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K Sunagawa

Publications and source records attributed to K Sunagawa.

At least 127 records · Page 7Linked to original sources
PubMed1990

A new method to identify dynamic transduction properties of aortic baroreceptors.

We identified, in 17 alpha-chloralose-anesthetized rabbits, the dynamic transduction characteristics of the aortic arch baroreceptors using a "white-noise technique." We recorded aortic pressure and aortic depressor nerve activity while perturbing pressure by rapid, intermittent ventricular pacing (400 beats/min). Dividing the cross-power spectrum between nerve activity and pressure by the power spectrum of pressure yielded the transfer function. The gain of the transfer function increased threefold as the frequency increased from 0.005 to 5 Hz, suggesting that the baroreceptors responded primarily to dynamic rather than to static changes in pressure. To quantify the nonlinear properties of baroreceptor transduction, we compared measured instantaneous nerve activity with that linearly predicted. We demonstrated that the major nonlinearity was attributable to "threshold". The overall baroreceptor transduction properties could be represented by a cascade connection of a linear subsystem followed by a nonlinear subsystem with threshold. The white-noise technique made it possible to identify the unbiased linear properties in a nonlinear system, and thus was very useful in identifying complex biological systems.

Animals↗
PubMed1990

Effects of left heart bypass on right ventricular performance. Evaluation of the right ventricular end-systolic and end-diastolic pressure-volume relation in the in situ normal canine heart.

Although left heart bypass has gained popularity as a powerful technique to assist the severely failed left heart, apparent right heart failure has often developed during the bypass procedure. We investigated whether the coexisting right heart failure is attributable to the left heart bypass in 16 open-chest dogs. We evaluated the effects of left heart bypass on the right ventricular systolic properties by the slope of the end-systolic pressure-volume relation and its effects on the diastolic properties by chamber compliance. Overall right ventricular performance was assessed by the end-diastolic pressure versus cardiac output relationship. The left heart bypass decreased the slope slightly when the assisted flow ratio exceeded 75% (-14% +/- 8% at the assisted flow ratio of 100%, p less than 0.02) and thus had a deleterious influence on right ventricular performance. The left heart bypass, on the other hand, had a counteracting beneficial influence on right ventricular performance through the increase in chamber compliance (38% +/- 5%, p less than 0.01) and the decrease in pulmonary arterial input resistance (-15% +/- 12%, p less than 0.01). The net effect of the left heart bypass was the increase in cardiac output (20% +/- 2%, p less than 0.05) for any given right ventricular end-diastolic pressure. We conclude that in normal hearts the left heart bypass augments right ventricular performance. We ascribe these beneficial effects to diastolic ventricular interdependence and afterload unloading.

Animals↗
PubMed1989

[Bacteriological, pharmacokinetic and clinical studies on clarithromycin in the pediatric field. Pediatric Study Group of Clarithromycin].

Clarithromycin (TE-031, A-56268), a new macrolide antibiotic agent, was evaluated bacteriologically and clinically for its efficacy and safety in pediatrics by a study group organized with pediatricians from all over the country. A summary of the results of the evaluation is as follows. 1. Absorption and excretion Pharmacokinetics of TE-031 was examined by single oral administration of 10% granules and 50 mg tablets at doses of 1, 5, 10 and 15 mg/kg. There were no significant differences between 10% granules and 50 mg tablets, and between administrations before and after meal. Peaks and half-life periods of blood level of TE-031 given once at doses of 5, 10 and 15 mg/kg (10% granules) before meal were 1.58, 4.37 and 3.79 micrograms/ml, and 2.53, 3.17 and 2.20 hours, respectively, and the urinary excretion in 6 hours after the administration were about 20-30%. 2. Antibacterial effects TE-031 was proved to have excellent antibacterial effect, i.e., inhibiting growth over 80% of strains of Streptococcus pneumoniae and Streptococcus pyogenes at 0.10 micrograms/ml, Branhamella catarrhalis at 0.39 micrograms/ml, and Campylobacter jejuni at 0.78 micrograms/ml. Against Staphylococcus aureus, TE-031 showed very similar activity spectrum to EM, and EM resistant strains were also resistant to TE-031. 3. Clinical results A total of 764 cases was studied. Clinical effects of TE-031 were evaluated in 717 cases out of the 764, excluding drop-outs and cases which did not meet specified protocols. Clinically, efficacies of TE-031 were "excellent" in 265 cases and "good" in 161 cases out of 453 cases of Group A in which causal agents were identified, with an efficacy rate of 94.0%, and out of 264 cases of Group B in which pathogens were not detected, clinical effects of TE-031 were "excellent" in 115 cases and "good" in 124 cases, with an efficacy rate of 90.5%. In terms of clinical effects of TE-031 classified by diseases when Group A and B were combined, efficacy rates were 91.6% for upper respiratory tract infection (217/237), 90.0% for bacterial pneumonia (108/120), 97.4% for Mycoplasma pneumonia (111/114), 100% for Chlamydia pneumonia (4/4), 85.0% for pertussis (34/40), 100% for scarlet fever (16/16), 83.9% for skin and soft tissue infection (26/31), and 98.9% for Campylobacter enteritis (87/88).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

