Klaus Brodda

A new method for detection of P waves in electrocardiograms

A new procedure for searching the P wave in the corrected orthogonal electrocardiogram (VCG) was developed on the basis of VCG representation in spherical coordinates. The time course of the angle azimuth shows a well defined configuration Pϕ which is suitable for searching the P wave. At least normal VCGs regularly show the Pϕ configuration even if P waves are not visible in any of the related amplitude curves. The validity of Pϕ for the P wave recognition is discussed by electrophysiological considerations, and it was tested by comparison of the time course of Pϕ with that of well visible P waves in the magnitude curve of the very same VCG. Superposition with disturbance vectors yielded that Pϕ is more stable against distortions than the P wave in the magnitude curve. A digital algorithm was examined by comparison with data obtained by visual evaluation and with the output data of a common computer program for the very same VCGs. Additionally, the P wave duration and the azimuth of the atrial repolarization vector were compared with related data taken from literature. The results show that P wave recognition by using the Pϕ configuration is a valid and reliable method.

Computeranalyse des korrigierten, orthogonalen Kardiogramms

ZusammenfassungNach der mathematischen Definition vektorkardiographischer Größen in der I. Mitteilung wird hier die Struktur eines Computerprogramms VCG zur vektorkardiographischen Ekg-Analyse dargestellt.Der Programmablauf wird in seinen einzelnen Schritten beschrieben. Insbesondere wird die Schleifenidentifikation näher erläutert, die einen wesentlichen Teil des Programms darstellt. Im Gegensatz zu anderen Computeprogrammen zur Ekg-Auswertung wird durch das Programm VCG ein Trenvektor zwischen der P-Schleife und der QRS-Schleife einerseits sowie zwischen der QRS-Schleife und der T-Schleife andereseits aufgesucht der sich als kleinster Momentanvektor der genannten Bereiche zeigt. Hierzu ist eine Serie von Abfragen erforderlich zum Ausschluß von Artefakten oder pathologischen Ekg-Konfigurationen, deren Verständnis durch ein Schaltdiagramm erleichtert wird. Gleiches gilt für die beiden UnterprogrammeVektor undWinkel, die den Hauptteil der Berechnungen durchführen. Die Abfragefolge, die zur Auffindung von Azimut und Elevation dient, stellt einem Teil des UnterprogrammsVektor zum Program VCG dar. Zudem wird in diesem Programmteil die Magnitude der jeweiligen Momentanvektoren berechnet. Das UnterprogrammWinkel ermittelt eine Reihe von Winkeln zwischen je zwei charakteristischen vektoriellen Größen.Ferner werden die Anordnunge der Ein-und Ausgabe der Daten erläutert, die eine optimale Nutzung der Ausgabeeinheiten einer Rechenanlage ermöglichen und die Ergebnisse vorsortiert zur weiteren statistischen Bearbeitung bereistellen.SummaryAfter mathematical definition of vectorcardiographic parameters in our first communication here the structure of the computing program VCG 3 for vectorcardiographic ECG analysis is presented.The single steps of the program are described. Especially, the identification of the loops is illustrated, which represents an important part of the program. In contrast to other programs for ECG evaluation program VCG 3 tries to find one separating vector between P-loop and QRS-loop and one between QRS-loop and T-loop. Separating vector is the vector with the smallest magnitude in each of these regions. To get these vectors, and to exclude artefacts or pathological ECG-configurations a serie of questions is necessarily programmed. These questions as well as the subroutinesVektor andWinkel-executing most of the calculations-are explained. A part of subroutineVektor serves to find the angles azimuth and elevation. Furthermore the magnitudes of every running vector are calculated in this part of program. SubroutineWinkel determines a set of angles between two respective vectors.The arrangement of input and output of data is explained which makes possible an optimal use of the computer, and which prepares the assorted results for further statistical treatment.

Untersuchung von Basisdaten an Weight-Watchers-Gruppen als Parameter für Langzeiterfolge der Gewichtsreduktion

