Tracking Improvement in Simulated Marine Biogeochemistry Between CMIP5 and CMIP6.

Purpose of Review: The changes or updates in ocean biogeochemistry component have been mapped between CMIP5 and CMIP6 model versions, and an assessment made of how far these have led to improvements in the simulated mean state of marine biogeochemical models within the current generation of Earth system models (ESMs). Recent Findings: The representation of marine biogeochemistry has progressed within the current generation of Earth system models. However, it remains difficult to identify which model updates are responsible for a given improvement. In addition, the full potential of marine biogeochemistry in terms of Earth system interactions and climate feedback remains poorly examined in the current generation of Earth system models. Summary: Increasing availability of ocean biogeochemical data, as well as an improved understanding of the underlying processes, allows advances in the marine biogeochemical components of the current generation of ESMs. The present study scrutinizes the extent to which marine biogeochemistry components of ESMs have progressed between the 5th and the 6th phases of the Coupled Model Intercomparison Project (CMIP).

Intraventricular pressure gradients in left ventricular aneurysms determined by color M-mode Doppler method: an animal study.

BACKGROUND: Left ventricular aneurysm (LVA) may affect diastolic intraventricular blood flow. Color M-mode (CMM) Doppler flow propagation patterns are abnormal in the presence of apical aneurysms. The aim of this study was to validate the accuracy of CMM echocardiography for assessing the existence and size of LVA and to determine the intraventricular pressure gradient in LVA. METHODS: CMM of the transmitral inflow in early diastole was obtained from the apical 4-chamber view in 19 sheep. The presence of the break point where the velocity decreased abruptly in the mitral inflow (point D) was determined and the distance between the apex and point D was measured. The intraventricular pressure difference between the base and the apex was measured by a catheter while it was calculated using CMM with the Euler equation. RESULTS: The presence of the break point D showed 84% sensitivity and 100% specificity for determining the existence of an LVA. Distance between the apex and point D correlated well with scar size. Catheter- and CMM-derived intraventricular pressure difference correlated and agreed well (y = 1.0 x -0.2, r = 0.94). CONCLUSIONS: The point of abrupt decrease in propagation velocity of the CMM recording indicated the presence and size of LVA. Intraventricular pressure gradients were determined noninvasively by CMM echocardiography with reasonable accuracy.

The accuracy of left ventricular mass determined by real-time three-dimensional echocardiography in chronic animal and clinical studies: a comparison with postmortem examination and magnetic resonance imaging.

Real-time 3-dimensional echocardiography (RT3DE), 2-dimensional echocardiography (2DE), and M-mode echocardiography were performed in 28 sheep with cardiac pathologies and 27 patients with heart disease to demonstrate the superiority of RT3DE over M-mode and 2DE for the determination of left ventricular mass. Postmortem examination and magnetic resonance imaging were used as a reference standard for the animal and clinical studies, respectively. In the animal study, the highest concordance correlation (0.92) was obtained between the actual weight of left ventricular mass and that estimated by RT3DE (0.69 for 2DE and 0.77 for M-mode, P < .001). In the clinical study, RT3DE also provided the best concordance correlation with left ventricular mass determined by magnetic resonance imaging (0.91 for RT3DE, 0.83 for 2DE, and 0.38 for M-mode; P < .0001).

Quantitative analysis of left atrial function during left ventricular ischemia with and without left atrial ischemia: a real-time 3-dimensional echocardiographic study.

Left atrial (LA) systolic and diastolic function were analyzed in an animal model of acute left ventricular ischemia with LA ischemia by proximal left circumflex coronary artery occlusion or without LA ischemia by midleft anterior descending coronary artery occlusion (7 sheep in each group). LA pressures and LA volumes were simultaneously recorded using a catheter and real-time 3-dimensional echocardiography, respectively. LA stroke volume represented 63% of left ventricular stroke volume during left anterior descending coronary artery occlusion, but only 32% during left circumflex coronary artery occlusion. This animal study with 3-dimensional echocardiographic determination of absolute LA volumes demonstrated dramatic depression of LA function during proximal left circumflex coronary artery occlusion as compared with left anterior descending coronary artery occlusion.

Automated mitral annular tracking: a novel method for evaluating mitral annular motion using two-dimensional echocardiography.

