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Biomedical subjects

W Radtke

Publications and source records attributed to W Radtke.

At least 19 recordsLinked to original sources
PubMed2000

Transcatheter closure of multiple atrial septal defects. Initial results and value of two- and three-dimensional transoesophageal echocardiography.

AIMS: To examine the feasibility of transcatheter closure of multiple atrial septal defects using two Amplatzer devices simultaneously and to describe the importance and the role of two- and three-dimensional transoesophageal echocardiography in the selection and closure of such defects. METHODS: Twenty-two patients with more than one atrial septal defect underwent an attempt at transcatheter closure of their atrial septal defects at a mean+/-SD age of 30. 8+/-18.6 years (range 3.7-65.9 years) and mean weight of 56.6+/-25.5 kg (range 12.9-99 kg) using two Amplatzer devices implanted simultaneously via two separate delivery systems. During catheterization, two dimensional transoesophageal echocardiography was performed in all but one patient, during and after transcatheter closure, while three dimensional transoesophageal echocardiography was performed in six patients before and after transcatheter closure. RESULTS: Forty-four devices were deployed in all patients to close 45 defects (one patient with three defects closed by two devices). Two dimensional transoesophageal echocardiography was helpful in selection and in guiding correct deployment of the devices. The mean size of the larger defect, as measured by transoesophageal echocardiography was 12.8+/-5.9 mm and the mean size of the smaller defect was 6.6+/-3.0 mm. The mean size of the larger devices was 15+/-7.5 mm, and 8.4+/-3.7 mm for the smaller. Three dimensional transoesophageal echocardiography provided superior imaging and demonstrated the number, shape and the surrounding structures of the atrial septal defects in one single view. The median fluoroscopy time was 28.7 min. Device embolization with successful catheter retrieval occurred in one patient. Forty-four devices were evaluated by colour Doppler transoesophageal echocardiography immediately after the catheterization with a successful closure rate of 97.7%. On follow-up colour Doppler transthoracic echocardiography demonstrated successful closure in 97.5% at 3 months. CONCLUSIONS: The use of more than one Amplatzer septal occluder to close multiple atrial septal defects is safe and effective. The use of two- and three-dimensional transoesophageal echocardiography provided useful information for transcatheter closure of multiple atrial septal defects using two devices. Three-dimensional transoesophageal echocardiography enhanced our ability to image and understand the spatial relationship of the atrial septal defect anatomy.

Adolescent↗
PubMed1997

Gadopentetate dimeglumine and iodinated contrast media. Hemodynamic side effects after bolus injections in pigs.

RATIONALE AND OBJECTIVES: The use of bolus injections of contrast media containing gadolinium for magnetic resonance imaging and their potential use as x-ray absorbents require the evaluation of possible cardiovascular side effects. The hemodynamic reactions of high doses (0.6 mmol/ kg) of gadopentetate dimeglumine (gadolinium [Gd]-DTPA, Magnevist) were evaluated and compared with the side effects of ionic (diatrizoate: Urografin 76%) and nonionic (iopamidol, Solutrast 370) radiographic contrast media. METHODS: In 18 pigs, pressure and flow of the systemic and pulmonary circulation were monitored after intracardiac bolus injections (2-4 seconds) of dose volumes of 1.2 mL/kg of each contrast agent. RESULTS: All contrast media decreased the aortic pressure transiently (Gd-DTPA and diatrizoate: -25%, iopamidol: -10%; P < 0.01). Pulmonary artery pressure, cardiac output, and stroke volume increased for several minutes. The vascular resistance declined. Diatrizoate induced stronger and longer-lasting side effects (P < 0.01) than Gd-DTPA and iopamidol. CONCLUSIONS: Despite of similar osmolality, Gd-DTPA induced weaker side effects than equivolumetric applications of diatrizoate. Other than osmolality, other factors such as viscosity and chemotoxicity influence the side effects of contrast media.

