Mitsuharu Okajima

Body surface isopotential mapping in Wolff-Parkinson-White syndrome: Noninvasive method to determine the localization of the accessory atrioventricular pathway

The body surface isopotential maps of 22 patients with WPM syndrome were obtained from the 85 unipolar lead ECGs using the on-line minicomputer system newly devised by the authors group. The map patterns were classified into three types-I, II, and III (Type I, eight; Type II, seven; Type III, three; and unclassified, four cases). In Type I, the back surface displayed the negative potential throughout the entire ventricular activation, and at the terminal stage the lower precordial area displayed the positive potential and the upper precordial area, the negative one. Type II was characterized by two longitudinal lines, one staying at its place on the back and the other moving right to left on the precordial area following the process of ventricular activation. In Type III, the right precordial area displayed negative potential in the early stage, and in the terminal stage the upper part of the right side of chest surface displayed positive potential and the lower part, negative potential. It was surmised from these patterns that the pre-excited area was located at the posterior region of the ventricles in Type I, at the right ventricle in Type II, and the right ventricular base near the posterior margin of the ventricular septum in Type III. Type A patients in the conventional ECG classification fell under Type I; Type C patients, under Type III; Type B patients under either Type I or Type II.

Computer simulation of the propagation process in excitation of the ventricles.

Simulation by a digital computer of propagated excitation in the ventricular myocardium has been accomplished. Experience with the program in normal conduction and in one example of abnormal conduction, an extrasystole, is presented. Results of the simulation process were in harmony with observations in animal experiments. This justifies attempts to apply this scheme to the analysis of abnormal ventricular excitation caused by other disturbances. A crucial role of the Purkinje network in determining the course of excitation spread was recognized in the simulated process of both normal beats and extrasystoles. New knowledge is expected from this scheme when applied to other types of abnormal excitation. The possibility of combining the scheme with a method of reconstruction of QRS complexes by means of “transfer impedance” values was pointed out.

Cardiac arrhythmias in healthy children revealed by 24-hour ambulatory ECG monitoring

SummaryAmbulatory electrocardiographic monitoring was performed on 360 healthy children, from newborn infants to junior high school students. They were divided into five groups by age: group A, 63 newborn infants on the first day of life; group B, 50 infants aged 1–11 months; group C, 53 kindergarten pupils aged 4–6 years; group D, 97 primary school pupils aged 9–12 years; and group E, 97 junior high school students aged 13–15 years.The maximal and minimal heart rates were significantly greater in infants than in older children. Sinus arrhythmia was recorded in every child. One boy in group E had an episode of sinus arrest for three seconds without any symptoms. First-degree and Wenckebach type second-degree atrioventricular blocks were not detected in group A and group B, but were most frequent in group E, especially during sleep. Supraventricular premature contractions (SVPCs) were the most common type of arrhythmia detected in this study. More than half of the children had at least one SVPC per 24-h monitoring period, and there were many children with frequent SVPCs in group E. The incidence of ventricular premature contractions (VPCs) in children of groups A and E was rather higher than in the other groups. Ventricular tachycardia was not recorded in any child except one newborn infant who had a couplet of VPCs without symptoms.Each group had different types and incidences of arrhythmias. There was a rising incidence of arrhythmias with advancing age, except in the neonatal period.

A practical microcomputer-based mapping system for body surface, precordium, and epicardium☆

Abstract A practical microcomputer-based mapping system is introduced for three different potential mapping applications: (1) an array of 48 AgAgCl electrodes for epicardial mapping, (2) a system of 64 AgAgCl dry electrode for precordial mapping, and (3) an 87-electrode configuration for general body surface potential mapping. The compact, mobile microcomputer system with multiplexing and sample-and-hold techniques makes it possible to construct high-resolution maps from simultaneously sampled ECG potential data in clinical and experimental conditions. It takes only 20–25 min from the beginning of electrode placement to the completion of potential or isochronic map displays on the graphic terminal. Digital magnetic cassette tapes are used as external storage mediums which permit interchange of stored data on a larger computer.

Computer pattern recognition techniques: electrocardiographic diagnosis

The use of programmed digital computers as general pattern classification and recognition devices is one phase of the current lively interest in artificial intelligence. It is important to choose a class of signals which is, at present, undergoing a good deal of visual inspection by trained people for the purpose of pattern recognition. In this way comparisons between machine and human performance may be obtained. A practical result also serves as additional motivation. Clinical electrocardiograms make up such a class of signals. The approach to the problem presented here centers upon the use of multiple adaptive matched filters that classify normalized signals. The present report gives some of the background for the application of this method.

Computer Pattern Recognition Techniques: Some Results with Real Electrocardiographic Data

Automatic interpretation of electrocardiograms is a particular example of the application of digital computers to medical diagnosis; this paper describes our experience with a new approach involving pattern recognition techniques. The program employs a multiple adaptive matched filter system with a variety of normalization, weighting, comparison, decision, modification, and adapting operations. The flexibility of the method has permitted study of effects of experimental variations of these operations on the pattern classification process to simulate human interpretation of electrocardiograms more closely. These programs have been successfully applied to actual electrocardiograms from cardiac patients. These researches in application of computer pattern recognition techniques to the automatic interpretation of electrocardiograms have been undertaken because they join together three fields of great interest. First, an example of artificial intelligence or a self-organized system is represented by the adaptive filter memory, together with the related decision operations. Second, we consider our program to be a model of complex sensory discrimination and use our intuition of human psychology as a guide when selecting one of several possible program mechanisms to overcome temporary obstacles. Third, the automation of medical diagnosis is a rapidly developing and promising field contributing to medical progress. This paper pays particular attention to the third of these objectives. The present state of computer analysis of electrocardiograms is mainly one of orthogonalization of the spatial vector, point recognition to separate the various component waves, parameterization, in one case via Fourier techniques, and then statistical matrix analysis.

