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Biomedical subjects

W Shimizu

Publications and source records attributed to W Shimizu.

At least 91 records · Page 5Linked to original sources
PubMed1995

Dynamic relationship between the Q-aT interval and heart rate in patients with long QT syndrome during 24-hour Holter ECG monitoring.

The purpose of this study was to investigate the dynamic relationship between heart rate and the Q-aT interval (the interval from the Q wave to the T wave apex) in patients with long QT syndrome. The QT to heart rate relation is useful for evaluating abnormalities of the ventricular repolarization, but its clinical application to the long QT syndrome requires accurate computer aided measurement of the QT interval and the sampling of a large number of beats. Therefore, the Q-aT interval was used on the basis of some reports that the heart rate dependency of the QT interval was concentrated in the Q-aT interval. Recent advances in the computer technology have allowed analysis of the relationship between the Q-aT and RR intervals on Holter ECG recordings. However, in addition to a prolonged QT interval, most patients with long QT syndrome have bizarre and variable T waves and the influence of this T wave morphology on the Q-aT to heart rate relation has not been clarified. We investigated the dynamic relationship between the Q-aT interval and heart rate in 10 patients with long QT syndrome and 11 control subjects using our original computer algorithm for the analysis of 24-hour Holter ECG recordings. The patients showed morphological T wave changes associated with heart rate changes during Holter recordings and these affected the Q-aT interval. The patients showed the following characteristics in the relationship between the major T wave peak and the RR interval: (1) a modestly decreased correlation between Q-aT and RR than in the control subjects (a median r value of 0.87 vs 0.93; P = 0.001); and (2) a steeper Q-aT/RR slope than in controls (a median slope of 0.24 vs 0.16; P < 0.05). Abnormal and variable T wave morphology in the long QT patients was closely related to a modestly decreased correlation between Q-aT and RR than in the control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Abnormal response to exercise, face immersion, and isoproterenol in children with the long QT syndrome.

The present study was performed to observe the change of QT interval by sympathetic stimulations in patients with the long Qt syndrome (LQTS). The study group consisted of 6 children with LQTS and 6 healthy children without QT prolongation. All LQTS patients had syncopal episodes. The QTc and delta QTc% ([QTc interval after examination-QTc interval at rest]/ QTc interval at rest x 100) by treadmill testing, face immersion, and isoproterenol were examined. One minute after peak exercise of treadmill testing, the changes in the QTc interval were not significant in either group, but delta QTc% was larger in the LQTS group than in the control group (+ 11.0 +/- 12.1% vs -2.6 +/- 3.2%; P = 0.02). The QTc interval at the shortest RR interval during face immersion was prolonged in the LQTS group (0.47 +/- 0.01 s to 0.51 +/- 0.04 s; P = 0.02), but there were no significant changes in the control group (0.40 +/- 0.03 s to 0.41 +/- 0.03 s; P = NS). delta QTc% was larger in the LQTS group than in the control group (+ 10.0 +/- 7.3% vs +1.1 +/- 5.5%; P = 0.04). In the LQTS group, the RR interval was shortened (P = 0.009) and QTc interval was prolonged (P = 0.0008) after isoproterenol infusion. These sympathetic stimulations amplified the TU abnormality in the LQTS group. By observing the TU changes caused by face immersion, we hoped to find a possible new method with which to diagnose LQTS. The combination of these examinations may be helpful in screening the borderline cases of TU abnormalities.

Adolescent↗
PubMed1995

[Concept of activation recovery interval and clinical usefulness of body surface recovery time and recovery time isochrone map].

Several experimental studies have suggested that activation recovery interval (ARI), i.e., the interval between the minimum dV/dt of the QRS and the maximum dV/dt in the ST-T segment on unipolar electrograms, is correlated closely with the transmembrane action potential duration. The ARI can be measured from numerous electrograms recorded simultaneously to provide spatial distribution data on local ventricular recovery. On the other hand, recovery time (RT), i.e., the interval between QRS onset and the time of maximum dV/dt in the ST-T segment, is used to estimate dispersion of ventricular repolarization. In this review article, clinical usefulness of RT and RT ischrone map measured by body surface mapping is outlined in normal subjects and some clinical settings.

Body Surface Potential Mapping↗
PubMed1995

Radiotherapy for laryngeal cancer in patients under 50 years old.

Fifty-nine cases of laryngeal cancer treated by radiotherapy at the National Cancer Center Hospital between 1962 and 1990 were analyzed retrospectively. All the patients were less than 50 years old. The median total dose of the radiation delivered to the primary tumor site was 70 Gy. The overall 5-yr survival rate and 5-yr local control rate were 88% and 72%, respectively. Five (8.5%) of the 59 patients developed late recurrence more than five yr after initial treatment, but subsequent salvage operations were successful for disease control; three patients had T1 glottic cancer, one had T2-3 glottic cancer and one had T3N1 supraglottic cancer. Since the local control rate and the 5-yr survival rate after radiotherapy are satisfactory, radiotherapy, which allows both functional and esthetic conservation, has an important role in the treatment of laryngeal cancer in adults under 50 yr of age.

