PubMed Health⌕ Search

Biomedical subjects

Philipp Bonhoeffer

Publications and source records attributed to Philipp Bonhoeffer.

At least 19 recordsLinked to original sources
PubMed2006

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

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

Animals↗
PubMed2006

Physiological and clinical consequences of relief of right ventricular outflow tract obstruction late after repair of congenital heart defects.

BACKGROUND: Right ventricular outflow tract obstruction (RVOTO) is a common problem after repair of congenital heart disease. Percutaneous pulmonary valve implantation (PPVI) can treat this condition without consequent pulmonary regurgitation or cardiopulmonary bypass. Our aim was to investigate the clinical and physiological response to relieving RVOTO. METHODS AND RESULTS: We studied 18 patients who underwent PPVI for RVOTO (72% male, median age 20 years) from a total of 93 who had this procedure for various indications. All had a right ventricular outflow tract (RVOT) gradient >50 mm Hg on echocardiography without important pulmonary regurgitation (less than mild or regurgitant fraction <10% on magnetic resonance imaging [MRI]). Cardiopulmonary exercise testing, tissue Doppler echocardiography, and MRI were performed before and within 50 days of PPVI. PPVI reduced RVOT gradient (51.4 to 21.7 mm Hg, P<0.001) and right ventricular systolic pressure (72.8 to 47.3 mm Hg, P<0.001) at catheterization. Symptoms and aerobic (25.7 to 28.9 mL.kg(-1).min(-1), P=0.002) and anaerobic (14.4 to 16.2 mL.kg(-1).min(-1), P=0.002) exercise capacity improved. Myocardial systolic velocity improved acutely (tricuspid 4.8 to 5.3 cm/s, P=0.05; mitral 4.7 to 5.5 cm/s, P=0.01), whereas isovolumic acceleration was unchanged. The tricuspid annular velocity was not maintained on intermediate follow-up. Right ventricular end-diastolic volume (99.9 to 89.7 mL/m2, P<0.001) fell, whereas effective stroke volume (43.7 to 48.3 mL/m2, P=0.06) and ejection fraction (48.0% to 56.8%, P=0.01) increased. Left ventricular end-diastolic volume (72.5 to 77.4 mL/m2, P=0.145), stroke volume (45.3 to 50.6 mL/m2, P=0.02), and ejection fraction (62.6% to 65.8%, P=0.03) increased. CONCLUSIONS: PPVI relieves RVOTO, which leads to an early improvement in biventricular performance. Furthermore, it reduces symptoms and improves exercise tolerance. These findings have important implications for the management of this increasingly common condition.

Adolescent↗
PubMed2006

Percutaneous pulmonary valve implantation.

Percutaneous implantation of valves is a fast evolving field in interventional cardiology. Acquired pulmonary valve disease is uncommon; however, right ventricular outflow tract dysfunction is one of the common indications of reoperations during late follow-up of repaired congenital heart disease. The impact of pulmonary valvular dysfunction on right ventricular function during late follow-up of patients with adult congenital heart disease has led to earlier intervention. The importance of a technique with lower morbidity and mortality, good patient acceptance, and efficacy that is comparable with surgery cannot be underestimated. Percutaneous pulmonary valve implantation uses a valved-stent assembly implanted by means of a double balloon catheter delivery system. The device is a bovine jugular venous valve sutured inside a platinum-iridium. In a series of 58 consecutive patients, we implanted this valve successfully with good clinical and hemodynamic results and no mortality on long-term follow-up. Early device designs led to reintervention by surgical explantation in the early experience, and a second percutaneous pulmonary valve implantation during latter experience. This exciting new technique will lead to review of the current indications and timing of intervention for right ventricular outflow tract dysfunction in late follow-up of congenital heart disease.

Adolescent↗
PubMed2006

Current experience with percutaneous pulmonary valve implantation.

Transcatheter valve replacement has recently been introduced into clinical practice and has the potential to transform the management of valvular heart disease. To date, the largest human experience exists with percutaneous pulmonary valve implantation in patients with repaired congenital heart disease who require re-intervention to the right ventricular outflow tract. The application of this approach, however, is presently restricted to certain right ventricular outflow tract morphologies, because the device needs to be anchored safely to prevent device dislodgement. Early results of percutaneous pulmonary valve implantation show lower morbidity than surgery and significant early symptomatic improvement. In the future, the challenge will be to extend percutaneous pulmonary valve implantation to all patients with a clinical indication to delay or avoid repeat open-heart surgery.

