Biomedical subjects

T Hiroki

Publications and source records attributed to T Hiroki.

At least 19 recordsLinked to original sources

PubMed1999

Long-term effects of LDL apheresis on carotid arterial atherosclerosis in familial hypercholesterolaemic patients.

OBJECTIVES: To assess the long-term effect of LDL apheresis on carotid arterial atherosclerosis in severe familial hypercholesterolaemic (FH) patients. DESIGN: Changes in existing plaque, new plaque formation and annual progression rate of carotid early plaque were evaluated by B-mode ultrasonography. SUBJECTS: LDL apheresis group: two homozygous FH and nine heterozygous FH patients received a combination of LDL apheresis and cholesterol-lowering drug therapy for a mean of 7.8 years. CONTROL GROUP: 10 heterozygous FH patients were maintained by medication only for a mean of 5.5 years. RESULTS: As a result of LDL apheresis treatment, LDL cholesterol levels reduced from 16.0+/-3.60 to 6.43+/-0.07 mmol L(-1) in homozygous FH patients and from 11.5+/-2.46 to 4.32+/-1.2 mmol L(-1) in heterozygous FH patients. During the long-term treatment period, the existing plaque tended to progress and new plaque formation in carotid arteries was also observed in both groups. The annual progression rate of mean maximum intima-media thickness in the common carotid artery was a mean of -0.0023+/-0.0246 mm year(-1) in heterozygous FH patients in the LDL apheresis group, suggesting regression. This was significantly lower when compared with the control group, which had a mean of 0.0251+/-0.0265 mm year(-1) CONCLUSION: The results suggest that the long-term treatment with combined LDL apheresis and drugs may delay the progression of the atherosclerotic process and prompt the stabilization of atheromatous plaque in severe FH patients.

Adult↗

PubMed1997

Structure of the rat methionine adenosyltransferase 2A gene and its promoter.

In this study, to understand the regulation of methionine adenosyltransferase (MAT) gene expression, we isolated the rat MAT2A gene encoding MAT alpha2, the catalytic subunit of non-hepatic-type enzyme MAT II and characterized its structural organization and 5'-flanking region. The gene spans approximately 7 kbp and consists of nine exons interrupted by eight introns. The transcription initiation site, as demonstrated by primer extension analysis, is located 123 bp upstream of the translation start codon. Comparison of the structural organization of the rat MAT2A gene to that of the mouse MAT1A gene encoding MAT alpha1, the subunit of liver-type enzymes MAT I and III, shows that the exon structure of two genes is very similar and the insertion sites of all corresponding introns are identical. A canonical TATA box and a GC box, the potential Sp1-binding site, are found 32 bp and 70 bp upstream of the transcription initiation site, respectively. The 5'-flanking region also contains potential recognition sites for various transcription factors including AP-1, AP-2 and NF-IL6 (C/EBPbeta), and a large G+C-rich domain with the characteristics of a CpG island. The 5'-flanking sequence of the rat MAT2A gene has no significant similarity with those of the MAT1A genes. Transient transfection experiments using a luciferase reporter gene showed that the first 820-bp sequence of the 5'-flanking region directed high levels of luciferase activity in cultured rat kidney fibroblast (NRK-49F) and hepatocellular carcinoma (FAA-HTC1) cells, but not in primary rat hepatocytes. Deletion analysis suggested that the first 343 bp of the 5'-flanking region contained cell-type-specific promoter elements of this gene.

Animals↗

PubMed1997

Effects of an angiotensin II antagonist on reperfusion arrhythmias in dogs.

Losartan, an angiotensin II receptor antagonist with no bradykinin potentiating property, provides the opportunity to study the consequences of blocking angiotensin II. The objective of this study was to evaluate the antiarrhythmic responses of reperfusion arrhythmia to losartan in dogs. The effects of losartan on ventricular tachyarrhythmias induced during occlusion and reperfusion of the left anterior descending coronary artery were investigated in 30 dogs. The animals were randomized to receive either losartan (n = 15) or saline (n = 15). The VF inducing threshold was measured before occlusion and after reperfusion. Losartan (50 micrograms/kg per min) or saline was intravenously administered 5 minutes before occlusion and continued throughout the entire study period. The incidence of ventricular tachyarrhythmias during reperfusion was lower in the losartan group than in the control group (4/15 vs 6/15). There was no significant change in VF inducing threshold between the period before occlusion and during reperfusion in the losartan group [10.9 +/- 5.7 vs 11.1 +/- 5.7 mA, P = NS), whereas there was a significant decrease in the control group (15.5 +/- 4.4 vs 7.7 +/- 3.9 mA, P < 0.01). Blockade of the angiotensin II receptor has beneficial effects on reperfusion arrhythmias.

