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Biomedical subjects

M Sigler

Publications and source records attributed to M Sigler.

At least 19 recordsLinked to original sources
PubMed2005

Breakable stent for interventions in infants and neonates: an animal study and histopathological findings.

OBJECTIVE: To test in a neonatal animal model the feasibility and biocompatibility of a new breakable stent that can be broken open by balloon dilatation during reintervention for use in neonates and infants. MATERIALS AND METHODS: Medical grade stainless steel breakable stents (n = 16) were interventionally implanted in systemic arteries in neonatal piglets (n = 7). Patency of the stented segments was shown by repeated angiography. Stents were redilated up to three times. After a follow up of 18-165 days the animals were killed and the tissue block containing the stent was excised. Besides standard histological examination, scanning electron microscopy was used for biocompatibility screening. RESULTS: The stents were broken by redilatation with a conventional angioplasty balloon catheter. During follow up, patency of all stented segments was shown angiographically. One stent became dislocated during implantation. One vessel ruptured during redilatation when an inadequately large balloon catheter was used for dilatation. No other complications were observed. Scanning electron microscopy showed complete cellular coverage of the stent struts. Histological examination showed thinning of the vessel wall and partial rupture of the media at the site of stent breakage. An only mild inflammatory reaction was detected. CONCLUSION: The new breakable stent can be broken open by simple angioplasty. Feasibility, effectiveness, and biocompatibility were shown in an animal model. Surgery to remove stents from paediatric patients due to disproportion between a previously implanted stent and the growing vessel may be avoided by the use of a breakable stent.

Animals↗
PubMed2005

Biocompatibility screening in cardiovascular implants.

BACKGROUND: Interest in information on biocompatibility of implants is increasing. The purpose of this paper is to discuss methods and results of pathological biocompatibility screening of explanted cardiovascular implants. METHODS: Use of standard histology after embedding in paraffin is limited since metallic implants have to be removed during workup with disruption of the specimen. Alternatively, tissue blocks containing an implant can be embedded in methylmethacrylate or hydroxyethylmethacrylate and processed by sectioning with a diamond cutter and grinding, thus leaving the implant in situ and saving the tissue/implant interface for detection of local inflammatory reactions. Another important aspect of evaluation is the progress of thrombus organisation after initial fibrin clotting on the metal surface or in the inner part of occlusion devices. New methacrylate resins and embedding techniques allow for specific immunohistochemical staining of the specimen thus enabling characterisation of tissues surrounding the implant. Information on endothelialisation of the vascular surface of the implant can be obtained by means of immunohistochemistry or by scanning electron microscopy. RESULTS: Illustrating the use of these technologies, we demonstrate findings in tissue specimens from animal studies with different types of devices (i.e. stents, occlusion devices). We present corresponding findings in human specimens with implants that were removed during corrective surgery for congenital heart defects. Early endothelialisation of the vascular surface was seen after implantation in all types of devices. Cells within occlusion devices could be characterised histologically and immunohistochemically as fibromuscular cells as seen in intimal hyperplasia after stent implantation. Inflammatory implant-host reactions ranged from mild to moderate (medical grade stainless steel, nitinol) to severe (polytetrafluoroethylene [PTFE]). CONCLUSIONS: With an optimal work-up of cardiovascular implants, ingrowth and endothelialisation as well as inflammatory reactions in the surrounding tissue can be assessed. This information allows evaluation of individual tissue reactions to the implant and may serve as valuable basis for optimisation of biocompatibility by implant modification.

Animals↗
PubMed2001

Time course of cranial ultrasound abnormalities after arterial switch operation in neonates.

BACKGROUND: The object of this study was to investigate the time course and fate of abnormal findings in cranial ultrasound after performing an arterial switch operation in neonates with transposition of the great arteries, and to analyze the relationship to cerebral cell damage. METHODS: Cranial ultrasound was performed prospectively in 35 neonates with transposition of the great arteries before the operation as well as 4 hours, 1, 2, and 3 days, and 1 and 2 weeks postoperatively. Blood levels of neuron-specific enolase, a marker of cerebral cell damage, were determined before, during, and 4 and 24 hours postoperatively. RESULTS: In 17 of 35 neonates (49%), early postoperative cranial ultrasound revealed abnormalities indistinguishable from intraventricular hemorrhage. In 11 neonates findings were transient and were normalized 2 weeks postoperatively, whereas in the remaining 6 neonates there was evidence of resolving hemorrhage. In all neonates there was a rise in neuron-specific enolase blood concentrations during and 4 hours after extracorporal circulation without correlation to sonographic findings. CONCLUSIONS: Enhanced echogenicity of the choroid plexus or dilatation of the cerebral ventricular system is a frequent early postoperative finding that may be caused by transient plexus edema rather than intraventricular hemorrhage and is not related to cerebral cell damage.

