Reproducibility of individual differences in behaviourally-elicited cardiovascular reactivity

The authors investigate the stability of individual differences in cardiovascular response to two behavioral stressors (mental arithmetic and concept formation) among 23 undergraduate males, at two laboratory sessions scheduled two weeks apart. Heart rate (HR), systolic and diastolic blood pressure (SPB, DBP), and measurements of pre-ejection period (PEP), stroke index (SI), cardiac index (CI), and total peripheral resistance (TPR) derived from impedance cardiography were obtained during baseline and task periods at each session. Results showed individual differences in HR, SBP, and PEP responses to these tasks to be reproducible on retesting, whereas impedance-derived measures of SI, CI, and TPR responses were not. Why the impedance-dependent measurements were less reliable than HR and blood pressure is unclear, though one explanation relates to possible intersession variability in circumferential electrode placement, which may influence measurements of basal thoracic impedance, dz/dt amplitude, and hence calculated estimates of stroke volume.<>