High Blood Pressure (HBP)

High blood pressure is defined for surveillance purposes as SBP ≥140 mm Hg or DBP ≥ 90 mm Hg, taking antihypertensive medications, or being told at least twice one has HBP.However, note that recent ACC/AHA Guidelines recommend that HBP be defined as  ≥130/≥80. HBP is the single most important modifiable risk factor for stroke. Approximately one-third of all US adults have high blood pressure. This at least doubles their lifetime risk of stroke, independent of other risk factors. It is estimated that about 75% of those who have a stroke had high blood pressure prior to the event. Long-term control of high blood pressure at target levels significantly reduces stroke risk. Recent trials suggest that intense systolic BP control (to <120 mm Hg) may have further benefit.

Populations at special risk

The age-adjusted prevalence of hypertension is about 45% in adult non-Hispanic black men and women, compared to about 27% in adult non-Hispanic whites. Furthermore, black Americans tend to develop high blood pressure earlier in life, and their average blood pressures are much higher compared to most other populations. Higher systolic blood pressure explains approximately 50% of the excess stroke risk among blacks compared to whites.

Relationship to stroke pathogenesis

Atherosclerotic plaque development in extracranial or intracranial arteries supplying the brain is a slowly progressive process that apparently begins in the teenage years. Arteries that are continuously subjected to high pressures are more likely to develop plaque, and it is also more likely that the endothelial surface of the vessel will be damaged, promoting plaque rupture and the formation of thrombi. A thrombus can occlude the vessel locally or can break off and potentially embolize the brain. Hypertension likely initiates lipohyalinosis of small arteries that deeply penetrate the brain, which makes their walls prone to rupture (producing an intraparenchymal brain hemorrhage) or to collapse, occluding the lumen and producing a small ischemic infarct.

A little about control and treatment

In most cases, the cause of hypertension isn’t known; however hypertension is easily detected, and is usually, although not always, controllable. A recent large U.S. study show that about 84% of adults with hypertension are aware of their condition, 76% are currently being treated, 54% have their blood pressure consistently controlled while 46% do not. Compared to whites, blacks with hypertension were more likely aware of their HBP and more likely to be treated – but less likely to have it well controlled.

Blood pressure goals are lower if the patient has additional risk factors for stroke, such as diabetes. BP <120/<80 is considered desirable. For a small number of patients, treatment of kidney, adrenal or thyroid disease can reverse hypertension. However for most patients, the physician’s challenge is to create a management plan that will enable the patient to maintain the recommended blood pressure levels over an extended time period. This plan usually combines lifestyle changes (more fruits/vegetables and lower fat in diet, weight loss, increased physical activity, alcohol moderation, smoking cessation) and one or more medications.