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Biomedical subjects

H Kasanuki

Publications and source records attributed to H Kasanuki.

At least 91 records · Page 5Linked to original sources
PubMed1996

Enhancement of the L-type Ca2+ current by mechanical stimulation in single rabbit cardiac myocytes.

Anion conductance is known to be activated by mechanical stimulation, such as osmotic cell swelling or cell inflation via the patch pipette, of canine or rabbit cardiac myocytes. The effects of mechanical stimulation on time-dependent currents, however, remain unsettled. Using the whole-cell voltage-clamp method, we have found that mechanical stimuli enhance the L-type Ca2+ current (ICa,L) in rabbit cardiac myocytes. At every membrane potential, ICa,L was reversibly increased by osmotic cell swelling and by cell inflation caused by applying a positive pressure of 10 to 15 cm H2O via the patch pipette. ICa,L was increased during cell inflation by 37 +/- 21% (mean +/- SD, n = 17) in atrial cells and by 37 +/ -8% (n = 7) in sinoatrial node cells in solution containing 2 mmol/L Ca2+. The current-voltage relationship, the inactivation time constant, the steady state inactivation curve, and the conductance properties of ICa,L were all virtually unaffected by mechanical stimulation except for the open probability, which appears to increase. The increase in ICa,L was not dependent on protein kinase A, since an inhibitor peptide of cAMP-dependent protein kinase failed to prevent the increase in ICa,L during mechanical stimuli (n=5). The increase in ICa,L caused by cell inflation was unaffected by the chelation of intracellular Ca2+ by the addition of 10 mmol/L EGTA or 10 mmol/L BAPTA to the pipette solution, suggesting that the effect was not mediated by changes in intracellular Ca2+. Thus, mechanical stimulation due to cell swelling or inflation may itself directly increase ICa,L in rabbit cardiac myocytes.

Animals↗
PubMed1996

[Implantable cardioverter defibrillator].

ICD therapy has been believed to be a last resort therapy for preventing of sudden death due to VT/VF. Since 1980, when clinical use first began, ICD therapy has rapidly increased in use in Europe and in the United State. In Japan, in 1990 clinical investigation began, and in 1996 it received insurance reimbursement. From here on, it should experience a rapid rise in use. However there are many problems such as complications, inappropriate shocks, size, longevity and psychological effects etc. Therefore indication for their use should be carefully considered and it is very important to obtain the patient's informed consent.

Arrhythmias, Cardiac↗
PubMed1996

[Prediction of long-term efficacy of amiodarone for refractory ventricular tachycardia: clinical significance of electrophysiologic study and Holter monitoring].

The usefulness of electrophysiologic study and Holter monitoring for predicting the long-term efficacy of amiodarone was investigated in 31 patients with sustained ventricular tachycardia (VT) and organic heart disease. Patients underwent both electrophysiologic study and Holter monitoring before and during oral administration of amiodarone. These patients were followed up and the difference in the prognosis according to the results of these two tests was examined. During a follow-up period of 887 +/- 678 days, sustained VT recurred in 13 patients and sudden cardiac death in 3. Sustained VT recurred in only one of 11 patients in whom amiodarone was determined effective by electrophysiologic study whereas recurrent VT and/or sudden death occurred in 15 of 20 patients in whom amiodarone was determined ineffective (p < 0.01). Eight of 18 patients in whom amiodarone was determined effective by Holter monitoring, and 8 of 13 in whom it was determined ineffective, suffered recurrent VT and/or sudden cardiac death. Amiodarone was judged effective in 7 patients by both tests (group I) and in 15 by either electrophysiologic study or Holter monitoring (group II). In the remaining nine patients, amiodarone was ineffective by both tests (group III). Recurrent VT or sudden death occurred in none of the patients in group I (0%), in nine group II (60%) and seven in group III (78%). The prognoses of the three groups were significantly different: group I vs II; p < 0.05, group II vs III: p < 0.05, and group I vs III; p < 0.005. The combination of the two drug tests, electrophysiologic study and Holter monitoring, is a useful method for the prediction of the long-term efficacy of amiodarone in patients with sustained VT and underlying heart disease. Patients in whom amiodarone was determined ineffective in both tests, are at high risk for VT recurrence and sudden death, and interventional therapy is recommended.

Administration, Oral↗
PubMed1996

[Short-term and long-term outcome of left heart function after cardioverter defibrillator implantation].

