CRT超声优化.ppt

Late activation of the left ventricle leads to increasing left ventricular systolic pressures at a time well after the interventricular septum has finished repolarizing. This late ventricular activation occurring as the septum has begun repolarizing, causes, not only a decreased septal contribution to stroke volume, but also septal dyskinesis, in which the septum moves away from the left ventricular wall during LV contraction. This is evidenced in the M-mode sample at left. Simultaneous activation of the ventricles allows ejection to occur in both ventricles prior to repolarization of the septum, as seen in the echo images. Toussaint et al. Biventricular Resynchronization in End-Stage Heart Failure: An Eight-Months Follow-up by Phase Map Radionuclide Angiography. PACE 1999; 22[4, Part II]:840, Abstract 561. Using Radionuclide Angiography (RNA) in 8 HF pts, NYHA III or IV, QRS120 ms, EF of 20±6% to assess mechanical resynchronization with BiV pacing at 8 days and 8 months post-implant. Global desynchronization time between RV and LV remained the same after 8 days and decreased significantly after 8 months. Regional desynchronization time decreased significantly at both follow-ups. The apex to base activation pattern was inverted with BiV pacing, and LVEF was the same at day 8 but increased significantly after 8 months. Curry C, Fetics B, Wyman B, McVeigh E, Kass D. Mechanical dyssynchrony at rest and with adrenergic stimulation in patients with dilated cardiomyopathy studied by MRI-tagging: Can it help identify candidates for chronic VDD pacing therapy? Circulation 1998; 98[17]: I-302 ( AHA abstract 1578). Tagged MRI images were taken before and after dobutamine in 5 DCM pts with ventricular dyssynchrony who were LV paced acutely, and compared with 7 controls. DCM pts were VDD paced at the site of delayed activation. Mechanical dyssynchrony was improved with VDD pacing, and basal dyssynchrony persisted with adrenergic stimulation of dobutamine, supporting poten