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Biomedical subjects

B Meyns

Publications and source records attributed to B Meyns.

At least 19 recordsLinked to original sources
PubMed2006

Stenting of hypoplastic aortic segments with mild pressure gradients and arterial hypertension.

OBJECTIVE: To determine the safety, feasibility and effectiveness of stent expansion of hypoplastic aortic segments with pressure gradients in patients with arterial hypertension. DESIGN: Non-randomised prospective clinical trial. SETTING: Tertiary referral centre, congenital cardiac unit. PATIENT SELECTION: 20 consecutive patients (median age 14.5 years, range 11.6-38.8 years) with arterial hypertension and a hypoplastic segment of the aorta. Seventeen patients had successful previous arch interventions in a coarctation site. INTERVENTIONS: Stent deployment in hypoplastic arch segments. MAIN OUTCOME MEASURES: Gradient across the aortic arch; complications early and during follow up; residual hypertension. RESULTS: 23 stents were deployed: 13 in the cross and 10 in the isthmus. The mean gradient across the aortic arch decreased from 16 (SD 6) (median 17) to 3 (4) (median 1) mm Hg (p < 0.001). In a few patients a mild gradient persisted just distal to the left carotid artery due to residual orificial narrowing or acute angulation. No complications occurred during or after the procedure. During follow up of 2.2 years (range 0.2-4.8 years) arterial hypertension resolved in 10 patients and 10 required residual drug treatment with better control of blood pressures. CONCLUSIONS: Pressure loss due to residual hypoplastic aortic segments can be treated effectively and safely with stent expansion. Some patients remain mildly hypertensive and require additional drug treatment.

Adolescent↗
PubMed2006

In vitro set-up of modified Blalock Taussig shunt: vascular resistance-flow relationship.

BACKGROUND: A modified Blalock-Taussig (mBT) shunt is an anastomosis created between the systemic and pulmonary arterial tree in order to improve pulmonary blood flow in neonates and children with congenital heart disease. The aim of this study was to assess vascular resistance-flow relationship in an in vitro set-up of a modified Blalock Taussig shunt. METHODS: A shunt set-up was constructed with the vessels of a sheep. A modified BT shunt was anastomosed between an innominate (brachiocephalic) and a right pulmonary artery. A Medos pump (ventricular assist device) was used to create pulsatile flow. Three different mean pulmonary artery flow rates (Q PA ) were applied. Once mean pulmonary and mean aortic flows (Q AO ) were fixed, shunt flow rates for twelve different pulmonary vascular resistances (R p ) were investigated. RESULTS: For all three pulmonary flow rates, the shunt flow decreased with increasing pulmonary resistance. In addition, systemic flow decreased compared to pulmonary flow. When pulmonary flow rate was set at 800 ml/min and aorta flow rate at 900 ml/min, the distribution of flow between pulmonary and systemic organs flow rates ranged between 69% - 70% and 30% - 31% respectively. Similarly, when both pulmonary and aorta flow rates were set at 900 ml/min, pulmonary and systemic organ flows ranged between 73% - 77% and 23% - 27% respectively. For pulmonary and aorta flow rates of 1000 ml/min and 900 ml/min, respectively, the distribution of flow between pulmonary and systemic organ flow rates varied between 79% - 83% and 17% - 21% respectively. CONCLUSION: Knowledge of the relationship between vascular resistances and flow in this surgically created in vitro mBT shunt set-up may be helpful in the clinical management of the patients whose survival is crucially dependent on the blood flow distribution between the pulmonary and systemic circulation.

Anastomosis, Surgical↗
PubMed2005

Successful extracorporeal lung assistance for overwhelming pneumonia in a patient with undiagnosed full blown aids--a controversial therapy in HIV-patients.

A case is described of overwhelming pneumonia in a patient with a history of coughing since three months. Because of hypoxia and hypercapnia that could not be managed by optimal mechanical ventilation, the patient required urgent extracorporeal lung assistance (ECLA, also known as ECMO). Afterwards the diagnosis of full blown AIDS was made. Appropriate antiviral, antibiotic and antimycotic therapy was successfully established. The patient was weaned from ECLA 4 days later, and discharged from hospital after two months.

