Biomedical subjects

T Hiroki

Publications and source records attributed to T Hiroki.

At least 19 recordsLinked to original sources

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↗

PubMed1991

A quantitative histopathological study of right bundle branch block complicating acute anteroseptal myocardial infarction.

The aim of the present study was to evaluate whether necrosis of the right bundle branch is responsible for development of right bundle branch block in acute myocardial infarction. Twenty patients with acute anteroseptal myocardial infarction were studied--10 with right bundle branch block (group A) and 10 without (group B)--to evaluate by serial sectioning the pathological extent of myocardial infarction surrounding the right bundle branch and also that of right bundle branch necrosis. Myocardial infarction reached the right bundle branch more than 8 mm above the moderator band in all of group A, whereas myocardial infarction reached the right bundle branch less than 3 mm above the moderator band in only three patients in group B. Nine hearts in group A showed significant necrosis of the right bundle branch. In group B and in one case with transient right bundle branch block no necrosis was found. The occurrence of right bundle branch block was almost entirely explained by necrosis of the right bundle branch, but transient right bundle branch block did develop without necrosis of the right bundle branch.

Aged↗

PubMed1991

Electrophysiological properties in chronic lone atrial fibrillation.

BACKGROUND: Although the electrophysiological mechanisms underlying self-sustaining atrial fibrillation (AF) are unclear, recent studies suggest that one requirement for reentry, slow conduction, is frequently present in patients with AF. However, these observations limited to paroxysmal AF may not necessarily apply to chronic AF. Therefore, electrophysiological properties of the atrium and sinus nodal function in chronic lone AF were evaluated. METHODS AND RESULTS: Electrophysiological studies were performed after electrocardioversion in 12 patients with chronic lone AF. Atrial enlargement was absent in the patients with AF. Twelve patients without atrial arrhythmias served as the control group. The patients with AF had a higher incidence of sinus nodal dysfunction, a shorter atrial effective refractory period (215 +/- 19 msec versus 238 +/- 23 msec, p less than 0.02), and a longer P wave duration than control patients (115 +/- 16 msec versus 86 +/- 16 msec, p less than 0.01). The conduction delay zone was significantly greater in patients with AF (60 +/- 12 msec) than that in the control patients (8 +/- 13 msec, p less than 0.01), and the maximal conduction delay was also greater in the study patients than those in the control group, both to the His bundle region (31 +/- 12 msec versus 10 +/- 15 msec, p less than 0.01) and to the coronary sinus (41 +/- 15 msec versus 15 +/- 11 msec, p less than 0.01). The fragmented atrial activity zone was wider in the study group (23 +/- 25 msec) than in control subjects (1.7 +/- 4 msec, p less than 0.02). Repetitive atrial firing was observed in four patients with AF but it was not seen in the control group. CONCLUSIONS: These electrophysiological features, which are manifestations of the abnormal atrial electrophysiology, would favor production of atrial reentry in chronic lone AF.

Atrial Fibrillation↗

PubMed1990

Automatic junctional tachycardia in an adult.

We report an adult patient with junctional ectopic tachycardia, a condition which was initially described in infants, frequently in association with congenital defects. The patient had a rapid, irregular paroxysmal junctional tachycardia with a rate ranging from 160 to 220 beats/min, distinguishing it from the more common nonparoxysmal junctional tachycardia in which a slower heart rate is seen. The electrophysiological study performed during an episode of tachycardia demonstrated periods of atrioventricular dissociation and narrow QRS complexes as well as a junctional ectopic rhythm, which was suggested by a His deflection preceding each ventricular depolarization with a normal HV interval. Both the response to exercise and the results of atrial and ventricular stimulation suggested enhanced automaticity of a high junctional focus. Therapy combining procainamide, verapamil, and digitalis proved to be effective. Thus, junctional ectopic tachycardia can also occur in adults, probably due to enhancement of automaticity.

Adult↗

PubMed1990

Low energy synchronous transcatheter cardioversion of atrial flutter/fibrillation in the dog.

