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Biomedical subjects

Masaki Tanabe

Publications and source records attributed to Masaki Tanabe.

At least 19 recordsLinked to original sources
PubMed2006

A novel two-dimensional echocardiographic image analysis system using artificial intelligence-learned pattern recognition for rapid automated ejection fraction.

OBJECTIVES: We sought to test the hypothesis that a novel 2-dimensional echocardiographic image analysis system using artificial intelligence-learned pattern recognition can rapidly and reproducibly calculate ejection fraction (EF). BACKGROUND: Echocardiographic EF by manual tracing is time consuming, and visual assessment is inherently subjective. METHODS: We studied 218 patients (72 female), including 165 with abnormal left ventricular (LV) function. Auto EF incorporated a database trained on >10,000 human EF tracings to automatically locate and track the LV endocardium from routine grayscale digital cineloops and calculate EF in 15 s. Auto EF results were independently compared with manually traced biplane Simpson's rule, visual EF, and magnetic resonance imaging (MRI) in a subset. RESULTS: Auto EF was possible in 200 (92%) of consecutive patients, of which 77% were completely automated and 23% required manual editing. Auto EF correlated well with manual EF (r = 0.98; 6% limits of agreement) and required less time per patient (48 +/- 26 s vs. 102 +/- 21 s; p < 0.01). Auto EF correlated well with visual EF by expert readers (r = 0.96; p < 0.001), but interobserver variability was greater (3.4 +/- 2.9% vs. 9.8 +/- 5.7%, respectively; p < 0.001). Visual EF was less accurate by novice readers (r = 0.82; 19% limits of agreement) and improved with trainee-operated Auto EF (r = 0.96; 7% limits of agreement). Auto EF also correlated with MRI EF (n = 21) (r = 0.95; 12% limits of agreement), but underestimated absolute volumes (r = 0.95; bias of -36 +/- 27 ml overall). CONCLUSIONS: Auto EF can automatically calculate EF similarly to results by manual biplane Simpson's rule and MRI, with less variability than visual EF, and has clinical potential.

Aged↗
PubMed2006

Velocity vector imaging to quantify ventricular dyssynchrony and predict response to cardiac resynchronization therapy.

Velocity vector imaging is a novel quantitative echocardiographic technique that was applied to routine grayscale echocardiographic images of 23 patients with heart failure who underwent cardiac resynchronization therapy. The hypothesis was tested that velocity vector imaging can quantify left ventricular mechanical dyssynchrony and predict response to resynchronization therapy. Tissue velocities were determined by the automated tracking of periodic B-mode image patterns on digital cine loops from standard apical 4-chamber, 2-chamber, and long-axis views, with the user tracing the mid left ventricular wall from a single frame. Dyssynchrony was determined as the greatest opposing wall peak longitudinal systolic velocity delay from the 3 views. Responders, defined as those with >or=15% increases in the ejection fraction, had greater baseline dyssynchrony than nonresponders (opposing wall velocity delays of 131 +/- 83 vs 52 +/- 60 ms, p <0.05), and >or=75 ms predicted response with 85% sensitivity and 80% specificity when followed 8 +/- 5 months after resynchronization therapy. Baseline electrocardiographic QRS duration was not predictive in the same patients. In conclusion, echocardiographic velocity vector imaging has potential for clinical utility.

Blood Flow Velocity↗
PubMed2006

Effect of concordance between sites of left ventricular pacing and dyssynchrony on acute electrocardiographic and echocardiographic parameters in patients with heart failure undergoing cardiac resynchronization therapy.

