V. COMPLICATIONS
A. Effects on Arteries and Heart
1. Myocardial Infarction
Hypertension damages the arteries in many vital organs, especially the brain, heart, kidneys, and eyes. Damage to the walls of the arteries is due to the increase in blood pressure, but important added factors are an increase in pulsatile force and velocity of the blood. The artery
wall responds to this stress by thickening its walls, but this leads to further narrowing of the arteries and a further increase in blood pressure. The arteries must branch to supply blood to various organs and tissues. Unfortunately, the branches to some areas take off at near right angles and mechanical stress is greatest at these points. The high velocity and pulsatile force of blood at a high pressure set up turbulence and mechanical stress that damage the smooth lining of the arteries, occasionally causing small tears (dissections) of the arteries. This mechanical injury provokes proliferation of smooth muscle cells of the artery walls and accumulation of fatty material including choles¬terol and small blood particles (platelets). This thickening produces a plaque (atheroma) that juts out into the lumen of the artery thus obstructing blood flow, which causes low flow and turbulence in the artery.