, highlighting the need for safer antithrombotics. Ixodes ricinus contact phase inhibitor (Ir-CPI) is a protein expressed by I. ricinus ticks, which specifically inhibits both factors XIIa and XIa, 2 factors contributing to thrombotic disease while playing a limited role in hemostasis. OBJECTIVES: This study assessed the antithrombotic activity of Ir-CPI in animal contact phase-initiated thrombosis models, including CPB. The safety of Ir-CPI also was evaluated. METHODS: The authors evaluated the antithrombotic activity of Ir-CPI by using in vitro catheter-induced clotting assays and rabbit experimental models of catheter occlusion and arteriovenous shunt. During CPB with cardiac surgery in sheep, the clinical applicability of Ir-CPI was investigated and its efficacy compared to that of UFH using an uncoated system suitable for adult therapy. Taking advantage of the similar hemostatic properties of pigs and humans, the authors performed pig liver bleeding assays to evaluate the safety of Ir-CPI. RESULTS: Ir-CPI prevented clotting in catheter and arteriovenous shunt rabbit models. During CPB, Ir-CPI was as efficient as UFH in preventing clot formation within the extracorporeal circuit and maintained physiological parameters during and post-surgery. Unlike UFH, Ir-CPI did not promote bleeding. CONCLUSIONS: Preclinical animal models used in this study showed that Ir-CPI is an effective and safe antithrombotic agent that provides a clinically relevant approach to thrombosis prevention in bypass systems, including highly thrombogenic CPB.

Specific features and survival of French bulldogs with congenital pulmonic stenosis: a prospective cohort study of 66 cases.

INTRODUCTION: The objectives of this study were to characterize the epidemiological, clinical, and echocardiographic features of French bulldogs (FBs) with congenital pulmonic stenosis and document their survival times and risk factors for cardiac death (CD). ANIMALS: This study included 66 FBs with congenital pulmonic stenosis. METHODS: Prospective cohort study including a survival analysis to assess time to CD. RESULTS: In most cases (53/66, 80%), at least two obstructive lesions were observed, most commonly valvular and supravalvular (42/66, 64%), with pulmonary trunk hypoplasia in 40/66 (61%) of cases. The median Doppler-derived peak trans-stenotic pressure gradient (ΔP) was very high: 170 mmHg (range = 34-291 mmHg), with ΔP ≥ 200 mmHg in 33% of FBs. Among the 51 FBs with an available follow-up and that did not undergo surgical valvuloplasty, 21/51 (41%) died, 67% (14/21) of deaths being CD. The median survival time from diagnosis to CD was 2.8 years (interquartile range = 0.8-4.6 years). Univariate Cox proportional hazard analyses revealed that age (hazard ratio [HR] = 2.3 per 1 year increase; p = 0.02), clinical signs at presentation (HR = 3.7; p = 0.03), ΔP (HR = 1.2 per 10 mmHg increase; p = 0.01), right ventricular dilation (HR = 5.0; p = 0.04), severe tricuspid regurgitation (HR = 7.6; p = 0.001), and right-sided congestive heart failure (HR = 4.8; p = 0.05) were associated with time to CD. After adjustment for age and ΔP, tricuspid regurgitation remained significantly associated with time to CD (HR = 5.1; p = 0.02). CONCLUSIONS: Pulmonic stenosis in FBs is commonly severe and complex, with at least 2 obstructive lesions in most cases, a high incidence of pulmonary trunk hypoplasia and CD, and strong association between prognosis and tricuspid regurgitation severity.

Surgical Treatment of Cor Triatriatum Sinister in a Cat Under Cardiopulmonary Bypass.

