Publications by authors named "Ludwig K von Segesser"

219 Publications

Outcome of right ventricular assist device implantation following left ventricular assist device implantation: Systematic review and meta-analysis.

Perfusion 2021 Jun 11:2676591211024817. Epub 2021 Jun 11.

Department of Cardiac Surgery, University Hospital Basel, Basel, Switzerland.

Objectives: The main aim was a systematic evaluation of the current evidence on outcomes for patients undergoing right ventricular assist device (RVAD) implantation following left ventricular assist device (LVAD) implantation.

Methods: This systematic review was registered on PROSPERO (CRD42019130131). Reports evaluating in-hospital as well as follow-up outcome in LVAD and LVAD/RVAD implantation were identified through Ovid Medline, Web of Science and EMBASE. The primary endpoint was mortality at the hospital stay and at follow-up. Pooled incidence of defined endpoints was calculated by using random effects models.

Results: A total of 35 retrospective studies that included 3260 patients were analyzed. 30 days mortality was in favour of isolated LVAD implantation 6.74% (1.98-11.5%) versus 31.9% (19.78-44.02%) p = 0.001 in LVAD with temporary need for RVAD. During the hospital stay the incidence of major bleeding was 18.7% (18.2-19.4%) versus 40.0% (36.3-48.8%) and stroke rate was 5.6% (5.4-5.8%) versus 20.9% (16.8-28.3%) and was in favour of isolated LVAD implantation. Mortality reported at short-term as well at long-term was 19.66% (CI 15.73-23.59%) and 33.90% (CI 8.84-59.96%) in LVAD respectively versus 45.35% (CI 35.31-55.4%) p ⩽ 0.001 and 48.23% (CI 16.01-80.45%) p = 0.686 in LVAD/RVAD group respectively.

Conclusion: Implantation of a temporary RVAD is allied with a worse outcome during the primary hospitalization and at follow-up. Compared to isolated LVAD support, biventricular mechanical circulatory support leads to an elevated mortality and higher incidence of adverse events such as bleeding and stroke.
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http://dx.doi.org/10.1177/02676591211024817DOI Listing
June 2021

Nitric Oxide-cGMP Pathway Modulation in an Experimental Model of Hypoxic Pulmonary Hypertension.

J Cardiovasc Pharmacol Ther 2021 May 8:10742484211014162. Epub 2021 May 8.

Department Cœur-Vaisseaux, Cardiac Surgery Center, 30635University Hospital of Lausanne, Lausanne, Switzerland.

Manipulation of nitric oxide (NO) may enable control of progression and treatment of pulmonary hypertension (PH). Several approaches may modulate the NO-cGMP pathway in vivo. Here, we investigate the effectiveness of 3 modulatory sites: (i) the amount of l-arginine; (ii) the size of plasma NO stores that stimulate soluble guanylate cyclase; (iii) the conversion of cGMP into inactive 5'-GMP, with respect to hypoxia, to test the effectiveness of the treatments with respect to hypoxia-induced PH. Male rats (n = 80; 10/group) maintained in normoxic (21% O) or hypoxic chambers (10% O) for 14 days were subdivided in 4 sub-groups: placebo, l-arginine (20 mg/ml), the NO donor molsidomine (15 mg/kg in drinking water), and phoshodiesterase-5 inhibitor sildenafil (1.4 mg/kg in 0.3 ml saline, i.p.). Hypoxia depressed homeostasis and increased erythropoiesis, heart and right ventricle hypertrophy, myocardial fibrosis and apoptosis inducing pulmonary remodeling. Stimulating anyone of the 3 mechanisms that enhance the NO-cGMP pathway helped rescuing the functional and morphological changes in the cardiopulmonary system leading to improvement, sometimes normalization, of the pressures. None of the treatments affected the observed parameters in normoxia. Thus, the 3 modulatory sites are essentially similar in enhancing the NO-cGMP pathway, thereby attenuating the hypoxia-related effects that lead to pulmonary hypertension.
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http://dx.doi.org/10.1177/10742484211014162DOI Listing
May 2021

Performance characteristics of the new Eurosets magnetically suspended centrifugal pump.

Perfusion 2021 03 20;36(2):183-189. Epub 2020 Jun 20.

Department of Surgery and Anesthesiology, Cardio-Vascular Research, Lausanne, Switzerland.

Objective: The aim was to evaluate the performance of a newly developed magnetically suspended centrifugal pump head intended for use as a ventricular assistance device with a newly developed extracorporeal membrane oxygenator setup.

Methods: In an experimental setup, an extracorporeal membrane oxygenator circuit was established in three calves with a mean weight of 68.2 ± 2.0 kg. A magnetically levitated centrifugal pump was tested, along with a newly designed extracorporeal membrane oxygenator console, at three different flow ranges: (a) 0.0 to 5.2 L/min, (b) 0.0 to 7.1 L/min, and (c) 0.0 to 6.0 L/min. For each setup, the animals were supported by a circuit for 6 h. Blood samples were collected just before caridiopulmonary bypass (CPB) after 10 min on bypass and after 1, 2, 5, and 6 h of perfusion for hemolysis determination and biochemical tests. Values were recorded for blood pressure, mean flow, and pump rotational speed. Analysis of variance was used for repeated measurements.

Results: Mean pump flows achieved during the three 6 h pump runs for the three pump heads studied were as follows: (a) flow range 0.0 to 5.2 L/min, 3.6 ± 1.5 L/min, (b) flow range 0.0 to 7.1 L/min, 4.9 ± 1.3 L/min, and (c) flow range 0.0 to 6.0 L/min, 3.8 ± 1.5 L/min. Blood trauma, evaluated by plasma hemoglobin and lactate dehydrogenase levels, did not help in detecting any significant hemolysis. Thrombocytes and white blood cell count profiles showed no significant differences between the groups at the end of the 6 h perfusion. At the end of testing, no clot deposition was found in the oxygenator, and there was no evidence of peripheral emboli.

Conclusion: The results suggest that the newly developed magnetically suspended centrifugal pump head provides satisfactory hydrodynamic performance in an acute perfusion scenario without increasing hemolysis.
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http://dx.doi.org/10.1177/0267659120931990DOI Listing
March 2021

Effects of PDE-5 Inhibition on the Cardiopulmonary System After 2 or 4 Weeks of Chronic Hypoxia.

Cardiovasc Drugs Ther 2019 08;33(4):407-414

Department Cœur-Vaisseaux, Cardiac Surgery center, University Hospital of Lausanne, Lausanne, Switzerland.

Purpose: In pulmonary hypertension (PH), hypoxia represents both an outcome and a cause of exacerbation. We addressed the question whether hypoxia adaptation might affect the mechanisms underlying PH alleviation through phosphodiesterase-5 (PDE5) inhibition.

Methods: Eight-week-old male Sprague-Dawley rats were divided into two groups depending on treatment (placebo or sildenafil, a drug inhibiting PDE5) and were exposed to hypoxia (10% O) for 0 (t0, n = 9/10), 2 (t2, n = 5/5) or 4 (t4, n = 5/5) weeks. The rats were treated (0.3 mL i.p.) with either saline or sildenafil (1.4 mg/Kg per day).

