The complementary roles of M-mode echocardiography and scintigraphy in the evaluation of adults with suspected left-to-right shunts. Additional observations on the role of two-dimensional echocardiography.

We sought to determine the relative clinical abilities and roles of echocardiography and scintigraphy in left-to-right shunt diagnosis. M-mode echocardiographic and scintigraphic studies were analyzed in 37 adults presenting diagnostic difficulties with suspected left-to-right shunts. The historic, physical, radiographic and electrocardiographic data were frequently ambiguous. An enlarged right ventricle on M-mode echocardiography was a sensitive (100%) but not specific (55%) indicator of atrial septal defect (ASD). M-mode lacked sensitivity for ventricular septal defect (VSD) and patent ductus arteriosus (PDA). In a few studies, two-dimensional echocardiography provided additional specific and clinically important anatomic information. Scintigraphic analysis demonstrated complete diagnostic accuracy and excellent localizing and quantitative abilities in all patients studied. Because it is extremely sensitive to ASD, free of any exposure to radioactivity, entirely noninvasive and may be simply and visually analyzed, echocardiography is the study of choice in the preliminary evaluation of patients presenting diagnostic difficulty with suspected ASD. Scintigraphy is the study of choice in the preliminary evaluation of patients presenting diagnostic difficulty with suspected VSD and PDA and is the logical response to the finding of echocardiographic right ventricular enlargement when the diagnosis remains in doubt.