Search PubMed⌕ Search

Biomedical subjects

J Asayama

Publications and source records attributed to J Asayama.

At least 73 records · Page 4Linked to original sources
PubMed1989

The contribution of an extrasystole to postextrasystolic potentiation in papillary muscles of guinea pigs.

It is well known that a short rest period during the regular stimulation of isolated cardiac muscle induces a transient increase of subsequent twitch tension, although the mechanism of postextrasystolic potentiation (PESP) is still unclear. This paper is concerned with the contribution of an extrasystole to the PESP using isolated papillary muscle of guinea pigs. We have found that the length of the coupling interval of the extra-stimulation prior to the rest interval affected the degree of PESP in a coupling interval-dependent way at the same rest period, and the PESP of the same coupling ratio increased and decreased at the rest period was prolonged. Theophylline increased the strength of steady-state twitch tensions, whereas the dependency of PESP on a coupling ratio of extra-stimulation was removed and the PESP decreased with prolonged rest periods. The evidence suggests that the coupling ratio of extra-stimulation might vary the relative contributions of trans-sarcolemmal Ca influx and Ca release from the sarcoplasmic reticulum.

Animals↗
PubMed1989

[Thallium-201 myocardial perfusion imaging during transient coronary occlusion at the time of PTCA: comparison with stress imaging].

To evaluate myocardial perfusion during transient coronary arterial occlusion, thallium-201 was administered intravenously during percutaneous transluminal coronary angioplasty (PTCA) in 12 patients with effort angina, and the resulting perfusion images were compared with those of exercise stress obtained before PTCA. Thallium-201 was injected at the last inflation of an angioplastic balloon and occlusion was maintained for 60 to 90 sec. Three projections of planar images were obtained immediately after PTCA, using a portable gamma camera in an angiography room. These perfusion images obtained during PTCA and exercise were visually interpreted and compared. Myocardial perfusion defects due to the responsible vessel occlusion were observed at early imaging after PTCA, and were fully redistributed three hrs post injection. In 10 patients without angiographically imaged collateral vessels, there were no significant differences in perfusion between images during PTCA and during exercise. Two patients whose collaterals were observed during coronary angiography before PTCA had higher perfusion scores during PTCA than during exercise. We concluded that intravenous injection of thallium-201 during PTCA is a useful means for assessing alteration of myocardial perfusion due to transient coronary occlusion without increasing the risk of angioplastic procedures, and that it provides more precise information about the jeopardized myocardium, perfused by antegrade blood flow.

Angioplasty, Balloon↗
PubMed1989

[An examination of left ventricular peak filling rate and ventricular relaxation rate by simultaneous acquisition of radionuclide ventriculography and left ventricular pressure].

We investigated whether peak filling rate (PFR) obtained from ECG gated radionuclide ventriculography (RNV) reflects left ventricular (LV) relaxation rate or not. Five patients with angina pectoris, 5 patients with old myocardial infarction and 6 controls were studied by simultaneous acquisition of RNV and LV pressure. RNV was performed in modified left anterior oblique position before and during angiotensin II (A II) infusion to elevate their blood pressure about 25 mmHg (A-1) and 50 mmHg (A-2). The data were acquired in a list mode and LV volume curves were reconstructed by forward and backward gating from the R wave of ECG. Actual PFR and corrected PFR by stroke volume (/SV), by end diastolic volume (/EDV), by instantaneous volume (/IV) were calculated from LV volume curve and its first differential curve. LV pressure was simultaneously measured by the catheter-tip micromanometer, and the time constant (T) of assumed exponential decline in LV pressure was calculated as index of LV relaxation rate. Although there was no correlation between actual PFR and T, corrected PFR (/EDV) and PFR (/IV) correlated with T. PFR (/EDV) decreased and T increased during A-1 and A-2. Decrease of PFR (/EDV) corresponded with increase of T. Thus, corrected PFR (/EDV) obtained from RNV reflects the rate of LV relaxation, and was considered to be an useful index to evaluate LV diastolic function.

