Hypertension is diagnosed when the systolic blood pressure is above 140, and the diastolic above 90. As explained in "Harrison's Principles of Internal Medicine," there is no exact definition of high blood pressure--the criteria for blood pressure are based on observing the level at which people begin to suffer from an increased risk of complications. Hypertension is a silent disease; for the most part, there are no symptoms until the disease is advanced and the damage to organs has been done.
Hypertensive Heart Disease
When the blood pressure is elevated, the heart must work harder to push blood into the arteries. As a result, It becomes hypertrophied, meaning that the heart muscle is thicker than normal. The thickened muscle can't relax properly, and the arteries supplying blood to the heart muscle can't deliver enough oxygen to meet its needs, leading to ischemia and chest pain. Prolonged ischemia can develop into a heart attack, in which a portion of the heart muscle dies. A major complication of hypertensive heart disease is heart failure, in which the heart cannot supply enough oxygenated blood to meet the body's needs. Disturbances in heart rhythm can also occur.
Strokes
Hypertension is the single most powerful risk factor for stroke. According to the National Institute of Neurological Disorders and Stroke, the risk for stroke is four to six times greater in people with hypertension than in people with normal blood pressure. Stroke is a leading cause of disability. Large strokes or repeated small strokes, that may go unnoticed, are thought to lead to cognitive decline in older people. "Harrison's Principles of Internal Medicine" explains that treatment of hypertension appears to reduce the risk of cognitive decline in patients with hypertension.
Kidney Disease
Hypertension damages the blood vessels in the kidneys, which impairs the kidneys' functioning, including their ability to dispose of excess fluids, thus exacerbating the existing hypertension. According to the National Kidney and Urological Diseases Clearinghouse, hypertension is a leading cause of renal failure in the United States, causing 25,000 new cases every year.
Eye Disease
Chronic hypertension damages the small blood vessels in the retina and contributes to disease of the larger blood vessels of the eye--the retinal artery and vein. Though the patient himself isn't aware of the damage, an eye exam will reveal changes typical to hypertensive retinopathy. Vision loss can occur. If blood pressure rises suddenly to very high levels, a condition known as malignant hypertension, swelling of the optic disk may occur, and can be accompanied by headache, vomiting and changes in the patient's mental state.
References
- "Harrison's Principles of Internal Medicine, 17th edition"; Anthony Fauci et al.; 2008
- National Institute of Neurological Disorders and Stroke: Stroke--Hope Through Research
- National Kidney and Urological Diseases Clearinghouse: High Blood Pressure and Kidney Disease
- Marck Manual for Healthcare Professionals: Hypertensive Retinopathy
