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Biomedical subjects

Fumihiko Miyake

Publications and source records attributed to Fumihiko Miyake.

36 records · Page 2Linked to original sources
PubMed2003

Experimental study on the effectiveness and safety of radiofrequency catheter ablation with the cooled ablation system.

Experimental in vitro and in vivo studies were performed to assess the effectiveness and safety of the cooled-tip catheter and the Cooled Ablation System, which enables the creation of deeper and wider burn lesions in the myocardial tissue using radiofrequency current. This system was confirmed to consistently create large burns by cooling the catheter tip with circulating water within the catheter, even under unfavorable conditions. On the other hand, unfavorable effects, as a result of over burning, such as explosive vaporization within the tissue (the 'pop' phenomenon), tissue carbonization, coronary artery injury and lung injury were identified. 'Pop' was difficult to predict, but it is important to know how it can be avoided. No 'Pop' was seen without first observing an impedance decrease, thus it was considered safe to decrease the radiofrequency current if the impedance began to decrease. This system will be very effective for ablation of refractory arrhythmias, such as ventricular tachycardia or atrial flutter, but it is recommended that only experienced electrophysiologists use this system to avoid serious complications.

Animals↗
PubMed2003

Health-related quality of life of Japanese patients with chronic heart failure: assessment using the Medical Outcome Study Short Form 36.

Chronic heart failure is characterized by impaired cardiac function, but the relationship between clinical indices and subjective perception is not clear. This study was undertaken to investigate the relationship between cardiac function, exercise capacity and clinical classification, and the health-related quality of life (HRQOL) in 91 outpatients with an left ventricular ejection fraction (LVEF) less than 40%. Exercise capacity was evaluated by the Specific Activity Scale, and HRQOL by the Medical Outcome Study Short Form 36. Exercise capacity and the cardiothoracic ratio were correlated with the HRQOL related to physical functioning, although the correlation between exercise capacity and mental health was not significant. LVEF was not related to HRQOL. Factor analysis revealed (1) LVEF was independent of physical functioning; (2) physical function and exercise capacity comprise a factor reflecting physical HRQOL; and (3) socio-emotional functioning is the third factor independent of LVEF and physical function. Physical and socio-mental HRQOL measurement included information independent of the widely used clinical indices such as LVEF and New York Heart Association classification. The evaluation of HRQOL should be included in the assessment of patient status.

Aged↗
PubMed2003

Autonomic imbalance as a property of symptomatic Brugada syndrome.

The autonomic properties in 27 patients with the electrocardiographic morphology of Brugada syndrome were investigated using 24-h Holter monitoring: 10 patients had a history of ventricular fibrillation (VF; Br-VF group) and 17 did not (Br-N group); there were 26 healthy subjects enrolled in this study. All subjects underwent normal Holter data monitoring and power spectral analysis. Few extrasystoles were observed in either group, and the mean heart rate (HR), maximum HR, and total heart beats over 24 h were obtained. All of these measurements were significantly lower in the Br-VF group than in the Br-N and healthy subject groups. The RR interval variability was analyzed over 512 beats every 10 min. The high-frequency component (0.15-0.40 Hz; HF), low-frequency component (0.04-0.15 Hz; LF) and the LF/HF ratio were analyzed over 24 h. The HF was significantly higher and LF/HF ratio lower in the Br-VF group than in the healthy subjects. The HF was also significantly higher than in the Br-N group. During the night (00.00-05.00 h), the HF was significantly higher in the Br-VF group, and the LH/HF lower. During the day (12.00-17.00 h), the HF was significantly higher in the Br-VF group, but there was no difference in the LF/HF. These results indicate that high vagal tone and low sympathetic tone are specific properties of symptomatic Brugada syndrome.

Autonomic Nervous System Diseases↗
PubMed2003

Impaired chronotropic response to exercise in acute myocardial infarction patients with type 2 diabetes mellitus.