AIDS-Related Opportunistic Infections↗
PubMed2005

Plasma leakage of oxygenators in ECMO depends on the type of oxygenator and on patient variables.

This study was conducted to identify the causes of plasma leakage of oxygenators in extra corporeal membrane oxygenation (ECMO). From 1996 through 2002, 91 oxygenators were used in 62 patients undergoing ECMO for respiratory and/or cardiac failure. Several types of oxygenators were used (Medtronic Maxima, Minima, PRF, Medos Hilite). Patient variables and variables related to the ECMO set-up were analysed for their relationship with oxygenator failure by a time related multiple regression analysis (Cox). Oxygenator failure occurred in 26% of the cases. The analysis identified the type of oxygenator (p=0.0016), younger patient age (p=0.04) and the number of oxygenators used (p=0.03) as the independent significant risk factors. The type of oxygenator used has the most overwhelming effect (significantly less leakage with the Medos Hilite). In conclusion, leakage of oxygenators is predominantly caused by the type of oxygenator used. Patient variables (younger age and the number of oxygenators used in one patient) are also significant and allude to an inflammatory process as underlying mechanism of plasma leakage.

Adolescent↗
PubMed2004

Is ABO group incompatibility really the reason of accelerated failure of cryopreserved allografts in very young patients?--Echography assessment of the European Homograft Bank (EHB) cryopreserved allografts used for reconstruction of the right ventricular outflow tract.

Right ventricular outflow tract reconstruction (RVOTR) with cryopreserved allograft for Ross operation and other congenital or acquired cardiac malformation has become a routine and currently, the procedure of choice for children and young patients. A tendency of accelerated degeneration in the youngest recipients has been reported. Some authors advocate the ABO group incompatibility as the main reason for such failure. This retrospective monocentric study presents the long-term outcome of the European Homograft Bank (EHB) cryopreserved allografts, used for RVOTR in Ross operation (group one) and other congenital heart malformation-s (group two). The evaluation of the allograft performance was done by means of echography, considering the allografts with the transvalvular gradient of > or =40 mmHg and/or regurgitation of > or =3+ as failed. Fifty-one patients of group one and 123 of group two were analysed after completed follow-up information. About 25.5% of patients of group one and 30.8% of group two had a compatible, whereas 74.5% of group one and 68.92 of group two an incompatible ABO group with the donor. The mean follow up was 45.77 and 68.88 months, respectively. In second group 22.76% received the aortic, while 77.24% pulmonary allograft. Only three cases of group one (5.88%) failed: one with a compatible (7.69%) and two with an incompatible ABO group (5.26%) (p=0.1), whereas 39 patients (29.4%) of group two failed between 20.1 and 120.2 months (29.73% with and 29.07% without ABO compatibility, p=0.03). Contrary, the age showed more importance in the allograft failure: out of 41 failed allografts, 24 (58.54%) were implanted in patients of 0-5 years (9 or 37.5% with compatible and 15 or 62.5% with incompatible ABO group). Generally, analysing both groups together, there was no influence of ABO mismatching on the allograft failure (p=0.79). Contrary, there was a significant difference in survival between Ross and non-Ross group (p=0.00082).

ABO Blood-Group System↗
PubMed2003

Initial experiences with the Impella device in patients with cardiogenic shock - Impella support for cardiogenic shock.

