Junichi Kikuchi

Modification of Human Left Ventricular Relaxation by Small-Amplitude, Phase-Controlled Mechanical Vibration on the Chest Wall

BACKGROUND Direct clinical manipulation to improve an impairment of left ventricular (LV) relaxation has not been reported. We investigated whether the LV relaxation rate in humans could be modulated by phase-controlled mechanical vibration applied to the patients anterior chest wall and whether there are some quantitative differences in the responses of normal (N), hypertrophied (H), and failing (F) ventricle. METHODS AND RESULTS In 46 patients (N, 10; H, 18 [hypertrophic cardiomyopathy]; F, 18 [heart failure]), the vibrator was attached to the precordium and a 50-Hz, 2-mm sinusoidal mechanical vibration was applied, with the timing restricted from the onset of isovolumic relaxation to end-diastole during cardiac catheterization. Heart rate and peak LV pressure showed no difference with vibration. However, in all patients, precordial vibration caused an acceleration of the LV pressure fall. The magnitude of the induced reduction of the time constant of LV pressure decay (delta T) was larger (P < .01) in H and F than in N (4.6 +/- 2.3, 4.0 +/- 1.6, and 0.6 +/- 1.5 ms for H, F, and N, respectively). Delta T correlated strongly with the magnitude of impaired relaxation and the magnitude of transmitted vibration to the ventricle. CONCLUSIONS Phase-controlled, small-amplitude vibration on the chest wall can directly modulate LV relaxation rate, especially in those with hypertrophy or failing ventricle.

Diastolic vibration improves systolic function in cases of incomplete relaxation.

BackgroundIncomplete relaxation of the left ventricle (LV) affects LV filling, but the subsequent effect on LV systolic function remains unclear. We attempted to improve relaxation by applying oscillatory mechanical perturbation during diastole (diastolic vibration) and examined the extent to which systolic function improved. Methods and ResultsUsing 10 open-chest canine preparations, pacing tachycardia and administration of propranolol were imposed to induce various levels of incomplete relaxation. Myocardial length perturbation was induced with an oscillator attached to the LV surface (50 Hz, 1-mm amplitude) and was restricted to the period from the beginning of isovolumic relaxation to end diastole. At resting heart rates, diastolic vibration caused an immediate decrease in the time constant (T) of LV pressure fall without any influence on heart rate, LV peak systolic pressure (peak LVP), stroke volume (SV), LV peak positive dP/dt, and total systemic vascular resistance. With pacing tachycardia, diastolic vibration increased both peak LVP and SV at 160 beats per minute (before) and 120 beats per minute (after propranolol), simultaneously decreasing both T and LV diastolic pressures and increasing end-diastolic segment length. The increase in peak LVP and SV caused by diastolic vibration correlated with the T/diastolic interval (r=0.82), the assumed index of severity of incomplete relaxation. ConclusionsThese results suggest that diastolic vibration accelerates the LV relaxation rate and that this increased relaxation improves systolic function through the Frank-Starling mechanism.

A new approach to time dependent AR modeling of signals and its application to analysis of the fourth heart sound

The authors present a method for estimating spectrum transition between short-length signals of succeeding frames in low-SNR cases when the transition pattern is complex and/or there are large differences in the transition patterns among the individual sets of multiframe signals. The present approach uses a linear algorithm without any basic functions. Instead, the authors use the spectrum transition constraint, and the singular value decomposition. (SVD)-based technique is applied to obtain more accurate estimates. For the analysis of multiframe signals of the fourth heart sounds obtained during a stress test, significant differences in the transition patterns are clearly detected in the spectra between patients with myocardial infarction and normal persons The significant characteristics of these transition patterns may be applied to acoustic diagnosis of heart disease. >

Dependence of instantaneous transfer function on regional ischemic myocardial volume.

To obtain the instantaneous left ventricular transfer function curve (instantaneous TFC) under conditions of regional ischemia, sinusoidal accelerations ranging from 30 to 150 Hz were applied to a small area of the epicardium of cross-circulated isovolumic canine left ventricle, and the contralateral acceleration was measured under control and during regional coronary occlusion (n = 11). The TFC is the ratio of the output to input acceleration amplitudes. The instantaneous TFC was characterized as a single-peaked configuration under control coronary perfusion. However, TFCs progressively changed from a single-peaked to a double-peaked configuration during regional ischemia. To quantify this change in instantaneous TFC, we defined an index D as the mean squared difference of TFC during ischemia from TFC during control. Index D was linearly related to the percent mass of the ischemic region at 40 minutes after onset of ischemia. We conclude that 1) transfer function curves are sensitive measures of myocardial heterogeneity and 2) the fractional ischemic weight of the ventricle is a major factor in determination of the deformation in instantaneous TFC at the later stages of regional ischemia.

