Hypertension, or high blood pressure, accounts for about 6 percent of deaths worldwide, as stated in "Harrison's Principles of Internal Medicine". Current criteria define hypertension as a systolic blood pressure above 140 or a diastolic blood pressure above 90. These criteria are subject to change based on studies of the risks of hypertension in the population.
Heart Disease
Hypertension leads to atherosclerosis, which is hardening of the arteries. In addition, the heart muscle thickens, or hypertrophies, as a result of needing to pump blood against higher resistance. The heart muscle needs oxygen in order to function, just like any other organ, and it obtains the oxygen when it relaxes, a period known as diastole. As the heart muscle hypertrophies it loses its capacity to relax, which makes it even more difficult for the hardened arteries to supply it with oxygen. This leads to ischemic heart disease, heart attacks, heart failure and death.
Effects on the Brain
Hypertension increases the risk for strokes. According to "Harrison's Principles of Internal Medicine," the risk for stroke is especially great in people over 65 who have increased systolic blood pressure. Hypertension is associated with cognitive decline and dementia, which can be due to a large stroke or multiple small strokes. In malignant hypertension, the blood pressure rises rapidly and to much higher levels than are usual for the hypertensive individual, leading to hypertensive encephalopathy. Symptoms include severe headache, nausea and vomiting; coma, seizures and death.
The Kidneys and Hypertension
Hypertension can lead to renal damage and eventually to renal failure. Malignant hypertension leads to severe and rapid damage to the kidneys, as explained by Americanheart.org. Conversely, renal disease can cause hypertension and is the most common cause of secondary hypertension, meaning hypertension that has a known cause.
Hypertensive Retinopathy
Hypertension leads to narrowing and leaking of blood vessels in the retina. An eye exam by an ophthalmologist will reveal changes that are typical of hypertension. Complications include loss of vision and headaches. Since hypertensive changes in the retina can be seen without any invasive procedures, patients with hypertension should have regular eye exams. Treatment of hypertension is the only way to prevent progression of hypertensive retinopathy.
References
- "Harrison's Principles of Internal Medicine, 17th edition"; Anthony Fauci et al.; 2008
- Mayoclinic.com: Hypertension, Complications
- Americanheart.org: An Overview of the Kidney in Cardiovascular Disease