Adult↗
PubMed1995

Concurrent chemotherapy and radiation therapy for locally advanced carcinoma of the esophagus.

A pilot study was undertaken to clarify the efficacy of concurrent chemoradiotherapy against locally advanced esophageal carcinoma. The 20 patients in this study had previously untreated esophageal carcinoma with evidence of T4 disease and/or distant node metastases. Chemotherapy consisted of protracted infusion of 5-fluorouracil at a dose of 400 mg/m2/day on days 1-5 and 8-12, combined with a 2-h infusion of cisplatinum at 40 mg/m2 on days 1 and 8. Radiation treatment for the mediastinum was administered 5 days per week for 3 wk at 2 Gy/day, along with chemotherapy. These schedules were repeated twice to give a total radiation dose of 60 Gy. For patients who responded, two additional courses of chemotherapy were administered. Five of the 20 patients had UICC stage III disease and 15 had stage IV. Seventeen (85%) of the 20 patients exhibited an objective response, including 6 (30%) complete responses. Local control was excellent with 10 (50%) complete responses. Toxic effects were severe. Major toxicities were leukocytopenia of grade 3 or more in 45% of the patients and esophagitis, including four perforations. There were two treatment-related deaths. The median survival time was 9 mo (range: 2 to 34+). Concurrent chemotherapy and radiotherapy was effective even for locally advanced esophageal carcinoma, but was associated with significant toxicity.

Aged↗
PubMed1994

Diagnostic value of recovery time measured by body surface mapping in patients with congenital long QT syndrome.

The QT interval of the resting 12-lead electrocardiogram is normal or borderline in some patients with congenital long QT syndrome (LQTS). Recently, several in vivo experimental studies have shown that the time of maximum dV/dt in the ST-T segment is correlated with the time of local ventricular recovery. The purpose of this study was to examine the value of the body surface recovery time measured by 87-lead body surface mapping for detecting LQTS. Body surface mapping and 12-lead electrocardiography were performed simultaneously in 18 patients with LQTS and 40 controls of similar age and sex. The recovery time (RT), that is, the interval between QRS onset and the time of maximum dV/dt in the ST-T segment, was measured automatically by computer from each of the 87 mapping leads, and the corrected RT (RTc) was calculated by Bazett's method. The QT interval was measured from each of the 12 standard electrocardiographic leads, and the corrected QT (QTc) interval was also calculated. The maximum RT and RTc, the minimum RT and RTc, and the RT and RTc dispersions (difference between maximum and minimum RT and RTc in each patient) were significantly longer in the LQTS group than in the control group. In addition, a maximum RT of 390 msec, a maximum RTc of 430 msec 1/2, an RT dispersion of 170 msec, and an RTc dispersion of 170 msec1/2 separated the 2 groups completely (i.e., no overlap). The maximum QT and QTc, the minimum QT and QTc, and the QT and QTc dispersions (difference between maximum and minimum QT and QTc in each patient) were also significantly longer in the LQTS group than in the control group. However, the maximum QTc was normal (< or = 440 msec1/2) or borderline (< or = 460 msec1/2) in 5 of the 18 LQTS patients, and none of these parameters clearly separated the 2 groups. These results suggest that measurement of RT by 87-lead body surface mapping is useful for diagnosing latent or borderline LQTS.

Adolescent↗
PubMed1994

Epinephrine-induced ventricular premature complexes due to early afterdepolarizations and effects of verapamil and propranolol in a patient with congenital long QT syndrome.

We report a patient with congenital long QT syndrome in whom early afterdepolarizations (EADs) were demonstrated on monophasic action potential (MAP) recordings in the left ventricular mid-base inferior wall. Epinephrine infusion at 5 micrograms/min increased the amplitude of the EADs and the late component of the T(U) wave. Epinephrine also induced ventricular premature complexes (VPCs) with right bundle branch block morphology and left-axis deviation that occurred from the peak of the EADs. Verapamil injection (5 mg) during continuous epinephrine infusion abolished all VPCs with a slight reduction in the amplitude of the EADs. Propranolol injection (5 mg) in addition to verapamil further reduced the amplitude of the EADs and the late component of the T(U) wave. These findings suggest that the epinephrine-induced VPCs were closely related to triggered rhythm arising from the EADs, and that both verapamil and propranolol were effective for the suppression of VPCs and EADs.

Action Potentials↗
PubMed1994

Differential effect of pharmacological autonomic blockade on some electrophysiological properties of the human ventricle and atrium.

