Measurement of Left Ventricular Ejection Time Utilizing the Derivative of the Ear Densitogram

A study was performed to investigate the validity of the derivative of the ear densitogram for measurement of left ventricular ejection time (LVET) .Nine male college students performed bicycle exercise at an initial work load of 0 watt (W), subsequently increasing by 60W every 3 min up to 240W. The LVET derived from the derivative of the ear densitogram (LVETe) was compared with that derived from the carotid pulse wave (LVETc) obtained at the same time.The results were as follows:1. There was a high correlation coefficient, r=0.987 (P<0.01), between LVETe and LVETc.2. At rest, LVETe showed a tendency to coincide with LVETc. In contrast, LVETe became longer than LVETc during exercise, and the higher HR became, the larger the difference between the two.3. In the individual regression equations between LVETe and LVETc, the slopes and the intercepts were nearly identical.4. The following equation was proposed for the correction of LVETe during exercise. LVET=-0.147⋅HR+ LVETe+ 8.3From these findings, it was concluded that the validity of the derivative of the ear densitogram for estimation of LVET is sufficiently high. LVETe at rest is valid for the estimation of LVET without correction. During exercise, however, LVETe shows a tendency to be longer than LVETc, and thus it is desirable to correct LVETe using the above equation.