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Biomedical subjects

K Kuga

Publications and source records attributed to K Kuga.

At least 19 recordsLinked to original sources
PubMed2003

Noninvasive, direct visualization of macro-reentrant circuits by using magnetocardiograms: initiation and persistence of atrial flutter.

AIMS: We analysed the cardiac magnetic fields on the body surface to visualize electrical currents noninvasively during reentrant arrhythmias. METHODS AND RESULTS: Seven patients with counterclockwise atrial flutter (AFL) were studied during 17 episodes of AFL using 64-channel magnetocardiograms (MCGs) and electrophysiological study. Eight of the episodes were paroxysmal AFL, in which MCGs were recorded from the time of spontaneous onset to the time of termination. We constructed iso-magnetic field maps of the tangential components and produced MCG animations. With respect to AFL initiation, an atrial premature complex induced AFL. Prior to the initiation of AFL, atrial fibrillation (AF) transiently occurred. The cardiac magnetic fields revealed a single peak during sinus rhythm or with premature complexes but a disorganized pattern during AF. When AF transformed to AFL, the magnetic fields changed from a disorganized pattern to a single peak at first and then evolved to a circular pattern. During persistent AFL, the magnetic source moved in a counterclockwise circuit. CONCLUSION: MCG animation can be used to visualize the sequence in which a premature complex transforms sinus rhythm to AFL via AF. Our findings indicate that MCGs can be used to identify noninvasively the mechanisms responsible for atrial tachyarrhythmias.

Atrial Fibrillation↗
PubMed2001

Torsade de pointes induced by intravenous and long-term oral amiodarone therapy in a patient with dilated cardiomyopathy.

A 70-year-old woman with dilated cardiomyopathy and ventricular tachyarrhythmia was initially treated in 1990 with intravenous amiodarone (240 mg). She developed a junctional escape rhythm (48 beats/min) with QT prolongation (QT: 0.68 s) and 8 h later developed torsade de pointes (TdP). Because other antiarrhythmic drugs did not suppress the arrhythmia, oral amiodarone (100 mg/day) was started in 1995, 7 weeks before she presented with congestive heart failure. The QT prolongation (QTc: 0.64) increased after administration of dopamine, and TdP again developed. This case suggests that amiodarone induces proarrhythmias by different mechanisms when administered intravenously or orally.

Administration, Oral↗
PubMed1999

Improvement of oral ingestion in patients with inoperable esophageal cancer treated with radiotherapy, chemotherapy and insertion of a self-expanding nitinol stent.

Radiotherapy, chemotherapy and self-expanding nitinol stent insertion were performed in patients with inoperable esophageal cancer to improve oral ingestion. Twelve patients underwent radiotherapy and chemotherapy. A stent was inserted in patients with dysphagia after radiotherapy and chemotherapy. Patients' capacity for oral ingestion was classified into three categories: grade I patients were able to ingest enough food; grade II patients could ingest food but required nutritional support; and grade II patients found it impossible to ingest anything. After radiotherapy and chemotherapy, the number of grade I patients increased from three to five but seven patients remained in grades II and III. Four grade II and III patients were treated with stents, after which dysphagia was reduced to grade I. In the grade I patients after treatment with radiotherapy and chemotherapy, the duration of grade I was on average 167 days and survival was 191 days. In the patients subjected to stent insertion, grade I lasted 65 days and survival was 149 days. Before the introduction of the stent, grade II patients died, on average, after 91 days. After the introduction of self-expanding nitinol stents, all patients could ingest enough food and were discharged.

Aged↗
PubMed1999

Effect of intravenous amiodarone on electrophysiologic variables and on the modes of termination of atrioventricular reciprocating tachycardia in Wolff-Parkinson-White syndrome.

Atrioventricular reciprocating tachycardia (AVRT) associated with the Wolff-Parkinson-White (WPW) syndrome, sometimes terminates spontaneously, generally sustains and eventually becomes drug resistant. Amiodarone is a potent antiarrhythmic drug that is sometimes effective in patients with AVRT which is resistant to conventional antiarrhythmic drugs. However, systematic studies concerning the effects of amiodarone on AVRT have not been reported. This study evaluated the effects of intravenous amiodarone on electrophysiologic variables, and on the sites and the modes of termination of AVRT. Fifteen WPW patients were studied. Nine had overt, and 6 had concealed WPW syndrome. Measurements of electrophysiologic variables and the induction of AVRT were performed by atrial and/or ventricular programmed stimulations. Amiodarone was then administered at a dose of 5 mg/kg over 5 min. The effective refractory periods (ERP) of the atrial, atrioventricular node, ventricular and accessory pathway were increased significantly by amiodarone. The conduction times of all the components were significantly lengthened by amiodarone, except for the His-ventricular (HV) interval in concealed WPW patients. AVRT was induced in all patients, and was terminated by amiodarone in 12 of 13 patients with sustained AVRT. After amiodarone, AVRT was induced in 9 patients. Spontaneous termination was observed 11 times in 3 of the 9 patients in whom AVRT was still induced. In these cases, the modes and sites of termination were the same as during the baseline state. The ERPs and conduction times of all components of AVRT, except the HV interval, were significantly lengthened by amiodarone. Amiodarone is efficacious for terminating AVRT wherever weak links exist. However, sites of spontaneous termination are not significantly affected by amiodarone.

