[Ventricular interdependence reflected in interventricular septal motion: with special reference to right ventricular pressure overload].

Abstract

The dynamic features of the interventricular septum were studied with two-dimensional echocardiography with special reference to the influence of right ventricular (RV) pressure overload. The subjects were 52 patients, including 30 with atrial septal defect (ASD), 14 with rheumatic mitral valvular disease and 8 with pulmonary hypertension (PH) due to cor pulmonale, pulmonary embolism, or primary PH. To assess septal motion, the configuration of the left ventricle (LV) in the short-axis view was quantified as the deformity index, and characterized as the distortion from right circle. As an accurate short axis was required to assess the deformity of the cavity, the transducer was attached to the guide arm, providing comparable positions and directions. The deformity index was highest at the chordal level among other levels in the same cardiac phase. In ASD without PH, the deformity was minimal in end systole and maximal in early diastole. The index curve showed two peaks in early diastole and these times coincided with those of the minute backward notches on the ventricular septal echogram. In ASD with PH, the deformity was minimal in early systole and became greater during systole. The maximum deformity was shown in early diastole, corresponding to the momentary retracting motion of the septum by M-mode echocardiography. At that moment, the septum became convex to the LV. In patients with RV pressure overload, the systolic peak of the RV pressure was delayed and the decrease in pressure became sluggish, resulting in the RV pressure exceeding that of the LV transiently in early diastole. This was the reason for the septum becoming convex to the LV in this phase. Among the patients, the bi-ventricular systolic pressure ratio correlated not only with the index in end systole but also with that in early diastole. Good correlation between systolic pressure ratio and early diastolic deformity index seemed to be attributable to the fact that the higher the RV systolic pressure, the larger the reversed pressure gradient between both ventricles in early diastole.(ABSTRACT TRUNCATED AT 400 WORDS)