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A van Oosterom

Publications and source records attributed to A van Oosterom.

At least 91 records · Page 5Linked to original sources
PubMed1987

Body surface maps and the conventional 12-lead ECG compared by studying their performances in classification of old myocardial infarction.

The performance of body surface potential maps and the 12-lead ECG in the detection of old myocardial infarction has been compared in a two-group (54 normals; 52 infarctions) classification procedure (linear discriminant analysis). Three methods for data reduction of body surface maps were compared: 1) time integration, 2) one-step reduction in eigenvectors and 3) two-step reduction in spatial and temporal eigenvectors. Features were taken from the reduction variables by a stepwise selection procedure. From 90% to 93% correct classifications could be obtained using three features from the map data over the initial 30 ms (Q interval) of the QRS wave for all three methods considered. Using the 100 ms (QRS) interval 86% correct classifications were obtained using method 1, and up to 90% and 87% for methods 2 and 3, respectively. In a further analysis the classification based on body surface maps was compared to the one based on the 12-lead ECG. The 12-lead ECG was treated as a restricted set of the body surface mapping leads, so the same methods of data reduction, feature extraction and classification could be applied to both sets of data. Applying method 1 (time integration) 89% correct classifications were obtained using data taken from the 30 ms interval of the 12-lead ECG and a subsequent reduction to three features. When using the 100 ms interval the result was 79% also using three features. The results of method 2 applied to the 12-lead ECG were 89% (30 ms interval, three features) and 78% (100 ms interval, three features).

Electrocardiography↗
PubMed1986

Spatial filtering of the fetal electrocardiogram.

One of the basic problems in the analysis of the rhythm and the shape of the fetal ECG (FECG) is the interference caused by the electrical activity of the maternal heart (MECG). Methods devised for suppressing the maternal signals in the abdominally recorded leads obviously have to rely on differences in the characteristics of both kinds of signals. In the past various differences have been employed for this purpose such as differences in wave shape, frequency content and source location. The method presented here is based on the latter principle. The electrical sources of the fetal and maternal heart are clearly separated in space. By employing multiple abdominal leads, a linear combination of the recorded signals can be formed which acts effectively as a spatial filter. As such the filtering characteristics depend exclusively on the separation inside the human body (the electrical volume conductor) and, as such, can be expected to be independent of the temporal aspects of the recorded signals. In particular, the obtained filter is unaffected by the occurrence of ectopic beats in either the fetal or the maternal heart. The determination of the required filter (weighting coefficients) is carried out by using the technique of singular value decomposition (SVD) of the data matrix representing the sampled input signals. The filter effectively suppresses the maternal component in the filter output and optimizes the fetal component. The properties of this filter are demonstrated.

Electrocardiography↗
PubMed1986

The potential distribution generated by the fetal heart at the maternal abdomen.

The pathways along which the electrical currents generated by the fetal heart are conducted to the surface of the maternal abdomen are not known. As a consequence, in recording the fetal electrocardiogram (FECG) it is hard to predict where electrodes should be placed in order to obtain an optimal signal. The amplitude of the FECG varies with gestation, and there is a large interindividual variability in the amplitude of the FECG and in the optimal recording site among subjects within the same gestational age. Attempts have been made to explain these phenomena in terms of volume conduction. In this research the complete potential distribution on the maternal abdomen is studied in connection with the geometrical configuration of the electrical source (fetal heart) and the volume conductor (surrounding tissues). For a small group of pregnant women the abdominal FECG is recorded simultaneously in 32 leads during a period of about one minute, once every two weeks from 20 weeks of gestation onwards. A spatial filtering technique which combines information of all 32 leads is used to provide a trigger of the fetal QRS complexes. Using this trigger, an average fetal complex is constructed for each lead by time coherent averaging, after subtraction of the maternal contribution. These average fetal complexes are combined to plot the complete potential distribution generated by the fetal heart at the maternal abdomen (fetal body surface map, FBSM) at any given time instant during the fetal cardiac cycle. At these recording sessions the geometry is carefully quantified by making transverse scans every 2 cm with a compound echo scanner. The contours of fetal head and body, the placenta and the uterus are manually drawn on hardcopies of the video display images. Real time echoscopy is used to support the identification of the geometry. The contours are fed into a computer using a graphics tablet. The three dimensional surfaces of fetus, placenta and uterus are separately represented by a triangulation of the respective contour lines. Figures 5 and 6 show an example of the triangulated representation of the recorded geometry. Figure 7 shows the average fetal complexes of an individual at 26 weeks of gestation, plotted at the site where they have been recorded.(ABSTRACT TRUNCATED AT 400 WORDS)

Abdomen↗
PubMed1985

Mitoxantrone as first-line chemotherapy in advanced breast cancer: results of a collaborative European study.

