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H Tsunakawa

Publications and source records attributed to H Tsunakawa.

At least 19 recordsLinked to original sources
PubMed1995

Effects of early coronary reperfusion on the time course of signal-averaged electrocardiogram after myocardial infarction and its relation to late arrhythmic events, effects of early coronary reperfusion on signal-averaged ECGs.

The effect of early reperfusion on the time course of signal-averaged ECG was examined in 90 patients with myocardial infarction. Abnormal signal-averaged ECG disappeared more frequently (p < 0.05) and earlier in cases with early reperfusion than in those without. Serious arrhythmic events in the late phase (> 7 days) occurred in patients with abnormal signal-averaged ECG, but not in cases with early reperfusion. These results indicate that dynamic changes in tissue structure and the physiological state of viable muscles after early reperfusion produce different time courses for signal-averaged ECG. The risk of arrhythmic events among patients with abnormal signal-averaged ECG seems to be lower in cases with early reperfusion than in those without.

Aged↗
PubMed1995

[Clinical value of signal averaged electrocardiogram for the prediction of ventricular tachycardia after myocardial infarction].

One of the most important predictors for mortality after myocardial infarction is the occurrence of malignant ventricular tachyarrhythmias. Reentry has been shown to play a major role in the development of ventricular tachycardia (VT) in the chronic phase of myocardial infarction. Signal averaged electrocardiogram (SAE) may reveal the substrate for VT, that is, the delayed and fragmented ventricular activation around the infarcted area. Since Simson's report, the relation between the detection of late potentials (LP) on the SAE and the occurrence of VT in the chronic phase of myocardial infarction has been described by many authors. In these reports, the result that the absence of LP can predict the lower risk for VT has been emphasized. However, several factors such as time of SAE recording, infarct location, effect of reperfusion therapy, infarct size, and ventricular function may modify the SAE findings. Accordingly, further prospective study considering these factors is needed to establish the clinical value of SAE after myocardial infarction.

Body Surface Potential Mapping↗
PubMed1995

[Body surface potential mapping system].

Body surface potential mapping systems have been developed by several laboratories in our country as well as many other countries all over the world. In most laboratories the basic procedure is the same. Body surface potentials are measured simultaneously using a multiplexer with or without sampling bold, with Wilson's central terminal and stored on a floppy disk in a digital form. Editing for waveform and drift of the baseline was performed in each leads and invalid leads were interpolated from surrounding leads values. Then, different types of maps such as isopotential map, isointegral map, isochronal map and departure map suitable for each clinical evaluation are constructed automatically. However, although body surface mapping provides detailed information about cardiac electrical activity, its clinical use has been limited by the following reasons summarized by B. Taccardi in 1985. 1) Lack of standardization: Different electrode replacement prevents comparing the results. 2) The equipment is comparably expensive. 3) Application of electrode is time-consuming. 4) Analysis of data is not standardized. Further clinical studies may improve some of above described difficulties. And the availability of high performance microcomputers and clinically acceptable electrodes are essential.

Body Surface Potential Mapping↗
PubMed1995

[Dipole analysis of data base for body surface potential maps of normal population].

The dipolarity of the body surface potential distribution and locus of the main dipole were estimated by means of the least square method in data base for body surface potential maps of normal population. The main dipole moved smoothly within the actual cardiac region and was inscribed in a clockwise direction during the QRS. The nondipolar content (residue) showed time-dependent fluctuation the QRS. The main dipole during the T wave moved near the center of the heart. The nondipolar content during the ST-T period was less fluctuation than that during the QRS. These results indicated that a large percentage of the body surface potential maps of normal population could be represented by a single moving dipole.

Aging↗
PubMed1993

[Electrocardiogram in heart failure].

Heart failure is basically a manifestation of mechanical disturbances of the heart, but not of electrical abnormalities and is not associated with specific ECG patterns. Several ECG findings are, however, experienced in cases with heart failure as a result of cardiac chamber enlargement and other related changes. Left atrial enlargement is known to cause characteristic P wave changes, which sometimes show parallel course with the clinical state. ECG criteria for atrial enlargement are critically reviewed. In cases with cardiac enlargement, which was improved in a relatively short period of time, R wave height often showed first increase and then decrease. Tissue edema was thought to be the major reason for the initial increase and the distance between the recording electrode and the heart for the later decrease, although other factors can contribute and modify the findings. Minor conduction disturbances due to myocardial stretch and other reasons may also contribute to changes of QRS complex. Analysis of RR intervals offers another possibility to characterise heart failure. A decrease in variability of the RR intervals and in high frequency components on frequency spectrum has been reported in cases with heart failure.

