Andrea Amerini

A novel approach to an anatomical adapted stent design for the percutaneous therapy of tricuspid valve diseases: preliminary experiences from an engineering point of view.

Tricuspid valve regurgitation mostly occurs as result of dilation of the right ventricle, secondary to left heart valve diseases. Until recently, little attention has been given to the development of percutaneous therapeutic tools exclusively designed for tricuspid valve disease. A new approach to the interventional therapy of tricuspid regurgitation, in particular, the design of a conceptual new valve-bearing, self-expansible stent, is presented here. A three-dimensional computer model of a right porcine heart was developed to gain a realistic anatomical geometry. The new design consists of two tubular stent elements, one inside the superior vena cava and the other inside the tricuspid valve annulus after being eventually equipped with a biological valve prosthesis, which are connected by struts. Anchoring to the heart structure is provided primarily by the vena cava stent, strengthened by the struts. The stents are designed to be cut from a 10 mm tube and later expanded to their designated diameter. Simulation software analyzing the expansion process with respect to the intended geometrical design is used in an iterative process. A validation of the anatomical geometry and function of the stent design inside a silicone model within in vitro tests and a random porcine heart shows an accurate anatomical fitting.

Video-assisted pericardioscopic surgery: refinement of a new technique for implanting epimyocardial pacemaker leads

OBJECTIVE Current alternative approaches for pacemaker lead implantation imply the breach of the pleural space. Recently, the feasibility of experimental lead implantation by rigid endoscopy has been described. The use of flexible endoscopes and a standardised application has not been realised yet. Our main goal was to compare rigid and flexible endoscopy and to establish a standardised protocol for the implementation of a closed-chest subxiphoid approach for epimyocardial lead implantation. METHODS Rigid and flexible endoscopes were used for placement of screw-in pacing leads (4-F). A total of 17 adult pigs (80 kg) were anaesthetised and a 10-mm subxiphoid axial incision performed. The pericardium was opened and entered under endoscopic vision. Epimyocardial electrodes were implanted through the endoscope onto all four chambers. Standard haemodynamic measurements and pacing measurements were carried out. RESULTS Both methods were deployed in the first three individuals. Superior endorsement of rigid endoscopy, due to better orientation and stability, led to its exclusive deployment in the remaining 14 individuals. Access to the implantation sites was quick (<10 min). A plastic cover had to be applied to reduce arrhythmia (VentricularExtraSystoles(bare): 17 ± 2.2 min(-1) vs VentricularExtraSystoles(cover): 5 ± 1.9 min(-1); n = 4). Measured pacing parameters were comparable with classic endocardial-derived thresholds. Post-mortem examination revealed no relevant damage/injury and/or bleeding in the heart and circumjacent tissue. There was no evidence of injury at the implantation sites and the corresponding pericardium. The electrodes showed excellent anchorage inside the myocardial tissue (penetration depths: 3 ± 0.2mm) and resisted high tractive forces. CONCLUSION Flexible endoscopy is not suitable for exclusive deployment inside the pericardial space, whereas rigid endoscopy presented itself as a safe, fast and simple approach for epimyocardial lead implantation using an insulating trocar. Without cover, malignant arrhythmia constrains the implementation of video-assisted pericardioscopic surgery (VAPS). Subxiphoid VAPS permits optimal lead positioning under direct vision without fluoroscopy, without the breach of the pleural space and with a short procedural duration (<60 min). Our standardised minimal-invasive approach allows visualisation and intervention, potentially of all intrapericardial structures.

A personalized approach to interventional treatment of tricuspid regurgitation: experiences from an acute animal study

OBJECTIVES Interventional treatment of tricuspid valve disease has so far received little attention due to the anatomical challenges in a thrombogenic surrounding. In the present study, we present an imaging-based, personalized interventional approach to the therapy of tricuspid regurgitation. METHODS In our porcine model, we used rapid prototyping to build a matrix reproducing the geometry of the right atrium that was previously derived from computer tomography (CT) scans. Over this matrix, a braided nitinol device fitting almost completely the right atrium was crafted. An additional tubular stent component was developed to carry a tissue valve prosthesis. This part was designed to be connectable to the annular portion of the main device. In our feasibility study, the crimped device was implanted via jugular access into the right atrium of 12 pigs and expanded subsequently. Following isolated implantation of the device without the valve-carrying component, further procedures included implantation of the whole composite device, including the mentioned tissue valve. Representing a only feasibility study, all implantations were performed under full bypass and direct sight. On-site visualization was performed by both echocardiography and fluoroscopy. Additional imaging was realized by postoperative CT scans. RESULTS Following implantation, 9 of 12 animals were weaned from cardiopulmonary bypass. Correct positioning of the device and orthodromic blood flow as maintained by the valve prosthesis were demonstrated by echocardiography and fluoroscopy. Postoperative contrast CT evaluation demonstrated proper fitting of the device into the right-sided heart cavities without obstruction of the outflow tract. Autopsy additionally confirmed its correct positioning without major trauma to surrounding structures. CONCLUSIONS We demonstrated the feasibility in principle of a personalized interventional treatment for tricuspid regurgitation using a braided stent, based on individual cardiac imaging, with anchoring forces mainly exerted on the venae cavae and on the inner surface of the right atrium. The design process of this device is a good indicator of the growing potential of an imaging-based personalized simulation and production approach for the treatment of tricuspid valve disease.

