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Masaki Nii

Publications and source records attributed to Masaki Nii.

13 recordsLinked to original sources
PubMed2006

Short and midterm results of aortic valve cusp extension in the treatment of children with congenital aortic valve disease.

BACKGROUND: We evaluated our experience with aortic valve cusp extension techniques to identify predictors of successful intraoperative repair and subsequent durability. METHODS: Twenty-two children (ages 5-18 years) underwent aortic cusp extension with autologous pericardium between 1999 and 2005. Sixteen children had previous surgical or percutaneous intervention. Ten children had bicuspid aortic valves. Cusp extensions were performed on 1 cusp in 3 patients, 2 cusps in 3, and 3 cusps in 16. Serial echocardiographic measures (n = 81) were obtained during a 5-year period and underwent blinded review. Longitudinal trajectories of ventricular and aortic valve function were modeled using mixed linear regression analysis. RESULTS: There was no hospital or late mortality. Five-year freedom from valve replacement was 75%. Comparison of preoperative and post-repair echocardiograms demonstrated reductions in aortic insufficiency (decreased in jet-width/aortic valve diameter ratio from 0.39 +/- 0.12 to 0.22 +/- 0.11; p < 0.0001), aortic stenosis (decreased in peak aortic valve gradient from 41 +/- 25 mm Hg to 29 +/- 15 mm Hg; p = 0.04), and left ventricular end-diastolic dimensions Z-score (decreased from 1.39 +/- 0.38 to 1.16 +/- 0.34; p < 0.001). During the follow-up period, post-repair jet-width and aortic valve diameter increased nonlinearly (p < 0.001). Patients with postoperative peak aortic gradients greater than 30 mm Hg had progression of aortic stenosis, whereas those with lesser postoperative peak gradients tended to regress during follow-up (p < 0.001). The decrement in Z-score of the left ventricular end-diastolic dimensions remained stable during the follow-up period. CONCLUSIONS: Aortic valve cusp extension can result in acceptable hemodynamic results with stabilization of left ventricular geometry. However, residual lesions are common and progression and regression of these lesions can be predicted based on echocardiographic data.

Adolescent↗
PubMed2006

Doppler tissue imaging in the assessment of atrioventricular conduction time: validation of a novel technique and comparison with electrophysiologic and pulsed wave Doppler-derived equivalents in an animal model.

Accurate assessment of atrioventricular conduction time (AVCT) is crucial for early detection of evolving fetal heart block. Simultaneous pulsed wave Doppler (PD) interrogation of left ventricular inflow and outflow is mainly used to study fetal AVCT. Limitations of this modality include its dependency on loading conditions and merging early and late diastolic inflow waves at faster heart rate (HR). Sequential analysis of atrioventricular myocardial motion by Doppler tissue imaging (DTI) might be more useful in this regard. In 15 open-chest pigs, AVCT was measured by PD, DTI, and electrocardiogram at baseline HR and during incremental atrial pacing up to 200 beats/min. Electromechanical delay and pre-ejection period were assessed at baseline and maximal HR. DTI-derived AVCT correlated better with PR intervals and allowed measurements at faster HRs than did PD (P < .05). Pre-ejection period prolonged with faster HR (P < .001), unlike electromechanical delay. In conclusion, DTI allows more accurate measurement of AVCT over a wider HR range than does PD.

Animals↗
PubMed2006

Three-dimensional tricuspid annular function provides insight into the mechanisms of tricuspid valve regurgitation in classic hypoplastic left heart syndrome.

BACKGROUND: Tricuspid regurgitation (TR) has a negative impact on outcome in hypoplastic left heart syndrome (HLHS). There is a paucity of data assessing the mechanisms of TR. Lateral forces from the left ventricle play an important role in normal tricuspid valve (TV) function. This study evaluates the role of real-time 3-dimensional echocardiography in the assessment of the TV annulus and subvalvular apparatus in HLHS. METHODS: In all, 31 real-time 3-dimensional echocardiographic studies from 26 patients (1 day-17 years old) with classic HLHS were included. In all, 7 studies were before and 8 were after first-stage palliation; 8 were postcavopulmonary shunt and 8 were post-Fontan. Only patients with severe left ventricular attenuation were included. Studies were subdivided into two groups: mild TR (N = 20) and severe TR (STR) (N = 11). Data from 17 control subjects were used for comparison. TV annular area, bending angle (saddle shape), and position of anterior papillary muscle were analyzed. RESULTS: All annular segments moved in equally during systole in mild TR, whereas septal-lateral diameter contraction was significantly diminished in STR. TV annular area was larger in HLHS (mild TR, 1265 +/- 325; STR, 1767 +/- 450 mm2/m2) than in control subjects (762 +/- 85) (P < .001). However, area change was reduced only in STR (12.4 +/- 4.6% vs control subjects 20.4 +/- 8.3%, P < .05). Annular shape was flat during systole in HLHS. Anterior papillary muscle was laterally displaced in STR. CONCLUSIONS: TV annular dynamics were different in patients with HLHS as a result of lack of interaction form left ventricle. Annular function, especially in septal-lateral direction, was further impaired in STR.