OBJECTIVE: This study investigated the dominance of each limb of the autonomic nervous system and tested sympathetic-vagal interactions in the human ventricle and atrium after administration of propranolol and atropine. PATIENTS AND METHODS: The 90% monophasic action potential duration (MAPD90) and the effective refractory period (ERP) at the right ventricular apex (RV) and the right lateral atrium (RA) were measured in 14 patients. The MAPD90 was measured during constant RV and RA pacing (cycle length 600 ms) and the ERP was measured at a driven cycle length of 600 ms. Electrophysiological variables were measured during a control period, after propranolol (0.15 mg/kg loading dose followed by 0.1 mg/min infusion), and after autonomic blockade (atropine 0.04 mg/kg). RESULTS: Both RV MAPD90 and RV ERP increased after propranolol (RV MAPD90 from 268 (26) ms to 275 (26) ms, p < 0.005; RV ERP from 252 (25) ms to 258 (26) ms, p < 0.0005) and then decreased to below the control values after autonomic blockade (RV MAPD90 256 (24) ms; RV ERP 239 (25) ms, p < 0.0005 v propranolol, p < 0.0005 v control). In contrast, both RA MAPD90 and RA ERP increased after propranolol (RA MAPD90 from 242 (19) ms to 260 (19) ms; RA ERP from 216 (21) ms to 230 (18) ms, p < 0.0005), and then increased slightly more after autonomic blockade (RA MAPD90 265 (16) ms, p = 0.09; RA ERP 235 (16) ms, p = 0.07), thus remaining above control values (p < 0.0005). CONCLUSIONS: The results indicate (a) that in the human ventricle vagal stimulation and sympathetic beta stimulation are antagonistic and that direct vagal stimulation predominates over beta stimulation, with sympathetic-vagal interaction being minimal and (b) that in the human atrium vagal stimulation and beta stimulation are synergistic and beta stimulation predominates over vagal stimulation, with direct vagal stimulation having a minimal effect.

Action Potentials↗
PubMed1993

Early afterdepolarization in a patient with complete atrioventricular block and torsades de pointes.

We present a patient with complete atrioventricular block and torsades de pointes in whom early afterdepolarization (EAD) was demonstrated in right ventricular monophasic action potentials (MAPs). In an emergency situation, MAPs were recorded after the suppression of torsades de pointes by magnesium injection. EADs were observed at three out of five right ventricular sites during escape rhythm. Thus, magnesium abolished the tachycardia without shortening the QT interval and probably without suppressing EAD. Right ventricular pacing and the injection of lidocaine (50 mg) suppressed EAD and shortened the QT interval.

Action Potentials↗
PubMed1993

Long-term results of catheter ablation for idiopathic ventricular tachycardia originated from the right ventricular outflow.

We performed catheter ablation in 10 consecutive patients with idiopathic monomorphic right ventricular tachycardia and studied the long-term outcome. All ventricular tachycardias had a left bundle branch block configuration with an inferior axis, and originated from right ventricular outflow. Antiarrhythmic drugs (3-6 drugs) had been ineffective in controlling ventricular tachycardia. The 2 patients who underwent direct-current ablation (2 shocks of 150 J) had no recurrence of ventricular tachycardia and did not require antiarrhythmic drugs during a follow-up of 56 and 51 months, respectively. Of the 8 patients who underwent radiofrequency ablation (30-40 watt, 20-40 sec, 2-15 application, using Inter Nova RA 50, 13.56 MHz), 1 patient had no recurrence of ventricular tachycardias and did not require antiarrhythmic drugs, 4 patients had no recurrence of ventricular tachycardias but did require anti-arrhythmic drugs, and 3 patients experienced recurrence of non-sustained ventricular tachycardia despite the use of antiarrhythmic drugs during a follow-up of 15-40 months. There were no complications except for cardiac perforation which occurred immediately after direct-current ablation in 1 patient. In conclusion, long-term success in preventing ventricular tachycardia was achievable with direct-current ablation, but this success was associated with serious risks, such as cardiac perforation. Radiofrequency ablation was safer than direct-current ablation, but had a lower long-term success rate.

Adult↗
PubMed1993

Small cell carcinoma of the esophagus with an esophago-mediastinal fistula successfully treated by chemoradiation therapy and intubation: a case report.

A case of esophageal small cell carcinoma with cervical node metastases and an esophago-mediastinal fistula was treated successfully by chemoradiotherapy. The fistula, after irradiation, was handled successfully by esophageal intubation, followed by infusional 5-fluorouracil and cisplatinum chemotherapy, resulting in the closure of the fistula. Two courses of concurrent chemoradiotherapy, followed by additional cisplatinum and etoposide chemotherapy, were administered. The tumor, including the cervical lymph node metastases, disappeared completely after the treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

[The effects of pharmacological autonomic blockade on the conduction system in patients with and without sinus node dysfunction].

