REN and Hypertension resistant to conventional therapy: Resistant hypertension (RHTN) is defined as BP that is uncontrolled despite using ≥ 3 medications of different classes, commonly a long-acting calcium channel blocker (CCB), a blocker of the renin-angiotensin system (angiotensin-converting enzyme [ACE] inhibitor or angiotensin receptor blocker [ARB]) and a diuretic.