Hypertension is defined by the 2017 ACC/AHA guidelines as BP ≥130/80 mmHg (replacing the previous JNC8 threshold of 140/90). Sustained elevated pressure causes endothelial dysfunction, reduces nitric oxide bioavailability, promotes vascular smooth muscle hypertrophy and arterial stiffening. The left ventricle undergoes concentric hypertrophy to overcome increased afterload, eventually progressing to diastolic then systolic dysfunction. Target organ damage affects the brain (lacunar infarcts, hemorrhagic stroke), heart (LVH, coronary artery disease, heart failure), kidneys (nephrosclerosis, proteinuria), eyes (hypertensive retinopathy), and peripheral vasculature (atherosclerosis, aortic dissection). Diagnosis requires confirmation with out-of-office measurements to exclude white-coat hypertension, which affects 15-30% of patients with elevated office readings.