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Biomedical subjects

H Asanoi

Publications and source records attributed to H Asanoi.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effects of water ingestion on gastric electrical activity and heart-rate variability in healthy human subjects.

Electrogastrography (EGG) is a method to record electrical activity of the stomach using cutaneous electrodes. Power ratio (PR) is one of the parameters and means the relative change of EGG power of gastric activity from before to after certain stimulations (e.g., meals, water or drugs). Autonomic nervous function is an important modulator of gastric activity, but its relation with the EGG parameters has not been well clarified. We recorded EGG and the R-R interval simultaneously both before and after drinking 150 ml water for 400 s, and spectrally analyzed them using the maximum entropy method in 12 healthy volunteers. We calculated PR from before to after water ingestion, and the power of the high-frequency component of R-R interval variability before (pre-HF) and after water ingestion (post-HF), and their ratio (rHF = post-HF/pre-HF). PR was positively correlated with rHR (r = 0.727; P < 0.05) and negatively correlated with pre-HF (r = 0.706; P < 0.05), and rHF was negatively correlated with pre-HF (r = 0.776; P < 0.05). These results suggest that simultaneous recording of EGG and ECG for frequency domain analysis is necessary to estimate the vagal nervous activity.

Adult↗
PubMed1996

Altered inotropic and lusitropic responses to heart rate in conscious dogs with tachycardia-induced heart failure.

OBJECTIVES: The effects of increasing heart rate on left ventricular contraction and relaxation were examined in conscious dogs with tachycardia-induced heart failure under autonomically blocked conditions. BACKGROUND: Previous studies using isolated myocardium have shown attenuated positive inotropic responses to stimulation frequency in heart failure. However, these responses have not been well examined in intact preparations in the presence of heart failure with autonomic system blockade, where the intrinsic ventricular responses to increasing heart rate could be revealed. METHODS: Seven dogs were instrumented with a micromanometer and a conductance volume catheter. After autonomic blockade to eliminate neural reflexes, left ventricular contractile properties were quantified by the slope of the end-systolic pressure-volume relation (ventricular elastance), and left ventricular relaxation was assessed by the time constant of isovolumetric ventricular pressure decay. RESULTS: Increasing the heart rate by 60 beats/min enhanced ventricular elastance by 71 +/- 18% (mean +/- SD) and decreased end-systolic volume by 6 +/- 5% in normal hearts. In failing hearts, ventricular elastance increased by only 21 +/- 20%, and end-systolic volume did not change appreciably. Although the reduction in left ventricular end-diastolic and minimal pressures by tachycardia was smaller in the failing heart, ventricular relaxation rate remained unaltered both in the normal heart and in the failing heart. CONCLUSIONS: Under conscious but autonomically blocked conditions, effects of increasing heart rate on the failing left ventricle are characterized by a predominant attenuation of the inotropic response rather than of the lusitropic response.

Animals↗
PubMed1996

Energetically optimal left ventricular pressure for the failing human heart.

BACKGROUND: An energy-starved failing heart would benefit from more effective transfer of the mechanical energy of ventricular contraction to blood propulsion. However, the energetically optimal loading conditions for the failing heart are difficult to establish. In the present study, we analyzed the optimal left ventricular pressure to achieve maximal mechanical efficiency of the failing heart in humans. METHODS AND RESULTS: We determined the relation between left ventricular pressure-volume area and myocardial oxygen consumption per beat (VO2), stoke work, and mechanical efficiency (stroke work/VO2) in 13 patients with different contractile states. We also calculated the optimal end-systolic pressure that would theoretically maximize mechanical efficiency for a given end-diastolic volume and contractility. Left ventricular pressure-volume loops were constructed by plotting the instantaneous left ventricular pressure against the left ventricular volume at baseline and during pressure loading. The contractile properties of the ventricle were defined by the slope of the end-systolic pressure-volume relation. In patients with less compromised ventricular function, the operating end-systolic pressure was close to the optimal pressure, achieving nearly maximal mechanical efficiency. As the heart deteriorated, however, the optimal end-systolic pressure became significantly lower than normal, whereas the actual pressure remained within the normal range. This discrepancy resulted in worsening of ventriculoarterial coupling and decreased mechanical efficiency compared with theoretically maximal efficiency. CONCLUSIONS: Homeostatic mechanisms to maintain arterial blood pressure within the normal range cause the failing heart to deviate from energetically optimal conditions.

