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Biomedical subjects

M Kaibara

Publications and source records attributed to M Kaibara.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of aprindine on electrophysiological properties of the atrial muscle in man.

The effects of aprindine on atrial vulnerability were studied in 11 patients; 9 with paroxysmal atrial fibrillation (PAF), and 2 with Wolff-Parkinson-White syndrome, aged 19 to 69 (55.9 +/- 16.5; mean +/- SD). Before and 10 min after the intravenous injection of aprindine (1.5 mg/kg), programmed extrastimulation was performed from the right atrial appendage. Atrial vulnerability was assessed by evaluating the repetitive atrial firing zone (RAFZ), conduction delay zone (CDZ), maximum conduction delay (Max. CD) and fragmented atrial activity zone (FAAZ). After the injection, the duration of the P wave and QTc interval was significantly prolonged without any change in blood pressure or heart rate. RAF was observed in 8 patients under control conditions. However, after the injection of aprindine, the RAFZ completely disappeared in 2 patients, was narrowed in 4, and became wider in 1. AF was induced in the remaining patient. The zone significantly reduced (p < 0.01) without any change in CDZ or Max. CD. While FAA was observed in 5 patients under control conditions, it completely disappeared in 2 patients, was narrowed in 1, and did not change in the remaining 7 after the injection of aprindine. In patients whose RAFZ narrowed after administration of aprindine, the wavelength, as determined from the atrial effective refractory period and conduction velocity, was augmented. These results indicate that aprindine suppresses atrial vulnerability with an augmentation of the wavelength. However aprindine exaggerated atrial vulnerability in some patients, such that atrial fibrillation was induced.

Action Potentials↗
PubMed1994

Supernormal atrial conduction and its relation to atrial vulnerability and atrial fibrillation in patients with sick sinus syndrome and paroxysmal atrial fibrillation.

The purpose of this study was to evaluate prospectively the relationship between supernormal atrial conduction (SNC) and the atrial vulnerability to fibrillation in patients with sick sinus syndrome (SSS) and paroxysmal atrial fibrillation (PAF). Programmed atrial stimulation was performed in 32 age-matched control patients (group I), 26 with SSS but without tachyarrhythmias (group II), and 24 with both SSS and PAF (group III) to assess some determinants of atrial vulnerability, SNC, and atrial fibrillation inducibility. Supernormal atrial conduction was observed in 20 (63%) patients of group I, 12 (46%) patients of group II, and 5 (21%) patients of group III (group I vs group III; p < 0.002). The SNC zone was 46 +/- 44 msec in group I, 36 +/- 42 msec in group II, and 12 +/- 24 msec in group III. (group I vs group III; p < 0.001). The absence of SNC showed a specificity of 89% and a positive predictive accuracy of 79% in predicting inducibility of atrial fibrillation. The sensitivity was 33% and the negative predictive accuracy was 52%. The SNC zone showed a significant inverse correlation with P wave duration (r = -0.32; p < 0.003), intraatrial conduction time (r = -0.28; p < 0.02), and maximum conduction delay (r = -0.23; p < 0.05). The maximum decrease in conduction time during supernormal conduction showed a significant inverse correlation with P wave duration (r = -0.27; p < 0.02), intraatrial conduction time (r = -0.26; p < 0.02), and with the maximum conduction delay (r = -0.27; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Mechanism of the suppression of repetitive atrial firing by isoproterenol--comparison with disopyramide.