Aldosterone↗

PubMed1995

Evaluation of abnormal signal-averaged electrocardiograms in young athletes.

Our objectives in this study were to determine the incidence of abnormal signal-averaged ECG (SAECG) and its relation to the extent and type of exercise in young healthy athletes, and to evaluate the association, if any, between the development of abnormal SAECGs and vigorous exercise. The presence of abnormal SAECG was evaluated in 796 athletes (mean age 19 years), and its relation to findings on 12-lead electrocardiogram, echocardiogram, and the presence arrhythmias was studied using Holter monitoring. An SAECG was considered abnormal when any one of the three following criteria was met: filtered QRS duration of more than 114 msec, root-mean-square voltage in the terminal 40 msec of less than 20 muV, or a voltage of less than 40 muV for more than 38 msec. Abnormal SAECGs were present in 68 (8.5%) of the athletes and were associated with a smaller left ventricular mass. Athletes who performed anaerobic exercise tended to exhibit a high incidence of abnormal SAECGs, which was associated with a smaller left ventricular mass. No serious ventricular arrhythmias were observed on 24 h Holter monitoring or during the follow-up period of 20 +/- months. There were no sudden cardiac deaths. Continuous anaerobic exercise may induce abnormal SAECGs through the development of delayed myocardial conduction or electrical inhomogeneity in cardiac tissue. Te presence of an abnormal SAECG was unrelated to the development of arrhythmias in young athletes.

Adult↗

PubMed1995

[Signal-averaged electrocardiograms in young athletes--sudden death during exercise].

Our objective was to evaluate the incidence of abnormal SAECG in young athletes, and to evaluate the relationship between abnormal SAECG and electrocardiographic and echocardiographic parameters. The presence of an abnormal SAECG was evaluated in 796 athletes (mean age 19 years), and its relation to findings on 12-lead electro-cardiograms, echocardiograms, and arrhythmias was studied, as recorded by the Holter monitor. An abnormal SAECG was defined as two of the three following criteria: filtered QRS duration > or = 114 msec, root mean squared voltage in the terminal 40 msec < or = 20 microV, or duration < 40 microV > or = 38 msec. Abnormal SAECGs were present in 68 (8.5%) of the athletes and were associated with a smaller left ventricular mass. Athletes who performed anaerobic exercise tended to exhibit a high incidence of abnormal SAECG, which was associated with smaller left ventricular mass. No serious ventricular arrhythmias were observed on Holter monitoring for 24h and during a follow-up period of 20 +/- 10 months in 796 subjects. Continuous anaerobic exercise may induce abnormal SAECG due to the development of delayed myocardial conduction or to electrical inhomogeneity in the cardiac tissue. The presence of an abnormal SAECG was unrelated to the development of arrhythmias in young athletes.

Adult↗

PubMed1994

Wavelength index: a predictor of the response to disopyramide in paroxysmal lone atrial fibrillation.

We investigated whether the new parameter wavelength index could predict the response to chronic disopyramide therapy in patients with paroxysmal atrial fibrillation (AF). Twenty-seven patients with AF underwent electrophysiologic studies and the wavelength index was determined before and after intravenous administration of disopyramide. Then all patients were treated with oral disopyramide for 6 months. In 17 patients, AF was eliminated (group A), while it persisted in another 10 patients (group B). The ratio of the wavelength index before and after intravenous disopyramide was higher in group A than in group B. Thus, the wavelength index proved useful for predicting the response of AF to disopyramide.

Adult↗

PubMed1993

Use of monophasic action potentials to evaluate postpacing T wave changes.