Adult↗
PubMed1996

Vesnarinone-induced granulocytopenia: incidence in Japan and recommendations for safety.

Vesnarinone (OPC-8212) is a new positive inotropic agent that augments myocardial contractility. A recent multi-center randomized trial in the United States demonstrated that 60 mg/day of vesnarinone significantly reduced morbidity and mortality and improved quality of life in patients with symptomatic chronic heart failure. Vesnarinone, however, is also known for its propensity to cause granulocytopenia. In search of effective safety measures against this side effect, data have been collected in Japan as part of the post-marketing surveillance of this drug. This article reviews the results of this post-marketing surveillance and other works available to date, including an illustrative case report, and presents measures that should be taken with regard to safety during treatment with vesnarinone. Vesnarinone-induced granulocytopenia has appeared in relatively early stages of vesnarinone therapy, and characteristically results in a rapid decrease in granulocyte count. Hematologic monitoring should be performed at least once a week during the initial 16 weeks of vesnarinone therapy. Granulocyte colony-stimulating factor may contribute to recovery from severe granulocytopenia, although it should be used carefully because of its potential to cause adult respiratory distress syndrome.

Adult↗
PubMed1995

Loading sequence plays an important role in enhanced load sensitivity of left ventricular relaxation in conscious dogs with tachycardia-induced cardiomyopathy.

BACKGROUND: Left ventricular relaxation rate in the failing heart depends more on the systolic load than in the normal heart. To elucidate the mechanisms for the enhanced load sensitivity of left ventricular relaxation in heart failure, we examined the relative contributions of changes in end-systolic volume and loading sequence to the left ventricular relaxation rate. METHODS AND RESULTS: In seven conscious dogs, the time constant (Td) of left ventricular pressure decay, end-systolic volume, systolic circumferential force, and time to peak force during caval occlusion were compared before and after development of tachycardia-induced heart failure. Rapid ventricular pacing decreased the slope of the end-systolic pressure-volume relation from 4.5 to 2.8 mm Hg/mL (P < .01) and prolonged Td from 33 to 49 ms (P < .01). In normal conditions, caval occlusion reduced end-systolic force (-580 g, P < .01) and end-systolic volume (-7 mL, P < .01) but did not change Td or time to peak force. In heart failure, however, caval occlusion shortened Td (-11 ms, P < .01), with a concomitant decrease in the time to peak force (-30 ms, P < .01), while end-systolic volume and force declined slightly. Consequently, for a comparable reduction in end-systolic force, Td decreased more in heart failure than in normal hearts, suggesting enhanced load sensitivity. Moreover, changes in Td correlated well with those in the time to peak force (r = .79, P < .01) but not with those in end-systolic volume. CONCLUSIONS: Loading sequence rather than elastic recoil seems to play the predominant role in the enhanced load sensitivity of left ventricular relaxation in heart failure.

Animals↗
PubMed1995

Intravenous dopexamine in the treatment of acute congestive heart failure: results of a multicenter, double-blind, placebo-controlled withdrawal study.