The feasibility and effectiveness of low energy synchronous transcatheter cardioversion of atrial flutter and fibrillation were examined in dogs with talc-induced pericarditis. A conventional electrode catheter was positioned transvenously in the right atrial appendage. Atrial flutter/fibrillation was induced by using the train pulse method, and the tachyarrhythmia-inducing threshold was determined. The minimal effective cardioversion energy levels were compared in three different cardioversion methods: method A = delivery of shock between the proximal electrode (cathode) and the backplate (anode), method B = delivery between the proximal electrode (cathode) and the distal electrode (anode) and method C = conventional external cardioversion. In both methods A and B, all 149 cardioversion attempts were successful with shocks of less than or equal to 5 J. Shocks of less than or equal to 1 J resulted in successful cardioversion in 57 (70%) of 81 attempts, 50 (74%) of 68 attempts and 5 (12%) of 41 attempts with methods A, B and C, respectively. The mean minimal effective cardioversion energy levels were not significantly different between methods A and B (0.62 +/- 0.67 versus 0.58 +/- 0.71 J). Transcatheter cardioversion decreased the defibrillation threshold 3- to 75-fold (mean 6- to 7-fold) from that of transthoracic cardioversion. The defibrillation threshold was not influenced by the inducibility of atrial flutter/fibrillation. There were no complications of heart block, ventricular fibrillation or pathologic evidence of severe shock-induced atrial injury. Thus, low energy synchronous transcatheter cardioversion of atrial flutter/fibrillation is considered feasible and effective. This technique may also be useful in managing the atrial flutter/fibrillation that can occur during electrophysiologic studies.

Animals↗

PubMed1990

Right bundle branch block. Echocardiographic study with special reference to the site of block within the right bundle.

One hundred and fifty-seven patients with complete right bundle branch block (CRBBB) were studied with echocardiography (UCG). In 87 of them, both ECG and UCG of good quality were obtained and analyzed to differentiate the site of the block within the right bundle. Their mean age was 53.2 +/- 17.6 (SD) years, and they consisted of 62 males (50.2 +/- 16.8 years) and 25 females (60.8 +/- 17.3 years), suggesting that males were more susceptible to CRBBB than females, with a male to female ratio of 2.48 among our study group. In a normal control group, the time interval from the initial deflection of the QRS complex of the ECG to mitral valve closure (QMC) was 52.3 +/- 11.6 msec, to tricuspid valve closure (QTC) 87.7 +/- 11.5 msec, to the point of full opening of the pulmonary valve (QPO) 124.5 +/- 13.7 msec, from mitral to tricuspid valve closure (MCTC) 35.5 +/- 11.2 msec, and from tricuspid valve closure to the maximum opening of the pulmonary valve (TCPO) 38.0 +/- 13.8 msec, and in patients with CRBBB, QMC 58.7 +/- 13.2 msec, QTC 95.4 +/- 24.2 msec, QPO 169.1 +/- 24.6 msec, MCTC 36.7 +/- 18.2 msec, and TCPO 73.7 +/- 23.7 msec. Although prolonged QMC and QTC are characteristic features in CRBBB as a whole, CRBBB was divided into 4 groups in this study depending on the difference in MCTC and TCPO: Proximal block with prolonged MCTC, peripheral block with prolonged TCPO, diffuse block with both MCTC and TCPO prolonged, and non-specific block without prolongation of either of the two. The incidences were 11.5% (10 patients) for proximal block, 64.4% (56 patients) for peripheral block, 16.1% (14 patients) for diffuse block, and 8.0% (7 patients) for non-specific block. Thus, conduction disturbance in the peripheral portion of the right bundle branch was observed in 80.5% of our cases, suggesting that peripheral block is much more common than proximal block in adults.

Adult↗

PubMed1990

[A case of myxedema with diffuse myocardial fibrosis proven by endomyocardial biopsy].

