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C Ibukiyama

Publications and source records attributed to C Ibukiyama.

At least 37 records · Page 2Linked to original sources
PubMed1998

Experimental study of catheter ablation using ultrasound energy in canine and porcine hearts.

UNLABELLED: We examined the efficacy and safety of ultrasound energy in eliminating the arrhythmogenic substrates of atrial as well as ventricular tissue using a newly developed instrument in both in vivo and in vitro experiments. Ultrasound (US) applicators were tested on 79 lesions created on a beating heart in canine cardiac tissue, and on 64 lesions in porcine heart specimens. US lesions were created by using transducers with frequencies around 5-10 MHz. In the in vivo study, we observed a significant decrease in the amplitude of the electrograms recorded from the tip of the ablation catheter during the US application (p < 0.01). In some sites transmural lesions could be created which were well demarcated. Blood coagulum formation was observed on the tip of the ablation catheter on several occasions. In one dog ventricular fibrillation was provoked by the delivery of ultrasound energy to the left ventricle. In the in vitro study, lesion depth increased significantly with a longer duration of energy delivery when the temperature was maintained table (p < 0.001), and the lesion depth increased significantly with higher temperatures of energy delivery when the duration of US application was maintained (p < 0.05). In both cases, no significant change in surface area was observed. The maximum depth of the lesion was 10.3 mm. CONCLUSIONS: An ultrasound energy system is relatively safe and effective for creating lesions large enough to eliminate arrhythmogenic substrates deep in the ventricular myocardium. Although the US system is free from pop phenomenon, the problem of blood coagulation on the catheter tip remains to be settled.

Animals↗
PubMed1998

[Influence of wall thickness on asynergy during exercise two-dimensional echocardiography in patients with old myocardial infarction].

The relationship between left ventricular wall motion worsening (new asynergy; newly developed or worsened asynergy) in the affected part of old myocardial infarction during exercise two-dimensional echocardiography and the wall thickness at diastole was evaluated in 20 patients with more than 51% diameter stenosis in only the infarcted related artery using symptom-limited graded supine bicycle exercise test and two-dimensional echocardiography. End-diastolic wall thickness at normal part of the wall (WtdN) and infarcted parts (WtdI) on the parasternal short-axis view at the papillary muscle level at rest were measured and the wall thickness ratio, WtdI/WtdN x 100(%), was calculated. The rate pressure product at the time when new asynergy appeared and the appearance time of new asynergy after starting exercise were measured in seconds. Mean values for the 20 patients were wall thickness ratio of 75.7 +/- 10.0% (mean +/- SD), new asynergy appearance time of 219 +/- 116 sec after exercise and rate pressure product of 14,209 +/- 2,997 mmHg. beat/min. Smaller wall thickness ratio was associated with lower rate pressure product levels (r = 0.696, p < 0.01) and shorter appearance time of new asynergy (r = 0.772, p < 0.01). There was no significant correlation between the percentage diameter stenosis of the infarct-related artery and appearance time of new asynergy or rate pressure product. New asynergy appeared at a specific infarcted part of the wall, and thinner walls were associated with shorter appearance time of new asynergy with lower rate pressure product levels, regardless of the severity of stenosis of the infarct-related artery.

Adult↗
PubMed1997

In vivo intravascular laser photodynamic therapy in rabbit atherosclerotic lesions using a lateral direction fiber.

BACKGROUND AND OBJECTIVE: This study was performed to evaluate the possibility of inducing regression of atherosclerotic foci by photodynamic therapy (PDT) using hematoporphyrin derivative (HpD). STUDY DESIGN/MATERIALS AND METHODS: Atherosclerotic rabbits were divided into four groups: A (n = 6) and C (n = 6) were given 5 mg/kg of HpD intravenously; Groups B (n = 4) and D (n = 4) were not. Twenty-four hours after HpD administration, the aortae of groups A and B were exposed to 200 mw output argon dye laser beam at 630 nm for 10 minutes; groups C and D were exposed to 400 mw for 5 minutes. Three rabbits from groups A and C and two rabbits from groups B and D were sacrificed immediately after laser photoradiation, being named groups A 0, C 0 and groups B 0, D 0, respectively. Groups A 7, C 7, and Groups B 7, D 7 were sacrificed 7 days after the photoradiation. RESULTS: In groups A 7 and C 7, most intimal cells and endothelial cells had become necrotic and disappeared, and a loss of intima was observed. No such changes were found in groups B 7, D 7. CONCLUSION: The above data suggest that PDT caused effective regression of the atherosclerotic lesions.