Results: Two-week hypoxia changed the body weight (- 31% vs. - 27%, respectively, P = NS), blood hemoglobin (+ 25% vs. + 27%, P = NS) and nitrates+nitrites (+ 175% vs. + 261%, P = 0.007), right ventricle fibrosis (+ 814% vs. + 317%, P < 0.0001), right ventricle hypertrophy (+ 84% vs. + 49%, P = 0.007) and systolic pressure (+ 108% vs. + 41%, P = 0.001), pulmonary vessel density (+ 61% vs. + 46%, P = NS), and the frequency of small (< 50 µm wall thickness) vessels (+ 35% vs. + 13%, P = 0.0001). Most of these changes were maintained for 4-week hypoxia, except blood hemoglobin and right ventricle hypertrophy that continued increasing (+ 52% vs. + 42%, P = NS; and + 104% vs. + 83%, P = 0.04). To further assess these observations, small vessel frequency was found to be linearly related with the right ventricle-developed pressure independent of hypoxia duration.

Conclusions: Thus, although hypoxia adaptation is not yet accomplished after 4 weeks, PH alleviation by PDE5 inhibition might nevertheless provide an efficient strategy for the management of this disease.
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http://dx.doi.org/10.1007/s10557-019-06887-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6689028PMC
August 2019

Outcome of inter-hospital transfer of patients on extracorporeal membrane oxygenation in Switzerland.

Swiss Med Wkly 2019 Apr 17;149:w20054. Epub 2019 Apr 17.

Clinic for Cardiovascular Surgery, University Heart Centre, Zurich, Switzerland.

Aims Of The Study: An extracorporeal membrane oxygenation system (ECMO), as a bridge to either recovery, a ventricular assist device (VAD), or heart or lung transplantation, may be the only lifesaving option for critically ill patients suffering from refractory cardiac, respiratory or combined cardiopulmonary failure. As peripheral hospitals may not offer ECMO treatment, tertiary care centres provide specialised ECMO teams for on-site implantation and subsequent patient transfer on ECMO to the tertiary hospital. This study reports the results of the largest ECMO transportation programme in Switzerland and describes its feasibility and safety.

Methods: Patients transported on ECMO by our mobile ECMO team to our tertiary centre between 1 September 2009 and 31 December, 2016 underwent retrospective analysis. Implantation was performed by our specialised ECMO team (primary transport) or by the medical staff of the referring hospital (secondary transport) with subsequent transfer to our institution. Type of ECMO, transport data, patient baseline characteristics, operative variables and postoperative outcomes including complications and mortality were collected from medical records.

Results: Fifty-eight patients were included (three patients excluded: one repatriation, two with incomplete medical records). Thirty-five patients (60%) received veno-venous, 22 (38%) veno-arterial and one patient (2%) veno-venoarterial ECMO. Forty-nine (84%) patients underwent primary and nine (16%) secondary transport. Thirty-five (60%) patients were transferred by helicopter and 23 (40%) by ambulance, with median distances of 38.1 (13–225) km and 21 (3-71) km respectively. No clinical or technical complications occurred during transportation. During hospitalisation, three patients had ECMO-associated complications (two compartment syndrome of lower limb, one haemothorax after central ECMO upgrade). Median days on ECMO was 8 (<1–49) and median days in hospital was 17 (<1–122). ECMO weaning was successful in 41 patients (71%), on-transport survival was 100%, 40 patients survived to discharge (69%), and overall survival was 67% (39 patients) at a median follow-up of 58 days (<1–1441). Cumulative survival was significantly affected by cardiogenic shock vs. ARDS (p = 0.001), veno-arterial and veno-venoarterial vs. veno-venous ECMO (p = 0.001) and after secondary vs. primary transport (p <0.001). The ECMO weaning rate was significantly lower after secondary transfer (22%, two patients, both vaECMO) vs. primary transfer (80%, p = 0.002, 39 patients of which 35 (71%) had vvECMO).

Conclusions: The first results of our ECMO transportation programme show its feasibility, safety and efficacy without on-site implant or on-transport complications or mortality. The favourable early survival may justify the large effort with respect to logistics, costs and manpower. With rising awareness, referring centres may increasingly consider this lifesaving option at an early stage, which may further improve outcomes.
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http://dx.doi.org/10.4414/smw.2019.20054DOI Listing
April 2019

The Swiss Heart Foundation.

Eur Heart J 2018 12;39(45):3995-3997

President of the Swiss Heart Foundation.

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http://dx.doi.org/10.1093/eurheartj/ehy705DOI Listing
December 2018

Sex, crime and surgery: Interactive CardioVascular and Thoracic Surgery in the age of fake news.

Interact Cardiovasc Thorac Surg 2018 06;26(6):894-896

Department of Surgery and Anesthesiology, Cardio-Vascular Research, Lausanne, Switzerland.

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http://dx.doi.org/10.1093/icvts/ivy144DOI Listing
June 2018

New, optimized, dual-lumen cannula for veno-venous ECMO.

Perfusion 2018 05;33(1_suppl):18-23

4 Department of Cardio-Vascular Surgery, University Hospital, Zurich, Switzerland.

Objective: The present study was designed to assess in vivo a new, optimized, virtually wall-less, dual-lumen, bi-caval cannula for veno-venous ECMO in comparison to a commercially available cannula.

Methods: Veno-venous extracorporeal membrane oxygenation (ECMO) was carried out in a bovine study (n=5, bodyweight 75±5kg). Following systemic heparinization, ECMO was established in a trans-jugular fashion through a calibrated 23F orifice, using a new, optimized, virtually wall-less, dual-lumen, bi-caval 24F cannula (Smartcanula LLC, Lausanne, Switzerland) versus a commercially available 23F bi-caval, dual-lumen control cannula (Avalon Elite, Maquet, Rastatt, Germany) in a veno-venous ECMO setup. Veno-venous ECMO was initiated at 500 revolutions per minute (RPM) and increased by incremental steps of 500 RPM up to 2500 RPM. Catheter outlet pressure, catheter inlet pressure, oxygen saturation and pump flow were recorded at each stage.

Results: Mean flow accounted for 0.37±0.04 L/min for wall-less versus 0.29± 0.07 L/min for control at 500 RPM, 0.97±0.12 versus 0.67±0.06 at 1000 RPM, 1.60±0.14 versus 1.16±0.08 at 1500 RPM, 2.31±0.13 versus 1.52±0.13 for 2000 RPM and 3.02±0.5 versus 2.11±0.18 (p<0.004). The mean venous suction required was 19±8 mmHg for wall-less versus 20±3 mmHg for control at 500 RPM, 7±3 versus 9±4 for 1000 RPM, -11±10 versus -12±8 at 1500 RPM, -39±15 versus -49±10 for 2000 RPM and -60±28 versus -94±7 for 2500 RPM. The mean venous injection pressure accounted for 29±7 mmHg for wall-less versus 27±5 mmHg for control at 500 RPM, 50±6 versus 61±7 at 1000 RPM, 89±10 versus 99±17 for 1500 RPM, 142±14 versus 161±9 at 2000 RPM and 211±41 versus 252 ±3 for 2500 RPM.

Conclusion: Compared to the commercially available control cannula, the new, optimized, virtually wall-less, dual-lumen, bi-caval 24F cannula allows for significantly higher blood flows, requires less suction and results in lower injection pressures in vivo.
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http://dx.doi.org/10.1177/0267659118765597DOI Listing
May 2018

Clinical Experience in Minimally Invasive Cardiac Surgery With Virtually Wall-Less Venous Cannulas.