Mitoxantrone (Novantrone; dihydroxyanthracenedione) is a substituted anthraquinone with a spectrum of activity similar to doxorubicin in experimental tumors. One hundred and seventy three patients with advanced breast cancer and no prior cytotoxic therapy for advanced disease entered a phase II study of mitoxantrone, 14 mg/m2 i.v. repeated every 3 weeks. At the time of this analysis 116 patients were evaluable. Eight patients achieved a complete response and 27 a partial response, the overall response rate being 30% (95% confidence limits: 22-39%). The median time until response was recorded was 15 weeks. The median duration of response was 74+ weeks and the median time to progression or death for all 116 patients was 22+ weeks. Mitoxantrone was well tolerated with myelosuppression as the dose-limiting toxicity. The most frequent non-haematological toxicities were nausea and vomiting (65%) but they were rarely severe. Total alopecia occurred in only 6% of the patients. Four patients developed clinically significant evidence of cardiotoxicity after cumulative mitoxantrone doses of 174-256 mg/m2. Thus, mitoxantrone offers comparable efficacy and less acute toxicity than the most active single agents currently available in the treatment of advanced breast cancer.

Adult↗
PubMed1985

Phase II study of elliptinium in metastatic soft tissue sarcoma.

A phase II study was carried out with 9-hydroxy-methyl-elliptinium (9-HME) in metastatic soft tissue sarcoma. The dose was 100 mg/m2 weekly in 1 1/2 hr intravenous infusion protected from light. Nineteen cases were evaluable for response, all previously treated with other chemotherapy regimens. No remissions were seen. Major toxicities were nausea and vomiting, dryness of the mouth and anorexia. It is concluded that 9-HME is not an effective drug in metastatic soft tissue sarcoma.

Adult↗
PubMed1985

Phase II study of cisplatin in advanced osteogenic sarcoma. European Organization for Research on Treatment of Cancer Soft Tissue and Bone Sarcoma Group.

The activity of cisplatin (CDDP) against advanced osteogenic sarcoma was evaluated in 37 of 50 patients registered by the members of the European Organization for Research on Treatment of Cancer Soft Tissue and Bone Sarcoma Group between 1979 and 1982. All patients had measurable lung metastases. Thirty-one patients (84%) had received previous chemotherapy consisting mainly of high-dose methotrexate, doxorubicin, and vincristine. CDDP (100 mg/m2) was given as a 24-hour continuous infusion every 3 weeks for a minimum of two cycles, with appropriate fluids and diuretics. In the absence of impairment of the renal function and/or myelosuppression, the dose could be escalated by 20%. The overall response rate was 19% (seven responses among 37 patients), with one complete remission for 51 weeks and six partial remissions from 12 to 26 weeks. The median number of courses of CDDP administered was three, ranging from two to 11. Of 143 courses administered, only 18 (12%) had to be modified because of toxicity. In 16% of the patients some transient impairment of the renal function was observed. CDDP adds to the limited number of chemotherapeutic agents with useful properties in osteogenic sarcoma, and CDDP-containing combination chemotherapy regimens should be actively investigated.

Adolescent↗
PubMedDate not supplied

Muscle electric activity. II: On the feasibility of model-based estimation of experimental conditions in electromyography.

From regular one-channel registrations of single muscle fiber action potential no measures on the recording configuration can be derived. When multichannel recordings are made, experimental parameters such as the distance between muscle fiber and needle electrode can be estimated. With the help of a volume conductor model, the single fiber activity at each of the electrodes can be predicted as a function of the recording conditions. Within known physical and physiological constraints such a model approach can be inverted (the inverse model) and used to estimate basic experimental conditions. From eight simultaneous single fiber action potential recordings we estimated (a) the distance between fiber and needle, (b) the axial position of the needle with respect to the muscle fiber, (c) a factor related to the muscle tissue anisotropy, and (d) a factor combining the muscle fiber diameter and the effective muscle tissue conductivity. With the help of a model describing the influence of the needle shaft it is made plausible that the needle inhomogeneity influences the results of the proposed procedure.

Action Potentials↗