A clinical method for mapping and quantifying blood stasis in the left ventricle

Abstract

In patients at risk of intraventrcular thrombosis, the benefits of chronic anticoagulation therapy need to be balanced with the pro-hemorrhagic effects of therapy. Blood stasis in the cardiac chambers is a recognized risk factor for intracardiac thrombosis and potential cardiogenic embolic events. In this work, we present a novel flow image-based method to assess the location and extent of intraventricular stasis regions inside the left ventricle (LV) by digital processing flow-velocity images obtained either by phase-contrast magnetic resonance (PCMR) or 2D color-Doppler velocimetry (echo-CDV). This approach is based on quantifying the distribution of the blood Residence Time (TR) from time-resolved blood velocity fields in the LV. We tested the new method in illustrative examples of normal hearts, patients with dilated cardiomyopathy and one patient before and after the implantation of a left ventricular assist device (LVAD). The method allowed us to assess in-vivo the location and extent of the stasis regions in the LV. Original metrics were developed to integrate flow properties into simple scalars suitable for a robust and personalized assessment of the risk of thrombosis. From a clinical perspective, this work introduces the new paradigm that quantitative flow dynamics can provide the basis to obtain subclinical markers of intraventricular thrombosis risk. The early prediction of LV blood stasis may result in decrease strokes by appropriate use of anticoagulant therapy for the purpose of primary and secondary prevention. It may also have a significant impact on LVAD device design and operation set-up.

Keywords: Blood stasis; Echocardiography; Intraventricular thrombosis; Left ventricular assist devices; Phase contrast magnetic resonance; Residence time.

Conflict of interest statement

Conflict of interest statement

All authors: Nothing to disclose.

Copyright © 2016 Elsevier Ltd. All rights reserved.

Figures

FIGURE 1

3-D intraventricular velocity field and residence time map in a pig at mitral valve opening (A) and at the end of filling (B). The wireframe contour depicts the LV volume segmentation. The magenta and contour lines identify the long-axis plane that contains the mitral valve, apex and aortic valve. The vortical structures in purple are visualized by isosurfaces of λci (imaginary part of the complex conjugate eigenvalue of ∇υ).

FIGURE 2

Snapshots of 2-D intraventricular residence time along the cardiac cycle in a healthy heart (A) and in two different examples of dilated cardiomyopathy (NIDCM) patients (B & C). 1st row: Residence Time mapping at the mitral valve opening in the converged N-l cycle. 2nd row: Residence Time mapping at peak E-wave in the last computed cycle. 3rd row: Residence Time mapping at the iso-volumetric contraction in the last computed cycle. 4th row: Residence Time mapping at mitral valve opening in the last cycle. Notice that in both NIDCMs there coexist different regions with high Tr.

FIGURE 3

Snapshots of 2-D K and Tsbefore mitral valve opening in the last converged cardiac cycle in a healthy heart (A) and in two different examples of NIDCM (B & C). 1st row: Kinetic energy density (K) mapping in the regions with in the regions with TR > 2 s. 2nd row: Distortion time (Ts) in the regions withTR > 2 s. The NIDCM-2 case is at risk of apical blood stasis given the combination of low K and large Ts.

FIGURE 4

Snapshots of 2-D intraventricular residence time along the cardiac cycle in a patient before (A) and after (B) LVAD implantation. The apically located inflow LVAD cannula is represented in magenta. 1st row A: Residence Time mapping at the mitral valve opening in the converged N-l cycle. 2nd row: Residence Time mapping at E-wave peak in the last computed cycle. 3rd row: Residence Time mapping at the onset of isovolumic contraction in the last computed cycle. 4th row: Residence Time mapping at mitral valve opening in the last cycle.

FIGURE 5

Example of region tracking (A) and time evolution ofVTR (B), TM,2(C), KM,2 (D), TSM,2 (E) along the last converged cycle in all the 2-D studied cases: Healthy heart (1st col), NIDCM-1 (2nd col), NIDCM-2 (3rd col), Pre-VAD (4th col) and Post-VAD (5th col). Line colors correspond to each of the tracked regions (row A) and their average (black).