PMC

Standard used for myocardial strain, mitral valve inflow velocity and longitudinal pressure gradient segmentation in the four-chamber view, reproduced according to the American Society of Echocardiography’s Guidelines.

Schematic depicting the relative number of emitter particles released at each time frame during rapid filling. The number of particles released at a given time frame is proportional to the area under the mitral inflow velocity curve at that time frame. The inflow velocity curve is obtained by averaging the velocity in the circled area illustrated in the insert.

Color-coded blood velocity maps with myocardial tag overlay for fifteen continuous representative time frames during early diastolic filling obtained in the four-chamber view with a high frame rate of 14 ms. Data was obtained from a normal volunteer in a single breath-hold SPAMM-PAV acquisition.

Overlapped pathline trajectories for (a) a normal baseline dog, (b) a representative infarcted dog with nominal flow dysfunction, and (c) a representative infarcted dog with severe flow dysfunction. A large vortex is observed around the mid-basal region of the septal wall in (b) depicting a compensatory accentuated filling pattern and nominal flow dysfunction as compared to baseline. In (c), the filling pattern is severely impaired and depicts shortened centric filling towards the apex, and stagnation in the basal regions (severe flow dysfunction).

Time plots comparing the mean of longitudinal strain in basal, mid-cavity, and apical regions of septal and lateral walls during early diastole, in normal volunteers (a and b), normal baseline dog (c and d), a representative infarcted dog with nominal flow dysfunction (e and f), and a representative infarcted dog with severe flow dysfunction (g and h). The strain pattern in the baseline dog is close to the normal volunteers. The dog with nominal flow dysfunction exhibits decreased strain in the apical region on the septal wall, while the dog with severe flow dysfunction exhibits decreased strain in the apical and mid regions on both the septal and lateral walls. Mitral valve inflow velocity curve is superimposed as a temporal reference.

Longitudinal pressure gradient time curves during rapid filling, averaged in ten regions defined along the central long-axis, as shown in , for (a) a normal volunteer, (b) a normal baseline dog, (c) a representative infarcted dog with nominal flow dysfunction, and (d) a representative infarcted dog with severe flow dysfunction. The left sub-figure of each case illustrates the relative position of the investigated regions with the pathlines. Case (a) and (b) exhibit a regular pattern and variation of regional pressure gradient with time, while case (c) and (d) show irregular patterns and regional variations. Mitral valve inflow velocity curve is superimposed as a temporal reference.

The net kinetic energy for each set of pathlines during the rapid filling phase (temporally scaled and resampled) for the normal volunteers represented by black (■) with standard deviation, a baseline dog represented by light grey (●) and six infarcted dogs, respectively represented by red (●), blue (♦), green (▲), cyan (●), purple (♦), and orange (▲), where the former three are the infracted dogs with nominal flow dysfunction and corresponds to dogs1, 2 and 3, shown in , and the latter three are the infracted dogs with severe flow dysfunction, corresponding to dog 4, 5 and 6 in . The large vortex present in dogs with nominal flow dysfunction may contribute to the increase in the net kinetic energy, while the reduced filling observed in the dogs with severe flow dysfunction may contribute to the decrease in the net kinetic energy.

(a) Time series (row1: acceleration, row 2: deceleration) of particle traces emitted from the mitral valve plane in a normal volunteer, color-coded to depict instantaneous kinetic energy. The number of blood particles, represented by the red circles, emitted at each time frame is determined by the area under the velocity curve at each time interval as shown in . The red dots on the pathlines, shown on the top left sub-figure, illustrate the position of the emitter particles (released at the first time frame) at each subsequent time frame as it propagates into the LV chamber. A wavefront like propagation is observed. (b) Overlapped particle trace trajectories of emitter particles released at all time points in a normal volunteer. Blood propagating into the left ventricle at an early stage distributes uniformly throughout the left ventricle, while blood entering at later time frames contributes to a more centric filling (away from the walls and the apex).