Innovations (Phila) 2018 Mar/Apr;13(2):104-107

Objective: Inadequate peripheral venous drainage during minimally invasive cardiac surgery (MICS) is a challenge and cannot always be solved with increased vacuum or increased centrifugal pump speed. The present study was designed to assess the benefit of virtually wall-less transfemoral venous cannulas during MICS.

Methods: Transfemoral venous cannulation with virtually wall-less cannulas (3/8″ 24F 530-630-mm ST) was performed in 10 consecutive patients (59 ± 10 years, 8 males, 2 females) undergoing MICS for mitral (6), aortic (3), and other (4) procedures (combinations possible). Before transfemoral insertion of wall-less cannulas, a guidewire was positioned in the superior vena cava under echocardiographic control. The wall-less cannula was then fed over the wire and connected to a minimal extracorporeal system. Vacuum assist was used to reach a target flow of 2.4 l/min per m with augmented venous drainage at less than -80 mm Hg.

Results: Wall-less venous cannulas measuring either 630 mm (n = 8) in length or 530 mm (n = 2) were successfully implanted in all patients. For a body size of 173 ± 11 cm and a body weight of 78 ± 26 kg, the calculated body surface area was 1.94 ± 0.32 m. As a result, the estimated target flow was 4.66 ± 0.78 l/min, whereas the achieved flow accounted for 4.98 ± 0.69 l/min (107% of target) at a vacuum level of 21.3 ± 16.4 mm Hg. Excellent exposure and "dry" intracardiac surgical field resulted.

Conclusions: The performance of virtually wall-less venous cannulas designed for augmented peripheral venous drainage was tested in MICS and provided excellent flows at minimal vacuum levels, confirming an increased performance over traditional thin wall cannulas. Superior results can be expected for routine use.
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http://dx.doi.org/10.1097/IMI.0000000000000478DOI Listing
October 2018

Impact of aortic root annuloplasty on 3D aortic root geometry.

J Surg Res 2018 05 30;225:45-53. Epub 2018 Jan 30.

Department of Cardiac Surgery, University Hospital Basel, Basel, Switzerland.

Background: The aim was to evaluate the impact of aortic root (AoR) annuloplasty on 3D AoR deformation.

Methods: In experimental setup, Yacoub procedure and Yacoub with annuloplasty were performed. Results were compared to native AoR. In each AoR modality, six microsonometric (2 mm, 200 Hz) crystals were implanted at the sinotubular junction (STJ) and at the AoR base (AoB). 3D deformation of the AoR was determined by AoR tilt (α) and rotation (β) angle changes.

Results: Tilt angle in Yacoub AoR with annuloplasty and in Yacoub AoR was maximal at ejection, 26.71 ± 0.18° and 24.91 ± 0.13°, respectively, and minimal at diastole, 25.34 ± 0.15° and 21.90 ± 0.15°, respectively. Rotation angle in Yacoub AoR with and without annuloplasty was maximal at ejection, 27.04 ± 0.25° and 23.53 ± 0.54°, respectively, and minimal at diastole, 24.84 ± 0.14° and 21.62 ± 0.16°, respectively. In native AoR, tilt angle and rotation were minimal at ejection, 14.34 ± 0.81° and 18.1 ± 3.20°, respectively, and maximal at diastole, 18.78 ± 0.84° and 21.23 ± 021°, respectively. AoB and STJ had maximal expansion at ejection; 2.59 ± 2.40% and 6.05 ± 0.66 for Yacoub and 3.75 ± 0.66% and 3.08 ± 0.24% for Yacoub with annuloplasty. In native AoR, the expansion at ejection for AoB was 7.13 ± 2.68% and for STJ was 16.42 ± 0.63%.

Conclusions: AoB annuloplasty reduces AoB deformation and has an impact on STJ dynamics. In both the Yacoub AoR modalities, during ejection, the AoR takes on more of a cone-like geometry, whereas in native AoR, it is of a cylinder-like shape.
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http://dx.doi.org/10.1016/j.jss.2017.12.021DOI Listing
May 2018

Impact of the bicuspid aortic valve on aortic root haemodynamics: three-dimensional computed fluid dynamics simulation.

Interact Cardiovasc Thorac Surg 2018 09;27(3):446-454

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Objectives: The aim was to evaluate the impact of a bicuspid aortic valve (BAV) on local shear stress and on the pressure profile on the elements of the aortic root (AoR).

Methods: The experiment setup included a BAV with aortic valve stenosis (n = 5 pigs, 67 ± 3.5 kg) and insufficiency (n = 5 pigs, 66.7 ± 4.4 kg). By implanting 6 high-fidelity microsonometric crystals in each AoR, we determined the 3-dimensional (3D) geometry of the AoR. Experimental and geometric data were used to create a 3D time- and pressure-dependent computed fluid dynamic model of the AoR with the BAV.

Results: 3D AoR geometry was determined by AoR tilt (α) and rotation angle (β). Both values were maximal at the end of diastole: 24.41 ± 1.70° (α) and 20.90 ± 2.11° (β) for BAV with stenosis and 31.92 ± 11.51° (α) and 20.84 ± 9.80° (β) for BAV with insufficiency and minimal at peak ejection 23.42 ± 1.65° (α), 20.38 ± 1.61° (β) for stenosis and 26.62 ± 7.86° (α), 19.79 ± 8.45° (β) for insufficiency. In insufficiency, low shear stress of 0-0.08 Pa and moderate pressure (60-80 mmHg) were present. In BAV with stenosis, low shear stress of 0-0.5 Pa and moderate pressure (0-20 mmHg) were present at diastole; at peak ejection high shear stress >2 Pa and elevated pressure of >80 mmHg were present.

Conclusions: In a BAV with aortic valve stenosis, the haemodynamics are less favourable. The elevated pressure with elevated shear stress may over the long term promote degenerative processes in the leaflets and consequently valve function failure.
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http://dx.doi.org/10.1093/icvts/ivy044DOI Listing
September 2018

Endovascular treatment of non-dissected ascending aorta disease: a systematic review.

Eur J Cardiothorac Surg 2018 02;53(2):317-324

Department of Cardiovascular Surgery, Cardiocentro Ticino Foundation, Lugano, Switzerland.

Severe ascending aorta disease includes aneurysms, pseudoaneurysms (ascending aorta pseudoaneurysms), penetrating aortic ulcers and Type A aortic dissections. Surgical replacement of the aortic root, ascending aorta or aortic arch is the common treatment for severe ascending aortic disease involving the root, the ascending aorta and/or the arch. Despite good surgical results, there is still a risk for morbidity and mortality following surgery for ascending aorta replacement when elderly patients or patients at high risk for surgery are concerned. Less invasive endovascular treatments for ascending aorta repair are under evaluation, and some reports appeared in the available literature in the last decade. However, clinical series or randomized studies are not yet available, and the use of these techniques is still questionable. In this study, we analysed the outcomes of reported cases of endovascular treatment for ascending aorta disease, excluding Type A aortic dissection. We reviewed reports published until February 2017, and we evaluated the employed technology, the devices, the procedural steps and the outcomes. A total of 26 articles reported 67 patients (mean age 65 ± 17 years) who received endovascular treatment for ascending aorta disease: aneurysms, ascending aorta pseudoaneurysms, penetrating aortic ulcers, intramural haematoma, thrombosis, iatrogenic coarctation and aortic rupture. Complications included endoleak (9 cases), stroke (3 cases), non-ST-elevation myocardial infarction (1 case) and splenic infarction (1 case). Three patients required conversion to open surgery, and 1 patient underwent endovascular reintervention. Early mortality was 2.9%. As an alternative treatment for ascending aorta disease in selected high-risk patients, the endovascular repair will gain popularity, but further analysis is required.
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http://dx.doi.org/10.1093/ejcts/ezx308DOI Listing
February 2018

Long-term Outcomes of a Telementoring Program for Distant Teaching of Endovascular Aneurysm Repair.