Adolescent↗
PubMed1996

CCK-4-induced calcium mobilization in T cells is enhanced in panic disorder.

We investigated the effects of brain cholecystokinin (CCK) receptors on the intracellular calcium concentration and protein kinase C in human T cells. CCK-4 produced a transient increase in calcium in the absence of extracellular calcium. CCK-B agonists stimulated calcium mobilization in a dose-dependent manner in T cells. CCK-B antagonists suppressed CCK-4-induced calcium mobilization more potently than CCK-A antagonist. The recovery of desensitization of the CCK-4-induced response was delayed by phosphoserine/phosphothreonine phosphatase inhibitor, calyculin A. The responsiveness to CCK-4 was also reduced by phorbol 12,13-dibutyrate (PDBu), and this effect of PDBu was abolished completely by preincubation with staurosporine. CCK-4-induced calcium mobilization was too small to attribute the desensitization to the protein kinase C transduction pathway. T cells from patients with untreated panic disorder exhibited significantly higher cholecystokinin-4-induced calcium mobilization than those from healthy controls or patients with treated panic disorder. These results suggest that cholecystokinin-B receptor function in T cells of patients with panic disorder is enhanced. Cholecystokinin-4-induced calcium mobilization in T cells may be state dependent and useful as a biological marker of panic disorder.

Adult↗
PubMed1996

Intraocular hemorrhage developing during interferon therapy.

A 43-year-old man with chronic active hepatitis C was treated with interferon-beta (IFN-beta) at a dosage of 6 x 10(6) IU/day for a planned 6-week period. Ocular hyperemia, ophthalmalgia, and increased intraocular pressure in the right eye developed 20 days after the start of treatment. Intraocular pressure remained high, even after discontinuation of IFN therapy, laser therapy, and iridectomy. Two days later, the right eye was removed because perforation had occurred. The ocular symptoms that developed in this case were thought to have been caused and exacerbated by IFN administration.

Adult↗
PubMed1996

[Class-I antiarrhythmic drugs].

Classification, mechanism of action, pharmacokinetic properties and clinical applications of class-I antiarrhythmic agents were summarized. Class-I drugs were subdivided into three groups, Ia, Ib, Ic. This subclassification is based on their action to modify the action potential duration. In the Cardiac Arrhythmia Suppression Trial (CAST), flecainide and encainide were associated with greater mortality than placebo in patients with non-life threatening arrhythmias. Results of CAST and other megatrials suggested that antiarrhythmic agents were unsafe in some groups of patients and the limitation of antiarrhythmic therapy. Proarrhythmia and combination therapy of antiarrhythmic agents were mentioned.

Anti-Arrhythmia Agents↗
PubMed1993

Unusual electrocardiographic findings associated with type A Wolff-Parkinson-White syndrome.

A 50-year-old woman with Wolff-Parkinson-White (WPW) syndrome presented with unusual electrocardiographic (ECG) findings following the termination of paroxysmal supraventricular tachycardia. The ECG showed three different QRS complexes and irregular R-R intervals. These QRS complexes consisted of: (1) narrow QRS; (2) wide QRS with delta wave; and (3) wide QRS with left bundle branch block (LBBB). The mechanisms of these findings, revealed by electrophysiological study, were: (1) intermittent anterograde left-sided accessory pathway conduction; (2) rate-dependent ipsilateral LBBB; and (3) intermittent retrogradely conducted atrial echoes that occurred due to intraventricular conduction delay resulting from LBBB. Cases of WPW syndrome with these unusual ECG findings, which were clearly interpreted by electrophysiological study, are rare.

Bundle-Branch Block↗
PubMed1993

Age-related changes of sinus node function and autonomic regulation in subjects without sinus node disease--assessment by pharmacologic autonomic blockade.