We report a middle-aged woman with myxedema heart who presented both clinical features resembling dilated cardiomyopathy and the diffuse myocardial fibrosis proven by endomyocardial biopsy. Thirty years previously, when she was 36 years old, partial thyroidectomy had been performed after a diagnosis of hyperthyroidism was made. Four years later, she experienced dry skin and peripheral edema, and hypothyroidism was diagnosed. Several months after, replacement therapy for hypothyroidism improved her symptoms. However, the therapy was discontinued because of her ignorance of the disease. Twenty six years later (64 years old), she felt exertional dyspnea, and was admitted to Fukuoka University Hospital for evaluation of her cardiac state. Thyroid function test revealed primary hypothyroidism with low T3, low T4 and high TSH levels. Cardiothoracic ratio on chest X-ray film was 69%. Electrocardiogram showed low voltage in the limb leads and intraventricular conduction disturbance. Echocardiogram demonstrated marked dilatation and severely reduced wall motion of the left ventricle and pericardial effusion. Left ventriculogram showed diffuse hypokinesis with 27% of the ejection fraction. No significant stenosis was observed on coronary arteriogram. Seventeen-month replacement therapy did not improve these cardiac findings significantly. Transvenous right ventricular endomyocardial biopsy demonstrated diffuse myocardial fibrosis without inflammatory infiltrate, which was interpreted as a sequel of interstitial lesions of the myxedema heart such as edema or mucoid infiltration. This pathological finding suggests that long-standing untreated hypothyroidism can cause irreversible myocardial damage.

Aged↗

PubMed1990

[A rare adult case of double-outlet right ventricle without pulmonary stenosis: an autopsy case].

Double outlet right ventricle (DORV) is a rare cardiac malformation especially in adulthood. We report a woman with DORV who survived to the age of 33 years. She had not been seriously limited, before she visited our hospital for cardiac evaluation at the age of 25 years. She was cyanotic, and had clubbing of fingers and toes and facial edema. Holosystolic murmur and diastolic regurgitant murmur were audible along the left sternal border. Chest X-ray showed cardiomegaly and enlarged pulmonary trunks. Electrocardiography showed right axis deviation and biventricular hypertrophy. Laboratory examination revealed polycythemia (Hb: 22.4 g/dl), increased levels of hepatic enzymes due to congestive liver and marked hypoxemia (Pao2: 40 mmHg), Diagnosis of DORV was made with cardioangiography. Surgical repair was not indicated. Thereafter, she experienced recurrent heart failure which progressed gradually. She died probably of ventricular arrhythmia at the age of 33 years. At autopsy, the heart showed dilatation of the right atrium and ventricle, and hypertrophy of the bilateral ventricles. Both the pulmonary artery without stenosis and the aorta originated completely from the right ventricle, which were almost normally positioned with bilateral conus. Large ventricule septal defect was found at the subaortic portion. Patent ductus arteriosus and preductal aortic coarctation co-existed. To our knowledge, few cases with DORV who survived over 30 years have been reported, and they all manifested pulmonary stenosis. The present case is a very rare DORV that survived over 30 years without the complication of pulmonary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Plasma fibrinogen levels as an independent indicator of severity of coronary atherosclerosis.

The relationship between plasma fibrinogen levels and the severity of coronary atherosclerosis was examined in 229 patients, aged 25-82 years (162 men and 67 women), undergoing coronary angiography. Severity of coronary atherosclerosis was assessed in terms of the number of vessels with a 75% or greater stenosis and Gensini's severity score. Fibrinogen levels increased progressively with the severity of coronary atherosclerosis, determined by both the number of involved vessels and Gensini's severity score in men, and the relationships were statistically significant. Similar patterns were noted among women, but the trends were not statistically significant. The association was evident even after adjustment for age, hypertension, total cholesterol, cigarette smoking, alcohol intake, high density lipoprotein cholesterol and body mass index. These results provide evidence that in the Japanese also plasma fibrinogen levels can serve as an independent indicator of the progression of coronary atherosclerosis.

Adult↗

PubMed1989

A case of cross stimulation.

Cross stimulation in a dual chamber pacing system, in which the atrial stimulus intermittently captured the right ventricle, occurred immediately after pacemaker implantation in a 71-year-old man. It was prevented temporarily by reducing the pacing rate so that P wave synchronous ventricular (VDD) pacing resulted and by reducing the output of the atrial circuit from 5 to 4 volts. Cross stimulation disappeared spontaneously 14 days after surgery.

Aged↗