OBJECTIVE: To report the surgical repair of cor triatriatum sinister (CTS) incorporating heart-beating cardiopulmonary bypass (CPB) in a cat. STUDY DESIGN: Clinical case report. ANIMAL: Fourteen-month-old, 5.9-kg male castrated Maine Coon cat. MATERIALS AND METHODS: The cat had a 3 month history of inappetance, weight loss, and recurrent pulmonary edema. CTS with severe systolic pulmonary arterial (SPA) hypertension (124 mm Hg) was diagnosed by 2D echocardiography, color flow and continuous wave Doppler modes, and left atrial and pulmonary angiography. Surgery was performed through a left intercostal thoracotomy. CPB was initiated and the heart was kept beating. The left atrial appendage was opened and the intra-atrial membrane was excised. RESULTS: After 48 hours, the cat was doing well. Reduced SPA pressure (52 mm Hg) with decreased right heart enlargement was observed on ultrasound examination and the cat was discharged 6 days after surgery with oral antibiotics for 10 days, aspirin, and furosemide. Four months after surgery, the cat presented with increased activity and weight gain and was completely asymptomatic. Transthoracic echocardiography showed a marked improvement of all echo-Doppler variables with disappearance of SPA hypertension (24 mm Hg). Four years after surgery, the cat was still doing well with no recurrence of clinical signs despite the lack of medical treatment. CONCLUSION: CTS in the cat may be successfully treated by surgery facilitated by use of CPB leading to early and long-term substantial improvement in clinical status and cardiac function. CTS can safely be repaired under CPB in cats.

Ovarian function is restored after grafting of cryopreserved immature ovary in ewes.

As a result of advances in medical treatment, almost 80% of children who are diagnosed with cancer survive long-term. The adverse consequences of cancer treatments include impaired puberty and fertility. In prepubertal girls, the only therapeutic option is the cryopreservation of an ovary. To date, a dozen births have been reported after reimplantation of cryopreserved mature ovaries. To analyze ovarian function after immature grafts, we performed ovarian grafting in a ewe model. Fresh or cryopreserved ovaries from immature ewes were autografted in prepubertal or adult ewes. Cyclic hormonal activity was recovered 3 mo after grafting. Histological analysis demonstrated the presence of all follicle populations and corpora lutea not affected by cryopreservation. After 3 reproductive seasons, births had been observed in all groups, and the follicle-stimulating hormone status was under the limit, which indicated an exhausted ovary. As an indicator of potential imprinting default, the methylation status of the Igf2r gene was analyzed and did not show significant alteration compared with that of nonmanipulated animals. Taken together, these results demonstrate that immature ovarian grafting is able to restore spontaneous puberty and fertility and could guide the reimplantation of immature cortex in women.

A new self-expandable transcatheter aortic valve for transapical implantation: feasibility in acute and chronic animal experiments.

OBJECTIVES: Transcatheter aortic valve implantation (TAVI) is currently expanding worldwide, however all available prostheses share some fundamental design drawbacks. We investigated the feasibility, safety and hemodynamic performance of the innovative transapical Acurate TA™ self-expandable device, which has the unique advantage of offering anatomically correct self-alignment within the aortic root. DESIGN: Transapical TAVI was performed in six acute swine and six chronic sheep procedures, with follow-up of 7, 14, 21, 28, 60 and 90 days. TAVI was performed under TEE and angiographic guidance without rapid pacing. RESULTS: A partial sternotomy approach was used to access the LV-apex. All valve implantations were performed as planned and all animals survived the implantation procedure. After deployment, no migration, embolization or coronary obstruction was observed during the observation period. Intraoperative TEE examination identified no signs of intravalvular leakage or valve dysfunction. Transvalvular mean pressure gradients were 5.4 ± 2.2 mmHg decreasing during follow-up (1.6 ± 0.8 mmHg, 1.8 ± 0.8 mmHg, 1.3 ± 0.2, 1.8 ± 0.7 mmHg, 1.6 ± 0.8 mmHg), with a slight increase atday 90 (4.0 ± 2.4 mmHg, P < 0.05). Macroscopic examination at necropsy showed correct anatomical positioning of the valve stent without any signs of structural valve deterioration. CONCLUSIONS: These first results of the innovative self-expandable transapical ACURATE TA™ device explore the feasibility and safety of anatomically correct off-pump implantation with optimal hemodynamic results.

Echoguided closed commissurotomy for mitral valve stenosis in a dog.

Surgical treatment of mitral stenosis (MS) usually consists of open mitral commissurotomy (MC) or percutaneous balloon MC, which require a cardiopulmonary bypass or transseptal approach, respectively. We describe here the first surgical management of congenital MS in a dog using a less invasive procedure, a surgical closed MC under direct echo guidance. A 5-year-old female Cairn terrier was referred for ascites, weakness, and marked exercise intolerance for 2 months, which was refractory to medical treatment. Diagnosis of severe MS associated with atrial fibrillation (AF) was confirmed by echo-Doppler examination and electrocardiography. Poor response to medical treatment suggested a corrective procedure on the valve was indicated. However, due to the cost and high mortality rate associated with cardiopulmonary bypass, a hybrid MC was recommended. A standard left intercostal thoracotomy was performed and three balloon valvuloplasty catheters of differing diameters were sequentially inserted through the left atrium under direct echo guidance. Transesophageal echocardiography revealed a 62% reduction in the pressure half-time compared to the pre-procedure. Thirteen months after surgery the dog is still doing well with resolution of ascites and a marked improvement of most echo-Doppler variables.

