Abstract 19124: Influence of Right Ventricular Pacing on Left Ventricular Early Diastolic Radial Lengthening and Left Atrial Conduit Function
Background: The apex-to-base mechanical activation sequence of left ventricle (LV) is important determinant of LV diastolic performance. LV radial lengthening during early diastole functions as suction and relates to left atrial (LA) conduit function in normal subjects. Although right ventricular (RV) pacing causes LV electro-mechanical dyssynchrony, the behavior of LV apical and basal diastolic lengthening during RV pacing and its relation to interaction of LV diastolic property and LA function during LV early diastole are unknown.
Method: We studied 21 patients with RV pacing (RVP) and 15 healthy volunteers (N). Time-volume and its first derivative curves of LA were obtained from apical view by biplane Simpson's method using 2D tissue tracking system (2DTT:EUB-7500, Hitachi, Japan). The peak value of first derivative curve during LV early diastole was obtained and corrected by maximum LA volume (dV/dtE). The basal and apical LV short-axis views were also obtained. Eight equiangular points on endo-myocardium at end-diastole were placed in each view, and the movements of these points were automatically tracked by 2DTT. The shortening ratios of four directions were calculated and averaged. Then, the time-LV shortening and lengthening curves were obtained. The time intervals from the aortic valve closure to the point of the first 40% of peak lengthening (T40) were measured in both basal and apical short-axis views (basal T40 and apical T40, respectively) (Figure A).
Results: Although there were no differences in basal T40 between two groups, apical T40 in RVP was longer than that of N (184±36 vs 118±25msec, p<0.01). The dV/dtE had good linear correlation to apical T40 (r=0.66, p<0.01), but not to basal T40 (figure B).
Conclusion: These results suggested that apical T40 was closely related to LA conduit function. RV pacing caused to delay LV apical lengthening during early LV diastolic phase and consequently might attenuate LV diastolic suction and LA conduit.
- © 2010 by American Heart Association, Inc.