The usefulness and problems of implantable cardioverter defibrillators (ICD) were examined in patients with reduced heart function. Of 36 patients who received ICD for refractory ventricular tachycardia (VT) or ventricular fibrillation (VF), VT and/or VF was associated with underlying heart disease in 26 patients, and VF without underlying heart disease in 10. Of the former 26 patients, 13 with left ventricular ejection fraction (LVEF) of less than 30% were assigned to group A, 13 with LVEF of greater than 30% to group B, and the other 10 with idiopathic VF to group C. Intraoperative death, cardiac death due to heart failure, sudden death, functional status of the ICD, exacerbation of heart failure symptoms and complications were compared between the three groups. There were no intraoperative deaths in any of the groups. During the median follow-up period of 36 +/- 22 months, there was only one sudden death in group A. There were no significant differences between the three groups. There were five cardiac deaths in group A, but none in groups B or C. The cardiac death-free rates 12, 24, and 36 months after implantation in group A were 83%, 60% and 50%, respectively. These values significantly differed from those in groups B and C (p < 0.05). The number of patients who received defibrillation therapy was higher in group A (p < 0.05). Defibrillation therapy was administered earlier in group A than in groups B and C (p < 0.05). The incidence of exacerbation of heart failure after implantation was 69%, 23% and 0% in groups A, B, and C, respectively. In group A, defibrillation therapy was administered in all patients with exacerbation of heart failure. The administration of defibrillation therapy significantly differed from that in patients without exacerbation of heart failure (p < 0.05). Exacerbation of heart failure during the postoperative acute stage occurred in both patients in group A in whom an epicardial lead system was used, but not in the four patients in group B or five in group C (p < 0.05). There were no differences in the incidence of other complications between the three groups. In group A, patients with reduced heart function, ICD greatly decreased the risk of sudden death. However, heart failure mortality remained high. Therefore, ICD may have limitations for improved prognosis. In group A patients, defibrillation therapy was administered in all patients with exacerbation of heart failure or death due to heart failure. In patients with reduced heart function, treatment for heart failure and prophylaxis of VT and/or VF should be administered.

Adult↗
PubMed1996

[Left ventricular lesions in arrhythmogenic right ventricular dysplasia and 12-lead electrocardiographic findings].

Left ventricular lesions in arrhythmogenic right ventricular dysplasia have not been well described, and the relationship between the left ventricular lesions and the 12-lead electrocardiographic findings has not been analyzed. This study examined whether the presence of left ventricular lesions and the extent of right ventricular lesions due to arrhythmogenic right ventricular dysplasia are predictable by 12-lead electrocardiographic findings. The 12-lead electrocardiograms during sinus rhythm and left and right ventriculography were studied in 29 patients (27 males and 2 females, mean age 42.6 +/- 15.5 years) diagnosed by the current criteria for this disease. After evaluation, patients were divided into two groups: those with normal left ventricles (normal group) and those with left ventricular wall motion abnormalities (abnormal group). Seventeen of the 29 patients (59%) were classified into the abnormal group. Left ventricular wall motion abnormalities were located in the posterolateral (4 patients), apical (1), and posterolateral and apical regions (12). QS patterns of abnormal Q waves in lead I, aVL or V5, V6 rS patterns (R/S ratio < 1) in leads I and V6, and/or R or Rs patterns (R/S ratio > 1) in lead V1 were observed in all patients in the abnormal group, but in none in the normal group. There was a positive correlation between the right ventricular end-diastolic volume index and the number of precordial negative T waves (r = 0.746, p < 0.0001), and the time from onset of the QRS to the terminal portion of the epsilon wave in lead V1 (r = 0.627, p < 0.001). The correlation coefficients showed no significant differences between the groups. A left ventricular lesion associated with arrhythmogenic right ventricular dysplasia was not unusual (59%), and our study suggests that the posterolateral and apical regions are the most frequent sites. The presence of these lesions were predictable by the QRS abnormalities. Moreover, regardless of the presence of such a lesion, the extent of the right ventricular lesion is also predictable by the 12-lead electrocardiographic findings.

Adult↗
PubMed1995

Chloride conductance in human atrial cells.