Adult↗
PubMed1989

[Evaluation of transient dilation of the left ventricle on exercise thallium-201 scintigraphy].

We have noted that some patients with ischemic heart disease have a pattern of transient dilation of the left ventricle on the immediate post exercise images as compared with 3 hour redistribution images. We assessed correlation between transient dilation of the left ventricle and coronary arteriographic findings in 32 patients with ischemic heart disease and 15 controls. Initial and delayed conventional short axis tomographic images were obtained after reconstruction of 20 projections acquired over 180 degrees. Thirty six radii by every 10 degrees were generated from the center of the middle myocardial images of the short axis. An area surrounded by thirty six points of maximal count on each radius was calculated in initial and delayed images. Transient Dilation Index (TDI) as an index of dilation was determined by dividing an area in initial image by an area in delayed image. There was no difference in TDI between patients with 1 vessel disease and controls, but TDI in patients with two vessel disease and patients with three vessel disease was larger than that in controls. Thus, transient dilation of the left ventricle on exercise Tl scintigraphy was likely to be related to number of stenotic vessel. We concluded that TDI as a simple quantitative index of transient dilation of the left ventricle was useful for detecting multi vessel stenosis.

Cardiomyopathy, Dilated↗
PubMed1989

Cinevideodensitometric quantification of relative coronary arterial stenosis: application to evaluating candidates for percutaneous transluminal coronary angioplasty.

As an alternative to visual interpretations of subjects' angiograms, coronary arteries dilated by percutaneous transluminal coronary angioplasty (PTCA) were evaluated using cinevideodensitometry, and the results were compared with those obtained by the edge detection method. Coronary arteriograms were obtained in various projections and suitable frames were selected for analysis. The frames were transformed to digitized images (512 X 512 X 8 bits) with an image analyzer (MIPRON 1), and cinevideodensitometric and edge detection analyses were performed. Phantom models of various shapes were opacified with contrast medium and were used to test our system. The cineangiograms of 58 patients with ischemic heart disease, 28 of whom had underwent PTCA, were analyzed. A highly linear correlation was observed between the cross-sectional areas of the phantoms and the summed gray levels measured using cinevideodensitometry. Percent area stenosis evaluated by the two methods was accurate and reproducible in measuring the symmetrical stenosis models. However, for the model of asymmetrical stenosis, the measurement by the edge detection method differed according to various projections. Similar results were obtained measuring asymmetrical stenosis in the right coronary artery in vivo in various projections. Based on these experimental results, coronary stenoses dilated by PTCA were evaluated. Prior to PTCA, coronary arterial stenosis measured using the two methods closely approximated each other. However, following PTCA, there were discrepancies between the measurements by the two methods in six cases. This can be accounted for by asymmetrical changes in a luminal cross-section, which cannot be accurately assessed using the edge detection method in single plane projection. In conclusion, cinevideodensitometric measurements of relative coronary arterial stenosis were objective, accurate, and reproducible. According to cinevideodensitometric analysis, eccentric lesions can be measured using a single projection, and tracing arterial borders is unnecessary. It is a useful means in measuring quantitatively the degree of dilatation of coronary arterial stenosis accomplished by PTCA.

Angiography↗
PubMed1989

[Ultrasonic tissue characterization by spectral analysis of myocardial textural pattern].

