Fig. 1

LV velocity vector plots from a healthy volunteer and a PH patient at four time points in the cardiac cycle (indicated by the ECG trace). The line colors represent longitudinal velocities: blue or yellow/red represent myocardial motion towards or away from the apex respectively. The line orientation and length represents the vector sum of the radial and tangential velocities. Note the biphasic tangential systolic (S1 and S2) and early diastolic (E1 and E2) motions. In health, this follows an anti-clockwise then clockwise motion in systole and diastole. In PH, however, there is reversal of early diastolic tangential untwisting directions: clockwise untwisting occurs prior to anti-clockwise untwisting