The available data of members of Weight Watchers groups were statistically evaluated and their efficiency is discussed with respect to the underlying therapeutic concept. As a result of the data evaluation and the discussion of the literature it can be concluded: 1. The time of active membership in the group correlates with the weight loss. 2. Dropouts can be expected at the beginning of the therapy and have usually a greater obesity than other members. An early motivation has to consider the slower success in those people with a high degree of obesity. 3. A continuous motivation and re-motivation is of greatest importance to prevent any weight gain after the end of group therapy. This re-motivation program should be established within the group; members who succeeded in losing weight should return for meetings at regular intervals.ZusammenfassungBei Mitgliedern von Weight-Watchers-Gruppen werden die verfügbaren soziodemographischen Daten statistisch ausgewertet und auf ihre Aussagekraft bezüglich des zugrundeliegenden Therapiekonzeptes beurteilt. Aus den Untersuchungen und der vergleichenden Literaturdiskussion ergibt sich:1.Die Dauer der aktiven Teilnahme in einer Gruppe entscheidet über das Ausmaß des erzielten Gewichtsverlustes.2.Vorzeitige Aussteiger — Dropouts — sind zu Beginn der Therapie zu erwarten und haben meist ein höheres relatives Übergewicht als die übrigen Teilnehmer. Eine frühzeitige Motivation muß daher den bei stark Übergewichtigen sich nur langsam einstellenden Erfolg berücksichtigen.3.Wesentliche Bedeutung für einen Langzeiterfolg hat die regelmäßige Nachsorge, d.h. Remotivation, wenn das Zielgewicht erreicht ist. Diese Nachsorge sollte weiterhin innerhalb der Gruppe in regelmäßigen Abständen erfolgen.SummaryThe available data of members of Weight Watchers groups were statistically evaluated and their efficiency is discussed with respect to the underlying therapeutic concept. As a result of the data evaluation and the discussion of the literature it can be concluded:1.The time of active membership in the group correlates with the weight loss.2.Dropouts can be expected at the beginning of the therapy and have usually a greater obesity than other members. An early motivation has to consider the slower success in those people with a high degree of obesity.3.A continuous motivation and re-motivation is of greatest importance to prevent any weight gain after the end of group therapy. This remotivation program should be established within the group; members who succeeded in losing weight should return for meetings at regular intervals.

Untersuchungen zur Reliabilität von Mustererkennungs-Algorithmen für die P-Wellen orthogonaler Elektrokardiogramme

On the Reliability of Pattern Recognition Algorithms for ECGs Judging the performance of pattern recognition algorithms in ECG analysis on an objective basis still presents a severe problem because of the heuristic nature of the criteria used- The paper illustrates that problem by way of P-wave detectors for ECGs. We want to focus on the external reliability of the algorithms. The term external reliability is closely related to condition or robustness. Here we are interested in the variation of the output of an algorithm when the input data are slightly altered. This pertains to the problem of how the biological variance of the ECGs is mapped into the variance of algorithm output. We may say that an algorithm is not reliable if this biological variance is strongly distorted in the output data.

Kriterien für die Auswahl von Elektronischen Rechenanlagen für Biomedizinische Forschungsinstitute

Computers are now a recognized tool in biomedical research. They are used for the evaluation of data on one hand and on the other hand for data acquisition and control of experiments. Based on our experience, some suggestions concerning the structure of a mini-computer system suitable for a research laboratory are made. According to the two major classes of application, two sets or requirements arise. We argue that it is effective to use this system for data reduction and evaluation because a large percentage of tasks require program development or at least specific input data handling. Therefore, we call for a multi-user time-sharing system which should be equipped with a set of commands that enable the user to perform easily standard tasks such as editing compilation, loading and execution of programs. Some figures are given on memory size, disk file system and other peripherals. In the field of data acquisition and experiment control electrical and logical characteristics of the computer system are of greater importance than in data evaluation. The transient nature of experimental set-ups requires a high degree of adaptability of the systems hardware in regard to changing interface problems. We, therefore, suggest supplying a number of standard interfaces such as RS 232, “paper tape reader” and “paper tape punch”. These connections will generally not suffice so that for the development of custom interfaces it will be necessary to have easy access to the I/O-bus of the CPU, for example by predesigned logic which yields a set of simplified data and timing signals. The structure of the operating system for data acquisition is also discussed. We experienced that a single-user system in a basically non-realtime environment with modification for data acquisition via direct memory access or interrupt requests is sufficient in many cases and should be preferred to a complicated large-scale realtime system. But for some applications, especially for the purpose of control, such a realtime system should be available. Among several other requirements, the demand for the possibility of upgrading processor and memories is stressed. Hard- and software compatibility should be provided to a great extent in case of upgrading. We further argue for mixed hardware and own software development in order to build a suitable system at a reasonable cost. This concept is illustrated by discussing our own system which is basically a PRIME 300 multi-user system equipped with two slave systems. The two slave systems are mainly used for I/0 tasks. The experimental hardware is connected to the system by means of standard interfaces (RS 232, parallel I/0), by modified standard interfaces and by hardware developments of our own. Care was taken to provide for a comfortable analog I/0 system with a communication network to allow access to the computer from all laboratories. The standard operating systems were modified to incorporate the slave systems and the experimental equipment. In conclusion, we suggest that it is necessary to have an intimate knowledge of the hard- and software of the computer system in order to use all the resources of the system in the changing applications. This requires a hard-and software documentation that covers the whole system in great detail.