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Biomedical subjects

J Hayano

Publications and source records attributed to J Hayano.

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

The relationship between R amplitude in lead V5 (RV5) and left ventricular mass in the groups of adolescent subjects classified by body composition.

How the amplitude of the R wave in lead V5 (RV5) of the ECG represents the left ventricular (LV) mass was investigated in 894 students aged 15 (boys: 545, girls: 349). The influence of body composition [ie, percentage of body fat (%fat)] was taken into consideration. A significant correlation was found between RV5 amplitude and LV mass for both genders. However, the relationship was stronger for boys than for girls. The students were then divided into 3 groups; that is, those at either the top or bottom 10th percentile (low or high-fat range) and the rest of the students (middle-fat range), depending on the % fat calculated by the bioelectrical impedance method. The significant correlation between RV5 and LV mass was found only for the 2 groups of boys whose percentage fat was in the low or middle-fat range. The correlation coefficients were 0.40 and 0.34, respectively. Moreover, in the boys' low-fat range, the RV5 of students whose LV mass was large (> or =90th percentile), was significantly higher (p<0.01) than in the other ranges. Setting a particular cutoff point of RV5 in the low-fat range of boys improved sensitivity as well as specificity (20-30% better among all boys) for detecting large LV mass. These observations suggest that classification of subjects by body composition could be improve the reliability of ECG assessment for left ventricular hypertrophy, although the gender and number of subjects in whom improvement is expected are limited.

Adolescent↗
PubMed1997

Coronary disease-prone behavior among Japanese men: job-centered lifestyle and social dominance. Type A Behavior Pattern Conference.

In Japan the type A behavior pattern, particularly its component of hostility, is known to have less value as a risk for coronary artery disease (CAD) than in the United States. We developed a questionnaire (Japanese Coronary-prone Behavior Scale [JCBS]) to investigate the behavioral correlates with CAD among contemporary Japanese persons. The JCBS was administered to 419 Japanese men undergoing coronary angiography; 310 of them had angiographic or clinical evidence or both of CAD, and 109 had no evidence of CAD. The group with CAD had more coronary risk factors than the group without CAD, but the two groups did not differ in type A behavior pattern as assessed with the Jenkins Activity Survey. Stepwise discriminant analysis, in which standard coronary risk factors were forced into the model, revealed that inclusion of nine JCBS items (scale C) in the model resulted in the best discrimination between the two groups. Cross-validation results showed that the error-rate estimates for the discriminant models that consisted only of standard coronary risk factors, only of scale C items, and of their combination were 34.7, 32.4, and 27.0%, respectively. The scale C items represented a job-centered lifestyle, social dominance, and suppressed overt type A behaviors. These results indicate that an independent behavior pattern prone to CAD is discernible among Japanese men and suggest that the behavior pattern may contain characteristics that can be differentiated from those that constitute the type A behavior pattern.

Aged↗
PubMed1997

Stability over time of circadian rhythm of variability of heart rate in patients with stable coronary artery disease.

Reproducibility of circadian rhythm of variability in heart rate was studied in 40 patients with stable coronary artery disease who underwent 48-hour ambulatory electrocardiographic recordings at baseline (time 1) and after 4 months (time 2). The standard deviation of the R-R interval and the low-frequency (0.04 to 0.15 Hz) and high-frequency (0.15 to 0.45 Hz) components of variability in heart rate were assessed every 5 minutes. In 35 patients a significant circadian rhythm was observed at both time 1 and time 2 in the standard deviation of the R-R interval, with the acrophase occurring at around 5:00 AM, in the high-frequency amplitude with the acrophase around 3:00 AM, and in the low-frequency/high-frequency ratio with the acrophase around noon. In these patients, parameters of circadian rhythm (mesor, amplitude, and acrophase) showed good within-individual reproducibility with an intraclass correlation coefficient of 0.63 to 0.95 (p < 0.001 for all). In the patients who showed inconsistency about the significance of circadian rhythm between time 1 or time 2, the amplitude of circadian rhythm, even if significant, was found in the lowest five values in the distribution. We conclude that the circadian rhythms of cardiac autonomic activity are stable over time within individual patients with stable coronary artery disease.

Adult↗
PubMed1997

Spectral characteristics of ventricular response to atrial fibrillation.

