抄録
The phases of the left heart cycle have been measured in athletes at rest and during exercise utilizing vibrocardiographic and electrocardiographic data. Six periods were studied which corresponded to electromechanical lag, isometric contraction, ejection, isometric relaxation, rapid filling, and diastasis. These periods were compared with the total length of the left heart cycle at heart rates ranging from 50 to 200 beats per min. The range of these intervals was such that the duration of any cardiac phase could be predicted from ventricular cycle length.
The 6 periods of the left heart cycle all diminished linearly with cycle length up to heart rates of 160. After this level, the electromechanical lag and isometric contraction periods remained unchanged, the ejection period short-ened more markedly, and the isometric relaxation and rapid filling periods did not change. The period of diastasis demonstrated a marked shortening and was found to be completely eliminated above heart rates of 160. It was suggested that a physiologic limit of heart rate is achieved near this level.
