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Biomedical subjects

Hideaki Kanzaki

Publications and source records attributed to Hideaki Kanzaki.

At least 19 recordsLinked to original sources
PubMed2006

Impact of blockade of histamine H2 receptors on chronic heart failure revealed by retrospective and prospective randomized studies.

OBJECTIVES: The goal of this work was to determine whether the blockade of histamine H2 receptors is beneficial for the pathophysiology of chronic heart failure (CHF). BACKGROUND: Because CHF is one of the major life-threatening diseases, we need to find a novel effective therapy. Intriguingly, our previous study, which predicts the involvement of histamine in CHF, suggests that we should test this hypothesis in patients with CHF. METHODS: We selected 159 patients who received famotidine among symptomatic CHF patients for the retrospective study. We blindly selected age- and gender-matched CHF patients receiving drugs for gastritis other than histamine H2 receptor blockers as a control group. For the prospective study, 50 symptomatic CHF patients were randomly divided into 2 groups. One group received famotidine of 30 mg/day for 6 months, and the other group received teprenone. RESULTS: In the retrospective study, famotidine of 20 to 40 mg decreased both left ventricular end-diastolic and end-systolic lengths (LVDd and LVDs, respectively) and the plasma B-type natriuretic peptide (BNP) levels (182 +/- 21 vs. 259 +/- 25 pg/ml, p < 0.05) with unaltered fractional shortening (FS). In a randomized, open-label study, compared with teprenone, famotidine of 30 mg prospectively decreased both New York Heart Association functional class (p < 0.05) and plasma BNP levels (183 +/- 26 pg/ml vs. 285 +/- 41 pg/ml, p < 0.05); this corresponded to decreasing both LVDd (57 +/- 2 mm vs. 64 +/- 2 mm, p < 0.05) and LVDs (47 +/- 2 mm vs. 55 +/- 2 mm, p < 0.05) with unaltered FS (15 +/- 1% vs. 17 +/- 1%). The frequency of readmission because of worsening of CHF was lower in the famotidine group (4% and 24%, p < 0.05). On the other hand, teprenone had no effects on CHF. CONCLUSIONS: Famotidine improved both cardiac symptoms and ventricular remodeling associated with CHF. Histamine H2 receptor blockers may have therapeutic benefits for CHF.

Aged↗
PubMed2006

Impaired systolic torsion in dilated cardiomyopathy: reversal of apical rotation at mid-systole characterized with magnetic resonance tagging method.

Left ventricular (LV) torsion plays an important role in squeezing the blood out of the heart. To characterize the systolic torsion in LV dysfunction, we studied using magnetic resonance imaging myocardial tagging method in 26 subjects: 17 patients with dilated cardiomyopathy (DCM, LV ejection fraction [EF], 27 +/- 8%) and 9 healthy control subjects. Grid-tagged LV short-axis cine images were acquired at base, mid and apex levels. Tag-intersections were tracked during the systole, thereby determining rotation angle (positive indicated clockwise from the apex). Peak torsion was defined as the maximum difference in rotation angle between the base and apex. Time to peak torsion was expressed as % systole by dividing the time by a total systolic time. Amplitude of the rotation at peak was less in DCM than in controls at both the base (0.1 +/- 2.9 vs. 2.6 +/- 1.6 degrees , P < 0.05) and apex (-5.9 +/- 5.3 vs. -11.2 +/- 2.5 degrees , P < 0.01). Amplitude of peak torsion was then less in DCM than in controls (6.1 +/- 3.4 vs. 13.6 +/- 2.5 degrees , P < 0.001), and the timing of peak was earlier (66 +/- 22 vs. 104 +/- 16% systole, P < 0.001). The amplitude of peak torsion was correlated with LVEF (r=0.74, P < 0.001). In conclusion, amplitude of systolic torsion was impaired in proportion to LV function. Systolic torsion in LV dysfunction was characterized by the discontinuing counter-rotation of the apex to the base before end-systole.

