1 Department of Pediatrics (Cardiology), New Jersey Medical School, 100 Bergen St, Newark, NJ 07103
To the Editor.
In the multicenter echocardiographic study of premature infants reported by Johnson et al,1 the measurement of aortic root dimension is shown in their figure 1 as inner-to-inner echoes. The recommendation of the American Society of Echocardiography, as reported by Sahn et al2 is for an outer-to-inner (ie, leading edge) measurement. In small premature infants with aortic root dimension of approximately 6 mm, such a measurement difference may amount to 1 to 2 mm, and will lower the normal left atrial to aortic root ratio (LA:Ao) to less than unity as compared with the value of 1.1 or higher reported by Johnson et al.