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Biomedical subjects

H Katsume

Publications and source records attributed to H Katsume.

At least 37 records · Page 2Linked to original sources
PubMed1991

Prolonged atrial activity due to delayed conduction in the atrium of patients with paroxysmal atrial fibrillation.

We investigated the relationship between the duration of electrical atrial activity and intra-atrial conduction time to determine whether the prolonged atrial activity was due to delayed conduction in the human atrium. The study included 15 patients with paroxysmal atrial fibrillation (PAF) and 15 control patients. The duration of atrial electrical activity was measured by selecting a minimum electrographic amplitude of 50 microV. In patients with PAF, the duration of atrial activity was prolonged in proportion to the delay of interatrial conduction time from the high right atrium to the coronary sinus as the coupling interval of premature extrastimuli was decreased. Both the fragmented atrial activity zone and the interatrial conduction delay zone were wider in patients with PAF than in control patients. It is concluded that assessment of the duration of atrial activity with a minimum amplitude of 50 microV is useful in evaluating human atrial vulnerability since it reflects the atrial conduction delay in patients with PAF.

Adolescent↗
PubMed1991

Effect of cardiac sympathetic nerve stimulation on acutely ischemic myocardium--a comparison with the response to exogenous noradrenaline.

To assess the integrity of an adrenergic nervous function in acute myocardial ischemia, the contractile response of the ischemic region to cardiac sympathetic nervous stimulation (CSNS) was measured in comparison that with to exogenous noradrenaline (NA) infusion. In 13 anesthetized open chest mongrel dogs, haemodynamic changes, segmental wall motion, and the concentration of NA in the efferent coronary vein were measured. CSNS was performed by electrically stimulating the left ansa subclavia. Data concerning baseline values, values during CSNS, and those obtained during NA infusion both before and up to 5 h after coronary occlusion were compared. Regional myocardial blood flow of the ischemic region was also measured using the H+ clearance method. Systolic expansion with coronary occlusion was not changed or augmented by CSNS. However, improvement was observed in all experiments when NA infusion was used. The percent change of systolic shortening, indicating the response of segmental wall motion to CSNS, decreased soon after occlusion, recovered temporarily within 30 min after occlusion, but did not improve throughout the period after 60 min. The decrease of NA overflow into the efferent vein by CSNS showed a biphasic pattern; reduction occurring immediately after occlusion and again 3-5h after occlusion. Throughout these experimental studies it was considered that the preserved responses to the exogenous injected NA represented the contribution of presynaptic factor.

Animals↗
PubMed1991

Visualization of the heart and determination of left ventricular mass in rats by echocardiography.

A high-frequency transducer was used to determine the optimal parameters for visualizing the heart in 40 normal Wistar, 15 SHR, and 10 aorta-banded rats. The rats were 5 to 30 weeks old and weighed between 105 and 705 grams. Two-dimensional and M-mode views of the ventricles, atria, valves, and great arteries were obtained by placing the transducer beneath the rats through the left or right parasternal window in either the prone or the right decubitus positions, respectively. Left ventricular (LV) mass was determined on the basis of a spheroid model; these values correlated well with the LV weight for both the Wistar rats (r = 0.94, p less than 0.001) and the rats with cardiac hypertrophy due to pressure load (r = 0.87, p less than 0.001). These results were highly reproducible. This indicates that echocardiography is useful for obtaining quantitative measurements in rats.

Animals↗
PubMed1991

Electrophysiological effects of sodium channel blockers on guinea pig left atrium.

The electrophysiological effects of five sodium channel blockers (mexiletine, lidocaine, disopyramide, aprindine and flecainide) on the guinea pig left atrium were investigated by recording the action potential and its maximum rate of rise (Vmax). The onset and offset kinetics of use-dependent block of Vmax were analyzed. Lidocaine, aprindine and flecainide were classified clearly as fast, intermediate and slow, respectively. Mexiletine and disopyramide had two components in onset and offset of use-dependent block. Mexiletine showed fast and intermediate kinetics, whereas disopyramide showed intermediate and slow kinetics. Action potential duration at 90% repolarization (APD) was prolonged by disopyramide and mexiletine. The other drugs did not change the action potential duration. Effective refractory period was prolonged by all drugs with relative potency in the following order: disopyramide greater than mexiletine greater than lidocaine greater than aprindine = flecainide. In conclusion, the modes of actions of sodium channel blockers on the atrium were disclosed to be different from those on the ventricle. The pharmacological therapy for atrial arrhythmias should be based on the electrophysiological effects of the drugs on the atrium, not on the ventricle.