To investigate whether isoproterenol (Iso) could suppress the initiation of repetitive atrial firing (RAF), we investigated its effect on RAF in comparison with that of disopyramide (Diso). Extrastimuli at a basic cycle length of 500 ms were delivered from the high right atrium in 49 patients who received an intravenous infusion of Iso (0.01 microgram/kg per min) and in 39 patients given intravenous Diso (2 mg/kg per 10 min). Induction of RAF, the atrial effective refractory period (A-ERP), and the maximum conduction delay (MCD) were measured. Iso abolished the induction of RAF in 13/19 (68%) patients, while Diso did so in 13/22 (59%) patients. Thirty-four of the 41 patients with RAF in the baseline study had an A-ERP < 250 ms and an MCD > 40 ms. Iso significantly decreased the A-ERP from 205 +/- 26 to 194 +/- 23 ms (P < 0.01) and significantly decreased the MCD from 67 +/- 24 to 39 +/- 16 ms (P < 0.0001) in 19 patients with RAF. On the other hand, Diso significantly increased the A-ERP from 203 +/- 31 to 235 +/- 36 ms (P < 0.0001), and significantly diminished the MCD from 68 +/- 31 to 55 +/- 30 ms (P < 0.01) in 22 patients with RAF. In patients with new RAF (n = 7) or re-induced RAF (n = 14) during Iso or after Diso, the MCD was more than 40 ms. Our results suggest that there are two different modes of RAF suppression, i.e. shortening or lengthening of the A-ERP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Incidence and electrophysiologic characteristics of supernormal atrial conduction in humans.

The incidence and electrophysiologic characteristics of supernormal atrial conduction (SNC) were examined by cardiac stimulation in 53 control subjects. Their ages ranged from 15 to 71 years (mean age, 50 +/- 21 years) (mean +/- SD). There were 27 women and 26 men in the study. Conduction of premature atrial responses from the sinus node to the atrioventricular node (intraatrial conduction time) was supernormal in 27 (51%) subjects and conduction to the left atrium (interatrial conduction time) was supernormal in 35 (66%) subjects (difference not significant). At coupling intervals ranging between 440 and 240 ms, the conduction time of the premature beats was as much as 25 ms shorter than that of the basic driven beats. The maximum decrease in interatrial conduction time during the period of SNC was 13 +/- 5 ms and the maximum decrease in intraatrial conduction time was 9 +/- 3 ms (P < .001). The supernormal interatrial conduction zone was 71 +/- 29 ms and the supernormal intraatrial conduction zone was 57 +/- 25 ms (P < .05). There was a significant positive correlation between the SNC zone and the maximum decrease in conduction time (r = .82; P < .001). Supernormal atrial conduction was stable, reproducible, and remained constant in individual patients. Supernormal atrial conduction was found to be a relatively frequent phenomenon. There was a significantly greater SNC zone and maximum decrease in conduction time in interartrial conduction than in intraatrial conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Function↗
PubMed1994

Repetitive atrial firing and fragmented atrial activity elicited by extrastimuli in the sick sinus syndrome with and without abnormal atrial electrograms.

Endocardial catheter mapping of the right atrium during sinus rhythm and programmed atrial stimulation were performed in 50 patients with sick sinus syndrome to investigate the relationship between abnormal atrial electrograms recorded during sinus rhythm and some determinants of the atrial vulnerability such as repetitive atrial firing and fragmented atrial activity elicited by single extrastimulus. The patients were divided into 2 groups on the basis of the presence (Group I) or absence (Group II) of abnormal atrial electrograms recorded during sinus rhythm. In Group I (N = 32), repetitive atrial firing was induced in 23 (72%) patients, and in Group II (N = 18) in 6 (33%) patients; p less than 0.01. The repetitive atrial firing zone was 41 +/- 37 ms in Group I and 12 +/- 18 ms in Group II; p less than 0.001. Fragmented atrial activity was induced in 30 (94%) patients from Group I, and in 8 (44%) patients from Group II; p less than 0.0001. The fragmented atrial activity zone was 47 +/- 42 ms in Group I and 14 +/- 19 ms in Group II; p less than 0.0001. The atrial electrogram width at the premature beat (A2; p < 0.02) and the maximum A2/A1 ratio (p < 0.002) were 178 +/- 53 ms and 196% +/- 40%, respectively in Group I, and 141 +/- 36 ms and 159% +/- 30%, respectively in Group II. Atrial fibrillation was induced in 13 (41%) patients from Group I, and in 1 (6%) patient from Group II (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Spontaneous perforation of pyometra: a case report.