J Endovasc Ther 2017 Dec 11;24(6):852-858. Epub 2017 Sep 11.

7 Cardiovascular Research Division, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.

Purpose: To prospectively evaluate the long-term outcomes after a telementoring program for distant teaching of endovascular aneurysm repair (EVAR) and the degree of EVAR procedure assimilation into routine practice.

Methods: A telementoring protocol using stepwise introduction of EVAR was implemented between a university care center and a remote vascular health care site; from March 1999 to October 2003, 49 EVAR patients (mean age 72 years; 48 men) were treated during telementoring at the remote center. After the telementoring period, 86 patients (mean age 71 years; 77 men) underwent EVAR procedures carried out at the secondary care center from November 2003 to July 2011. The long-term outcomes were compared between the EVAR procedures performed during telementoring with the procedures performed independently thereafter.

Results: No significant difference was appreciated between telementored and not telementored procedures either in 30-day mortality (4.1% vs 2.3%, p=0.621) or in the initial technical success (93.9% vs 97.7%, p=0.353). The telementored group showed no significant difference in overall aneurysm-related mortality (6.1% vs 2.3%, p=0.353) or in the overall complication rates (p=0.985). The reintervention rate was significantly lower among the unmentored procedures (11.6% vs 32.7%, p=0.004). In particular, significantly fewer patients underwent late endovascular procedures (1.2% vs 12.2%, p=0.009) and late percutaneous interventions (7.0% vs 20.4%, p=0.027) after telementoring ceased.

Conclusion: The telementoring program followed here allowed excellent EVAR skill assimilation into the routine practice of a remote health care site. Telementoring is a feasible strategy to support skill introduction in remote medical facilities.
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http://dx.doi.org/10.1177/1526602817730841DOI Listing
December 2017

Aortic Valve Pathology as a Predictive Factor for Acute Aortic Dissection.

Ann Thorac Surg 2017 Oct 3;104(4):1340-1348. Epub 2017 Jun 3.

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne.

Background: In this study, the effect of aortic valve (AV) pathology on local hemodynamic conditions was evaluated as a potential trigger for the onset of acute type A and B aortic dissection.

Methods: A time- and pressure-related four-dimensional (4-D) computed fluid dynamic model of the aorta was established. In an experimental setup, AV stenosis and AV insufficiency were created. 4-D pressure-related geometry of the aortic root (AR) with valve insufficiency and valve stenosis were determined by high-fidelity (200 Hz) microsonometric crystals. Flow and pressure were obtained at the left ventricle, ascending aorta, and aortic arch.

Results: Expansion of the AR in AV insufficiency was higher with expansion in AV stenosis, at peak ejection, and at the end of systole. In AV insufficiency, there was low shear stress (0 to 0.6 Pa), turbulent flow, and high pressure (80 to 95 mm Hg) at the anterior wall of the ascending aorta, at the proximal aortic arch, and at the aortic isthmus. In stenosis, high shear stress (>2 Pa) and high pressure (>95 mm Hg) were found at the ascending aorta and at the bifurcation of the brachiocephalic trunk.

Conclusions: In AV insufficiency, low shear stresses and turbulent flow regions were documented at the traditional levels of entry tears for acute type A and B dissection. In AV stenosis, high shear stress with elevated pressure at the ascending aorta may be a trigger element for vessel dilatation, aneurysm formation, and intimal tear, which is typical for type A aortic dissection.
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http://dx.doi.org/10.1016/j.athoracsur.2017.02.076DOI Listing
October 2017

Apical closure device for full-percutaneous transapical valve implantation: stress-test in an animal model†.

Interact Cardiovasc Thorac Surg 2017 05;24(5):721-726

Cardiovascular Research Unit, University of Lausanne, Lausanne, Switzerland.

Objectives: Transapical valve implantation is traditionally performed through a left antero-lateral mini-thoracotomy. A self-expandable apical closure device has recently been developed for full-percutaneous transapical valve implantation. We performed haemodynamics stress-tests on an animal model to evaluate the sealing properties.

Methods: Under general anaesthesia 5 pigs (mean weight: 67 ± 6 Kg) received full heparinization (100 IU/Kg; activated clotting time >250 s and, through inferior mini-sternotomies, 21-Fr introducer sheaths for transapical aortic valve implantation (outer diameter: 25-Fr) were placed over-the-wire in the apexes. Delivery-catheters carrying folded occluders (SAFEX TM final design) were inserted in the introducer sheaths and plugs were then deployed under fluoroscopic guidance. Phase 1: after protamine injection, apical bleeding was monitored for 1 h with standard haemodynamics condition. Phase 2: we induced systemic hypertension with adrenaline infusion to test the sealing properties under stress. Animals were sacrificed after Phase 2 and hearts were removed and inspected.

Results: Five plugs were successfully introduced and deployed in 5 pig hearts. Plugs provided good apical sealing in each animal and a mean of 7 ± 4 ml of blood lost per animal was collected during Phase 1: haemodynamics remained stable and no plug dislodgement was detected (mean blood pressure: 52 ± 9 mmHg). During Phase 2, mean systolic and diastolic peak levels reached 268 ± 24 mmHg and 175 ± 17 mmHg, respectively, without plug dislodgment or bleeding. Post-mortem inspection showed good plug deployment and fixation without myocardial damage.

Conclusions: The new apical occluder seals large-sized apical access sites in animal models also during induced systemic hypertension. This pilot study is a further step towards full-percutaneous transapical valve procedures in the clinical setting.
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http://dx.doi.org/10.1093/icvts/ivw433DOI Listing
May 2017

Impact of synthetic elements on aortic root haemodynamics: computed fluid dynamics of aortic root reconstruction and valve reimplantation.

Eur J Cardiothorac Surg 2017 03;51(3):432-441

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Objectives: The aim was to evaluate the impact of the aortic valve reimplantation (David) and of the aortic root (AoR) remodelling (Yacoub) on the AoR haemodynamics.

Methods: In an experimental setup where the clinical scenario of Yacoub, ( n =  5, domestic pig) and of David ( n =  5, domestic pig) procedure was performed in each AoR, six high-fidelity (200 Hz) sonomicrometric crystals were implanted. Crystals were positioned at three commissures with their projection at the root base. In post-measurement processing 3D deformation of both AoR was determined and used for computed fluid dynamic modelling in order to evaluate pressure, velocity and shear stress profiles.