Adult↗
PubMed2006

Visualization of three-dimensional cardiac electrical excitation using standard heart model and anterior and posterior magnetocardiogram.

Our aim in this study is to obtain novel three-dimensional (3-D) images of cardiac electrical excitation that include morphological information on the whole heart. We obtain these 3-D images by projecting anterior and posterior two-dimensional (2-D) current-arrow maps (CAMs) onto a 3-D standard heart model. This standard heart model is adjusted to the individual subject's heart position by using the coordinates of the sinus node, which are obtained from magnetocardiogram (MCG) signals. The anterior and posterior CAMs are calculated by taking the orthogonal partial derivatives of the normal component of the anterior and posterior MCGs. After adjusting the base current values of the anterior and posterior CAMs, the adjusted CAMs are projected onto the standard heart model. We generated the projected CAMs (PCAMs) of the six phases (atrial, and ventricular, excitation) for seven healthy subjects. The validity of PCAM was evaluated by extracting the maximal current directions and positions from the PCAMs. The maximal current directions and positions during each excitation phase were almost in the same in the seven healthy subjects. Therefore, the PCAMs give us a clear view of the anterior and posterior myocardial excitation for the respective electrophysiological phases.

Adult↗
PubMed2006

Circadian variation of endothelial function in idiopathic dilated cardiomyopathy.

This study measured flow-mediated dilation (FMD) of the brachial artery 3 times a day (6:30 a.m., 11:30 a.m., and 9 p.m.) in 7 normal subjects and 14 patients with idiopathic dilated cardiomyopathy (7 in New York Heart Association [NYHA] functional class I or II and 7 in NYHA functional class III or IV). FMD in normal subjects and patients in NYHA class I or II showed a circadian variation, being lowest in the morning and highest at night. Compared with them, FMD in patients in NYHA class III or IV was lower and almost constant during the day, showing loss of significant circadian variation in endothelial function in patients with congestive heart failure.

Adult↗
PubMed2006

Effects of radial left ventricular dyssynchrony on cardiac performance using quantitative tissue Doppler radial strain imaging.

Our objective was to test the hypothesis that novel angle-corrected radial strain imaging can quantify left ventricular dyssynchrony associated with contractile impairment and improved with biventricular pacing. Eight open-chest dogs were studied by novel angle-corrected color-coded radial strain imaging and high-fidelity pressure-conductance catheters recording pressure-volume loops. Heart rate was controlled by right atrial pacing and all timing intervals were corrected by R-R interval (corrected interval = measured interval/(R-R interval)(1/2)). Left bundle branch block, simulated by right ventricular free wall pacing, resulted in marked radial dyssynchrony, which we defined as maximal time difference between peak segmental strain, from 39 +/- 17 to 354 +/- 49 milliseconds and stroke work decreased from 157 +/- 40 to 60 +/- 37 mJ, (P < .005 vs baseline). Depression of contractility by high-dose esmolol (end-systolic pressure-volume relationship from 5.7 +/- 2.4 to 3.6 +/- 1.0 mm Hg/mL) was associated with augmented dyssynchrony to 388 +/- 53 milliseconds (P < .05 vs baseline right ventricular pacing). Biventricular pacing improved dyssynchrony to 55 +/- 19 milliseconds and stroke work to 143 +/- 33 mJ (P < .05 vs right ventricular pacing). Changes in radial dyssynchrony correlated significantly with 6-site average regional strain (r = -0.93 +/- 0.05 individually, r = 0.80 overall) and stroke work (r = -0.88 +/- 0.12 individually, r = -0.82 overall). Angle-corrected radial strain imaging has clinical potential to quantify mechanical dyssynchrony and effects of biventricular pacing.

Animals↗
PubMed2006

Acute improvement in myocardial function assessed by myocardial strain and strain rate after aortic valve replacement for aortic stenosis.