Adolescent↗
PubMed2006

The impact of patch augmentation on left atrioventricular valve dynamics in patients with atrioventricular septal defects: early and midterm follow-up.

OBJECTIVE: Left atrioventricular valve pericardial patch may prevent valve replacement. We assessed patch annular dynamics compared with conventional repair and normal annuli. METHODS: Transesophageal 3-dimensional echocardiography was acquired preoperatively and postoperatively in atrioventricular septal defects (n = 10, 5 patch, 5 conventional repair). Real-time 3-dimensional annular motion at midterm was compared with that of healthy children (n = 10). Parameters were: annular area, perimeter, segmental diameter, bending angle, stenosis, and regurgitation. RESULTS: Regurgitant jet area ratio decreased in both patient groups. Conventional repair reduced annular area (P = .02). Patch repair showed an annular area larger than normal (P = .01). Control subjects had increased systolic area whereas operative groups showed a reduction. Patch repair had segmental diameters similar to normal whereas conventional repair was inhomogeneous. Annular bending angle was maintained after operation. CONCLUSION: Patch repair in pediatrics shows durability without shrinkage or expansion. Improved stenosis and regurgitation does not change by midterm. Operation causes increased annular stiffness and diminished compliance. Neither technique establishes normal annular eccentricity.

Aortic Valve Insufficiency↗
PubMed2006

Assessment of the evolution of normal fetal diastolic function during mid and late gestation by spectral Doppler tissue echocardiography.

OBJECTIVE: To establish gestational age-specific reference values in healthy singleton fetuses, we prospectively assessed the evolution of diastolic longitudinal wall-motion velocities by spectral Doppler tissue imaging. METHODS: Early (Ea) and late diastolic (Aa) peak Doppler tissue imaging velocities were analyzed in 114 fetuses (age range: 14-42 weeks) at the base of right ventricular free wall, ventricular septum, and left ventricular free wall and compared with early (E) and late (A) diastolic peak Doppler inflow velocities. RESULTS: A linear increase in Ea, Aa, and Ea/Aa ratio was documented at all sites with advancing gestation. Likewise, the peak E flow velocities of both atrioventricular valves and the tricuspid peak A flow velocity increased. The ratio of peak E/Ea velocities decreased exponentially as a result of a more rapid increase in Ea than E, to reach a stable E/Ea relationship only in the early third trimester. CONCLUSIONS: There was a strong positive correlation between Ea and Aa velocities and gestational age indicating improved diastolic myocardial lengthening with advancing gestation. Reference charts for Doppler tissue imaging velocities were established that will allow identification of fetal diastolic function abnormalities.

Echocardiography, Doppler↗
PubMed2006

Three-dimensional echocardiography improves the understanding of the mechanisms and site of left atrioventricular valve regurgitation in atrioventricular septal defect.

OBJECTIVES: The purpose of this study was to determine whether 3-dimensional echocardiography (3DE) provides additional information regarding the mechanisms and sites of left atrioventricular valve regurgitation in atrioventricular septal defect compared with transesophageal 2-dimensional echocardiography (2DE). METHODS: Eleven patients with a median age of 5.4 years (2.9-11.6 years) and a median weight of 16.8 kg (13.7-38.3 kg) with an atrioventricular septal defect underwent simultaneous transesophageal 2DE and 3DE before operation. RESULTS: The 2DE-3DE agreement for the assessment of the superior and mural leaflet size was 72.7%. The 2DE-3DE agreement for coaptation failure, a residual or primary cleft, and commissural abnormalities as a mechanism of regurgitation were 72.7%, 63.6%, and 36.4%, respectively. For jet sites the 2DE-3DE agreement was 63.6% for a commissural and central location. CONCLUSION: Three-dimensional echocardiography provides new and superior data regarding the mechanisms and sites of left atrioventricular valve regurgitation in atrioventricular septal defect.

