Persistent Sympathetic Activation During Chronic Antihypertensive Therapy

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Abstract
Previous studies have demonstrated that antihypertensive treatment resets baroreflex control of heart rate (HR) and increases cardiac vagal baroreflex sensitivity. However, it is uncertain whether baroreflex control of muscle sympathetic nerve activity (MSNA) also resets after treatment. We tested the hypothesis that chronic antihypertensive therapy alters baroreflex regulation of MSNA in patients with untreated moderate hypertension. Seven newly diagnosed patients with systolic blood pressure (BP) of 159±5 mm Hg (mean±SE) and diastolic BP of 103±4 mm Hg were studied before and after 1 to 2 weeks ' and 3 months (chronic) of antihypertensive treatment with losartan-hydrochlorothiazide (Hyzaar). MSNA and hemodynamics were measured supine, during a Valsalva maneuver (VM), and at 70° head-up tilt (HUT) for 10 minutes. Data were compared with those obtained in 7 age-matched healthy controls. We found that Hyzaar lowered mean BP acutely and chronically by 20±4 and 23±3 mm Hg (both P<0.01) but did not change HR....