Cardiovascular
Blood Pressure
Systolic over diastolic — the force driving blood through arteries
Blood pressure is the force blood exerts against arterial walls, recorded as systolic/diastolic in mmHg. Normal: 120/80. Systolic = peak pressure during ventricular contraction. Diastolic = trough pressure between beats. Hypertension (≥130/80 by ACC/AHA 2017; ≥140/90 by ESC) silently damages arteries, kidneys, brain. It is the #1 modifiable cause of cardiovascular death worldwide. Mean arterial pressure (MAP) ≈ DBP + ⅓(SBP−DBP); MAP ≥65 mmHg needed to perfuse organs.
- Normal target<120/80 mmHg
- Hypertension stage 1130-139/80-89 (ACC/AHA)
- Hypertension stage 2≥140/90
- MAP formulaDBP + ⅓ × (SBP − DBP)
- First-line drugsACEi/ARB, CCB, thiazide
- Global prevalence~1.3 billion adults
Interactive visualization
Press play, or step through manually. The visualization is yours to drive — try it before reading on.
Watch the 60-second explainer
A condensed visual walkthrough — narrated, captioned, under a minute.
Why blood pressure matters
- Stroke prevention. Each 20/10 mmHg above 115/75 doubles cardiovascular risk.
- Cardiac load. Hypertension causes left ventricular hypertrophy and heart failure.
- Renal protection. Hypertension is the #2 cause of ESRD after diabetes.
- Cognitive aging. Midlife hypertension predicts dementia decades later.
- Pregnancy. Preeclampsia: BP ≥140/90 plus proteinuria; emergency delivery if severe.
- Surgical risk. Uncontrolled BP postpones elective surgery.
- Hypotension matters too. Septic shock targets MAP ≥65 mmHg for organ perfusion.
Common misconceptions
- "My BP is fine without meds because I feel fine." Symptoms don't track BP.
- One reading defines hypertension. Diagnosis needs ≥2 visits, ideally with home or ambulatory monitoring.
- Diastolic doesn't matter after 60. Both still predict events; isolated systolic is most common in elderly.
- White-coat hypertension is benign. ~30% progress to sustained hypertension within 5 years.
- Stop drugs once BP is controlled. Hypertension is lifelong; stopping returns BP to baseline.
- Beta-blockers are first-line. Only if there's coronary disease, heart failure, or arrhythmia indication.
Frequently asked questions
What do the two numbers mean?
Systolic (top) is peak arterial pressure when the left ventricle contracts and ejects blood. Diastolic (bottom) is the lowest pressure between beats while the ventricle relaxes and fills. Normal 120/80. Pulse pressure = SBP − DBP (normally 40 mmHg). Wide pulse pressure suggests stiff arteries or aortic regurgitation; narrow suggests low stroke volume or tamponade.
How is it measured?
Auscultatory method: cuff inflated above SBP, deflated slowly. Korotkoff sounds appear at SBP (phase I) and disappear at DBP (phase V). Oscillometric machines use cuff pressure oscillations. Cuff size matters: too small overestimates by 10-50 mmHg. Position: arm at heart level, feet flat, no caffeine/smoking 30 min prior. Take two readings 1-2 min apart.
When does hypertension cause symptoms?
Usually never until end-organ damage. The "silent killer" — most patients feel fine at 160/100. Symptoms (headache, blurred vision, dyspnea) appear with hypertensive emergency (>180/120) or established complications: stroke, heart failure, renal failure. This is why screening matters: 1 in 5 with hypertension don't know they have it.
What raises blood pressure?
Age (arterial stiffening), obesity, salt intake, alcohol, stress, sleep apnea, NSAIDs, decongestants, oral contraceptives, licorice. Secondary causes (~10%): renal artery stenosis, primary aldosteronism (Conn), pheochromocytoma, Cushing, coarctation. Always consider secondary in young patients, drug-resistant cases, or paroxysmal pattern.
How is it treated?
Lifestyle first: DASH diet, sodium <2.3 g/day, weight loss (1 mmHg per kg), exercise, alcohol limit. Drugs: ACEi (lisinopril) or ARB (losartan), calcium channel blocker (amlodipine), thiazide (chlorthalidone). Beta-blockers second-line unless coronary disease. Goal: <130/80 in most adults; <140/90 in frail elderly. Combination therapy is the rule, not exception.
What is hypertensive emergency?
BP >180/120 with end-organ damage (encephalopathy, MI, aortic dissection, eclampsia, AKI). Lower MAP by 10-20% in first hour, then 5-15% over next 23 hours. Aggressive lowering causes watershed strokes. Drugs: IV labetalol, nicardipine, clevidipine, nitroprusside. Aortic dissection: target SBP <120 within minutes.
Why does salt matter?
Sodium retention expands plasma volume; raises cardiac output and peripheral resistance via endothelial effects. Salt-sensitive individuals (Black patients, elderly, CKD) show 5-10 mmHg drop with sodium restriction. DASH-sodium trial: cutting from 3.5 to 1.2 g sodium dropped SBP by 8 mmHg in hypertensives. Population-wide reduction would prevent millions of strokes annually.