Role of M mode echocardiography in congenital aortic stenosis

M mode ultrasonic recognition of a bicuspid aortic valve or congenttally stenotic aortic valve rests on detection of the following criteria: eccentricity index, increased leaflet thickness, multiple diastolic cusp lines and presence of a central systolic line. In this investigation, M mode ultrasonic tracings from 118 children were interpreted by evaluators who did not know the diagnosis. Twenty-eight records from children with aortic valve stenosis (25 with a bicuspid valve and 3 with a tricuspid valve), were intermixed with records of 90 children with a catheterization-proved normal aortic valve to determine how many criteria were present in each tracing. Additionally, tracings were reviewed for overall visual appearance of the criteria, without measurement, to attempt to identtty those with an abnormal aortic valve. Finally, all echoes were viewed simultaneously and ranked from the most normal in appearance to the most abnormal aortic valve image. Rankings were then compared with measured pressure gradients across the aortic valve.

An eccentricity index value greater than 1.5, thought to be indicative of a bicuspid aortic valve, was found in 29 percent of patients with aortic stenosis and 20 percent of normal children. Mean eccentricity index values for the two groups were statistically similar. Increased leaflet thickness was not detected in any tracing. Multiple diastolic cusp lines were present in 64 percent of patients with aortic stenosis and 60 percent of normal children. None of these criteria were sensitive or selective for dlagnosing aortic stenosis from an M mode tracing of a given patiënt. On the basis of subjective visual appearance, 39 percent of tracings of patients with aortic stenosis were identified correctly. No useful correlation existed between the ranking an M mode tracing received for degree of valve normality or abnormality and the aortic pressure gradient. This investigation shows that M mode echocardiography of the aortic valve, despite prior recommendations to the contrary, has limited usefulness in diagnosing congenital aortic stenosis.