Acute hemodynamic effects of intravenous infusion of dopexamine were evaluated by a placebo-controlled withdrawal study in patients with acute congestive heart failure. Twenty patients were enrolled at 10 centers in Japan. All patients had a pulmonary capillary or diastolic pressure of 15 mmHg or greater and a cardiac index of 2.5 l/min/m2 or less. Phase I: Intravenous dopexamine was introduced in a single-blind, uncontrolled fashion at the rate of 0.5 micrograms/kg/min and was titrated up to achieve a 30% or more increase in the cardiac index. Two patients withdrew from the study due to sinus tachycardia and ventricular ectopy or exacerbation of heart failure. Phase II: The remaining 18 responders who were free of limiting side effects were randomized in double-blind fashion to continue dopexamine or to switch to placebo for an additional 60 minutes. At the end of phase II, the hemodynamic improvement obtained in phase I of the study disappeared completely after substitution of placebo but was maintained in dopexamine-treated patients. Our findings suggest that dopexamine, when given in appropriate doses to selected patients, shows balanced vasodilator action suitable for the treatment of acute congestive heart failure.

Acute Disease↗
PubMed1995

Whole-body 201Tl scintigraphy during one-leg exercise and at rest in normal subjects: estimation of regional blood flow changes.

To determine the effect of exercise intensity on regional blood flow in exercising and resting leg muscles and organs, we assessed relative changes in the regional distribution of 201Tl during one-leg ergometer exercise and at rest by whole-body scintigraphy as an estimate of regional blood flow changes in 10 healthy males. The regional 201Tl activity was expressed as a percentage of the whole-body activity, and relative changes in each region were compared to those at the anaerobic threshold (AT) and at peak exercise. In the legs, the distribution of 201Tl in the exercising thigh and calf increased significantly at the AT to 390.7 and 219.2% respectively of resting levels (both P < 0.01), but remained unchanged the resting thigh from rest to peak exercise. Conversely its distribution in the resting calf decreased significantly at the AT to 60.0% of the resting level (P < 0.01). However, there were no significant differences between AT and peak exercise. In the organs, the distribution of 201Tl in the lung, liver, spleen and kidneys decreased significantly at the AT to 88.4 +/- 10.4%, 67.0 +/- 11.5%, 62.4 +/- 11.8% and 67.0 +/- 8.6% respectively of resting levels (all P < 0.01). Redistribution of blood flow to the exercising leg occurs predominantly during mild to moderate exercise. Therefore, blood flow in the leg during strenuous exercise depends primarily upon an increase in cardiac output. The splanchnic organs are the major sources of redistribution.

Adult↗
PubMed1994

Clinical effects of long-term administration of pimobendan in patients with moderate congestive heart failure.

The long-term efficacy of the positive inotropic and vasodilator drug, pimobendan, was assessed in 21 patients suffering from symptomatic heart failure. Patients were randomized to 16 weeks of double-blind therapy with either 2.5 or 5.0 mg/day of pimobendan (n = 10), or a matching placebo (n = 11). Patients were blinded on the study drug if their clinical status had not substantially worsened during the study. Of the placebo-treated patients, 5 patients were withdrawn from the study because of a deterioration of their heart failure, while none of the active treated group was withdrawn because of increased symptoms. Quality of life, assessed by the specific activity scale derived from the metabolic costs of individual physical activity, was 3.45 +/- 0.90 (SD) mets in the baseline state and increased significantly after week 16, averaging 5.07 +/- 1.40 and 4.67 +/- 1.47 mets at weeks 16 and 24, respectively. In the placebo-treated group, the specific activity scale was 3.27 +/- 1.21 mets at the baseline and remained unchanged throughout the study period. Patients treated with pimobendan were able to significantly increase their exercise duration. The accompanying increase in peak oxygen uptake was statistically insignificant, due to the limited number of patients enrolled in the study. These results suggest that in contrast to the recent pessimistic view of the long-term efficacy of cardiotonic drugs, pimobendan is beneficial in treating patients with congestive heart failure and may favorably modify their prognosis. Further large-scale evaluation of this agent is warranted.

Activities of Daily Living↗
PubMed1994

Neural modulation of ventriculoarterial coupling in conscious dogs.