To investigate the spectral characteristics of the fluctuation in ventricular response during atrial fibrillation (AF), R-R interval time series obtained from ambulatory electrocardiograms were analyzed in 45 patients with chronic AF and in 30 age-matched healthy subjects with normal sinus rhythm (SR). Although the 24-h R-R interval spectrum during SR showed a 1/f noise-like downsloping linear pattern when plotted as log power against log frequency, the spectrum during AF showed an angular shape with a breakpoint at a frequency of 0.005 +/- 0.002 Hz, by which the spectrum was separated into long-term and short-term components with different spectral characteristics. The short-term component showed a white noise-like flat spectrum with a spectral exponent (absolute value of the regression slope) of 0.05 +/- 0.08 and an intercept at 10(-2) Hz of 4.9 +/- 0.3 log(ms2/Hz). The long-term component had a 1/f noise-like spectrum with a spectral exponent of 1.26 +/- 0.40 and an intercept at 10(-4) Hz of 7.0 +/- 0.3 log(ms2/Hz), which did not differ significantly from those for the spectrum during SR in the same frequency range [spectral exponent, 1.36 +/- 0.06; intercept at 10(-4) Hz, 7.1 +/- 0.3 log(ms2/Hz)]. The R-R intervals during AF may be a sequence of uncorrelated values over the short term (within several minutes). Over the longer term, however, the R-R interval fluctuation shows the long-range negative correlation suggestive of underlying regulatory processes, and spectral characteristics indistinguishable from those for SR suggest that the long-term fluctuations during AF and SR may originate from similar dynamics of the cardiovascular regulatory systems.

Adult↗
PubMed1996

Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency.

BACKGROUND: The primary mechanisms of respiratory sinus arrhythmia (RSA) are understood to be the modulation of cardiac vagal efferent activity by the central respiratory drive and the lung inflation reflex, and the degree of RSA increases with cardiac vagal activity. However, it is unclear whether RSA serves an active physiological role or merely reflects a passive cardiovascular response to respiratory input. We hypothesized that RSA benefits pulmonary gas exchange by matching perfusion to ventilation within each respiratory cycle. METHODS AND RESULTS: In seven anesthetized dogs, a model stimulating RSA was made. After elimination of endogenous autonomic activities, respiration-linked heartbeat fluctuations were generated by electrical stimulation of the right cervical vagus during negative pressure ventilation produced by phrenic nerve stimulation (diaphragm pacing). The vagal stimulation was performed in three conditions; phasic stimulation during expiration (artificial RSA) and during inspiration (inverse RSA) and constant stimulation (control) causing the same number of heartbeats per minute as the phasic stimulations. Although tidal volume, cardiac output, and arterial blood pressure were unchanged, artificial RSA decreased the ratio of physiological dead space to tidal volume (VD/VT) and the fraction of intrapulmonary shunt (Qap/Qt) by 10% and 51%, respectively, and increased O2 consumption by 4% compared with control. Conversely, reverse RSA increased VD/VT and Qap/Qt by 14% and 64%, respectively, and decreased O2 consumption by 14%. CONCLUSIONS: These results support our hypothesis that RSA benefits the pulmonary gas exchange and may improve the energy efficiency of pulmonary circulation by "saving heartbeats."

Animals↗
PubMed1996

Autonomic dysfunction in hemodialysis patients with persistent hypotension.

To investigate autonomic mechanisms underlying persistent hypotension in long-term hemodialysis patients, high-frequency (HF, > 0.15 Hz) and low-frequency (LF, 0.04-0.15 Hz) components of heart rate variability and plasma noradrenaline were analyzed in 10 persistently hypotensive hemodialysis patients (group H), 11 normotensive patients (group N) and 10 healthy controls (group C). The HF amplitude, an index of cardiac parasympathetic activity, and LF-to-HF ratio, an index of sympathetic predominance, were in the order of groups C > N > H (p < 0.01). While the HF amplitude decreased with standing in all three groups (p < 0.05 for all), the LF-to-HF ratio increased only in groups N and C (p < 0.05 for both) but not in group H. Conversely, plasma noradrenaline level was in the order of groups C < N < H (p < 0.001). Furthermore, while the LF-to-HF ratio correlated positively with the plasma noradrenaline level in group C (r = 0.73, p < 0.01), it correlated negatively in group H (r = 0.69, p < 0.05). These results indicate that an impairment in both parasympathetic and sympathetic functions exists in hemodialysis patients with persistent hypotension, and that the apparent sympathetic dysfunction could result from a reduction in cardiovascular responsiveness to sympathetic stimulation.