Electrophysiological studies were performed in 26 patients with sick sinus syndrome (SSS) and 12 controls before and after pharmacologic autonomic blockade (PAB) with propranolol (0.15 mg/kg) and atropine (0.04 mg/kg). Sinus cycle length (SCL) shortened significantly after PAB in both groups. PA and HV intervals did not change after PAB. AH interval shortened and Wenckebach period increased after PAB in SSS group. Maximum corrected sinus node recovery time shortened in the control group but did not change in the SSS group after PAB. Calculated sinoatrial conduction time shortened after PAB in both groups. Refractory periods of the atrioventricular (AV) node and the ventricle shortened significantly, but those of the atrium did not change after PAB. Linear relations existed between the change of SCL and the change of AH interval and of the Wenckebach period. These results suggested that the autonomic nervous system had the same effects on the sinus and the AV nodes in patients with SSS, and that parasympathetic tone was predominant on the sinus node, the perinodal tissue and the AV node under resting conditions.

Atropine↗
PubMed1992

Induction of TU abnormalities in patients with torsades de pointes.

1. TU abnormalities could be induced by the specific interventions in the majority of the patients with TDP in chronic stage: isoproterenol in congenital long QT patients, disopyramide in Ia-related TDP patients, and slow heart rate in bradycardia-related TDP patients. 2. Humps in MAP could be recorded in all patients with congenital long QT syndrome by isoproterenol, in half of the patients with Ia-related TDP by disopyramide, but in none of the control patients by these agents. 3. The results suggested that TU abnormalities and the occurrence of hump in MAP were hypersensitive reactions. 4. The results also suggested that specific intervention was not enough for the appearance of marked TU abnormalities in some TDP patients, especially in Ia-related TDP patients. Additional aggravating factors were probably required for marked TU abnormalities and the occurrence of TDP in these patients.

Action Potentials↗
PubMed1992

Effects of a combination of disopyramide and mexiletine on the anterograde accessory pathway conduction in patients with Wolff-Parkinson-White syndrome.

In order to evaluate the electrophysiological effects of the combined administration of disopyramide and mexiletine on anterograde accessory pathway conduction, we studied 11 patients with Wolff-Parkinson-White (WPW) syndrome. Disopyramide was first infused intravenously at 1 mg kg-1 for 5 min followed by a continuous infusion at 0.025 mg kg-1 min-1. After the infusion rate of disopyramide was decreased to 0.004 mg kg-1 min-1 to maintain a lower serum concentration, mexiletine was infused at 2 mg kg-1 for 5 min followed by a continuous infusion at 0.008 mg kg-1 min-1 (protocol 1). The shortest atrial paced cycle length with 1:1 anterograde accessory pathway conduction (shortest CL with 1:1) and the anterograde effective refractory period of the accessory pathway (ERP) were measured: (1) before drug administration, (2) after disopyramide was given alone, and (3) after disopyramide and mexiletine were combined at lower concentrations. The same protocol was repeated with the order of drug administration reversed (mexiletine followed by disopyramide) in all patients (protocol 2). Both disopyramide and mexiletine lengthened the shortest CL with 1:1 and the ERP to the same degree. The combination of disopyramide and mexiletine at lower concentrations further lengthened the shortest CL with 1:1. It was longer than with disopyramide (protocol 1) or mexiletine (protocol 2) alone [protocol 1: 412 +/- 169 ms (combination) vs 356 +/- 117 ms (disopyramide); P less than 0.05, protocol 2: 409 +/- 166 ms (combination) vs 355 +/- 119 ms (mexiletine); P less than 0.01].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Significance of ventricular pacing site in manifest entrainment during orthodromic atrioventricular reentrant tachycardia with left-sided accessory pathway.

We examined entrainment by ventricular pacing in six patients during orthodromic atrioventricular reentrant tachycardia (AVRT) utilizing a left-sided lateral accessory pathway. Constant fusion and progressive fusion were demonstrated in all patients by left ventricular pacing during tachycardia, but in none of the patients by right ventricular pacing. When left ventricular pacing was performed during AVRT, the antidromic wave front from the pacing impulse (n) collided with the orthodromic wave front of the previous pacing beat (n - 1) within the ventricle, therefore, constant fusion and progressive fusion were demonstrated in the surface electrocardiographic QRS complexes. On the other hand, when right ventricular pacing was performed during orthodromic AVRT, the antidromic wave front from the pacing impulse (n) collided with the orthodromic wave front of the previous paced beat (n - 1) within the normal atrioventricular pathway, and constant fusion and progressive fusion were therefore not demonstrated. These phenomena were explained by the relationship of the ventricular pacing site and the reentrant circuit. This study demonstrates the importance of the pacing site in manifest entrainment of orthodromic AVRT during ventricular pacing.

Adult↗