To investigate the role of autonomic reflexes in stroke-work optimization, we studied ventriculoarterial coupling in unanesthetized dogs with the autonomic system intact and blocked. Ventricular contractility was quantified by the slope of the end-systolic pressure-volume relation, ventricular elastance (Ees). Arterial system properties were quantified by the ratio of end-systolic pressure to stroke volume, arterial elastance (Ea). The coupling between left ventricle and arterial system was expressed by the Ea-to-Ees ratio. Changes in arterial blood pressure during nitroprusside or angiotensin II infusion were used to elicit reflex-mediated influences on ventriculoarterial coupling. With the autonomic system intact, Ees doubled during nitroprusside infusion while Ea remained unchanged due to reactive vasoconstrictor forces and tachycardia. Consequently, the Ea-to-Ees ratio fell 50% from baseline. Angiotensin II infusion increased Ea 46% but did not significantly change Ees, resulting in a 26% increase in the Ea-to-Ees ratio. In contrast to ventriculoarterial coupling, stroke work was insensitive to changes in afterload, remaining close to its theoretical maximum. After autonomic blockade, Ees tended to decrease during nitroprusside and increased during angiotensin II infusion in parallel with changes in Ea, so that the Ea-to-Ees ratio did not change from baseline as much as it did with the autonomic system intact. Again, the left ventricle maintained nearly 90% of its maximal stroke work. Thus, over a wide range of afterload, stroke work was kept near its theoretical maximum, independent of autonomic neural regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1994

Importance of total leg muscle mass for exercise intolerance in chronic heart failure.

Patients with chronic heart failure symptoms tend to avoid voluntary effort and are thus subject to physical deconditioning. The presence of symptoms in daily life is thought to predispose to physical deconditioning and subsequent skeletal muscle loss. This study was designed to describe the relation among daily physical activities, skeletal muscle loss and exercise capacity in patients with chronic heart failure. We studied 14 patients with severe cardiac dysfunction (left ventricular ejection fraction < 40%) and 7 age-matched normal subjects. We measured total leg muscle mass by dual energy X-ray absorptiometry. The patients were divided into 7 asymptomatic and 7 symptomatic individuals using questionnaires for specific physical activities. Peak oxygen uptake and anaerobic threshold were significantly reduced in cardiac patients as compared with normal subjects. The reduction in exercise capacity was greater in the symptomatic patients than in asymptomatic patients. Leg muscle mass was significantly reduced (-17%) in the symptomatic patients, while it remained normal in the asymptomatic patients. Oxygen uptake in unit muscle mass at the level of anaerobic threshold and at peak exercise was decreased in both the asymptomatic (-21% and -21%, respectively) and symptomatic patients (-27% and -30%, respectively) but the difference between these two groups was not significant. In the asymptomatic patients, the reduced exercise capacity was accounted for primarily by muscle mass-independent factors such as an impaired nutritive blood flow to exercising muscles or metabolic abnormalities within the muscle cell. In the symptomatic patients, the marked reduction in exercise tolerance was attributable to a decrease in leg muscle mass and to hemodynamic or metabolic abnormalities. We conclude that the loss of leg muscle mass plays an important role in exercise intolerance in patients who are prone to physical deconditioning as a result of symptomatic heart failure.

Absorptiometry, Photon↗
PubMed1994

Disparate inotropic and lusitropic responses to pimobendan in conscious dogs with tachycardia-induced heart failure.

