Search PubMed⌕ Search

Biomedical subjects

Y Iesaka

Publications and source records attributed to Y Iesaka.

At least 55 records · Page 3Linked to original sources
PubMed1991

Effects of pirmenol on electrical induction of sustained ventricular tachycardia in a seven-day-old canine myocardial infarction.

Effects of pirmenol on electrical induction of sustained ventricular tachycardia (VT) were examined in 14 dogs with 7-day-old myocardial infarctions. Before administration of the drug, sustained VT was induced in 8 of 14 dogs. After administration of 3 mg/kg pirmenol, induction of VT was suppressed in 2 dogs but remained inducible in 6 dogs. After cumulative administration of 5 mg/kg pirmenol, VT was no longer inducible in 3 dogs but in the other 3 dogs VTs were still inducible at increased cycle lengths. After 7 mg/kg pirmenol, VT was not inducible in the remaining three dogs. Arrhythmias could not be provoked in any postinfarction dogs after pirmenol administration. Plasma concentrations after sequential and cumulative administration of 3, 5, and 7 mg/kg pirmenol averaged 0.43, 0.65, and 1.15 micrograms/ml, respectively. Administration of pirmenol increased the effective refractory period (ERP) and paced QRS duration in both the normal and infarcted ventricular myocardium. In the infarcted myocardium, prolongation of the ERP for the second and third extrastimuli was greater than for the first one (p less than 0.05). Results indicate that pirmenol is effective for prevention of sustained VT owing to prolongation of both the ERP and conduction time in recent myocardial infarction.

Animals↗
PubMed1991

Comparative efficacy of subcutaneous mesh and plate electrodes for nonthoracotomy canine defibrillation.

To determine the optimal configuration for the subcutaneous placement of electrodes for the performance of ventricular defibrillation without thoracotomy, internal defibrillation using four different subcutaneous electrodes was performed in 13 anesthetized dogs (7-12 Kg, mean +/- SD: 9.2 +/- 1.5 Kg). An electrode (7 cm2) was positioned transvenously in the superior vena cava with the following electrodes randomly implanted subcutaneously on the left chest: small mesh electrode (14 cm2), large mesh electrode (28 cm2), small titanium plate electrode (14 cm2), and large plate electrode (28 cm2). Ventricular fibrillation was induced by applying alternating current; a monophasic defibrillation wave was administered between the superior vena cava and the subcutaneous electrodes 10 seconds later. The energy level associated with a 50% successful defibrillation, as predicted by logistic regression analysis, was defined as the ED50. After the completion of the defibrillation protocol using the four subcutaneous electrodes, the small mesh electrode was sutured to the epicardium and the ED50 measurements were repeated. Energy ED50s were lower when the superior vena cava electrode was used as the cathode rather than as the anode. Of the subcutaneous electrodes, the large plate electrode showed the lowest energy ED50 (3.3 +/- 0.9 joules). The plate electrodes had lower energy ED50s than the mesh electrodes, and the large electrode had a lower energy ED50 than the small electrodes. Using the epicardium electrode, transient arrhythmias and ST elevation were observed following successful defibrillation; however, no arrhythmias or ST-T changes were observed following defibrillation using the subcutaneous electrodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[A case of Romano-Ward syndrome effectively treated by propranolol and atrial pacing].

A case of Romano-Ward syndrome effectively treated by both propranolol and atrial pacing is reported. A 33 year-old female, who had experienced syncopal episodes since she was 20 years old, had a family history showing her son with QTc 0.46. Her QT-U interval and QTc were both 0.6 second when propranolol was not administered. It shortened to 0.28 second and 0.39 respectively under exercise stress testing, and also shortened to 0.41 second and 0.43 respectively when left satellite ganglion block was used. Electrophysiologic study demonstrated that both sinus and atrioventricular nodal functions were normal, but the refractory periods of right and left ventricle differed significantly, and nonsustained ventricular tachycardia was induced. Her QT-U and QTc intervals shortened to 0.37 seconds and 0.43 respectively through both the treatment of 80 bpm atrial pacing, and the administration of 80mg propranolol. She has never experienced a syncopal episode.