BACKGROUND: Wide QRS complexes are associated with left ventricular (LV) dyssynchrony, but an optimal site of LV pacing has not been established. HYPOTHESIS: We hypothesized that concordance between the sites of LV pacing and of latest LV mechanical activation during cardiac resynchronization therapy (CRT) is associated with more favorable acute echocardiographic changes. METHODS: An analysis of 28 consecutive patients (64+/-15 years, 46% male, 52% ischemic heart disease, LV ejection fraction 0.24+/-0.07, QRS 163+/-22 ms, New York Heart Association > or = 3 93%) implanted with biventricular (BIV) defibrillators was performed. Sites of latest LV activation were determined by tissue Doppler imaging (TDI) and speckle tracking (ST). The site of LV pacing was determined by fluoroscopy in two views. A concordance score (0-5) was created to describe the proximity of the pacing site to the site of the latest mechanical activation. RESULTS: Compared with the worst concordance score, a perfect score was associated with shorter QRS width with LV (187+/-40 vs. 246+/-8 ms, p= 0.048) and BIV (134+/-19 ms vs. 179+/-39 ms, p = 0.05) but not with right ventricular pacing. A perfect concordance score was also associated with a greater acute reduction in LV volumes in systole (42+/-36 ms 16+/-22 ms, p = 0.068) and diastole (47+/-37 vs. 8+/-31 ml, p = 0.043) 24 h after CRT device implantation. CONCLUSIONS: A high concordance is associated with shorter QRS width with LV and BIV pacing and greater acute reduction in LV volumes. The effect of concordance on the intermediate and long-term response to BIV pacing deserves further evaluation.

Acute Disease↗
PubMed2006

Force- and relaxation-frequency relations in patients with diastolic heart failure.

BACKGROUND: Chronotropic effects on myocardial contractility (the positive force-frequency relation) and relaxation (the positive relaxation-frequency relation) are impaired in patients with congestive heart failure and depressed left ventricular (LV) ejection fraction (systolic heart failure [SHF]). However, the force- and relaxation-frequency relation and LV-arterial coupling in patients with diastolic heart failure (DHF) has not been fully investigated. METHODS AND RESULTS: To examine inotropic and lusitropic responsiveness to atrial pacing, LV pressure-volume relations were measured using a conductance catheter and microtip manometer in patients with DHF (n = 18) and SHF (n = 11). In patients with SHF, an increase in heart rate by 40 beat/min did not affect LV end-systolic elastance (Ees), which reflects LV contractility, or the time constant of LV relaxation. By contrast, in patients with DHF, an increase in heart rate by 40 beat/min significantly enhanced Ees (2.1 vs 2.9 mm Hg/mL, P < .05) but not the time constant. Furthermore, LV-arterial coupling, quantified as Ees/arterial elastance, was impaired during pacing in patients with DHF (1.1 vs 0.8, P < .05) as well as SHF. CONCLUSIONS: In patients with DHF, the force-frequency relation was preserved, but the relaxation-frequency relation was impaired. Furthermore, LV-arterial coupling was impaired as heart rate increased, which may be related to the impaired LV function. These results suggest that the impaired relaxation-frequency relation and exacerbated LV-arterial coupling during tachycardia may be an important therapeutic target in patients with DHF.

Adult↗
PubMed2006

Single beat determination of regional myocardial strain measurements in patients with atrial fibrillation.

Atrial fibrillation (AF) and congestive heart failure share several features and often coexist in the same patients; therefore, serial assessment of regional myocardial function is important for patients with AF. However, the clinical assessment of regional myocardial function in AF is unreliable and difficult because of beat-to-beat variation. Recent reports have shown that the ratio of the preceding to the prepreceding R-R interval (RR1/RR2) can be used to assess global left ventricular systolic function. Accordingly, we tested the hypothesis that regional wall motion can be estimated from a single beat based on RR1/RR2 in patients with AF. Peak systolic strain at basal, mid, and apical segments of the septal wall was measured by Doppler tissue imaging from an apical 4-chamber view for 30 seconds in 50 patients with AF (mean ejection fraction 52.1 +/- 15.3%; mean heart rate 76.4 +/- 16.0/min). There was a positive linear relationship between peak strain and RR1/RR2 and RR1, and a negative relationship with RR2, with the correlation of peak strain to RR1/RR2 was better than that in RR1 or RR2. Furthermore, peak strain at RR1/RR2 = 1 was calculated from the linear regression and compared with the average measured value of all recorded cardiac cycles in each patient. In all cases, average peak strain showed a significant positive correlation with RR1/RR2 at each segment (r = 0.99). In conclusion, regional myocardial strain at RR1/RR2 = 1 on the linear regression represents the average value of all recorded cardiac cycles in patients with AF.

Aged↗
PubMed2005

Effects of human atrial natriuretic peptide on cardiac function and hemodynamics in patients with high plasma BNP levels.