BACKGROUND: We planned a study to assess the safety, feasibility, and efficacy of the Impella micro-axial blood pump in patients with cardiogenic shock. METHODS: From January 2001 to September 2002 inclusive, 16 patients in cardiogenic shock (maximal inotropic support and with IABP in 11 cases) underwent left ventricle unloading with the Impella pump. 6 were placed via the femoral artery (patients in the coronary care unit) and 10 directly through the aorta (postcardiotomy heart failure). In three patients, the device was used in combination with ECMO. Mean age was 60 years (range 43 - 75), 11 were male. RESULTS: A stable pump flow of 4.24 +/- 0.28 l/min was reached (3.3 +/- 1.9 l/min in patients with ECMO and Impella). Mean blood pressure before Impella) support was 57.4 +/- 13 mmHg, which increased to 74.9 +/- 13 mmHg after 6 hours and 80.6 +/- 17 mmHg (p = 0.003) after 24 hours. Cardiac output increased from 4.1 +/- 1.3 l/min to 5.5 +/- 1.3 (p = 0.003) and 5.9 +/-1.9 l/min (p = 0.01) at 6 and 24 hours. Mean pulmonary wedge pressure decreased from 29 +/- 10 mmHg to 17 +/- 5 mmHg and 18 +/- 7 mmHg at 6 (p = 0.04) and 24 hours. Blood lactate levels decreased significantly after 6 hours of support (from 2.7 +/- 1 to 1.3 +/- 0.5 mmol/l, p = 0.004). Device-related complications included three sensor failures (no clinical action), one pump displacement (replacement) and six incidences of haemolysis (peak free plasma haemoglobin > 100 mg/dl, no clinical action). Eleven patients (68 %) were weaned, six (37 %) survived. CONCLUSIONS: Left ventricular unloading with the Impella pump via the transthoracic or femoral approach is feasible and safe. Support led to a decrease in pulmonary capillary wedge pressure, increase in cardiac output and mean blood pressure, and improved organ perfusion in patients with severe cardiogenic shock.

Adult↗
PubMed2002

Coronary artery bypass grafting supported with intracardiac microaxial pumps versus normothermic cardiopulmonary bypass: a prospective randomized trial.

OBJECTIVE: To analyze the difference in coronary artery bypass grafting (CABG) performed with normothermic cardiopulmonary bypass (CPB) and CABG supported with the intracardiac microaxial pump (ICP, Impella, Aachen, Germany). METHODS: A prospective randomized study was conducted in seven centers. The study population consists of 199 patients undergoing isolated primary CABG (CPB group 94 patients, ICP group 105 patients). Both groups are equal in demographic variables, number of bypasses performed, and Euroscore predicted mortality. We analyzed clinical outcome, myocardial enzymes and blood parameters of hemolysis, organ function and inflammatory response. RESULTS: Seventeen patients (16%), randomized in the ICP group, were switched to the CPB group. This was due to the inability to position the right side catheter adequately (n=8), to a pump failure (n=1) or to the perioperative decision that beating heart surgery is technically not possible (n=8). There was no significant difference between the two study arms regarding the pump assistance time (CPB 67.1+/-22.9 min; ICP 67.7+/-30.3 min; P=0.88861), the number of grafts (CPB 2.4+/-0.7; ICP 2.3+/-0.8) and the number of grafts to the back wall (CFX; both groups n=37). There is no significant difference in clinical outcome, evolution of myocardial enzymes, indices of organ function and hemolysis. There is a reduced inflammatory response in the ICP group as indicated in the postoperative release of granulocyte elastase (CPB 259+/-195; ICP 150+/-126 microg/l; P<0.00001) and complement C3 (CPB 0.73+/-0.2; ICP 0.65+/-0.2g/l; P=0.008). CONCLUSION: The intracardiac pump for the right heart is difficult to introduce. As a consequence the right side pump underwent design modifications. There were no differences in clinical outcome between both groups. The inflammatory response is significantly reduced in the ICP group.

Aged↗
PubMed2002

The heart-pump interaction: effects of a microaxial blood pump.

BACKGROUND: When we use rotary blood pumps as an assist device, an interaction takes place between the pump performance and the native heart function (native heart influences pump performance and vice versa). The interaction between native heart and rotary blood pump can be useful to predict recovery of the failing heart. METHODS: The rotary blood pumps used were microaxial catheter-mounted pumps with an external diameter of 6.4 mm (Impella, Aachen, Germany). The pump-heart interaction was studied in five juvenile sheep with a mean body weight of 68.5 +/- 8.7 kg. The pumps were introduced via the left carotid artery and placed in transvalvular aortic position. Recorded parameters were pump speed (rpm), generated flow (L/min) and differential pressure (mm Hg) obtained at high frequency rate of data recordings (25 sets of data per second). This allowed continuous analysis of the pump performance during cardiac cycle. Under clinical conditions the interaction was studied in a 60-year-old male, in whom the device was applied due to postcardiotomy heart failure after myocardial infarction. RESULTS: Heart-pump interaction was analyzed based on pump flow differential pressure. This relationship, analyzed continuously during cardiac cycle, presents as a loop. The dynamic contribution of the heart to the flow generated by the pump leads to continuous fluctuation in the pressure head and the creation of hysteresis. The improved function of the failing heart under clinical conditions after seven days of mechanical support was expressed by: increased hysteresis of the loop caused by increased gradient of flow generated during cardiac cycle, a more pronounced venticular ejection phase that indicates more dynamic heart contribution to the generated flow, and finally increased gradient of the differential pressure during cardiac cycle, caused predominantly by increased aortic pressure and decreased left ventricle pressure during diastolic phase. CONCLUSIONS: The heart-pump interaction based on the pump flow-differential pressure relationship can be useful in predicting the possibility to wean the patient from the device.