Transcatheter glue arterial embolization of a mass in the hind limb of a dog.

This article reports the use of transarterial glue embolization in the treatment of a soft-tissue mass in the hind limb of a dog that was referred for a > 15-cm diameter soft tissue mass in the caudal thigh. Clinical improvement showed that the percutaneous therapeutic cyanoacrylate glue embolization procedure was technically feasible and useful.

Preclinical study of the novel vascular occluding agent, WST11, for photodynamic therapy of the canine prostate.

PURPOSE: Vascular targeted photodynamic therapy with WST09 shows promise for recurrent prostate cancer after radiation but hydrophobicity in aqueous solutions limited application. We tested the safety and efficacy of WST11, a novel water soluble vascular occluding agent, for vascular targeted photodynamic therapy of the dog prostate and compared it to WST09 vascular targeted photodynamic therapy. MATERIALS AND METHODS: Optical fibers were inserted in the prostate and connected to diode lasers. WST11 (Steba Biotech, Cedex, France) at varying doses, including a drug control with no light in 34 dogs, and WST09 (Steba Biotech) (2 mg/kg) in 3 dogs were infused during 10 minutes. Illumination was initiated at 5 or 10 minutes, and lasted up to 33.2 minutes based on laser fluence and delivered energy. Blood was collected for analysis and pharmacokinetics. The end point was at 1 week. RESULTS: No vascular targeted photodynamic therapy associated change was observed in blood pressure or blood test values. Circulating WST11 increased with drug infusion and decreased rapidly during 1 hour to reach undetectable levels by 24 hours. All except 1 dog with bowel intussusception did well after vascular targeted photodynamic therapy with only mild urinary symptoms that resolved within 24 to 48 hours. Lung and liver were normal. Hemorrhage was present in all prostates except controls. This translated into necrosis at a WST11 threshold and within a window of doses at fixed illumination. Necrosis was associated with loss of the vessel endothelial layer. Fluence highly impacted necrosis. WST11 vascular targeted photodynamic therapy was advantageously comparable to WST09 vascular targeted photodynamic therapy, and optimally ablated about 5.0 cm(3) of tissue per lobe and about 10 cm(3) of the whole prostate. CONCLUSIONS: The safety and efficacy of WST11 vascular targeted photodynamic therapy in the dog prostate support clinical applications for prostate cancer and benign prostatic hyperplasia.

Successful treatment of a congenital pulmonic valvular stenosis in a snow leopard (Uncia uncia) by percutaneous balloon valvuloplasty.

A 3-yr-old intact female snow leopard (Uncia uncia) was evaluated for progressive apathy, lethargy, and decreased appetite. Cardiac auscultation revealed a left basal grade IV/VI systolic ejection murmur, and an echocardiogram confirmed a severe pulmonic valvular stenosis (pressure gradient of 98 mm Hg). The lesion was managed by balloon valvuloplasty, resulting in a marked pressure gradient reduction (30 mm Hg). The cat recovered well, and clinical signs resolved. This is the first description of a pulmonary valve stenosis and management with balloon valvuloplasty in a wild felid.

Toward the development of a fully elastic mitral ring: preliminary, acute, in vivo evaluation of physiomechanical behavior.

OBJECTIVES: The optimal repair of functional mitral regurgitation is still debated. No device is able to simultaneously abolish mitral regurgitation and replicate natural mitral annular dynamics. We have tested a fully elastic mitral ring in an acute animal study with the purpose of evaluating (1) ring design and implantation technique, (2) elastic performance, and (3) acute effects on the native mitral annulus. METHODS: Ten healthy sheep underwent surgical implantation of mitral devices, the elastic component of which is represented by a helicoid metallic spring. Preimplantation and postimplantation echocardiographic parameter measurements to evaluate annular dynamics and ventricular function comprise mitral annular motion, systolic tissue Doppler imaging peak wave, transmitral pressure gradient, peak transmitral flow velocity, and ejection fraction. Postimplantation angiographic analysis allowed measurement of the mitral annular area and perimeter variations by means of segmentation of the radiopaque mitral device contour. RESULTS: No significant difference in terms of ejection fraction (P = .13) and systolic tissue Doppler imaging peak wave (P = .87) was found before and after implantation. Mitral annular motion (1.16 cm) was preserved. The percentage of systolic annular reduction derived from angiographic analysis was 14.1% (range, 7.7%-19.7%) in terms of area and 7.2% (range, 4.9%-10.0%) in terms of perimeter. CONCLUSIONS: A mitral elastic ring, implantable by using a standard technique, acutely preserves mitral annular dynamics, allowing area and perimeter changes. Further chronic study is needed to verify the biocompatibility and durability of the device.