[Embolization of the lumbar artery for pelvic fracture].

Bleeding from the lumbar artery could be a major source of hemorrhage in a patient with massive blood loss associated with pelvic fracture. Embolization of injured lumbar artery should be attempted since hemorrhaging from the lumbar artery could be a cause of potentially life-threatening retroperitoneal hemorrhage. Selective lumbar arteriography is often helpful to diagnose bleeding from a lumbar artery, which is occasionally overlooked in pelvic aortography. We have not experienced any complications from using gelatin sponge (Gelfoam) cubes, cut into 1-2 mm pieces, for embolization of the bleeding artery.

Abdominal Muscles↗
PubMed1989

[Electrophysiologic and histopathologic investigations in children with idiopathic ventricular arrhythmias].

Between April 1984 and December 1987, electrophysiological studies and endomyocardial biopsy were performed in 14 pediatric patients, aged from 7 to 15 years, with idiopathic ventricular arrhythmias in whom diagnostic evaluation had revealed no structural heart disease. They were 8 boys and 6 girls. Cardiac catheterization revealed regional wall motion abnormalities of the left ventricle in 3 patients, one of whom showed decreased ejection fraction (EF). Electrophysiologic examination showed sinus node dysfunction in 21%. AV nodal dysfunction in 14% and dual AV nodal pathway in 21%. Histopathologic examination by endomyocardial biopsy showed myocellular hypertrophy, degeneration of myocytes, interstitial fibrosis and endomyocardial thickness in 86%, 36%, 35% and 14%, respectively. Since idiopathic ventricular arrhythmias in pediatric age group included relatively high electrophysiologic and histopathologic abnormalities, which were suggestive of occult myocardial disease and might be the early stage of cardiomyopathy, careful follow-up should be required.

Adolescent↗
PubMed1988

Effect of afterload resistance on end-systolic pressure-thickness relationship.

The influence of afterload resistance on the end-systolic pressure-thickness relationship (ESPTR) was assessed in six isolated canine left ventricles made to eject into a simulated arterial system. An increase of simulated peripheral resistance from 1.5 to 6.0 mmHg.s.ml-1 resulted in a modest but significant shift of the ESPTR upward and to the right, indicating augmented contractile performance. A relationship between the extent of systolic wall thickening and end-systolic performance was also observed: increased wall thickening impairing and decreased wall thickening enhancing end-systolic performance. The dependence of end-systolic performance on wall thickening history in this setting is consistent with shortening deactivation. This phenomenon appears to account at least in part for the observed shift in the ESPTR with altered afterload resistance.

Animals↗
PubMed1988

Random exercise stress test in diagnosing effort angina.

