Biomedical subjects

S M Maas

Publications and source records attributed to S M Maas.

21 records · Page 2Linked to original sources

PubMed1990

Detection of ventricular tachycardia using scanning correlation analysis.

Cross correlation is an accurate method for distinguishing normal sinus rhythm (NSR) from ventricular arrhythmias. The computational demands of the method, however, have prohibited development of an implantable device using correlation. In this study, temporal data compression prior to correlation analysis was used to reduce the total number of computations. Unipolar and bipolar intracardiac electrograms of NSR and 23 episodes of ventricular tachycardia (VT) from 23 patients were obtained from a right ventricular apex electrode catheter during routine electrophysiology studies. The data were filtered (1-11 Hz), digitized (250 samples/sec) and temporally compressed to 50 samples/sec. Data compression removed four out of every five samples by only saving the sample with the maximum excursion from the last saved sample. The average squared correlation coefficient (r2) was computed for the NSR and VT episodes using each patient's NSR waveform as a template. In all 23 patients, the r2 values showed large separation between NSR versus VT in both unipolar (0.93 +/- 0.05 vs 0.20 +/- 0.16, P less than 0.005) and bipolar (0.91 +/- 0.07 vs 0.17 +/- 0.11, P less than 0.005) electrode configurations using template lengths of 80% the intrinsic interval (avg +/- SD). Narrow templates (40% intrinsic interval or less) often resulted in multiple r2 peaks during each heart cycle and degraded the r2 separation (n = 10, P less than 0.005). High pass filtering at 3 Hz also degraded the r2 separation (n = 10, P less than 0.05). Standard noncompressed correlations indicated that data compression had negligible effects on the results. Thus, a computationally efficient cross correlation method was found to be a reliable detector of VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Intrauterine fetal death due to Farber disease: case report.

We report a case of Farber disease in a fetus who died in utero at a gestational age of 29 weeks. Macroscopic examination showed moderate postmortem changes in a microcephalic female fetus (46,XX) with mild internal hydrops, two vessels in the umbilical cord, and a moderately enlarged, relatively well-preserved spleen. Microscopic examination showed foamy cells in the spleen. Electron microscopic examination revealed the presence of Farber bodies within these foamy cells. Enzyme studies of the fetus were not possible because all tissues were formalin fixed. Lipids were extracted from formalin-fixed tissues and increased levels of ceramide and the presence of hydroxyceramide in tissue of the spleen, liver, and lung were found. Glucosylceramide was not increased excluding saposin-precursor-deficiency. Because of these findings, both parents were tested for acid ceramidase activity in their leukocytes. They both had markedly reduced enzyme activity consistent with heterozygosity for Farber disease. To the best of our knowledge, this is the first published case of Farber disease in Dutch nonconsanguineous parents.

Acid Ceramidase↗

PubMedDate not supplied

Tachyarrhythmia therapy utilizing electrical stimulation: a review.

The review is structured in such a way as to fall naturally into four main sections. These are as follows: clinical overview of the common mechanisms leading to the generation of tachyarrhythmias; commonly used sensing techniques and algorithms for the detection of tachyarrhythmias; electrical stimulation algorithms used to terminate many of the rhythms; existing implantable devices and a brief look at the future. The clinical overview introduces the reader unfamiliar with tachyarrhythmias to such mechanisms as sinus tachycardia, supraventricular tachycardias (SVTs), ventricular tachycardia, 'torsade de pointes', and ventricular fibrillation. SVT includes paroxysmal SVT, atrial flutter, atrial tachycardia and junctional tachycardia (enhanced automaticity). Also there is a brief introduction to alternative therapies (drugs, surgery etc.) The sensing techniques section covers input signal processing to enable the R wave to be adequately detected; while the tachycardia detection algorithms section discusses such areas as simple rate detect, rate of change of rate detect, stability of rate, the so-called probability density function technique and some other more complex detection algorithms. The section on electrical stimulation algorithms used for tachycardia therapy discusses burst pacing techniques, special cases such as automatically decrementing bursts and automatically incrementing bursts, defibrillation shock therapy (since fibrillation is a form of tachyarrhythmia) and several other more complex algorithms. The review finishes up with a discussion of current implantable antitachy pacemakers and defibrillators. There is also a speculative look at the future to enable the reader to obtain a full picture.

Algorithms↗