We developed an automated mitral annular tracking method based on a digital processing of high frame rate cineloop images of 2-dimensional echocardiography. In this study, its feasibility and accuracy was validated in 11 healthy volunteers and 16 patients with left ventricular (LV) dysfunction. The mitral annular excursion measured by automated mitral annular tracking agreed well with that measured by 3-dimensional echocardiography and correlated with LV ejection fraction. The longitudinal mitral annular excursion was reduced whereas the radial one was preserved for patients with LV dysfunction compared with control subjects. The novel automated mitral annular tracking method is clinically feasible and has potential capability to quantify the comprehensive mitral annular motion for evaluating LV function in a clinical setting.

Combination of pulsed-wave Doppler and real-time three-dimensional color Doppler echocardiography for quantifying the stroke volume in the left ventricular outflow tract.

Real-time three-dimensional (3-D) color Doppler echocardiography (RT3D) is capable of quantifying flow. However, low temporal resolution limits its application to stroke volume (SV) measurements. The aim of the present study was, therefore, to develop a reliable method to quantify SV. In animal experiments, cross-sectional images of the LV outflow tract were selected from the RT3D data to calculate peak flow rates (Q(p3D)). Conventional pulsed-wave (PW) Doppler was performed to measure the velocity-time integral (VTI) and the peak velocity (V(p)). By assuming that the flow is proportional to the velocity temporal waveform, SV was calculated as alpha x Q(p3D) x VTI/V(p), where alpha is a temporal correction factor. There was an excellent correlation between the reference flow meter and RT3D SV (mean difference = -1. 3 mL, y = 1. 05 x -2. 5, r = 0. 94, p < 0. 01). The new method allowed accurate SV estimations without any geometric assumptions of the spatial velocity distributions.

Mitral annular motion as a surrogate for left ventricular ejection fraction: real-time three-dimensional echocardiography and magnetic resonance imaging studies.

AIMS: To validate the accuracy of mitral annular motion assessed by real-time three-dimensional echocardiography (RT3DE) as a surrogate for determination of the left ventricular function in comparison with magnetic resonance imaging (MRI). METHODS AND RESULTS: Forty-seven patients with a variety of cardiac pathologies underwent both RT3DE and MRI exams. After 3D data sets were transferred to a PC with a custom-made program, nine consecutive rotational apical plane images (20 degrees apart) were displayed. The two mitral leaflet insertion points were manually identified in each plane. The geometry of the mitral annulus was reconstructed from a total of 18 coordinates (x, y, z), and the changes in mitral annular area and mitral annular motion along the apical long axis were calculated. The left ventricular ejection fraction (LVEF) determined by MRI was 41+/-18%, and 24 patients had LVEF<50%. Mitral annular motion (y) obtained by RT3DE was 11+/-5 mm and correlated moderately well with LVEF (x) measured by MRI (r=0.84, y=0.25x+0.43, p<0.0001). The mitral annular motion<12 mm was a good threshold for detecting LVEF<50% with 96% sensitivity, 85% specificity, and 91% accuracy. CONCLUSION: Mitral annular motion determined by RT3DE correlated moderately well with LVEF; and systolic motion, <12 mm, accurately detected LV dysfunction.

Determinant of left atrial dilation in patients with hypertrophic cardiomyopathy: a real-time 3-dimensional echocardiographic study.

To identify the determinants of left atrial (LA) dilation for patients with hypertrophic obstructive cardiomyopathy (HOCM), first we validated LA volume determination by real-time 3-dimensional echocardiography using magnetic resonance imaging in patients. Subsequently, real-time 3-dimensional echocardiography and 2-dimensional Doppler echocardiography were performed in 60 patients with HOCM and in 17 age-matched control subjects. LA volumes and left ventricular (LV) filling pressures were higher for patients with HOCM than in control subjects. By stepwise multilinear regression analysis, LV end-diastolic pressure, resting LV outflow tract pressure gradient, and LV wall thickness were significant determinants of LA dilation. However, tau, -dP/dt, LV stiffness, provokable pressure gradient, and mitral regurgitation did not have any independent relationship with LA volumes. Therefore, it is concluded that LA volume can be accurately determined by real-time 3-dimensional echocardiography; and LA dilation in patients with HOCM is related to LV filling pressure, LV outflow tract pressure gradient, and LV wall thickness.

