Damien Garcia (1), Juan Carlos del Ãlamo (2), Cristina Cortina (1), Raquel Yotti (1),. David Tanné (3), Ãric Bertrand (3), Miguel A. GarcÃa-Fernández (1),.
Cardiac Mechanics and Function
Presentation O-148
S151
FULL INTRAVENTRICULAR FLOW MAPPING BY CONVENTIONAL COLOR-DOPPLER ECHOCARDIOGRAPHY Damien Garcia (1), Juan Carlos del Álamo (2), Cristina Cortina (1), Raquel Yotti (1), David Tanné (3), Éric Bertrand (3), Miguel A. García-Fernández (1), Francisco Fernández-Avilés (1), Javier Bermejo (1)
1. Hospital Gregorio Marañón, Madrid, Spain; 2. University of California at San Diego, USA; 3. Team of cardiovascular biomechanics, IRPHE, Marseilles, France
Introduction Accurate quantification of left ventricular function is primordial in clinical decision making and follow-up assessment in patients with cardiovascular disease. Its ability to derive real-time noninvasive information makes Doppler ultrasound the cornerstone technique for cardiovascular diagnosis [Thomas, 2006]. Current color-Doppler ultrasound, however, is limited to the only components of the actual three-dimensional velocity field projected along the direction of the ultrasound beam. Computational [Pedrizzetti, 2005] and in vitro [Kheradvar, 2007] studies have suggested that more complete clinical diagnostic information could be derived from the full-field characterization of intraventricular flow. To date, the detailed visualization of full-flow in the left ventricle is only accessible with magnetic resonance velocimetry. The objective of our study was thus to develop and validate an original algorithm to construct a twodimensional time-resolved (2D+T) left ventricular flow field from conventional echocardiographic acquisitions.
Methods Color-Doppler images were acquired in the apical long-axis view. Two-dimensional flow mapping was reconstructed from Doppler velocities by means of the continuity equation. The inner left ventricular wall was automatically tracked and used as boundary conditions. To validate the method, simultaneous color-Doppler and laser particle image velocimetry (PIV) measurements were obtained in an atrio-ventricular duplicator under variable hemodynamic conditions. Echo-Doppler acquisitions were also performed in human subjects to demonstrate the applicability and the potential of the new technique in the clinical setting.
Results Agreement analysis on the in vitro experiments demonstrated that the proposed numerical processing method yields an accurate reconstruction of the 2D+T velocity and vortex mappings. Clinical measurements showed that E- and A-waves are both characterized by the formation of a strong
16th ESB Congress, Oral Presentations, Tuesday 8 July 2008
confined jet passing through the mitral jet that rolls up to feed a large vortex structure (Figure 1, left). The vortex ring generated by atrial contraction during late filling remains sustained during isovolumic contraction and facilitates blood ejection during early systole (Figure 1, right).
Figure 1: Full-flow mapping (m/s) in a normal subject. MV: mitral valve, AV: aortic valve.
Discussion and Conclusion We have developed an original method to display the 2D+T flow field inside the left ventricle. By digital processing conventional transthoracic colorDoppler sequences, 2D+T flow fields could be overlaid on grayscale anatomical images, allowing both visual and quantitative characterization of intraventricular flow features at a high temporal resolution. In comparison with magnetic resonance velocimetry, our novel echocardiographic method based on the continuity equation is fast, clinically compliant and does not require any specific training. Previously impossible to derive by ultrasound, this new modality could allow the study of a number of additional aspects of intraventricular flow dynamics in the clinical setting by fast processing conventional color-Doppler images.
References Thomas et al, JACC, 48:2012-2025, 2006. Pedrizzetti et al, Phys Rev Lett, 95:108101, 2005. Kheradvar et al, ASAIO J, 53: 8-16, 2007. Journal of Biomechanics 41(S1)
