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Biomedical subjects

T Nirei

Publications and source records attributed to T Nirei.

18 recordsLinked to original sources
PubMed2001

Recovery time dispersion measured by body surface mapping: noninvasive method of assessing vulnerability to ventricular tachyarrhythmias.

To assess the significance of recovery time (RT) dispersion measured by body surface mapping, we investigated body surface RT isochrone maps of 40 patients with anterior old myocardial infarction (OMI), 40 patients with dilated cardiomyopathy (DCM), and 40 controls. Among the OMI and DCM groups, 20 patients per group had sustained ventricular tachycardia (VT). The dispersion of corrected recovery time (RTc) by Bazett's formula significantly increased in OMI patients (169 +/- 38 ms) and DCM patients (163 +/- 22 ms) compared with controls (147 +/- 10 ms) (P <.01). RTc dispersion was greater in OMI patients with sustained VT than in those without sustained VT [184 +/- 43 ms vs. 155 +/- 24 ms (P <.05)], as well as in DCM patients with sustained VT compared with those without sustained VT [170 +/- 25 ms vs. 156 +/- 17 ms (P <.05)]. The results suggest that RTc dispersion determined by body surface mapping can be useful for assessing vulnerability to sustained VT.

Adult↗
PubMed2000

[A successful case of hybrid therapy for the left main trunk and triple coronary vessel lesions with acute myocardial infarction and cardiogenic shock].

A 86-year-patient who had acute myocardial infarction and critical cardiogenic shock was diagnosed to have the left main trunk (LMT) and triple vessel disease. Emergent coronary artery bypass grafting to the left anterior descending artery was performed using saphenous vein graft without cardiopulmonary bypass through median sternotomy. On the 41st postoperative day, catheter intervention was performed to the remaining lesions by stenting of LMT and percutaneous transluminal coronary angioplasty to the right coronary artery lesions. Tl scintigraphy showed remarkable reduction of myocardial ischemia. Hybrid therapy is the effective new strategy for critical cases which cannot be successfully and securely treated by medical or surgical approach alone.

Aged↗
PubMed1998

Possible mechanism of ECG features in patients with idiopathic ventricular fibrillation studied by heart model and computer simulation.

The possible contribution of localized conduction delay and abnormal action potentials to ventricular fibrillation (VF) was studied by applying an anisotropic cardiac computer model to clinical cases of the Brugada-type electrocardiogram (ECG), which shows right bundle branch block (RBBB), a normal QT interval, ST-segment elevation, and late r' in leads V1 and V2. The anisotropic heart model was composed of 50,000 discrete units with a spatial resolution of 1.5 mm and was mounted in a human torso model. The longitudinal/transverse conduction velocity ratio was 3:1. For the normal ECG, a conduction velocity of 0.75 m/s was required. In the abnormal area of the right anterior epicardial wall, the conduction velocity was set at 0.2 m/s, with decreasing action potential amplitude and 10% prolonged action potential duration. The ECG features of ST-segment elevation and Brugada-type right bundle branch block pattern were simulated. The action potential duration was able to change dynamically with coupling interval of stimulation, with a ratio of 9% for normal ventricular muscle and 50% for Purkinje fibers. Five successive stimuli were applied to the left lateral epicardium 300 ms after the first sinus excitation, and sustained VF was induced with the transmural conduction delay at the right anterior ventricle as a block increasing the vulnerability. At the initiation of VF, reentry circuits were shown around the border zone of the right epicardium and were very heterogeneous around the conduction delayed area and septal area. In an area with the characteristics of nontransmural conduction delay, sustained VF was prevented, and the pattern of transient right bundle branch block appeared on the simulated ECG and body surface potential maps. The late r' wave was calculated in the precordial leads and right anterior site on the body surface potential maps. These results suggest that increased multipolarity in the border zone between the Purkinje fibers and delayed conduction area in the right ventricle might play an important role as a functional block for the persistence of VF.

Action Potentials↗
PubMed1997

Idiopathic ventricular fibrillation induced with vagal activity in patients without obvious heart disease.

BACKGROUND: Recently, idiopathic ventricular fibrillation (VF) has gained much attention. Although several subgroups have been described, its pathogenesis, mechanism, treatment, and prognosis remain unknown. METHODS AND RESULTS: We studied six cases of idiopathic VF with transient late r' waves and ST elevation (late r'/ST elevation) in leads V1 through V3. Late r'/ST elevation was augmented before and after VF episodes. Signal-averaged ECGs showed late potentials even when no late r'/ST elevation occurred. During late r', a conduction delay was observed by use of body-surface maps at the anterior wall and outflow tract of the right ventricle without inhomogeneity of the repolarization phase. There was a decrease or total disappearance of late r'/ST elevation with isoproterenol, atropine, and exercise stress testing and induction or exacerbation with propranolol, edrophonium, and hyperventilation. VF was induced by programmed electrical stimulation in all cases but two, in which it was induced only after edrophonium injection. In two cases, VF was exacerbated by propranolol, and in all cases, it was uninducible with isoproterenol. Heart rate spectral analysis just before VF episodes showed a sudden rise in vagal activity in two cases. As the VF mechanism, a conduction delay exists at the anterior wall and outflow tract of the right ventricle that is possibly exacerbated by an abrupt rise in vagal activity, inducing random reentry that results in VF. Class I antiarrhythmic agents and beta-blockers were ineffective for this VF. All subjects required implantable cardioverter-defibrillators. CONCLUSIONS: We propose this VF associated with late r'/ST elevation in the precordial leads and influenced by vagal activity as a new possible mechanism of idiopathic VF.