Results: In David AoR: high pressure (> 150 mmHg) and low to moderate shear stress (0-30 Pa) were found from the period of isovolemic contraction to the closure of the aortic valve. At mid diastole pressure augmentation (> 120 mmHg) a low shear stress (0-10 Pa) was registered at the leaflets, three commissures, and intervalvular triangles. In Yacoub AoR: high pressure (110-130 mmHg) with moderate low shear stress (0-30 Pa) was only registered at isovolemic contraction.

Conclusions: The results show that haemodynamic conditions following a David procedure have a less favourable pattern as compared to a Yacoub AoR. In David AoR, high pressure and low shear stress are present during 2/3 of the cardiac cycle, whereas in Yacoub root, these conditions are present only for a short period of isovolemic contraction.
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http://dx.doi.org/10.1093/ejcts/ezw347DOI Listing
March 2017

Sildenafil attenuates hypoxic pulmonary remodelling by inhibiting bone marrow progenitor cells.

J Cell Mol Med 2017 05 18;21(5):871-880. Epub 2016 Nov 18.

Laboratory of Cardiovascular Research, Department of Surgery and Anesthesiology, University Hospital Lausanne, Lausanne, Switzerland.

The recruitment of bone marrow (BM)-derived progenitor cells to the lung is related to pulmonary remodelling and the pathogenesis of pulmonary hypertension (PH). Although sildenafil is a known target in PH treatment, the underlying molecular mechanism is still elusive. To test the hypothesis that the therapeutic effect of sildenafil is linked to the reduced recruitment of BM-derived progenitor cells, we induced pulmonary remodelling in rats by two-week exposure to chronic hypoxia (CH, 10% oxygen), a trigger of BM-derived progenitor cells. Rats were treated with either placebo (saline) or sildenafil (1.4 mg/kg/day ip) during CH. Control rats were kept in room air (21% oxygen) with no treatment. As expected, sildenafil attenuated the CH-induced increase in right ventricular systolic pressure and right ventricular hypertrophy. However, sildenafil suppressed the CH-induced increase in c-kit cells in the adventitia of pulmonary arteries. Moreover, sildenafil reduced the number of c-kit cells that colocalize with tyrosine kinase receptor 2 (VEGF-R2) and CD68 (a marker for macrophages), indicating a positive effect on moderating hypoxia-induced smooth muscle cell proliferation and inflammation without affecting the pulmonary levels of hypoxia-inducible factor (HIF)-1α. Furthermore, sildenafil depressed the number of CXCR4 cells. Collectively, these findings indicate that the improvement in pulmonary haemodynamic by sildenafil is linked to decreased recruitment of BM-derived c-kit cells in the pulmonary tissue. The attenuation of the recruitment of BM-derived c-kit cells by sildenafil may provide novel therapeutic insights into the control of pulmonary remodelling.
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http://dx.doi.org/10.1111/jcmm.13026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5387166PMC
May 2017

How can cardiothoracic and vascular medical devices stay in the market?

Interact Cardiovasc Thorac Surg 2016 12 11;23(6):940-948. Epub 2016 Aug 11.

Department of Surgery and Cancer, Imperial College London, St Mary's Hospital, London, UK.

Surgeons, as the consumers, must engage in commercial activity regarding medical devices since it directly has impacts on surgical practice and patient outcomes. Unique features defy traditional economic convention in this specific market partly because consumers do not usually pay directly. Greater involvement with commercial activity means better post-market surveillance of medical devices which leads to improved patient safety. The medical device industry has exhibited astonishing levels of growth and profitability reaching $398 billion on a global scale with new product development focusing on unmet clinical need. The industry has rapidly emerged within the context of an ageing population and a global surge in healthcare spending. But the market remains fragmented. The split of consumer, purchaser and payer leads to clinical need driving demand for new product development. This demand contributes to potentially large profit margins mainly contained by regulatory burden and liability issues. Demographic trends, prevalence of diseases and a huge capacity to absorb technology have sustained near unparalleled growth. To stay in the market, incremental development over the short term is essentially aided by responsiveness to demand. Disruptive product development is now more likely to come from multinational companies, in an increasingly expensive, regulated industry. Understanding healthcare organization can help explain the highly complex process of diffusion of innovations in healthcare that include medical devices. The time has come for surgeons to become actively involved with all aspects of the medical device life cycle including commercial activity and post-market surveillance. This is vital for improving patient care and ensuring patient safety.
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http://dx.doi.org/10.1093/icvts/ivw257DOI Listing
December 2016

Aortic root haemodynamics following David procedure: numerical analysis of 3-dimensional haemodynamics.

Eur J Cardiothorac Surg 2016 Jun 19;49(6):1588-98. Epub 2016 Jan 19.

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Objectives: The aim was to determine 3-dimensional (3D) geometrical deformation of the aortic root (AoR) following the David procedure in order to evaluate local haemodynamical conditions of individual AoR elements.

Methods: In the experimental set-up, the David procedure was performed on 10 domestic pigs. Data were compared with the measurements obtained in 10 native AoRs. In each AoR, six high-resolution ultrasonometric crystals (200 Hz) were implanted, being positioned at each commissure and at the AoR base. 3D geometrical deformation of the AoR, torsion and tilt angle was determined. Computed fluid dynamics (CFD) simulation analysis was used to evaluate local pressure, flow and shear stress.

Results: In David AoRs, the tilt angle was maximal at a peak ejection of 25.9 ± 1.49° and minimal at the end of isovolemic contraction at 23.5 ± 0.80°. David root rotation was maximal at a peak ejection of 27.93 ± 1.54° and minimal at the end of the isovolemic contraction at 25.7 ± 1.32°. In the native AoR, the opposite was observed. Here, the tilt and rotation angle were maximal at the end of isovolemic contraction (17.25 ± 0.68° and 19.71 ± 0.73°) and decreased to its minimal values at peak ejections (14.1 ± 0.62° and 16.33 ± 0.47°). In David AoR, high pressure (>140 mmHg) combined with low-to-moderate shear stress (0-40 Pa) was found at the leaflet body from the beginning of isovolemic contraction till the opening of the aortic valve. Similar high pressure (>140 mmHg) and shear stress (0-40 Pa) were found in the period from aortic valve closure till the beginning of the isovolemic contraction. In native AoRs, high pressure (>95 mmHg) was conjoined with low-to-moderate shear stress (0-30 Pa) at the leaflets and was registered at the end of isovolemic contraction.

Conclusions: The David AoR is haemodynamically less favourable when compared with the native AoR. During almost two-thirds of the time period of the cardiac cycle, AoR elements are exposed to high pressure and low shear stress. In contrast, in native AoRs, similar conditions were present only during the short period of isovolemic contraction.
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http://dx.doi.org/10.1093/ejcts/ezv427DOI Listing
June 2016

Numerical analysis of the 3-dimensional aortic root morphology during the cardiac cycle.

Eur J Cardiothorac Surg 2016 Apr 9;49(4):1213-21. Epub 2015 Sep 9.

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Objectives: The aim was to define the 3-dimensional (3D) geometrical changes of the aortic root and to determine the local shear stress profile of aortic root elements during the cardiac cycle.

Methods: Six sonomicrometric crystals (200 Hz) were implanted into the aortic root of five pigs at the commissures and at the aortic root base (AoB). 3D aortic root deformation including volume, torsion and tilt angle were determined. Geometrical data with measured local flow and pressure conditions was used for computed fluid dynamics modelling of the aortic root.