Spontaneous perforation is a rare complication of pyometra and is usually associated with uterine cervical occlusion. We report a very rare case of spontaneously perforated pyometra without cervical occlusion. A 56-year-old woman with severe abdominal pain was admitted to our hospital. Exploratory laparotomy was performed because of suspicion of gastro-intestinal perforation with generalized peritonitis. There was no perforation of the stomach, gallbladder, or bowels, but examination of the uterus revealed a perforation of the uterine fundus. A total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed. Pathological investigation of the surgical specimen revealed endometritis and myometritis of the uterus; but there was no evidence of malignancy, and the cervical canal was patent. Although spontaneously perforated pyometra is rare, the condition must be born in mind with regard to elderly women with acute abdominal pain.

Abdominal Pain↗
PubMed1994

Involvement of Na(+)-H+ antiporter in regulation of L-type Ca2+ channel current by angiotensin II in rabbit ventricular myocytes.

The present study investigated the possible involvement of a Na(+)-H+ antiporter in the regulation of L-type Ca2+ channels by angiotensin II (Ang II) in isolated rabbit ventricular cardiac myocytes by using both cell-attached and whole-cell patch-clamp current recording techniques. In cell-attached patch-clamp current recordings, an increase in the open-state probability of the Ca2+ channel (144.8 +/- 9.8% [mean +/- SEM], n = 11) was seen after exposure of the cells to Ang II (100 nmol/L). This effect was inhibited by pretreatment with losartan (10 mumol/L), a synthetic antagonist of the AT1 receptor. 5(N,N-Dimethyl)amiloride (100 mumol/L), an amiloride analogue, as well as Na(+)-deficient bath solution abolished Ang II-induced stimulation of the Ca2+ channel activities. In whole-cell patch-clamp current recordings, Ang II also increased the L-type Ca2+ current when a pipette solution of pH 7.1 containing 5 mmol/L HEPES (139 +/- 5%, n = 4) was used but did not significantly increase the current when a pipette solution of pH 7.5 containing 5 mmol/L HEPES or a pipette solution of pH 7.1 containing 30 mmol/L HEPES was used. These results suggest that Ang II-induced stimulation of the Ca2+ channels is mediated by a Na(+)-H+ antiporter and therefore provide a novel insight into signal transduction of Ang II receptor stimulation in cardiac myocytes.

Angiotensin II↗
PubMed1994

Effects of intravenous verapamil on atrial vulnerability.

To investigate the effects of verapamil on indicators of atrial vulnerability, we examined 30 patients with paroxysmal supraventricular tachycardia who received intravenous verapamil during an electrophysiologic study. Single atrial extrastimuli were given before and after intravenous administration of verapamil to induce repetitive atrial firing (RAF) or atrial fibrillation, and to examine the maximum A2/A1, which was defined as the maximum ratio of the duration of the atrial electrogram resulting from premature stimulation (A2) to that resulting from the basic drive beat (A1). The maximum A2/A1 increased from 145 +/- 20% to 154 +/- 25% (p < 0.02) after verapamil administration. The maximum A2/A1 in patients in whom neither RAF nor atrial fibrillation were induced both before and after verapamil were smaller than those in patients in whom RAF was induced only after verapamil (before; 138 +/- 20% vs 165 +/- 15%, p < 0.02. after; 144 +/- 22% vs 172 +/- 17%, p < 0.05). RAF or atrial fibrillation was induced only after verapamil in 6 patients, who showed a maximum A2/A1 before verapamil of 150% or more. These data suggest that verapamil may induce repetitive atrial firing and possibly atrial fibrillation in some predisposed patients, especially in those that have a greater maximum A2/A1, which may be an indicator of local intraatrial conduction delay before drug infusion.

Adolescent↗
PubMed1993

Anterograde and retrograde decremental conduction over left-sided accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome.

