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Biomedical subjects

W Shimizu

Publications and source records attributed to W Shimizu.

100 records · Page 6Linked to original sources
PubMed1991

Differential response of QTU interval to exercise, isoproterenol, and atrial pacing in patients with congenital long QT syndrome.

Sympathetic stimulation is well known to contribute to the genesis of QTU prolongation and ventricular tachyarrhythmias in patients with congenital long QT syndrome. In this study, we performed exercise treadmill testing, isoproterenol infusion (1-2 micrograms/min), and right atrial pacing (cycle length 500 msec) in 11 patients with congenital long QT (LQT) syndrome (LQT group) and in 12 age- and sex-matched controls (control group). The responses of the corrected QT (QTc; Bazett's method) interval and the TU wave complex were evaluated. The QTc interval was prolonged from 482 +/- 63 msec1/2 to 548 +/- 28 msec1/2 by exercise in the LQT group (n = 11; P less than 0.005), and this was associated with fusion of the T waves with enlarged U waves, whereas the QTc interval did not increase with exercise in the control group (n = 12; 402 +/- 19 msec1/2 vs 409 +/- 22 msec1/2). The QTc interval was also prolonged from 466 +/- 50 msec1/2 to 556 +/- 33 msec1/2 by isoproterenol in the LQT group (n = 7; P less than 0.005) in association with morphological changes of the TU wave complex like those seen with exercise, whereas it was only slightly increased from 399 +/- 10 msec1/2 to 436 +/- 13 msec1/2 by isoproterenol in the control group (n = 77; P less than 0.001). However, the QTc interval did not increase with atrial pacing in the LQT group (n = 8; 476 +/- 57 msec1/2 vs 486 +/- 59 msec1/2), whereas it was slightly increased from 400 +/- 21 msec1/2 to 426 +/- 18 msec1/2 by atrial pacing in the control group (n = 8; P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Bradycardia-dependent early afterdepolarizations in a patient with QTU prolongation and torsade de pointes in association with marked bradycardia and hypokalemia.

Endocardial monophasic action potentials (MAPs) were recorded at the right ventricular apex in a patient with QTU prolongation and torsade de pointes (TdP) in association with marked bradycardia and hypokalemia. There was a distinct hump on phase 3 repolarization of the MAPs characteristic of early afterdepolarizations (EADs), which was associated with marked prolongation of the QTU interval on the surface electrocardiogram. EAD amplitude was bradycardia dependent, and there was a strong correlation (r = 0.91) between the preceding RR interval and the amplitude of the EAD (percent of MAP amplitude). Intravenous administration of lidocaine or right ventricular pacing suppressed the ventricular premature complexes and TdP in association with the suppression of the EADs on the MAPs. Furthermore, these EADs were not recorded on the MAPs 1 month later when the QTU prolongation and TdP had disappeared. These findings suggest that the TU abnormality and QTU prolongation responsible for TdP were due to bradycardia-dependent EADs.

Action Potentials↗
PubMed1991

Early afterdepolarizations induced by isoproterenol in patients with congenital long QT syndrome.

BACKGROUND: Several recent experimental and clinical studies have shown that early afterdepolarizations (EADs) are important in the genesis of QTU prolongation and ventricular tachyarrhythmias (VTs) in patients with long QT syndrome. On the other hand, sympathetic stimulation is well known to contribute to the genesis of QTU prolongation and VTs in patients with congenital long QT syndrome. The present study was performed to examine the influence of isoproterenol on the genesis of EADs and on the action potential durations and QTU intervals in patients with congenital long QT syndrome. METHODS AND RESULTS: We recorded monophasic action potentials (MAPs) with a contact electrode during right atrial pacing at a constant cycle length of 500 msec before and after continuous isoproterenol infusion (1 microgram/min). MAPs were obtained from the right and left ventricular endocardium in six patients with congenital long QT syndrome (LQT group, 18 recording sites) and in eight control patients (control group, 19 recording sites). Although no EADs were recorded from either group during the control state, MAP duration at 90% repolarization (MAPD90) was significantly longer in the LQT group (n = 18) than in the control group (n = 19) (275 +/- 36 versus 231 +/- 22 msec; p less than 0.0005). Isoproterenol induced EADs in four of the six LQT patients (five of 18 recording sites) but not in the eight control patients (zero of 19 recording sites). The appearance of EADs in the LQT group was associated with an increased amplitude of the late component of the TU complex, and the corrected QT (QTc) interval was prolonged by isoproterenol from 543 +/- 53 to 600 +/- 30 msec 1/2 (n = 6; p less than 0.05). Isoproterenol also prolonged the MAPD90 from 275 +/- 36 to 304 +/- 50 msec in the LQT group (n = 18; p less than 0.005), whereas it shortened the MAPD90 from 231 +/- 22 to 224 +/- 25 msec in the control group (n = 19; p less than 0.05). Moreover, isoproterenol increased the dispersion of MAPD90 (difference between the longest MAPD90 and the shortest MAPD90 in each patient) from 30 +/- 5 to 62 +/- 35 msec in the LQT group (n = 6; p = 0.08), whereas it did not change the dispersion of MAPD90 in the control group (n = 8; 25 +/- 14 versus 27 +/- 14 msec). CONCLUSIONS: These results suggest that patients with congenital long QT syndrome have primary repolarization abnormalities and that EADs induced by isoproterenol play an important role in the exaggeration of these repolarization abnormalities.

Action Potentials↗
PubMedDate not supplied

Intraoperative and conformal external-beam radiation therapy in patients with locally advanced pancreatic carcinoma; results from a feasibility phase II study.