Left ventricular (LV) inotropic and lusitropic responses to a calcium sensitizer, pimobendan, were compared between normal and failing hearts. Heart failure was induced by rapid ventricular pacing in 6 dogs instrumented with a micromanometer and a conductance catheter. The effects of pimobendan were evaluated in the conscious state before and after development of heart failure. Pimobendan dose-dependently increased the slope of the end-systolic pressure-volume (P-V) relation (Ees) in both normal and failing hearts, whereas its magnitude was markedly attenuated in failing hearts. Heart rate (HR) was increased by pimobendan in normal heart but did not change in failing heart. LV relaxation, assessed by peak -dP/dt and the time constant of isovolumic pressure decay (Td), was substantially improved to the same extent in failing and normal hearts. Consequently, Ees and Td exhibited a hyperbolic relation over a wide range of contractility states. In normal heart, pimobendan caused a leftward shift of the diastolic P-V relation while maintaining a similar curve. In failing heart, however, this relation shifted directly downward with a concomitant increase in end-diastolic volume, indicating a reduction in the constraints on LV distention and a resultant increase in preload reserve. Thus, pimobendan accelerated LV isovolumic relaxation and improved distensibility in conscious dogs with tachycardia-induced heart failure despite the marked attenuation of inotropic responses.

Animals↗
PubMed1993

Limited value of anaerobic threshold for assessing functional capacity in patients with heart failure.

Exercise tolerance was assessed in 146 patients with cardiac dysfunction in terms of anaerobic threshold (ATge). Patients were divided into four classes according to the peak oxygen uptake: Class A (72 patients) exceeding 1000 ml/min; Class B (27 patients) 800-999 ml/min; Class C (37 patients) 500-799 ml/min; and Class D (10 patients) below 500 ml/min. An incidence of the ATge breakpoint was lower in patients of Class C (38%) than in those of either Class B (70%, p < 0.05) or Class A (87%, p < 0.05). The ATge could not be determined in any patients in Class D. The V-slope method improved the ability to determine ATge by 20%. In Classes C and D, ATge detection was precluded considerably by the fact that the initial workloads of exercise test involved oxygen uptake levels already close to or above the ATge. An oscillatory hyperventilation pattern was also significantly related to failure in defining ATge in Class C patients. Of the 51 patients whose ATge was undetermined, 9 had an atrial septal defect. In two of these, exercise-induced right-to-left shunting led to progressive arterial hypoxemia, and the consequent hyperventilation masked the appearance of ATge. Thus, ATge is virtually undetectable in patients with severe heart failure largely because of the early onset of anaerobic metabolism or abnormal ventilatory responses to exercise. Accordingly, the clinical application of ATge in the assessment of functional capacity would be limited to patients with mild to moderate heart failure.

Adult↗
PubMed1993

Importance of abnormal lung perfusion in excessive exercise ventilation in chronic heart failure.

Whether excessive ventilatory response to exercise is related to the maldistribution of pulmonary blood flow was examined in 23 patients with chronic heart failure and nine age-matched normal subjects. With the use of technetium 99m macroaggregated albumin, the resting distribution of pulmonary blood flow was assessed by the scintigraphic counts ratio of upper to lower lung fields. The ventilatory response to exercise was assessed by the slope of the relationship between minute ventilation and carbon dioxide production during exercise. Eight patients (group A) had slope less than 33, the upper limit of the normal range, and 15 patients had slope of 33 or greater (group B). In group B pulmonary blood flow was distributed more to the upper lung, which made the counts ratio (60%) higher than in normal subjects (34%) or in patients in group A (38%). There was no significant difference in pulmonary flow distribution between normal subjects and patients in group A. In group B tidal volume did not increase during exercise as much as it did in normal subjects and in patients in group A; therefore, the respiratory pattern was rapid and shallow. Although the ratio of physiologic dead space to tidal volume fell by 20% during exercise in normal subjects and by 23% in patients in group A, it failed to decrease in patients in group B (-1%), which indicates a relative increase in dead space respiration during exercise. These data indicate that decreased lung compliance and regional ventilation-perfusion mismatch caused by pulmonary vascular and parenchymal abnormalities would play an important role in the excessive exercise ventilation in chronic heart failure.

Exercise Test↗
PubMed1993

Importance of non-stenosed donor coronary arteries for collateral flow reserve.