Action Potentials↗
PubMed1991

[Electrophysiological effect of verapamil on human atrium].

To investigate the effect of verapamil on atrial vulnerability, the following measurements were performed before and after the intravenous administration of verapamil (0.15 mg/kg) in 10 subjects with paroxysmal atrial fibrillation (Paf), and 10 subjects without Paf (non-Paf). During the sinus rhythm, 1) intra-/interatrial conduction time (Intra-/Inter- ACT); the initial deflection of high right atrium (HRA) to that of His bundel/coronary sinus were measured. After 8 consecutive HRA stimuli (A1), premature stimulus (A2) was introduced by shortening the coupling interval (A1A2) and we measured 2) conduction delay zone (CDZ); the zone of A1A2 with the prolongation of Inter-ACT, 3) % maximum atrial fragmentation (%MAF); % maximum value of the ratio of HRA activity width at A2 (Awt) against that at A1 (Awc), 4) fragmented atrial activity zone (FAZ); the zone of A1A2 with % value of Awt/Awc more than 150%,5) repetitive atrial response (RAR); more than 2 atrial activities which occur in response to A2. (6) right atrial effective refractory period (RAERP). Verapamil significantly shortened CDZ and %MFA, slightly lengthened RAERP, and had RAR disappear in Paf, while it did not effect any indices significantly in non-Paf. We concluded that verapamil could reduce atrial vulnerability in Paf due to blocking of atrial conduction delay mediated by slow response fibers.

Adolescent↗
PubMed1991

[Effect of age on visualization of right atrium by thallium-201 myocardial scintigraphy].

With Thallium-201 (Tl) myocardial scintigraphy, right atrial (RA) myocardium has been visible in the disease involving the right side of the heart. We have found RA visualization in the elderly patients without the evidence of right heart disease. Therefore, we studied the relation of age to the RA visualization with Tl myocardial scintigraphy performed at rest. Planar images of 291 patients without valvular or congenital heart disease were read by two observers and classified into the three by the degree of RA visualization; RA 0 = not visualized, RA 1+ = moderately visualized, RA 2+ = intensely visualized. The results were as follows: 93.1% of under 50 y.o., 77.8% of fifties, 86.7% of sixties, 50.5% of seventies and 36.7% of over 80 y.o. showed RA 0. 6.9% of under 50 y.o., 22.2% of fifties, 8.3% of sixties, 46.5% of seventies and 36.7% of over 80 y.o. showed RA 1+. None of under 60 y.o., 5.0% of sixties, 3.0% of seventies, and 26.6% of over 80 y.o. showed RA 2+. In conclusion, RA visualization in Tl myocardial scintigraphy, suggesting right heart overload, may increase with aging.

Aged↗
PubMed1991

[Apical sequestration in hypertrophic cardiomyopathy: its clinical features and pathophysiology].

The clinical and pathophysiological significance of apical sequestration, in which an apical cavity was sequestered from the remainder of the left ventricle by cavity obliteration was investigated in patients with hypertrophic cardiomyopathy (HCM). Among 196 consecutive patients, 24 with apical sequestration and 70 control subjects proven to have no sequestration with left ventriculography were selected for this study using echocardiography combined with Doppler color flow imaging. Various cardiac disorders occurred significantly more frequently in patients with apical sequestration than in the 70 controls: NYHA > or = II, 83% vs 51%; thromboembolism, 17% vs 3%; ventricular tachycardia, 47% vs 11%; and apical asynergy, 75% vs 4%. Continuous Doppler ultrasound revealed that all 24 patients with sequestration had a high systolic blood flow velocity across the obliterated cavity (2.7 +/- 0.9 m/s). During isovolumic relaxation or early diastolic filling or both, 21 of them had paradoxical jet flow directed toward the basal cavity away from the apex, with the peak flow velocity ranging from 1.0 m/s to 3.5 m/s (mean 1.9 +/- 0.7). The maximal diastolic pressure gradient across the obliterated cavity ranged between 4 mmHg and 49 mmHg using the simple Bernoulli's equation, which suggested a significantly higher pressure in the sequestered apical chamber during early diastole. Patients with sequestration were classified into 2 groups; 17 with (group A) and 7 without (group B) apical hypertrophy. The time interval from the closing of the aortic valve to the onset of filling into the sequestered cavity was longer in group A than in group B (401 +/- 191 vs 131 +/- 145 ms, p < 0.01) as assessed by the pulsed Doppler technique. Angiographic asynergy of the apex was more frequent in group A than in group B (100 vs 29%, p < 0.01). In group B, the midventricular cavity was incompletely obliterated throughout the cardiac cycle; whereas, in group A, it was obliterated completely in systole and partially in diastole. Apical sequestration is not uncommon in HCM; it is accompanied by abnormal segmental wall motion, which may be related to ventricular arrhythmias and thromboembolism. Prolonged cavity obliteration with a higher systolic apical pressure and a persistent diastolic intraventricular gradient may play a pathogenic role in apical aneurysmal formation in the absence of fixed coronary artery disease, particularly in patients with apical hypertrophy.