Intra renal arterial injection of autologous mesenchymal stem cells in an ovine model in the postischemic kidney.

BACKGROUND AND AIMS: Acute renal failure (ARF) remains a major healthcare problem. Although modern medical therapy has improved its outcome, the syndrome still has high mortality and morbidity rates [Xue et al.: J Am Soc Nephrol 2006;17:1135-1142]. Recently, stem cell (SC) therapies have been proposed as an alternative for the treatment of ARF on the basis of the damaged cells' replacement or enhanced recovery or regeneration. The aims of this study were to investigate the engraftment of autologous mesenchymal stem cells (MSC) injected into the renal artery in an ovine model of ischemia reperfusion injury (IRI) and to assess the consequence of the delay between injury and cell transplantation on the engraftment. MATERIAL AND METHODS: MSC were transplanted in animals submitted to IRI or in healthy animals not submitted to IRI. Sheep with IRI were grafted at two different time points after injury. Unilateral renal IRI was performed by percutaneous transluminal placement of a balloon catheter in the renal artery. MSC were isolated from bone marrow, cultured, labeled and injected into the renal artery. RESULTS: All ewes showed renal engraftment by MSC, both in tubules and glomeruli. MSC expressed tubular epithelial cell markers and podocyte phenotype. There was a significant increase of engraftment of tubules by MSC when cells were injected early after injury indicating that the delay for cell transplantation after ischemic insult should be short. CONCLUSIONS: This is the first report of intra-arterial autologous transplantation of MSC in the kidney, resulting in a successful engraftment into tubular and glomerular structures. The results strongly suggest that the optimal time window for stem cell therapy is during the early phase of the ischemic injury.

Beating heart mitral valve replacement with a bovine pericardial bioprosthesis for treatment of mitral valve dysplasia in a Bull Terrier.

OBJECTIVES: To describe an open, beating heart surgical technique and use of a bovine pericardial prosthetic valve for mitral valve replacement (MVR) in the dog. STUDY DESIGN: Clinical case report. ANIMALS: Male Bull Terrier (17-month-old, 26 kg) with mitral valve dysplasia and severe regurgitation. METHODS: A bovine pericardial bioprosthesis was used to replace the mitral valve using an open beating heart surgical technique and cardiopulmonary bypass. RESULTS: Successful MVR was achieved using a beating heart technique. Mitral regurgitation resolved and cardiac performances improved (left ventricular end-diastolic diameter decreased from 57.6 to 48.7 mm, and left atrium/aorta ratio returned to almost normal, from 1.62 to 1.19). Cardiopulmonary by-pass time and total surgical duration were decreased compared with standard cardioplegic techniques. Surgical recovery was uneventful and on echocardiography 6 months later valve function was excellent. CONCLUSION: Considering the technique advantages (no cardiac arrest, ischemic reperfusion injury, and hypothermia, or the need for aortic dissection and cannulation for administration of cardioplegic solution), short-term mortality and morbidity may be reduced compared with standard cardioplegic techniques. CLINICAL RELEVANCE: Based on experience in this dog, beating heart mitral valvular replacement is a seemingly safe and viable option for the dog and bovine pericardial prosthesis may provide better long-term survival than mechanical prostheses.

Non-cultured cell transplantation in an ovine model of non-ischemic heart failure.