Feasibility and efficacy of bypassing the right ventricle and pulmonary circulation to treat right ventricular failure: an experimental study

BackgroundRight ventricular failure (RVF) and -support is associated with poor results. We aimed for a new approach of right - sided assistance bypassing the right ventricle and pulmonary circulation in order to better decompress the right ventricle and optimize left ventricular filling.MethodsFrom a microaxial pump (Abiomed), a low resistance oxygenator (Maquet and Novalung) and two cannulas (28 and 27 Fr) a system was set up and evaluated in an ovine model (n = 7). Connection with the heart was the right and left atrium. One hour the system was operated without RVF and turned of again. Then a RVF was induced and the course with the system running was evaluated. Complete hemodynamic monitoring was performed as well as echocardiography, flow measurement and blood gas analysis.ResultsThe overall performance of the system was reliable. Without RVF no relevant changes of hemodynamics occurred; blood gases were supra normal. In RVF a cardiogenic shock developed (MAP 35 ± 13 mmHg, CO 1,1 ± 0,7 l/min). Immediately after starting the system the circulation normalized (significant increase of MAP to 85 ± 13 mmHg, of CO to 4,5 ± 1,9). Echocardiography also revealed right ventricular recovery. After stopping the system, RVF returned.ConclusionsBypassing the right ventricle and pulmonary circulation with an oxygenating assist device, which may offer the advantages of enhanced right ventricular decompression and augmented left atrial filling, is feasible and effective in the treatment of acute RVF. Long time experiments are needed.

Pulmono-atrial shunt and lung assist to treat right ventricular failure

In right ventricular failure (RVF) a decrease of right ventricular afterload and improvement of left atrial filling could be achieved by a pulmonary artery-left atrial (PA)-shunt. To avoid cyanosis, artificial oxygenation is necessary. In 11 pigs a PA-shunt was created. An interventional lung assist device (ILA) was installed from the femoral artery to vein in 5 pigs (serial in relation to native lung: Group I) and into the PA-shunt in 6 pigs (parallel: Group II). RVF was induced by pulmonary artery banding. Right ventricular performance was determined by pulse contour analysis, pressure - and flow measurements. In both groups a stable RVF was generated. In Group I cardiac output trended to increase but neither right ventricular filling pressures nor arterial pressure changed significantly. The PaO2 decreased significantly. In Group II cardiac output and arterial pressure increased significantly under a shunt flow of 2.3- 2.6 l/min and the animals recovered from cardiogenic shock. In conclusion a PA-shunt with a parallel lung assist can effectively reverse the deleterious effects of RVF.

Prevention of sternal dehiscence with the Sternum External Fixation (Stern-E-Fix) corset – a randomized trial in 750 patients

BackgroundThe main objective of this study will be to determine the effects of a new advanced sternum external fixation (Stern-E-Fix) corset on prevention of sternal instability and mediastinitis in high-risk patients.MethodsThis prospective, randomized study (January 2009 – June 2011) comprised 750 male patients undergoing standard median sternotomy for cardiac procedures (78% CABG). Patients were divided in two randomized groups (A, n = 380: received a Stern-E-Fix corset postoperatively for 6 weeks and B, n = 370: control group received a standard elastic thorax bandage). In both groups, risk factors for sternal dehiscence and preoperative preparations were similar.ResultsWound infections occurred in n = 13 (3.42%) pts. in group A vs. n = 35 (9.46%) in group B. In group A, only 1 patient presented with sternal dehiscence vs. 22 pts. in group B. In all 22 patients, sternal rewiring followed by antibiotic therapy was needed. Mediastinitis related mortality was none in A versus two in B. Treatment failure in group B was more than five times higher than in A (p = 0.01); the mean length of stay in hospital was 12.5 ± 7.4 days (A) versus 18 ± 15.1 days (B) (p=0.002). Re-operation for sternal infection was 4 times higher in group B. Mean ventilation time was relatively longer in B (2.5 vs. 1.28 days) (p = 0.01). The mean follow-up period was 8 weeks (range 6 – 12 weeks).ConclusionsWe demonstrated that using an external supportive sternal corset (Stern-E-Fix) yields a significantly better and effective prevention against development of sternal dehiscence and secondary sternal infection in high-risk poststernotomy patients.

Takotsubo cardiomyopathy with concurrent multivessel obstructive coronary artery disease: proposition for a new clinical entity and first case surgical experience

We present a seldom seen case of Takotsubo cardiomyopathy (TCM) with concurrent obstructive coronary artery disease (OCAD) and its first case surgical experience. We propose that TCM and OCAD can coexist and that the presence of OCAD should not be an exclusion criterion for the diagnosis of TCM.

