This study clarified the relationship between right ventricular (RV) overload and contraction of the interventricular septum using two-dimensional echocardiography. Seventeen patients with atrial septal defect (RV systolic pressure: 36 +/- 14 mmHg), 13 with mitral stenosis (49 +/- 19 mmHg), nine with primary pulmonary hypertension (87 +/- 21 mmHg) and 17 normal subjects (23 +/- 3 mmHg) were evaluated using two-dimensional echocardiography and cardiac catheterization. The circumferential lengths of the septum (Civs) and the left ventricular (LV) free wall (Cfw) were measured in the LV short-axis view at the level of the papillary muscles. In normal subjects, Civs was 3.4 +/- 0.5 cm and Civs/Cfw was 0.40 +/- 0.07. All patients with RV overload had longer Civs and greater Civs/Cfw as compared with the normal subjects. There was no significant difference in the Cfw among the cases with mitral stenosis and primary pulmonary hypertension and the normal subjects. Cfw in atrial septal defect was shorter than in the normal subjects. The percent contraction of Civs was decreased in mitral stenosis and primary pulmonary hypertension as compared with the normal subjects. No significant difference was found in the percent contraction of Civs between the normal subjects and the 11 patients with atrial septal defect with normal RV systolic pressure. However, in six patients with atrial septal defect with high RV systolic pressure, the percent contraction of Civs was decreased. There was an inverse correlation between RV systolic pressure and the percent contraction of Civs (r = -0.39, p less than 0.01), and RV ejection fraction (r = -0.52, p less than 0.01) defined by multiplegated equilibrium scintigraphy.(ABSTRACT TRUNCATED AT 250 WORDS)