The electrophysiologic properties of left-sided accessory pathways (APs) were examined by cardiac stimulation in 55 patients with Wolff-Parkinson-White syndrome. Atrioventricular and ventriculoatrial conduction times were assessed at the coronary sinus level nearest to the AP and then plotted graphically as a function of coupling interval (for atrial and ventricular refractory period determinations). Of 29 patients with anterograde conduction over the AP, 10 (34%) exhibited decremental conduction. However, only two (7%) had a maximal decrement equal to or more than 30 msec. In the other eight (27%) patients the maximal decrement ranged from 10 to 20 msec. The longest coupling interval at which anterograde decremental conduction was demonstrated ranged from 260 to 440 msec (346 +/- 52 msec). The shortest coupling interval ranged from 240 to 320 msec (265 +/- 24 msec). The anterograde decremental conduction zone was 91 +/- 55 msec. Of 51 patients with retrograde conduction over the AP, 23 (45%) exhibited decremental conduction. However, only eight (15%) had a maximal decrement equal to or greater than 30 msec. In the other 15 (29%) patients the maximal decrement ranged from 10 to 25 msec. The longest coupling interval was 338 +/- 70 msec. The shortest coupling interval was 275 +/- 42 msec. The retrograde decremental conduction zone was 72 +/- 47 msec. There was a significant inverse correlation between the AP effective refractory period and the maximal decrement (r = -0.42; p < 0.05). The comparison of maximal ventriculoatrial conduction time with the maximal decrement revealed a positive correlation (r = 0.63; p < 0.01). These data reveal that minimal decremental conduction over left-sided APs is not an uncommon finding and stress that care should be taken in evaluation of conduction over these connections.

Adolescent↗
PubMed1993

The start-stop-start phenomenon of subdurally recorded seizures.

Defined as a pair of sequential ictal potentials separated by complete or almost complete cessation of seizure activity, the start-stop-start (SSS) phenomenon was found on subdural recordings in 23 (23%) of 98 patients. The two phases were morphologically similar. Thirty-six (58%) of 62 SSS seizures showed a complete stop, a return to interictal morphology being more common than a postictal pattern. Twenty-two (35%) of 62 seizures in 8 (35%) of 23 patients restarted in a different location than the first start. When in different locations, the start, not the restart, correlated with non-SSS origin. SSS seizures arose in the same region as non-SSS seizures in 22 of 23 patients.

Adult↗
PubMed1993

Selective adhesion and proliferation of cells on ion-implanted polymer domains.

We have found that the adhesion and proliferation of endothelial cells can be drastically improved when cultivated on an ion-implanted polymer surface. When the surface of segmented polyurethane, where endothelial cells are not capable of proliferating, is modified by Ne+ or Na+ ion implantation with a fluence of 1 x 10(15) ions/cm2 at an energy of 150 keV, cell adhesion and proliferation occurred selectively on the ion-implanted region irrespective of the ion species. The cells did not proliferate at ion fluences below 1 x 10(14) ions/cm2. Most cells migrated into the ion-implanted domain within 1-2 h, but some of the cells attached outside of the region and then slowly migrated into the region. Ion implantation of polystyrene, on which cells are capable of proliferating, further promoted cell spreading and proliferation, and increased resistance to detachment when the cells were exposed to trypsin.

Animals↗
PubMed1993

Electrophysiologic effects of a new class III antiarrhythmic agent, E-4031, on atrial flutter, atrial refractoriness, and conduction delay in a canine sterile pericarditis model.

