Effect of flow disturbances remaining at the beginning of diastole on intraventricular diastolic flow and colour M-mode Doppler echocardiograms

Abstract

A computational model of the fluid dynamics of intraventricular flow was used to investigate the importance of the effects of flow disturbances existing within the left ventricle (LV) at the onset of diastole on a diastolic flow field. The simulation started with a quiescent flow state; it continued for a number of cardiac cycles to obtain a cyclically repeatable flow. After the flow became periodic, the initial diastolic flow was not quiescent: flow disturbances, remnants of a systolic flow, were present within the LV. Nevertheless, they faded away during an acceleration phase of diastole and almost ceased by the end of this phase. Consequently, a flow field during a deceleration phase of diastole, characterised by the formation of a vortex ring, was hardly affected by the initial flow disturbances. The propagation velocity of a colour M-mode Doppler echocardiogram obtained by scanning velocity along the LV long axis was 0.58 m s(-1) in the case where diastolic flow was initially quiescent and 0.56 m s(-1) in the case where flow disturbances existed at the beginning of diastole. These results indicated that the colour M-mode Doppler echocardiographic technique captures flow dynamics produced purely by ventricular expansion, with little influence from initial diastolic flow disturbances.

Analysis of Flow Within a Left Ventricle Model Fully Assisted With Continuous Flow Through the Aortic Valve

“…The ventricle shape was simplified by using the method proposed by Nakamura et al. (10,11). The configuration of the LV model is shown in Fig.…”

“…The computational model of the LV was constructed using computer-aided design software (Pro/ ENGINEER, PTC Japan,Tokyo, Japan).The shape of the ventricular cavity was assumed to be a bended tube having a continuously changing cross section. The ventricle shape was simplified by using the method proposed by Nakamura et al (10,11). The configuration of the LV model is shown in Fig.…”

Doppler vortography - Detection and quantification of the vortices in the left ventricle

“…It is worth mentioning that the mitral vortex is stretched during systolic contraction and is ejected and disappears almost completely before the onset of diastolic filling. Therefore, the remaining vorticity from the previous cycle weakly affects the mitral inflow vortex and the diastolic flow can be considered vortexfree before the beginning of ventricular filling [72,135]. …”

Computational Blood Flow Analysis -New Trends and Methods

“…They discussed the relationship between the growth of an intraventricular vortex and a Doppler-derived clinical index for left ventricular diastolic function, the so-called "flow propagation velocity," and provided the fluid mechanical basis of this index. Their subsequent analysis of the utility and limitations of this index showed that the flow propagation velocity was not sensitive to flow disturbances remaining from systole (93) and to ventricular untwisting (94) . Nakamura et al also addressed the importance of the opening mode of the mitral valve orifice on vortex formation within the left ventricle during diastole (95) and showed that the vortex structure affected left ventricular flow ejection into the aorta (96) .…”