High blood pressure is called the silent killer because it does its work without symptoms for years. What it is doing in those years is not mysterious. Cardiologists have mapped it in detail. It is a story about a single layer of cells.
The gatekeeper
Every artery is lined with a layer one cell thick, the endothelium. It is not just a lining. It makes nitric oxide, keeps the vessel relaxed, stops platelets sticking and keeps inflammation out of the wall. When it is healthy, blood flows and nothing attaches. When it is damaged, the wall is open for business.1
Endothelial dysfunction can be detected before anything else is wrong. In children and young adults with risk factors for atherosclerosis, the arteries already relax less well than they should, decades before disease.2 It is the earliest measurable step, and a marker of what is to come.3
How pressure damages it
High pressure is a mechanical injury. It stretches the wall and roughens the lining, especially where arteries branch and flow is turbulent. Damaged endothelium makes less nitric oxide and lets more through. LDL cholesterol enters the wall, where it oxidises. The immune system responds to the oxidised LDL as it would to an invader, sending in cells that engulf it and become foam cells. A fatty streak forms, then a plaque.4
Atherosclerosis, in other words, is an inflammatory disease. The cholesterol is the fuel; the inflammation in a damaged wall is the fire.1 4
A heart attack is rarely a vessel slowly closing. It is a plaque splitting open and a clot forming on the wound.
The event
Over years the plaque grows and the wall around it weakens and inflames. The dangerous plaques are not always the biggest; they are the ones with a thin cap and an inflamed core. When the cap ruptures, the blood meets the material inside and does what blood does to a wound: it clots. If the clot blocks a coronary artery, the muscle beyond it loses its supply. That is a heart attack.5 The same failure in an artery supplying the brain is a stroke.
Where it is decided
Follow the chain backwards and every step passes through the endothelium: the nitric oxide it stopped making, the inflammation it let in, the plaque it couldn't prevent, the rupture of a wall it no longer protected. Dr Caldwell Esselstyn, the Cleveland Clinic physician whose work on arresting and reversing heart disease is cited throughout this field, puts the whole chain in one sentence: “CAD [coronary artery disease] begins with progressive endothelial injury, inflammatory oxidative stress, diminution of nitric oxide production, foam cell formation, and development of plaques that may rupture to cause a myocardial infarction (MI) or stroke.”6 The same paper is as clear about the other direction. His patients were taught “the importance of the endothelial cell and its product, nitric oxide”, and when the foods that injure the lining are avoided, “the body readily restores the capacity of endothelial tissue to produce nitric oxide.”6 Strengthen the lining and you change the whole chain.
What strengthens it
Everything that raises nitric oxide and lowers inflammation in the wall: movement, nitrate-rich food, sleep, slow breathing, less smoke, less alcohol, less stress, antioxidants that let nitric oxide survive, and the minerals the wall runs on. Everything, that is, in the seven levers and the four pathways. Keep taking any medication you have been prescribed; it protects you while the lining recovers. And measure, so you can see it happening.
