SUN-224 Interrogating the Distinction Between Low-Renin Hypertension and Primary Aldosteronism Using Angiotensin Converting Enzyme Inhibition

Abstract Disclosure: C. Tsai: None. J.M. Brown: None. S.P. Salle: None. A.J. Newman: None. V. Wu: None. Y. Lin: None. A. Vaidya: None. Background: Primary aldosteronism (PA) is a form of low-renin hypertension (LRH) characterized by inappropriate aldosterone production. In normal physiology, angiotensin-converting enzyme inhibitors acutely raise renin and lower aldosterone, but this response is altered in patients with PA. We investigated the distinction between LRH and PA using the captopril challenge test (CCT). Methods: We conducted a retrospective cohort study with 756 patients with LRH who underwent CCT for diagnostic evaluation of PA. The distinction between PA and LRH was assessed by four CCT criteria: 1) Post-CCT renin activity < 1ng/mL/h and aldosterone decrease < 30%; 2) Post-CCT aldosterone-to-renin ratio > 30ng/dL per ng/mL/h; 3) Post-CCT renin activity < 1ng/mL/h; 4) Post-CCT aldosterone >11ng/dL. Treatment outcomes following aldosterone-targeted therapy were assessed after 12 months using PASO and PAMO criteria. Results: There was a continuous spectrum of nonsuppressible aldosterone production post-CCT that transcended categorical criteria. When interpreting CCT results based on both renin and aldosterone responses (criteria 1 or 2), 57.8-66.3% of patients were classified as having PA. When interpreting CCT results based on only aldosterone or renin responses (criteria 3 or 4), 82.5-95.1% of patients were classified as having PA. Among patients receiving aldosterone-targeted therapy with follow-up data, complete or partial treatment responses were high, 86.5-91.7%, regardless of CCT interpretations. Conclusion: These findings highlight the blurred distinction between LRH and PA. Although persistently suppressed renin, or elevated aldosterone, following captopril facilitated the maximum capture of “PA” cases, implementation of aldosterone-targeted therapy provided similar benefits to all patients, regardless of CCT interpretations. Empiric aldosterone-directed therapy for patients with LRH suspected of having PA may be an appropriate alternative to laborious diagnostics to confirm PA. Presentation: Sunday, July 13, 2025