We examined the relationship between postpacing T wave changes and monophasic action potentials recorded from the ventricle in dogs. MAPs were recorded from the right and left ventricle before and after cessation of pacing. The duration of the MAP was calculated as the time in milliseconds from the upstroke to 90% repolarization (MAPD90). T waves in limb leads were flat or had a biphasic pattern, eventually becoming negative after pacing. The Q-T interval of the escape beat after pacing was prolonged compared with the control. After right ventricular pacing, the average duration of MAPD90 in the right ventricle, but not in the left ventricle, was prolonged. (right MAPD: control 275 +/- 10 ms; after pacing: 311 +/- 17 ms, p < 0.05; left MAPD: control: 266 +/- 23 ms, after pacing: 284 +/- 26 ms, NS). After left ventricular pacing, the average duration of MAPD90 in the left ventricle, but not in the right ventricle, was prolonged (right MAPD: control: 247 +/- 75 ms, after pacing: 287 +/- 39 ms, NS; left MAPD: control: 257 +/- 23 ms, after pacing: 303 +/- 25 ms, p < 0.05). Furthermore, the average duration of MAPD90 at the pacing site became progressively prolonged over time. These results suggest that myocardial cells retain the memory of abnormal repolarization associated with pacing.

Action Potentials↗

PubMed1993

Pathological extent of interventricular septal infarction in patients with acute anteroseptal myocardial infarction with and without right bundle branch block.

The purpose of the present study is to elucidate the difference in extent of myocardial infarction (MI) between those cases with and those without right bundle branch block (RBBB) occurring during the course of acute MI. We examined postmortem hearts from 20 patients with acute anteroseptal MI; 10 with (group A) and 10 without RBBB (group B). The extent of MI was studied pathologically in the interventricular septum (IVS) and reconstructed. The longitudinal extent of MI did not distinctly differ between groups A and B. In 5 hearts of group B, the anterior limit of the MI extended as high, or as close to the cardiac base, as in group A hearts. Transmural MI was relatively common and seen more frequently in group A than in group B. However, the MI did not always extend evenly to the left and right ventricular sides in the IVS. Left-sided predominance in extent of the MI was more frequently observed in group B than in group A. Right-sided predominance in the extent of septal MI was relatively rare and was seen in 5 cases at the portion where the right bundle branch came down. Four of these were group A patients. Thus, involvement of the right bundle branch might partly depend on the unevenness of the mural extent of the MI as well as the height of extension of the MI in the IVS.

Aged↗

PubMed1993

[Early diagnosis and management of acute pulmonary embolism: clinical evaluation those of 225 cases].

To contribute for making early diagnosis and treatment of acute pulmonary embolism (APE), we investigated on clinical pictures of 225 patients with APE. Common underlying factors were heart disease, prolonged bed rest, post-surgical state, thrombophlebitis, malignant tumor and post-catheterization state in this order. Dyspnea, chest pain, tachycardia and shock were frequently seen as initial symptoms and signs. Blood screening showed leukocytosis, hypoxemia, hypocapnia and elevated serum LDH. Electrocardiographic findings highly demonstrated were ST.T abnormalities, such as T inversion with ST elevation in V1-3, ST depression in V4-6 and sinus tachycardia. Chest X-rays showed diminished pulmonary vascular marking and pulmonary artery dilation. Right ventricular dilatation were frequently seen on 2-dimensional echocardiograms. Pulmonary artery pressure were elevated up to 49/20 (30) mmHg. Twenty-five percent of the patients died, and the recurrence was seen in 4%. Thus, as soon as APE is suspected by above clinical findings, definitive diagnosis should be obtained by the lung perfusion scan and pulmonary arteriography, then oxygen and thrombolytic agents should be given immediately to prevent the fatal outcome.

Acute Disease↗

PubMed1992

A fast Fourier transform analysis of coronary reperfusion-induced ventricular fibrillation and the modification by dibutyryl cyclic AMP in a cat model.

To investigate the effect of dibutyryl cyclic AMP (dbcAMP) on ventricular fibrillation after coronary reperfusion, the proximal portion of the anterior descending branch of left coronary artery was reperfused 20 min after ligation in 24 cats. McFee X Y Z electrocardiograms were recorded and ventricular fibrillation was analyzed using a fast Fourier transform analysis (FFT). Ventricular fibrillation occurred in 20 of 24 cases. Sixty seconds after the occurrence of ventricular fibrillation, an intracardiac infusion of dbcAMP was administered. Nine of the 20 were defibrillated and converted to sinus rhythm or junctional rhythm after the administration of dbcAMP. The amplitude and frequency of the main power spectrum of the ventricular fibrillation waves were analyzed by FFT before and after the infusion of saline or dbcAMP. In the saline group there was no significant change in FFT. However, in the dbcAMP group, the amplitude increased significantly from 0.036 +/- 0.015 (MV--2) to 0.054 +/- 0.013 (MV--2) (p < 0.01) and the frequency decreased significantly from 4.22 +/- 1.37 (Hz) to 1.33 +/- 0.91 (Hz) (p < 0.01). Those results indicate that dbcAMP increased the amplitude and decreased the frequency of the main power spectrum of ventricular fibrillation analyzed by FFT. These distinctive changes in FFT analysis were associated with defibrillation in 9 of 20 cases.