Animals↗
PubMed1997

Comparison of lumen area after PTCA by IVUS and QCA.

The coronary lumen area just after percutaneous transluminal coronary angioplasty (PTCA) was assessed by intravascular ultrasonography (IVUS) with 4.3 F cardiovascular imaging systems (CVIS) and quantitative coronary angiography (QCA) with Kontron CARDIO 500. Altogether 34 lesions were divided into two groups by IVUS findings using Nissen's circular shape factor (CSF), which was defined by the (calculated perimeter/observed perimeter), expressing lumen eccentricity. The eccentric group (CSF < or = 0.92) was 22, and concentric group (CSF > 0.92) was 12. The minimum lumen diameter by IVUS and QCA (both edge-detection and densitometric methods) correlated in both the eccentric and concentric groups. As for the lumen area, only the QCA densitometric method in the concentric group correlated with the lumen area determined by IVUS. Despite using QCA, it is almost impossible for angiography to determine the lumen area just after PTCA if an eccentric lesion with a tear or dissection had occurred.

Aged↗
PubMed1996

The beneficial effects of atrial natriuretic peptide on arrhythmias and myocardial high-energy phosphates after reperfusion.

OBJECTIVES: The aim of this investigation was to test whether the administration of atrial natriuretic peptide (ANP) has cardioprotective effects against ischaemic and reperfusion injury. METHODS: Thoracotomized dogs underwent a 30 min left circumflex coronary artery occlusion and 60 min of reperfusion (control group; n = 16). The ANP group (n = 9) received a 20 micrograms bolus injection of synthetic alpha human ANP (SUN 4936) followed by infusion at a dose of 0.1 microgram/kg/min from the beginning of coronary occlusion to the end of the procedure. RESULTS: Administration of exogenous ANP increased plasma ANP immediately and maintained levels at 3000 pg/ml, resulting in an 8-fold increase in plasma cyclic guanosine monophosphate (cGMP) levels. Plasma ANP and plasma cGMP levels did not change at all in controls. There were no significant differences in haemodynamic parameters during ischaemia and reperfusion between the groups. In the ANP group, the prevalence and frequency of ventricular extrasystoles within 10 min after reperfusion decreased markedly [ANP 22% vs. control 100%, P < 0.01, and ANP 1 (1) vs. control 92 (50), P < 0.05, respectively]. No dog in the ANP group had ventricular fibrillation (VF), but the incidence of VF was not statistically significant between the groups [ANP 0% vs. control 25%]. ATP content in the inner layers of the ischaemic myocardium in the ANP group was higher than in controls (P < 0.05) [1.92 (0.28) vs. 1.18 (0.13) mumol/g wet weight]. There was no significant difference in the content of myocardial tissue angiotensin II between the groups. CONCLUSIONS: These data show that the infusion of ANP has cardioprotective effects on myocardial ischaemia and reperfusion in this model. These beneficial effects are probably due to direct effects through cGMP rather than haemodynamic changes.

Angiotensin II↗
PubMed1996

Body surface mapping criteria for diagnosis of left ventricular hypertrophy associated with complete right bundle branch block.