Arteries↗
PubMed2001

Neurodevelopmental outcome related to cerebral risk factors in children after neonatal arterial switch operation.

BACKGROUND: Neurodevelopmental outcome after neonatal arterial switch operation for complete transposition of the great arteries is an important topic needing prospective assessment. METHODS: A group of 33 unselected children (3.0 to 4.6 years) operated on as neonates with combined deep hypothermic circulatory arrest and low flow cardiopulmonary bypass and a control group of 32 age-matched healthy children (3.0 to 4.8 years) underwent evaluation of socioeconomic and clinical neurological status and a standardized test comprising all areas of child development. Results of patients were related to those of the control group, to population norms, and to preoperative, perioperative, and postoperative cerebral risk factors. RESULTS: Clinical neurological status was normal in 26 patients (78.8%) and reduced in 7 (21.2%). Complete developmental score and the subscores for motor function, visual perception, learning and memory, cognitive function, language, and socioemotional functions were not different compared to population norms. Compared to the patients, the children of the control group scored higher on tests of complete development, cognition, and language, but also on socioeconomic status. Complete developmental score and the scores for motor, cognitive, and language functions were weakly inversely related to the duration of circulatory arrest, but not to the duration of bypass. Cerebral risk factors such as serum levels of the neuron-specific enolase, perinatal acidosis, perinatal asphyxia, peri- and postoperative cardiocirculatory insufficiency, or clinical seizures were not correlated to the test results. CONCLUSIONS: Neonatal arterial switch operation with combined circulatory arrest and low flow bypass is associated with neurological impairment, but not with reduced development as assessed by formal testing of motor, cognitive, language, and behavioral functions. Perioperative serum level of the neuron-specific enolase is not a valid marker for later developmental impairment.

Arteries↗
PubMed2001

Effective and safe but forgotten: methsuximide in intractable epilepsies in childhood.

The efficacy and safety of methsuximide (MSM) was evaluated in children with intractable epilepsies in a prospective uncontrolled study. MSM was added to the therapeutic regimen of 112 children with intractable epilepsy under inpatient conditions, all of whom were therapeutically refractory to various first-line antiepileptic drugs (AED) or combinations of other AED. Titration of MSM was performed following a uniform protocol. Administration of MSM resulted in a 50% or greater reduction in seizure frequency in 40 patients after a short-term observation period (mean 9.1 weeks). After a mean of 3.7 years, the rate of seizures and side effects were re-evaluated in 39 patients who were still receiving MSM as part of their antiepileptic regimen. Twenty two of these patients derived long-term benefit from MSM. In patients with good seizure control, fasting plasma levels of N-desmethylmethsuximide, the principal active metabolite of MSM, were 25.3-44.7 mg l(-1)(mean 36.0 mg l(-1)). Thus effective plasma levels of N-desmethylmethsuximide in children were found to be higher than previously described. Forty one of 112 patients (28.9%) developed side effects during MSM treatment. No serious or irreversible side effects were seen. Our study demonstrates the value of MSM as an 'add-on' drug in intractable epilepsies.

Anticonvulsants↗
PubMed2001

Influence of temperature during cardiopulmonary bypass on leukocyte activation, cytokine balance, and post-operative organ damage.

This study examined the hypothesis that core temperature (T(o)) during cardiopulmonary bypass (CPB) influences the perioperative systemic inflammatory response and post-operative organ damage. Twenty-four pigs were assigned to a T(o) regimen during CPB: normothermia (T(o) 37 degrees C; n = 8), moderate hypothermia (T(o) 28 degrees C; n = 8), or deep hypothermia (T(o) 20 degrees C; n = 8). Perioperative leukocyte activation, endotoxin release, and production of tumor necrosis factor-alpha (TNFalpha) and interleukin-10 (IL10) were examined with regard to post-operative organ damage, which was scored at histological examination of tissue probes of heart, lungs, liver, kidney, and ileum, taken 6 h after CPB. Total blood leukocyte count and TNFalpha plasma levels during CPB were significantly lower and IL10 levels were significantly higher in the moderate hypothermic group than in both other groups. Elastase activity, leukotriene B4-, and endotoxin levels were not affected by T(o) regimen. Moderate hypothermia was associated with the lowest histological organ damage score and normothermia with the highest. In all animals organ damage score for heart, lungs, and kidneys correlated significantly with TNFalpha levels at the end of CPB. Our data demonstrate a clear relationship between TNFalpha production during cardiac operations and post-operative multiple-organ damage. Moderate hypothermia, by stimulating IL10 synthesis and suppressing TNFalpha production during CPB, might provide organ protection.

Animals↗
PubMed2001

Heart rate variability in elderly patients before and after electroconvulsive therapy.

