Right ventricular volume loading in dogs reduced the mean transseptal end-diastolic pressure gradient from 2.1 to -2.6 mm Hg (p<0.001), causing a leftward shift of the interventricular septum.
Does the end-diastolic transseptal pressure gradient influence ventricular septal position and motion in an open-chest dog model?
Changes in the end-diastolic transseptal pressure gradient directly correlate with shifts in interventricular septal position and paradoxic motion.
p-value: p=<0.001
Despite the clinical prevalence of paradoxic interventricular septal (IVS) motion, its pathogenesis remains unclear. To assess the influence of the end-diastolic transseptal pressure gradient, we studied eight open-chest dogs during right ventricular (RV) volume loading (induced by opening a Dacron shunt between the pulmonary artery PA and right atrium), RV pressure loading (constriction of PA), and left bundle branch block (RV pacing). Ultrasonic crystals in the IVS and on the RV and left ventricular (LV) free walls (FW) allowed measurement of RV septal-to-free wall (S-FW) and LVS-FW diameters. Another set measured the anteroposterior (AP) diameter of the LV (LVAP). Two-dimensional and M mode echocardiograms confirmed IVS shape and motion pattern, respectively. RV volume load caused a reduction in mean transseptal end-diastolic pressure gradient from 2.1 to -2.6 mm Hg (p less than .001), with a concomitant increase in mean end-diastolic RVS-FW diameter of 2.5 mm (p less than .001) and a decrease in LVS-FW diameter of 2.8 mm (p less than .001). LVAP was unchanged. Echocardiograms confirmed a leftward IVS shift during diastole with paradoxic systolic motion. PA constriction and RV pacing caused similar directional changes in transseptal end-diastolic pressure gradients and diameters. Compared with control values, shunt opening and PA constriction also caused a small leftward shift of IVS at end-systole. Normalized data from all eight dogs revealed significant (p less than .001) correlations between reduction in LV-RV end-diastolic pressure gradients and increases in RVS-FW (r = .85) and decreases in LVS-FW (r = .80) diameters.(ABSTRACT TRUNCATED AT 250 WORDS)
Kingma et al. (1983) studied Paradoxic interventricular septal motion (n=8). Right ventricular volume loading, pressure loading, and pacing vs. Baseline/control values was evaluated on Transseptal end-diastolic pressure gradient and septal-to-free wall diameters (p=<0.001). Right ventricular volume loading in dogs reduced the mean transseptal end-diastolic pressure gradient from 2.1 to -2.6 mm Hg (p<0.001), causing a leftward shift of the interventricular septum.
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