The standard electrocardiographic (ECG) criteria for left ventricular hypertrophy are unreliable in patients with complete right bundle branch block. This study was undertaken to formulate criteria for diagnosing these patients by using body surface mapping. The echocardiographic left ventricular mass was calculated by the Penn method from M-mode measurements. Of 56 patients, 27 were defined as having left ventricular hypertrophy with a left ventricular mass of 215 g or more. Isopotential and isointegral maps of the QRS complex were observed. The QRS isointegral maps were separated into two parts at the end of the downstroke of the initial R wave of vector spatial magnitude. The body surface mapping criteria with the highest sensitivity were EPmax (maximum of early part of the QRS) 45 microV.s or greater (sensitivity 93%, specificity 90%), EPmax/d (EPmax averaged by EP duration) 0.8 mV or greater (sensitivity 93%, specificity 97%), and Max (initial maximum) 2.2 mV or greater (sensitivity 89%, specificity 90%). These results suggest that body surface mapping is a useful technique in diagnosing patients with left ventricular hypertrophy and right bundle branch block.

Aged↗
PubMed1996

Frequency, significance, and mechanism of myocardial ischemia during daily activities detected by Holter dynamic electrocardiogram.

Exercise testing (EX) and Holter ECG (DCG) were performed consecutively in 52 patients with ischemic heart disease. A total of 100 episodes of myocardial ischemia (IE) were recorded during DCG in 30 patients, who constituted 94% of the patients with myocardial ischemia under 6 metabolic equivalents (METs) during EX. A significant increase in heart rate (HR) was observed before the development of IE. The duration of this increase in HR was longer in IE than in periods in which the HR increased above the ischemic threshold, but without ischemia. The incidence of IE showed two peaks at 8-10 am and 4-6 pm. The frequency of IE among all of the periods with increased HR was highest at 8-10 am (51%). IE in the morning was associated with a lower HR than that in the afternoon, and LF/HF, which reflects sympathetic activity, evaluated using power spectral analysis, increased before IE in the morning. The early appearance of myocardial ischemia in EX can predict its appearance in daily life. The increase in HR and its duration appear to be associated with the development of IE. The increases in sympathetic activity in the morning and the increase in myocardial oxygen demand accompanied by physical activity in the afternoon most likely contributed to the circadian variation in the incidence of ischemic episodes.

Activities of Daily Living↗
PubMed1996

Angiogenesis. Angiogenic therapy using fibroblast growth factors and vascular endothelial growth factors for ischemic vascular lesions.

Angiogenic therapy using fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) is being developed as a novel therapeutic strategy to obtain restoration of blood flow around the ischemia in cases of ischemic cardiovascular disease. In addition, arterial gene therapy through gene transfer by VEGF genes has now reached the stage of clinical application. Through in vivo animal experiments to determine the angiogenic effects of FGF and VEGF, we hope to obtain clues concerning the clinical applications of these methods. Methods-1: Twenty-three adult dogs were divided into 3 groups as follows: Group A-1: 20 micrograms of bFGF was administered intravenously simultaneously with heparin three times per week in 4 dogs. Group A-2: 20 micrograms of bFGF was administered intravenously three times a week without heparin in 4 dogs. Group B: 20 micrograms of bFGF was administered intramuscularly three times per week in 5 dogs. Group C: Sham operation control group consisting of 10 dogs. Local ischemia was created in the hind limbs of animals in groups A-1, A-2 and B through ligation of the femoral artery. Selective femoral arteriography was performed immediately after ligation at 1 week and 2 weeks postoperatively. Biopsy was also performed either at 1 week or 2 weeks after ligation. Results-1: (1) The percent increase in number of collateral vessels of the ischemic zone, as recognized on arteriography, was greater in the bFGF groups compared to group C. (2) The increase in collateral vessels peaked at 1 week. (3) No difference in angiogenic effect was observed in relation to the method of administration. (4) The combined administration of heparin had no angiogenic effect. (5) The hemoglobin content of the biopsy specimens was significantly greater in the 3 groups receiving bFGF compared to group C. Methods-2: The same study was performed using VEGF as detailed in Method-1. Results-2: As in the first experiment, a significant increase in collateral vessels was seen in the VEGF group compared to the control group. Both exogenous bFGF and VEGF significantly promote collateral vessel development and appear to be effective novel therapeutic agents for the treatment of ischemic disease.