This study was undertaken in acute myocardial infarction (AMI) patients with non-insulin-dependent diabetes mellitus (type 2 DM) to investigate their impaired chronotropic response to exercise. Seventy-one AMI subjects entered the study, 30 with type 2 DM and 41 age- and body mass index-matched non-DM (control) patients. One month after the onset of AMI, these patients underwent cardiopulmonary exercise testing on a treadmill under a ramp protocol. Anaerobic threshold (AT) and peak oxygen uptake (peak VO2) were determined as indicators of exercise capacity. Plasma norepinephrine (NE) concentration was measured in blood samples obtained at 2 time points: during pre-exercise rest and immediately after peak exercise. The change in NE concentration during exercise, as an index of sympathetic nervous activity, was calculated as a percentage: deltaNE = [(NE during exercise) - (resting value)]/(resting value) x 100. The change in heart rate (HR) during exercise was calculated as a simple difference: deltaHR = [(peak HR) - (rest HR)]. Index of chronotropic response to exercise was then quantified as the deltaHR/deltaNE during exercise. No significant intergroup differences in ejection fraction at rest or HR at peak exercise were observed. However, VO2 at AT, peak VO2, deltaHR, and deltaHR/deltaNE were significantly lower in the type 2 DM group than in the non-DM group. DeltaHR correlated with VO2 at AT (r = 0.49, P<0.001) and with peak VO2 (r = 0.53, P<0.001) in all subjects. Also, deltaHR/deltaNE correlated with VO2 at AT (r = 0.42, P<0.001) and with peak VO2 (r = 0.44, P<0.001) in all subjects. AMI patients with type 2 DM had impaired cardiopulmonary responses to maximal and submaximal exercise testing and impaired chronotropic response to exercise, even though their cardiac function at rest was similar to that of non-DM AMI patients. The data suggest that one mechanism of impaired cardiopulmonary response to exercise in AMI patients with type 2 DM groups is an impaired chronotropic response.

Aged↗
PubMed2003

Relationship between impaired chronotropic response, cardiac output during exercise, and exercise tolerance in patients with chronic heart failure.

The present study was undertaken to investigate the relationship between the extent of impaired chronotropic response and cardiac output during exercise, and exercise tolerance in patients with chronic heart failure. The subjects consisted of 24 patients (mean 60.1 +/- 14.0 years) who had mild chronotropic incompetence. Cardiopulmonary exercise testing was performed in all patients, and heart rate (HR), anaerobic threshold (AT), maximum oxygen uptake (peak VO2), slope of the regression line relating the ventilatory equivalent to carbon dioxide output (VE/VCO2 slope), and exercise time were measured. Cardiac output (CO) was measured by a thoracic bioimpedance method and cardiac index (CI) was calculated. Plasma norepinephrine (NE) was measured at rest and immediately after the exercise test. The changes in HR, NE, and CI from the resting state to immediately after exercise were calculated as deltaHR, deltaNE, and deltaCI, respectively. The deltaNE was converted to a logarithmic scale and deltaHR/log deltaNE was used as a parameter of HR response to sympathetic nerve stimulation. The results were as follows: HR and NE in the resting state had no correlation with AT and with peak VO2. DeltaHR/log deltaNE correlated positively with both AT and peak VO2, and negatively with the VE/CO2 slope. DeltaHR/log deltaNE correlated positively with peak CI, %deltaCI, and deltaCI/exercise time. The data suggest that one of the mechanisms of low exercise tolerance in chronic heart failure patients was due to an inadequate increase in CO response against exercise caused by an impaired HR response to increased NE.

Adult↗
PubMed2003

Reversible ischemic neurological deficit (RIND) due to exercise testing for the diagnosis of angina pectoris.

A 57 year old Japanese male with chest oppression due to exercise is presented. This symptom was likely due to effort angina pectoris. Master's double two-step test revealed ischemic ST segment depression on the electrocardiogram, thus, a Tl201 myocardial stress imaging test using a bicycle ergometer was undertaken. Immediately following the exercise test, the patient experienced dizziness and palsy in his left upper and lower limbs. Cerebral angiography demonstrated 70% stenosis at the right internal carotid artery, but no abnormal findings were demonstrated on a cranial x-ray CT scan and magnetic resonance imaging. His palsy in the left limbs completely recovered within 3 weeks. Thus this event was diagnosed as a reversible ischemic neurological deficit (RIND). Major but non-cardiogenic complications during exercise testing are very rare, and RIND has not been reported thus far to the best of our knowledge.

Angina Pectoris↗
PubMed2003

[Different effects of exercise training in patients with myocardial infarction with or without diabetes mellitus].

