Biphasic hemodynamic effects of LDL-apheresis in common carotid artery

Heparin-induced Extracorporeal Low Density Lipoprotein Precipitation (HELP) Apheresis gives beneficial reductions in Low Density Lipoprotein (LDL) cholesterol levels; otherwise, extracorporeal circulation settings might elicit inflammation and platelet aggregation. The net effect of these variations on carotid hemodynamic has not been established. Aim of the present study was to investigate periprocedural variations of common carotid artery wall shear stress, circumferential wall tension, and Peterson's elastic modulus.

Measurements were sequentially performed on 22 procedures: immediately before apheresis (T1), within one hour after (T2), after 24 (T3) and 48 hours (T4). In order to confirm acute effects, in additional 30 procedures measurements were performed at T1 and T2.

Mean shear stress was decreased at T2, with an improvement at T4. Mean circumferential wall tension showed an improvement at T4; arterial stiffness showed the same trend, but only close to statistical significance. The following 30 procedures, where measurements were performed at T1 and T2 only, confirmed previous results, showing a deep wall shear stress decrease at T2 (-21%).

LDL apheresis seems to have a biphasic effect on common carotid hemodynamics: the acute worsening of shear stress, probably mediated by extracorporeal circulation, was followed by its improvement, possibly driven by LDL cholesterol reduction.