Angiography↗
PubMed1996

Abnormalities of T waves in effort angina pectoris patients at rest evaluated by spatial velocity electrocardiogram.

The normal shape of the T wave on the standard 12-lead electrocardiogram (ECG) is asymmetrical. The spatial velocity electrocardiogram (SVECG) is a method of recording the slope of the wave of the ECG and makes it possible to quantify the symmetry of the ECG-T wave. The aim of this study was to diagnose resting effort angina pectoris not detectable by conventional resting ECG using SVECG. We studied SVECG-T waves in effort angina pectoris patients with significant coronary artery stenosis but with normal resting ECG (AP group: 50 subjects) and in an age- and sex-matched normal controls (N group: 30 subjects). The SVECG is depicted as a simple differential wave, and all SVECG-T waves had two peaks. The first peak of the SVECG-T wave was designated as the 'a' wave and the second peak as the 'c' wave. The heights (a wave-mag, c wave-mag) and c wave-mag/a wave-mag ratio (c/a ratio) were calculated. The c/a ratio was significantly decreased in the AP group (1.52 +/- 0.29 vs 1.87 +/- 0.27, p < 0.0001). In cases below the cut off c/a ratio of 1.7, the diagnostic sensitivity, specificity and accuracy for effort angina pectoris were retrospectively evaluated to be 82%, 70% and 78%, respectively. The heights of the 'a' and 'c' waves correspond to the maximum slope of the ascending and descending limbs of the T wave on ECG. The symmetrization of the T wave on ECG is considered to occur when the c/a ratio decreases and approaches 1.0. In conclusion, the c/a ratio of the SVECG-T wave is a useful index to diagnose effort angina pectoris at rest when the resting ECG is normal.

Aged↗
PubMed1995

Underestimation of vasodilator effects of nitroglycerin by upper limb blood pressure.

To determine why upper limb blood pressure measurement underestimates the vasodilator effects of nitroglycerin on lowering ascending aortic systolic pressure, we studied 24 patients (58 +/- 11 years, mean +/- SD). Ascending aortic pressure and radial artery pulse calibrated by cuff blood pressure measurement at the brachial artery were recorded simultaneously before and 5 minutes after sublingual administration of 0.3 mg nitroglycerin. Waves were analyzed by a signal processor, and the fourth derivative wave was used to find the early (S1) and late (S2) systolic shoulders (S1 corresponds to the second zero crossing and S2 to the third zero crossing). Before nitroglycerin administration, maximal systolic pressure in the ascending aorta (141 +/- 21 mm Hg) coincided with the late systolic peak in all patients, and in most patients (21 of 24) maximal systolic pressure in the radial artery (140 +/- 19 mm Hg) coincided with the early systolic peak. Maximal systolic pressure decreased more in the ascending aorta than in the radial artery (22 +/- 13 and 11 +/- 11 mm Hg, respectively; P < .001). However, the reduction in the shoulder of late systolic pressure in the radial artery (24 +/- 13 mm Hg) clearly indicated the reduction in maximal systolic pressure (late systolic peak) in the ascending aorta. The augmentation index of the ratio of the height of late systolic pressure to early systolic pressure fell proportionally (r = .74, P < .001) in the radial artery (from 0.88 +/- 0.13 to 0.60 +/- 0.11) and in the ascending aorta (from 1.57 +/- 0.25 to 1.26 +/- 0.24), which indicated the reduction in late systolic pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

[Electrocardiographic characteristics of patients with left circumflex-related myocardial infarction in the acute phase without tented T waves or definite ST elevation].