Animals↗

PubMed1992

Transesophageal low-energy synchronous cardioversion of atrial flutter/fibrillation in the dog.

The purpose of this study was to determine the feasibility and efficacy of terminating atrial flutter/fibrillation using low-energy synchronous shocks delivered through a transesophageal catheter in dogs with talc-induced pericarditis. Atrial flutter/fibrillation was induced by employing the pulse train method. The minimum effective cardioversion energy level was compared for three different methods--method A, delivery between a distal esophageal electrode and a proximal esophageal electrode; method B, delivery of shocks through a distal esophageal electrode and a plate placed on the chest; method C, transthoracic cardioversion. The minimum effective cardioversion energy level did not differ significantly between methods A and B (1.30 +/- 0.46 joules versus 1.29 +/- 0.35 joules). Transesophageal cardioversion decreased the defibrillation threshold three- to fourfold from that of conventional transthoracic cardioversion. There were no complications of heart block, ventricular fibrillation, or any pathologic evidence of esophageal injury. Thus transesophageal low-energy synchronous cardioversion is considered a feasible and effective method for the treatment of atrial flutter/fibrillation.

Animals↗

PubMed1992

Lymphocytic active myocarditis characterized by numerous clusters of lymphocytes: a chronic variant of myocarditis?

We report three patients with a particular form of myocarditis characterized by numerous clusters of lymphocytes. Their common clinical manifestation was progressive and fatal heart failure with a 3- to 6-year duration. Atrioventricular and intraventricular conduction disturbances were observed in two patients. At necropsy, the hearts weighed 480, 530, and 430 gm, respectively, and showed marked dilatation of the bilateral ventricles and atria, with frequent mural thrombi. Histologic examination revealed numerous lymphocytic clusters and scattered foci of acute myocardial cell damage on a background of extensive fibrosis. We propose the term "chronic active myocarditis" to denote clinicopathologic characteristics of the present cases.

Atrial Fibrillation↗

PubMed1991

Alcohol intake and nonfatal acute myocardial infarction in Japan.

The relation between alcohol and nonfatal acute myocardial infarction (AMI) was examined in a case-control study of 89 male patients and 271 control subjects in Fukuoka, Japan. Patients admitted for the first AMI at 2 hospitals in Fukuoka City were aged 40 to 69 years, and control subjects were recruited based on the telephone directory of the city. Information on alcohol drinking and potential coronary risk factors was obtained by using a self-administered questionnaire, and past drinkers were separated from lifelong abstainers in the analysis. After adjustment for age, occupation, cigarette smoking, strenuous exercise, body mass index, hypertension, diabetes mellitus and parental heart disease, the risk of AMI was progressively less with increasing levels of alcohol consumption. With those who never drank as a referent, adjusted odds ratios for current drinkers consuming less than 30, 30 to 59, and greater than or equal to 60 ml/day of alcohol were 1.11 (95% confidence interval 0.51 to 2.42), 0.31 (0.11 to 0.83), and 0.13 (0.05 to 0.36), respectively. These findings add to the body of data showing that alcohol drinkers are less likely to have AMI.

Adult↗

PubMed1991

Effects of dibutyryl cyclic AMP on ventricular vulnerability during atrioventricular block in dog.

The effects of dibutyryl cyclic AMP (DBcAMP) on ventricular vulnerability during complete atrioventricular block (CAVB) were studied one week after transarterial electrical ablation of the AV junction in 18 closed-chest dogs. All dogs exhibited CAVB and a stable ventricular escape rhythm with a mean cycle length of 1812 +/- 638 ms. After the administration of DBcAMP at a rate of 0.1 mg/kg/min for 30 min, the ventricular cycle length was significantly shortened, and the QTc interval was slightly prolonged, although the QT interval did not change. The ventricular fibrillation threshold after the administration of DBcAMP was significantly increased (from 12.2 +/- 3 84 to 18.4 +/- 5.08 mA, p less than 0.01). Thus, it was demonstrated that DBcAMP exhibited suppressive effects on the ventricular vulnerability in the experimentally induced CAVB.

