To pulse or not to pulse

The purpose of a pulsatile flush, or push-pause flush, isn't to break off clots. When you flush through a line, particularly against back pressure, laminar flow will occur with the most flow occurring in the center of the lumen and flow towards the walls of the lumen decreasing until near the wall there is actually no flow at all. Using a pulsatile flush allows the solution that is not in the center of the lumen to move towards the center through diffusion each time the flow is paused, which then allows it to be flushed down stream. This is particularly important in valved catheters, which is why valved catheter manufacturers specifically recommend a pulsatile flush.

Unfortunately you usually don't get to see what your flush is doing, so it's hard for people to visualize the differences between a constant flush and a pulsatile flush. Transduced lines with VAMPS are great ways to see the differences between the two. If you ever get the chance to draw blood off of a VAMP, try flushing it both ways, the difference will be pretty obvious.

The point is to achieve turbulent flow inside the catheter instead of laminar flow, the only variable of which you have any control is the velocity of the flush... above a certain velocity (Google Reynolds number if you're particularly interested), the flow will be turbulent. The reason for the pulsatile flow is abrupt pressure differentials that occur during the change from laminar flow to turbulent flow.

Regarding your rationale, consider the relative pressure and volume differences between the heart and the flush... the flush is just signal noise by comparison.