Adult↗
PubMed1990

Prognostic significance of sustained monomorphic ventricular tachycardia induced by programmed ventricular stimulation using up to triple extrastimuli in survivors of acute myocardial infarction.

The prognostic significance of sustained monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation using up to 3 extrastimuli was evaluated in 133 consecutive survivors of acute myocardial infarction (AMI) at a mean interval of 1.8 +/- 1.1 months after onset. This was compared with hemodynamic and angiographic abnormalities shown by cardiac catheterization and ventricular ectopic activity detected by Holter monitoring. Sustained monomorphic VT was induced in 25 (19%) patients, sustained polymorphic VT in 11 (8%) patients, nonsustained monomorphic VT (greater than or equal to 10 beats) in 12 patients (9%) and nonsustained polymorphic VT in 9 patients (7%). Multivariate logistic regression analysis of clinical, angiographic, hemodynamic and electrocardiographic variables showed that the presence of a left ventricular aneurysm (p = 0.005) and Lown grade 4B ventricular ectopic activity (p less than 0.001) were independent predictors of inducibility of sustained monomorphic VT. During a mean follow-up of 21 +/- 13 months, there were 8 (6%) sudden cardiac deaths and 3 (2.3%) spontaneous occurrences of life-threatening sustained VT. The 2-year probability of freedom from sudden cardiac death or sustained ventricular tachyarrhythmias was 53 +/- 13% for patients with inducible sustained monomorphic VT, 70 +/- 10% for those with a left ventricular ejection fraction less than 40% and 58 +/- 13% for those with Lown grade 4B ventricular ectopic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Arrhythmogenic right ventricular dysplasia with sick sinus syndrome and atrioventricular conduction disturbance.

Although arrhythmogenic right ventricular dysplasia (ARVD) is believed to involve primarily the right ventricle, left ventricular abnormalities have also been described. We report a case of ARVD with abnormalities of the sinus node, right atrium and atrioventricular node. The biopsies taken from the right atrium and the right ventricle showed replacement of myocardium by fibrous tissue. The pathologic changes of this disease process may extend into the atrium and atrioventricular node.

Atrioventricular Node↗
PubMed1990

Usefulness of electrophysiologic study and endomyocardial biopsy in differentiating arrhythmogenic right ventricular dysplasia from idiopathic right ventricular tachycardia.

Fifteen patients with right ventricular tachycardia without evidence of coronary artery disease or dilated or hypertrophic cardiomyopathy were evaluated, by means of electrophysiologic study and right ventricular endomyocardial biopsy. Six cases were diagnosed as definite arrhythmogenic right ventricular dysplasia (ARVD), while 2 cases without characteristic findings of ARVD by noninvasive studies and angiography were diagnosed as probable ARVD on the basis of their electrophysiologic and histopathologic data. In conclusion, ARVD is relatively common as an etiology of right ventricular tachycardia, and detailed electrophysiologic study and endomyocardial biopsy appear to be useful for diagnosis of ARVD.

Adolescent↗
PubMed1988

Effects of procainamide and lidocaine on electrically inducible ventricular tachycardia studied with programmed ventricular stimulation in post myocardial infarction.

