Blood pressure: how to measure, manage, and treat high blood pressure (AMA #48 rebroadcast)

KEYPOINTS

• 01

  Blood pressure is one of three main drivers of atherosclerosis, along with apoB and smoking, because it mechanically damages the endothelium.

  Peter frames them as complementary attacks: hypertension is a mechanical injury to the vessel lining, smoking is a chemical one, and apoB is the particle that gets through the damaged wall. All three are 'area under the curve' problems that compound over decades, so a 35-year-old with untreated hypertension is accruing risk for 40 years, not the 3 years of a typical trial.

• 02

  Current US categories: normal is below 120/80, elevated is 120–129/<80, stage 1 is 130–139 or 80–89, stage 2 is ≥140 or ≥90.

  Tightened in 2017 after SPRINT. Note 120/83 is stage 1 despite a normal systolic. Peter would be happy with 119/78 but won't rush to medicate a borderline 123/79 average, because unlike apoB, pressure can go too low and overtreatment causes orthostasis, fainting and falls.

• 03

  SPRINT showed intensive control below 120 systolic cut cardiovascular events by about 25% and all-cause death by 27%.

  About 9,400 high-risk, non-diabetic adults with systolic pressure of 130 or higher were treated to below 120 or below 140. After one year they averaged 121.4 versus 136.2. The trial was stopped early at a median of a little over 3 years. The composite outcome had a hazard ratio of about 0.75 (roughly 0.54% absolute reduction per year), cardiovascular death halved, and all-cause mortality fell 1.2% in absolute terms, including fewer kidney and even accidental deaths. Peter calls it about as conclusive as trials get.

• 04

  Hypertension mostly damages three small-vessel organs: heart, brain and kidneys.

  Meta-analyses of 40–70-year-olds show each 20 mmHg rise in systolic (or 10 diastolic) doubles the risk of death from stroke, heart disease or vascular disease, so 140/90 carries about twice the risk of 120/80. The kidneys are 1–2% of body weight but get 20–25% of cardiac output, which makes them highly pressure-sensitive. In SPRINT MIND, intensive lowering cut dementia risk by about 16% in relative terms.

• 05

  About 46% of US adults have hypertension, and it's largely silent.

  Prevalence is roughly 30% in men and just under 20% in women aged 20–44, about half of men at 45–55, and over 80% for both sexes at 75 and older. It's highest in African Americans (about 59% of men, 56% of women). There are no reliable symptoms; the only way to know is to measure accurately.

• 06

  Sloppy technique can move a reading by 10–30 mmHg, so home measurement under protocol beats office readings.

  The errors Peter lists: wrong cuff size or measuring over clothing; unsupported back or feet (5–10 mmHg); crossed legs (5–8); skipping a 5-minute silent rest (10–20); talking (10–15); pain (10–30); a full bladder (10–15); and about 2 mmHg for every inch the arm sits above or below the heart. He ignores his own office readings. Before judging anything he wants two weeks of readings taken two or three times a day.

• 07

  Manual readings are the gold standard, and automated cuffs read 10–15 mmHg high for Peter.

  He describes the manual method: inflate about 30 mmHg past the point where the pulse disappears, then release slowly; the first tapping sound is systolic and the point where the sound vanishes is diastolic. His two expensive automated cuffs consistently read high systolic against several manual checks. His guess is that automated devices estimate from mean arterial pressure. Automated cuffs are still fine for most people if they're used correctly.

• 08

  Pressure should dip 10–20% at night; during exercise systolic rises normally, but a rising diastolic is a red flag.

  Lying down and parasympathetic tone should lower nighttime pressure, which is what 24-hour ambulatory monitors look for. Stress alone can push Peter over 140. During VO2 max testing a systolic of 180–200 is normal, because widening arterioles lower vascular resistance and keep diastolic flat. People with dilated aortas may need to avoid heavy breath-holding lifts that spike pressure.

• 09

  About 10% of hypertension has a fixable underlying cause (secondary hypertension).

  Clues include resistance to medication, readings over 180, sudden onset, or high pressure in a young person with no risk factors. Causes to rule out include kidney disease, narrowed renal arteries, thyroid disease, excess aldosterone and adrenal tumors. 'Primary' hypertension, Peter says, is really code for 'we don't know the cause.'

• 10

  Lifestyle moves blood pressure far more than it moves lipids, and might let about half of hypertensives avoid drugs.

  Each kilogram lost lowers systolic by a little over 1 mmHg and diastolic by nearly 1. Aerobic training of 90–150 minutes a week at 65–75% of max heart rate (zone 2) lowers systolic by up to 8 and diastolic by about 5 within weeks. Dynamic resistance training lowers it by about 2/3, and isometric work by about 6/3. Insulin resistance raises pressure by reducing nitric oxide availability (ADMA and SDMA are markers). Sleeping under 5 or over 10 hours is linked to up to 40% higher hypertension risk.