PubMed Health⌕ Search

Biomedical subjects

Harald Bertram

Publications and source records attributed to Harald Bertram.

9 recordsLinked to original sources
PubMed2006

Interventional atrial septal defect closure using a totally bioresorbable occluder matrix: development and preclinical evaluation of the BioSTAR device.

OBJECTIVES: We sought to test the hypothesis that interventional atrial septal defect (ASD) closure can be performed safely and effectively using a bioresorbable occluder matrix. BACKGROUND: The ideal septal occluder scaffold should promote the healthiest and most complete healing response while eventually facilitating the full resorption of the material and leaving "native" tissue behind, thus minimizing the potential for future complications from chronic foreign body and maintaining the possibility for later unobstructed transseptal access to the left atrium. METHODS: The STARFlex occluders (NMT Medical Inc., Boston, Massachusetts) were modified by substituting the conventional polyester fabric for a bioengineered, acellular type-I collagen matrix derived from porcine submucosa with a heparin-coated surface (BioSTAR occluder, NMT Medical Inc.). Comparative transcatheter closure of ASDs was performed in young sheep (n = 36). Gross pathology and histopathology were obtained after follow-up periods ranging from 7 days to 2 years. RESULTS: The STARFlex (control) devices were encapsulated time-dependently by ingrown fibrous tissue. Histology showed a mild but chronically persisting foreign body reaction. By contrast, BioSTAR devices exhibited a mild-to-moderate transient cellular immune response. Heparin coating of the BioSTAR surface improved the biocompatibility of the device by reducing surface thrombogencity. A remodeling process of the collagen scaffold, starting after 30 days in vivo, resulted in the full replacement of the matrix by host tissue after 2 years of follow-up. CONCLUSIONS: The BioSTAR device is the first septal occluder with a totally bioresorbable matrix that is fully replaced by host tissue during the healing process. The promising results of this study support testing of the BioSTAR device in clinical trials.

Absorbable Implants↗
PubMed2005

Prophylaxis of thromboembolic complications after the Fontan operation (total cavopulmonary anastomosis).

OBJECTIVES: Thrombotic events have been reported as a major cause of morbidity after the Fontan procedure. There is no consensus concerning the postoperative mode and duration of anticoagulation prophylaxis. In a retrospective study, we evaluated the results of a prophylactic regimen on the basis of the surgical technique, potentially predisposing risk factors, and specific sequelae. METHODS: We evaluated 142 surviving patients after total cavopulmonary anastomosis (mean follow-up was 91.1 +/- 43.9 months). Prophylactic antithrombotic treatment was initiated in 86 patients with partial prosthetic venous pathway with acetylsalicylic acid; 45 patients with complete autologous tissue venous pathway or partial prosthetic venous pathway received no anticoagulation, and 11 patients received warfarin sodium (Coumadin). During long-term follow-up, 22 patients (12 after acetylsalicylic acid medication) crossed over to warfarin. RESULTS: Thrombotic events occurred in 10 patients (7%), with systemic venous thrombus formation in 8 (5.6%), stroke in 2 (1.4%), and a peak incidence during the first postoperative year. Eight of 10 patients were receiving heparin therapy mainly for prolonged postoperative immobilization. During follow-up, none of the 74 patients receiving acetylsalicylic acid and 1 of 40 patients without medication presented with thrombus formation. Under warfarin medication, 1 of 28 patients had an asymptomatic thrombus. Expected freedom from a thromboembolic event was 92% at 5 years and 79% at 10 years. There was no association with coagulation factor abnormalities. Protein-losing enteropathy was present in 4 of 10 patients. CONCLUSION: A prophylactic anticoagulation strategy that considers the surgical technique and potential predisposing circumstances proved effective in the prevention of late thrombotic complications after total cavopulmonary anastomosis. There is no need for routine anticoagulation during long-term follow-up after Fontan-type surgery in pediatric patients.

Anticoagulants↗
PubMed2003

A new biological matrix for septal occlusion.

The ideal septal occluder scaffold should promote the healthiest and most complete healing response possible while eventually facilitating the full resorption of the material, leaving "native" tissue behind. An excellent biocompatibility of the scaffold tissue is a prerequisite for quick, complete, and firm ingrowth of the device, optimizing outcomes and minimizing the potential for complications. Intestinal collagen layer (ICL) is a highly purified (acellular) bioengineered type-1 collagen derived from porcine submucosa. It is gradually resorbed by the host organism and subsequently replaced by the host tissue. CardioSEAL occluders were modified by substituting the conventional polyester fabric for an intestinal collagen layer (ICL). Percutaneous transcatheter closure of interventionally created atrial septal defects was performed in lambs using these modified occluders. A complete pathomorphological investigation including histology was carried out after 2, 4, and 12 weeks follow-up. Standard CardioSEAL implants served as a control group. After 2 weeks in vivo the devices were already covered completely by neo-endothelium. Compared with the conventional synthetic scaffold, ICL devices showed a quicker endothelialization, decreased thrombogenicity, and superior biocompatibility with no significant cellular infiltration observed in the histology of explants with ICL fabrics. After 3 months in vivo the collagen layer remained mechanically intact, but began to show the first histological signs of mild disintegration, gradual resorption, and remodeling. In conclusion, short-term results from preliminary in vivo experiments using a bioengineered collagen matrix as the occluder tissue scaffold showed excellent biocompatibility. This resulted in superior overall results: quicker endothelialization, a decreased thrombogenicity, and decreased immunological host response.

Absorbable Implants↗
PubMed2002

Intraatrial reentrant tachycardias in patients after atrial switch procedures for d-transposition of the great arteries Endocardial mapping and radiofrequency catheter ablation primarily targeting protected areas of atrial tissue within the systemic venous atrium.