Results: Compared with end-diastole, the sinotubular junction and AoB have maximal expansion at peak ejection: 16.42 ± 6.36 and 7.60 ± 2.52%, and minimal at isovolaemic relaxation: 2.87 ± 1.62 and 1.85 ± 1.79%. Aortic root tilt and rotation angle were maximal at the end of diastole: 17.7 ± 8.8 and 21.2 ± 2.09°, and decreased to 15.24 ± 8.14 and 18.3 ± 0.1.94° at peak ejection. High shear stress >20 Pa was registered at peak ejection at coaptations, and during diastole at the superior two-thirds of the leaflets and intervalvular triangles (IVTs). The leaflet body, inferior one-third of the IVTs and valve nadir were exposed to moderate shear stress (8-16 Pa) during the cardiac cycle.

Conclusions: Aortic root geometry demonstrates precise 3D changes of tilt and rotation angle. Reduction of angles during ejection results in a straight cylinder with low shear stress that facilitates the ejection; the increase during diastole results in a tilted frustum with elevated shear stress. Findings can be used for comparative analysis of native and synthetic structures with individual compliance.
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http://dx.doi.org/10.1093/ejcts/ezv295DOI Listing
April 2016

Apical closure device for transapical valve procedures.

Interact Cardiovasc Thorac Surg 2015 Nov 11;21(5):561-4. Epub 2015 Aug 11.

Cardiovascular Research Unit, University of Lausanne, Lausanne, Switzerland.

Objectives: Transapical transcatheter valve procedures are performed through a left minithoracotomy and require apical sutures to seal the apical access site. The use of large-calibre devices compromises any attempt to fully perform the procedure with a thoracoscopic approach or percutaneously. We report our preliminary experience in animals with a new sutureless self-expandable apical occluder, engineered to perform transapical access site closure in a minimally invasive setting with large-size introducer sheaths.

Methods: The apical occluder with extendable waist was implanted in six young pigs during an acute animal study. Under general anaesthesia, animals (mean weight: 62 ± 8 kg) received full heparinization (heparin: 100 UI/kg; activated clotting time above 250 s). Through a median sternotomy, a 21-Fr Certitude™ introducer sheath (outer diameter: 25 Fr) was placed over the wire into the cardiac apex. The delivery catheter carrying the constrained apical plug was inserted into the sheath and deployed under fluoroscopic control, whereas the Certitude™ was retrieved. After protamine infusion, we observed and recorded the 1-h bleeding with standard haemodynamic parameters. Animals were sacrificed, and hearts analysed.

Results: Six apical closure devices were successfully introduced and deployed in six pig hearts through large-size apical sheaths at first attempt. In all animals, the plugs guaranteed immediate apical sealing and traces of blood were collected in the pericardium during the 1-h observational period (mean of 16 ± 3.4 ml of blood loss per animal). Haemodynamic parameters remained stable during the entire study period and no plug dislodgement was detected with normal systemic blood pressure (mean arterial mean blood pressure: 65 ± 7 mmHg). Post-mortem analysis confirmed the full deployment and good fixation of all plugs, without macroscopic damages to the surrounding myocardium.

Conclusions: This sutureless self-expandable apical occluder is a simple device capable of sealing large-size apical access sites (20-35 Fr) in an acute animal study. This approach is a step further towards less invasive transapical valve procedures in the clinical setting, and further animal tests will be performed to confirm the long-term efficacy and safety of this device.
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http://dx.doi.org/10.1093/icvts/ivv225DOI Listing
November 2015

Analysis of flow dynamics in right ventricular outflow tract.

J Surg Res 2015 Jul 14;197(1):50-7. Epub 2015 Mar 14.

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Background: The mechanism behind early graft failure after right ventricular outflow tract (RVOT) reconstruction is not fully understood. Our aim was to establish a three-dimensional computational fluid dynamics (CFD) model of RVOT to investigate the hemodynamic conditions that may trigger the development of intimal hyperplasia and arteriosclerosis.

Methods: Pressure, flow, and diameter at the RVOT, pulmonary artery (PA), bifurcation of the PA, and left and right PAs were measured in 10 normal pigs with a mean weight of 24.8 ± 0.78 kg. Data obtained from the experimental scenario were used for CFD simulation of pressure, flow, and shear stress profile from the RVOT to the left and right PAs.

Results: Using experimental data, a CFD model was obtained for 2.0 and 2.5-L/min pulsatile inflow profiles. In both velocity profiles, time and space averaged in the low-shear stress profile range from 0-6.0 Pa at the pulmonary trunk, its bifurcation, and at the openings of both PAs. These low-shear stress areas were accompanied to high-pressure regions 14.0-20.0 mm Hg (1866.2-2666 Pa). Flow analysis revealed a turbulent flow at the PA bifurcation and ostia of both PAs.

Conclusions: Identified local low-shear stress, high pressure, and turbulent flow correspond to a well-defined trigger pattern for the development of intimal hyperplasia and arteriosclerosis. As such, this real-time three-dimensional CFD model may in the future serve as a tool for the planning of RVOT reconstruction, its analysis, and prediction of outcome.
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http://dx.doi.org/10.1016/j.jss.2015.03.001DOI Listing
July 2015

Fluid dynamics simulation of right ventricular outflow tract oversizing.

Interact Cardiovasc Thorac Surg 2015 Aug 26;21(2):176-82. Epub 2015 Apr 26.

Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland.

Objectives: Repair of the right ventricular outflow tract (RVOT) in paediatric cardiac surgery remains challenging due to the high reoperation rate. Intimal hyperplasia and consequent arteriosclerosis is one of the most important limitation factors for graft durability. Since local shear stress and pressure are predictive elements for intimal hyperplasia and wall degeneration, we sought to determine in an oversized 12-mm RVOT model, with computed fluid dynamics simulation, the local haemodynamical factors that may explain intimal hyperplasia. This was done with the aim of identifying the optimal degree of oversizing for a 12-mm native RVOT.

Methods: Twenty domestic pigs, with a weight of 24.6 ± 0.89 kg and a native RVOT diameter of 12 ± 1.7 mm, had valve conduits of 12, 16, 18 and 20 mm implanted. Pressure and flow were measured at 75, 100 and 125% of normal flow at RVOT at the pulmonary artery, pulmonary artery bifurcation and at the left and right pulmonary arteries. Three-dimensional computed fluid dynamics (CFD) simulation in all four geometries in all flow modalities was performed. Local shear stress and pressure conditions were investigated.

Results: Corresponding to 75, 100 and 125% of steady-state flow, three inlet velocity profiles were obtained, 0.2, 0.29 and 0.36 m/s, respectively. At inflow velocity profiles, low shear stress areas, ranged from 0 to 2 Pa, combined with high-pressure areas ranging from 11.5 to 12.1 mmHg that were found at distal anastomosis, at bifurcation and at the ostia of the left and right pulmonary arteries in all geometries.

Conclusions: In all three oversized geometries, the local reparation of shear stress and pressure in the 16-mm model showed a similar local profile as in the native 12 mm RVOT. According to these findings, we suggest oversizing the natural 12-mm RVOT by not more than 4 mm. The elements responsible for wall degeneration and intimal hyperplasia remain very similar to the conditions present in native RVOT.
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http://dx.doi.org/10.1093/icvts/ivv108DOI Listing
August 2015

Late removal of retrievable caval filters.

