In the case of a sufficiently strong impact, the upstroke of the PSN can reach positive values, called a post-systolic motion.6),7),8),9),10),11),12) We propose this simple mechanism to explain the biphasic configuration of the post-ejection velocity spike. Previous research had suggested it to be a resultant of different phenomena such as: asynchronous Inhibitors,research,lifescience,medical contraction and ventricular interdependence,13) asynchronous deformation of subendocardial and subepicardial LV wall layers14) and tug-of-war between weak and strong segments during the isovolumic relaxation phase.15) The prevalence of the positive PSN velocities found in the current study is somewhat higher than previously reported,3) Inhibitors,research,lifescience,medical probable
because no temporal averaging of the measurement results was applied. The centrifugal propagation of the positive PSN velocity front is illustrated by a frame-by-frame analysis of a color TDI sample (Fig. 6). Fig. 6 The typical sequence of the centrifugal distribution of the apically directed velocity of the myocardium (red-colored area) following the aortic valve closure. Four consecutive images are shown. Panel A corresponds to the post-systolic velocity notch … To the best of our knowledge the present study describes for the first time the existence of two PSN spikes with apically
directed acceleration. This was possible due to use of the high frame rate and non-smoothed Inhibitors,research,lifescience,medical measurement results. Inhibitors,research,lifescience,medical While the origin of the first PSN spike is as discussed above, probably, the closure of the aortic valve, the genesis of the second PSN spike is less clear. We hypothesize that the sudden cessation of the aortic backflow at the instant of the aortic valve closure16) is a potential mechanism behind the second PSN spike. The transmission
of the kinetic energy could be sufficient to cause an acceleration of adjacent structures in the direction of the left ventricle.17) The magnitude of the retrograde flow in the Inhibitors,research,lifescience,medical ascending aorta is known to vary significantly between the Ruxolitinib in vitro healthy subjects and constitutes 4-29% of the antegrade aortic flow. At an average of 600-700 mL/min retrograde flow the coronary circulation takes 200-300 mL/min, the remainder turns around in the sinuses of Valsalva.18) The maximal velocity of the retrograde flow in the ascending aorta is in the range of 8-40 cm/s in healthy subjects.19) These differences in velocity and volume of the retrograde aortic flow are likely to cause a wide spectrum of velocity and duration of found the second PSN spike. Further studies are needed to elucidate its nature and clinical significance. Limitations The apical longitudinal axis view is hampered by suboptimal alignment of the Doppler interrogation with longitudinal motion of the ascending aorta which varies with the magnitude of the aorto-septal angle. However, it is unlikely that possible malalignment influenced the timing intervals measured in this study.