Pulsed Doppler echocardiography combined with two-dimensional echocardiographic (2-DE) system was performed to detect a shunt flow through a defect in the interatrial septum (IAS) in patients with secundum atrial septal defect (ASD) utilizing right parasternal approach (RPA). RPA is a method which provides an accurate evaluation of a defect in the IAS on a 2-DE image by placing a transducer on the right of the sternum because the ultrasonic beam passes in a plane almost perpendicular to the IAS. The subjects consisted of 20 patients with ASD (25 +/- 22 yrs) diagnosed by cardiac catheterization or 2-DE with peripheral contrast material injection, and 10 cases of healthy subjects (34 +/- 18 yrs). Defects in the IAS were clearly visible in 19 patients with ASD on 2-DE images by RPA. By placing the sample volume in the center of the defect, Doppler flows could be obtained in 17 of them. In 13 with sinus rhythm, except a case of Eisenmenger syndrome, Doppler signals showed mainly a laminar flow toward the transducer (positive flow), but a transient flow of low velocity away from the transducer (negative flow) was also observed. The positive flow had its peaks in late systole and atrial systole and occasionally in mid-systole, early diastole and mid-diastole. The negative flow occurred in early systole, mid-diastole and late diastole. In a patient with Eisenmenger syndrome and tricuspid regurgitation (TR), a negative turbulent flow was observed from early systole to mid-diastole. In three patients with atrial fibrillation, Doppler signals were variable. The Doppler echogram of a patient with atrial fibrillation but no complication showed a laminar positive flow with its peaks in late systole and mid-diastole, and a negative flow in early systole. One patient with atrial fibrillation and TR had a systolic negative turbulent flow and a mid-diastolic laminar positive flow. In a patient with TR and mitral regurgitation, the Doppler echocardiogram showed a laminar positive flow throughout the entire cardiac cycle with its peaks in early diastole and mid-diastole. Doppler signals from the left atrium (LA) to the right atrium (RA) through a defect coincided in timing with the appearance of negative contrast echo from the defect to the RA on 2-DE image and signals from the RA to the LA coincided with the appearance of the contrast echo into the LA from the RA through the defect. Doppler signals disappeared after the closure of the defect in all six patients examined.(ABSTRACT TRUNCATED AT 400 WORDS)