Swiss Med Wkly 2014 6;144:w14022. Epub 2014 Nov 6.

Cardio-Vascular Research, Department of Surgery and Anaesthesiology, Lausanne, Switzerland.

The advent of retrievable caval filters was a game changer in the sense, that the previously irreversible act of implanting a medical device into the main venous blood stream of the body requiring careful evaluation of the pros and cons prior to execution suddenly became a "reversible" procedure where potential hazards in the late future of the patient lost most of their weight at the time of decision making. This review was designed to assess the rate of success with late retrieval of so called retrievable caval filters in order to get some indication about reasonable implant duration with respect to relatively "easy" implant removal with conventional means, i.e., catheters, hooks and lassos. A PubMed search (www.pubmed.gov) was performed with the search term "cava filter retrieval after 30 days clinical", and 20 reports between 1994 and 2013 dealing with late retrieval of caval filters were identified, covering approximately 7,000 devices with 600 removed filters. The maximal duration of implant reported is 2,599 days and the maximal implant duration of removed filters is also 2,599 days. The maximal duration reported with standard retrieval techniques, i.e., catheter, hook and/or lasso, is 475 days, whereas for the retrievals after this period more sophisticated techniques including lasers, etc. were required. The maximal implant duration for series with 100% retrieval accounts for 84 days, which is equivalent to 12 weeks or almost 3 months. We conclude that retrievable caval filters often become permanent despite the initial decision of temporary use. However, such "forgotten" retrievable devices can still be removed with a great chance of success up to three months after implantation. Conventional percutaneous removal techniques may be sufficient up to sixteen months after implantation whereas more sophisticated catheter techniques have been shown to be successful up to 83 months or more than seven years of implant duration. Tilting, migrating, or misplaced devices should be removed early on, and replaced if indicated with a device which is both, efficient and retrievable.
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http://dx.doi.org/10.4414/smw.2014.14022DOI Listing
May 2015

Venous cannula performance assessment in a realistic caval tree model.

Interact Cardiovasc Thorac Surg 2015 Feb 2;20(2):194-9. Epub 2014 Nov 2.

Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.

Objectives: A new caval tree system was designed for realistic in vitro simulation. The objective of our study was to assess cannula performance for virtually wall-less versus standard percutaneous thin-walled venous cannulas in a setting of venous collapse in case of negative pressure.

Methods: For a collapsible caval model, a very flexible plastic material was selected, and a model with nine afferent veins was designed according to the anatomy of the vena cava. A flow bench was built including a lower reservoir holding the caval tree, built by taking into account the main afferent vessels and their flow provided by a reservoir 6 cm above. A cannula was inserted in this caval tree and connected to a centrifugal pump that, in turn, was connected to a reservoir positioned 83 cm above the second lower reservoir (after-load = 60 mmHg). Using the same pre-load, the simulated venous drainage for cardiopulmonary bypass was realized using a 24 F wall-less cannula (Smartcanula) and 25 F percutaneous cannula (Biomedicus), and stepwise increased augmentation (1500 RPM, 2000 and 2500 RPM) of venous drainage.

Results: For the thin wall and the wall-less cannulas, 36 pairs of flow and pressure measurements were realized for three different RPM values. The mean Q-values at 1500, 2000 and 2500 RPM were: 3.98 ± 0.01, 6.27 ± 0.02 and 9.81 ± 0.02 l/min for the wall-less cannula (P <0.0001), versus 2.74 ± 0.02, 3.06 ± 0.05, 6.78 ± 0.02 l/min for the thin-wall cannula (P <0.0001). The corresponding inlet pressure values were: -8.88 ± 0.01, -23.69 ± 0.81 and -70.22 ± 0.18 mmHg for the wall-less cannula (P <0.0001), versus -36.69 ± 1.88, -80.85 ± 1.71 and -101.83 ± 0.45 mmHg for the thin-wall cannula (P <0.0001). The thin-wall cannula showed mean Q-values 37% less and mean P values 26% more when compared with the wall-less cannula (P <0.0001).

Conclusions: Our in vitro water test was able to mimic a negative pressure situation, where the wall-less cannula design performs better compared with the traditional thin-wall cannula.
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http://dx.doi.org/10.1093/icvts/ivu318DOI Listing
February 2015

Long-term outcome of congenital aortic valve stenosis: predictors of reintervention.

Cardiol Young 2015 Jun 1;25(5):893-902. Epub 2014 Jul 1.

1Department of Cardiovascular Surgery,University Hospital,Lausanne,Switzerland.

Objectives: To evaluate long-term outcome of initial aortic valve intervention in a paediatric population with congenital aortic stenosis, and to determine risk factors associated with reintervention.

Patients And Methods: From 1985 to 2009, 77 patients with congenital aortic stenosis and a mean age of 5.8±5.6 years at diagnosis were followed up in our institution for 14.8±9.1 years.

Results: First intervention was successful with 86% of patients having a residual peak aortic gradient 1 regurgitation increased by 7%. Long-term survival after the first procedure was excellent, with 91% survival at 25 years. At a mean interval of 7.6±5.3 years, 30 patients required a reintervention (39%), mainly because of a recurrent aortic stenosis. Freedom from reintervention was 97, 89, 75, 53, and 42% at 1, 10, 15, 20, and 25 years, respectively. Predictors of reintervention were residual peak aortic gradient (p=0.0001), aortic regurgitation post-intervention >1 (p=0.02), prior balloon aortic valvuloplasty (p=0.04), and increased left ventricular posterior wall thickness (p=0.1).

Conclusions: Aortic valve intervention is a safe and effective procedure for congenital aortic stenosis with excellent survival results. However, rate of reintervention is high and influenced by increased left ventricular posterior wall thickness pre-intervention, prior balloon valvuloplasty, higher residual peak systolic valve gradient, and more than mild regurgitation post-intervention. The study highlights that long-term follow-up is recommended for these patients.
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http://dx.doi.org/10.1017/S1047951114001085DOI Listing
June 2015

Computational fluid dynamics of the right ventricular outflow tract and of the pulmonary artery: a bench model of flow dynamics.

Interact Cardiovasc Thorac Surg 2014 Oct 19;19(4):611-6. Epub 2014 Jun 19.

Department of Cardiovascular Surgery, University Hospital Lausanne, Lausanne, Switzerland

Objectives: The reconstruction of the right ventricular outflow tract (RVOT) with valved conduits remains a challenge. The reoperation rate at 5 years can be as high as 25% and depends on age, type of conduit, conduit diameter and principal heart malformation. The aim of this study is to provide a bench model with computer fluid dynamics to analyse the haemodynamics of the RVOT, pulmonary artery, its bifurcation, and left and right pulmonary arteries that in the future may serve as a tool for analysis and prediction of outcome following RVOT reconstruction.

Methods: Pressure, flow and diameter at the RVOT, pulmonary artery, bifurcation of the pulmonary artery, and left and right pulmonary arteries were measured in five normal pigs with a mean weight of 24.6 ± 0.89 kg. Data obtained were used for a 3D computer fluid-dynamics simulation of flow conditions, focusing on the pressure, flow and shear stress profile of the pulmonary trunk to the level of the left and right pulmonary arteries.