Risk factors for the development of right ventricular failure after left ventricular assist device implantation—a single-centre retrospective with focus on deformation imaging

OBJECTIVES Right heart failure (RHF) after the implantation of a left ventricular assist device (LVAD) remains a dreaded postoperative complication. Using 2D speckle-tracking echocardiography, it is possible to acquire right ventricular global and regional function. The aim of our study was to assess whether speckle-tracking echocardiography values will better predict the RHF post-continuous-flow LVAD implantation. METHODS From January 2014 to January 2016, 54 patients who underwent LVAD implantation were included and retrospectively analysed. Clinical, invasive haemodynamic (right and left heart catheterization), laboratory and transthoracic echocardiography data were reviewed. Multivariable logistic regression was performed using RHF as dependent variable. RESULTS Thirteen patients (24%) developed RHF. These patients had significantly elevated procalcitonin (P = 0.011), elevated central venous pressure (CVP) pre- and post-LVAD implantation (P = 0.002 and 0.031, respectively), higher right ventricular (RV) and pulmonary systolic pressure (P = 0.016 and 0.013, respectively), higher Michigan Risk Score (P = 0.001) and a lower peak systolic longitudinal strain of the basal RV free wall (P = 0.032). Haemoglobin, procalcitonin, RV systolic pressure, basal right ventricular free wall and pre-CVP entered the final multivariable analysis, only basal right ventricular free wall (P < 0.001) and pre-CVP (P < 0.001) remained significant predictors of RHF. The sensitivity and specificity of the final model were 85.7% and 95.4%, respectively. The negative predictive value reached 94%. CONCLUSIONS 2D strain parameters of the RV free wall seem to be auspicious for RV function and predicting RHF. Moreover, intraoperative CVP should not be neglected since elevated values proved to be highly associated with RHF. Our results represent a valuable supplement to other scores by considering both echocardiography and intraoperative data.

Development of a Transcatheter Tricuspid Valve Prosthesis Through Steps of Iterative Optimization and Finite Element Analysis.

The development of a transcatheter tricuspid valve prosthesis for the treatment of tricuspid regurgitation (TR) is presented. The design process involves an iterative development method based on computed tomography data and different steps of finite element analysis (FEA). The enhanced design consists of two self-expandable stents, one is placed inside the superior vena cava (SVC) for primary device anchoring, the second lies inside the tricuspid valve annulus (TVA). Both stents are connected by flexible connecting struts (CS) to anchor the TVA-stent in the orthotopic position. The iterative development method includes the expansion and crimping of the stents and CS with FEA. Leaflet performance and leaflet-stent interaction were studied by applying the physiologic pressure cycle of the right heart onto the leaflet surfaces. A previously implemented nitinol material model and a new porcine pericardium material model derived from uniaxial tensile tests were used. Maximum strains/stresses were approx. 6.8% for the nitinol parts and 2.9 MPa for the leaflets. Stent displacement because of leaflet movement was ≤1.8 mm at the commissures and the coaptation height was 1.6-3 mm. This led to an overall good performance of the prosthesis. An anatomic study showed a good anatomic fit of the device inside the human right heart.

Oxygenated shunting from right to left: a feasibility study of minimized atrio-atrial extracorporeal membrane oxygenation for mid-term lung assistance in an acute ovine model

OBJECTIVES Right ventricular failure is often the final phase in acute and chronic respiratory failure. We combined right ventricular unloading with extracorporeal oxygenation in a new atrio-atrial extracorporeal membrane oxygenation (ECMO). METHODS Eleven sheep (65 kg) were cannulated by a 28-Fr inflow cannula to the right atrium and a 25-Fr outflow cannula through the lateral left atrial wall. Both were connected by a serial combination of a microaxial pump (Impella Elect(®), Abiomed Europe, Aachen, Germany) and a membrane oxygenator (Novalung(®)-iLA membrane oxygenator; Novalung GmbH, Hechingen, Germany). In four animals, three subsequent states were evaluated: normal circulation, apneic hypoxia and increased right atrial after load by pulmonary banding. We focused on haemodynamic stability and gas exchange. RESULTS All animals reached the end of the study protocol. In the apnoea phase, the decrease in PaO2 (21.4 ± 3.6 mmHg) immediately recovered (179.1 ± 134.8 mmHg) on-device in continuous apnoea. Right heart failure by excessive after load decreased mean arterial pressure (59 ± 29 mmHg) and increased central venous pressure and systolic right ventricular pressure; PaO2 and SvO2 decreased significantly. On assist, mean arterial pressure (103 ± 29 mmHg), central venous pressure and right ventricular pressure normalized. The SvO2 increased to 89 ± 3% and PaO2 stabilized (129 ± 21 mmHg). CONCLUSIONS We demonstrated the efficacy of a miniaturized atrio-atrial ECMO. Right ventricular unloading was achieved, and gas exchange was well taken over by the Novalung. This allows an effective short- to mid-term treatment of cardiopulmonary failure, successfully combining right ventricular and respiratory bridging. The parallel bypass of the right ventricle and lung circulation permits full unloading of both systems as well as gradual weaning. Further pathologies (e.g. ischaemic right heart failure and acute lung injury) will have to be evaluated.