Animals↗
PubMed1995

Heterotaxia syndrome and autosomal dominant inheritance.

Previous familial cases of recurrent heterotaxia have suggested an autosomal recessive or exceptionally X-linked or dominant inheritance. Here, we report six families including 18 affected members, consistent with autosomal dominant inheritance. Among these, four families have more than one case of heterotaxia. The other two families have one member with heterotaxia and at least one other affected member with an "isolated" heart malformation, which could be considered as a mild form of heterotaxia. In five families, the disorder is transmitted through two or three generations. In one family, the patients are of the same generation but are linked to each other by obligate carriers. We suggest a rule to classify these families with heart malformations, according to the etiologic factor involved (rule of precocity). This rule might be useful to other disruptions of morphogenetic processes.

Fatal Outcome↗
PubMed1990

Balloon dilation catheters.

Catheter therapy has gained an important role in the treatment of congenital heart disease. The cumulative experience with vascular and valvular balloon dilations has demonstrated low mortality and morbidity with short-term results similar to surgery. Currently, balloon dilation is an accepted treatment for valvular pulmonary stenosis, distal pulmonary artery stenosis, recurrent coarctation, rheumatic mitral stenosis, congenital valvular aortic stenosis, and intra-atrial baffle obstruction. Except for patients at high surgical risk, balloon dilation of native coarctation is considered investigational at most institutions but accepted at others. No conclusive evaluation is yet possible for dilation of bioprosthetic valves and membranous subaortic stenosis. Individual pulmonary veins appear undilatable. Various devices are available for closure of extra- and intracardiac communications. Transcatheter closure of aortopulmonary collaterals and arteriovenous malformations is now well established at some centers. In selected patients, therapeutic embolization of surgical shunts can replace surgery. Transcatheter closure of the patent ductus arteriosus has become routine at some centers. Nonsurgical closure of atrial and ventricular septal defects has entered clinical trials, and preliminary results appear very promising. Blade atrioseptostomy and foreign body retrieval are well established. Improvement of existing procedures and implementation of new concepts will consolidate the role of catheter therapy in congenital and acquired heart disease.

Aortic Coarctation↗
PubMed1989

Pulsed holmium laser ablation of cardiac valves.

Ablation efficiency and residual thermal damage produced by pulsed holmium laser radiation were investigated in vitro for bovine mitral valves and human calcified and noncalcified cardiac valves. Low-OH quartz fibers (200 and 600 microns core diameter) were used in direct contact perpendicular to the specimen under saline or blood. Etch rate was measured with a linear motion transducer. Radiant exposure was varied from 0 to 3 kJ/cm2. For 200-microns fibers, the energy of ablation was approximately 5 kJ/cm3 in noncalcified and 15 kJ/cm3 in calcified valves. Etch rates were dependent on mechanical tissue properties. Maximum etch rate at 1,000 J/cm2 was 1-2 mm/pulse at 3 Hz repetition rate. Microscopic examination revealed a zone of thermal damage extending 300 microns lateral into adjacent tissue. Thermal damage was independent of radiant exposure beyond twice threshold.

Animals↗
PubMed1989

Coil embolization to occlude aortopulmonary collateral vessels and shunts in patients with congenital heart disease.

Gianturco coils were used to embolize 77 vessels in 54 patients: 58 aortopulmonary collateral vessels, 14 Blalock-Taussig shunts, 3 arteries involved in pulmonary sequestrations and 2 venae cavae. Embolization resulted in total occlusion in 53 (69%), subtotal occlusion in 19 (25%) and partial occlusion in 3 (1 intentional). Two embolizations failed to reduce flow. Thus, 72 (95%) of 76 embolizations in which complete occlusion was the intended result resulted in total or subtotal occlusion. Analysis of the results demonstrates that completely occluded collateral vessels were longer and had a smaller diameter than did incompletely occluded vessels. Complications included six cases of inadvertent embolization to the pulmonary arteries (n = 5) or the aorta (n = 1); three were retrieved and three were left without symptoms. In addition, there was a case of severe hemolysis after intentional partial occlusion of a Blalock-Taussig shunt. The results demonstrate that coil embolization can be an effective procedure for managing a wide variety of aorto-pulmonary collateral vessels and shunts in children with congenital heart disease.