Based on the fact that ultrasonic myocardial textural patterns are more irregular in the pathological myocardium than in the normal, evaluation of the myocardial tissue character was attempted in vivo using spectral analysis. Parasternal left ventricular long-axis echocardiograms were obtained from five patients with old myocardial infarction diagnosed by history, electrocardiography and coronary angiography. These echocardiograms were transferred to an image analyzer and digitized (256 x 256 x 8). The waveforms of the gray-scale-changes from the normal myocardium showed periodicity in each 8-pixel cycle, but those from the infarcted myocardium did not. To quantify pattern changes in gray-scale values in the ultrasound beam direction, spectral analysis was performed by the maximum entropy method (MEM). There were four peaks in the MEM spectra both in the normal and infarcted myocardia, but there was a great significance in these patterns: with high, steep peaks in normal MEM spectra, and low, blunt peaks in infarcted ones. By discriminatory analysis of these four peak values, normalized by the whole spatial frequencies as multivariate, the misclassification rate was 4.8-22.7% in anteroseptal infarctions and 5.0-20.0% in posterior infarctions. Thus, spectral analysis of the myocardial textural pattern has advantages for analyzing routine echocardiograms without corrections by any absolute ultrasonic references. Furthermore, the misclassification rate is so low that we are able to characterize myocardial tissue.

Echocardiography↗
PubMed1989

[Effect of mexiletine on human atrial vulnerability].

The effect of mexiletine on human atrial vulnerability was investigated in 14 subjects (8 with paroxysmal atrial fibrillation, 2 with paroxysmal atrial tachycardia, 2 with ventricular tachycardia, 1 with sick sinus syndrome and 1 with Wolff-Parkinson-White syndrome). During the electrophysiologic study, after 8 consecutive stimuli (A1) were delivered through the electrode catheter positioned at high right atrium, premature stimulus (A2) was introduced, and following measurements were made; 1) Aw: atrial activity width of A1, 2) maximum atrial fragmentation (MAF): the longest atrial activity width of A2, which was expressed by the relative value against Aw, 3) fragmented atrial activity zone (FAZ): the zone of the coupling interval (A1A2) with the prolongation of the atrial activity width at A2 more than 150% against Aw, 4) conduction delay zone (CDZ): the zone of A1A2 with the prolongation more than 20 msec of the intraatrial conduction time at A2 from high right atrium to coronary sinus or low right atrium against the intraatrial conduction time at A1, and 5) right atrial effective refractory period (RAERP). These measurements were repeated after the intravenous administration of mexiletine (2 mg/kg/10 min). 3 cases (case 12, 13 and 14), whose FAZ and CDZ were 0 msec, were excluded from the following evaluation. Mexiletine showed little effect on Aw and RAERP, but significantly shortened MAF and FAZ (p less than 0.001 and p less than 0.05, respectively). CDZ were also reduced in 3 cases and remained unchanged in 6 cases, though no statistical difference of CDZ was recognized between before and after the administration of mexiletine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A case of left ventricular aneurysm of uncertain etiology presenting as ventricular tachycardia.

A case of a 59-year-old Asian male with several episodes of syncope and palpitation is reported. Electrophysiologic study disclosed that sustained ventricular tachycardia was induced by programmed electrical stimulation at the right ventricular apex. The electrogram in the left ventricular aneurysm showed delayed activities and the fastest depolarization. Entrainment was observed by faster pacing. Left ventriculography showed a large aneurysm and normal coronary arteries. Congenital left ventricular aneurysm is the most likely clinical diagnosis given the lack of past history of chest pain, myocarditis, cardiomyopathy, etc. Congenital aneurysm which presents as ventricular tachycardia is very rare, and has never been reported in an Asian. Medical management has thus far been successful.

Bundle-Branch Block↗
PubMed1988

[Transmitral blood flow velocity patterns evaluated by pulsed Doppler echocardiography in diagnosing transient myocardial ischemia].