OBJECTIVES: We investigated whether Doppler tissue imaging (tissue velocity, strain, and strain rate) could be useful to detect subtle left ventricular (LV) dysfunction in patients with aortic stenosis and changes in regional myocardial function after aortic valve replacement (AVR). METHODS: We studied 34 patients (age 69.2 +/- 10.4 years) with severe aortic stenosis, 21 of whom underwent AVR. Tissue velocity, systolic strain, strain rate, time to peak strain, and time to peak systolic and diastolic strain rates of basal and midsegments were measured in the apical 4-, 3-, and 2-chamber views before and 2 weeks after AVR. RESULTS: Strain and systolic strain rate showed the best correlation with LV ejection fraction (r = 0.80 and r = 0.70, respectively, both P < .0001). Early and late diastolic strain rates showed significant correlations with LV mass index (r = 0.45, P < .01; and r = 0.64, P < .0001, respectively) and time to peak strain, to peak systolic strain rate, and to peak early diastolic strain rate with aortic pressure gradient (r = 0.45, P < .01; r = 0.44, P < .01; and r = 0.56, P < .001, respectively) before AVR. Although LV mass index and LV systolic function did not change significantly after 2 weeks (LV mass index, 137 +/- 54 vs 125 +/- 36 g/m2; LV ejection fraction, 60 vs 58%, both P = not significant), peak strain and strain rates increased (P < .001) and time to peak strain and strain rate shortened after AVR (P < .001). Tissue velocities did not change significantly after AVR. CONCLUSIONS: Strain and strain rate parameters seemed to relate to LV function and aortic stenosis severity. Further, they seemed to be superior to tissue velocity and conventional echocardiography in detecting subtle changes in myocardial function after AVR before LV mass and LV function showed improvement.

Aged↗
PubMed2005

Infective tricuspid valve endocarditis with pulmonary emboli caused by Campylobacter fetus after tooth extraction.

We describe a case of infective endocarditis caused by Campylobacter fetus accompanied by pulmonary emboli. A 52-year-old man was referred to our hospital due to febrile temperatures with a history of dental treatment followed by eating raw meat. Computed tomography revealed multiple infiltrations and a nodule with low attenuation area and feeding vessels. A mobile mass, possible vegetation, attached to the tricuspid valve was detected by transthoracic echocardiography. Two blood cultures disclosed Campylobacter fetus. Long-term antibiotic therapy was given, curing the infection with valvuloplasty. We presented the possibility that infective Campylobacter fetus endocarditis after dental treatment was caused by eating raw meat.

Campylobacter Infections↗
PubMed2004

A mechanism for immediate reduction in mitral regurgitation after cardiac resynchronization therapy: insights from mechanical activation strain mapping.

OBJECTIVES: We tested the hypothesis that an immediate reduction in mitral regurgitation (MR) after cardiac resynchronization therapy (CRT) results from improved coordinated timing of the papillary muscle insertion sites, using the novel approach of mechanical activation strain mapping. BACKGROUND: Heart failure patients with left bundle branch block often benefit acutely from CRT; however, the role and mechanism of reduction of MR are unclear. METHODS: Twenty-six consecutive patients undergoing CRT with at least mild MR were studied (ejection fraction 24 +/- 6%; QRS duration 168 +/- 30 ms). Echocardiographic Doppler and strain imaging was performed immediately before and the day after CRT, as well as in 10 normal control subjects. Mechanical activation sequence maps were constructed using longitudinal strain from 12 basal and mid-LV sites, with color coding of time-to-peak strain. RESULTS: Mitral regurgitation by the volumetric method consistently decreased after CRT: regurgitant volume from 40 +/- 20 ml to 24 +/- 17 ml and regurgitant fraction from 40 +/- 12% to 25 +/- 14% (both: p < 0.001 vs. baseline). Normal controls had uniform segmental time-to-peak strain, with a difference of only 12 +/- 8 ms between all segments. In contrast, CRT patients at baseline had a 106 +/- 74 ms time delay between papillary muscle insertion sites (p < 0.001 vs. normal). This interpapillary muscle time delay shortened after CRT to 39 +/- 43 ms (p < 0.001 vs. baseline) and was significantly correlated with reductions in mitral regurgitant fraction (r = 0.77, p < 0.001). CONCLUSIONS: Cardiac resynchronization therapy significantly and immediately reduced MR. Improved coordinated timing of mechanical activation of papillary muscle insertion sites appears to be a mechanistic contributor to immediate MR reduction by CRT.