Atrial T(Ta) wave and atrial gradient in patients with A-V block

The P and the Ta waves of two patient groups with A-V block were magnified with a direct-current amplifier and recorded at a high paper speed. In Group A patients (those without serious cardiovascular complications except A-V block) the P and the Ta waves were recorded in the opposite direction in every lead and there was a linear relationship between the amplitude of the P and the Ta waves. The atrial gradient was nearly zero. There existed a positive correlation between the P + Ta time and the P-P interval. In Group B patients (those with serious cardiovascular complications besides A-V block) there were significant differences in the Ta wave from Group A with respect to form, polarity, amplitude, duration, and the relationship between the Ta and the P waves. The atrial gradient was markedly large. Careful attention should be paid to the deviation of the PQ segment caused by the Ta wave in daily ECGs to detect atrial abnormalities. The Ta wave extends into the ST segment and, while describing the deviation of the ST segment, the influence of the Ta wave should be kept in mind.

On the Genesis of the Absolute Ventricular Arrhythmia Associated with Atrial Fibrillation

Genetic factors in the formation of the long R-R interval in ventricular arrhythmia associated with atrial fibrillation were investigated in the isolated rabbit heart which was perfused using Langendorffs technique. The trans-membrane action potentials recorded from a single cell within the A-V node or within its vicinity were analyzed, and contiguous bipolar-lead electrograms simultaneously recorded from the right atrium and ventricle. Atrial fibrillation was induced by the combined application of acetylcholine solution and electrical stimulation. Atrial excitation was mainly blocked in the right atrium and in the anterior half of the A-V node. To clarify further the time-correlation between the right atrial electrogram and the A-V nodal responses, the pattern of atrio-ventricular conduction was studied by applying only the electrical stimulation at high frequency without acetylcholine. The conduction was mainly blocked in the same sites as in the above experiment and the pattern of the conduction block in Wenckebach rhythm was observed. The conduction block within the anterior half of the A-V node may be the most important factor in producing the long R-R interval in atrial fibrillation. It was shown that the pattern of the conduction block can be explained by the Wenckebach rhythm.

Electrocardiographic changes in pulmonary emphysema: Effects of experimentally induced over-inflation of the lungs on QRS complexes

Summary Seventeen dogs were anesthetized with sodium pentobarbital. In these dogs, over-inflation of the lungs was experimentally induced by blocking the exhaust of a respirator. Dislocation of the heart during over-inflation of the lungs was prevented by fixing the heart on a supporting rod. Three pairs of bipolar electrodes were implanted either on the anterior or posterior wall of the ventricles. They were used as the X- (left-to-right), Y- (foot-to-head), and Z- (front-to-back) dipoles while passing alternating currents (50 μA, 20 Hz.). The electrical signals generated from these dipoles were recorded with the McFee-Parungao lead system. The same lead system was used for recording electrocardiograms. The effects of the over-inflation of the lungs upon the potentials generated from the dipoles and upon the QRS complexes of the electrocardiograms were investigated. Potentials generated from the X-dipole on the anterior or posterior wall decreased during over-inflation of the lungs, in parallel with the R wave in Lead X. Similar reduction was found between the potentials generated from the Y-dipole on the anterior or posterior wall and the R wave in Lead Y. In contrast, opposite changes were found between the potentials generated from the Z-dipole on the anterior or posterior wall. There was a decrease of the potential generated from the Z-dipole on the anterior wall and an increase of that from the Z-dipole on the posterior wall. Similar contradictory changes were found between the R and S waves in Lead Z. The parallelism between changes in the potentials generated from the dipoles and the R and S waves of three orthogonal leads was found to be statistically significant (correlation coefficients ≥ 0.80. Since the position of the heart was fixed, the changes in the potentials generated from the dipoles induced by over-inflation of the lungs could be attributed to the increased electrical resistance of the lungs. The same explanation may be applied to those changes in the R and S waves which were closely related to the changes in the potentials generated from the dipoles. On the basis of resemblance of the changes in the QRS complexes between pulmonary emphysema and the experimentally induced over-inflation of the lungs, increased resistance of the lungs may contribute to changes in QRS complexes in pulmonary emphysema.

Genesis of body surface potential distribution in right bundle branch block

In order to investigate the specific sites of conduction block in the three types (I, II, III) of right bundle branch block (RBBB) classified by body surface isopotential maps, the simulation of ventricular propagation process and mathematically reconstructed maps were used. Four assumptions were introduced from the results of clinical observations and animal experiments. The maps reconstructed from two of these assumptions, in which the conduction block was placed on the main stem of the right bundle branch, showed two different patterns at late stages of excitation, and these two kinds of map resembled Types I and II in clinical maps, respectively. The maps reconstructed from the other two assumptions, in which the site of the conduction block was located mainly in the Purkinje system of the right ventricular free wall, resembled Type I at the late stage of excitation in one of two assumptions and agreed with Type III through all stages of excitation in other case. Based on the above results, it is speculated that the differences of ranges and degrees of conduction block ascribed to abnormal activation in the Purkinje system of the right ventricular free wall are responsible for the genesis of clinical RBBB map patterns.