Validation of the cardiac-vascular reactivity index and analysis of mixing type of pressor response

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Two contrastive types has been differentiated for the cardiovascular stress reactivity, i.e., cardiac and vascular type. This study introduced new index of cardiac-vascular reactivity pattern (CVI) and examined whether CVI combined with blood pressure reactivity index (BPI) was effective for the analysis of stress reactivity. In experiment 1, temporal variations in CVI and BPI were examined during sustained mental arithmetic task (MA), in which shift in the pressor mechanism was expected from cardiac to vascular one. Anticipation of (4min), engaging in (10min) and recovery from (4min) MA were recorded from 44 male undergraduates. Based on CVI and BPI during 1st 3min of MA, 4 groups was identified, i.e., cardiac and vascular reactors with higher pressor responder (RC and RV, respectively), and those with lower pressor responder (NC and NV, respectively). Persistent vascular responses were seen in vascular reactors. Blood pressure responder heightened not only vascular resistance but also cardiac pre-ejection period reactivity. Blood pressure is considered to be affected mainly by α-adrenergic mediated vascular resistance and be influenced by generalized sympathetic nervous reactivity. In experiment 2, the stability and validity were examined between supine and standing positions, and between MA and mirror drawing tasks (MD). Hemodynamic and autonomic indices were measured from 38 male undergraduates. Although correlations of reactivity were not significant between supine and standing position, CVI showed mixing variations of other cardiac and vascular measures of response. In conclusion, CVI appears to be an integrated measure of cardiac and vascular components in stress response. The primary advantage of CVI is the independence of sample statistics, and the comparability with other study.