Emerging Trends in CV Flow Visualization

Abstract

Blood flow patterns are closely linked to the morphology and function of the cardiovascular system. These patterns reflect the exceptional adaptability of the cardiovascular system to maintain normal blood circulation under a wide range of workloads. Accurate retrieval and display of flow-related information remains a challenge because of the processes involved in mapping the flow velocity fields within specific chambers of the heart. We review the potentials and pitfalls of current approaches for blood flow visualization, with an emphasis on acquisition, display, and analysis of multidirectional flow. This document is divided into 3 sections. First, we provide a descriptive outline of the relevant concepts in cardiac fluid mechanics, including the emergence of rotation in flow and the variables that delineate vortical structures. Second, we elaborate on the main methods developed to image and visualize multidirectional cardiovascular flow, which are mainly based on cardiac magnetic resonance, ultrasound Doppler, and contrast particle imaging velocimetry, with recommendations for developing dedicated imaging protocols. Finally, we discuss the potential clinical applications and technical challenges with suggestions for further investigations.

Comparative numerical study on left ventricular fluid dynamics after dilated cardiomyopathy

“…Other techniques available for LV flow assessment are the Echo Doppler, Echo-PIV (Particle Image Velocimetry), and phase-contrast CMR (Sengupta et al, 2012b). These have the advantage of being direct in-vivo measures without requiring reconstruction methods, although each presents limitations.…”

“…There is an increasing consensus that maladaptive fluid mechanics contributes to cardiac inefficiency and participates in the modulation toward phenotypic patterns of heart failure (HF) (Bolger et al, 2007;Pedrizzetti et al, 2010;Sengupta et al, 2012b). HF is associated with ventricular remodeling: modification of the LV, which progressively alters its function.…”

“…Flow analysis has the potential to represent an early predictor of changes in LV function. Nevertheless, the knowledge of intraventricular flow in pathologic conditions is very limited and clinical references for diagnostic use are missing (Sengupta et al, 2012b).…”

On the accuracy of intracardiac flow velocimetry methods

“…This method works based on combining measured axial velocities with estimated radial velocities according to the physical principles [33]. VFM ignores the three-dimensional component of the flow by assuming the flow is two-dimensional, solves the 2D continuity equation, and use ventricular wall velocity acquired by tissue tracking to improve the results [34].…”

“…Generally, the ultrasound-based velocimetry methods are all bounded by the limitations and constraints of echocardiographic acquisitions, such as inter and intra-operator variabilities and acoustic shadowing. Furthermore, limited frame rate of echocardiographic acquisitions-particularly in 3D-is currently a major obstacle for accurate assessment of high-velocity values and advancement of 3D ultrasound-based velocimetry modalities for intracardiac flow [21,33,37]. More recent efforts may overcome these limitations and pave the way for routine clinical applications [33,[37][38][39].…”