To improve the performance of exercise stress testing in the diagnosis of effort angina while minimizing risks of serious complications, we evaluated an impulse response of ST changes, which is a transient ST response resulting from a hypothetical, strenuous-impulselike exercise, without actually imposing the strenuous load. To obtain the impulse response, subjects walked intermittently according to a computer-generated random binary sequence on a treadmill for 20 minutes (with a constant speed of 1.7 mph and a slope of 10%). We used Fourier transform for beat-to-beat changes in ST level and the binary sequence of exercise. We then determined the transfer function by taking the ratio of Fourier transformed ST level to exercise over the frequency range of 0.5 through 5.0 cycles/min. Converting the transfer function to the time domain yielded the impulse response of ST change. The subjects consisted of 49 patients (60 +/- 9 years) with effort angina, 13 patients with atypical chest pain (56 +/- 9 years), and 30 healthy, male volunteers (23 +/- 7 years). In 82 subjects (89%), the ST impulse response showed an initial depression followed by a smooth, gradual restoration toward the preexercise ST level (type I response). The average duration of the initial depression was 8 +/- 3 seconds in the healthy volunteers, whereas it was significantly prolonged to 23 +/- 14 seconds in effort angina (p less than 0.05). The depression in patients with atypical chest pain was not significantly different from that in the healthy volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Ventricular systolic interdependence: volume elastance model in isolated canine hearts.

To analyze the interaction between the right and left ventricle, we developed a model that consists of three functional elastic compartments (left ventricular free wall, septal, and right ventricular free wall compartments). Using 10 isolated blood-perfused canine hearts, we determined the end-systolic volume elastance of each of these three compartments. The functional septum was by far stiffer for either direction [47.2 +/- 7.2 (SE) mmHg/ml when pushed from left ventricle and 44.6 +/- 6.8 when pushed from right ventricle] than ventricular free walls [6.8 +/- 0.9 mmHg/ml for left ventricle and 2.9 +/- 0.2 for right ventricle]. The model prediction that right-to-left ventricular interaction (GRL) would be about twice as large as left-to-right interaction (GLR) was tested by direct measurement of changes in isovolumic peak pressure in one ventricle while the systolic pressure of the contralateral ventricle was varied. GRL thus measured was about twice GLR (0.146 +/- 0.003 vs. 0.08 +/- 0.001). In a separate protocol the end-systolic pressure-volume relationship (ESPVR) of each ventricle was measured while the contralateral ventricle was alternatively empty and while systolic pressure was maintained at a fixed value. The cross-talk gain was derived by dividing the amount of upward shift of the ESPVR by the systolic pressure difference in the other ventricle. Again GRL measured about twice GLR (0.126 +/- 0.002 vs. 0.065 +/- 0.008). There was no statistical difference between the gains determined by each of the three methods (predicted from the compartment elastances, measured directly, or calculated from shifts in the ESPVR). We conclude that systolic cross-talk gain was twice as large from right to left as from left to right and that the three-compartment volume elastance model is a powerful concept in interpreting ventricular cross talk.

Algorithms↗
PubMed1987

Comparative influence of load versus inotropic states on indexes of ventricular contractility: experimental and theoretical analysis based on pressure-volume relationships.

We examined the quantitative influence of carefully controlled alterations in end-diastolic volume and afterload resistance on multiple simultaneously determined ejection and isovolumetric phase indexes of left ventricular contractile function in 23 isolated supported canine ventricles. The influence of load change on each index was compared with its sensitivity to inotropic stimulation, and this sensitivity was in turn contrasted to the response of the end-systolic pressure-volume relationship (ESPVR). Experimental data demonstrated various degrees of load sensitivity among the indexes, with a generally curvilinear relationship between load and index response for both preload and afterload alterations. The curvilinear nature of these relationships meant that over a select range of loading, many indexes demonstrated relative load independence. They also often displayed greater sensitivity to inotropic change than the ESPVR, and both factors help explain their enduring clinical utility. To further explore the influence of load and contractile state on several of the indexes, we developed a theoretical analysis, using variables common to pressure-volume relationships, in which these dependencies could be derived. The theoretical models fit very well with the experimental data, and reaffirmed the frequently curvilinear nature of the relationships. We conclude that while many clinical indexes of ventricular contractile function show significant load dependence, the information they provide can be reasonably interpreted within defined ranges of load and inotropic alteration. Any advantage of the ESPVR will derive not from the magnitude of its response to inotropic change, which is smaller than most other indexes, but from its relative insensitivity to load alteration over a wider range of load.

Animals↗
PubMed1987

Instantaneous pressure-volume relation of the ejecting canine left atrium.

