Hajime Oguri

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.

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.

Experimental Studies on the Antiarrhythmic Action of a Lidocaine Analog

The electrophysiologic properties of a lidocaine analog (Kö 1173) was experimentally studied in 41 mongrel dogs. The threshold for occurrence of repetitive ventricular extrasystoles was significantly raised by the administration of 2, 4, and 8 mg/kg of the drug, while atrioventricular and intraventricular conduction times were not affected. After ligation of the anterior descending branch of the left coronary artery, the threshold for occurrence of repetitive ventricular extrasystoles was significantly lowered before the administration of Kö 1173 but it returned to control values after the administration 1 mg/kg of the drug. The strength-interval curve shifted profressively to the right when the dose was increased from 2 to 4 and 8 mg/kg. These results indicate that Kö 1173 prevents the decrease in threshold for occurrence of repetitive ventricular extrasystoles in acute coronary insufficiency at a dose which does not affect the conduction system.

Body surface distribution of QRS deflection areas in experimental ventricular preexcitation

The utility of QRS isoarea maps for recognition of preexcitation sites was evaluated in chronic experiments in dogs. Pacing electrodes were surgically implanted on the atrium and ventricular sites near the AV ring. Electrocardiograms from 192 torso sites were simultaneously recorded during pacing of the atrium together with each of the ventricular sites. Time phase of atrial and ventricular stimuli was varied to yield both preexcitation with clear delta waves and more subtle forms of preexcitation with sites activated earlier than normal but after onset of the normal QRS. QRS area maps were determined by integrating QRS amplitudes at 1 msec intervals over the QRS duration. Results showed a systematic relation between the body surface location of the minimum in the QRS area maps and the preexcitation site. In additon there was a linear relation between the magnitude of maximum and minima in the QRS isoarea maps over different degrees of preexcitation, and the slope of curves showing this relation differed for different sites of preexcitation. Findings suggest that a single display of the QRS isoarea map may permit identification and localization of preexcitation including subtle forms occurring after the onset of the QRS.

Body surface potential distributions in posterior ventricular pre-excitation***

Waveform of the QRS complex during ventricular pre-excitation is subject to the influence of both the site of pre-excitation and the time of pre-excitation relative to that of excitation via the normal AV path. This paper reports a case in which lead V1 of the electrocardiogram (ECG) could be altered from an R to an rS pattern by the administration of atropine sulfate. The provable mechanism was that of reduced conduction time in the normal AV path with altered time phase of normal excitation and pre-excitation. This mechanism was simulated in experiments on dogs and yielded similar findings. Body surface mapping in both the patient and the dogs provided evidence that pre-excitation could be recognized by that means with varied time phase of normal excitation and pre-excitation. It was demonstrated that the QRS complex of right sided precordial leads could be altered from an R to an rS pattern by altering the time phase of normal excitation and pre-excitation of the posterior ventricular wall. This alteration was related to the degree to which negative potentials on the anterior chest wall due to right ventricular breakthrough of normal activation developed in relation to the time of pre-excitation.

Computational Reconstruction of Body Surface Isopotential Maps in Myocardial Infarction: Comparison between Nontransmural and Transmural Infarction

The relationship between the lack of electromotive force in myocardial infarction and body surface potential distribution was investigated on maps reconstructed from a simulated heart model and transfer impedance vectors of human torso model. The heart model, a cluster of 3-mm cubic blocks, was stored in the memory of a computer. Transfer impedance vectors between 81 lead points on the human torso model and 392 positions covering ventricular areas in the torso were measure. Body surface potential values were calculated mathematically by summing up scalar products between the electromotive force of the heart model and the measured transfer impedance vectors. Thus, reconstructed maps changed in their patterns with the alternation in lacation and/or extent of infarcted region in the heart model. In particular, the appearance of the abnormal potential minimum, which projects the infarcted region in the heart model onto the torso surface, was characteristic in both transmural and subendocardial infarction. In addition, delayed activation in the intact layer of the epicardium overlying the infarcted region produced a potential maximum on the same place as the abnormal potential minimum appeared previously.