| Abstract: | Systolic time interval methodology was used to explore the relative contributions of intracardiac and vascular delays to modifications in pulse transmission time elicited by a series of behavioural and physical challenges. The following variables were recorded on every cardiac cycle: interbeat interval (IBI), the interval between Q and R wave of the EKG, Q wave to pulse arrival (QPT) at the ear and wrist, left ventricular ejection time, and cardiac pre-ejection period (PEP). The true arterial pulse transit time (PTT), inversely related to pulse wave velocity, was calculated by subtracting PEP from QPT. Modifications of QPT were generally associated with PEP rather than PTT responses. But QPT to the ear and wrist were not equivalent; PEP showed closer correlations with QPT to the ear, while PTT was correlated more consistently with QPT to the wrist. Similar patterns were observed with monitoring from the Q and R waves of the EKG. Important differences also emerged between individuals in the degree to which QPT reactions were correlated with the cardiac or vascular components. A supplementary analysis of correlations between blood pressure and the components of QPT was carried out through hand-scoring of systolic time intervals. Both PEP and PTT contributed to the correlations of systolic pressure with QPT. The uses of pulse transmission times as indices of pulse wave velocity, or alternatively of PEP and ventricular contractility, are considered. |