Numerous studies have shown that E-4031 generally prolongs the atrial effective refractory period (AERP) without affecting cardiac conduction. The effects of E-4031 on AERP and cardiac conduction at short cycle lengths (CLs) close to the AERP were measured in 12 dogs with sterile pericarditis. Three pairs of electrodes were sutured at three sites in the atria 4 days after the model was created. We measured AERP and maximum conduction delay (MCD) after 8 beats train at CLs of 400, 300, 200 and 150 ms before and during continuous infusion of E-4031 (0.1 microgram/kg/min) that followed an initial dose of 10 micrograms/kg/min/5 min. E-4031 interrupted sustained atrial flutter (AF) (> or = 10 min) in 4 of 5 episodes and atrial fibrillation (> or = 10 min) in 4 of 4. The CL of AF defined as a rapid atrial rhythm (rate > or = 240 beats/min) in five episodes studied in the sterile pericarditis model was significantly (p < 0.005) prolonged from 120 +/- 8 to 160 +/- 17 ms. There were significant (p < 0.005) increases in AERP at each CL, and prolongation of AERP was 39 +/- 18, 31 +/- 14, 23 +/- 14, and 16 +/- 14 ms at CL 400, 300, 200, and 150 ms, respectively. E-4031 produced less prolongation of AERP at short pacing CLs and had no effect on conduction time during atrial rapid pacing at CLs > 150 ms. E-4031 did not prolong MCD at CL 400 ms, but did prolong MCD at CLs of 300, 200, and 150 ms, despite prolongation of AERP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Relationship between atrial conduction defects and fractionated atrial endocardial electrograms in patients with sick sinus syndrome.

The relationship between abnormal atrial electrograms (AAE) recorded during sinus rhythm by endocardial catheter mapping of the right atrium and the atrial conduction defects of sinus impulses or single atrial extrastimuli was investigated in 44 patients with sick sinus syndrome. The patients were divided into two groups on the basis of the presence (n = 29) or absence (n = 15) of AAE recorded during sinus rhythm. The P wave duration in the AAE (+) Group patients was 137 +/- 14 msec, and 125 +/- 15 msec in the AAE (-) Group; P < 0.02. The intraatrial conduction time of sinus impulses in the AAE (+) Group was 54 +/- 12 msec, and 39 +/- 9 msec in the AAE (-) Group; P < 0.001. The interatrial conduction time in the AAE (+) Group was 101 +/- 14 msec, and 78 +/- 16 msec in the AAE (-) Group; P < 0.001. In the AAE (+) Group, 11 (38%) patients had a sinus node recovery time > 4 seconds, whereas in the AAE (-) Group there was only one (6%) patient; P < 0.03. AAE showed a specificity of 93% and a positive predictive accuracy of 91% in predicting inducibility of atrial fibrillation. The sensitivity was 35% and the negative predictive accuracy was 42%. Sustained atrial fibrillation was induced in ten (35%) patients of the AAE (+) Group, and in one (7%) patient of the AAE (-) Group; P < 0.05. These data suggest that in patients with sick sinus syndrome who possess abnormal endocardial electrograms in sinus rhythm within the right atrium have: (1) a significantly longer P wave duration; (2) a significantly longer intraatrial and interatrial conduction time of sinus impulses; and (3) a significantly greater sinus node dysfunction and higher incidence of induction of sustained atrial fibrillation. It is concluded that there are significantly greater atrial conduction defects in patients with sick sinus syndrome who possess AAE within the right atrium during sinus rhythm.

Adult↗
PubMed1993

Double response of the ventricle during transient entrainment in a common atrioventricular nodal reentrant tachycardia.

We report a patient with slow-fast atrioventricular (AV) nodal reentrant tachycardia, in which double ventricular response was demonstrated during rapid pacing at cycle length of 300 msec or less from the high right atrium. The determinants of double ventricular response during transient entrainment in the present case were: (1) a crucial conduction delay in the slow pathway; (2) the collision between the activation via the antegrade fast pathway (antidromically) of the last paced beat and the activation via the antegrade slow pathway (orthodromically) of the previous paced beat, instead of the unidirectional block in the slow pathway; and (3) the enhanced AV nodal conduction over the antegrade fast pathway.

Adult↗
PubMed1993

[A study on hemorheology of pregnant women with obesity].