Electrocardiography↗
PubMed1992

A case of right atrial mobile thrombus complicating multiple pulmonary emboli.

Right atrial thrombi are usually immobile. However, a mobile type mimicking a cardiac tumor, especially myxoma, has been described on rare occasions. We report here a case of atrial thrombus which was mobile in the cardiac chambers. A 29-year-old male was admitted because of exertional dyspnea. On admission, his echocardiogram showed an abnormal mass in the right atrium with a stalk attached to the interatrial septum. It decreased in size on the next day. On the fourth day of admission, it moved to the right ventricle. Multiple pulmonary emboli were revealed by the lung perfusion scintigram. Two days after the administration of intravenous urokinase, the abnormal mass in the cardiac chambers was no longer seen on the echocardiogram. This was a rare case of mobile atrial thrombus associated with multiple pulmonary emboli. Thrombolytic therapy appeared to be effective in this case.

Adult↗
PubMed1991

Study on the genesis of giant negative T wave in apical hypertrophic cardiomyopathy using a three-dimensional computer model.

Apical hypertrophic cardiomyopathy is characterized by a spade-like left ventricular cavity and by both giant negative T waves and tall R waves in the electrocardiogram. However, the mechanisms of these ECG abnormalities have not been satisfactorily clarified. We have recently developed a three-dimensional computer model of ventricular depolarization and repolarization processes. This model has successfully simulated normal QRST waves and changes characterizing some abnormal conditions. A model of apical hypertrophic cardiomyopathy was constructed by adding model units to the endocardium of the left ventricular apex. The surface ECG was then calculated by assuming different gradients of action potential durations and different proportions of the hypertrophic cells in the apical segment. A negative T wave of -1.45 mV in lead V4, similar to the clinically reported ECG, was obtained by assuming: (1) diffusely distributed hypertrophic cells at the apex and (2) uniform, long action potential durations of hypertrophic cells. It is suggested that these properties may account for the distinctive ECG abnormalities in apical hypertrophic cardiomyopathy.

Cardiomyopathy, Hypertrophic↗
PubMed1990

Computer simulation of supraventricular tachycardia with the Wolff-Parkinson-White syndrome using three-dimensional heart models.

Supraventricular tachycardias with the Wolff-Parkinson-White (WPW) syndrome have been successfully simulated using a newly developed simulation system. The heart model, including atria and ventricles, was constructed of about 50,000 discrete elements (model cells) in three dimensions with 1.5-mm spatial resolution. The model cells covered all of the types of cells in the actual heart, including the normal myocardium, special conduction system and abnormal cells, such as the bundle of Kent (accessory pathway) and ectopic pacemaker (premature beat). Different model cells were specified by their electrophysiologic parameters, such as action potential, refractory period, and conduction velocity. The WPW syndrome was simulated by setting an accessory pathway between the right atrium and ventricle. Based on this model a premature atrial beat was introduced, which initialized the tachycardia. By adjusting the parameters, three types of reciprocal supraventricular tachycardia were simulated with the reentry circuits (1) formed anterogradely by the A-V node and retrogradely by the accessory pathway, (2) formed anterogradely by the accessory pathway and retrogradely by the A-V node, and (3) confined within the A-V node. Time relations for initializing and maintaining the tachycardias were evaluated. The simulated ECGs were in good agreement with the clinical findings.

Computer Simulation↗
PubMed1990

Determination of the site of the accessory pathway in WPW syndrome by an electrocardiographic inverse solution.

The initial portion of the QRS complex in WPW syndrome might be represented by a single dipole, since the delta wave corresponds to the localized ventricular activation propagated over the accessory atrioventricular pathway. In order to examine whether the site of the accessory pathway in WPW syndrome could be localized by an equivalent dipole method, the dipole positions during the delta wave were determined in 30 patients using a three dimensional model of the torso and were then compared with the sites of accessory pathways localized by body surface maps. The single dipole approximation during the delta wave appeared to be appropriate since the index of the nondipolarity of the potentials was as low as 28% on average. The dipole positions determined on the atrioventricular ring during the delta wave were compatible with the sites of accessory pathways localized by body surface maps in 22 of the 30 patients. The dipole positions were adjacent to the sites of accessory pathways in 7 of the remaining 8 patients. Thus the equivalent dipole method might be an additional noninvasive tool to determine the site of the accessory pathway in WPW syndrome.

Adult↗
PubMed1989

Identification of susceptibility to ventricular tachycardia after myocardial infarction by nondipolarity of QRST area maps.