Earlier studies have found major depression to be associated with increased cardiac mortality, hypothesized to result from reduced vagal modulation. Since reduced heart rate variability is part of normal aging, depression might predispose elderly patients to a higher risk. The authors investigated cardiac autonomic modulation, using spectral analysis, in 11 elderly depressed inpatients before and after electroconvulsive therapy (ECT). Cardiac vagal modulation increased significantly after ECT and was associated with symptom improvement, assessed by a significant decrease in the Hamilton Rating Scale for Depression. Further research is needed to elucidate the relationship between depression, autonomic modulation, and clinical risks in elderly patients.

Aged↗
PubMed2000

QT dispersion in the surface electrocardiogram in elderly patients with major depression.

BACKGROUND: QT dispersion (QTd) is a measure of interlead variations of QT interval of the surface 12-lead electrocardiogram (ECG). Increased QTd, found in various cardiac diseases, reflects cardiac instability and is associated with increased cardiac death. Major depressive disorder (MDD) was found to be associated with high cardiovascular mortality rates. This study compares QTd in elderly patients with MDD to normal controls. METHODS: QTd and rate-corrected QTd of 18 physically healthy elderly patients (69.9 +/- 7.6 years) with MDD was compared to nine physically and mentally healthy age- and gender-matched controls (64.1 +/- 12.2 years). RESULTS: QTd and rate-corrected QTd were significantly higher in MDD compared to controls (68 +/- 30 vs. 40 +/- 13 ms, P=0.002 and 81 +/- 39 vs. 43 +/- 13 ms, P=0.001, respectively). Intra- and inter- observer reproducibilities were highly correlated (r=0.96, P <0.0001; r=0.88, P <0.001, respectively). LIMITATIONS AND CONCLUSIONS: The major limitations of this study are the small number of subjects and the fact that all the patients were maintained on antidepressant medication. However, it seems that QTd analysis might shed light on possible autonomic imbalance and also provide a novel cardiovascular risk factor for increased cardiac death in MDD.

Aged↗
PubMed2000

Evaluation of in vivo biocompatibility of different devices for interventional closure of the patent ductus arteriosus in an animal model.

OBJECTIVE: To evaluate the in vivo biocompatibility of three different devices following interventional closure of a patent ductus arteriosus (PDA) in an animal model. MATERIALS AND METHODS: A medical grade stainless steel coil (n = 8), a nickel/titanium coil (n = 10), and a polyvinylalcohol foam plug knitted on a titanium wire frame (n = 11) were used for interventional closure of PDA in a neonatal lamb model. The PDA had been maintained by repetitive angioplasty. Between one and 278 days after implantation the animals were killed and the ductal block removed. In addition to standard histology and scanning electron microscopy, immunohistochemical staining for biocompatibility screening was also undertaken. RESULTS: Electron microscopy revealed the growth of a cellular layer in a cobblestone pattern on the implant surfaces with blood contact, which was completed as early as five weeks after implantation of all devices. Immunohistochemical staining of these superficial cells showed an endothelial cell phenotype. After initial thrombus formation causing occlusion of the PDA after implantation there was ingrowth of fibromuscular cells resembling smooth muscle cells. Transformation of thrombotic material was completed within six weeks in the polyvinylalcohol plug and around the nickel/titanium coil, and within six months after implantation of the stainless steel coil. An implant related foreign body reaction was seen in only one of the stainless steel coil specimens and in two of the nickel/titanium coil specimens. CONCLUSION: After implantation, organisation of thrombotic material with ingrowth of fibromuscular cells was demonstrated in a material dependent time pattern. The time it took for endothelium to cover the implants was independent of the type of implant. Little or no inflammatory reaction of the surrounding tissue was seen nine months after implantation.

Animals↗
PubMed1998

Double-helix coil for occlusion of large patent ductus arteriosus: evaluation in a chronic lamb model.

OBJECTIVES: We sought to evaluate the efficacy and tissue reaction of a new miniature interventional device for occlusion of large patent ductus arteriosus (PDA) in a neonatal lamb model. BACKGROUND: A variety of devices are used to close PDAs by interventional measures. Spring coils found to have a high cumulative occlusion rate have thus far been limited to smaller PDAs because of the physical limitation of grip forces. METHODS: Memory-shaped double-cone stainless steel coils with enhanced stiffness of the outer rings by a double-helix configuration were mounted on a titanium/nickel core wire. A snap-in mechanism attaches the coil to the delivery wire, allowing intravascular coil retrieval and repositioning. The system was placed through a 4F or 5F Teflon catheter. A chronic lamb model (n = 8) of PDA (>5 mm) was used in which ductus patency was secured by a protocol of repetitive angioplasty procedures. The animals were killed after 1 to 181 days, and the ductal region was examined by inspection as well as by light and electron microscopy. RESULTS: Placement of the coils within the PDA was possible in all lambs. Before final detachment, the coils were retrieved or repositioned, or both, up to 12 times. In all but one animal the ductus was closed within 6 days after the procedure. The coils caused no infections or aortic and pulmonary artery obstruction. Histologic and electron microscopic studies revealed endothelial coverage of the implants but no foreign body reaction or local or systemic inflammation or erosion of the implant. CONCLUSIONS: The device effectively closed large PDAs in our model and may overcome the previous limitations of coils. Clinical trials are indicated.

