RV functional imaging: 3-D echo-derived dynamic geometry and flow field simulations

Abstract

We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts. cardiac image analysis; ventricular function; cardiac fluid dynamics; right ventricle; heart chamber volume QUANTITATIVE ANALYSIS of three-dimensional (3-D) digital cardiac images has become increasingly important given the recent advances in the digital cardiac imaging techniques of 3-D echocardiography, magnetic resonance imaging, computed tomography, and digital fluoroscopy (1,24,26). The growth of these digital imaging techniques is accompanied by an increasing usage of image manipulation tools, providing more elaborate image analysis and measurement and quantitative evaluation and leading to more refined diagnostic accuracy than visual interpretation alone. Moreover, complex mathematical procedures are being used to localize and highlight important changes in cardiac function that cannot be visually detected directly from the original images. With the concurrent development of high-performance computers and analytical software, a functional sort of imaging can now evolve, geared toward the creation of physiological images that are the result of a mathematical simulation derived from a set of images. Such functional imaging will allow visualization and understanding of the evolution of any dynamic process of interest (filling, ejection) within the heart. Accordingly, it should allow better insights into cardiac physiology and pathophysiology and may possibly detect warning signs of diseases not yet overt.This study developed innovative dynamic geometric chamber reconstruction models for use in functional imaging analyses of right ventricular (RV) filling dynamics and physiology. With the use of a new volumetric "prism method," it is first shown that the geometric chamber reconstructions provide accurate and reliable dynamic instantaneous RV chamber geometry ...

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

“…The development and refinement of three-dimensional cine-MR imaging techniques have enabled reconstruction of the ventricle by the interleaving of multiple long-and short-axis images. Similarly, three-dimensional echocardiography has also developed to a level of sophistication that permits expeditious and accurate determination of LV volumes and mass (27,28). These imaging modalities can thus provide very accurate geometric models of the heart that can yield reliable estimates of myocardial contractility.…”

Noninvasive Assessment of the Right Ventricular Filling Pressure Gradient

“…To date, the RV filling pressure difference (RVFPD) between these 2 locations can be measured only by sophisticated high-fidelity catheterization procedures or complex functional 3-dimensional imaging methods, which are clinically unavailable. [5][6][7] To the best of our knowledge, not even the magnitude of the physiological RVFPD has ever been reported for the human heart.…”

“…A functional image processing approach has been demonstrated to provide the distributions of pressure differences inside the RV. 7 This technique requires very high-resolution measurements of the endocardial boundaries in 3-dimensional plus time and complex processing, which were beyond the scope of this article. However, it is noteworthy that both the magnitude and waveforms of the RVFPD curves reported with this methodology 7 closely resemble our findings.…”

Complementarity and competitiveness of the intrinsic and extrinsic components of the total ventricular load: Demonstration after valve replacement in aortic stenosis

“…3,[13][14][15][16] Larger intraventricular gradients can be demonstrated when blood is ejected rapidly from an enlarged chamber through a normal-sized aortic anulus 3,4 as in aortic regurgitation, an instance of systolic ventriculoannular disproportion. 3 Analogous concepts were more recently put forward, [17][18][19] that govern previously unrecognized important aspects of the diastolic ventricular filling load. A new mechanism, the convective deceleration load, 18,19 was formulated as an important determinant of diastolic inflow during the upstroke of the E wave.…”

“…This underlies the concept of a diastolic ventriculoannular disproportion. [17][18][19] In the presence of left (right) ventricular outflow tract obstruction, including aortic (pulmonic) valvular stenosis, intraventricular ejection gradients of large magnitude are typical. 2,3,20 The total systolic ejection load Through the above-mentioned endeavors, the view was developed 3,13 that total ventricular systolic load comprises both extrinsic (the aortic root ejection pressure waveform) and intrinsic (flow-associated intraventricular pressure gradients) components.…”