The effects of procainamide and lidocaine, representative of class IA and IB antiarrhythmic agents, on electrically inducible ventricular tachycardia (VT) were studied using programmed ventricular stimulation in 47 post myocardial infarction patients at an average of 1.5 months after the onset. The mean doses of administered procainamide and lidocaine were 1050 mg and 161 mg, and their mean plasma concentrations were 7.5 micrograms/ml and 3.1 micrograms/ml respectively. The induction of sustained VT was suppressed in 15 of 29 patients (52%) by procainamide, but in none by lidocaine. The induction of nonsustained VT was suppressed in 6 of 18 patients (33%) by procainamide, and in 1 of 8 patients (13%) by lidocaine. The efficacy rate of procainamide was significantly higher than that of lidocaine in suppression of VT induction (21/47 vs 1/14 p less than 0.01). Procainamide significantly prolonged the effective refractory period of the right ventricle as well as the HV and QRS interval, however lidocaine did not affect them significantly. On the other hand, the worsening effect which changed nonsustained VT inducible in the baseline into sustained VT inducible post drug administration was demonstrated in 8 of 18 procainamide cases (44%), and in 3 of 8 lidocaine cases (38%). Between the procainamide effective and ineffective or worsening patients, there were no differences found in the electrophysiologic variables either in the baseline or post procainamide administration. We concluded that procainamide was more effective than lidocaine for the prevention of potential life-threatening VT induction in post myocardial infarction patients, although its efficacy was considerably limited, and to confirm the effectiveness and exclude the worsening effects of the class IA and IB antiarrhythmic agents, drug testing using programmed ventricular stimulation appeared to be valuable.

Cardiac Pacing, Artificial↗
PubMed1988

Hemodynamic studies of nitroglycerin in dogs using an open loop method.

Nitroglycerin is considered to decrease both preload and afterload. To elucidate the actions of nitroglycerin on afterload, venous return was kept constant in this experiment. Three different doses of nitroglycerin, 0.3 microgram/kg/min, 1.0 microgram/kg/min, 3.0 micrograms/kg/min were administered into the ascending aorta of 6 mongrel dogs weighing over 20 kg. These doses of nitroglycerin were randomized in each of six procedures. The plasma concentration of nitroglycerin increased during 10 min of infusion, then it decreased exponentially. Heart rate, cardiac output and left atrial pressure did not change significantly at any dose of nitroglycerin. Systolic blood pressure and systemic vascular resistance (as indices of afterload) decreased significantly during nitroglycerin infusion, especially with the 3 micrograms/kg/min dose. These data suggest that nitroglycerin decreases the afterload. The effects appeared rapidly with administration and disappeared rapidly after cessation of the infusion.

Animals↗
PubMed1987

Comparison of susceptibility of myopotential inhibition between AAI and VVI pacemakers.

Susceptibility of unipolar AAI pacemakers to myopotential inhibition (MPI) was assessed in 10 patients by provocative maneuvers and 24-hour Holter monitoring, and compared to that of unipolar VVI pacemakers in 12 patients. Five maneuvers were performed for each of four different sensitivity levels, and an MPI score of from 0-4 points was given according to the lowest sensitivity level at which MPI was provoked. The MPI score in patients with AAI pacemakers was significantly lower than that in patients with VVI pacemakers, 1.60 +/- 1.26 vs 2.83 +/- 1.03 (p less than 0.05). On Holter monitoring, no MPI was detected in any of the patients with AAI pacemakers, whereas myopotential inhibition was detected in 5/12 patients (42%) with VVI pacemakers. Intracardiac electrograms were of lower amplitudes for AAI pacing than for VVI pacing, 3.13 +/- 1.83 mV vs 11.20 +/- 5.95 mV (p less than 0.01). Although the amplitude of atrial signals was lower than that of ventricular signals, the AAI pacemakers were less susceptible to MPI than were the VVI pacemakers. However, when MPI occurs in AAI pacing, it may be more difficult to correct without undersensing because of the lower amplitude of the intracardiac signals.

Adult↗
PubMed1986

Cardiac syncope: a case exhibiting dichotomy between clinical impression and electrophysiologic evaluation.

This case report illustrates the value of electrophysiologic study in patients presenting with graphically unmonitored syncope and/or sudden cardiac death, and who have clinical markers of both bradycardia and ventricular tachycardia. In our patient, a wide QRS on the electrocardiogram and Holter monitor documented high grade ventricular ectopic activity. In this case, had therapy been solely guided by the clinical impression that the patient had ventricular tachycardia, the treatment would have resulted in increasing the risk of recurrence of syncope and/or sudden cardiac death.

