Normal sympathetic vasomotor and cardiac parasympathetic activities in patients with primary aldosteronism: assessment by spectral analysis

Abstract

The role of the autonomic nervous system in hypertension due to mineralocorticoid excess remains unclear. To address this issue, we performed power spectral analysis of blood pressure (BP) and RR interval oscillations in 20 patients with primary aldosteronism (PA), 54 patients with essential hypertension (EH) and 45 normotensive (NT) subjects. Blood pressure and the degree of organ damage were similar between PA and EH groups. Age did not differ between the three groups. The Mayer wave power spectrum (MWP) of BP (approx. 0.1 Hz), an index of sympathetic vasomotor tone, was smaller in patients with PA than in patients with EH either while subjects were supine (systolic/diastolic; 3.9 ± 3.2 (SD)/1.5 ± 1.3 vs. 5.5 ± 4.2/2.1 ± 1.6 mmHg 2, P < 0.05 for both) or standing (7.6 ± 6.6/3.0 ± 3.0 vs. 17.7 ± 23.7/7.2 ± 8.3 mmHg 2, P < 0.05 for both). Supine respiratory-related power spectrum (RRP) of the RR interval (approx. 0.25 Hz), an index of cardiac parasympathetic tone, was greater in patients with PA than in patients with EH (545 ± 574 vs. 302 ± 464 ms 2, P < 0.01). The MWP of BP and the RRP of the RR interval were similar between patients with PA and NT subjects. Adrenalectomy reduced the 24-h mean BP (−18 mmHg for systolic BP, P < 0.001; −12 mmHg for diastolic BP, P < 0.01) and increased the 24-h mean heart rate (+8 bpm, P < 0.001). Furthermore, the diastolic MWP increased mildly (+32%, P < 0.05) and the RRP of the RR interval decreased dramatically (−75%, P < 0.01) following adrenalectomy. These results suggest that both vascular sympathetic and cardiac parasympathetic regulatory systems have minor roles in the maintenance of hypertension in patients with PA. The autonomic nervous system contributes more to the maintenance of BP following than prior to adrenalectomy. This information may be useful for the management of hypertension still persists after removal of adrenal adenoma.