Influence of acute increase in aortic impedance on left ventricular regional wall motion during early ejection period

To examine the effects of aortic (Ao) impedance (Z/sub c/, measured at 2-12 Hz) on LV regional systolic wall motion, measured ascending Ao flow (AoF), pressures of both LV (LVP) and Ao(AoP), and systolic segmental excursion (SE) in LV basal (B) and apical regions (A) in eight open-chest dogs. They also measured the changes of AoP ( Delta P), AoF ( Delta F) and SE in both B ( Delta Bx) and A ( Delta x) from 10 to 30 ms after the onset of ejection, and obtained the Delta P/ Delta F ratio during this period. Linear correlation was observed between Z/sub c/ and Delta P/ Delta F. During relatively tight construction of the aorta, Delta Ax was significantly reduced, but the percentage change of total SE in A and B, and Delta Bx, were unchanged. An inverse linear correlation was observed between Z/sub c/ and Delta Ax. Thus, a nonuniform response of LV regional wall motion was induced between basal and apical regions by acute alteration of Z/sub c/. >