Adolescent↗
PubMed1988

Comparison of digital with conventional ventriculography for quantitative right ventricular studies.

To assess the feasibility of quantitative central venous digital angiocardiography, right ventricular spatial orientation, size, and shape were compared with measurements based on conventional angiocardiography, both obtained during routine cardiac catheterization in 21 children with various congenital heart defects. Without systematic error, correlations for end-diastolic and end-systolic volumes were excellent, at r = 0.986 and 0.969, respectively. Ejection fractions were similarly closely correlated. Premature ventricular contractions were common in conventional angiocardiography and absent in digital and angiocardiography. The amount of contrast medium was 36% of that used for conventional angiocardiography. Digital angiocardiography using reduced amounts of contrast medium given through a central venous catheter allows accurate assessment of right ventricular size and function.

Adolescent↗
PubMed1987

Acute complications of catheter therapy for congenital heart disease.

Although therapeutic catheter procedures for congenital heart disease are still developing, the number of procedures being performed allows statistically relevant review of the acute complications. Between January 1, 1984, and February 1, 1987, 417 such procedures were performed at The Children's Hospital, Boston; the age range of the patients was 1 day to 51 years (median 4 years, 6 months). Catheter procedures consisted predominantly of vascular dilations (peripheral pulmonic stenosis, 97; valvular pulmonic stenosis, 67; valvular aortic stenosis, 62; recurrent coarctation, 49) and embolizations (double umbrella device, 36; steel coils, 45). Overall, there were 50 acute complications (12%); 24 (6%) were major and 26 (6%) were minor. The mortality rate was 3 of 417 (0.7%). Complication rates varied between 4% for dilation of recurrent coarctation and 40% for dilation of aortic stenosis. The age of the patients was a factor in complications of vascular access (11 patients), 8 of which occurred in patients younger than 6 months (median 5), and in cardiac arrest and ventricular fibrillation (4 patients, 3 of whom were younger than 6 months [median 3]). No statistically significant trend toward diminishing overall complication rates was discerned over the 37 months of this study.

Acute Disease↗
PubMed1986

Percutaneous balloon valvotomy of congenital pulmonary stenosis using oversized balloons.

Percutaneous balloon valvotomy was attempted in 27 patients (aged 6 days to 19 years, median 2 years, 11 months) with unoperated typical valvular pulmonary stenosis using a balloon 7 to 60% (mean 30%) larger than the valve anulus. One patient had undergone a previous balloon valvotomy elsewhere. To achieve an oversized dilation diameter in three larger patients, two balloons were inflated side by side. Their "effective dilation diameter" was determined by the diameter of the circle with the same area as that of the oval enveloping the two balloons. A significant reduction of the transvalvular gradient occurred in all patients (mean +/- SD = 74.3 +/- 14.7%, range 33 to 100%). The average gradient of 65.0 +/- 19.0 mm Hg (mean +/- SD) fell to 15.9 +/- 7.6 mm Hg (0 to 30 mm Hg). Twenty-five of 27 patients had a residual transvalvular gradient of less than 25 mm Hg. The calculated valve orifice area increased by an average of 183 +/- 80%. No significant complications occurred. It is concluded that percutaneous balloon valvotomy with a balloon 20 to 40% larger than the valve anulus is the treatment of choice for typical congenital valvular pulmonary stenosis.

Adolescent↗
PubMed1985

Myocardial imaging by digital subtraction angiography for left ventricular mass measurement.