Animals↗
PubMed2002

A new rotary blood pump for versatile extracorporeal circulation: the DeltaStream.

Today, rotary pumps are routinely used for extracorporeal circulation in different clinical settings and applications. A review of these applications and specific limitations in extracorporeal perfusion was performed and served as a basis for the development of the DeltaStream. The DeltaStreams is a miniaturized rotary blood pump of a new and unique design with an integrated drive unit. Despite its small design, the pump maintains a sufficient hydraulic capacity, which makes the DeltaStream very flexible for intra- and perioperative applications. It also opens the field for short-term ventricular assist devices (VAD) applications or use as a component in extracorporeal life support systems (ECLS). The DeltaStream and, specifically, its impeller design have been optimized with respect to haemolysis and nonthrombogenicity. Also, the pump facilitates an effective pulse generation in VAD applications and simulates heart action in a more physiological way than other rotary pumps or roller pumps. Hydraulic and haematological properties have been tested in vitro and in vivo. In a series of seven animal experiments in two different setups, the pump demonstrated its biocompatibility and applicability. Basic aspects of the DeltaStream pump concept as well as important console features are presented. A summary of the final investigation of this pump is given with focus on hydraulic capabilities and results from animal studies.

Animals↗
PubMed2001

The challenge of departmental quality control in the reengineering towards off-pump coronary artery bypass grafting.

OBJECTIVE: Off pump coronary surgery is a major reengineering effort of the surgical systems. There are no perfect tools available to guide every centre in the confrontation with the complete spectrum of risk and the limited number of events. This study analyses the use of a hospital mortality risk-stratifying system in the complete shift towards off-pump CABG. METHODS: All 535 off-pump CABG patients from January 1997 till September 2000 underwent a comparison of their hospital mortality versus the EuroSCORE predictions. The mean risk predicted by the EuroSCORE was 4.5+/-3% (range 0-14) and the mean age was 65+/-10 years (range 36-89). The series includes 23 repeat procedures, also 77 patients with per oral or insulin-treated diabetes. The number of distal anastomoses was 2.5+/-1 and of arterial grafts 1.3+/-0.6. RESULTS: The observed hospital mortality was 15 patients, 2.8% (Fisher exact test P=0.19 versus the EuroSCORE). The 1 and 3 month Kaplan-Meier survival, irrespective from hospital discharge, was 97.4+/-0.7 and 97.2+/-0.7%, respectively. A cumulative risk-adjusted mortality plot is constructed. The area under the ROC curve was 0.886. A stepwise sampling of patients according to increasing risk identified the difference between the EuroSCORE-predicted and observed hospital mortality for the complete spectrum of risk. The P value of this difference was 0.06 for the grouping including all patients from 0-5% risk (78% reduction), 0.04 for the grouping 0-8% risk (61% reduction), and 0.05 for the grouping 0-11% risk (52% reduction of risk). The loss of statistical significant difference was due to the inclusion of the patients at extremely high risk. CONCLUSION: A hospital mortality risk-stratifying system can provide guidance but different and in depth approaches are mandatory to improve the insight, certainly in the presence of a large spectrum of risk.

Aged↗
PubMed2001

Single centre, single domain validation of the EuroSCORE on a consecutive sample of primary and repeat CABG.