Thirteen patients with d-transposition of the great arteries after the Mustard/Senning procedure underwent electrophysiological study for recurrent intraatrial reentrant tachycardia (IARTs). In 8 patients, a 20-pole electrode catheter and a steerable 7F mapping and ablation catheter were placed in the systemic venous atrium, and via the retrograde route in the pulmonary venous atrium, if required. During IART pace mapping and entrainment mapping were performed in order to localize protected areas of atrial tissue between anatomical and/or surgical barriers of electrical isolation. The systemic venous atrium of 5 patients was studied using the non-contact mapping system (Ensite 3000(TM)). Linear radiofrequency current lesions were induced after mapping of electrical protected areas from the medial aspect of the superior caval vein to the systemic venous atrium and/or intraatrial baffle or the intraatrial suture line in 4 patients, from the medial aspect of mitral valve annulus to the inferior caval vein in 5 patients, from the intraatrial suture line to the posterior systemic venous atrium in 1 patient and in 2 patients from the posterior and inferior pulmonary venous atrium to the tricuspid valve annulus. Subsequently, 14 of the 15 identified IARTs were not inducible during repeated programmed stimulation. Mean duration of the electrophysiological study was 202 min, mean fluoroscopy time was 21.6 min. During follow-up (mean 20 months), 10 of 12 patients with successful procedures are free of tachycardia, 2 patients developed IARTs with a new morphology. In the majority of our patients, curative treatment was feasible by induction of linear radiofrequency current lesions by primarily targeting electrical protected areas of atrial tissue in the systemic venous atrium.

Adolescent↗
PubMed2002

Fontan-type procedures: residual lesions and late interventions.

BACKGROUND: The purpose of this study was to determine the type and incidence of hemodynamic and electrophysiological abnormalities requiring surgical or catheter-based interventions in a single-center long-term experience. METHODS: Eighty-eight patients with a follow-up of at least 5 years (mean follow-up, 9.6 +/- 2.6 years) after Fontan-type procedures were included. All patients had undergone cardiac catheterization either as part of the regular postoperative protocol or because of symptomatic atrial tachycardia or increasing cyanosis. RESULTS: Freedom from reoperation for up to 5 years was documented for 82% of patients and decreased to 76% after 8 years. Late reoperations included conversion of an atriopulmonary anastomosis to a total cavopulmonary anastomosis in 2 patients with atrial dysrhythmia and implantation of an extracardiac conduit in 1 patient with left atrial isomerism and intrapulmonary arteriovenous malformations after a Kawashima operation. Decline in sinus node function with symptomatic bradycardia required pacemaker therapy in 10 patients (11%). Transcatheter interventions included fenestration occlusion in 5 of the 11 patients with initial baffle fenestration. In 6 of 17 patients with aortopulmonary collaterals, coil occlusion was indicated to reduce future systemic ventricular volume load. Various systemic venous collaterals were documented in 11 patients and required coil occlusion in 2. One patient with symptomatic protein-losing enteropathy underwent transcatheter fenestration creation without sustained relief of symptoms. Freedom from transcatheter interventions decreased from 94% to 82% after 5 and 10 years, respectively. CONCLUSIONS: During long-term follow-up, reoperations are rare and mainly involve Fontan conversion to either a lateral-tunnel or extracardiac-conduit procedure. Detailed angiographic evaluation on a routine basis allows identification of the vascular sites of origin of aortopulmonary collateral vessels and systemic venous collaterals potentially developing during long-term follow-up. Transcatheter interventions including fenestration occlusion and occlusion of venous collaterals and aortopulmonary collaterals were performed to maintain and improve the Fontan circulation in clinically symptomatic and asymptomatic patients. During long-term follow-up after Fontan-type operations, a regular postoperative cardiac catheterization protocol is recommended.

Adolescent↗
PubMed2002

Experimental ASD closure using autologous cell-seeded interventional closure devices.

OBJECTIVE: Atrial septal defect (ASD) occluders are permanent implants in paediatric cardiology which serve as mechanical shields until complete overgrowth and incorporation of the occluding device by autologous tissue has occurred. Thereafter, the foreign body material making up the device is dispensable and bears potential long-term adverse effects. Rapid, firm and complete incorporation into the atrial septal wall should be a prerequisite for biodegradable devices. In this study, the feasibility of using autologous cell-seeded devices was investigated by (a) testing the influence of a collagen coating on cellular stress resistance in vitro and (b) comparing the short-term effects between cell-seeded, collagen-coated and acellular ASD occluders in vivo. METHODS: Native and collagen-coated Dacon fabrics and Starflex-devices were pre-seeded with autologous fibroblasts (skin biopsy) and evaluated using various mechanical stress tests. In a sheep model interventionally created ASDs were closed using either autologous pre-seeded or conventional (acellular) Starflex-devices. RESULTS: ASD closure devices were successfully pre-seeded with autologous cells. The incubation period needed, the cellular density achieved and the mechanical stability of the cytolayer after mechanical stressing (implantation) were improved by applying a collagen matrix on the fabric. Compared to the thin layer of ingrown tissue seen on conventional occluders after 30 days in vivo, a thicker layer of organising, newly formed granulation tissue on pre-seeded collagen-coated devices embedded not only the Dacron fabric, but also completely covered the spring arms of the device underneath a layer of neo-endothelium. CONCLUSION: Autologous cell pre-seeding of interventional closure devices is feasible since the cells survive the mechanical stress encountered during implantation. Rapid, firm and complete ingrowth of occluder devices into a thicker layer of young fibrous granulation tissue can be achieved, but an increased thrombogenicity currently limits the in vivo application.

Absorbable Implants↗