Animals↗

PubMed1991

Normalization of reverse redistribution of thallium-201 with procainamide pretreatment in Wolff-Parkinson-White syndrome.

Stress thallium-201 myocardial perfusion imaging was performed in a patient with Wolff-Parkinson-White syndrome. Reverse redistribution phenomenon was observed in the absence of coronary artery disease. This seems to be the first report of normalization of this phenomenon in association with reversion of accessory pathway to normal atrioventricular conduction after pretreatment with procainamide.

Adult↗

PubMed1991

Antiarrhythmic and proarrhythmic properties of diazepam demonstrated by electrophysiological study in humans.

We evaluated the electrophysiological parameters before and after the intravenous infusion of diazepam (0.2 mg/kg) in 20 cardiac patients to investigate the drug's antiarrhythmic effect. Diazepam did not significantly change the arterial pressure. After the intravenous infusion of diazepam, the sinus cycle length significantly shortened from 847 +/- 132 to 747 +/- 155 ms (p less than 0.01). No significant change in the maximal sinus node recovery time was noted. The AH interval at the atrial pacing length of 600 ms shortened significantly from 140 +/- 40 to 127 +/- 39 ms (p less than 0.05). However, there was no significant change after the administration of diazepam in the longest atrial pacing rate associated with Wenckebach conduction in the atrioventricular (AV) node, effective and functional refractory periods of the AV node, HV interval, and QRS width during ventricular pacing at the cycle length of 600 ms. The atrial and ventricular effective refractory periods remained unchanged after the administration of diazepam. Six of the eight patients who showed dual AV nodal refractory period curves in the control study did not demonstrate them after diazepam administration by increasing the atrial or AV node effective refractory period. Thus, diazepam showed significant electrophysiological effects of the heart including shortening of the sinus cycle length, improvement in AV node conduction, and no significant effect on the His-Purkinje or intraventricular conduction and refractoriness of the atrium, AV node and ventricle. On the other hand, diazepam may influence the inducibility of supraventricular reentrant tachycardia incorporating the AV node.

Adult↗

PubMed1991

Effects of atrioventricular block on ventricular fibrillation threshold in dog.

The effects of complete atrioventricular block (CAVB) on ventricular vulnerability were studied 1 week after a transcatheter electrical ablation of the AV junction in 18 closed-chest dogs. All dogs exhibited CAVB and a stable ventricular escape rhythm with a mean cycle length of 1795 +/- 600 ms. Although QT interval during CAVB was significantly prolonged compared with that during the sinus rhythm, QTc interval was significantly shortened. The ventricular fibrillation threshold was significantly elevated after creation of the block (from 9.35 +/- 2.28 to 12.3 +/- 3.69 mA, p less than 0.01). Thus, CAVB which is not associated with QTc prolongation would be even less likely to play an important role in producing ventricular fibrillation presumably including torsades de pointes or polymorphous ventricular tachycardia.

Animals↗

PubMed1991

Effects of transcatheter cardioversion on chronic lone atrial fibrillation.

The effectiveness and safety of internal transcatheter cardioversion on chronic lone atrial fibrillation were examined in ten patients resistant to external electrical (400 joules) and pharmacological cardioversion. Transcatheter cardioversion was performed by pulling back the atrioventricular junction catheter just inferior to the site of the His-bundle recording and delivering the shock between a proximal electrode (cathode) and backplate (anode). Transcatheter cardioversion restored sinus rhythm in all of the ten patients. The only complication observed was transient atrioventricular block after the shock and this was treated by temporary pacing. However, atrial fibrillation recurred in five patients at 30, 27, 52, 1, and 6 days, respectively. A second attempt at transcatheter cardioversion was performed in those patients an was successful in three patients. During a follow-up period ranging from 12 to 22 months, eight patients continued in sinus rhythm. Thus, transcatheter cardioversion is considered effective and safe in selected patients with chronic lone atrial fibrillation in whom external cardioversion was unsuccessful.

Atrial Fibrillation↗