To elucidate whether the presence of significant stenoses in donor coronary arteries compromises collateral flow reserve, coronary arteriography was performed in 22 patients with stable effort angina who had a complete obstruction in one of the major coronary arteries. The patients were divided into two groups according to the absence (group I: n = 11) or presence (group II: n = 11) of significant stenoses (> or = 75% stenosis of the luminal diameter) in donor arteries. After conventional cardiac catheterization, coronary arteriography was repeated before and during rapid atrial pacing. Coronary collateral circulation was evaluated by means of angiographic contrast appearance time (CAT) which was defined as the time (s) until the epicardial segments distal to the site of complete occlusion were opacified after the injection of contrast medium into the donor artery. The pressure gradient across the collateral circulation (mean aortic pressure minus left ventricular end-diastolic pressure) remained unchanged before and during rapid atrial pacing (group I: 95 +/- 14 vs. 99 +/- 15 mmHg; group II: 91 +/- 18 vs. 94 +/- 16 mmHg). Rapid atrial pacing decreased the contrast appearance time in group I from 1.73 +/- 0.34 to 1.47 +/- 0.37 s (P < 0.01), but was not changed in group II from 1.68 +/- 0.36 to 1.73 +/- 0.51 s (P = n.s.). It was concluded that coronary collateral circulation is further augmented in response to an increase in myocardial oxygen demand in patients with non-stenosed donor coronary arteries and significant stenoses in donor arteries compromise an increase in collateral blood flow.

Aged↗
PubMed1993

Augmentation of smoking cessation education by urinary cotinine measurement.

Monitoring the current smoking status by an objective method may augment the effects of smoking cessation instruction. To quantitatively evaluate smoking status and its modification by smoking cessation instruction, urinary cotinine, a major metabolite of nicotine, was measured by radioimmunoassay in 64 patients with a smoking habit before and during smoking cessation instruction. Urinary cotinine levels were used to discriminate between smokers and nonsmokers (with 50 ng/ml used as a threshold). In 49 patients who claimed to have stopped smoking, urinary cotinine concentrations 1 month after instruction indicated that only 30 (61%) of them had actually stopped (before: 243 +/- 104, after: 1 +/- 3 ng/ml) (mean +/- standard deviation). In the remaining 15 patients who failed to stop smoking while reporting a reduction of cigarette consumption (before: 27 +/- 12, after: 7 +/- 5/day), there was no appreciable reduction in urinary cotinine levels (before: 298 +/- 140, after: 229 +/- 171 ng/ml). When the patients who had failed to stop smoking again received intensive smoking cessation instruction, the success rate increased from 47% (30/64) to 69% (44/64) (p < 0.05). Thus, urinary cotinine measurement may provide a useful and quantitative method for monitoring actual smoking habits and thus augment the efficacy of smoking cessation educational programs.

Cotinine↗
PubMed1992

Ventriculoarterial coupling during exercise in normal human subjects.

To examine the relative roles of ventricular contractility and loading conditions for cardiovascular adjustment during exercise, 10 normal human subjects were studied using a framework of ventriculoarterial coupling. Anaerobic threshold was evaluated to determine the work rates of aerobic and anaerobic exercise. Ventricular contractile properties were quantified by the slope of the end-systolic pressure-volume relationship (ventricular elastance) and arterial system properties were expressed by the end-systolic pressure-stroke volume relationship (arterial elastance). During aerobic exercise, left ventricular end-diastolic volume and stroke volume were increased by 14 and 33%, with plasma norepinephrine levels being doubled. Arterial elastance was reduced by 30%, but ventricular elastance did not change significantly. During anaerobic exercise, ventricular end-diastolic volume returned to the resting value, while stroke volume remained increased by 31%. In contrast to aerobic exercise, ventricular elastance rose substantially by 89% in association with about a 10 times increase in plasma norepinephrine. Arterial elastance remained the same as in aerobic exercise. Thus, the increase in stroke volume was primarily mediated by changes in loading conditions during aerobic exercise and by enhanced contractility during anaerobic exercise.

Adult↗