Effects of Mineralocorticoid and AT1 Receptor Antagonism on The Aldosterone-Renin Ratio In Primary Aldosteronism-the EMIRA Study

Context: While current guidelines recommend the withdrawal of mineralocorticoid receptor antagonist (MRA) and renin-angiotensin system blockers for the screening and detection of primary aldosteronism (PA), this can worsen hypokalemia and control of high blood pressure (BP) values. Objective: To investigate whether aldosterone/renin ratio (ARR) values were affected by the MRA canrenone and/or by canrenone plus olmesartan treatment in patients with PA. Design: Within-patient study. Setting: The European Society of Hypertension center of excellence at the University of Padua. Patients: Consecutive patients with an unambiguous diagnosis of PA subtyped by adrenal vein sampling. Interventions: Patients were treated for 1 month with canrenone (50-100 mg orally), and for an additional month with canrenone plus olmesartan (10-20 mg orally). Canrenone and olmesartan were up-titrated over the first 2 weeks until BP values and hypokalemia were controlled. Patients with unilateral PA were adrenalectomized; those with bilateral PA were treated medically. Main Outcome Measures: BP, plasma levels of sodium and potassium, renin and aldosterone. Results: Canrenone neither lowered plasma aldosterone nor increased renin; thus, the high ARR and true positive rate remained unaffected. Addition of the angiotensin type 1 receptor blocker raised renin and slightly lowered aldosterone, which reduced the ARR and increased the false negative rate. Conclusions: At doses that effectively controlled serum potassium and BP values, canrenone did not preclude an accurate diagnosis in patients with PA. Addition of the angiotensin type 1 receptor blocker olmesartan slightly raised the false negative rate. Hence, MRA did not seem to endanger the accuracy of the diagnosis of PA.