Angiography↗
PubMed1998

Characteristics of patients with schizophrenia successive to childhood attention deficit hyperactivity disorder (ADHD).

The goal of this study was to investigate the characteristics of schizophrenic patients with a history of childhood attention deficit hyperactivity disorder (ADHD). The study was performed on 37 adolescent patients meeting the DSM-III-R criteria for schizophrenia and ADHD and 40 controls with schizophrenia only. Schizophrenic patients who were diagnosed in childhood as suffering from ADHD had more prominent developmental disturbances in infancy, more insidious course of schizophrenia, failed to respond to neuroleptics and had poorer outcome as compared to patients with schizophrenia only. The results of this study indicate that schizophrenia subsequent to childhood ADHD has a poor prognosis as compared to schizophrenia only.

Adolescent↗
PubMed1997

Retrievable patent ductus arteriosus plug for interventional, transvenous occlusion of the patent ductus arteriosus. Evaluation in lambs and preliminary clinical results.

RATIONALE AND OBJECTIVES: The clinically most widely used devices (Porstmann-plug, Rashkind-umbrella, Botallooccluder) have inherent specific limitations (eg, transarterial approach, residual shunts, limited retrieval). The authors assess practicability, efficacy, and tissue reaction of the new retrievable transvenous plug device for the occlusion of the persistent patent ductus arteriosus (PDA). METHODS: A foam plug (polyvinyl alcohol) is mounted on a titanium core pin where, at both ends, small legs (titanium nickel alloy) with titanium heads are anchored, to ensure safe fixation in the ductus. The device is introduced transvenously through a long sheath (Mullins sheath) and held by a modified biopsy forceps allowing complete retrieval until final release. A common lamb model of large PDAs (n = 11) was used to test for practicability and the histomorphologic outcome. Clinical results were obtained from a consecutive series of 16 patients (aged 13 to 71 years). RESULTS: In all lambs, placement of the plug within the PDA was possible. Histopathology (follow-up 10 to 215 days; mean 112 days) revealed an adequate ingrowing of the device and no pathologic foreign body reaction. The diameter of the human PDAs ranged from 3 to 7 mm (mean 5 mm). The size of the sheath used for introducing the plug (diameter 8 to 16 mm) ranged from 8 to 16 French. Fourteen of 16 PDAs were closed immediately after or on day 1 after implantation, 1 was closed after the 12-month follow-up, and 1 needed an additional plug after 30 months for definitive closure. CONCLUSIONS: The device demonstrated practicability and biocompatibility in our experimental lamb model and effectively closed the PDA in a consecutive series of 16 patients. A greater number of patients and a longer follow-up period are necessary for the definitive clinical assessment of the new device.

Adolescent↗
PubMed1997

Coil on the loop and selectively enhanced stiffness for improved control: feasibility study in the neonatal ovine model of the large patent ductus arteriosus.

RATIONALE AND OBJECTIVES: Several devices have been suggested and tested for interventional closure of the persistent ductus arteriosus. Coils were found effective only in small ducts due to their lack of maneuverability and physical limitation of grip forces leading to risk of embolization. The authors evaluated the feasibility to place single coils with selectively enhanced stiffness into high shunting ductus arteriosus, the coils being deployed and controlled through a veno-arterial loop in a bovine model. METHODS: "Double-cone" shaped, stainless steel coils with enhanced stiffness of the outer rings were mounted on either end on a nitinol core wire. A snap-in mechanism attaches the coil to this delivery wire and is freed by a pusher system of coiled steel wire that is advanced over the core wire. Forming a veno-arterial loop across the patent ductus allows for repositioning into the pulmonary artery or aortic catheter. A chronic lamb model of large patent ductus arteriosus (PDAs) (> or = 9 mm) was used in which ductus patency was secured by a protocol of repetitive angioplasties. Different systems (n = 10) were placed having retrieved the previous coil by a snare after definitive release. RESULTS: Placement of coils was possible in all 10 attempts. The coils were pulled back into the catheters between five and eight times before definitive release. CONCLUSIONS: The device allows controlled placement of single coils in our model of large PDAs and may lead the way to overcome previous limitations of coils. Clinical trials are warranted.

Animals↗