HardCardiologyResistant hypertension and secondary causesca-rcpsc-im
A 48-year-old man with a 3-year history of hypertension is on maximal doses of an ACE inhibitor, a thiazide-like diuretic, and a long-acting calcium-channel blocker. His clinic blood pressures remain around 162/96 mm Hg despite good adherence, appropriate lifestyle measures, and confirmed elevated home blood pressure readings. Serum potassium is 3.2 mmol/L, and creatinine is 90 µmol/L. Which investigation is the most appropriate next step?