Acute myocardial infarction (AMI) causing ST depression and T wave inversion has been diagnosed as subendocardial or non-Q myocardial infarction. However, some patients eventually develop strictly posterior infarction with a lesion of the left circumflex coronary artery (LCX). This study attempted to determine the electrocardiographic (ECG) characteristics of such myocardial infarction in 32 patients with definite AMI in whom ECG showed no hyperacute T waves or ST elevation and the LCX was an infarct-related coronary artery. ECG on admission (< 6 hours from the onset), at 24 hours, and on the 14th day were analyzed to evaluate QRS, ST, T, and U waves using calipers and magnifying lens. Sixty-six patients with normal circulation served as controls. The characteristic ECG findings on admission were ST depression in chest leads, and prominent positive U waves in leads V2 or V3 with relatively small T waves. Based on these results we proposed new ECG criteria: 1) ST depression > or = 0.1 mV in 2 consecutive chest leads, 2) prominent positive U wave > or = 0.1 mV in leads V2 or V3, 3) T/U ratio in leads V2 or V3 < or = 4. Considering two of the above criteria as positive, the sensitivity was 71.9%, the specificity 97.0%, and the diagnostic accuracy 88.8%. In 85.2% of the patients, ST depression returned to the baseline by 24 hours. As the amplitude of the U waves decrease gradually, the T/U ratio increased. The R/S ratio in leads V1 or V2 became > or = 1 by 24 hours in 46.4% and the amplitude of R wave in lead V1 increased gradually. T waves in the right precordial leads increased with time. These findings were consistent with isolated strictly posterior myocardial infarction. From these results we identified new ECG criteria: 1) R/S ratio in leads V1 or V2 > or = 1, 2) R wave > or = 0.7 mV in lead V1, 3) T wave > or = 0.5 mV in lead V1. Considering any of the above criteria as positive, the sensitivity was 72.0%, the specificity 87.9%, and the diagnostic accuracy 86.7% on the 14th day. These new ECG criteria of strictly posterior myocardial infarction with the LCX as an infarct-related coronary artery apply at less than 6 hours or at 24 hours from the onset of the symptoms.

Aged↗
PubMed1994

Heart rate variability before the occurrence of silent myocardial ischemia during ambulatory monitoring.

Thirty-three ischemic episodes in 19 patients with stable coronary artery disease were studied to clarify changing autonomic nervous system activity during daily life before the occurrence of myocardial ischemia. Nonischemic points were studied for comparison of control data with ischemic episodes. These were defined as (1) patient showing no ischemic ST-T change while having the same heart rate with onset of ischemic episodes, and (2) presence within 1 to 2 hours before or after onset of ischemic episodes in the same patient. We analyzed heart rate (HR) variability during the 30-minute period before the onset and after the end of ischemic episodes during 24-hour monitoring. The period of 30 to 40 minutes before ischemia was regarded as the baseline, and HR variability was analyzed at 10-minute intervals before each ischemic episode and nonischemic point. HR variability was quantified on the band of 2 components: low frequency (0.04 to 0.15 Hz; LF) and high frequency (0.15 to 0.40 Hz; HF). Of the 33 episodes, 24 (73%) had a greater LF/HF value during the 30-minute period before ischemia than that before the nonischemic points. Distribution of the number of the 24 episodes demonstrated circadian rhythm with a peak from 8 to 10 A.M. HF power began to decrease from the last 10 minutes before ischemia, compared with baseline. A significant decrease in HF power with a background of greater value of LF/HF may explain the reduced ischemic threshold for ischemia during daily life.

Aged↗
PubMed1994

A case of creatine kinase isomer anomaly in relation to the diagnosis of acute myocardial infarction.

Creatine kinase (CK) isomers have recently been suggested to be of value in the diagnosis of acute myocardial infarction (AMI). The aim of this report was to determine whether measurement of CK isomers, especially the MM isomer and the cardio-specific marker MB isomer, is practical in the diagnosis of AMI. A 64-year-old female with consistently high values for total CK showed an electrophoretic pattern which suggested AMI. We ruled out all possible causes of increased CK, and its MB isomer, including IgGBB, beta-LP (lipoprotein) and mitochondrial complexes as well as myocarditis, muscular disorders, and myoglobinuria. Regardless of the source of the anomaly, the fact remains that CK macroanomaly cases can be an obstacle in the diagnosis of AMI. CK isomers have proven to be accurate markers in AMI and valuable in doubtful cases, such as non Q-AMI. However, in light of this particular case of CK macroanomaly, isomers are not 100% accurate (specific) in the diagnosis of AMI.