Many types of chloride current have been reported in the hearts of various species; however, the nature of chloride conductance in the human heart is still unclear. We investigated cyclic AMP-dependent chloride current and swelling-induced chloride current in isolated human atrial cells using the whole-cell voltage-clamp method. External application of 1 microM isoprenaline increased calcium current by 391.9 +/- 48.6% (mean +/- S.D., n = 8); however, there was no activation of cyclic AMP-dependent chloride current at steady-state membrane potentials between -80 and +50 mV. Neither external application of 10 microM forskolin nor internal application of 50 microM cyclic AMP activated a cyclic AMP-dependent chloride current. On the other hand, when the same cell was superfused with a 50% hypotonic solution, it exhibited osmotic swelling and an outward rectifying current (6.59 +/- 0.96 pA/pF at +30 mV, n = 10). This swelling-induced current reversed at -26.5 +/- 3.1 mV (n = 10), close to the calculated equilibrium potential for chloride, and it was sensitive to the stilbene-derivative chloride channel blocker. In conclusion, no activation of cyclic AMP-dependent chloride current was observed in human atrial cells. On the other hand, a swelling-induced chloride current was consistently demonstrated and its kinetic properties were similar to those reported in other cardiac myocytes.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1995

Association of sick sinus syndrome with hyperinsulinemia and insulin resistance in patients with non-insulin-dependent diabetes mellitus: report of four cases.

We report four non-insulin-dependent diabetic (NIDDM) patients accompanied by a unique combination of sick sinus syndrome (SSS) and hyperinsulinemia of unknown etiology. SSS of all four cases was due to sinus arrest in association with paroxysmal atrial fibrillation (Rubenstein-III). Of special interest is that one patient showed a high prevalence of SSS and NIDDM among her close relatives. Hyperinsulinemia of moderate degree was seen at fasting state or after carbohydrate ingestion in the absence of obesity. The resistance to the action of insulin on glucose metabolism which was evaluated in three patients by the euglycemic hyperinsulinemic clamp study was found to be comparable to the lowest quartile level for common NIDDM patients. Because insulin is a physiological regulator of cell-membrane Na+/K+-ATPase, we speculate that malfunction of the sinus node automaticity may be caused by chronic exposure to hyperinsulinemia secondary to insulin resistance in these NIDDM patients.

Aged↗
PubMed1995

[Usefulness of 123I-BMIPP myocardial imaging in patients with stable effort angina and unstable angina].

We evaluated the clinical significance of myocardial imaging using 123I-15-(p-iodophenyl)-3-methyl pentadecanoic acid (BMIPP) scintigraphy in patients with stable effort angina pectoris (SAP) and unstable angina pectoris (UAP). Thirty-three patients with SAP were studied using rest BMIPP and stress 201TlCl (Tl) myocardial scintigraphy, and 13 patients with worsening effort type of UAP were also examined using both rest BMIPP and Tl scintigraphy. We compared those BMIPP findings with myocardial perfusion images obtained with Tl and the regional wall motion determined by left ventriculography. In 45% of 282 segments of myocardial ischemia of SAP, the degree of myocardial uptake of BMIPP was concordant with that of stress Tl and the defect score of Tl was higher than that of BMIPP. On the other hand, in 32% of 62 segments of ischemia of UAP, the degree of myocardial BMIPP and Tl uptake was concordant and BMIPP defect score was higher than Tl score. In SAP, the decrease in regional wall motion agreed better with the decrease in myocardial uptake of BMIPP than that of Tl. These results suggest that myocardial ischemic regions decreased BMIPP uptake show the disturbance of fatty acid metabolism and lead to abnormal wall motions. Such ischemic regions may be clinically severe state in patients with angina pectoris.

Aged↗
PubMed1995

[Classification of the site of the conduction disturbance in right bundle branch block using body surface mapping].

We can estimate the conduction disturbance in right bundle branch block (RBBB) using body surface mapping. Characteristics of body surface mapping in the cases with RBBB are classified into three types using the appearance time and the site of the breakthrough. In the first type, breakthrough appeared in the center of the anterior chest within the normal time. It shows the peripheral block of right bundle branch. In the second type, breakthrough appeared in the center of the anterior chest later than the normal time. It shows the conduction delay of the main trunk of right bundle branch. In the third type, breakthrough appeared at the left of the anterior chest later than the normal time. It suggests the complete block of the main trunk of right bundle branch.

Body Surface Potential Mapping↗
PubMed1995

[Characteristics of body surface mapping in the cases of idiopathic ventricular fibrillation].

Body surface mapping was recorded in three patients with idiopathic ventricular fibrillation (VF). A late r' wave appeared and disappeared in the precordial leads in all three patients. In one case, the late r' wave appeared with epithides of VF. In the presence of the late r' wave, the QRS duration was extremely prolonged. However, the appearance time of the breakthrough in the QRS isopotential map was not significantly prolonged. The time of the peaks of the r' wave was elongated in the mid anterior chest. These findings suggest that peripheral conduction disturbances in the right ventricle are related to the occurrence of VF in patients with idiopathic VF.

Adult↗