Hemodynamics and arterial properties underlying pressure responses to cognitive stress in borderline hypertensives.

摘要

It has been postulated that the blood pressure (BP) elevation observed in borderline hypertension is caused by enhanced reactivity to stress. To further elucidate the nature of pressure hyperreactivity in borderline hypertension, hemodynamic and arterial responses to the Stroop Color Word Test (SCWT) were studied in 23 borderline hypertensives and 19 normotensives, aged 20 to 63 and 24 to 64 respectively. Twenty borderline hypertensives had a cardiac index less than the mean plus one standard deviation of the normotensive group and were classified as the normokinetic borderline hypertensive subgroup. Blood pressure reactivity to stress of the borderline hypertensives was compared to that of the normotensives. Impedance-derived hemodynamics and arterial properties underlying BP responses to stress were compared between the normokinetic borderline hypertensive and the normotensive group.; Blood pressure was continuously recorded using a radial artery tonometer during the stress protocol. Heart rate and stroke volume were measured using the Minnesota impedance cardiograph. Augmentation index, an estimate of aortic wave reflection, was measured using a radial applanation tonometer and a pulse wave analysis system with a generalized transfer function. Arterial compliance was estimated using the stroke volume to aortic pulse pressure ratio. Ambulatory BP was also recorded at 30 to 60 minute intervals for a 24-hour period using an autonomic noninvasive cuff-oscillometric recorder.; Total peripheral resistance was higher in borderline hypertensive than in normotensive subjects. While arterial compliance was lower in normokinetic borderline hypertensives than in normotensives, augmentation index was similar between groups. The SCWT induced significant increases in systolic BP, diastolic BP and mean arterial pressure, which were of similar magnitude for borderline hypertensives and age-matched normotensives. Overall, hemodynamic and arterial responses to the SCWT were similar in normokinetic borderline hypertensives and normotensives. The BP reactivity to cognitive stress likely resulted from tachycardia rather than a vasoconstriction response, and was not associated with a change in wave reflection or compliance. Evaluated with ambulatory BP monitoring, borderline hypertensive subjects had a generally higher BP variability than normotensive subjects. Augmentation index did not predict the degree of nocturnal BP reduction, nor did it differentiate borderline hypertensives from normotensives, or dippers from nondippers.