Real-time three-dimensional color doppler evaluation of the flow convergence zone for quantification of mitral regurgitation: Validation experimental animal study and initial clinical experience.

BACKGROUND: Pitfalls of the flow convergence (FC) method, including 2-dimensional imaging of the 3-dimensional (3D) geometry of the FC surface, can lead to erroneous quantification of mitral regurgitation (MR). This limitation may be mitigated by the use of real-time 3D color Doppler echocardiography (CE). Our objective was to validate a real-time 3D navigation method for MR quantification. METHODS: In 12 sheep with surgically induced chronic MR, 37 different hemodynamic conditions were studied with real-time 3DCE. Using real-time 3D navigation, the radius of the largest hemispherical FC zone was located and measured. MR volume was quantified according to the FC method after observing the shape of FC in 3D space. Aortic and mitral electromagnetic flow probes and meters were balanced against each other to determine reference MR volume. As an initial clinical application study, 22 patients with chronic MR were also studied with this real-time 3DCE-FC method. Left ventricular (LV) outflow tract automated cardiac flow measurement (Toshiba Corp, Tokyo, Japan) and real-time 3D LV stroke volume were used to quantify the reference MR volume (MR volume = 3DLV stroke volume - automated cardiac flow measurement). RESULTS: In the sheep model, a good correlation and agreement was seen between MR volume by real-time 3DCE and electromagnetic (y = 0.77x + 1.48, r = 0.87, P <.001, delta = -0.91 +/- 2.65 mL). In patients, real-time 3DCE-derived MR volume also showed a good correlation and agreement with the reference method (y = 0.89x - 0.38, r = 0.93, P <.001, delta = -4.8 +/- 7.6 mL). CONCLUSIONS: real-time 3DCE can capture the entire FC image, permitting geometrical recognition of the FC zone geometry and reliable MR quantification.

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

OBJECTIVE: The 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. BACKGROUND: Most indexes described to quantify LV systolic function, such as LV ejection fraction and cardiac output, are dependent on loading conditions. METHODS: In 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. RESULTS: Left 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. CONCLUSIONS: For 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.

Quantitative analysis of aortic regurgitation: real-time 3-dimensional and 2-dimensional color Doppler echocardiographic method--a clinical and a chronic animal study.

BACKGROUND: For evaluating patients with aortic regurgitation (AR), regurgitant volumes, left ventricular (LV) stroke volumes (SV), and absolute LV volumes are valuable indices. AIM: The aim of this study was to validate the combination of real-time 3-dimensional echocardiography (3DE) and semiautomated digital color Doppler cardiac flow measurement (ACM) for quantifying absolute LV volumes, LVSV, and AR volumes using an animal model of chronic AR and to investigate its clinical applicability. METHODS: In 8 sheep, a total of 26 hemodynamic states were obtained pharmacologically 20 weeks after the aortic valve noncoronary (n = 4) or right coronary (n = 4) leaflet was incised to produce AR. Reference standard LVSV and AR volume were determined using the electromagnetic flow method (EM). Simultaneous epicardial real-time 3DE studies were performed to obtain LV end-diastolic volumes (LVEDV), end-systolic volumes (LVESV), and LVSV by subtracting LVESV from LVEDV. Simultaneous ACM was performed to obtain LVSV and transmitral flows; AR volume was calculated by subtracting transmitral flow volume from LVSV. In a total of 19 patients with AR, real-time 3DE and ACM were used to obtain LVSVs and these were compared with each other. RESULTS: A strong relationship was found between LVSV derived from EM and those from the real-time 3DE (r = 0.93, P <.001, mean difference (3D - EM) = -1.0 +/- 9.8 mL). A good relationship between LVSV and AR volumes derived from EM and those by ACM was found (r = 0.88, P <.001). A good relationship between LVSV derived from real-time 3DE and that from ACM was observed (r = 0.73, P <.01, mean difference = 2.5 +/- 7.9 mL). In patients, a good relationship between LVSV obtained by real-time 3DE and ACM was found (r = 0.90, P <.001, mean difference = 0.6 +/- 9.8 mL). CONCLUSION: The combination of ACM and real-time 3DE for quantifying LV volumes, LVSV, and AR volumes was validated by the chronic animal study and was shown to be clinically applicable.