Aged↗
PubMed2004

Quantification of radial mechanical dyssynchrony in patients with left bundle branch block and idiopathic dilated cardiomyopathy without conduction delay by tissue displacement imaging.

Cardiac resynchronization therapy has made assessment of cardiac dyssynchrony clinically important. To test the hypothesis that echocardiographic displacement imaging can quantify dyssynchrony, 22 patients with left bundle branch block (LBBB), 14 with idiopathic dilated cardiomyopathy (IDC) without electrical conduction delay, and 22 normal controls were studied using radial angle-corrected displacement imaging. Control subjects had coordinated wall movement, whereas patients with LBBB had dyssynchrony characterized by early inward anteroseptal movement and markedly delayed posterior, lateral, or inferior regions (157 +/- 99 ms; p <0.001 vs normal). An interesting subset of patients with IDC without conduction delay (36%) had dyssynchrony with anteroseptal to posterior wall delays of 169 +/- 56 ms (p <0.001 vs normal), similar to patients with LBBB.

Adult↗
PubMed2004

Usefulness of echocardiographic tissue synchronization imaging to predict acute response to cardiac resynchronization therapy.

Echocardiographic tissue synchronization imaging (TSI) consists of color-coding time-to-peak tissue Doppler velocities. This study of 29 patients who underwent cardiac resynchronization therapy (CRT) demonstrated that differences in baseline time-to-speak velocities of opposing ventricular walls by TSI were greater in 15 patients, with an acute hemodynamic improvement. A >/=65 ms delay from the anterior septum to the posterior wall using the apical long-axis view had 87% sensitivity and 100% specificity for predicting an acute response. Although a subgroup without acute improvement had later decreases in end-systolic volume, suggesting that acute response underestimates long-term effects, TSI has potential to assist in guiding CRT.

Aged↗
PubMed2004

Regional heterogeneity of left ventricular myocardial work quantified using anatomical M-mode echocardiography.

BACKGROUND: Although assessment of left ventricular (LV) regional work per unit of myocardium (RWM) from the wall stress-area relationship has been proposed using M-mode echocardiography, the applicable region was limited. Anatomical M-mode is a new technique which permits the M-mode cursor to be angled in any direction on digital two-dimensional images. Our objective was to characterize regional heterogeneity of LV myocardial work using anatomical M-mode. METHODS: Sixteen patients were studied: 5 with idiopathic dilated cardiomyopathy (DCM), 4 hypertrophic cardiomyopathy (HCM), and 7 controls. Digital 2-dimensional echocardiographic cineloops were acquired from the mid LV short-axis view simultaneously with high-fidelity LV pressure. Using anatomical M-mode, LV internal diameters and wall thickness (H) were determined to calculate mean wall stress (sigma) at 6 equiangular directions. The volume of region, which was given by area times H, was assumed to be constant throughout one cardiac cycle from the incompressibility of myocardium. Thus, 1/H is proportional to the regional area, and then RWM was determined as an area within the sigma-ln (1/H) loop at each direction (positive values indicated a counterclockwise loop rotation). RESULTS: RWM from controls were heterogeneous with the highest in the lateral segments. The 6-segment average RWM was lower in both patients with DCM and HCM than controls (3.9 +/- 1.7 and 2.1 +/- 0.3 vs. 5.5 +/- 1.4 mJ/cm(3), both p < 0.05). RWM was particularly deteriorated at septal and inferior segments in patients with DCM (2.3 +/- 0.9 and 3.0 +/- 1.5 mJ/cm(3), both p < 0.05 vs. control) and at hypertrophied anterior and anteroseptal segments in patients with HCM (0.4 +/- 0.1 and 0.8 +/- 0.6 mJ/cm(3), both p < 0.01 vs. control). CONCLUSIONS: Anatomical M-mode enabled RWM assessment at all segments including the inferoseptum and lateral regions that had been impossible for analysis, revealing regional heterogeneity. The present method has the potential to provide additional information on myocardial mechanical condition.

