Hypertension: Description, Diagnosis, Causes and, Consequences
Hypertension refers to high blood pressure. It is important because the risks of cardiovascular disease (mainly heart attack, heart failure, stroke and chronic kidney disease) increase in patients with hypertension. Indeed, it is the leading preventable cause of cardiovascular death. Unfortunately, hypertension typically does not produce symptoms and therefore the only way someone may know that they have the condition is to have the blood pressure measured. Blood pressure is recorded as systolic (upper level)/diastolic (lower level) of which the systolic is now considered the most important predictor of cardiovascular disease. Normal blood pressure is defined as an average value of systolic blood pressure below 130 mmHg. Borderline hypertension is 130 – 140 mmHg and established hypertension is above 140 mmHg. Blood pressure varies widely during the day, and in response to exercise, emotion and other factors. Therefore, the level of blood pressure cannot be safely established from a single measurement. It is better undertaken by repeated measurements in a doctor’s office or, ideally, by the subject themselves in their own home. Please see link to:
“Home blood pressure recording”
The most accurate measurement is an ambulatory blood pressure monitor (see patient information: Ambulatory Blood Pressure Monitor)
Borderline hypertension is not normally treated with medication, but is an important indication for lifestyle alterations. The following lifestyle factors are recognized as reversible causes of increased blood pressure and/or risk of cardiovascular disease: high salt intake, overweight and underactivity, prolonged stress and anxiety, more than one alcoholic drink and certain medications including nonsteroidal anti-inflammatory drugs (NSAIDs) such as motrin or ibuprofen. Please see link to: “Weight reduction”
High blood pressure is more frequent, and the risks more severe, in people who have other diseases that can affect the cardiovascular system. These includes: diabetes mellitus, and chronic kidney disease. Therefore, in these subjects, the "normal" blood pressure goal is a systolic blood pressure below 130 mmHg in most cases.
If someone is unsure whether they have hypertension, they should consult their physician, have their blood pressure measured in the office, and if it is equivocal or high, invest in a home blood pressure recorder and record their own blood pressure once daily after two minutes of quiet sitting for a period of about two weeks, and bring the results to the physician. A good choice is an automated Omron upper arm cuff blood pressure monitor. The pharmacist can help to choose a cuff of the correct size for the upper arm.
More than 9 out of 10 subjects with hypertension do not have a defined, reversible cause for the condition. In them, the hypertension is likely a combination of inherited genes and a lifestyle in which the level of salt intake is much higher, and the level of activity much lower, than that to which our bodily system was evolved to utilize. This leads to increased salt and fluid in the blood stream which increases the blood pressure. Hence, the advice in pre-hypertensive subjects to reduce dietary salt, improve exercise and lower body weight.
About 1 in 10 or 20 subjects with hypertension have a defined cause ("secondary hypertension"). This may be a coincident condition such as diabetes mellitus or chronic kidney disease or an unrecognized problem that has raised the blood pressure. There may be a decrease in blood flow to the kidneys most usually caused by fibrous bands in younger women ("fibromuscular dysplasia of the renal arteries") or atherosclerotic hardening of the arteries in older subjects. This leads the kidney to secret hormones such as renin into the blood stream that elevate the blood pressure, thereby helping to perfuse the kidney down stream from the narrowed artery, but at the expense of hypertension in the rest of the body. Sometimes, this can be treated by angioplasty (dilation of the artery by a radiologist) but, unfortunately, the condition is usually detected too late for the hypertension to respond to renal artery angioplasty, and the hypertension then requires medication for its control.
Other patients may have a benign tumor of the adrenal gland, which oversecrets a hormone termed aldosterone. This hormone acts on the kidney to retain salt and water, and thereby to raise the blood pressure,and to increase the excretion of potassium, which leads to low serum potassium concentrations. This condition ("hyperaldosteronism"), if diagnosed, maybe treatable by a relatively simple laparoscopic surgical removal of the benign adrenal tumor, which usually improves, and sometimes cures, the hypertension.
The conduct and interpretation of many of these tests for secondary or severe hypertension, and the treatment of severe or drug resistant hypertension, is complex, and is best undertaken by physicians specializing in these conditions. The Division of Nephrology and Hypertension at Georgetown University Medical Center has a number of full time staff physicians with expertise in hypertension diagnosis and management, and experienced radiologists and surgeons who can undertake the interventions if they are required. Please see link to: “Secondary Hypertension”
The majority of patients with high blood pressure presently require lifelong therapy with lifestyle modification and medication. The first step is always to reduce dietary salt intake, improve exercise and correct obesity or under activity. Salt intake must be assessed from a 24 hour urine collection for salt because 3/4 of the salt that we eat is already added to the food before it reaches the table. Therefore, merely avoiding additional salt, or the most obviously salty foods, is often not successful in achieving an adequate reduction in dietary salt intake. Please see link to: “24 Hour Urine Collection”
The goal for salt intake in the general population should be not more than approximately 150 millimoles or milliequilvalents daily. This is the same as to 9 gm of salt or 4 gm of sodium daily (one gram is 1000 mg). For patients with high blood pressure, a lower goal of 100 millimoles or milliequivalents (equivalent to 2 gm of sodium or 2000 mg) is a goal which can be achieved, but requires very close attention to diet, reading the salt content of foods at the store and ideally the preparation of fresh food from original ingredients in the home rather than eating prepared food in fast food restaurant settings. Please see link to: “Dietary Salt Restriction”
Besides sodium and chloride (salt), other food ingredients affect blood pressure and cardiovascular health. A recent NIH study showed that a specific diet (termed the DASH diet) significantly reduced blood pressure in normal subjects and those with high blood pressure. This diet emphasizes foods with low salt, high potassium and to fiber content. It is based on five servings daily of fresh fruits and/or vegetables, with low fat diary products, white meat and fish, grains and cereals but minimal processed carbohydrates or red meat. Please see link to: “The Dash Diet Information”
Potassium is found in many of the foods recommended in the DASH diet. A high potassium intake generally is associated with lower blood pressure and better cardiovascular health. However, some patients with chronic kidney disease accumulate potassium in the body to a dangerous degree and must have a low potassium diet. In that setting, please see the link to: “Dietary Potassium Restriction”
Lifestyle modifications are usually insufficient to control hypertension. These patients then require additional therapy with medications.