Results: Three inlet steady flow profiles were obtained at 0.2, 0.29 and 0.36 m/s that correspond to the flow rates of 1.5, 2.0 and 2.5 l/min flow at the RVOT. The flow velocity profile was constant at the RVOT down to the bifurcation and decreased at the left and right pulmonary arteries. In all three inlet velocity profiles, low sheer stress and low-velocity areas were detected along the left wall of the pulmonary artery, at the pulmonary artery bifurcation and at the ostia of both pulmonary arteries.

Conclusions: This computed fluid real-time model provides us with a realistic picture of fluid dynamics in the pulmonary tract area. Deep shear stress areas correspond to a turbulent flow profile that is a predictive factor for the development of vessel wall arteriosclerosis. We believe that this bench model may be a useful tool for further evaluation of RVOT pathology following surgical reconstructions.
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http://dx.doi.org/10.1093/icvts/ivu202DOI Listing
October 2014

Ross procedure: is the root replacement technique superior to the sub-coronary implantation technique? Long-term results.

Eur J Cardiothorac Surg 2014 Dec 24;46(6):944-51. Epub 2014 Apr 24.

Department of Surgery and Anesthesiology, Cardio-Vascular Research, University Hospital Lausanne, Lausanne, Switzerland.

There is controversy over the use of the Ross procedure with regard to the sub-coronary and root replacement technique and its long-term durability. A systematic review of the literature may provide insight into the outcomes of these two surgical subvariants. A systematic review of reports between 1967 and February 2013 on sub-coronary and root replacement Ross procedures was undertaken. Twenty-four articles were included and divided into (i) sub-coronary technique and (ii) root replacement technique. The 10-year survival rate for a mixed-patient population in the sub-coronary procedure was 87.3% with a 95% confidence interval (CI) of 79.7-93.4 and 89.1% (95% CI, 85.3-92.1) in the root replacement technique category. For adults, it was 94 vs 95.3% (CI, 88.9-98.1) and in the paediatric series it was 90 vs 92.7% (CI, 86.9-96.0), respectively. Freedom from reoperation at 10 years was, in the mixed population, 83.3% (95% CI, 69.9-93.4) and 93.3% (95% CI, 89.4-95.9) for sub-coronary versus root replacement technique, respectively. In adults, it was 98 vs 91.2% (95% CI, 82.4-295.8), and in the paediatric series 93.3 vs 92.0% (95% CI, 86.1-96.5) for sub-coronary versus root replacement technique, respectively. The Ross procedure arguably has satisfactory results over 5 and 10 years for both adults and children. The results do not support the advantages of the sub-coronary technique over the root replacement technique. Root replacement was of benefit to patients undergoing reoperations on neoaorta and for long-term survival in mixed series.
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http://dx.doi.org/10.1093/ejcts/ezu176DOI Listing
December 2014

Caval collapse during cardiopulmonary bypass: a reproducible bench model.

Eur J Cardiothorac Surg 2014 Aug 14;46(2):306-12. Epub 2014 Jan 14.

Cardio-Vascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.

Objectives: During open heart surgery, so-called atrial chatter, a phenomenon due to right atria and/or caval collapse, is frequently observed. Collapse of the cava axis during cardiopulmonary bypass (CPB) limits venous drainage and may result downstream in reduced pump flow on (lack of volume) and upstream in increased after-load (stagnation), which in turn may both result in reduced or even inadequate end-organ perfusion. The goal of this study was to reproduce venous collapse in the flow bench.

Methods: In accordance with literature for venous anatomy, a caval tree system is designed (polyethylene, thickness 0.061 mm), which receives venous inflow from nine afferent veins. With water as medium and a preload of 4.4 mmHg, the system has an outflow of 4500 ml/min (Scenario A). After the insertion of a percutaneous venous cannula (23-Fr), the venous model is continuously served by the afferent branches in a venous test bench and venous drainage is augmented with a centrifugal pump (Scenario B).

Results: With gravity drainage (siphon: A), spontaneously reversible atrial chatter can be generated in reproducible fashion. Slight reduction in the outflow diameter allows for generation of continuous flow. With augmentation (B), irreversible collapse of the artificial vena cava occurs in reproducible fashion at a given pump speed of 2300 ± 50 RPM and a pump inlet pressure of -112 mmHg. Furthermore, bubbles form at the cannula tip despite the fact that the entire system is immersed in water and air from the environment cannot enter the system. This phenomenon is also known as cavitation and should be avoided because of local damage of both formed blood elements and endothelium, as well embolization.

Conclusions: This caval model provides a realistic picture for the limitations of flow due to spontaneously reversible atrial chatter vs irreversible venous collapse for a given negative pressure during CPB. Temporary interruption of negative pressure in the venous line can allow for recovery of venous drainage. This know-how can be used not only for testing different cannula designs, but also for further optimizing perfusion strategies.
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http://dx.doi.org/10.1093/ejcts/ezt620DOI Listing
August 2014

Incidence and risk factors for Contegra graft infection following right ventricular outflow tract reconstruction: long-term results.

Eur J Cardiothorac Surg 2014 Jun 10;45(6):1070-4. Epub 2014 Jan 10.

Department of Cardiovascular Surgery, University Hospital, Lausanne, Switzerland

Objectives: The aim of this study was to evaluate the risk factors associated with Contegra graft (Medtronic Minneapolis, MN, USA) infection after reconstruction of the right ventricular outflow tract.

Methods: One hundred and six Contegra grafts were implanted between April 1999 and April 2010 for the Ross procedure (n = 46), isolated pulmonary valve replacement (n = 32), tetralogy of Fallot (n = 24), double-outlet right ventricle (n = 7), troncus arteriosus (n = 4), switch operation (n = 1) and redo of pulmonary valve replacement (n = 2). The median age of the patients was 13 years (range 0-54 years). A follow-up was completed in all cases with a median duration of 7.6 years (range 1.7-12.7 years).

Results: There were 3 cases of in-hospital mortality. The survival rate during 7 years was 95.7%. Despite the lifelong endocarditis prophylaxis, Contegra graft infection was diagnosed in 12 (11.3%) patients at a median time of 4.4 years (ranging from 0.4 to 8.7 years). Univariate analysis of preoperative, perioperative and postoperative variables was performed and the following risk factors for time to infection were identified: female gender with a hazard ratio (HR) of 0.19 (P = 0.042), systemic-to-pulmonary shunt (HR 6.46, P < 0.01), hypothermia (HR 0.79, P = 0.014), postoperative renal insufficiency (HR 11.97, P = 0.015) and implantation of permanent pacemaker during hospitalization (HR 5.29, P = 0.075). In 2 cases, conservative therapy was successful and, in 10 patients, replacement of the infected valve was performed. The Contegra graft was replaced by a homograft in 2 cases and by a new Contegra graft in 8 cases. Cox's proportional hazard model indicated that time to graft infection was significantly associated with tetralogy of Fallot (HR 0.06, P = 0.01), systemic-to-pulmonary shunt (HR 64.71, P < 0.01) and hypothermia (HR 0.77, P < 0.01).

Conclusion: Contegra graft infection affected 11.3% of cases in our cohort, and thus may be considered as a frequent entity that can be predicted by both intraoperative and early postoperative factors. After the diagnosis of infection associated with the Contegra graft was confirmed, surgical treatment was the therapy of choice.
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http://dx.doi.org/10.1093/ejcts/ezt579DOI Listing
June 2014
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