[An experimental study on the relationship between interventricular septal echograms and interventricular pressure gradient].

To evaluate the correlation between the configuration and motion of the interventricular septum (IVS) and the interventricular pressure gradient, six closed-chest dogs were studied. M-mode and two-dimensional echograms, the left (LVP) and right ventricular pressures (RVP), the interventricular pressure gradient (LVP-RVP), phonocardiograms in the left and right ventricles and electrocardiograms were simultaneously recorded. The RVP was gradually elevated by injecting Lycopodium in a peripheral vein. In all six dogs, there were good correlations between the curvature of the IVS and the interventricular pressure gradient in end-systole and in end-diastole. In M-mode echograms of the IVS, three dips were recognized in early diastole (isovolumetric relaxation period, D1 dip), in late diastole (atrial kick, D2 dip) and in early systole (isovolumetric contraction, S1 dip) when the RVP was elevated. Three negative dips on interventricular pressure gradient curves were observed to occur simultaneously with D1, D2, and S1 dips, respectively. A D1 dip was demonstrated in all six dogs, a D2 dip in four dogs, and an S1 dip in six dogs. In conclusion, the curvature of the IVS reflects the change in the interventricular pressure gradients in diastole as well as in systole. D1, D2 and S1 dips in the IVS echogram also reflect changes in the interventricular pressure gradients.