Adrenergic Fibers↗
PubMed1996

Association between type A behavior pattern and coronary artery spasm in Japanese patients.

The relations between the Jenkins Activity Survey (JAS) Type A score and coronary atherosclerosis and spasm were examined in 192 patients (115 men and 77 women) undergoing coronary angiography. Thirty-nine men (34%) and 12 women (16%) had significant (>or=75%) coronary stenosis. In 97 patients (54 men and 43 women) with no significant coronary stenosis, a coronary spasm provocation test by 0.2 to 0.4 mg of ergometrine was performed, by which a significant focal spasm (>or=75% reduction of luminal diameter) was induced in 22 men (40%) and 5 women (12%). Men who showed a significant focal spasm had a higher Type A score than men who showed no such spasm (1.9 +/- 8.4 vs. -2.4 x 8.3, p < 0.05). Discriminant analysis in male patients revealed that the induction of coronary spasm can be predicted by the JAS Type A score and smoking habit (p = 0.04). No such association was found for female patients. These results suggest that the Type A behavior pattern as assessed by the JAS may be associated with coronary spasm in Japanese men without significant coronary stenosis.

Journal Article↗
PubMed1995

Assessment of autonomic function in myotonic dystrophy by spectral analysis of heart-rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart-rate variability (HRV) of 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and sex-matched healthy, sedentary humans (control) at rest in the supine position. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead electrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency component (a marker of sympathetic and vagal modulation of heart rate) and that of the high-frequency component (a marker of vagal modulation of heart rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest that the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform daily activities. Therefore, one must give careful consideration to the cardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.

Adult↗
PubMed1995

Assessment of autonomic function in traumatic quadriplegic and paraplegic patients by spectral analysis of heart rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart rate variability (HRV) of quadriplegic and paraplegic male subjects at rest in the supine position. In agreement with our previous study, in nine of 15 quadriplegic patients only the high-frequency (HF: center frequency = respiratory frequency) component (a marker of vagal modulation of heart rate) was observed. In contrast, in six of the quadriplegic patients both the HF component and the low-frequency (LF: center frequency at approx. 0.1 Hz, 0.03-0.15 Hz in this study) component (a marker of sympathetic and vagal modulation of heart rate) were observed. However, in six quadriplegic patients who presented the LF component, (i) the center frequency of the LF component was lower than that in 10 healthy, sedentary, age-matched males (control I) (P < 0.01), (ii) the power of the HF component was smaller than that in the control-I group (P < 0.01) and (iii) the LF/HF power ratio (an index of sympathovagal balance) was larger than that in the control-I group (P < 0.05). On the other hand, in nine paraplegic patients with an intact 1st-4th thoracic spinal cord, from which the cardiac sympathetic nerves originate, the total power, the power of the LF component and that of the HF component were smaller than those in nine healthy, sedentary, age-matched males (control II) (P < 0.05, P < 0.01 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

'Non-hypotensive' hypovolaemia reduces ascending aortic dimensions in humans.

1. The notion that small, 'non-hypotensive' reductions of effective blood volume alter neither arterial pressure nor arterial baroreceptor activity is pervasive in the experimental literature. We tested two hypotheses: (a) that minute arterial pressure and cardiac autonomic outflow changes during hypovolaemia induced by lower body suction in humans are masked by alterations in breathing, and (b) that evidence for arterial baroreflex engagement might be obtained from measurements of thoracic aorta dimensions. 2. In two studies, responses to graded lower body suction at 0 (control), 5, 10, 15, 20 and 40 mmHg were examined in twelve and ten healthy young men, respectively. In the first, arterial pressure (photoplethysmograph), R-R interval, and respiratory sinus arrhythmia amplitude (complex demodulation) were measured during uncontrolled and controlled breathing (constant breathing frequency and tidal volume). In the second, cross-sectional areas of the ascending thoracic aorta were calculated from nuclear magnetic resonance images. 3. Lower body suction with controlled breathing resulted in an increased arterial pulse pressure at mild levels (5-20 mmHg; ANOVA, P < 0.05) and a decreased arterial pulse pressure at moderate levels (40 mmHg; ANOVA, P < 0.05). Both R-R intervals and respiratory sinus arrhythmia were negatively related to lower body suction level, whether group averages (general linear regression, r > 0.92) or individual subjects (orthogonal polynomials, 12 of 12 subjects) were assessed. 4. Aortic pulse area decreased progressively and significantly during mild lower body suction, with 47% of the total decline occurring by 5 mmHg. 5. These results suggest that small reductions of effective blood volume reduce aortic baroreceptive areas and trigger haemodynamic adjustments which are so efficient that alterations in arterial pressure escape detection by conventional means.

