Measurement by systolic time intervals (STI) of cardiac responses requires extremely careful recording during actual stress test performance. Previous work indicated no significant changes in the pulse transmission time (PTT) during exercise and other challenges. Since external STI depend on the carotid pulse offset by the PTT as an aortic curve equivalent, stable PTT implies that timing of the carotid upstroke (CARu) and the carotid incisura (CARIN) would respectively track the pre-ejection period (i.e., the externally calculated onset of the aortic upstroke) and the aortic incisura which is externally timed by the aortic component of SII (IIA). In ten subjects, STIs were recorded at supine rest, sitting, standing, during prompt and sustained squatting and during isometric and dynamic exercise. The results demonstrated the tracking of both points: regression slopes and correlation coefficients were close to 1.00 for each series and for each subset. Coefficients of correlation (r) and of determination (r2) were uniformly high for all challenges except isometric handgrip (IHG). Since left ventricular ejection time is obtained directly from the pulse curve, with the exception of IHG, STI responses during stress testing can be measured without a phonocardiogram.

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Eight normal male volunteers were studied during bicycle ergometry at constant work loads of 50, 100, and 150 W for 4 min each and heart rate-targeted exercise to rates which matched those during the end of the 4th min at each constant work load. Systolic intervals measured prior to and during exercise included: Q-IM, isovolumic contraction time (IVCT), preejection period (PEP), left ventricular ejection time (LVET), ejection time index (ETI), PEP/LVET, and pulse transmission time (PTT). Directional changes during both exercise methods were consistent with previously reported results. Comparable control values indicated equivalent starting points for each bout and confirmed recovery from preceding exercise. There was striking similarities within each matched exercise set for Q-IM, IVCT, PEP, and PEP/LVET. LVET was significantly shorter for rate targeted exercise. We conclude that either constant-load or rate-targeted bicycle ergometry may be employed with choice of method determined by the purpose of the protocol and that systoloc intervals (except LVET) should not be importantly altered owing to the method chosen.

Regression equations for heart rate (HR)-ejection time (LVET) (Kesteloot and Denef, 1970;Benchimol and Matsuo, 1971;Parisi, Salzman and Schechter, 1971;Takahashi and Moritz, 1972;Matsuura and Goodyer, 1973). Because LVET is dependent on heart rate (HR) (Braunwald, Sarnoff, and Stainsby, 1958;Jones and Foster, 1964) it is common practice to correct LVET for HR based on linear regression equations. The corrected value, the ejection time index (ETI), is calculated as follows: ETI = LVET-b(HR), where b is the slope of the regression analysis of LVET on HR. By employing the intercept (a) of the regression equation, it is also possible to predict LVET for a given HR using the formula LVET= a+b(HR).While LVET is HR dependent, the exact relation varies according to factors such as age, sex, and health status (Weissler, Harris, and White, 1963;Harris et al., 1964;Spodick and Kumar, 1968;Kesteloot and Denef, 1970;Willems et al., 1970;Takahashi and Moritz, 1972). Physiological challenges such as supine (Lindquist, Spangler, and Blount, 1973;Maher et al., 1974) and upright (Lance and Spodick, 1976) bicycle exercise also effect differences in the HR-LVET relation. Demonstration of the HR-LVET relations under the different conditions in which LVET must be corrected for HR are of both theoretical and practical importance. They are of theoretical importance as an expression of the underlying physiology of these conditions. They are of practical importance as appropriate factors for correcting data.To obtain a range of LVET behaviour, we chose