Clinical Enzyme Tests↗
PubMed1994

Role of MB isoforms (isomers) in the early diagnosis of acute myocardial infarction.

In addition to electrocardiogram (ECG), analysis of creatinine phosphokinase (CPK), lactate dehydrogenase (LDH) and their isoenzymes is commonly employed to diagnose acute myocardial infarction (AMI). The aim of this study was to observe the efficiency of isomers of CPK for early diagnosis of AMI. ECG, though useful in many ways, is not 100% sensitive. The drawback involved with CPK and LDH isoenzymes is the time lag factor in diagnosing AMI early enough for interventional therapy. Recently the subunits of these isoenzymes, namely MM and now the MB isomers are being tested for their effectiveness in the early diagnosis of AMI. In our experience MB isomers were found to be accurate markers in the early diagnosis of AMI. They were especially valuable in diagnosing myocardial infarction not detectable by ECG in cases such as non-Q AMI, cardiomyopathy, and bundle branch block among other such cases.

Clinical Enzyme Tests↗
PubMed1994

[Evaluation of myocardial viability and efficacy of reperfusion therapy by dual-SPECT using 99mTc-PYP and 201Tl in acute myocardial infarction].

UNLABELLED: Dual SPECT using 99mTc-PYP and 201Tl was performed in 70 patients with acute myocardial infarction, and the ratio of overlap zone between 201Tl and 99mTc-PYP uptake in the infarcted area was determined (the Y-ratio). The Y-ratio was significantly higher in the group with redistribution in the infarcted area on exercise thallium myocardial scintigraphy in the chronic stage of infarction, as well as in the group with normal left ventricular wall motion. Thus, the Y-ratio value was apparently useful in the evaluation of myocardial viability. Patients from 60% of the Y-ratio upward are suggested that myocardial viability had been survived. When the Y-ratio was determined in 30 patients who underwent early reperfusion therapy (ICT or direct-PTCA), no significant difference was found between the ICT group and the direct-PTCA group. However, the Y-ratio was significantly higher when reperfusion was performed within 6 hours than when it was performed after 6 hours, and a significant positive correlation (r = 0.63, p < 0.01), was found between reperfusion time from cardiac event within 9 hours and the value of (100--the Y-ratio). CONCLUSION: The Y-ratio was grateful appeared to be useful for the quantitative evaluation of myocardial viability in the acute stage of myocardial infarction. In addition, it appears to be important to perform reperfusion as soon as possible to improve myocardial salvage.

Adult↗
PubMed1993

The prognostic significance of exercise-induced silent ST-segment depression in patients after myocardial infarction.

To evaluate the prognostic value of exercise-induced silent ST-segment depression, 157 patients who had suffered myocardial infarction underwent symptom-limited exercise testing and coronary angiography. Patients were divided into 3 groups according to the presence or absence of ischemic ST-segment depression and angina during exercise testing. Group A patients had ST-segment depression without angina. Group B patients had both ST-segment depression and angina. Group C patients had neither ST-segment depression nor angina. All patients were followed without coronary artery bypass graft or percutaneous transluminal coronary angioplasty for an average of 36 months and the frequency of coronary events (cardiac death, recurrent myocardial infarction and unstable angina pectoris) was compared. Group A patients had less severe coronary artery disease, greater coronary reserve during exercise and exercised longer than group B. However, the prognosis of group A was similar to group B, and was worse than group C. Using the Cox proportional hazards model, ischemic ST-segment depression was the most useful index for predicting future coronary events among the baseline values, coronary angiographic and exercise testing variables. However, angina during exercise testing was not an independent predictor. Thus, post-infarction patients showing exercise-induced ST-segment depression should be treated carefully regardless of the presence or absence of angina.

Adult↗