Hiroyuki Tsujino

Validation of real-time three-dimensional echocardiography for quantifying left ventricular volumes in the presence of a left ventricular aneurysm: in vitro and in vivo studies

OBJECTIVESnTo validate the accuracy of real-time three-dimensional echocardiography (RT3DE) for quantifying aneurysmal left ventricular (LV) volumes.nnnBACKGROUNDnConventional two-dimensional echocardiography (2DE) has limitations when applied for quantification of LV volumes in patients with LV aneurysms.nnnMETHODSnSeven aneurysmal balloons, 15 sheep (5 with chronic LV aneurysms and 10 without LV aneurysms) during 60 different hemodynamic conditions and 29 patients (13 with chronic LV aneurysms and 16 with normal LV) underwent RT3DE and 2DE. Electromagnetic flow meters and magnetic resonance imaging (MRI) served as reference standards in the animals and in the patients, respectively. Rotated apical six-plane method with multiplanar Simpsons rule and apical biplane Simpsons rule were used to determine LV volumes by RT3DE and 2DE, respectively.nnnRESULTSnBoth RT3DE and 2DE correlated well with actual volumes for aneurysmal balloons. However, a significantly smaller mean difference (MD) was found between RT3DE and actual volumes (-7 ml for RT3DE vs. 22 ml for 2DE, p = 0.0002). Excellent correlation and agreement between RT3DE and electromagnetic flow meters for LV stroke volumes for animals with aneurysms were observed, while 2DE showed lesser correlation and agreement (r = 0.97, MD = -1.0 ml vs. r = 0.76, MD = 4.4 ml). In patients with LV aneurysms, better correlation and agreement between RT3DE and MRI for LV volumes were obtained (r = 0.99, MD = -28 ml) than between 2DE and MRI (r = 0.91, MD = -49 ml).nnnCONCLUSIONSnFor geometrically asymmetric LVs associated with ventricular aneurysms, RT3DE can accurately quantify LV volumes.

Cosgrove-Edwards annuloplasty system: Midterm results

BACKGROUNDnThe Cosgrove-Edwards Annuloplasty System includes a universally flexible band that corrects mitral annular dilatation via measured plication of the posterior annulus. The purpose of this study was to evaluate midterm clinical and functional results in the first 197 patients receiving this flexible annuloplasty band at mitral valve repair.nnnMETHODSnFrom February 1993 to July 1994, 197 consecutive patients with mitral regurgitation had mitral valve repair using this system. Valve disease was degenerative in 73%, rheumatic in 15%, ischemic in 5%, infectious in 2.5%, and other in 4%.nnnRESULTSnImmediately after repair, echocardiographic mitral regurgitation was none or trivial in 92%, 1+ in 5%, and 2+ in 3%. There were no hospital deaths. Late follow-up was available in 195 patients (99%), with 661 patient-years of follow-up available for analysis. Four-year actuarial survival was 93%, freedom from thromboembolism 94%, from endocarditis 98%, and from reoperation 95%. At a mean interval of 18 months, echocardiography in 157 patients demonstrated no or trace mitral regurgitation in 56%, 1+ in 24%, 2+ in 9%, 3+ in 6%, and 4+ in 3%. At a mean of 61 +/- 5 months, reconstruction of the mitral annulus from real-time three-dimensional echocardiographic images in 10 patients confirmed preserved nonplanar shape and sphincter mechanism of the mitral annulus. Annular orifice area decreased 28% +/- 11% during the cardiac cycle from a mean of 10.1 +/- 3.9 cm2 in diastole to 7.2 +/- 2.8 cm2 in systole.nnnCONCLUSIONSnThis annuloplasty system is effective for repair of mitral regurgitation secondary to all causes and preserves mitral annular flexibility and function at 5-year follow-up.