Cardiomyopathy, Dilated↗
PubMed2004

Impact of catheter ablation on pulmonary vein morphology and mechanical function.

INTRODUCTION: Previous reports have documented that radiofrequency catheter ablation of pulmonary veins induces a significant increase in the peak velocity of transvenous blood flow. Although the magnitude of the increase infers a state of pulmonary vein stenosis, there have been no reports of direct visualization of the ablation zone. METHODS AND RESULTS: In each of 23 subjects, the myocardium investing one or more pulmonary veins (total of 42 veins) was electrically isolated by applying a confluent circumferential ablation lesion to the atrial side of the venoatrial junction. Doppler measurements of transvenous flow velocity were made before and after ablation using phased-array intracardiac echocardiography. Direct visualization of the ablation zone was performed using rotating intracardiac echocardiography, permitting assessment of shape, cross-sectional area, phasic variation in cross-sectional area, and wall thickness. In a subset of 5 subjects, a more detailed assessment of the ablation and contiguous regions was performed using three-dimensional echocardiography (rotating transducer). Prior to ablation, venoatrial junctions demonstrated noncircular shape and marked phasic variation in cross-sectional area. There was a trivial transvenous pressure gradient. After ablation, there was a significant increase in both anterograde and retrograde flow velocities and pressure gradient, the magnitudes of which were inversely proportional to the preablation and postablation areas. Direct visualization of the ablation zone revealed circumferential wall swelling, reduced cross-sectional area, and diminishment in phasic variation in cross-sectional area. Similar observations were made at contiguous nonablated sites, diminishing in magnitude as a function of distance. CONCLUSION: Pulmonary vein ablation induces significant acute changes in morphology and mechanical function that extend beyond the ablation zone.

Adult↗
PubMed2004

[Usefulness of conscious sedation with midazoram during transesophageal echocardiographic examination].

OBJECTIVES: Although transesophageal echocardiography is useful to identify various cardiovascular diseases, the semi-invasive nature of the examination hampers its routine application. We investigated whether conscious sedation using a low dose of intravenous midazoram was safe and useful during the examination. METHODS: We asked 55 consecutive patients undergoing transesophageal echocardiography (44 with midazoram, mean age 59 +/- 16 years, and 11 without midazoram, mean age 62 +/- 8 years) and the examiners about the effects of midazoram using a questionnaire. RESULTS: The mean dose of midazoram was 2.2 mg (range 1-3.5 mg). All examinations were done without any adverse events. Eighty-two percent of the patients with midazoram considered the examination under conscious sedation tolerable, whereas 91% without midazoram felt it untolerable. Most examiners felt manipulation of the echo probe was easier in patients with midazoram than in those without (69% vs 27%). CONCLUSIONS: Conscious sedation with a low dose of intravenous midazoram facilitated and increased patient tolerance during transesophageal echocardiographic examination.

Aged↗
PubMed2003

Regional correlation by color-coded tissue Doppler to quantify improvements in mechanical left ventricular synchrony after biventricular pacing therapy.

Cardiac resynchronization therapy (CRT) can improve cardiac function in patients with heart failure and left bundle branch block. To test a new synchrony index derived from mitral annular velocity by color tissue Doppler, 19 subjects were studied: 9 patients with heart failure and left bundle branch block at baseline and at 1, 3 and 6 months after CRT and 10 normal controls. The synchrony index in patients with heart failure was less than that in controls at baseline (r = 0.60 +/- 0.13 vs 0.94 +/- 0.02; p <0.01), but improved at 6 months after CRT (r = 0.77 +/- 0.09; p <0.05 vs baseline).

