Hideo Miyahara

Evaluation of five computer programs in the diagnosis of second-degree AV block

Five electrocardiogram (ECG) analyzing systems were tested with a microcomputer-based ECG signal generator to assess the accuracy of the systems in interpreting Wenckebach periodicity. Although normal sinus rhythm with normal PR intervals and sinus rhythms with first-degree atrioventricular (AV) block were diagnosed by all five systems, second-degree AV block with classic Wenckebach periodicity was routinely misdiagnosed by four of the five systems. No system recognized the atypical Wenckebach periods in a total of 200 trials, misinterpreting the phenomenon as atrial fibrillation, supraventricular rhythm, sinoatrial block, and other rhythm disturbances. In advanced AV block and a variety of ventricular arrhythmias, none of the five systems diagnosed second-degree AV block with Wenckebach periods. Marked unsatisfactory performance with regard to the diagnosis of Wenckebach periodicity indicates the urgent need for accelerated and comprehensive testing of ECG diagnostic equipment. The present generating device was seen as an effective troubleshooter in optimizing the diagnostic competency of computerized ECG systems.

The reproducibility of interpretation of 10 computer ECG systems by means of a microprocessor-based ECG signal generator

The use of computer ECG systems has become widespread in Japan, and many new models are available. In order to provide a method for comparative evaluation, a microprocessor-based ECG signal generator was built. This generator was used to compare 10 of the computer ECG systems which are currently available in Japan. Since the generator can produce a precisely defined wave form, it is particularly suited for testing the reproducibility of diagnostic interpretation. Several deficiencies of some current ECG analysis systems were noted. Specifically in three systems, there was interference of the interpretation of morphology with the interpretation of rhythm when WPW-like patterns were analyzed. The current evaluation concentrates on the reproducibility of interpretation in the tested systems. As the library of test ECG patterns is expanded in the future, the technique will also become applicable to the evaluation of diagnostic accuracy.

A personal computer-based arrhythmia generator based on mathematical models of cardiac arrhythmia

A personal computer-based arrhythmia generator has been developed based upon mathematical models of modulated parasystole and the related equations. A system of nonlinear difference equations is used to generate the time series of RR intervals of ECG that contain normal as well as ectopic QRS waves. The ECG waveform is synthesized according to the computed RR interval and the type of QRS wave and output via DA converter in a real-time base. Various types of ECGs with ventricular ectopic beats and those with very long periods were generated by selecting values for a small number of model parameters. This method requires neither large RAM nor external memory for storing a library of arrhythmic ECGs. The theory, hardware design, software implementation on a personal computer, and experimental reconstruction of clinical ECGs based on the model are discussed.

A mathematical model of atrioventricular conduction block using the excitability recovery curve of the myocardial cell

A simple mathematical model of AV conduction block was constructed on the basis of single-cell electrophysiological experiments concerning the rate-dependent property of excitability of the AV nodal cells (the excitability recovery curve, ERC). This ERC was analogous to the phase response curve (PRC) of cardiac pacemaker cells, which the authors had previously used to construct a model of modulated parasystole. Computer simulation was used to reproduce the ERC. The single-cell ERC was then extended to the entire AV node, and this curve was used to formulate a mathematical model of AV conduction block as a nonlinear, first-order difference equation of the successive PR intervals of the ECG. This model predicted a variety of ECG patterns of AV conduction block: normal rhythm, first-degree block, and several second-degree blocks of complex Wenckebach periodicity in relation to the sinus rate and the shape of the ERC. By assuming this model it was possible to identify the underlying ERC of actual ECGs with complex Wenckebach periodicity.

Two types of distribution patterns of bigeminy and trigeminy in long-term ECG: a model-based interpretation

Two types of distribution patterns of bigeminy and trigeminy are found in analysis of long-term ECG. To investigate the mechanism underlying this finding, a simplified equation of a modulated parasystole model was used and symbolic solutions for cyclic VPC patterns were obtained. The map of these solutions in a model parameter plane showed two different solutions for bigeminy, four kinds of trigeminy, two kinds of quadrigeminy, combinations of these patterns, and apparently normal ECG. These results are used to explain the features of the distribution patterns.

WinArrhythmia: A Windows based application for studying cardiac arrhythmias

We have developed Windows-based software for ECG training as a tool in teaching physiology. A standard user interface allows the user to choose which arrhythmia to review. The arrhythmia is drawn in real time with sound beeps synchronized to R waves. The system also presents a brief summary or multiple choice question corresponding to the arrhythmia. A ladder diagram shows how simulate the conduction system, which consisted of 4 modules characterized by 4 parameters: automaticity, refractory period, antegrade- and retrograde-conduction time. This system has proved both useful and effective for training medical students in ECG interpretation of arrhythmias.

A 15-year follow-up study on the outcome in patients with early rheumatoid arthritis

This study aimed to investigate the natural course of early rheumatoid arthritis (RA) after treatment for 15 years based on the present data of patients who had been enrolled in a 1 year study of early RA conducted by the Japan Rheumatism Foundation in 1981 and 1982. An examination form was mailed to each doctor who had participated in the previous study requesting them to record the present data of the patients. The patients were requested to fill out the AIMS2 questionnaire. Patients had been randomly assigned into three treatment groups: those treated with gold, with d-penicillamine and without slow acting antirheumatic drugs (SAARDs). Information was obtained concerning 74 of 161 patients who had completed the previous 1 year study. Clinical remission was observed in 20 of 74 patients. The current status of RA by physician’s assessment was reported to be well controlled in 32 of 48 cases (66.7%); however, no remarkable improvement was seen in erythrocyte sedimentation rate (ESR, and the number of painful joints compared with the values at entry 15 years previously. Radiographical stages showed progression and the average score of AIMS2 had deteriorated in most cases. High ESR, progression of joint damage and positive rheumatoid factors at the early stage of RA were suggested to be factors relating to QOL deterioration. These results suggest that it would be difficult to modify the natural course of RA by currently used treatment strategies with SAARDs.

Simulation system of arrhythmia and HRV analyzer

We aim to integrate our interactive simulation systems of arrhythmia and heart rate variability (HRV) analyzer by a Windows message to understand the theoretical mechanisms of arrhythmia and HRV. The arrhythmia simulator (250 kB, Visual Basic 6.0) was composed of 4 normal and 2 ectopic foci. The electrical activity of each cell was modeled by the conduction speed and the phase response curve. The ECG waves were graphically plotted with impulse conduction on a ladder diagram. An RR interval was sequentially messaged to the HRV analyzer (90 kB, Visual Basic 6.0), which automatically calculated power spectrum (PS) of HRV by Lombs method and FFT. The power of VLF, LF and HF bands, mean, SD and range were listed. The HRV analyzer interactively showed the variation of PS influenced by a baseline trend of RR intervals, ectopic beats, sampling rate, the number of samples and window function