Adolescent↗
PubMed1991

Quantitative measurements of balloon-to-artery ratios in coronary angioplasty.

To determine the optimal balloon-to-artery ratio in percutaneous transluminal coronary angioplasty (PTCA), the effects of balloon size on the extent of residual stenosis, the incidence of coronary dissection, and the percentage of cases requiring repeat PTCA for restenosis were examined retrospectively. Fifty consecutive patients who underwent elective PTCA for simple and discrete lesion localized in the left anterior descending coronary artery were selected for this study. To measure the absolute cross-sectional area of the adjacent control segment of the artery, we developed a new method of quantitative coronary angiography, a hybrid of cinevideodensitometry and the edge detection method. The balloon-to-artery ratio was calculated as the cross-sectional area ratio between the control segment adjacent to the stenosis and the balloon which was visually selected by the operator during PTCA. Residual stenosis was determined as the percent area of stenosis by our hybrid method using cinevideodensitometry. The balloon-to-artery ratio ranged from 0.4 to 2.4, and a weak but significant inverse correlation (r = -0.51) was observed between the balloon-to-artery ratio and the extent of residual stenosis. In 23 patients whose balloon-to-artery ratios were less than 1.0, residual stenosis was greater (59.9 +/- 11.9% vs 46.0 +/- 19.6%, p < 0.05), and the percentage of repeat PTCA was higher (26% vs 4%, p < 0.05) than in the group of 27 patients whose balloon-to-artery ratios were higher than 1.0. The incidence of coronary dissection was similar in the 2 groups (9% vs 15%, ns). The percent area of stenosis before PTCA, the number of inflations, the inflation pressures, and the inflation times were also similar between these 2 groups. We concluded that the optimal balloon size is slightly more than the control segment dimensions of simple and discrete isolated stenoses of the left anterior descending artery treated at lower inflation pressures, and that an accurate measurement method of the coronary arterial dimensions is necessary to determine this optimal balloon size.

Angioplasty, Balloon, Coronary↗
PubMed1991

[A case of hypertrophic cardiomyopathy with progressive cavity dilatation--a review of serial 201Tl myocardial imaging].

We reviewed 201Tl images of a 32 year old man with dilated hypertrophic cardiomyopathy (DHCM). At 22 years of age, when he was diagnosed as having nonobstructive hypertrophic cardiomyopathy (HCM)IVST; 20mm, Dd; 44mm, EF; 62%), 201Tl images showed only a small defect in the anteroseptal segment. At 27 years of age, when he had the first cardiac symptom as palpitation on exertion, his perfusion defect of 201Tl became wider. At 32 years age, he was hospitalized because of deterioration of congestive heart failure. Echocardiography revealed left ventricular wall thinning(IVST; 6mm), left ventricular cavity enlargement (Dd; 63mm) with a large mural thrombus and reduced left ventricular ejection fraction (EF; 32%). Thus 201Tl images may provide useful information on the process of DHCM from HCM.

Adult↗
PubMed1991

[Evaluation of coronary arterial stenosis before and after PTCA: visual estimation versus computer-assisted analysis].

Coronary arteriogram of 34 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) were evaluated visually and by computer-assisted analysis, that employed an edge detection method and cine-videodensitometry. The results of visual estimation were in general agreement with those of computer-assisted analysis for determination of percent area of stenosis in severe stenosis, and percent diameter of stenosis in slightly stenotic lesions. Before PTCA, the findings obtained by densitometry agreed with those using the edge detection method. However, after PTCA, the results were significantly different. This discrepancy may have been due to asymmetric morphologic changes in the luminal cross sectional area immediately after PTCA, which could not be assessed by the edge detection method in a single-plane view. Through these studies it was concluded that the densitometry is most useful for evaluating the effects of PTCA.

Absorptiometry, Photon↗
PubMed1990

[Value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments].