OBJECTIVES: This study investigated whether myocardial infarction patients with diabetes mellitus had lower heart rate reserve to exercise by measuring the increment in heart rate (HR) divided by the increment of norepinephrine (NE) concentration from rest to peak exercise (delta HR/log delta NE). The difference in exercise training effects was also investigated. METHODS: The 148 patients after myocardial infarction were divided into two groups, the DM group (n = 34) and the non-DM group (n = 114). Cardiopulmonary exercise testing was performed in each subject at 1 and 3 months after the onset. Blood samples were taken at rest and immediately after peak exercise, rest brain natriuretic peptide, rest and peak norepinephrine were analyzed. Exercise training was performed from 1 to 3 months after the onset. RESULTS: Resting heart rates were significantly higher in the DM group than in the non-DM group both at 1 and 3 months although peak heart rates were not significantly different. Peak oxygen uptake were lower in the DM group both at 1 and 3 months after onset of myocardial infarction compared to the non-DM group. End-tidal carbon dioxide pressure was lower and the rate of increase of minute ventilation to carbon dioxide output was higher in the DM group. Plasma brain natriuretic peptide was higher in the DM group. delta HR/log delta NE was 19.4 +/- 4.0 in the DM group and 22.2 +/- 5.6 in the non-DM group (p < 0.01), and increased in only the non-DM group. delta HR/log delta NE was more closely correlated with peak oxygen uptake in the DM group than in the non-DM group. CONCLUSIONS: Impaired response to exercise training may be caused, in part, by impaired heart rate reserve to exercise in patients with diabetes mellitus.

Aged↗
PubMed2003

[Development of measure for disease-specific quality of life in patients with chronic heart failure].

OBJECTIVES: To develop a measure for disease-specific health-related quality of life in patients with heart failure and examine its reliability and validity. METHODS: One hundred and four patients with stable chronic heart failure (74 males, 30 females, mean age 64.2 +/- 10.0 years) with left ventricular ejection fractions of less than 40% were enrolled in this study. Each patient responded to the Medical Outcomes Study Short Form 36 (SF-36) and a disease specific questionnaire comprising four categories (dyspnea, sleep, appetite and fatigue), each consisting of five to six questions. A stepwise exploratory factor analysis was applied to the disease-specific measure to consider categorical fitness. In 25 of the 104 patients, the data in the questionnaire were compared with peak oxygen uptake, anaerobic threshold, slope of the regression line relating the ventilatory equivalent to carbon dioxide output (VE/VCO2 slope) and peak work rate. Correlations between the questionnaire and eight components of SF-36 were evaluated. RESULTS: The appetite category proved unreliable and was excluded from consideration, so 12 questions were adopted from the other three categories. Cronbach's a values ranged from 0.68 to 0.89 and the coefficients of test-retest were from 0.84 to 0.94, so both internal consistency and reproducibility of these questions were considered excellent. The scores of three categories well reflected the severity of heart failure based in New York Heart Association functional class. The anaerobic threshold (r = 0.53), peak oxygen uptake (r = 0.66), VE/VCO2 slope (r = -0.48) and peak work rate (r = 0.41) correlated with the total score of the 12 questions. The total scores were closely correlated with the eight components of SF-36. CONCLUSIONS: This study suggests that the disease-specific questionnaire is applicable to evaluation of the health-related quality of life in patients with heart failure.

Aged↗
PubMed2002

Reversible left ventricular dysfunction "takotsubo" cardiomyopathy related to catecholamine cardiotoxicity.

An 80-year-old female was admitted for a persistent consciousness disturbance. Electrocardiography revealed ST-segment elevation in leads II, III, aVf, and V3-V6. Coronary angiography demonstrated normal arteries, while left ventriculography revealed asynergy of apical akinesis and basal hyperkinesis. The creatinine kinase and creatinine kinase MB levels were not elevated after the initial measurement on admission. The diffuse ST-segment elevation reached a maximum level 24 hours after admission. In leads V3-V6, ST-segment elevation continued for 48 hours, and was followed-up by deep inverted T waves. Within 24 days, the asynergy improved without any specific treatment, but the giant negative T waves were present on the electrocardiogram. The plasma norepinephrine and brain natriuretic peptide levels on the first hospital day were 2.9ng/mL and 906pg/mL, respectively. The left ventricular dysfunction appeared to be induced by the exposure to high-level plasma catecholamines. (123)I-metaiodobenzyl guanidine scintigraphy also revealed transient dysfunction of the cardiac catecholamine dynamics.