The QRST area map has been related to susceptibility to ventricular tachyarrhythmias because it reflects the disparity of ventricular recovery properties. However, the clinical value of the nondipolarity of the QRST area map, a marker of nonuniform ventricular repolarization, has not been fully studied in myocardial infarction. The nondipolarity of the QRST area map (residue), the ratio of minimized deviation by an optimal dipole to the total measured potentials, was quantitatively studied in relation to susceptibility to ventricular tachycardia after myocardial infarction. The residue of the QRST area map was higher in 59 patients with myocardial infarction than in 44 normal subjects (25.0 +/- 9.0 versus 17.8 +/- 3.3%, p less than 0.01). Seventeen patients with ventricular tachycardia in the chronic phase (greater than 10 days) of myocardial infarction showed higher residue in their QRST area map (34.5 +/- 10.3%) than that in 29 patients without ventricular tachycardia throughout the study (22.7 +/- 6.7%) or that in 13 patients with ventricular tachycardia only in the acute phase (21.2 +/- 7.5%). QRST area maps with a residue greater than or equal to 25% (mean + 2 SD of normal subjects) identified patients with ventricular tachycardia in the chronic phase of myocardial infarction with a sensitivity of 82% and a specificity of 71%. These results suggest that quantitative assessment of the nondipolarity of the QRST area map is clinically useful for identifying susceptibility to ventricular tachycardia in the chronic phase of myocardial infarction.

Adult↗
PubMed1989

Clinical application of electrocardiographic computer model.

A three-dimensional computer model was developed to stimulate the ventricular depolarization and repolarization in a clinical setting. The ventricle is composed of approximately 50,000 units arranged in a cubic close-packed structure and the specialized conduction system is distributed so as to obtain the excitation sequence resembling normal ventricular depolarization. The normal distribution of action potential waveforms with the longest duration on the endocardium and the shortest on the epicardium is used in the model. The heart model is mounted in a homogeneous torso model, and the body surface potential distribution generated by the electric dipoles is calculated using the boundary element method. The QRST waveforms corresponding to the normal and some abnormal heart conditions, such as bundle branch block, myocardial infarction, apical hypertrophic cardiomyopathy, and Wolff-Parkinson-White syndrome, is obtained by assuming the abnormal area with altered electrical properties. Thus the three-dimensional computer model may provide further insight into the genesis of the clinical electrocardiogram.

Bundle-Branch Block↗
PubMed1987

Application of dipole analysis for the diagnosis of myocardial infarction in the presence of left bundle branch block.

The residue value on dipole analysis (the ratio of non-dipolar component to the measured body surface potentials) was estimated mathematically in 16 patients with left bundle branch block. Patients were classified into those with (group A, nine patients) and those without (group B, seven patients) a perfusion defect on thallium-201 myocardial scintigraphy. For the entire QRS complex the residue of group B was smaller than that of normal subjects (20.0 +/- 4.1% versus 24.6 +/- 3.5%, p less than 0.05). Group A showed a greater mean residue value than group B (27.4 +/- 4.4% versus 20.3 +/- 2.4%, p less than 0.01) only during the initial one-third of the QRS complex. All but one patient of group A and only one patient in group B showed a high peak on the residue curve during the initial stage of the QRS complex. The maximal residue value of group A during the initial QRS complex was significantly greater than that of group B (40.9 +/- 10.9% versus 23.4 +/- 5.4%, p less than 0.01). An arbitrarily selected criterion of the maximal residue value greater than or equal to 30% during the initial QRS complex showed a sensitivity of 89% with a specificity of 86% for the diagnosis of myocardial infarction in the presence of left bundle branch block. These results might be related to the complex ventricular activation around the infarcted area even in the presence of left bundle branch block in which intramyocardial conduction with a simple activation front predominates. Dipole analysis appeared to be a valuable method of diagnosing myocardial infarction in the presence of left bundle branch block.

Bundle-Branch Block↗
PubMed1985

Dipolarity and dipole location during QRS and T waves in normal men estimated from body surface potential distribution.

The dipolarity of the body surface potential distribution and the locus of the main dipole were estimated mathematically at 2 msec intervals in 27 normal men. The nondipolar content showed time-dependent fluctuation during the QRS. It increased sharply at early and later phases of the QRS. The main dipole moved smoothly within the actual cardiac region and was inscribed in a clockwise direction in most cases. The nondipolar content during the ST-T period was smaller and with less fluctuation than that during the QRS. The main dipole during the T wave moved less than 2 cm near the center of the heart. These results indicated that although a fairly large percentage of the body surface potential could be represented by a single moving dipole, the nondipolar content was larger during initial and late phases of the QRS. It was also suggested that the ventricular repolarization process can be better approximated by a single fixed dipole in normal men.

Adult↗