Coronary Angiography↗
PubMed2005

Percutaneous pulmonary valve implantation in humans: results in 59 consecutive patients.

BACKGROUND: Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to reintervention for pulmonary regurgitation and stenosis in later life. METHODS AND RESULTS: Patients with pulmonary regurgitation with or without stenosis after repair of congenital heart disease had percutaneous pulmonary valve implantation (PPVI). Mortality, hemodynamic improvement, freedom from explantation, and subjective and objective changes in exercise tolerance were end points. PPVI was performed successfully in 58 patients, 32 male, with a median age of 16 years and median weight of 56 kg. The majority had a variant of tetralogy of Fallot (n=36), or transposition of the great arteries, ventricular septal defect with pulmonary stenosis (n=8). The right ventricular (RV) pressure (64.4+/-17.2 to 50.4+/-14 mm Hg, P<0.001), RVOT gradient (33+/-24.6 to 19.5+/-15.3, P<0.001), and pulmonary regurgitation (PR) (grade 2 of greater before, none greater than grade 2 after, P<0.001) decreased significantly after PPVI. MRI showed significant reduction in PR fraction (21+/-13% versus 3+/-4%, P<0.001) and in RV end-diastolic volume (EDV) (94+/-28 versus 82+/-24 mL.beat(-1).m(-2), P<0.001) and a significant increase in left ventricular EDV (64+/-12 versus 71+/-13 mL.beat(-1).m(-2), P=0.005) and effective RV stroke volume (37+/-7 versus 42+/-9 mL.beat(-1).m(-2), P=0.006) in 28 patients (age 19+/-8 years). A further 16 subjects, on metabolic exercise testing, showed significant improvement in VO2max (26+/-7 versus 29+/-6 mL.kg(-1).min(-1), P<0.001). There was no mortality. CONCLUSIONS: PPVI is feasible at low risk, with quantifiable improvement in MRI-defined ventricular parameters and pulmonary regurgitation, and results in subjective and objective improvement in exercise capacity.

Adolescent↗
PubMed2005

Steps toward the percutaneous replacement of atrioventricular valves an experimental study.

OBJECTIVES: The goal of this study was to develop a device for percutaneous replacement of the tricuspid valve in animals. BACKGROUND: Percutaneous valve replacement has recently been introduced, and early clinical experience has been reported. To date, this technique is limited to the replacement of pulmonary and aortic valves in selected patients. METHODS: A newly designed nitinol stent, forming two large disks separated by a cylinder with a diameter of 18 mm, was specially designed for the purpose of this study. An 18-mm bovine valve was mounted in the central part of the stent, and a polytetrafluoroethylene membrane was sutured onto the ventricular disk. Eight ewes were equally divided into two groups (group 1, acute study; group 2, killed at one month). RESULTS: Seven of eight devices were successfully delivered in the desired position. In one animal, the device was trapped in tricuspid cordae, leading to its incomplete opening. A significant paravalvular leak was noticed in one animal of group 2. Mean right atrial pressure increased from 5 to 7 mm Hg and did not change during the follow-up. At autopsy, examination confirmed the good position of devices in successfully implanted animals. CONCLUSIONS: Implantation of a semi-lunar valve in the tricuspid position is possible in ewes through a transcatheter approach. A disk-based nitinol stent is needed to allow valve implantation in the atrioventricular position. These studies open new perspectives into tricuspid as well as mitral valve replacement.

Alloys↗
PubMed2005

New insights in minimally invasive valve replacement: description of a cooperative approach for the off-pump replacement of mitral valves.