Both atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) bind preferentially to the natriuretic peptide A receptor. Therefore, we hypothesized that the positive inotropic and lusitropic effects of ANP might be blunted in patients with moderate congestive heart failure and high BNP levels. Micromanometers and conductance catheters were used to obtain relatively load-insensitive left ventricular pressure-volume analysis in order to compare the myocardial and load-altering actions of ANP in 20 patients with low and high plasma BNP levels. In the low-BNP group (plasma BNP levels <230 pg/ml), ANP infusion significantly decreased end-systolic pressure and end-diastolic pressure and volume, increased end-systolic elastance, and shortened left ventricular relaxation. By contrast, in the high-BNP group (plasma BNP levels >230 pg/ml), the effect of ANP infusion on LV contractility was blunted but its beneficial effects on LV diastolic function and LV-arterial coupling remained. Thus, ANP infusion may improve LV diastolic function even in patients with moderate heart failure and high plasma BNP levels.

Aged↗
PubMed2005

Assessment of left ventricular systolic function in patients with chronic atrial fibrillation and dilated cardiomyopathy using the ratio of preceding to prepreceding R-R intervals.

The objective of this study was to determine the relation between left ventricular (LV) systolic function and the ratio of preceding (RR1) to prepreceding (RR2) R-R intervals in patients with chronic atrial fibrillation (AF) and dilated cardiomyopathy. LV systolic function (Emax) was examined using a conductance catheter with a micromanometer in 13 patients with chronic AF and dilated cardiomyopathy. We calculated Emax as a load-independent index of LV contractility and compared it with RR1, RR2, and the ratio of RR1/RR2. We analyzed 50+/-13 cardiac cycles (range 18-61) in each patient. Average heart rate was 80+/-13 beats/min, and ejection fraction over all cardiac cycle in each patient measured by conductance catheter was 31+/-8%. Emax was positively correlated with RR1 and RR1/RR2 in all patients, and negatively correlated with RR2 in all patients. In each patient, correlation coefficients of Emax with RR1/RR2 were greater than those with either RR1 or RR2. Furthermore, Emax at RR1/RR2=1 in the linear regression line reflected average Emax over all cardiac cycles in each patient. In conclusion, we have shown that LV contractility correlated positively with RR1/RR2 in patients with chronic AF and dilated cardiomyopathy, and LV contractility at RR1/RR2=1 represents the average value of contractility over all cardiac cycles.

Adult↗
PubMed2005

Electron microscopic findings of cardiomyopathy with limb girdle muscular dystrophy.

Cardiac involvement in limb girdle muscular dystrophy has considered to be rare. This is the first report showing the electron microscopic findings of dilated cardiomyopathy (DCM) accompanied with limb girdle muscular dystrophy. The findings described in this report indicate that limb girdle muscular dystrophy may be yet another cause of DCM.

Cardiomyopathy, Dilated↗
PubMed2005

Change in filling pattern with preload reduction reflects left ventricular relaxation.

BACKGROUND: The early diastolic mitral valve pressure gradient and the rate of left ventricular filling are determined by the rate of left ventricular relaxation and left atrial pressure at the time of mitral valve opening. Accordingly, we hypothesized that the left ventricular filling pattern with preload reduction can be used to estimate left ventricular relaxation in patients with preserved systolic function. METHODS: We evaluated the relationship between the logistic time constant of left ventricular relaxation and left ventricular filling pattern calculated from the time derivative of left ventricular volume using a microtipmanometer and a conductance catheter in 26 consecutive patients with preserved left ventricular ejection fraction (>45%). Left ventricular filling patterns were determined from the maximal rates of early diastolic left ventricular filling (E velocity) and atrial filling (A velocity) before and after preload reduction by inferior venal caval occlusion. RESULTS AND CONCLUSIONS: There was no significant relationship between the logistic time constant of left ventricular relaxation and the E/A velocity ratio at baseline. However, the time constant was correlated with the E/A velocity ratio after venal caval occlusion (r=-0.47, p=0.02). Furthermore, the time constant was correlated with %E/A velocity change, which was defined as the rate of change of E/A before and after caval occlusion divided by E/A after caval occlusion, more significantly (r=-0.67, p<0.01) than with the E/A velocity ratio after caval occlusion. Thus, the left ventricular filling pattern with preload reduction can be used to estimate left ventricular relaxation in patients with preserved left ventricular ejection fraction.