BACKGROUND/AIMS: Chemoradiation therapy is widely indicated to patients with locally advanced pancreatic carcinoma, though the capability of radiotherapy alone is not assessed enough. The purpose of this study is to clarify the efficacy and safety of a more intensive radiotherapy for those patients. METHODOLOGY: Fifteen patients were enrolled in a feasible phase II study of treatment with intraoperative radiation therapy (25 Gy), followed by conformal external-beam radiation therapy (40 Gy in 20 fractions, 5 times/week). The antitumor effect was evaluated on the early phase of dynamic computed tomography image. RESULTS: The full irradiation dose was feasible in 12 of 15 patients. The overall response rate was 40% (1 complete and 5 partial responses). Grade 3 toxicity was observed in 2 patients (13%) with nausea/vomiting or anorexia. One patient developed gastric ulcer and died of gastrointestinal bleeding 12 months after intraoperative radiation therapy. The median survival time was 11.1 months, and the 2-year survival rates were 13%. Survival for more than 2 years was observed in 2 of the 6 responders. CONCLUSIONS: The above radiotherapy is considered to be active for the locally advanced pancreatic cancer with acceptable toxicity, when the gastrointestinal tract is excluded from the radiation field. This should be further assessed in late phase II studies involving a large number of patients.

Adenocarcinoma↗
PubMedDate not supplied

Utility of serum CA 19-9 monitoring in preoperative radiotherapy for pancreatic cancer.

BACKGROUND/AIMS: Pancreatic cancer is extremely refractory even to aggressive treatments including surgery, resulting in early metastasis and/or local recurrence. We investigated changes in serum tumor marker CA 19-9 levels during preoperative radiotherapy in conjunction with initial treatment failure. METHODOLOGY: Twenty-three patients presenting with localized disease and an increased serum CA 19-9 level, who were slated to undergo pancreatectomy and/or intraoperative radiotherapy following preoperative radiotherapy were reviewed. CA 19-9 response, the ratio of post-radiotherapy level before laparotomy to pre-radiotherapy level, was analyzed in relation to disease-control time and survival. RESULTS: Eleven patients revealed metastasis at restaging or laparotomy; 12 patients (52%) completed aggressive treatments. Initial failure was identified at the liver (52%), peritoneum (52%), or local site (26%) with a median disease-control time of 91 days; 7 patients showed combined failure. All but 1 patient died of cancer with a median survival time of 264 days. CA 19-9 response (range: 0-1185%) did not correlate with disease-control time or survival; 8 progressive-disease patients (> 140% response), however, showed significantly shorter disease-control time than 15 nonprogressive-disease patients (< or = 140% response). CONCLUSIONS: CA 19-9 monitoring is useful in preoperative radiotherapy for identifying patients who will not benefit by succeeding aggressive treatments by predicting early metastasis.

Adult↗
PubMedDate not supplied

Exfoliative tumor clearance following radiotherapy estimated by comparing radioresponse between primary esophageal cancer and its lymph node metastasis.

BACKGROUND/AIMS: We estimated the capacity for exfoliative mechanical clearance which could occur in shrinkage of esophageal tumors following radiotherapy; both mechanical clearance and phagocytotic biological clearance of another clearance mechanism could participate in primary diseases located on outer tissue surfaces, whereas only biological clearance can participate in lymph node metastases surrounded by normal tissues which prevent mechanical clearance. METHODOLOGY: Twenty-one patients with primary esophageal cancer and lymph node metastasis both treated by radiotherapy with the same dose were reviewed. The extent of tumor shrinkage was estimated by measuring the size on computed tomography scans before and after radiotherapy. The capacity for biological clearance plus mechanical clearance (primary disease) or biological clearance alone (lymph node metastasis) was defined as the slope of a tumor shrinkage curve. The capacity for mechanical clearance was estimated by intra-patient subtraction. RESULTS: Extent of tumor shrinkage was consistently greater in primary disease than in lymph node metastasis for each patient, showing significant correlation in extent of shrinkage between them. The capacity was smaller for mechanical clearance than for biological clearance as a whole, showing no correlation between them. CONCLUSIONS: Mechanical clearance is highly likely to participate extra in the shrinkage of tumors located on outer tissue surfaces; therefore, these tumors will normally respond more highly than parenchymal tumors.

Aged↗
PubMedDate not supplied

Adenoid cystic carcinoma of the tracheobronchial system: the role of postoperative radiotherapy.

To clarify the role of postoperative radiotherapy for adenoid cystic carcinoma of the tracheobronchial system (ACC), we analyzed patients treated at the National Cancer Center Hospital, Tokyo. Seven patients with ACC were treated with resective surgery and postoperative radiotherapy from 1962-1990. None of the primary lesions was completely surgically resected. Postoperative irradiation was delivered by standard fractionation at a dose range of 49.2-72 Gy. Four of seven patients lived more than 5 years, up to 21 years, without local recurrence. In contrast, three other patients who showed recurrence within 2 years died of disease before 5 years. Three of four patients who received postoperative irradiation of 60 Gy or more attained local control. One of three patients who received less than 60 Gy failed locally. A high dose of postoperative radiotherapy for patients with a positive surgical margin of ACC seems to improve local control and result in long-term survival.

Adult↗
PubMedDate not supplied

Cine MRI in radiotherapy treatment planning of brain tumors.

This paper presents our preliminary experience with three-dimensional (3-D) treatment planning using the cine mode display of magnetic resonance imaging (MRI) for brain tumors. MRI images, viewed from the direction of the source of radiation, are reconstructed at consecutive 5 mm intervals and superimposed on the 3-D skin surface image. Tumors and normal structures can be visualized as is, without delineating them. Limitations of the technique are also discussed.

Adult↗