Cardiac Surgical Procedures↗
PubMed2005

Fetal brady- and tachyarrhythmias: new and accepted diagnostic and treatment methods.

Sustained bradyarrhythmias are typically the result of symptomatic sinus bradycardia, atrial bigeminy or complete atrioventricular (AV) block. Fetal tachyarrhythmias relate to sinus tachycardia, atrial flutter and supraventricular tachycardia as the main aetiology. Ultrasound is essential to understand the underlying arrhythmia mechanism, to study the impact on cardiac function, to exclude cardiac defects or tumours, and to survey the fetal heart rate and well-being, e.g. during anti-arrhythmic treatment. Based on retrospective studies, several more or less safe, effective and well-tolerated anti-arrhythmic agents are currently available for the treatment of atrial and supraventricular tachycardia. Isolated congenital complete AV block is mainly related to maternal anti-Ro/La auto-antibodies. The rationale to treat a fetus at this irreversible stage of AV nodal damage is primarily to mitigate or prevent concomitant myocardial inflammation and to augment cardiac output. A recently published study demonstrated a significant improved outcome with transmaternal dexamethasone and beta-stimulation.

Bradycardia↗
PubMed2005

Insight into normal mitral and tricuspid annular dynamics in pediatrics: a real-time three-dimensional echocardiographic study.

BACKGROUND: Although there are animal or adult studies analyzing annular motion of the mitral valve (MV) or tricuspid valve (TV) separately, there are no data analyzing interaction between the MV and TV, or data from the pediatric population. METHODS: A total of 17 healthy children (age 3-15 years) were enrolled in this study. Using real-time 3-dimensional echocardiography, annular area, perimeter, segmental diameter, and bending angle were obtained and analyzed. RESULTS: MV area increased during systole, in contrast to TV area, which decreased. TV area demonstrated a greater reduction of lateral diameter during systole. Bending motion became most acute in early diastole, which was greater for the TV. CONCLUSIONS: MV area change differs from adults, which may be explained by a more compliant myocardium in children. Greater lateral forces on TV prevent it from becoming circular, thus, preserving valve competency. Both valves show a bending motion, which becomes most prominent during isovolumic relaxation continuing into early diastole for the TV, suggesting a relationship with torsional forces within the ventricles.

Adolescent↗
PubMed2005

Isovolumic but not ejection phase Doppler tissue indices detect left ventricular dysfunction caused by coronary stenosis.

BACKGROUND: Isovolumic acceleration (IVA) obtained by tissue Doppler echocardiography (TDE) is a sensitive and relatively load-independent index for assessing systolic ventricular function. IVA also has the ability to describe the force-frequency relationship during incremental atrial pacing in vivo. OBJECTIVE: We sought to assess the ability of IVA to detect global left ventricular (LV) dysfunction induced by coronary constriction. METHODS: In 6 open-chest anesthetized pigs we examined right ventricular and LV long-axis function by TDE (4-chamber view) with simultaneous invasive measurements of intraventricular pressure, maximum dP/dt, minimum dP/dt, and tau by microtip catheter. A pneumatic cuff was placed around the proximal portion of left anterior descending coronary artery (LAD) and distal flow was monitored by transonic flow probe. Mean arterial pressures were monitored by indwelling cannula. Baseline studies assessed force-frequency relationships with TDE and invasive measurements during incremental pacing from 100 to 200/min (20/min increments every 10 minutes). The protocol was repeated 10 minutes after balloon inflation to reduce LAD blood flow by 50%. RESULTS: Compared with baseline, LV pressure decreased significantly (P = .03, 2-way analysis of variance) as did maximum dP/dt (P < .004) with LAD constriction. At the same time IVA and isovolumic velocity at the LV free wall were significantly reduced (P < .002 and P = .04, respectively) and both IVA and isovolumic velocity were correlated with dP/dt (r = 0.45, P < .002, and r = 0.35, P < .02, respectively). TDE systolic indices were unchanged in the right ventricle. CONCLUSION: IVA detects changes in global LV systolic function during LAD constriction and may be a useful clinical tool to diagnose ischemia.

Animals↗
PubMed2005

Three-dimensional echocardiography improves the understanding of left atrioventricular valve morphology and function in atrioventricular septal defects undergoing patch augmentation.