To characterize the pump function of the left atrium, we determined the instantaneous pressure-volume relation of the isolated supported left atrium. A physiologic after-loading system for the low-pressure atrium was created by coupling it to a real-time computer-simulated ventricle and a simulated venous impedance network via a volume servo-pump. In 10 atria loaded with such systems, multiple isochronal sets of pressure-volume data were collected from many ejecting or isovolumic contractions obtained under a constant inotropic state, and the time-varying elastance, E(t), as well as the volume-axis intercepts, VO(t), were calculated. E(t) is the ensemble of slopes, and VO(t), the volume-axis intercepts resulting from the linear regression of instantaneous pressure on instantaneous volume at multiple instants throughout the cardiac cycle. The systolic portion of the left atrial E(t) was insensitive to loading conditions, as was VO(t), which, in addition, proved to be similar to the right atrial and right ventricular VO(t) waveforms in its time dependence. These results indicate that E(t) and VO(t) adequately represent the instantaneous pressure-volume relation of the left atrium in systole irrespective of the mode of contraction. Whatever the underlying mechanism might be, the load insensitivity and similarity of the basic shape of the left atrial E(t) among different atria suggests that the characterization reflects fundamental features of left atrial contraction.

Animals↗
PubMed1985

Stroke volume effect of changing arterial input impedance over selected frequency ranges.

We investigated the effect of changing arterial input impedance over three selected frequency ranges on stroke volume (SV) in nine isolated canine left ventricles. The input impedance was simulated with a three-element Windkessel model (i.e., resistance, characteristic impedance, and compliance) and was imposed on the ventricles with a servo-controlled loading system. Under a constant end-diastolic volume [33.1 +/- 1.5 (SE) ml], we changed the modulus of the afterloaded impedance over a low frequency range (below 0.13 Hz) by changing the resistance, over a transitional frequency range (in which the impedance modulus decreases from total resistance to characteristic impedance) by changing the compliance, and over a high frequency range (above 2.0 Hz) by changing the characteristic impedance. Each of the impedance components was changed from control to 50 and 200% of control. SV sensitively decreased from 16.1 +/- 0.7 to 7.4 +/- 0.5 ml in response to the increase in the low-frequency impedance modulus. SV was relatively insensitive, however, to the same percent increase in the impedance modulus over the transitional frequency range (from 11.2 +/- 0.6 to 12.3 +/- 0.7 ml) and over the high frequency range (from 11.9 +/- 0.6 to 11.6 +/- 0.7 ml). The average relative sensitivities of SV to the increase and decrease in impedance moduli in these frequency ranges were 1.2:0.12:0.04. We conclude that the modulus of impedance in the low frequency range is, by far, a more important determinant of SV than those in the transitional and high frequency ranges.

Animals↗
PubMed1985

Alternating contractility in pulsus alternans studied in the isolated canine heart.

We examined pulsus alternans in seven isolated, perfused canine left ventricles ejecting into a simulated arterial impedance. Left ventricular pressure-volume loops were measured during pulsus alternans while filing-source pressure was lowered. In all cases two distinct linear end-systolic pressure-volume relationships (ESPVRs) were noted for the strong and weak beats. The slopes of the ESPVRs of the strong beats were significantly greater than those of the weak beats (mean difference 0.9 +/- 0.6 mm Hg/ml, p less than .01), while the intercepts were not significantly different (mean difference 0.06 +/- 0.5 ml). Diastolic pressure-volume relationships for the strong and weak beats were not significantly different, excluding incomplete relaxation as a cause of pulsus alternans. Although the weak beats had both a smaller preceding end-diastolic volume and a larger end-systolic volume, the presence of two distinct ESPVRS for the strong and weak beats shows there is alternating ventricular chamber contractility in pulsus alternans that is not solely due to the Starling mechanism. The magnitude of alternation in pump function parameters such as pressure and stroke volume during pulsus alternans reflects the complex interactions of alternating contractile state with alternations in preload and afterload.

Animals↗
PubMed1985

Effect of heart rate on the canine end-systolic pressure-volume relationship.