Cardiac Pacing, Artificial↗
PubMed1986

Definition of mixing rate of indicator by indicator dilution method: evaluation of relationship between mixing rate of indicator and cardiac output determination.

It is generally agreed that complete mixing of the indicator is one of the most important factors of the indicator dilution method, however, no clear definition of the mixing state has been established. We established a formula for the mixing rate of the indicator by the indicator dilution method, using the concept of entropy in the information theory, and compared the mixing rate of indocyanine green in one mixing chamber (left ventricle) with that in the two mixing chamber system (including the aortic system). The mixing rate of the indicator (M) is shown as M(%) = 100 H/Hcm = -100 (lk sigma ni = 1 Ci + log Ci + log k) (l & k: correction factors in each dye dilution curve, C: mean concentration of the indicator in the region). Left heart and aortic catheterizations by retrograde femoral and carotid artery approach were performed in five anesthetized dogs. Simultaneous dye dilution curves were recorded at the aortic root and at the bifurcation of the abdominal aorta, following the injection of indocyanine green (2.5 mg/1 ml of indocyanine green for each injection) by impulse into the left ventricle at the endsystole, triggered on the R wave of ECG, using the automatic injector devised by the authors. Twenty-five pairs of dye dilution curves were obtained by simultaneous recording in the aortic root and the abdominal aorta under several hemodynamic conditions, and the cardiac output, mean circulation time and the mixing rate of the indicator were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Clinical evaluation of urapidil, a new antihypertensive drug: preliminary findings in Japan.

The pharmacokinetics, hypotensive effects, and safety of urapidil were investigated in 22 patients with essential hypertension at four coordinated centers in Japan. The drug was administered in sustained-release capsules given twice daily. The peak plasma concentration of the drug (measured in six patients) was observed four to six hours after administration, and 60% to 70% of the peak concentration was detectable at eight hours. These findings suggest that blood pressure might be controlled by twice-daily administration of urapidil. In 14 outpatients, who received 40 to 80 mg/day of urapidil, systolic and mean blood pressure decreased significantly (P less than 0.05) by week 4, and systolic, diastolic, and mean blood pressure decreased significantly (P less than 0.001) by week 6. In four inpatients, treated with 60 to 120 mg/day of the drug for two weeks, there were significant decreases (P less than 0.05) in systolic, diastolic, and mean blood pressure at day 6 and significant decreases (P less than 0.01) in diastolic and mean blood pressure at day 13. Although side effects were noted in five (23%) of the 22 patients, they were transient and slight in three; in two patients, the side effects disappeared after use of the medication was discontinued. Because the study was carried out in a small number of patients who received different dosages of urapidil over a short period of time, the optimal dosage was not established.

Adult↗
PubMed1983

Macroreentry as a mechanism of atrial-induced ventricular ectopic beats: a laboratory curiosity?

During electrophysiologic study in a patient, programmed stimulation of the atrium induced fixed coupled ventricular premature beats on the basis of intraventricular macroreentry. This type of macroreentry, which was reproducible, appears to have been merely a "laboratory curiosity" and never played a clinical role in this patient with chronic recurrent ventricular tachycardia.

Cardiac Complexes, Premature↗
PubMed1983

A permanently implanted endocardial electrode complicating ventricular tachycardia with a second VT.

A VVI pacemaker was permanently implanted for the purpose of suppressing recurrent ventricular tachycardia (VT). Not only did the device fail to suppress the VT, but also the permanent endocardial electrode caused a second VT which was more rapid and clinically more severe. When a new VT occurs in the presence of a permanently implanted ventricular pacing system, the implanted electrode should be considered as one of the possible etiologic causes for the VT.

Aneurysm↗