Aged↗
PubMed2005

Nitroglycerin improves left ventricular relaxation by changing systolic loading sequence in patients with excessive arterial load.

Nitroglycerin abbreviates left ventricular (LV) relaxation through improved hemodynamics as well as by direct actions on the myocardium. The aim of this study was to examine whether the changing systolic loading sequence during nitroglycerin administration affects LV relaxation in patients with excessive arterial load. By use of a conductance catheter with microtip manometer, the effects of intravenous nitroglycerin (0.3-0.5 microg/kg/min) on LV function and hemodynamics were examined in 39 patients with various degrees of LV contractility. Patients were divided into two groups according to LV-arterial coupling, the ratio of end-systolic elastance (Ees) to effective arterial elastance (Ea). In patients with Ees/Ea ratio > 1, nitroglycerin had no effect on the time to peak force or on the time constant of LV relaxation (tau). On the other hand, in patients with Ees/Ea < 1, which represented excessive arterial load, nitroglycerin significantly shortened the time to peak force, shifted the peak of the loading sequence from late to early systole, and significantly decreased tau without any changes in Ees. Thus, nitroglycerin improved LV relaxation in patients with excessive arterial load partly by changing the systolic loading sequence.

Aged↗
PubMed2004

Effective cardiac resynchronization after Dor procedure and mitral annuloplasty.

Endoventricular circular patch plasty (Dor ventriculoplasty) is an effective strategy for severely impaired left ventricular function due to ischemic cardiomyopathy. Cardiac resynchronization therapy improves cardiac function in patients with severe congestive heart failure and an intraventricular conduction delay. The present case demonstrates the efficacy of adding cardiac resynchronization to Dor ventriculoplasty and mitral annuloplasty in a patient with severely impaired left ventricular function and an intraventricular conduction delay.

Aged↗
PubMed2004

Intravascular hemolysis in aortic stenosis.

A 67-year-old woman with rheumatic aortic stenosis for 20 years was admitted to our hospital. Although she had no overt symptoms, she had severe aortic valve stenosis with a transvalvular pressure gradient of more than 150 mmHg. She had also been suffering from anemia and mild chronic renal failure. A peripheral blood smear showed numerous fragmented erythrocytes. Hemoglobin was 8.4 g/dl, lactate dehydrogenase was 316 IU/l, haptoglobin was less than 7.3 mg/dl, and hemosiderinuria was evident. We diagnosed intravascular hemolysis related to aortic stenosis. After we performed an aortic valve replacement, fragmentation on the peripheral blood smear dramatically disappeared.

Aged↗
PubMed2004

Alternans decay of postextrasystolic potentiation in human left ventricle.

An organ-level assessment of the total Ca2+ handled in the excitation-contraction coupling in a beating heart has been accomplished in canine left ventricles (LVs). This approach combines the intramyocardial Ca2+ recirculation fraction (RF) with the cardiac O2 consumption for the excitation-contraction coupling. The RF has conventionally been obtained from the exponential decay of the postextrasystolic (PES) potentiation of myocardial contractility. However, in canine LVs, the PES contractility in terms of Emax (end-systolic pressure-volume ratio) has been shown to decay generally in alternans under both physiological and pathological conditions. Nevertheless, the RF can be obtained from the exponential decay component in the PES Emax alternans decay. We expected that the same Ca2+ assessment could be applied to the human heart. As the first step, we investigated whether the PES Emax would decay in alternans or exponentially in patient LVs. We retrospectively analyzed 13 patient cases that had stable regular beats unexpectedly interrupted by a spontaneous extrasystole followed by a PES compensatory pause during their diagnostic examination. These patients had either mitral regurgitation, old myocardial infarction, or dilated cardiomyopathy. Their LV Emax decayed consistently in alternans within the first several PES beats. These Emax alternans decays resemble those reported in canine LVs. This finding suggests for the first time the applicability of the same organ-level RF assessment method developed for canine hearts to human hearts.

Animals↗