To the Editor.
—The article entitled "Echocardiographic Systolic Time Intervals" by Chilton and colleagues, in the Archives (140:240-243, 1980), lends further support to our work,1 as well as that of Sakamoto et al,2 on the same subject. A more detailed version of this work was presented at the International Conference on Systolic Time Intervals held in Austria in 1978. The complete work of this symposium containing the reports of several experts in the field—Spodick, Weissler, Kesteloot, Zoneraiche, and others of equally high caliber—has recently been published.3 For the purpose of calculating systolic time intervals (STIs) from the echocardiogram, the authors presume that the aortic closure point by the echocardiogram coincides with the point of aortic valve closure of the phonocardiogram (referred to as 2A or A2). Although this point has been disputed by Sakamoto, our study clearly showed that the 2A of the phonocardiogram coincides exactly (±