The hemorheological properties of women with obesity were studied during pregnancy. Blood viscosity at a shear rate of 0.5/sec was measured with a Contraves Low Shear 100 viscometer and that at a shear rate of 115/sec was measured with a Well-Brookfield viscometer. The levels of blood viscosity (both shear rates) of non-pregnant and pregnant women with obesity were significantly higher compared than those of control women. Plasma viscosity was similar in both groups. The filterability of erythrocytes was determined with a St. George's Filtrometer. The initial relative filtration rate, which represented the deformability of each red cell, was similar in both groups. The clogging rate which represented the properties of red clogging capillaries was increased in non-pregnant women with obesity as compared in non-pregnant control women. However, it was similar in pregnant women in both groups. Hematocrits were increased significantly in women with obesity both in non-pregnant and pregnant states. There was no significant difference between fibrinogen levels in the two groups. The results of the present study suggested that the high frequency of pre-eclampsia among pregnant women with obesity was due to increased Ht and blood viscosity which were factors predisposing to pre-eclampsia.

Blood Flow Velocity↗
PubMed1992

In vitro rheological evaluation of antithrombogenicity or anticoagulability of styrene derivative polymer.

In vitro evaluation of antithrombogenicity or anticoagulability of styrene derivative polymer with functional silyl groups, the polymer treated with acid, polystyrene and glass as a reference was attempted using a rheological method. The results were compared with those obtained from measurements of platelet adhesion. The coagulation process of blood in polymer-coated tubes was monitored using a damped oscillation-type rheometer recently developed. The change of fluidity during coagulation of blood was dependent on the polymers. Poly((4-vinylphenyl)dimethyl-2-propoxysilane) (poly(1)) was more antithrombogenic than polystyrene and acid-treated poly(1). The evaluation of antithrombogenicity or anticoagulability for the polymers and glass by the rheological method coincided well with that obtained from other methods. Furthermore, it was confirmed that the rheological method would be useful for elucidating mechanisms of coagulation of blood as well as thrombus formation in developing artificial blood-compatible materials.

Adult↗
PubMed1992

Different distribution of abnormal endocardial electrograms within the right atrium in patients with sick sinus syndrome.

BACKGROUND: Prolonged and fractionated right atrial endocardial electrograms are characteristic of paroxysmal atrial fibrillation (idiopathic or associated with sick sinus syndrome). The distribution of these abnormal atrial electrograms within the right atrium and the way it is related to the likelihood that patients with sick sinus syndrome will develop paroxysmal atrial fibrillation was studied. METHODS: Endocardial catheter mapping of the right atrium during sinus rhythm was performed in 41 control patients with normal sinus node function and without paroxysmal atrial fibrillation, in 33 patients with sick sinus syndrome but without tachycardia, and in 27 patients with sick sinus syndrome and paroxysmal atrial fibrillation (group 3). The bipolar electrograms were recorded at 12 sites in the right atrium and an abnormal atrial electrogram was defined as lasting > or = 100 ms and/or showing eight or more fragmented deflections. RESULTS: 1195 atrial endocardial electrograms were assessed and quantitatively measured. In patients with sick sinus syndrome and paroxysmal atrial fibrillation 54% of the abnormal atrial electrograms were recorded from the high right atrium, 28% from the mild right atrium, and 18% from the low right atrium. However, in patients with sick sinus syndrome without tachycardia 78% of the abnormal atrial electrograms were recorded from the high right atrium and 22% from the mid right atrium. No abnormal electrograms were recorded from the low right atrium. CONCLUSIONS: In patients with sick sinus syndrome without tachycardia abnormal atrial electrograms generally came from the high right atrium but in patients with sick sinus syndrome and paroxysmal atrial fibrillation abnormal atrial electrograms were more widely distributed in the right atrium. In patients with sick sinus syndrome the greater the extent of the compromised atrial muscle, the greater the likelihood that paroxysmal atrial fibrillation will develop.

Adult↗