Aged↗
PubMed2003

Second-generation tissue Doppler with angle-corrected color-coded wall displacement for quantitative assessment of regional left ventricular function.

To test the hypothesis that a new tissue Doppler (TD) approach using angle-correction and transformation of velocity data to color-coded displacement data may objectively quantify regional left ventricular function, in vitro experiments were first performed with an oscillating echo target precisely controlled by a microstepping motor. Displacement varied from 1 to 15 mm (60 to 130 cycles/min) at angles of 0 degrees and 45 degrees to the echo transducer. Custom software transformed TD data to displacement data. Sixty-five subjects were then studied: 35 with wall motion abnormalities and 30 normal controls. Results were compared with independent visual assessment and caliper measurements of endocardial excursion from gray-scale images. In vitro displacement imaging strongly correlated with true displacement (r = 0.99, p <0.0001). In humans, peak transmural displacement discriminated normal results (6.3 +/- 3.2 mm) from hypokinesia (2.7 +/- 1.8 mm, p <0.05), akinesia (0.4 +/- 1.2 mm, p <0.05) from hypokinesia, and dyskinesia (-1.9 +/- 1.2 mm, p <0.05) from akinesia. Normal subendocardial displacement was 5.9 +/- 2.9 versus 4.0 +/- 3.9 mm in the epicardial layer (p <0.01). This displacement gradient was absent in abnormal segments. Displacement data correlated with endocardial excursion by calipers (parasternal views: r = 0.86, all views: r = 0.79, both p <0.0001). Overall accuracy of displacement imaging was 82% (kappa = 0.71) versus 66% (kappa = 0.43) for visual assessment with caliper data as the standard of reference. Angle-corrected displacement imaging was superior to routine visual assessment and is a promising new method to quantify regional left ventricular function.

Aged↗
PubMed2003

A new screening method to diagnose coronary artery disease using multichannel magnetocardiogram and simple exercise.

BACKGROUND: Magnetocardiography (MCG) is a non-contact mapping technique to record cardiac action currents. The Master's two-step electrocardiogram (ECG) test is a simple exercise method for screening coronary artery disease (CAD), but it is inadequate concerning the sensitivity. Our aim was to develop a new screening method using multichannel MCG instead of ECG. METHODS: Thirty subjects (aged 54 +/- 16 years, 27 males), 17 of whom had CAD confirmed by coronary angiography, underwent the Master's exercise ECG test. After the exercise, MCG signals were acquired every minute during recovery with a 64-channel MCG system (MC-6400, Hitachi Ltd). We integrated tangential components of the MCG signals within QRS (during 20, 40, 80, and 120 ms centering on R-wave peak) immediately after exercise (Iex) and 5 minutes after exercise (Irec). The exercise-induced change of currents [(Iex-Irec)/Irec] was determined and normalized for each channel, and the maximal change among 64 channels, maximal QRS integral change, was used as a diagnostic index for myocardial ischemia. RESULTS: The maximal QRS integral change during 40 ms was significantly higher in the CAD group than in the control group (0.81 +/- 0.51 vs. 0.36 +/- 0.19, p < 0.01). A sensitivity and specificity for predicting CAD by the change > 0.44 were 82 % and 85 %, respectively, yielding a diagnostic accuracy of 83 %. The conventional Master's ECG test identified the CAD patients with a diagnostic accuracy of 63 % (sensitivity 47 %, specificity 85 %). CONCLUSION: The Master's two-step exercise test with a 64-channel MCG system showed the high diagnostic accuracy, despite of non-contact recording and simple exercise. The magnetic field in the depolarization process has the potential to detect the subtle myocardial ischemia induced by exercise.

Adult↗