Real-time three-dimensional color doppler echocardiography for characterizing the spatial velocity distribution and quantifying the peak flow rate in the left ventricular outflow tract

Quantification of flow with pulsed-wave Doppler assumes a flat velocity profile in the left ventricular outflow tract (LVOT), which observation refutes. Recent development of real-time, three-dimensional (3-D) color Doppler allows one to obtain an entire cross-sectional velocity distribution of the LVOT, which is not possible using conventional 2-D echo. In an animal experiment, the cross-sectional color Doppler images of the LVOT at peak systole were derived and digitally transferred to a computer to visualize and quantify spatial velocity distributions and peak flow rates. Markedly skewed profiles, with higher velocities toward the septum, were consistently observed. Reference peak flow rates by electromagnetic flow meter correlated well with 3-D peak flow rates (r = 0.94), but with an anticipated underestimation. Real-time 3-D color Doppler echocardiography was capable of determining cross-sectional velocity distributions and peak flow rates, demonstrating the utility of this new method for better understanding and quantifying blood flow phenomena.

Left ventricular outflow tract mean systolic acceleration as a surrogate for the slope of the left ventricular end-systolic pressure-volume relationship.

OBJECTIVEnThe goal of this study was to analyze left ventricular outflow tract systolic acceleration (LVOT(Acc)) during alterations in left ventricular (LV) contractility and LV filling.nnnBACKGROUNDnMost indexes described to quantify LV systolic function, such as LV ejection fraction and cardiac output, are dependent on loading conditions.nnnMETHODSnIn 18 sheep (4 normal, 6 with aortic regurgitation, and 8 with old myocardial infarction), blood flow velocities through the LVOT were recorded using conventional pulsed Doppler. The LVOT(Acc) was calculated as the aortic peak velocity divided by the time to peak flow; LVOT(Acc) was compared with LV maximal elastance (E(m)) acquired by conductance catheter under different loading conditions, including volume and pressure overload during an acute coronary occlusion (n = 10). In addition, a clinically validated lumped-parameter numerical model of the cardiovascular system was used to support our findings.nnnRESULTSnLeft ventricular E(m) and LVOT(Acc) decreased during ischemia (1.67 +/- 0.67 mm Hg.ml(-1) before vs. 0.93 +/- 0.41 mm Hg.ml(-1) during acute coronary occlusion [p < 0.05] and 7.9 +/- 3.1 m.s(-2) before vs. 4.4 +/- 1.0 m.s(-2) during coronary occlusion [p < 0.05], respectively). Left ventricular outflow tract systolic acceleration showed a strong linear correlation with LV E(m) (y = 3.84x + 1.87, r = 0.85, p < 0.001). Similar findings were obtained with the numerical modeling, which demonstrated a strong correlation between predicted and actual LV E(m) (predicted = 0.98 [actual] -0.01, r = 0.86). By analysis of variance, there was no statistically significant difference in LVOT(Acc) under different loading conditions.nnnCONCLUSIONSnFor a variety of hemodynamic conditions, LVOT(Acc) was linearly related to the LV contractility index LV E(m) and was independent of loading conditions. These findings were consistent with numerical modeling. Thus, this Doppler index may serve as a good noninvasive index of LV contractility.

Interaliasing distance of the flow convergence surface for determining mitral regurgitant volume: A validation study in a chronic animal model

OBJECTIVESnWe aimed to validate a new flow convergence (FC) method that eliminated the need to locate the regurgitant orifice and that could be performed semiautomatedly.nnnBACKGROUNDnComplex and time-consuming features of previously validated color Doppler methods for determining mitral regurgitant volume (MRV) have prevented their widespread clinical use.nnnMETHODSnThirty-nine different hemodynamic conditions in 12 sheep with surgically created flail leaflets inducing chronic mitral regurgitation were studied with two-dimensional (2D) echocardiography. Color Doppler M-mode images along the centerline of the accelerating flow towards the mitral regurgitation orifice were obtained. The distance between the two first aliasing boundaries (interaliasing distance [IAD]) was measured and the FC radius was mathematically derived according to the continuity equation (R(calc) = IAD/(1 - radicalv(1)/v(2)), v(1) and v(2) being the aliasing velocities). The conventional 2D FC radius was also measured (R(meas)). Mitral regurgitant volume was then calculated according to the FC method using both R(calc) and R(meas). Aortic and mitral electromagnetic (EM) flow probes and meters were balanced against each other to determine the reference standard MRV.nnnRESULTSnMitral regurgitant volume calculated from R(calc) and R(meas) correlated well with EM-MRV (y = 0.83x + 5.17, r = 0.90 and y = 1.04x + 0.91, r = 0.91, respectively, p < 0.001 for both). However, both methods resulted in slight overestimation of EM-MRV (Delta was 3.3 +/- 2.1 ml for R(calc) and 1.3 +/- 2.3 ml for R(meas)).nnnCONCLUSIONSnGood correlation was observed between MRV derived from R(calc) (IAD method) and EM-MRV, similar to that observed with R(meas) (conventional FC method) and EM-MRV. The R(calc) using the IAD method has an advantage over conventional R(meas) in that it does not require spatial localization of the regurgitant orifice and can be performed semiautomatedly.

