Chronic hypertension overview

# Overview
Arterial blood pressure (BP) is a measure of the force exerted by the blood on the arterial walls. It is the function of both the cardiac output (CO) and the systemic vascular resistance (SVR). The maintenance of a normal blood pressure value is crucial to ensure appropriate blood circulation throughout the cardiovascular system. Arterial BP is considered one of the most important vital signs in the clinical setting.
Hypertension (HTN) is generally defined as an elevated systolic blood pressure (SBP)  140 mmHg and/or diastolic blood pressure (DBP)  90 mmHg at each of two or more visits. However, target BP values are set at a lower threshold in specific populations, such as diabetics and subjects with significant proteinuria and other renal diseases.

# Classification
In 2004, the Seventh Report of the Joint National Committee (JNC 7) classified blood pressure values into 4 categories: normal, prehypertension, stage I hypertension, and stage II hypertension. In 2007, the Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and the European Society of Cardiology (ESC) classified blood pressure into 7 categories. This classification remained unchanged in the 2013 ESH/ESC classification. The ESH/ESC classification excludes JNC 7s pre-hypertension category, but includes 3 different grades of hypertension in contrast to JNC 7s two-stage classification of hypertension.

# Pathophysiology
Although the pathophysiology of secondary hypertension has been outlined, there is still much debate about the true pathogenesis of primary (essential) hypertension. It is now conceded that hypertension is caused by multiple genetic and environmental factors with varying roles between individuals.

# Causes
The prevalence of primary hypertension is much more common than secondary hypertension, where only 5-10% of hypertension cases are diagnosed as secondary hypertension. When a full evaluation yields no clear etiology for the hypertension, the latter is thus identified as primary or essential hypertension. It is considered a chronic disease that requires lifetime treatment and management. If an underlying disease is identifiable as the cause of hypertension, the latter is called secondary hypertension. Causes of secondary hypertension include obstructive sleep apnea, hyperaldosteronism, kidney diseases, excess catecholamines, coarctation, cushing syndrome among other diseases.

# Differentiating Hypertension from other Diseases
Before the diagnosis of primary (essential) hypertension, secondary causes of hypertension should be ruled out. Additionally, other conditions that may elevate BP include: White coat hypertension, masked hypertension, and pseudohypertension.

# Epidemiology and Demographics
Hypertension is considered an epidemic worldwide. It continues to be one of the most common diseases. In October 2013, CDC data from the 2011-2012 National Health And Nutrition Examination Survey (NHANES) demonstrated that the overall age-adjusted prevalence of hypertension among U.S. adults aged 18 and older was 29.1%. Similar surveys conducted in Europe estimated the prevalence of hypertension to be 44%. The prevalence of hypertension increases among older patients and among non-Hispanic black patients, but is similar in both genders.

# Risk Factors
Established risk factors for essential hypertension include old age, male gender, African American ethnicity, dyslipidemia, diabetes mellitus, smoking, increased salt intake in diet, obesity, and sedentary lifestyle. Studies are currently assessing the role of new emerging factors that might be considered as new risk factors for the development of hypertension.

# Screening
The age to begin screening for hypertension varies between 13-20 years of age, according to different authorities. Generally, hypertension is defined as SBP > 140 mmHg and/or DBP > 90 mmHg. In specific populations, however, routine follow-up target BP may be different; and initiation of treatment may be considered at even lower BP values than those considered for the normal population.

# Natural History, Complications and Prognosis
Hypertension is a well-established risk factor for several serious diseases. Chronic uncontrolled hypertension can be complicated by target organ damage. Most common damaged organs include the cardiovascular system, the brain, the kidneys, and the retina. Even moderate elevation of arterial blood pressure leads to a shortened life expectancy. The risk of cardiovascular complications is significantly increased even with small incremental increases in blood pressures. Blood pressure values should never be regarded as distinct stages or grades, but rather as a continuum of risk. Ultimately, hypertension should never be evaluated in isolation as a cardiovascular risk; it should always be integrated with other risk factors for the decision of optimal management and how aggressive the lowering of blood pressure values must reach.

# Diagnosis

## History
Thorough history-taking is crucial for the diagnosis and assessment of hypertension. Not only should history-taking be targeted to identify symptoms consistent with high blood pressure, but more importantly it should address risk factors and target organ damage. History-taking alone may be sufficient to diagnose some causes of secondary hypertension, such as drug-induced hypertension, and may guide healthcare providers towards individualized work-up and tailored management.

## Physical Examination
Physical examination of a patient with isolated hypertension in the absence of target organ damage is usually unimpressive with the exception of high blood pressure. Healthcare providers must nonetheless search thoroughly for findings on physical examination that might suggest target organ damage and associated clinical conditions.

## Blood Pressure Measurement
The use of a sphygmomanometer in the clinic to measure blood pressure is the most accurate technique to diagnose hypertension. Blood pressure measurements must be performed appropriately according to a standardized technique that involves adequate device and cuff choice and comfortable positions. Sources of error, involving the sphygmomanometer, the patient, and the technique itself must also be considered and avoided. Other techniques for diagnosis, such as ambulatory and self blood pressure measurements may also be helpful, particularly for the follow-up of patients with hypertension.

## Laboratory Findings
Laboratory studies are often undertaken to identify possible causes of secondary hypertension, and seek evidence for end-organ damage to the heart itself or the eyes (retina) and kidneys. Diabetes and raised cholesterol levels being additional risk factors for the development of cardiovascular disease are also tested for as they will also require management.

## Electrocardiography
An electrocardiogram (EKG/ECG) is performed to evaluate for the presence of left ventricular hypertrophy or silent myocardial infarction.

## Echocardgiography
On 2D echocardiography, signs of LVH and heart failure are mostly seen in hypertensive patients.

## Chest X Ray
A chest X-ray may show signs of congestive heart failure, such as cardiomegaly, pulmonary edema, and Kirley B lines.

# Treatment

## Lifestyle Modification
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.

## Medical Therapy
Medical therapy is considered the most efficient means for the reduction of both systolic and diastolic blood pressure values in patients with hypertension. The two most important approaches for pharmacologic therapy in hypertension are proposed by JNC-7 guidelines in 2004 and more recently by the ESH/ESC guidelines in 2013. With the emergence of recent data, a major shift from the classical use of thiazide-type diuretics as first line therapy for patients with isolated essential hypertension has occurred. Recent guidelines currently encourage the use of any anti-hypertensive agent for isolated essential hypertension. Nonetheless, various conditions warrant the use of specific classes that have been found to have compelling indications in certain diseases and among specific patient populations.