The aim of this study was to evaluate the value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments following percutaneous transluminal coronary angioplasty (PTCA) and aortocoronary bypass surgery. The relative thallium activity (RTA: the ratio of the count rate in the infarcted segment to that in the intact segment) obtained from delayed images of stress myocardial scintigraphy was used as an index of myocardial viability and was compared with the following parameters. 1) Thallium-201 myocardial perfusion images were made during transient coronary arterial occlusion (PTCA) in eight patients with old myocardial infarction. The RTA of delayed images after successful PTCA was compared with those of stress thallium-201 scintigraphy. There were no significant differences of the RTA between delayed images following PTCA and those of stress myocardial scintigraphy. We therefore, presumed that incomplete redistribution of the delayed images of stress thallium-201 scintigraphy did not truly reflect the degree of coronary stenosis. 2. Regional ejection fraction of the left ventricle after postextrasystolic potentiation (PESP) using equilibrium radionuclide ventriculography was studied in 18 patients with old myocardial infarction, and was compared with the RTA of delayed images of stress myocardial scintigraphy. A significant correlation was observed between the changes in regional ejection fraction by PESP and the RTA three hours after exercise. 3. The RTAs of early and delayed thallium-201 scintigrams were measured at rest in 30 patients with old myocardial infarction, and were compared with the RTA of delayed thallium 201 scintigrams after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

[Coronary flow reserve index corrected by exercise load using Tl-201 SPECT: evaluation by PTCA].

For simple, non-invasive evaluations of coronary flow reserve during exercise, we investigated the coronary flow reserve index using the ratio of change of fractional distribution in the regional myocardium to oxygen demand. The subjects included 24 patients with effort angina pectoris and 11 normal volunteers. PTCA was performed for 11 patients. Using the biological properties of Tl-201, single photon emission computed tomography (SPECT) was performed at submaximal exercise and at rest by two successive injections of Tl-201 within a short time interval (double dose method). The correlation between the fractional distribution in the myocardium (delta-Fract) and the oxygen demand during exercise and at rest were evaluated. delta-Fract correlated well with the rate of change of the pressure rate product (delta-PRP), and delta-Fract/delta-PRP (CRI) was a good indicator of the coronary flow reserve index. CRI in the ischemic region correlated well with the percent area stenosis of the supplying coronary artery and improved with resolution of percent area stenosis of the target coronary artery after PTCA, but in some cases they were not above the normal range. CRI as obtained by exercise SPECT using the double dose method is useful for non-invasively estimating the coronary flow reserve during exercise, and it can be used for evaluating the effect before and after PTCA.

Angina Pectoris↗
PubMed1990

[Long-term follow-up of electrocardiographic changes in patients with asymmetric apical hypertrophy].

The serial electrocardiographic (ECG) changes of 20 patients with asymmetric apical hypertrophy (AAH) were retrospectively reviewed relative to their clinical symptoms, echocardiography and Doppler echocardiography, and thallium-201 perfusion scintigraphy. These patients were followed 4-18 years (mean 8 years). Patterns of the serial ECG changes were as follows: Seven patients (group Ia) had an increase of 10 mm or greater in the highest R wave amplitude in the precordial leads, with newly-developed giant T wave inversion. Five patients (group Ib) had relatively stable ECGs and the changes in the R wave amplitudes of less than 10 mm. Six patients (group IIa) had a decrease of 10 mm or greater in the highest R wave amplitude with mild decreases of negative T wave amplitudes. In the remaining two patients (group IIb) right bundle branch block developed. At the last follow-up study, group IIa had lower R wave amplitudes and longer QTc than did those in group I. The follow-up periods and their mean age did not differ among the groups. At the initial evaluation, exercise limitation was rare in group I; whereas, most of the patients in group II presented symptoms such as palpitation, chest pain or exertional dyspnea. These cardiac symptoms developed slowly but progressively during the follow-up period, and their incidence increased both in groups I and II at the final observation. Left ventricular (LV) wall thickness at the chordal level showed normal values and did not differ between the two groups, but apical wall thickness was greater in group II than in group I. Two-dimensional echocardiography showed a spade-like deformity of the LV in group II. In group I, the LV deformity was less marked and was not noted at the initial examination. Color Doppler echocardiography frequently revealed "paradoxical flow" expelled from the obliterated apex to the base in the early diastolic filling period in group II. Left ventriculography confirmed asynchronous contraction, hyperkinesis in the basal segment and dyskinesis at the apical segment, resulting in this abnormal intraventricular blood flow profiles. Serial studies by thallium-201 (TL) perfusion scintigraphy disclosed that four of the eight patients in group II developed localized hypoperfusion at the apex where a high and homogeneous uptake of TL was previously noted.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

[Different sensitivity of sinus node and atrioventricular node to adenosine triphosphate].