OBJECTIVES: We sought to address the role of 3-dimensional echocardiography in the evaluation of the left atrioventricular valve in children with an atrioventricular septal defect who underwent patch augmentation of their valve for either regurgitation or left ventricular outflow tract obstruction. METHODS: Five children whose ages ranged between 4.5 and 9.2 years and who underwent patch augmentation of their left atrioventricular valve had a preoperative and postoperative transesophageal echocardiogram with 3-dimensional reconstruction to evaluate the left atrioventricular valve. The indication for operation was left atrioventricular valve regurgitation in 3 patients and left ventricular outflow tract obstruction in 2 patients. Three were rerepairs, and 2 were primary repairs. Both 3-dimensional morphology and color Doppler data were obtained. Two- and 3-dimensional findings were correlated with surgical observations through the use of direct inspection and video images obtained with a head-mounted super-VHS camera. RESULTS: In each case there was precise correlation between the 3-dimensional and surgical findings as to the cause of leaflet failure in those with regurgitation. The site that would require leaflet augmentation could be determined by means of 3-dimensional echocardiography. Three-dimensional echocardiography provided more specific detail as to the morphology and function of the left atrioventricular valve than did its 2-dimensional counterpart. CONCLUSIONS: Three-dimensional echocardiography provides detailed information about the status of the left atrioventricular valve in the atrioventricular septal defect and can aid in the planning of either primary or secondary repair.

Child↗
PubMed2004

Peak negative myocardial velocity gradient and wall-thickening velocity during early diastole are noninvasive parameters of left ventricular diastolic function in patients with Duchenne's progressive muscular dystrophy.

Myocardial velocity gradient and wall-thickening velocity were measured in the interventricular septum and left ventricular posterior wall (LVPW) by color-coded M-mode Doppler tissue echocardiography in patients with Duchenne's progressive muscular dystrophy (DMD) with a normal shortening fraction (n = 14) and age-matched control subjects (n = 40). In the LVPW, peak myocardial velocity gradients during systole and early diastole were significantly lower for patients with DMD than in control subjects (P <.0005, and P <.0001, respectively). Peak myocardial wall-thickening velocities of the LVPW during systole and early diastole were also lower for patients with DMD (P <.0005 and P <.0001, respectively). Mitral peak atrial to early filling velocity ratio was not significantly different between the 2 groups. The cut-off values of peak myocardial velocity gradients and wall-thickening velocities of the LVPW during early diastole for differentiation between patients with DMD and control subjects were -5.8/s and -6.0 cm/s, respectively (sensitivity/specificity: 93%/93% and 93%/85%, respectively). In conclusion, wall thinning during early diastole is frequently abnormal in patients with DMD, even when conventional echocardiographic findings are normal.

Adolescent↗
PubMed2002

Quantification of the myocardial velocity gradient and myocardial wall thickening velocity in healthy children: a new indicator of regional myocardial wall motion.

Doppler tissue imaging allows the measurement of tissue motion velocity in real time. However, tissue velocities are affected by translational motion and by the angle of Doppler interrogation. The myocardial velocity gradient and myocardial wall thickening velocity, determined by color Doppler tissue imaging, can be used to evaluate regional wall thickening and thinning motion independent of translational motion. To determine the control values for myocardial velocity gradient and myocardial wall thickening velocity for the interventricular septum and posterior wall, we studied 120 healthy children (mean age: 7.8 +/- 5.0 years). Peak values of myocardial velocity gradient and myocardial wall thickening velocity at each cardiac phase were measured: systole, early diastole, and atrial contraction. The peak values of myocardial velocity gradient and myocardial wall thickening velocity were higher in the posterior wall than those in the interventricular septum, suggesting that thickening and thinning are more dynamic in the posterior wall. Linear regression analysis demonstrated that absolute values of myocardial velocity gradient at systole, early diastole, and atrial contraction, and wall thickening velocity at atrial contraction decreased with body surface area (BSA). On the other hand, absolute values of myocardial wall thickening velocity at systole and early diastole increased with BSA, and myocardial wall thickening velocity at early diastole in interventricular septum did not change. Myocardial velocity gradient at systole and early diastole, and myocardial wall thickening velocity at systole were strongly related to BSA. In contrast, myocardial velocity gradient and myocardial wall thickening velocity at atrial contraction strongly correlated with time interval between 2 consecutive QRS complexes. Because myocardial wall thickening velocity at early diastole in the interventricular septum did not correlate with BSA or time interval between 2 consecutive QRS complexes, it might evaluate diastolic function of interventricular septum independent of body size or heart rate.

Blood Flow Velocity↗