Impact of temporal resolution on flow quantification by real-time 3D color Doppler echocardiography: numerical modeling and animal validation study

Real-time, 3D color Doppler echocardiography (RT3D) is capable of quantifying flow at the LV outflow tract (LVOT). However, previous works have found significant underestimation for flow rate estimation due to finite scanning time (ST) of the color Doppler. The authors have, therefore, developed a mathematical model to correct the impact of ST on flow quantification and validated it by an animal study. Scanning time to cover the entire cross-sectional image of the LVOT was calculated as 60 ms, and the underestimation due to temporal averaging effect was predicted as 18/spl plusmn/7%. In the animal experiment, peak flow rates were obtained by spatially integrating the velocity data front the cross-sectional color images of the LVOT. By applying a correction factor, there was an excellent agreement between reference flow rate by an electromagnetic flow meter and RT3D (A/spl uml/=-5.6 ml/s, r=0.93), which was significantly better than without correction (p<0.001). Real-time, color 3D echocardiography was capable of quantifying flow accurately by applying the mathematical correction.

Estimation of the spatial mean and peak flow velocities using real-time 3D color Doppler echocardiography: in vitro and in vivo studies

Using real-time, three-dimensional (3D) color Doppler, experimental studies were performed to quantify velocity in the out flow tract from cross-sectional, short axis images. In vitro experiments showed an excellent linear correlation between the reference pulsed wave (PW) Doppler and 3D color estimates of the peak velocities (r=0.98). In an animal experiment 3D peak flow velocities showed a reasonably good agreement with reference peak velocities by PW Doppler (r=0.76, delta =+11.6%). The spatial mean velocity by 3D showed a good linear relationship with PW peak velocity, but with an anticipated underestimation (r=0.81, delta=-43 %) due to the non-uniform velocity profile. Real-time, color 3D echocardiography was capable of quantifying velocities accurately, permitting the calculation of flow volume without any geometrical assumptions about flow distribution.

Comparison of left ventricular stroke volume determination by real-time three-dimensional echocardiography and conventional two-dimensional echocardiography: an animal study during non-ischemic and ischemic conditions

Recently, 3D echocardiography (3DE) has developed the capability to capture 3D images in real-time and has been reported to be accurate for estimating left ventricular (LV) volume. The authors hypothesized that real-time 3DE could determine LV stroke volumes (SV) more accurately than conventional 2DE. The aim of this study was to compare 2DE and 3DE for estimating LV stroke volumes during a variety of hemodynamic conditions, including left anterior descending (LAD) coronary artery occlusions. During a total of 30 hemodynamic conditions in 6 sheep with chronic aortic regurgitation, electromagnetic (EM) flow probes and meters were used to obtain LV SV. LV end-diastolic (LV EDV) and LV end-systolic volumes (LV ESV) were measured using real-time; 3DE with Simpsons rule (slice spacing 7 mm). For 24 conditions without LAD occlusions, SV by EM ranged from 27 to 66 ml (average 45/spl plusmn/10 ml). The correlation for LV SV measured by 3DE and that by EM was excellent (r=0.92, y=0.91x+3.6, /spl Delta/=-1/spl plusmn/4 ml, n=24), and better than that between 2DE and EM (r=0.62, y=0.68x+8.8, /spl Delta/=-5.6/spl plusmn/9.4 ml, p=0.0003). For 6 conditions during LAD occlusion, SV by EM ranged from 26 to 58 ml (average 41/spl plusmn/12 ml). SV derived from 3DE also agreed well with values derived by EM (r=0.96); however, the r-value between 2DE and EM was reduced to 0.58. It is concluded that real-time 3DE provided accurate assessment of LV SV under both ischemic and nonischemic conditions, while conventional 2DE showed poor correlations with reference standards, especially for SVs during coronary artery occlusion.