Aged↗
PubMed2002

Prolongation of LAS40 (duration of the low amplitude electric potential component (<40 microV) of the terminal portion of the QRS) induced by isoproterenol in 11 patients with Brugada syndrome.

The electrophysiological mechanism of Brugada syndrome is unclear, but transmural dispersion of repolarization in the right ventricle is believed to be the most likely mechanism. On the other hand, the presence of a conduction delay region is considered to be related to the occurrence of ventricular fibrillation; that is, a relationship between the presence of a ventricular late potential (LP) and arrhythmogenic right ventricular cardiomyopathy. In this study, the LP from signal-averaged electrocardiography during isoproterenol (ISP) administration in patients with Brugada syndrome is discussed. The subjects were 11 patients with Brugada syndrome and 6 healthy individuals. In all subjects, the total filtered QRS duration (fQRS), root mean square voltage of the 40 ms terminal portion of the QRS (RMS(40)), duration of the low amplitude electric potential component (40 microV) of the terminal portion of the QRS (LAS(40)), and time duration of the fQRS-LAS(40) difference were compared between when ISP was prescribed and when it was not. During ISP administration, a peculiar response, which resulted in an LAS(40) prolongation, was observed in the patients with Brugada syndrome. With ISP, the fQRS remained unchanged, but the RMS(40) and the fQRS-LAS(40) decreased. Consequently another 3 patients with a positive LP were diagnosed using the ordinary standard because of the administration of ISP. We believe that the low-amplitude component was unmasked by shortening of the high-amplitude component. In patients with Brugada syndrome, a conduction delay in the ventricle may be present and may be related to the occurrence of ventricular fibrillation.

Adult↗
PubMed2002

Clinical significance of the dispersion of the activation--recovery interval and recovery time as markers for ventricular fibrillation susceptibility in patients with Brugada syndrome.

Brugada syndrome (BS) is associated with sudden cardiac death and the markers for ventricular fibrillation (VF) remain unclear, so the activation-recovery interval (ARI) dispersion and recovery time (RT) dispersion were investigated as possible markers in 20 subjects with BS (BS group) and 22 healthy individuals (H group). The 20 BS subjects were divided into 8 cases with documented VF (BS-VF group), 3 of which had recurrences, and 12 without (BS-N group). The corrected dispersion measurements from the standard 12-lead ECG of the QT interval (QTcd), ARI (ARIcd) and RT (RTcd) were compared among the groups. There were significant differences noted between the BS-VF and BS-N groups for the ARIcd and the RTcd, but not for the QTcd. Further, there were critical differences, 150 ms(1/2), observed for the ARIcd and RTcd, and these were associated with a prolongation of the maximum ARI or RT, shortening of the minimum ARI or RT, and prolongation only of the maximum QT for the QTcd. Susceptibility to VF may be predicted by the ARIcd or RTcd in BS.

Arrhythmias, Cardiac↗
PubMed2002

Electrocardiography subtraction method of detecting low-amplitude, high-frequency components (L-HFCs) within the QRS complex of patients with ventricular tachycardia.

A new method of extracting the low-amplitude and high-frequency components (L-HFCs) was developed and this study investigated its usefulness in 86 subjects: 28 normal subjects (group 1) and 58 patients with a previous myocardial infarction (MI). The patients were classified into 3 groups: group 2 with 38 patients without ventricular tachycardia (VT), group 3 with 13 patients with non-sustained VT, and group 4 with 7 patients with sustained VT. The new electrocardiography (ECG) subtraction method, using a mathematical filtering procedure, was used instead of conventional complex filtering. The continuous L-HFCs within the QRS complex were analyzed using a Z-lead recording. The duration of the continuous L-HFCs was significantly longer in group 4 than in groups 1 (p<0.0001), 2 (p<0.0001) or 3 (p<0.05) with all 3 filters. The ECG subtraction method is a powerful and useful new technique for identifying patients at risk for either sustained or non-sustained VT after MI, and overcomes several of the problems with the conventional signal-averaging method.

Adult↗
PubMed2002

Relationship between infarction location and size to QT dispersion in patients with chronic myocardial infarction.