Adult↗
PubMed1995

Heart rate and blood pressure variabilities during graded head-up tilt.

We investigated the responses of the frequency components of heart rate (HR) and blood pressure (BP) variabilities to progressive changes in autonomic activity induced by the graded head-up tilt technique in 12 normal subjects (age 19-27 yr) under the condition of frequency-controlled respiration (0.25 Hz). During low-level tilt (0-30 degrees), the R-R interval was unchanged and the amplitude of the high-frequency (HF; 0.25 Hz) component of HR variability showed only a slight insignificant decrease. The amplitude of the low-frequency (LF; 0.04-0.15 Hz) component of HR variability increased progressively as the angle increased (P < 0.05). During high-level tilt (30-90 degrees), the R-R interval and the HF amplitude of HR variability decreased progressively with tilt angle (P < 0.001 for both). The LF amplitude of HR variability peaked at a tilt angle of 30 degrees. The LF-to-HF ratio of HR variability and the LF amplitude of systolic and diastolic BP variabilities increased progressively as the tilt angle increased from 0 to 60 degrees (P < 0.001), although systolic and diastolic BPs were unchanged. These results suggest that mixed autonomic responses to orthostatic stress, which are thought to be mediated by both cardiopulmonary and arterial baroreflex mechanisms, can be distinguished by changes in the frequency components of HR and BP variabilities.

Adult↗
PubMed1995

Lesser vagal withdrawal during isometric exercise with age.

The tachycardia that accompanies isometric exercise decreases with age in humans; however, the mechanism of this decline is unknown. To determine whether less cardiac vagal withdrawal is associated with the age-related decrease in this response, we assessed high-frequency R-R interval variability (0.15-0.40 Hz), an index of cardiac vagal tone, before (control) and during isometric exercise to exhaustion in healthy young (21-29 yr; n = 12) and older (61-72 yr; n = 11) men. During control, the two groups did not differ in respiratory rate, mean arterial pressure, or heart rate, although the older subjects had a lower high-frequency amplitude (12.2 +/- 1.1 vs. 29.4 +/- 4.6 ms/Hz; P < 0.05). During isometric exercise, the respiratory rate and arterial pressure responses did not differ; however, the older men had a lower absolute heart rate and a smaller increase in heart rate, and only the young men demonstrated a significant decline in high-frequency amplitude. The heart rate responses to exercise were correlated with the declines in high-frequency amplitude (initial, r = -0.808; midpoint, r = -0.714; peak, r = -0.632; all P < 0.005), which were, in turn, correlated with the control high-frequency amplitude (initial, r = -0.727; midpoint, r = -0.643; peak, r = -0.610; all P < 0.01). Thus smaller declines in high-frequency amplitude, related to lower baseline amplitude, corresponded to smaller increases in heart rate throughout isometric exercise. Therefore, we conclude that the smaller tachycardiac response to isometric exercise in older humans is associated with an inability to decrease cardiac vagal tone below an already reduced baseline level.

Adult↗
PubMed1994

Effect of relaxation training on cardiac parasympathetic tone.

To examine the hypothesis that the relaxation response is associated with an increase in cardiac parasympathetic tone, the frequency components of heart rate variability during relaxation training were investigated in 16 college students. Electrocardiograms and pneumograms were recorded during a 5-min baseline period followed by three successive 5-min sessions of the autogenic training (relaxation) or by the same periods of quiet rest (control), while subjects breathed synchronously with a visual pacemaker (0.25 Hz). Although neither the magnitude nor the frequency of respiration showed a significant difference between relaxation and control, the amplitude of the high-frequency component of heart rate variability increased only during relaxation (p = .008). There was no significant difference in the ratio of the low-frequency (0.04-0.15 Hz) to the high-frequency amplitudes. The increased high-frequency amplitude without changes in the respiratory parameters indicates enhanced cardiac parasympathetic tone. Thus, our results support the initial hypothesis of this study. Enhanced cardiac parasympathetic tone may explain an important mechanism underlying the beneficial effect of the relaxation response.

Adult↗
PubMed1994

Effects of respiratory interval on vagal modulation of heart rate.