We showed that higher concentration of adenosine 5'-triphosphate (ATP) was required to prolong the spontaneous cycle length of the sinus node (SN) than that required to prolong the spontaneous cycle length of the atrioventricular node (AVN). Spontaneously beating preparations of SN and AVN of rabbit (n = 8) were superfused with Tyrode solution containing 10(-8)-10(-3)M ATP, and action potential was recorded. The negative chronotropic action of ATP was dependent on the concentration. The required concentration of ATP to prolong spontaneous cycle length significantly (p less than 0.01) was 10(-5)M in SN and 10(-6)M in AVN, respectively. At concentrations higher than 10(-6)M, the degree of prolongation was greater in AVN than in SN (p less than 0.01). 10(-7)M dipyridamole enhanced this effect of ATP, while 10(-4)M theophylline reduced it. Action potential duration of 50% repolarization was not changed significantly in either SN or AVN at concentrations up to 10(-3)M. Maximum diastolic potential (MDP) was hyperpolarized from 10(-8)M to 10(-4) M. Hyperpolarization of MDP induced by ATP was greater in AVN than in SN but it was not statistically significant. MDP was depolarized by 10(-3) M ATP in both SN and AVN. The maximum velocity of depolarization was slightly larger in both SN and AVN as the concentration of ATP was increased in the perfusate. However, it was not statistically significant. 10(-3) M ATP decreased the maximum velocity of depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Effect of paced cycle length on sinus node effective refractory period before and after autonomic blockade in patients with sick sinus syndrome.

Effect of basic paced cycle length on sinus node effective refractory period was studied in 22 patients with sick sinus syndrome. Sinus node effective refractory period was measured using three different paced cycle lengths before and after pharmacologic autonomic blockade. Sinus node effective refractory period could be measured at one cycle length, at least, in 59% of the patients before blockade, however, it could be measured at two or more cycle lengths in only 18% of patients because of the chaotic response of sinus node against premature stimuli. It could be measured after pharmacologic autonomic blockade in 68% of the patients at two or more paced cycle lengths. On the other hand, the rest of the patients showed no measurable sinus node effective refractory period at any cycle length, for their sinus node effective refractory periods were shorter than their right atrial effective refractory periods. The comparison of sinus node effective refractory period at different paced cycle lengths was unsuccessful before pharmacologic autonomic blockade, while the refractory period was significantly prolonged as cycle length was shortened after blockade. We concluded that (1) sinus node effective refractory period in humans is prolonged as paced cycle length decreases, (2) the autonomic reflex is the major disturbing factor in measuring sinus node effective refractory period, and pharmacologic autonomic blockade can be usefully employed to eliminate a chaotic sinus nodal response, (3) when sinus node effective refractory period is shorter than right atrial effective refractory period, a shorter paced cycle length should be used for definite measurement of the former.

Adolescent↗
PubMed1989

Combined effects of hypoxia and elimination of glucose on resting and postextrasystolic potentiated contractions of papillary muscle of guinea pigs.

We studied the combined effects of hypoxia and the absence of glucose on postextrasystolic potentiated and resting contractions in papillary muscle of guinea pigs. Postextrasystolic potentiations (PESPs) were evoked following trains of 40 externally applied continuous stimulations. During hypoxia resting (regular) contractions decreased to about 25% of baseline tension at 30 degrees C, whereas postextrasystolic potentiated contractions decreased to about 35% of baseline measurement of postextrasystolic potentiated contraction. In contrast, with reoxygenation, PESPs recovered quickly while resting contractions recovered gradually. Caffeine abolished the potentiation of post-extrasystolic contraction not only in normoxia but also in hypoxia. We speculate that calcium release from the sarcoplasmic reticulum (SR) is attributable to PESP for the most part, and that the trans-sarcolemmal calcium influx generally contributes to the steady-state tensions developed by continuous stimulations. In addition, it seems that PESP works in a ischemic heart to compensate for the decreased tension during hypoxia as a potentiation by a premature ventricular contraction. Trans-sarcolemmal calcium influx might be affected more easily than the SR calcium release, by a combination of hypoxia and the absence of glucose, that is, the sarcolemma may be more susceptible to hypoxic injury than the SR.

Animals↗
PubMed1989

Giant right atrial thrombus in Noonan syndrome combined with Eisenmenger's complex.

A 54-year-old woman with the Noonan syndrome was admitted with congestive heart failure and a giant right atrial thrombus with atrial septal defect detected by two-dimensional echocardiography. The thrombus vanished on oral anticoagulant therapy with warfarin. The thrombus is considered to result from hemostasis in the right atrium due to congestive heart failure and to her specific skeletal characteristics. This report describes the first case of Noonan syndrome with right atrial thrombus.

Echocardiography↗