Adult↗
PubMed1997

Cardiac memory in patients with intermittent Wolff-Parkinson-White syndrome.

This study used body surface mapping to evaluate the ventricular repolarization process in the absence of delta waves in 13 patients with the intermittent Wolff-Parkinson-White (WPW) syndrome. The findings were compared with data from 30 normal individuals and 50 patients with the overt WPW syndrome. The QRST isointegral maps of patients with the overt WPW syndrome exhibited abnormal areas and the QRST departure maps showed a peculiar distribution to each accessory pathway site. The QRST isointegral map exhibited abnormal areas in 11 of the 13 cases (85%) of the intermittent WPW syndrome in the absence of delta waves. In 8 of these 11 cases (73%), the distribution of the departure map resembled that in the overt WPW syndrome. These findings suggest that abnormal ventricular repolarization due to cardiac memory is present in patients with the intermittent WPW syndrome even in the absence of delta waves.

Adolescent↗
PubMed1995

[Localization of accessory pathway in Wolff-Parkinson-White syndrome using body surface mapping].

Predicting the site of accessory pathway in Wolff-Parkinson-White syndrome using body surface mapping is an established examination. For this purpose, many methods have been reported, such as, isopotential maps of QRS wave and ST-T wave, subtraction map of QRS isopotential map, isointegral maps of QRS and QRST waves, and departure map of QRST isointegral map, moving dipole and single value decomposition. The method of determining by the location of the minimum in early QRS isopotential map is most widely used. It should be noted, however, that the prediction is often difficult in posteroseptal accessory pathway and the cases with relatively narrow QRS wave.

Body Surface Potential Mapping↗
PubMed1995

[Classification of the site of the conduction disturbance in right bundle branch block using body surface mapping].

We can estimate the conduction disturbance in right bundle branch block (RBBB) using body surface mapping. Characteristics of body surface mapping in the cases with RBBB are classified into three types using the appearance time and the site of the breakthrough. In the first type, breakthrough appeared in the center of the anterior chest within the normal time. It shows the peripheral block of right bundle branch. In the second type, breakthrough appeared in the center of the anterior chest later than the normal time. It shows the conduction delay of the main trunk of right bundle branch. In the third type, breakthrough appeared at the left of the anterior chest later than the normal time. It suggests the complete block of the main trunk of right bundle branch.

Body Surface Potential Mapping↗
PubMed1995

[Variation of body surface QRST isointegral map in patients with idiopathic long QT syndrome].

Body surface QRST isointegral maps in patients with long QT syndrome (LQTS) often show multipolar distribution. We recorded body surface maps in eight cases with LQTS. There were same day variations in the distribution of multipolarity and unipolarity in two of seven cases, and day-to-day variation in one of seven cases. In two of four cases, the distribution of the map changed from unipolarity to multipolarity following hand-pushing exercise. When two patients with same day variation or day-to-day variation were administered beta-adrenergic blocking agents, their QRST isointegral maps all showed unipolar distribution and had no variations. These findings suggest that QRST isointegral map can be a useful method for predicting the effectiveness of beta-adrenergic blocking drugs in idiopathic long QT syndrome.

Adolescent↗
PubMed1995

[Characteristics of body surface mapping in the cases of idiopathic ventricular fibrillation].

Body surface mapping was recorded in three patients with idiopathic ventricular fibrillation (VF). A late r' wave appeared and disappeared in the precordial leads in all three patients. In one case, the late r' wave appeared with epithides of VF. In the presence of the late r' wave, the QRS duration was extremely prolonged. However, the appearance time of the breakthrough in the QRS isopotential map was not significantly prolonged. The time of the peaks of the r' wave was elongated in the mid anterior chest. These findings suggest that peripheral conduction disturbances in the right ventricle are related to the occurrence of VF in patients with idiopathic VF.

Adult↗
PubMed1992

Evaluation of proarrhythmic effect of antiarrhythmic drugs on ventricular tachycardia associated with congestive heart failure.

The usefulness and limitations of antiarrhythmic drugs in ventricular tachycardias (VT) associated with congestive heart failure remain uncertain. The purpose of this study is to evaluate the proarrhythmic effects of antiarrhythmic drugs in patients with refractory VT associated with left ventricular dysfunction using electrophysiologic study (EPS). Twenty-four patients with left ventricular dysfunction, defined by left ventricular ejection fraction (LVEF) lower than 40% using left ventriculography, were studied. The average LVEF was 29.5%. As for underlying heart disease, 14 had old myocardial infarction, 8 cases had dilated cardiomyopathy and 2 had aortic regurgitation. As a control to this group, 23 cases with underlying heart disease and LVEF higher than 40%, and 27 cases with no obvious heart disease were studied. We considered a drug to have proarrhythmic effects if 1) it decreased by one the number of stimuli needed to induce VT, 2) induced non-sustained VT in the control study which changed to induced sustained VT, 3) the sustained VT or ventricular fibrillation was newly induced, or 4) the induced sustained VT which was stopped by pacing in the control study changed to induced VT which could not be terminated by pacing and required DC shock. Proarrhythmic effects were recognized in 17 of 24 cases with left ventricular dysfunction. Of the 67 drug trials, proarrythmic effects were seen in 26. Proarrhythmias were observed in 9 of 23 cases (39.1%) with organic heart disease associated with LVEF higher than 40%. In 12 of 69 drug trials (17.4%) proarrhythmias were observed. Of 27 cases with no obvious heart disease 10 cases (37%) had proarrhythmias. In 14 of 130 drug trials (10.8%), proarrhythmias were recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