AIMS: The aim of the present study was to evaluate whether off-pump mini-invasive mitral valve replacement is possible after prior bioprosthetic mitral valve replacement in animals. METHODS AND RESULTS: To validate this concept for off-pump redo mitral valve insertion, we first replaced surgically mitral valves of six sheep under extracorporeal circulation using a Mosaïc valve. Prior to its insertion, we added a radio-opaque ring on its base to enhance its visualization under fluoroscopy. A bovine jugular valve mounted into a stent was then inserted off-pump through an opening of the atrial wall. Mitral valves were replaced successfully in all animals. Following the surgical valve insertion, mean left atrium and left ventricular end-diastolic pressures were 38 (22-42) and 18.8 mmHg (13-22), respectively. Angiography showed perfectly functioning valves, no subaortic valve obstruction, and a mild paravalvular leak in one animal. In one animal, we were unable to control the bleeding from the atrial opening. In this case, trans-atrial valvulation was not attempted. The off-pump valvular implantation was successful in the other five sheep. Haemodynamic data did not change after the insertion of valved stents. Implanted valves were all competent. The animal with the better haemodynamics was kept alive and is still alive 3 months after implantation. CONCLUSION: Surgically implanted bioprosthetic valves provide excellent support for off-pump insertion of a valved stent. Further experiments are necessary, in particular with appropriate valve size, before considering this approach for percutaneous mitral valvular replacement in patients with a dysfunctional bioprosthesis.

Animals↗
PubMed2005

Percutaneous approaches to valvular heart disease.

Percutaneous endovascular therapy has now become a reality. From early balloon valvotomy for valvular stenosis, technologies have been developed that allow percutaneous replacement of pulmonic and aortic valves and repair of regurgitant mitral valves in selected patients. Following extensive investigations in animals, early clinical reports have shown successes in selected patients. As criteria for patient selection and clinical safety and efficacy trials progress, the role of these new technologies in patient care strategy will become better understood.

Adolescent↗
PubMed2005

The potential impact of percutaneous pulmonary valve stent implantation on right ventricular outflow tract re-intervention.

OBJECTIVE: To assess the impact of a percutaneous technique for pulmonary valve implantation on the conventional surgical valve/conduit approach to right ventricular outflow tract re-intervention. METHODS: We have retrospectively reviewed our results following surgical or percutaneous re-intervention to the right ventricular outflow tract in both paediatric and adult groups. Between November 1998 and March 2004, 94 patients underwent surgical re-intervention to the right ventricular outflow tract. Percutaneous pulmonary valve implantation was introduced in October 2002 and 35 procedures were performed to March 2004. The median age was 26 years (6-65 years) in the surgical group and 16 years (9-39 years) in the percutaneous group. Tetralogy of Fallot was the commonest original diagnosis (64.9 and 62.9%, respectively). The predominant indication for re-intervention in the surgical group was pulmonary regurgitation (64.9%) compared to the percutaneous group in which it was homograft/conduit stenosis or a mixed lesion (68.6%). RESULTS: There has been one (1.1%) early death reported in the surgical series and none in the percutaneous group. In the surgical group 9 (9.6%) experienced a procedural complication whilst 3 (8.5%) of those undergoing a percutaneous valve experienced a significant procedural event necessitating urgent surgery. Important early morbidity was 8 (8.5%) in the surgical group and 2 (5.7%) in the percutaneous group. Freedom from re-operation at 1 year was 100% in the surgical group and 86.1% in the percutaneous group due to late restenosis. Median hospital stay in the surgical group was 7 (4-114) days and 2 (2-22) days in the percutaneous group. CONCLUSIONS: Preliminary data suggests that percutaneous pulmonary valve implantation provides a promising additional and complementary approach to a successful surgical programme. Both approaches are safe with acceptable levels of morbidity and low mortality. With current technology the aneurysmal outflow tract remains a problem for the percutaneous approach. Follow-up remains too short, at present, to prove longevity of the percutaneous conduit.

Adolescent↗
PubMed2005

Off-pump replacement of the pulmonary valve in large right ventricular outflow tracts: a hybrid approach.