To assess the relationship between aging and autonomic regulation of sinus node function, 56 subjects of various ages (range 14-75 years, mean 43 +/- 19 years) without sinus node disease were studied. Heart rate, corrected sinus node recovery time and sinoatrial conduction time were measured before (basic) and after (intrinsic) pharmacologic autonomic blockade (propranolol + atropine i.v.). Percent chronotropies of the above parameters were calculated by a modified Jordan's method. Basic heart rate and basic corrected sinus node recovery time did not vary with age (r = -0.15, r = 0.08, respectively), while basic sinoatrial conduction time tended to increase with age (r = 0.32, p < 0.05). Intrinsic heart rate decreased (r = -0.76, p < 0.001), and intrinsic corrected sinus node recovery time and intrinsic sinoatrial conduction time both increased with age (r = 0.55, p < 0.001; r = 0.56, p < 0.001, respectively). The younger the subject, the more negative the percent chronotropies of the above parameters were, and the percent chronotropies correlated positively with age (r = 0.68, p < 0.001; r = 0.52, p < 0.001 and r = 0.34, p < 0.05, respectively). In conclusion, intrinsic sinus node functions deteriorated with age. Furthermore, parasympathetic tone on the sinus node functions decreased with age, which may compensate for age-related deterioration of intrinsic sinus node function.

Adolescent↗
PubMed1991

A study of ventricular contraction sequence in complete right bundle branch block by phase analysis.

Twenty-four patients with complete right bundle branch block (CRBBB) combined with and without left axis deviation (LAD) on ECG, were compared with 17 normal subjects to evaluate the right ventricular contraction sequence and pattern in detail. Blood pool scintigrams were obtained in the left anterior oblique projection, and these images were analyzed by first component Fourier harmonics. In the normal subjects, the phase value distribution representing the pattern of ventricular contraction was almost homogeneous in both the right and left ventricles (RV & LV). In the CRBBB patients without LAD, the phase images showed apparent phase delay in the right ventricle. In the CRBBB patients with LAD, the phase images showed many different contraction patterns varying from normal to RV phase delay, owing to the effects of the hemi-block. Quantitative analysis of the absolute values, showed that the mean (RV-LV) value was 6.6 +/- 8.4 msec in the normal subjects. In the CRBBB patients without LAD, the duration of the QRS complex correlated with the mean (RV-LV) value, whereas no difference was observed between the duration of the QRS complex and the standard deviation of the right ventricle. Using phase analysis the degree of the RBBB can be determined from the phase images, and can be quantitatively analyzed as in electrical studies.

Adult↗
PubMed1990

Electrophysiologic and antiarrhythmic actions of pirmenol on rabbit and guinea pig cardiac preparations.

The electrophysiological and antiarrhythmic effects of pirmenol HCl were examined using the microelectrode technique applied to multicellular preparations and the suction-pipette whole-cell clamp method applied to ventricular myocytes from rabbit and guinea pig hearts. Pirmenol at 5 microM and higher doses suppressed the sinus node automaticity by depressing the slow diastolic depolarization without changing the maximum diastolic potential. Pirmenol at 1 microM and higher doses depressed the maximum upstroke velocity (Vmax) of action potentials and prolonged the action potential duration at 90% repolarization in atrial muscles and Purkinje fibers without affecting resting membrane potentials. Pirmenol at 5 microM depressed the early part of the plateau and lengthened the final repolarization of the action potentials in ventricular myocytes, of which effects were attributed to the depression of the calcium current and the delayed outward K+ current. Triggered tachyarrhythmias arising from delayed afterdepolarizations in papillary muscles and ventricular myocytes were markedly inhibited by 1-5 microM pirmenol. The drug changed the amplitude and appearance of the transient inward current in ventricular myocytes. These results suggest that pirmenol has electrophysiologic properties that could provide an antiarrhythmic action on various types of arrhythmias.

Action Potentials↗
PubMed1989

New observations on the mechanisms of antiarrhythmic actions of disopyramide on cardiac membranes.

Electrophysiologic effects of disopyramide on cardiac membranes were studied using the microelectrode technique applied to papillary muscles and the suction pipette whole-cell clamp method applied to isolated ventricular myocytes from guinea-pig hearts. In contrast to previous reports, the development and recovery from the Vmax blocks of action potentials by disopyramide and lidocaine were best expressed by 2 exponential functions, not 1, suggesting that there might be 2 different processes for the sodium current block. A near-therapeutic concentration (11 microM) of disopyramide depressed Vmax at frequencies of 0.1 to 2.0 Hz decreased action potential amplitude and shortened plateau phase in ventricular myocytes. Action potential duration was prolonged by the drug in most of the preparations but shortened in some. Disopyramide prolonged the refractory period and increased threshold current for excitation. The drug was also shown to depress both the calcium current and the delayed outward potassium current. These multiple actions of disopyramide may explain its variety of antiarrhythmic properties.