Digital ECG- and respiration gated background subtraction and image combination were used to visualize the myocardial wall in routine left ventricular angiocardiography. Muscle mass was computed from manually traced biplane endo- and epicardial contours according to the multiple slices algorithm. Experimental validation and first clinical applications are reported. In animal experiments (13 pigs, 16 to 25 kg) a close correlation to postmortem measurement was found: r = 0.894 and SEE = 7.4 g for end-diastole, r = 0.938 and SEE = 6.2 g for end-systole. The postmortem measurement was always within the 95%-confidence range of +/- 10%. In 16 patients (five days to 60 years, 3.2 to 81 kg) assessment of myocardial mass by myocardial imaging and conventional angiocardiography was compared. Conventional calculation based on manually outlined cavity contour and mean thickness of a lateral wall segment in the unprocessed angiogram. At end-diastole myocardial imaging and the conventional method correlated closely with r = 0.986 and SEE = 18.7 g. Conventional mass determination was inaccurate in end-systole (r = 0.928, SEE = 56.9 g) with values exceeding the diastolic ones by 26% +/- 19% (mean, SD), sometimes by up to 100%. Enclosure of the papillary muscle in the averaged wall segment probably leads to a mostly overrated mean wall thickness. There was no significant difference between diastolic and systolic results of myocardial imaging. In further investigations myocardial imaging showed good agreement to two-dimensional echocardiographic mass determination and, furthermore, has successfully been applied to study contraction pattern and to evaluate percentage of non-perfused muscle volume.

Angiocardiography↗
PubMed1984

Right ventricular imaging with digital subtraction angiocardiography using intraventricular contrast injection.

Angiocardiography is of considerable value in the dimensional analysis of the right ventricular (RV) cavity, but conventional angiocardiography requires large amounts of contrast medium. In this study digital subtraction angiocardiography was applied to biplane RV projections of 25 children with congenital heart disease after direct injection of a small dose of contrast medium. Volume measurements were compared with those obtained by conventional angiocardiography. The amount of contrast medium required was reduced to 30%, flow rate to 57% and ventricular ectopic activity to 60% of that used in conventional angiocardiography, and the degree of radiation exposure was reduced considerably. There was a good correlation for end-diastolic (r = 0.996) and end-systolic volume (r = 0.990) determined with both techniques. Digital subtraction angiography after selective RV injection allows accurate volume measurements of the right ventricle in children with congenital heart disease. The main benefits of this method are reduction of the amount of contrast medium, flow rate during injection, radiation and ventricular ectopic activity.

Adolescent↗
PubMed1984

Late results of valve xenograft conduits between the right ventricle and the pulmonary arteries in patients with pulmonary atresia and extreme tetralogy of Fallot.

Between 1975 and 1982, valve xenograft conduits were used to establish continuity between the right ventricle and the pulmonary arteries in 28 patients between the ages of 3 to 39 years (mean 14.7 years) with 4 hospital deaths (14%). The indications for operation were pulmonary atresia types I and II in 7, extreme tetralogy of Fallot with hypoplastic pulmonary artery and valvular ring in 10, secondary obliteration of the infundibulum following Waterston shunt in 4, pulmonary valve insufficiency after transannular right ventricular outflow tract patch in 5 and tetralogy of Fallot with anomalous coronary artery in 2. Twenty-one patients (87%) between 9 and 41 years of age (mean 17.4 years) were available for follow-up 1/2 to 8 years after operation. The late death incidence during the follow-up period was 8% (2/24). Postoperative cardiac catheterization, which included right and left ventriculogram and measurements of gradients, was performed in 14 patients 4 months to 6 years after operation. Four patients were in New York Heart Association (NYHA) class 1, 6 in class II and 4 in class III. The other 7 non-catheterized patients were in class II. There were resting peak systolic gradients of 15 to 35 mmHg in 4, 36 to 55 mmHg and more than 55 mmHg across the xenograft valve and the proximal anastomosis in 4 other patients. The right and left ventricular end-diastolic pressures (RVEDP, LVEDP) averaged 18 and 17.5 mmHg, respectively, in 3 patients. The mean ratio of PRV/PLV quotient in NYHA class I group was 0.3, in class II 0.45 to 0.7 and in class III greater than 0.7 (including 2 with residual VSD and pulmonary hypertension). Late densitometric studies for assessing pulmonary valve competence revealed regurgitant fraction of up to 40% of the total stroke volume in the absence of a residual shunt 2 to 4 years after conduit implantation. Three children underwent uneventful surgical replacement of calcified xenograft conduit 1 1/2 to 4 1/2 years after surgery with antibiotic-sterilized valve allograft. Four other patients have residual ventricular septal defects (VSD), 2 of them underwent surgical reclosure while the other 2 patients with pulmonary hypertension still have their residual VSD open.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1984