To evaluate the influences of transient myocardial ischemia on transmitral blood flow velocity patterns, pulsed Doppler echocardiography was performed during coronary artery occlusion in 10 anesthetized open-chest dogs, and also during esophageal pacing or the administration of dipyridamole in 79 patients with coronary artery disease (CAD), and in 19 control subjects. During occlusion of the coronary artery, an abrupt decrease in the peak velocity of the rapid filling wave (R) was noted within one min simultaneously with rapid decrease of % wall thickening in the ischemic regions. The peak velocity of atrial filling was augmented compensatorily. Although the transmitral blood flow velocity pattern did not change in the controls with esophageal pacing, changes similar to those which were obtained during experimental studies were demonstrated in CAD patients. There were no significant differences between transmitral blood flow velocity patterns of patients with multivessel disease and those with single vessel disease. Ischemic changes in transmitral blood flow velocity patterns were not demonstrated in patients with mitral regurgitation. Sublingual nitroglycerin normalized post-pacing abnormal blood flow velocity patterns. In contrast, after the intravenous administration of 0.56 mg/kg of dipyridamole, R and A were increased and the A/R ratio was unchanged both in CAD patients and the control groups. Deceleration time, or the half time, was prolonged during both provocation tests in CAD patients, and these changes were transient and were restored within several min. Furthermore, they were noted more frequently than was the development of ST depression on ECG, or chest pain. These findings indicate that the transmitral blood flow velocity patterns obtained by pulsed Doppler echocardiography are useful for detecting transient myocardial ischemia, though they have limitations in diagnosing the extent of coronary artery disease.

Animals↗
PubMed1988

[Value of exercise echocardiography in evaluating left ventricular systolic function in mitral stenosis].

Exercise echocardiography was performed for 34 patients with mitral stenosis (MS) to evaluate left ventricular (LV) systolic function. The patients were categorized in three groups according to the work loads attained: Group I, 14 patients who attained 25 watts; Group II, 10 patients, 50 watts; and Group III, 10 patients, 75 watts. Among these groups, there were no statistical differences between the resting echocardiographic LV systolic function and their cardiac catheterization data. Resting LV end-diastolic and end-systolic dimensions (EDD and ESD) did not differ by group. During exercise, EDD and ESD decreased significantly in all groups, but ESD at the maximum exercise in Group I was greater than those of the other groups. The percent fractional shortening of the left ventricle (%FS) decreased significantly with exercise in Group I, while it increased significantly in the other groups. The mean velocity of circumferential fiber shortening (mean Vcf) increased significantly in all groups, but the extent was least in Group I. The exercise-induced changes in %FS (delta %FS) and mean Vcf (delta mean Vcf) correlated closely with exercise duration (r = 0.80, r = 0.73), but this was not the case in the mitral valve area. Postoperatively, exercise echocardiography was also performed for 14 patients with mitral stenosis; two of seven patients in Group I, four of five in Group II, and two in Group III showed significant improvement in exercise tolerance after surgery. However, the other six patients showed no change in their exercise tolerance. The former patients had positive values in delta %FS and more than 0.5 circ/sec in delta mean Vcf during pre-operative evaluations, while except one patient, those who did not improve had negative delta %FS values and less than 0.5 circ/sec in delta mean Vcf. It was concluded that the change in LV systolic function during exercise echocardiography reflects LV functional reserve in patients with MS, and provides valuable information for evaluating the severity of, indications for and benefits from surgery for MS.

Blood Pressure↗
PubMed1987

[Transmitral flow patterns during acute coronary artery occlusion: experimental and clinical evaluations by pulsed Doppler echocardiography].

To evaluate left ventricular diastolic properties during acute myocardial ischemia, transmitral flow patterns were analyzed by two-dimensional pulsed Doppler echocardiography. In a preliminary study of transient coronary artery occlusion in anesthetized open-chest dogs, the following results were obtained: decreased peak velocity of rapid filling, prolonged rapid filling period, and compensatory increase in the peak velocity of atrial filling. These changes occurred nearly concomitantly with decreased cardiac output, elevated left atrial and left ventricular end-diastolic pressures, and decreased left ventricular systolic pressures. With reperfusion of the coronary artery, these parameters rapidly returned to the base line values. In acute and transient myocardial ischemia induced by intracoronary balloon inflation during therapeutic percutaneous transluminal coronary angioplasty (PTCA) in man, similar changes in these parameters were observed, and the changes were more marked in PTCA for the left anterior descending artery as compared with that of the right coronary artery. In conclusion, noninvasive two-dimensional pulsed Doppler echocardiography is of practical use in evaluating deterioration of the diastolic function of the left ventricle during acute and transient myocardial ischemia.