Action Potentials↗
PubMed1989

[The heart rate alternative sequence during pharmacologic total autonomic blockade in patients with sick sinus syndrome: differential effects in relation to age].

To study the age-related changes of the sinus node function and the variations of influence of autonomic nervous system, pharmacologic total autonomic blockade (TAB) was conducted in 35 patients with symptomatic sinus bradycardia (21 men and 14 women, 50 +/- 21 years, mean +/- SD). Twenty-one patients [Group I, consisting of 14 patients younger than 60 years (group IY) nd 7 patients 60 years or older (group IE)] had a normal intrinsic heart rate (IHRo), and 14 patients had an abnormal IHRo [Group II, consisting of 8 patients younger than 60 years (group IIY) and 5 patients 60 years or older (group IIE)]. The basic cycle length was significantly longer in group II than in group I, suggesting that intrinsic sinus node function was more seriously deteriorated in group II in spite of the compensatory effect of autonomic regulation. In group II it was characteristic that the cycle length (CL) after atropine sulfate administration was longer than the CL of the predicted intrinsic heart rate (IHRp). Otherwise, some group II patients might be regarded as normal by atropine sulfate administration alone. Parasympathetic tone showed a negative correlation with age, and it was most enhanced in group IIY, suggesting that parasympathetic negative chronotropy was stronger in this group. In the course of propranolol administration, prolongation of CL was significantly larger in group IIE than in group IIY, but there was no age-related difference in group I. In group II, beta-adrenergic blockade with propranolol administration showed that sympathetic positive chronotropy was a critical compensatory factor around the upper limit of the CL of IHRp.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Assessment by autonomic blockade of age-related changes of the sinus node function and autonomic regulation in sick sinus syndrome.

Age-related changes of the sinus node (SN) function and the autonomic influence on the SN function were evaluated in 65 patients with sick sinus syndrome (range 14 to 84 years). Heart rate (HR), corrected SN recovery time and sinoatrial conduction time were measured before (basic) and after (intrinsic) autonomic blockade (propranolol 0.2 mg/kg plus atropine 0.04 mg/kg intravenously). Percent of autonomic chronotropies of the SN function were calculated by the following formulas: (1)--(intrinsic HR--basic HR/intrinsic HR) X 100; (2) (intrinsic corrected SN recovery time--basic corrected SN recovery time/intrinsic corrected SN recovery time) X 100; (3) (intrinsic sinoatrial conduction time--basic sinoatrial conduction time/intrinsic sinoatrial conduction time) X 100. Basic HR, basic corrected SN recovery time and basic sinoatrial conduction time did not vary with age. Intrinsic HR decreased with age, but this correlation was weak (r = -0.54, p less than 0.001). Intrinsic corrected SN recovery time and intrinsic sinoatrial conduction time tended to increase with age (r = 0.26, p less than 0.05; r = 0.29, p less than 0.05, respectively). Percent chronotropies of HR, corrected SN recovery time and sinoatrial conduction time were negative values in younger patients and positive values in elderly patients; they correlated positively with age (r = 0.59, p less than 0.001; r = 0.60, p less than 0.001; r = 0.43, p less than 0.001, respectively). Thus, the basic SN function did not change with age, while the intrinsic SN function deteriorated with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Aneurysm of patent ductus arteriosus in an adult case: findings of cardiac catheterization, angiography, and pathology.

A 42-year-old male was admitted to our hospital for evaluation of a left precordial continuous murmur. Results of catheterization revealed a step-up of oxygen content in the pulmonary arteries and the calculated left-to-right shunt flow was 40% of the pulmonary arterial flow. Furthermore, aortography unexpectedly revealed an aneurysm of the patent ductus arteriosus. During surgery, the aneurysm was discovered to arise from the frontal wall of the ductus arteriosus, and histological observation showed focal necrosis and mucoid degeneration of the media of the aneurysmal wall in contrast to a thickened intimal fibroelastosis of the adjacent ductal wall. This is presumed to be the first adult case of patent ductal aneurysm ever reported in which antemortem diagnosis and surgical treatment were successfully conducted. Our case may suggest that the fragility of the ductal wall following the structural change in an incomplete closing process is considered as a potential pathogenesis of ductal aneurysm formation.

Adult↗