Pathophysiology
Clinical meaning
Hypertension (HTN) is a sustained elevation in systemic arterial blood pressure classified by the ACC/AHA 2017 guidelines into stages: Normal (<120/<80 mmHg), Elevated (120-129/<80), Stage 1 (130-139 or 80-89), and Stage 2 (≥140 or ≥90). The pathophysiology involves increased cardiac output, elevated systemic vascular resistance (SVR), or both. Key mechanisms include: RAAS overactivation (angiotensin II causes vasoconstriction and aldosterone-mediated sodium/water retention), sympathetic nervous system overactivity (increased norepinephrine → vasoconstriction and increased HR/contractility), endothelial dysfunction (reduced nitric oxide bioavailability → impaired vasodilation), and renal sodium handling defects (pressure natriuresis curve shifted rightward). Target organ damage from sustained HTN includes: left ventricular hypertrophy (pressure overload → concentric remodeling → diastolic then systolic dysfunction), nephrosclerosis (arteriolar thickening → progressive CKD → proteinuria), retinopathy (arteriolar narrowing → AV nicking → hemorrhages → papilledema), and cerebrovascular disease (lipohyalinosis → lacunar infarcts, atherosclerosis → large vessel stroke, aneurysm formation). Management strategy: Elevated BP → lifestyle modification alone. Stage 1 → lifestyle + pharmacotherapy if 10-year ASCVD risk ≥10% or compelling indication (DM, CKD, HF, post-MI). Stage 2 → lifestyle + pharmacotherapy (consider two-drug initial therapy if...