Angioplasty, Balloon↗
PubMed1987

[Clinical utility of spatial color mapping vectorcardiography in diagnosing myocardial infarction: comparison with 201Tl scintigraphy].

The feasibility of spatial color mapping vectorcardiography in diagnosing the site and extent of the old myocardial infarct was evaluated in comparison with 201T1 scintigraphy. Vectorcardiographic data made by Frank's technique were entered in the personal computer and the QRS complexes were plotted over 112 points crossing the latitude of each 20 (from 20N to 80S) degrees and longitude of each 20 degrees from 20W to 20E on the spherical body. Eight colors were assigned according to the direction of the QRS vector. To construct a territorial map, the apical, then, the septal, anterior, lateral, inferior and posterior portions were determined from the normal 201Tl scintigrams. Myocardial images obtained in the anterior, left anterior oblique and lateral projections were analyzed by the circumferential profile curve. Diagnostic specificity for infarction was greater than 60%, and especially high (90%) in the anterior, apical and lateral regions, but relatively low (50%) in the septal, inferior and posterior regions. Accuracies exceeded 64%. The infarcted areas assessed by spatial color vectorcardiography agreed with those assessed by 201T1 myocardial scintigraphy. Thus, spatial color vectorcardiography was simple and useful for diagnosing the site and extent of myocardial infarction.

Adult↗
PubMed1987

[Right ventricular systolic and diastolic functions assessed by 81mKr scintigraphy and relation to ventricular septal ischemia].

Right ventricular (RV) systolic and diastolic functions were assessed in patients with previous anteroseptal myocardial infarction to ascertain the influence of interventricular septal ischemia on RV function. Gated right ventriculography with continuous infusion of krypton-81 m was performed in 12 normal subjects and 28 patients with infarction but without significant stenosis of the right coronary artery. Furthermore, RV contractile reserve by postextrasystolic potentiation was evaluated by gated radionuclide ventriculography with 99mTc-HSA. The patients with anteroseptal infarction were divided into two groups by the presence or absence of three hours' redistribution in the septal region on exercise thallium-201 myocardial scintigraphy. Two indices of systolic function (ejection fraction and the peak ejection rate) and three indices of diastolic function (1/3 diastolic filling rate, the peak filling rate and time to the peak filling rate) were derived from the right ventricular time-activity curve and its derivative curve. There was no difference in systolic function among normal subjects and patients with or without redistribution. However, diastolic function was impaired only in the patients without redistribution. The RV contractile reserve in the patients without redistribution was less than in those with it. Thus, RV systolic function was maintained in the patients with anteroseptal infarction, but contractile reserve deteriorated only in severe septal ischemia. Similarly, diastolic function was maintained in mild septal ischemia, but impaired in severe septal ischemia. We concluded that RV systolic and diastolic functions are closely related to interventricular septal ischemia.

Diastole↗
PubMed1986

[Left ventricular function during atrial fibrillation assessed by left ventricular function curve using ECG-gated blood pool scintigraphy].