To determine whether paced breathing (PB) and respiratory interval of PB modify the relationship between spectral components of heart rate variability (HRV) and cardiac vagal tone, we studied seven healthy young males under the condition of beta-adrenergic blockade by intravenous propranolol (0.2 mg/kg). Compared with spontaneous breathing, PB at the same respiratory interval as that of individual spontaneous breathing showed no significant effect on the amplitude of the high-frequency (HF) component or the mean R-R interval in either the supine or tilt position, whereas the PB decreased the amplitude of the low-frequency (LF; 0.04-0.15 Hz) component in both positions (P = 0.004 and 0.042, respectively). When the respiratory interval was increased from 3 to 6 s, the HF amplitude showed a progressive increase in both positions (P = 0.001 and 0.035, respectively), while the LF amplitude and mean R-R interval remained unchanged. These results indicate that the effects of PB and respiratory interval on the spectral components of HRV are not mediated by the changes in mean cardiac vagal tone and support the hypothesis that increased respiratory interval amplifies the respiratory-related vagal modulation of heart rate.

Adrenergic beta-Antagonists↗
PubMed1994

Assessment of frequency shifts in R-R interval variability and respiration with complex demodulation.

A complex demodulation (CDM) method for continuous assessment of frequency shifts and time-dependent changes in amplitude in the rhythmic components existing in predefined frequency bands was proposed and applied to the analysis of high-frequency (HF) and low-frequency (LF) components of the R-R interval and to the analysis of respiration via impedance spirogram. Simulation studies revealed that this CDM technique furnishes mathematical features well suited to the investigation of non-stationary R-R interval signals and can delineate time-dependent fluctuations in both amplitude and frequency, accurately differentiating between HF and LF components. Analysis of data during paced breathing at different respiratory frequencies revealed that the estimated frequency of the HF component and respiration faithfully reflected the frequency of paced breathing. Analysis of data during dynamic exercise with increasing workload (20 W/min) showed that the frequency of the HF component was elevated with exercise and that both HF and LF amplitudes were reduced progressively with advancing load. CDM-derived frequency and amplitude of respiration were highly correlated to direct breath-by-breath respiratory frequency and tidal volume measurements. We conclude that this method could provide a powerful means for continuously assessing time-dependent changes in both cardiovascular and respiratory variations.

Adult↗
PubMed1994

[Periodical blood pressure variation during cardiopulmonary bypass--effects of cervicothoracic epidural anesthesia and phentolamine].

We studied the effects of cervicothoracic epidural anesthesia or intravenous phentolamine on periodical blood pressure variation during cardiopulmonary bypass in 12 adult patients undergoing open heart surgery under fentanyl anesthesia. Spontaneous periodical fluctuation of the blood pressure was analyzed by means of autoregressive power spectrum method. Amplitudes of the low frequency (0.02-0.15 Hz) component of the blood pressure variation amplitudes were calculated. The amplitudes decreased significantly 10 minutes after cervicothoracic epidural block with 15 ml of 2% lidocaine solution (P < 0.05), and after infusion of 0.4 mg.kg-1 of phentolamine (P < 0.05). Since amplitudes of the blood pressure variation were reduced by adequate epidural block or phentolamine, they are likely to reflect sympathetic vasomotor activity.

Adult↗
PubMed1993

Relation of cardiovascular responses to mental stress and cardiac vagal activity in coronary artery disease.

Forty-six patients with documented coronary artery disease were studied to examine the relation of cardiovascular reactivity to mental stress and cardiac vagal activity. Cardiac vagal activity was measured by means of frequency-domain analysis of heart rate variability with 48-hour out-of-hospital Holter monitoring. The amplitude of the high-frequency component (0.16 to 0.40 Hz) of heart rate variability is considered to be an index of cardiac vagal activity. Cardiovascular reactivity was measured in the laboratory during a 3-minute public speaking task. Results revealed that (1) the amplitude of the high-frequency component was significantly higher during sleep (24.6 +/- 11.3 ms) than during waking (18.2 +/- 8.0 ms) (p = 0.002); (2) compared to subjects with low diastolic blood pressure reactivity, those who displayed high diastolic blood pressure reactivity exhibited a significantly lower amplitude of the high-frequency component (19.2 +/- 6.9 vs 23.4 +/- 9.6 ms, p = 0.03). These results indicate that decreased cardiac vagal activity may contribute to the exaggerated diastolic blood pressure reactivity to mental stress in patients with coronary artery disease.

Aged↗