This study clarified regional and global functions of the distorted left ventricle due to right ventricular overload by means of gated radionuclide ventriculography (RNV). Cardiac catheterization and RNV were performed in 13 cases of atrial septal defect (ASD), 13 of pure mitral stenosis (MS), 10 of primary pulmonary hypertension (PPH), and 10 of normal subjects (NL). Right ventricular systolic pressure (RVSP) was 32.9 +/- 13.9, 45.0 +/- 12.2, 88.3 +/- 17.1, and 21.2 +/- 4.5 mmHg, respectively. RNV was performed with a 99mTc-red blood cell in a vivo labeling technique. The end-systolic LAO view of the left ventricle was halved into septal and free-wall sides. The end-diastolic halves were determined in the same plane. Ejection fractions of the global left ventricle (LVEF), global right ventricle (RVEF), the septal half of the left ventricle (SEPEF), and the free-wall half of the left ventricle (FWEF) were obtained. LVEF was 56.8 +/- 9.8% in NL, 52.8 +/- 10.5% in ASD, and 49.5 +/- 12.9% in PPH. In MS, LVEF (47.0 +/- 13.0%) was smaller than those in the other groups. RVEF was 37.0 +/- 5.2% in NL, 43.7 +/- 15.5% in ASD, and 32.8 +/- 11.5% in MS. In PPH, RVEF (25.0 +/- 10.6%) was smaller than those in the other groups. SEPEF was smaller in AS D (42.5 +/- 13.2%), MS (40.4 +/- 13.1%), PPH (40.5 +/- 12.5%) than in NL (53.5 +/- 8.5%). Systolic function of the septal half of the left ventricle was disturbed by right ventricular overload. RVEF (r = -0.35, p less than 0.05) and SEPEF (r = -0.51, p less than 0.01) had negative correlations with RVSP. As RVSP rose, systolic function of the septal half of the left ventricle was more severely disturbed. FWEF was the same among the four groups; NL (57.0 +/- 12.6%), ASD (48.6 +/- 15.2%), MS (50.5 +/- 12.0%), and PPH (51.1 +/- 12.3%). Right ventricular overload does not affect systolic function of FWLV. There was a good correlation between SEPEF and LVEF in NL (r = 0.81), though in PPH this correlation was poor (r = 0.64). In patients with PPH the septal side of the left ventricle does not act as a part of the global left ventricle. Systolic function of the septal side of the left ventricle is disturbed due to the distortion of the ventricular septum, but systolic function of the free-wall side is maintained within a normal range, when the left ventricular myocardium is kept normal.(ABSTRACT TRUNCATED AT 400 WORDS)