Simulation study on the effect of external vibration on left ventricular function: potential indicator of LV tolerance to the sudden reduction of myocardial contractility

In a previous study the authors reported that external mechanical vibration applied to the left ventricular (LV) epicardium induces contractility-dependent depression in LV pressure, stroke volume and stroke work. It was suggested that this depression may be caused by the direct effect of external vibration on contractile protein. In another paper in this issue, it is proved that LV function with various myocardial contractilities and the actual process of deterioration in heart failure are well simulated in the model proposed by Beyar and Sideman, after some modifications have been made. In the study reported here it is assumed that an external mechanical vibration induces sudden reduction in myocardial active stress in the model of Beyar and Sideman; in this way the contractility-dependent effect of external vibration on LV function has been simulated. The results of this simulation support the suggestion that external mechanical vibration directly affects contractile protein and reduces LV function, and it is further suggested that the reduction of LV function induced by external vibration reflects the reserve or tolerance capacity of LV to a sudden reduction of myocardial contractility.

Estimation of left ventricular myocardial elasticity and viscosity by a thick-walled spherical model

The authors measured the transfer function (TF) of the left ventricle (LV) in an isolated canine preparation. Here TF indicates the ratio of induced vibration in LV to input vibration when an external mechanical oscillation is applied. TF had a single peak the frequency of which changed from 40 Hz to 80 Hz when LV pressure (LVP) increased from 6 mm Hg to 96 mm Hg. A mathematical model was formulated to estimate the viscoelasticity of the spherical shell. This model was constructed of the material points, elastic components which connected all the material points, and viscous components placed in series with elastic components. Theoretical TF can be computed if the viscoelastic values are given. The value of viscoelasticity at which the theoretical TF best fitted the experimental TF was considered to be the viscoelasticity of the model. The validity of this approach was verified using a silicone spherical shell. The estimated myocardial elasticity was 40 kPa when LVP was 6 mm Hg, 160–170 kPa when LVP was 96 mm Hg and was approximately proportional to LVP, whereas viscosity showed small change. The inclination of elasticity was consistent with previous reports. These results proved that myocardial elasticity can be estimated by analysing the transfer function of the left ventricle.

Immature Core protein of hepatitis C virus induces an unfolded protein response through inhibition of ERAD-L in a yeast model system

The structural protein Core of hepatitis C virus (HCV), a cytosolic protein, induces endoplasmic reticulum (ER) stress and unfolded protein response (UPR) in hepatocytes, and is responsible for the pathogenesis of persistent HCV infection. Using yeast as a model system, we evaluated mechanisms underlying Core‐induced interference of ER homeostasis and UPR, and found that UPR is induced by the immature Core (aa 1–191, Core191) but not by the mature Core (aa 1–177, Core177). Interestingly, Core191 inhibits both ERAD‐L, a degradation system responsible for misfolded/unfolded proteins in the ER lumen, and ERAD‐M, a degradation system responsible for proteins carrying a misfolded/unfolded region in the ER membrane. In contrast, Core177 inhibits ERAD‐M but not ERAD‐L. In addition, requirement of an unfolded protein sensor in the ER lumen suggested that inhibition of ERAD‐L is probably responsible for Core191‐dependent UPR activation. These results implicate inadequate maturation of Core as a trigger for induction of ER stress and UPR.

A new approach to time dependent AR modeling of multi-frame signals and its application to diagnosis of myocardial infarction

A method for estimating spectrum transition between short-length multiframe signals in low SNR (signal-to-noise ratio) cases is presented. If the transition pattern is complex and/or there are large differences in the transition patterns among the individual sets of multiframe signals, it is difficult to estimate the transition pattern stably by the time-varying AR modeling because the results are considerably dependent on the choice of the basic functions to be used. The proposed approach uses a linear algorithm without any basic functions. Instead, the spectrum transition constraint is used, and the singular-value-decomposition-based technique is applied to obtain more accurate estimates. When this method is applied to the analysis of multiframe signals of the fourth heart sounds significant differences in the transition patterns are clearly detected in the spectra between patients with myocardial infarction and normal persons. The characteristics of these transition patterns may be applied to acoustic diagnosis of heart diseases.<<ETX>>

A case of bilateral multiple pulmonary arteriovenous fistula associated with bronchial artery to pulmonary vein fistula.

51才女性.高校時代にチアノーゼ,太鼓ばち指に気づき, 25才時胸部X線異常陰影(両側全肺野に境界明瞭な多数の均等性大結節陰影)を指摘されるも放置.その後29年間無症状に経過したが,心不全を発症し,肺動脈造影にて両側多発性肺動静脈瘻と診断した.また気管支動脈造影により気管支動脈-肺静脈瘻の合併も確認した. Rendu-Osler-Weber病の合併はないが,子宮・腎動静脈瘻の合併が疑われた.本例のように短絡率が大(40%)で著明な低酸素血症,多血症を伴い,体動脈とも交通がある肺動静脈瘻では,心不全が初発症状となりうる.