OBJECTIVES: Intra- and interdepartmental benchmarking require scoring systems with excellent performance on several properties: discrimination (resolution), reliability (calibration) and stability over the complete spectrum of peri-procedural risk. This single centre, single domain study validates the European system for cardiac operative risk evaluation (EuroSCORE) on an independent sample of primary and repeat coronary artery bypass grafting (CABG) patients and will evaluate these different properties. METHODS: The study population is a consecutive series of 2051 isolated primary and repeat CABG patients, inclusive of patients in cardiogenic shock or resuscitation, operated on in a single institution from January 1997 to July 2000. The age of the patients was 66+/-9 years, 77% were males and 7% were repeat procedures. The EuroSCORE was 5.0+/-3%, with a range from 0 to 22. The studied event was in-hospital death, defined as mortality during hospital stay, which was unlimited in time and included a stay in a secondary hospital without discharge home. RESULTS: The EuroSCORE predicted 102 deaths versus 81 deaths observed (P=0.14, Fisher exact test). The EuroSCORE described only 20% of the variance of in-hospital mortality. The EuroSCORE created an area under the receiver operating characteristic curve of 0.83+/-0.03. The highest discriminative accuracy was obtained with 8% EuroSCORE risk (only 64% sensitivity and 87% specificity). Further exploration identified an over score in the EuroSCORE range 0-8 (57%, P<0.0001). There was an equal score (-2%, P=1) in the range 9-11, but an under score in the range 12-22 (-133%, P=0.003). CONCLUSIONS: On the condition that these single centre results could be extended to any European cardiac surgery centre, it can be concluded that the overall acceptable performance of the EuroSCORE is the result of an over score in the lower risk and insufficient correction in the higher risk spectrum. The EuroSCORE is probably refined enough for improved informed consent versus aggregated results but should only be used for inter-institutional benchmarking with great caution, preferably below the 12% risk pivot.

Aged↗
PubMed2001

Indications for rotary blood pumps in clinical practice.

To understand the needs and requirements in the development of rotary blood pumps, we have to consider the current use and limitations of blood pumps in cardiac surgery. There are 5 different fields of indications for blood pumps in cardiac surgery. First, there is the possibility to use rotary blood pumps in the cardiopulmonary bypass system. Second, miniaturized rotary blood pumps can be used to support beating heart surgery. Third, we expect a growing use of rotary blood pumps in short-term ventricular support. The same applies to the field of chronic cardiac failure and long-term myocardial support. Finally, miniaturized rotary blood pumps can be used to support the ventricle during myocardial infarction. Rotary blood pumps are expected, based on their features, to progress in all these indications.

Angioplasty, Balloon, Coronary↗
PubMed2001

Development of the MEDOS/HIA DeltaStream extracorporeal rotary blood pump.

The DeltaStream blood pump has been developed for extracorporeal circulation with one focus on potential integration into simplified bypass systems (SBS). Its small size and an embedded electric motor are the basic pump properties. A variation of the impeller design has been performed to optimize hydraulic and hematologic characteristics. A simple impeller design was developed which allows flow and pressure generation for cardiopulmonary bypass applications. The option of a pulsatile flow mode for ventricular assist device applications also was demonstrated in vitro. Impeller washout holes were implemented to improve nonthrombogenicity. The pump was investigated for potential thermal hazards for blood caused by the integrated electric motor. It could be demonstrated that there is no thermal risk associated with this design. Durability tests were performed to assess the lifetime of the pump especially with regard to the incorporated polymeric seal. Seal lifetimes of up to 28 days were achieved using different blood substitutes. In animal tests using either the pump as a single device or in an SBS setup, biocompatibility, low hemolysis, and nonthrombogenicity were demonstrated. In summary, the DeltaStream pump shows great potential for different extracorporeal perfusion applications. Besides heart-lung machine and SBS applications, ventricular assist and extracorporeal membrane oxygenation up to several days also appear promising as potential applications.

Animals↗
PubMed2001

Hydrodynamic characterisation of ventricular assist devices.

A new mock circulatory system (MCS) was designed to evaluate and characterise the hydraulic performance of ventricular assist devices (VADs). The MCS consists of a preload section and a multipurpose afterload section, with an adjustable compliance chamber (C) and peripheral resistor (Rp) as principal components. The MCS was connected to a pulse duplicator system for validation, simulating a wide range of afterload conditions. Both pressure and flow were measured, and the values of the different components calculated. The data perfectly fits a 4-element electrical analogon (EA). The MCS was further used to assess the hydrodynamic characteristics of the Medos VAD as an example of a displacement pump. Data was measured for various MCS settings and at different pump rates, yielding device specific pump function graphs for water and pig blood. Our data demonstrate (i) flow sensitivity to preload and afterload and (ii) the effect of test fluid on hemodynamic performance.

