[Detection of right-to-left shunt flow in atrial septal defect using transesophageal color and pulsed Doppler echocardiography].

The clinical significance of right-to-left (R-L) shunt flow dynamics in atrial septal defects (ASD) were investigated using transesophageal color and pulsed Doppler echocardiography in 30 patients with ASD of the ostium secundum type, including 20 with systolic pulmonary artery pressures (sPA) less than 40 mmHg, 4 with sPA of 40 to 60 mmHg, 3 with sPA of 90 mmHg or greater, 2 with pulmonic stenosis and 1 with Ebstein's anomaly. R-L shunting was detected by a shunt flow signal across the defect during a cardiac cycle. The timing of the R-L shunt was compared with various parameters obtained by echocardiography or cardiac catheterization. R-L shunt flow at the onset of ventricular contraction or closing phase of the tricuspid valve was detected in five patients with isolated ASD associated with increased mean right atrial pressure, but no severe pulmonary hypertension. R-L shunt flow during systole was detected in five of 26 patients with isolated ASD and tricuspid regurgitation and in one patient with Ebstein's anomaly. The tricuspid regurgitation signals in three of the five patients were directed toward the defect, while the other two had massive tricuspid regurgitation. R-L shunt flow during mid-diastole was detected in three patients without pulmonary hypertension. Massive left-to-right shunt flows occurred during the phase from end-systole to early diastole. R-L shunt flow during atrial systole was detected in three patients with severe pulmonary hypertension and two with pulmonic stenosis. The severe pulmonary hypertension patients, in particular, showed the aliasing signal as a high speed shunt flow, and in two of these, R-L shunt flow continued from atrial systole to early ventricular systole, and was also observed in early diastole. R-L shunt flow was detected in ASD patients with and without pulmonary hypertension, and was influenced by right atrial pressure at the phase of tricuspid valve closing, volume or direction of tricuspid regurgitation, rebound flow due to massive left-to-right shunt flow, grade of right ventricular distensibility or pulmonary hypertension, and other cardiac complications.