Chronic hypertension overview

Hypertension Main page
Overview
Causes
Classification Primary Hypertension Secondary Hypertension Hypertensive Emergency Hypertensive Urgency
Screening

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-In-Chief: Taylor Palmieri

Overview

Hypertension, commonly referred to as "high blood pressure" or HTN, is a medical condition in which the blood pressure is chronically elevated. While it is formally called arterial hypertension, the word "hypertension" without a qualifier usually refers to arterial hypertension.

In 2003, the Joint National Committee provided a seventh report (JNC 7) which suggested the following definitions based upon the average of two or more properly measured readings at each of two or more visits after an initial screen:

• Normal blood pressure: systolic <120 mmHg and diastolic <80 mmHg
• Prehypertension: systolic 120-139 mmHg or diastolic 80-89 mmHg
• Hypertension:

Stage 1: systolic 140-159 mmHg or diastolic 90-99 mmHg

Stage 2: systolic ≥160 or diastolic ≥100 mmHg

Classification

Hypertension can be classified as either essential (primary) or secondary. Essential hypertension indicates that no specific medical cause can be found to explain a patient's condition. Secondary hypertension indicates that the high blood pressure is a result of (i.e. secondary to) another condition, such as kidney disease or certain tumors (especially of the adrenal gland).

Pathophysiology

While the mechanisms underlying secondary hypertension are well understood, the mechanisms underlying primary or essential hypertension are poorly understood. It has been postulated that polygenic influences, increased arterial collagen with aging, salt consumption and sensitivity, hyperinsulinemia as part of the metabolic syndrome and renin may all play a role in the pathophysiology of essential hypertension.

Epidemiology and Demographics

Hypertension is one of the most common diseases afflicting humans worldwide, estimated to have a prevalence of as many as 1 billion individuals, and causing 7.1 million deaths per year. Hypertension is the most important modifiable risk factor for coronary heart disease (the leading cause of death in North America), stroke (the third leading cause), congestive heart failure, peripheral vascular disease, and is a leading cause of chronic renal failure. Despite the prevalence and associated complications of hypertension, control of the disease is still exceedingly insufficient.

Risk Factors

Established risk factors for essential hypertension include increased alcohol intake (more than 2 drinks per day), increased salt intake in diet (more than 2 gm per day), obesity, and a sedentary lifestyle and lack of exercise. All these risk factor are reversible. Smoking is not a risk factor for hypertension.

Natural History, Complications, Prognosis

Even moderate elevation of arterial blood pressure leads to shortened life expectancy. At severely high pressures, mean arterial pressures 50% or more above average, a person can expect to live no more than just a few years unless appropriately treated.

Diagnosis

The key to properly diagnosing hypertension is an accurate measurement of blood pressure. Accurate, reproducible blood pressure measurement is important to allow comparisons between blood pressure values and to correctly classify blood pressure. Incorrectly labeling a hypertensive patient as normotensive may increase risk for vascular events, since risk rises with increasing blood pressure. Labeling a patient with normal blood pressure as a hypertensive can affect insurability, employment, morbidity from medications, loss of time from work, and unnecessary lab and physician visits.

Systolic blood pressure level should be the major factor for the detection, evaluation, and treatment of hypertension, especially in adults 50 years and older. The purpose of a hypertensive patient evaluation is to identify other cardiovascular risk factors that may affect prognosis and guide treatment, find any identifiable causes of high blood pressure, and determine the presence or extent of target organ damage and cardiovascular disease. Patients with hypertension are evaluated through medical history, physical examination, routine laboratory tests and other diagnostic procedures.

In order to properly diagnose a patient, the recommended laboratory tests include

• 12-lead electrocardiogram
• Urinalysis
• Blood glucose
• Hematocrit
• Serum potassium
• Creatinine
• Electrolytes
• Uric acid
• Lipoprotein profile (after 9- to 12-hour fast).

Additional diagnostic tests may be performed to reveal causes of hypertension particularly in the event that a patient's medical history and examinations indicate a cause, blood pressure is unresponsive to drug treatment, blood pressure increases after being controlled, or onset was sudden. Currently, testing for microalbuminuria is limited primarily to patients with diabetes in order to screen for early nephropathy. The main indication for echocardiography is to detect suspected end-organ damage in a patient with borderline blood pressure values, who may not otherwise be treated based solely on clinical criteria.

Treatment

Hypertension is the most common primary diagnosis in America. Initial treatment for hypertension generally involves lifestyle modifications (nonpharmacologic therapy), which is also critical for prevention of the disease. Modifications encouraged for hypertensive patients include moderate dietary salt restriction, maintain body weight or weight reduction in obese patients, increased intake of fruits and vegetables and low-fat dairy products, limited alcohol intake, and regular aerobic exercise. Although effective control of blood pressure can be achieved in most patients with hypertension, the majority will require 2 or more antihypertensive drugs.

There are three main classes of drugs that are used for initial monotherapy (when no specific indication requires other treatment methods): thiazide diuretics, long-acting calcium channel blockers (usually a dihydropyridine), and ACE inhibitors or angiotensin II receptor blockers. In some cases, particularly with patients having moderate to severe hypertension, single agent therapy does not control the blood pressure. Over time, patients who were initially controlled with monotherapy need to increase treatment to a combined therapy in order for continued blood pressure control. The primary determinant of the outcome is the attained blood pressure, not the specific drug(s) used. The goal of antihypertensive therapy in patients with uncomplicated combined systolic and diastolic hypertension is a blood pressure of below 140/90 mmHg.