Equipment Design↗
PubMed2001

Silzone coating and paravalvular leak: an independent, randomized study.

BACKGROUND AND AIM OF THE STUDY: The study aim was to address independently, in a randomized patient cohort, the impact of Silzone coating on the prevalence and impact of paravalvular leak in patients undergoing mechanical valve replacement. METHODS: Randomized implantation of the uncoated St. Jude Medical Masters, and the Silzone-coated prosthesis was performed in 95 patients, excluding those with suspected or diagnosed infective endocarditis. The company did not support the study; this cohort is not contained in the AVERT trial. Following recall of the Silzone-coated valves, all patients in this cohort were invited to undergo control transthoracic echocardiography and plasma LDH determination. RESULTS: Silzone-coated valves were implanted in 46 patients (57 valves; 34 aortic, 20 mitral, three tricuspid), and uncoated valves in 49 patients (55 valves; 38 aortic, 16 mitral, one tricuspid). One patient with an uncoated mitral valve died from left ventricular dissection. In total, 73 patients returned for specifically planned echocardiography (mean interval 478+/-78 days). Sixteen patients underwent echocardiography on another occasion (mean interval 113+/-202 days). Six hospital survivors did not undergo any postoperative echocardiography. In total, 51 Silzone-coated valves (31 aortic, 18 mitral, two tricuspid), and 53 uncoated valves (37 aortic, 15 mitral, one tricuspid) were evaluated. No patients were reoperated for intrinsic or extrinsic valve dysfunction. No major paravalvular leaks were seen. Five of 51 Silzone-coated valves showed minimal (grade <1+; four aortic, one mitral) paravalvular leak when specifically sought; two showed minimal (grade <1+; one aortic, one mitral), and one slight (grade 1+; one mitral) paravalvular leak in the uncoated group (p = 0.55). The LDH level was 654+/-163 U/I in the Silzone group, and 598+/-124 U/l in the control group (p = 0.10). CONCLUSION: No differences were detected in the incidence of paravalvular leak between Silzone-coated and uncoated mechanical St. Jude Medical valves. The incidence of major paravalvular leaks appears to be lower in the present cohort than was reported in the AVERT trial.

Aged↗
PubMed2000

Micropumps to support the heart during CABG.

OBJECTIVE: To show the effect of myocardial support by micropumps during beating heart CABG for triple vessel disease. METHODS: In 12 sheep, three coronary arteries (LAD, intermediate branch and circumflex) were consecutively occluded for 10 min. The animals were divided in two groups: group 1 without support (n=6) and group 2 with biventricular support of intravascular micropumps. The pumps (diameter 6.4 mm) were placed through peripheral access (femoral artery and jugular vein) and advanced under fluoroscopic guidance. The hemodynamic evolution was analyzed during the procedure and 2 h of reperfusion. Myocardial flow was assessed by colored microspheres. Differences between groups were analyzed by ANOVA for repeated measurements and post-hoc testing in case of significance. RESULTS: All of the pump-supported animals survived the procedure, 1 of the control animals died of resistant ventricular fibrillation. At the end of the reperfusion period, the hemodynamic performance and myocardial contractility was significantly better in the pump-supported group (cardiac output: 2.4+/-0.9 vs. 3.3+/-0.9 l/min, P=0.0192; mean arterial blood pressure: 51+/-23 vs. 73+/-9 mmHg, P=0. 036; first derivative of the left ventricular pressure: 561+/-271 vs. 947+/-316 mmHg/s, P=0.0074). After the procedure, subendocardial blood flow was significantly better in all areas of the left ventricle in group 2 (0.935+/-0.427 ml/min per g vs. 0.409+/-0.183 ml/min per g in group 1; P=0.0366). CONCLUSION: The supported heart is more resistant to repetitive local ischemia. Support by microaxial pumps can make beating heart surgery safer and applicable for more complex cases.

Animals↗