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 (โฅ140 or โฅ90). 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 โ vasoconstriction and increased HR/contractility), endothelial dysfunction (reduced nitric oxide bioavailability โ impaired vasodilation), and renal sodium handling defects (pressure natriuresis curve shifted rightward). Target organ damage from sustained HTN includes: left ventricular hypertrophy (pressure overload โ concentric remodeling โ diastolic then systolic dysfunction), nephrosclerosis (arteriolar thickening โ progressive CKD โ proteinuria), retinopathy (arteriolar narrowing โ AV nicking โ hemorrhages โ papilledema), and cerebrovascular disease (lipohyalinosis โ lacunar infarcts, atherosclerosis โ large vessel stroke, aneurysm formation). Management strategy: Elevated BP โ lifestyle modification alone. Stage 1 โ lifestyle + pharmacotherapy if 10-year ASCVD risk โฅ10% or compelling indication (DM, CKD, HF, post-MI). Stage 2 โ lifestyle + pharmacotherapy (consider two-drug initial therapy if...