The relationship between the location and size of an infarction and QT dispersion was investigated in 84 Japanese patients with chronic myocardial infarction (54 with anteroseptal infarction and 30 with inferior infarction). The control group consisted of 23 subjects without ischemic heart disease (13 normal subjects and 10 hypertensive patients). Corrected QT dispersion (maximum corrected QT interval minus minimum corrected QT interval: QTc dispersion), was significantly larger in the anterior infarction group than in the control group (69.9+/-21.5 msec vs 53.0+/-17.6 msec), while the inferior infarction group showed no significant difference from control subjects. QTc dispersion was significantly greater in the patients with large anterior infarcts than in those with small anterior infarcts (80.5+/-20.5 msec vs 61.9+/-18.8 msec). In patients with chronic myocardial infarction, QT dispersion is influenced by the infarct location and size. Accordingly, interpretation of QT dispersion data should take these factors into consideration.

Electrocardiography↗
PubMed2002

[Von Willebrand factor-cleaving protease activity in patients of collagen disease with antiphospholipid antibodies].

Acquired thrombotic thrombocytopenic purpura (TTP), characterized by widespread thrombus formation in the microcirculation, is a ponderous complication of antiphospholipid syndrome. Recently, von Willebrand factor-cleaving protease (VWF-CPase) activity has been reported as a possible determinant for the occurrence of TTP. To clarify the role of VWF-CPase in the thrombus formation associated with antiphospholipid syndrome, we investigated plasma VWF-CPase activity in patients of collagen diseases with lupus anticoagulant (LA). Decreased plasma VWF-CPase activity less than 50% of the normal activity was observed in 25.7% (n = 18) in 70 patients with collagen diseases and 7 (10%) cases of them showed more lower VWF-CPase activity less than 25%. The IgG fractions obtained from 2 patients with the low VWF-CPase activity strongly inhibited the proteolytic reaction of normal VWF-CPase. There was no significant relationship between LA and plasma VWF-CPase activity. Thrombotic episodes, especially arterial thrombosis, were more frequently observed in LA-positive patients with low VWF-CPase activity. These results suggest that decreased activity of VWF-CPase, partly due to IgG type inhibitor to the enzyme activity may be an additional risk factor for arterial thrombosis in collagen disease patients with antiphospholipid antibodies.

ADAM Proteins↗
PubMed2002

Determination of the target ventricular rate in patients with atrial fibrillation by evaluation of ventriculoarterial coupling.

In a pilot study, we determined the target ventricular rate of patients with atrial fibrillation by evaluating their ventriculoarterial coupling. Eleven patients with atrial fibrillation were studied. We recorded M-mode echocardiograms and radial artery blood pressure simultaneously. The left ventricular end-systolic pressure-volume ratio (Emax) and effective arterial elastance (Ea) were calculated for each beat, and the relationship of the preceding R-R interval (pRR) to Emax and Ea was evaluated. There was a significant positive correlation between pRR and Emax, and a significant negative correlation between pRR and Ea in all patients. The pRR that produced maximal stroke work was determined at the point of Emax=Ea, and the pRR that achieved maximal mechanical efficiency was determined at the point of 2Ea=Emax. By evaluating ventriculoarterial coupling in these patients who had atrial fibrillation, we were able to determine that the range between the 2 pRR intervals was the range of the optimal ventricular rate. A narrower range of the 2 pRR intervals was observed in patients with dilated cardiomyopathy than in the patients with no underlying cardiac disease. We conclude that it may be possible to determine the optimal ventricular rate in patients with atrial fibrillation by evaluating ventriculoarterial coupling.

Atrial Fibrillation↗
PubMedDate not supplied

A case of lipomatous hypertrophy of the interatrial septum detected via transthoracic 2-dimensional echocardiography.

A 71-year-old woman underwent echocardiography for the evaluation of hypertensive heart disease. A 2-dimensional echocardiogram revealed an abnormal mass that protruded into the left atrium from the atrial septal side of the left atrial wall. Microscopic examination of the surgical specimen disclosed a mixture of normal-appearing fat, vesicular fat, and hypertrophied myocytes, and degenerated cardiac tissue with foci of necrotic fat tissue, consistent with lipomatous hypertrophy. Although lipomatous hypertrophy of the interatrial septum is rare, this little-known entity should be included in the differential consideration of the left atrial mass detected via echocardiographic examination, particularly in both obese and elderly patients.

Aged↗