BACKGROUND: Percutaneous pulmonary valve replacement has recently been introduced and is under investigation in humans. This technique is, however, limited to patients with a right ventricular outflow tract that does not exceed 22 mm in diameter. We report our experience of off-pump pulmonary valve replacement using a hybrid approach in animals with large right ventricular outflow tracts. METHODS: Eight ewes were included in the protocol and were equally divided into 2 groups. A left thoracotomy was first performed, and the main pulmonary artery was banded by using 2 radiopaque rings with a diameter of 18 mm that allowed for further pulmonary valve replacement. We then intended to implant a valved stent either percutaneously (group 1) or through a transventricular approach (group 2). All animals were killed after valve implantation. The operation allowed the pulmonary diameter to be reduced from 30 to 17.6 mm. RESULTS: The right ventricular pressure did not significantly increase after reduction of the pulmonary artery diameter (25 vs 36 mm Hg). Subsequent pulmonary valve replacement through a percutaneous or a transventricular approach was always possible without any requirement for extracorporeal circulation. All devices were successfully delivered inside the pulmonary artery banding and were functioning perfectly at early evaluation. CONCLUSIONS: Implantation of a pulmonary valve is possible in ewes through a hybrid approach when the right ventricular outflow tract exceeds 22 mm in diameter. This involves both surgeons and interventionists and allows for a staged procedure in which the valvulation is performed percutaneously or, for a combined hybrid approach, in which the valve is implanted off pump transventricularly during the same operation.

Animals↗
PubMed2005

Complications of paediatric interventional catheterisation: an analysis of risk factors.

OBJECTIVES: To identify predictive factors of complications occurring during paediatric interventional catheterisation. BACKGROUND: Interventional paediatric catheterisation is still burdened by a substantial risk. Risk factors, however, have rarely been investigated. METHODS: We analysed prospectively 1,022 interventional procedures performed over a period of 8 years, excluding 260 procedures for atrial septostomy. We considered several patient-related variables, specifically age, weight, and gender, type of procedure, times required for fluoroscopy and the overall procedure, technical challenge, and the severity of the clinical condition. We also analysed variables linked to the environment, specifically the date of the examination, whether the operator remained in training, the novelty of the material, any breakdown in the installation, and errors made by the operator. We classified complications as those without clinical consequence, those which proved lethal, those requiring cardiopulmonary resuscitation, elective or emergency surgery, hospitalisation in the intensive care unit, and those leading to recatheterisation. RESULTS: Our average incidence of complications was 4.1 per cent, which did not change significantly during the period of study. Of the patients, 4 died, 7 needed urgent surgery, 5 elective surgery, 3 hospitalisation in intensive care unit, and 8 recatheterisation. Independent risk factors for complications were technical challenge, critical clinical condition, operator in training, operator error, and breakdown of the installation. Young age was not associated with a higher risk of complications. Patients in whom no cause for complication could be found, either related to their own features or the environment, had a risk of complication of 1.4 per cent (95 per cent confidence intervals from 0.7 to 2.5 per cent). CONCLUSIONS: Our data show that variables relating either to the patient or the environment of catheterisation are associated with an increased risk of procedural complications. Knowledge of the risk factors can improve the odds of paediatric interventional catheterisation.

Adolescent↗
PubMed2004

Percutaneous pulmonary valve replacement in a large right ventricular outflow tract: an experimental study.

OBJECTIVES: We report our initial experience with percutaneous pulmonary valve replacement in animals with large pulmonary trunks, using a modified percutaneous approach. BACKGROUND: Percutaneous pulmonary valve replacement has recently been introduced, and early clinical experience has been reported. This technique is presently limited to patients with a right ventricular outflow tract no bigger than 22 mm in diameter. METHODS: In seven animals (groups 1 and 3), we implanted a newly designed nitinol stent in the shape of a conduit with a central restriction of its diameter, containing an 18-mm bovine valve, as a one-step procedure. The animals in groups 1 and 3 were sacrificed after valve implantation and after two-month follow-up, respectively. In the second group (n = 3), we expected to percutaneously reduce the diameter of the pulmonary artery. Eight weeks later, we implanted an 18-mm valve mounted in a balloon-expandable stent. These animals were sacrificed after valve implantation. RESULTS: Eight of 10 devices were successfully delivered and were functioning perfectly at the initial evaluation and after two months. We failed to cross the tricuspid valve in two cases. The downsize mechanism allowed the pulmonary diameter to be reduced from 30 to 18 mm, without an impact on right ventricular function in any of the animals. CONCLUSIONS: Non-surgical implantation of a pulmonary valve is possible in ewes with all types of pulmonary trunk, regardless of its size. A "downsize" stent is needed to allow valve implantation in a large trunk. Further refinements will make this technique feasible in humans.

Animals↗