Polyamine induced suppression of erythropoiesis in uremia.

The effect of the polyamine spermine previously shown to suppress erythropoiesis in vitro was investigated in a long term animal experiment. Continuous application of spermine by intraperitoneally implanted microperfusion pumps caused a mild hypoproliferative microcytic anemia in normal rats. Furthermore, in 12 patients with advanced renal insufficiency spermine was shown to be markedly elevated. This, together with the results obtained in animal experiments, suggests that hypersperminemia is the reason for the impaired erythropoiesis in anemic uremic patients.

Anemia↗
PubMed1982

Quantitative analysis of structure and function of the cardiovascular system by roentgen-video-computer techniques.

A survey of the evolution of roentgen-video-computer techniques is given which was initiated by the development of videodensitometry by Wood and his associates. Following fundamental studies of the usefulness and limitations of x-ray equipment for quantitative measurements and the applicability of the Lambert-Beers law to x-ray absorption, videodensitometry has been used experimentally and clinically for various circulatory studies and has proved to be particularly valuable for the quantitation of aortic, pulmonic, and mitral valvular regurgitation. The second offspring of these techniques, so-called videometry, uses dimensional measurements from single and biplane angiocardiograms for the assessment of size, shape, and contraction pattern of the heart chambers. Volumes of the right and left ventricles can be determined clinically with a standard error of estimate below 10%. On the basis of these studies, normal values have been derived for all age groups, and they depict geometric changes of the growing heart. Cardiac index and ejection fractions proved to be age-independent biologic constants. Finally, methods for complete digital processing of video-image sequences in an off-line and real-time mode are described which allow digital image storage and documentation, dynamic background subtraction for contrast enhancement, and intravenous angiocardiography, in addition to functional imaging by parameter extraction from a matrix of pixel densitograms. Wall thickness and motion determinations, regional flow distribution measurements, and various image-composition techniques are also feasible.

Absorptiometry, Photon↗
PubMed1981

Catamnestic investigations in children with malformations of the gastrointestinal tract and the abdominal wall.

Catamnestic investigations were performed in 288 children with malformations of the gastrointestinal tract and the abdominal wall, among them 41 with oesophageal atresia, 41 with stenosis/atresia of the small and large bowel, 78 with anorectal malformations, 75 with Hirschsprung's disease, 28 with omphalocele and 25 with gastroschisis. In atresias/stenoses of the gastrointestinal tract both sexes were equally affected whereas boys were significantly more often affected in both Hirschsprung's disease (p 0.0005) and omphalocele/gastroschisis (p 0.05). The babies were more frequently preterm (p 0.025) than it was the case in controls. Parental age was not higher than the average parental age at time of delivery. Incidence of malformations was significantly higher in the relatives of our patients than in the average population and reached 20% (p 0.0005) in relatives of children with omphalocele/gastroschisis. Teratogenic effects of alcohol, diseases, X-rays and drugs during pregnancy could be suspected in several instances, whereas adverse effects of smoking, previous abortions and cycle disorders before pregnancy could not be established.

Abdominal Muscles↗