OBJECTIVE: Cell therapy may be a promising alternative or adjunct to current treatment modalities for ischemic heart failure. But little is known on the impact of myogenic cell transplantation in large animal models of non-ischemic cardiomyopathy. The aim of the present study was to explore whether an ovine model of toxin-induced heart disease could benefit from non-cultured skeletal muscle cell transplantation. METHODS: Sequential intracoronary injections of doxorubicin (0.75 mg/kg) were carried out every 2 weeks until echocardiographic detection of myocardial dysfunction. Sheep were then randomly assigned to either non-cultured cell transplantation (n=8) or placebo injection (n=5). For the cell therapy group, a skeletal muscle biopsy (about 10 g) was explanted from each animal approximately 3h before grafting. After thoracotomy, 20 epicardial injections were carried out. The animals were assessed one last time before sacrifice, 2 months after the thoracotomy. Cells were tracked with cmDiI (red fluorescence) and characterized with immunohistochemistry with monoclonal antibodies to a fast skeletal isoform of myosin heavy chain. RESULTS: Two months after intramyocardial grafting, tissue Doppler imaging and conventional echocardiographic assessment of the groups showed a marked improvement in the non-cultured cell therapy group. Ejection fraction (EF) (p<0.05) as well as systolic endocardial velocities (p<0.01) improved versus the placebo group. CmDiI and skeletal myosin heavy chain expression was detected in all animals at 2 months after implantation confirming engraftment of skeletal muscle cells. CONCLUSIONS: In conclusion, our data indicate that non-cultured muscle cell transplantation is feasible and may translate into a functional benefit in an ovine model of dilated heart failure.

A repositionable valved stent for endovascular treatment of deteriorated bioprostheses.

OBJECTIVES: 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). BACKGROUND: Among the different devices designed for percutaneous VR, none has the potential for repositioning of a fully deployed VS. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Macroscopic assessment of porcine coronary vessel wall trauma after percutaneous cardiac catheterization and intervention.

A macroscopic pathological assessment of the coronary arteries of a pig's heart, in which stent implantation and intra-vascular ultrasound and thermography pullbacks were performed, shows that during percutaneous coronary catheterization and intervention, one of the major vessel traumas occurs in the very proximal part of the coronary arteries, where the guiding catheter tip is manipulated to adequately engage the vessels.

Expandable right ventricular-to-pulmonary artery conduit: an animal study.

This study was performed to assess a new vascular stent graft as an expandable valved conduit for right ventricular outflow tract (RVOT) reconstruction in sheep. Conduits were constructed by sewing an 18-mm valved conduit inside a stent. Crimped to 16 mm, they were implanted either under or without extracorporeal circulation in seven (group A) and in five (group B) sheep, respectively. Six weeks and 3 mo after their insertion, conduits were dilated intraluminally. A valved stent was implanted percutaneously into conduits before they were killed. Two animals from group A recovered normally, whereas five animals had a complicated postoperative course. In group B, one died acutely due to kinking of the conduit. Balloon dilatations were performed in all surviving animals. First dilatations had a slight impact on valvular function in all animals but one, whereas second dilatations led to significant PR in all. Transcatheter valve implantation was performed successfully. When animals were killed, no bleeding was found around the surgically implanted device. In conclusion, we designed a biologic valved conduit for RVOT reconstruction that can be dilated sequentially to follow animal growth. This new device can have tremendous applications in children with congenital heart diseases involving the RVOT.

An ovine model of chronic heart failure: echocardiographic and tissue Doppler imaging characterization.

BACKGROUND AND AIM OF THE STUDY: Heart failure in the western world is a major health-care issue. In order to validate novel surgical or pharmacological treatments, reproducible animal models of left ventricular dysfunction are necessary. In the current study, we report our data and experience with a model of toxin-induced heart failure in the sheep. METHODS: Sequential intracoronary injections of doxorubicin (0.75 mg/kg) were carried out every 2 weeks until standard echocardiographic and tissue Doppler imaging detection of myocardial systolic dysfunction. The animals were assessed 1 month later and harvested. Indices of cardiac function from baseline to last day of protocol were recorded and their differences were evaluated by a Wilcoxon rank test for paired data. RESULTS: Ten sheep received 2.5 +/- 0.7 intracoronary injections of a cumulative dose of 88.8 +/- 25 mg/m2 doxorubicin. All available parameters demonstrated signs of severe cardiac dysfunction with statistical significance. All hearts demonstrated severe histological lesions, some of which were consistent with doxorubicin-induced toxicity. CONCLUSIONS: The present study shows that this ovine model is reproducible and stable. It can therefore be relevant to the study of chronic heart failure. It will be incorporated in our future studies concerning novel treatments (such as cell therapy) of nonischemic dilated cardiomyopathy.