A low-renin status characterized two-thirds of patients with treatment-resistant hypertension, who could be treated efficiently by aldosterone inhibition. Patients with an escape phenomenon (18%) could effectively be treated by increasing the aldosterone inhibitor. Low-renin hypertensives had high prevalence of adrenocortical adenomas and primary aldosteronism.

Abstract-In the present study we hypothesized that arterial catecholamine concentrations during rest and 2 laboratory stress tests were independent predictors of blood pressure at an 18-year follow-up. At entry, blood pressure, heart rate, and arterial plasma epinephrine and norepinephrine concentrations were measured in 99 healthy men (age: 19.3Ϯ0.4 years, meanϮSD) at rest, during a mental arithmetic test, and during a cold pressor test. After 18.0Ϯ0.9 years of follow-up, resting blood pressure was measured. The norepinephrine and epinephrine concentrations during the mental arithmetic explained 12.7% of the variation of future systolic blood pressure after adjusting for initial resting blood pressure, family history, body mass index, and systolic blood pressure during the stress test in a multiple regression analysis (adjusted R 2 ϭ0.651; PϽ0.001). To conclude, the present study shows that sympathetic nervous activity during mental arithmetic predicts future blood pressure, indicating a possible causal factor in the development of essential hypertension independent of the initial blood pressure. (Hypertension. 2008;52:336-341.)Key Words: blood pressure Ⅲ stress reactivity Ⅲ catecholamines Ⅲ cold pressor test Ⅲ epinephrine Ⅲ mental stress Ⅲ norepinephrine H ypertension and other cardiovascular diseases develop slowly over decades, and although the disease process starts early, clinical manifestations do not usually appear until late middle age. Interestingly, the classical risk factors, like family history, obesity, smoking, diabetes, and hypercholesterolemia, are able to predict only Ϸ50% of future cardiovascular diseases. 1 Thus, much effort has been made to identify other risk factors, and increased reactivity to stress is believed to be one of them.Although previous prospective studies on reactivity as a predictor of future hypertension have given conflicting results, 1 studies with a follow-up of Ͼ5 years tend to show a strong association between cardiovascular hyperreactivity and future hypertension. [2][3][4][5][6][7][8][9] This supports the reactivity hypothesis, which states that exaggerated physical or psychological responses to stress identify subgroups with increased cardiovascular risk. 10

No abstract

Several studies have shown increased sympathetic activity during acute exposure to hypobaric hypoxia. In a recent field study we found reduced plasma catecholamines during the first days after a stepwise ascent to high altitude. In the present study 14 subjects were exposed to a simulated ascent in a hypobaric chamber to test the hypothesis of a temporary reduction in autonomic activity. The altitude was increased stepwise to 4500 m over 3 days. Heart rate variability (HRV) was assessed continuously in seven subjects. Baroreceptor reflex sensitivity (BRS) was determined in eight subjects with the 'Transfer Function' method at baseline, at 4500 m and after returning to baseline. Resting plasma catecholamines and cardiovascular- and plasma catecholamine- responses to cold pressor- (CPT) and mental stress-test (MST) were assessed daily in all and 12 subjects, respectively. Data are mean +/- SEM. Compared with baseline at 4500 m there were lower total power (TP) (35 457 +/- 26 302 vs. 15 001 +/- 11 176 ms2), low frequency (LF) power (3112 +/- 809 vs. 1741 +/- 604 ms2), high frequency (HF) power (1466 +/- 520 vs. 459 +/- 189 ms2) and HF normalized units (46 +/- 0.007 vs. 44 +/- 0.006%), P < or = 0.001. Baroreceptor reflex sensitivity decreased (15.6 +/- 2.1 vs. 9.5 +/- 2.6 ms mmHg(-1), P = 0.015). Resting noradrenaline (NA) decreased (522 +/- 98 vs. 357 +/- 60 pmol L(-1), P = 0.027). The increase in systolic blood pressure (SBP) and NA during mental stress was less pronounced (21 +/- 4 vs. 10 +/- 2% and 25 +/- 9 vs. -2 +/- 8%, respectively, P < 0.05). The increase in SBP during cold pressor test decreased (16 +/- 3 vs. 1 +/- 6%, P = 0.03). Diastolic blood pressure, HR and adrenaline displayed similar tendencies. We conclude that a transient reduction in parasympathetic and sympathetic activity was demonstrated during stepwise exposure to high altitude.

Abstract-We hypothesized that resting blood pressure is related to sympathetic activity in young men who are unaware of their blood pressure status in high, normal, and low ranges and that there is a relationship between sympathetic activity and coronary risk factors. Forty-three healthy, young men from the 1st [group 1, 106/52Ϯ2/2 mm Hg (ϮSEM), nϭ15], 50th (group 2, 129/79Ϯ2/1 mm Hg, nϭ15), and 98th to 99th percentile (group 3, 166/97Ϯ3/1 mm Hg, nϭ13) at a blood pressure screening were studied with intraarterial blood pressure, heart rate, and arterial plasma catecholamine responses to a mental, cold pressor, and orthostatic stress test. At baseline, group 3 had significant higher blood pressure (137/74Ϯ3/2 mm Hg) than group 2 (126/66Ϯ3/2 mm Hg; PϽ0.01) and group 1 (116/62Ϯ2/1 mm Hg; PϽ0.001). Group 1 had lower systolic blood pressure than group 2 (Pϭ0.007). Baseline epinephrine and norepinephrine showed a clear positive linear trend (PϽ0.05), with the lowest values being in group 1 and highest in group 3. High-density lipoprotein was negatively related to epinephrine (rϭϪ0.387; Pϭ0.010). Mental stress was the only test that showed significant differences in cardiovascular and sympathetic responses among the groups, where group 3 had a more pronounced response in systolic and diastolic blood pressure and heart rate compared with group 1 (PϽ0.001) and group 2 (PϽ0.01). Furthermore, we found significant positive linear trends for ⌬catecholamines during mental stress across the groups (⌬epinephrine Pϭ0.001 and ⌬norepinephrine Pϭ0.026, ANOVA). We conclude that resting blood pressure reflects both variation in resting arterial catecholamines and variation in cardiovascular and sympathetic responses specifically to mental stress. Key Words: blood pressure Ⅲ catecholamines Ⅲ epinephrine Ⅲ stress Ⅲ norepinephrine W e have demonstrated previously that pure knowledge of being hypertensive may increase blood pressure (BP), heart rate (HR), plasma catecholamines, and cardiovascular and sympathetic responses to laboratory stressors, 1-3 thereby being a confounding factor in hypertension research. Thus, pathophysiological studies in hypertension should ideally be carried out in subjects unaware of their BP status. In a previous study, 4 we examined plasma catecholamines in 3 groups of 19-year-old men with different screening BPs while keeping them unaware of their BP level. In our laboratory, the group with the highest screening BP had normal BP and plasma catecholamines after 30 minutes of supine rest. Thus, in this former study, we were not able to examine sympathetic activity in unaware subjects with high resting BP. We found, however, that subjects from the highest percentile of screening BP were characterized by cardiovascular hyperreactivity specifically to mental stress. Furthermore, important coronary risk factors seemed to be catecholamine dependent in this group.Based on our previous observations, we hypothesized in the present study that resting BP was related to arterial plasma catecholamines, cardiovascular and ...