Value of M-mode echocardiography for non-invasive diagnosis of Ebstein's anomaly.
M-mode echocardiographic studies were performed in 11 patients, most of them adults, with Ebstein's anomaly of the tricuspid valve, proven by cardiac catheterisation. Simultaneous recordings of the tricuspid and mitral valves were obtained in all cases, the transducer position being outside the left midclavicular line in seven patients. Tricuspid valve closure followed mitral valve closure in all cases, with an interval ranging between 0.04 and 0.14 s. Since, in more than 8500 routine echocardiographic studies a valve closure interval between 0.09 and 0.12 s was seen in only one patient without Ebstein's anomaly, an interval of 0.065 s or more should be regarded as diagnostic of Ebstein's disease; however, an interval shorter than 0.065 s does not exclude this diagnosis. In all patients a paradoxical septal movement was found. Two patients showed an atypical three-peaked diastolic pattern of movement of the anterior tricuspid leaflet and one patient also showed mitral valve prolapse. Pathological tricuspid valve closure delay, shown by echocardiography, makes it possible to diagnose Ebstein's anomaly in many cases without resort to cardiac catheterisation which has a relatively high risk in this disease.