Abstract
<h3>To the Editor.—</h3> I would like to make the following comments about the production of A2. Leatham<sup>1</sup>recorded phonocardiograms and external carotid pulse tracings in ten healthy persons and concluded that the origin of the first component of S2 is associated with aortic valve closure by its relationship to the dicrotic notch. Although the foregoing hypothesis has been generally accepted, several investigators have reported that the first component of S2 precedes aortic valve closure by 5 to 30 ms.<sup>2-4</sup> To clarify this controversy regarding the relationship between the aortic valve closure and the first component of S2, we conducted a study on 20 subjects (<i>Geriatrics</i>26: 372-374, 1978). Simultaneous phono-cardiograms, ECGs, and echocardiograms were recorded on a strip-chart recorder. The points of separation and closure of the echoes of the two cusps of the aortic valve were considered to be the aortic opening and closing points, respectively. The
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