Although the rate dependence of isolated muscle contractility is well known, the ventricular end-systolic pressure-volume relationship (ESPVR) has been reported to be insensitive to heart rate. To resolve this contradiction, we used an isolated, ejecting canine heart preparation perfused at a constant coronary arterial pressure. Heart rate was changed from 60 to 200 beats/min in steps of 20 beats/min. At least 10 pressure-volume loops under different filling pressures were obtained at each heart rate in each of six hearts. Over a heart rate range from 60 to 120 beats/min, the slope of the ESPVR (Ees) increased significantly from 3.5 +/- 0.4 (SE) to 5.3 +/- 0.6 mm Hg/ml. In the range between 120 and 180 beats/min there was little change in Ees (5.3 +/- 0.6 to 5.4 +/- 0.6 mm Hg/ml), but at 200 beats/min Ees increased slightly to 5.7 +/- 0.5 mm Hg/ml. The volume axis intercept (V0) of the ESPVR changed little over the range of heart rate from 60 to 160 beats/min (10.2 +/- 2 ml to 9.4 +/- 1.3 ml) but increased to 15.2 +/- 1.2 ml at a rate of 200 beats/min. The change in ESPVR with increase in heart rate from 60 to 120 beats/min (i.e., increase in Ees without change in V0) is the same as those seen with a positive inotropic intervention with calcium or cathecholamines, whereas the V0 changes over the range from 160 to 200 beats/min is similar to those seen with regional ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Optimal arterial resistance for the maximal stroke work studied in isolated canine left ventricle.

In a previous analysis of ventricular arterial interaction (Sunagawa et al., 1983), we represented the left ventricle as an elastic chamber which periodically increases its volume elastance to a value equal to the slope of the linear end-systolic pressure-volume relationship. Similarly, the arterial load property was represented by an effective elastance which is the slope of the arterial end-systolic pressure-stroke volume relationship. Since the maximal transfer of potential energy from one elastic chamber to another occurs when they have equal elastance, we hypothesized that the left ventricle would do maximal external work if the ventricular elastance and the effective arterial elastance were equal. We tested this hypothesis in 10 isolated canine left ventricles, ejecting into a simulated arterial impedance, by extensively altering arterial resistance and finding the optimal resistance that maximized left ventricular stroke work under various combinations of end-diastolic volume, contractility, heart rate, and arterial compliance. Each of these parameters was set at one of three levels while others were at control. The optimal resistance varied only slightly with arterial compliance, whereas it varied widely with contractility and heart rate. We thus determined that the ratio of the optimal effective arterial elastance to the given ventricular elastance remained nearly unity. This result supports the hypothesis that the left ventricle does maximal external work to the arterial load when the ventricular and arterial elastances are equalized.

Animals↗
PubMed1985

Roles of coronary circulation as a determinant of the left ventriculo-arterial interaction.

We investigated how coronary circulation influences the ventriculo-arterial interaction. For the quantitative analysis of this interaction, we proposed a simple framework where both ventricular property and vascular property were expressed as the end-systolic pressure-volume relationship. Combining this analysis with experimental data indicated the interactive nature of ventricular function that varied with loading condition through coronary circulation. Effects of regional ischemia on the ventriculo-arterial interaction was also analyzed. The loading condition insensitivity, simplicity and adequacy of the end-systolic pressure-volume relationship of ventricle made it possible to analytically couple the ventricle with arterial system providing a useful view in understanding the complex hydraulic interaction between the ventricle and arterial system.

Atrial Function↗
PubMed1984

Ventricular interaction with the loading system.

The purpose of this investigation was to develop a theoretical framework to predict stroke volume (and therefore cardiac output) when the ventricle is coupled with the arterial impedance. The ultimate objective is to arrive at an analytical description of cardiac output in the closed hydraulic loop of the entire circulatory system on the basis of the properties of the major system components. We developed the framework of analysis of ventriculo-arterial coupling by characterizing both the ventricle and arterial system in terms of the end-systolic pressure vs. stroke volume (Pes-SV) relationships. This approach, motivated by the load-insensitivity of ventricular end-systolic pressure-volume relationship (ESPVR), yielded stroke volume as the intersection between the ventricular Pes-SV relationship and arterial Pes-SV relationship. The theoretical outcome was validated by comparing the stroke volume predicted as a result of interaction between a given ventricular ESPVR and a set of arterial impedances against those SVs actually measured by imposing the same arterial impedance on the isolated canine ventricles. Furthermore, because of the mathematical simplicity of this approach, it enabled us to describe cardiac output in the closed circulatory loop with a small set of analytical equations. We conclude that the proposed framework is useful in analyzing the ventriculo-arterial coupling and various mechanisms which affect cardiac output in the closed circulatory loop.

Arteries↗