The raised blood pressure of hypertension is well known to accelerate the progression of atherosclerosis. It certainly makes it more likely for blood vessels weakened by atherosclerotic lesions to rupture, or for the lesions themselves to fragment and cause blockages. Beyond that, however, mechanisms are at work in the environment of high blood pressure to accelerate the growth of these lesions. The major consequences of atherosclerosis, stroke and heart attack, are the cause of death for a sizable fraction of all people, and this is why blood pressure control produces a meaningful reduction in mortality risk, by slowing the progression towards those consequences.
Blood pressure-lowering drugs are routinely used to prevent the development of atherosclerosis and heart disease, but the mechanism of this effect is still unknown. People suffering from high blood pressure (hypertension) often have accompanying changes in the hormones that control blood pressure and it has been unclear whether the pressure itself or the hormonal changes are the driver of accelerated atherosclerosis. To investigate this, researchers analyzed the development of atherosclerosis in minipigs that were genetically engineered to have high blood cholesterol and develop atherosclerosis.
Minipigs have arteries that are very similar in structure to human arteries and like humans they develop atherosclerosis in the heart when exposed to high blood cholesterol. By manipulating blood pressure in the pigs and by analyzing the effects on arteries in the heart, the researchers found that the direct forces of pressure on arteries leads to structural changes that facilitate the development of atherosclerosis. "Arteries become denser and allow less passage of molecules from the blood. This includes the LDL particles that carry blood cholesterol, which instead accumulate in the innermost layer of arteries, where they drive the development of atherosclerosis."
This finding uncovers an intimate relationship between the most important risk factors for atherosclerosis, LDL cholesterol and high blood pressure. While it has been known for decades that accumulation of LDL particles in arteries lead to atherosclerosis, the new research shows that high blood pressure accelerates the accumulation of LDL. Therefore, high blood pressure aggravates the effect of having high LDL cholesterol in the blood.