Cardiac function is difficult to assess in patients with atrial fibrillation due to the widely fluctuating cycle lengths resulting in variable ventricular hemodynamics. With respect to ECG-gated blood pool scintigraphy, distortion of the time activity curve occurs due to a summation of irregular cycle lengths. Therefore, performing such a study has been regarded meaningless. To evaluate left ventricular function during atrial fibrillation using scintigraphic technique, a new processing algorithm was devised to make multiple gated images which are discriminated by the preceding R-R interval, and left ventricular filling and function curves were established. The left ventricular filling curve, obtained by plotting end-diastolic volume against the preceding R-R intervals demonstrated an impairment of blood filling in cases of mitral stenosis and constrictive pericarditis, which resolved after mitral commissurotomy in case of mitral stenosis. The left ventricular function curve, established by plotting stroke volume against end-diastolic volume, was analyzed according to indices such as "slope" and "position". Both of these indices were significantly reduced in relation to the severity of heart failure according to the NYHA's functional classification and cardiomegaly on chest radiography. On individual comparisons of underlying diseases, the indices decreased in the following order; lone atrial fibrillation, hyperthyroidism, aging, hypertension, mitral valve disease, ischemic heart disease, dilated cardiomyopathy and aortic regurgitation. The indices correlated closely with ejection fraction. In cases of mitral regurgitation, however, the function curves were situated to the right and above those of lone atrial fibrillation and decreased in slope despite the fairly well-maintained ejection fraction. After treatment with digitalis and/or diuretics, the function curves shifted to the left and upward. In conclusion, left ventricular filling and function curves based on a newly-devised algorithm of ECG-gated blood pool scintigraphy are of considerable clinical value in evaluating cardiac performance in patients with atrial fibrillation. They are widely applicable to the assessment of therapeutic and interventional effects.

Atrial Fibrillation↗
PubMed1986

[Influence of exercise training on left ventricular performance investigated by two-dimensional echocardiography].

The influence of exercise training on left ventricular performance was investigated by exercise two-dimensional echocardiography in 12 top-ranking Japanese volleyball players and 10 untrained subjects. Left ventricular wall thickness and dimension were greater in the athletes than in the nonathletes. The left ventricular wall thickness-internal radius ratio, however, was nearly the same in both groups. At rest, heart rate, the stroke area index, % fractional area and the cardiac index were significantly lower in the athletes than in the nonathletes. During exercise, heart rate was slower in the athletes at every exercise stress stage. The stroke area index, % fractional area and the cardiac index increased linearly in the athletes, although these indices of the nonathletes reached a plateau at the moderate exercise stage. The double product at the last stage was greater in the athletes than in the nonathletes. Both groups did not differ as to segmental fractional area change of left ventricular contraction at rest and during exercise. Serum norepinephrine concentration was significantly lower in the athletes than in the nonathletes at rest. After exercise, however, the difference between the two groups was not apparent. It is suspected that exercise training increased the exercise capacity due to an increase in the left ventricular systolic function reserve, the increment of cardiac VO2 max, and the change of blood flow distribution, and generalized aerobic metabolism in various organs.

Adult↗
PubMed1986

[Cardiac inotropic reserve examined by postextrasystolic potentiation and redistribution of exercise thallium-201 scintigraphy].

Evaluation of regional contractile reserve and the viability of an infarcted segment of the myocardium is very important in determining the indications for aorto-coronary bypass after myocardial infarction and in predicting the prognosis. Regional wall motion of the left ventricle after postextrasystolic potentiation (PESP) was studied in 18 patients with old myocardial infarction, and compared with indices of redistribution of thallium after exercise. Equilibrium radionuclide angiocardiography (RNA) using Tc99m HSA was performed at rest and after PESP produced by a programmable cardiac stimulator via a right ventricular catheter. Regional ejection fractions (REF) were determined, and wall motion was observed visually. The relative thallium activity (RTA) and washout rate (WOR) were obtained from exercise myocardial scintigraphy performed 10 minutes, and 3 hours after thallium-201 injections. Wall motion improved in 12 of 23 infarcted segments after PESP. Regional ejection fraction and relative thallium activity (in three hours, or the difference between the activities of the initial and three hours after exercise) in the improved segments were significantly higher (p less than 0.001) than in the unchanged segments. Washout rate was lower (p less than 0.02) in the improved segments. Significant correlation was observed between the change in regional ejection fraction and relative thallium activity (3 hours after exercise) (r = 0.654, p less than 0.05). Thus, the wall motion of some infarcted regions of the myocardium improved after PESP, and thallium was redistributed during three hours after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise Test↗