Abstract
Since the publication of a paper by the American Society of Hypertension, Inc. Writing Group in 2003, some refinements have occurred in the definition of hypertension. Blood pressure is now recognized as a biomarker for hypertension, and a distinction is made between the various stages of hypertension and global cardiovascular risk. This paper discusses the logic underlying the refinements in the definition of hypertension.
Hypertension is usually defined by the presence of a chronic elevation of systemic arterial pressure above a certain threshold value. However, increasing evidence indicates that the cardiovascular (CV) risk associated with elevation of blood pressure (BP) above approximately 115/75 mm Hg increases in a log‐linear fashion. 1 , 2 , 3 , 4 , 5 In the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) a category of “prehypertension” was created using BP criteria of 120/80 mm Hg to 139/89 mm Hg. 6 This category did not emphasize that some individuals with prehypertension already had the disease, hypertension, while others did not. In 2003, a writing group,7 offered a written definition of hypertension that did not depend on threshold values of BP above optimal. The purpose of this present position paper is to further refine and update the definition and classification of hypertension. It should be noted that while definitions of disease are useful for detection, management, research, and education, definitions alone do not constitute recommendations for treatment.
Definition of hypertension
Hypertension is a progressive CV syndrome arising from complex and interrelated etiologies. Early markers of the syndrome are often present before BP elevation is sustained; therefore, hypertension cannot be classified solely by discrete BP thresholds. Progression is strongly associated with functional and structural cardiac and vascular abnormalities that damage the heart, kidneys, brain, vasculature, and other organs and lead to premature morbidity and death. 7 Reduction of BP when target organ damage is demonstrable or the functional precursor of target organ damage is present and still reversible generally reduces the risk for CV events. Note that we separate elevated BP (one manifestation of the disease) from hypertension (the disease).
Stages of hypertension
Staging of a disease process such as hypertension is an assessment of the extent to which the disease has advanced at a particular time, that is, it is a “snapshot” of the pathophysiologic process. On the other hand, total CV risk assessment is an attempt to predict the future likelihood of the occurrence of a CV event such as myocardial infarction or stroke. Staging of hypertension and total CV risk assessment are related but not identical.
Individuals are either normal or hypertensive based on their CV status. The progression of hypertension—from early to advanced—may be represented as stages 1, 2, and 3 hypertension. Each stage of hypertension is characterized by the cumulative presence or absence of markers of hypertensive CV disease (CVD) and evidence of target organ damage regardless of the BP level. For example, progression includes such parameters as microalbuminuria or evidence of left ventricular hypertrophy. The occurrence of a major CV event clearly places the progression of the disease in a more advanced category.
BP as a Biomarker for Hypertension
BP serves as a biomarker for the disease hypertension. However, individuals with the same levels of BP might have different stages of hypertension (Table I). Furthermore, some individuals may exhibit elevated BP in the absence of hypertension. For purposes of calculating total CV risk, BP should be evaluated in the context of other CV risk factors and disease markers.
Table I.
Definition and Classification of Hypertension
| Classification | Normal | Stage 1 Hypertension | Stage 2 Hypertension | Stage 3 Hypertension |
|---|---|---|---|---|
| Descriptive category | Normal blood pressure or rare blood pressure elevations and no identifiable cardiovascular diseasea | Occasional or intermittent blood pressure elevations and early cardiovascular diseasea | Sustained blood pressure elevations or progressive cardiovascular diseasea | Marked and sustained blood pressure elevations or advanced cardiovascular diseasea |
| Cardiovascular risk factors (Table II) | None or few | Several risk factors present | Many risk factors present | Many risk factors present |
| Early disease markers (Table III) | None | Usually present | Overtly present | Overtly present with progression |
| Target organ disease (Table IV) | None | None | Early signs present | Overtly present with or without CVD events |
Definition and classification of hypertension by classifying individuals by blood pressure level or cardiovascular status; however, priority is given to cardiovascular status. aCardiovascular disease designation is determined by the constellation of risk factors, early disease markers, and target organ disease as listed in II, III, IV.
Classification of Hypertension
American Society of Hypertension: Normal
Individuals with optimal levels of BP and no identifiable early markers of CVD are considered by the American Society of Hypertension (ASH) as normal. Resting average BP levels are usually <120/80 mm Hg, but occasional elevated BPs (even to levels ≥140/90 mm Hg) may occur in these individuals. Some individuals designated as having prehypertension by JNC 7 will be classified as normal in the ASH paradigm. Accurate diagnosis in some individuals may be assisted by home BP determinations or 24‐hour ambulatory BP recordings (ASH position paper on ABPM 8 ).
ASH Stage 1 Hypertension: Characterized by Early CVD Markers
ASH stage 1 hypertension is the earliest identifiable stage of hypertensive disease and generally arises from circulatory, vascular, or renal adaptations to environmental or genetic stimuli. This stage is often characterized by early signs of functional or structural changes in the heart or small arteries. BP levels are above 115/75 mm Hg and may be elevated, particularly with environmental stress. Patients frequently have more than 1 CV risk factor (Table II). This category is applied only to those individuals with early disease markers (Table III), who do not show any evidence of target organ damage (Table IV).
Table II.
Cardiovascular Risk Factors
| Increasing age |
| Elevated blood pressurea |
| High heart rate |
| Overweight/obesity |
| Increased body mass index |
| Central obesity |
| Increased abdominal circumference |
| Increased abdominal adiposity (waist‐to‐hip ratio)a |
| Dyslipidemia |
| Elevated LDL or non‐HDL cholesterol |
| Low HDL cholesterola |
| Elevated triglyceridesa |
| Elevated blood glucose, insulin resistance, or diabetesa |
| Chronic kidney disease |
| Smoking |
| Family history of premature CVD (<age 50 y in men, <age 60 y in women) |
| Sedentary lifestyle |
| Psychosocial stressors |
| Elevated hs‐CRP |
Abbreviations: CVD, cardiovascular disease; HDL, high‐density lipoprotein; hs‐CRP, high‐sensitivity C‐reactive protein; LDL, low‐density lipoprotein; non‐HDL cholesterol, total cholesterol − HDL cholesterol. aComponents of the metabolic syndrome.
Table III.
Early Markers of Hypertensive Cardiovascular Disease
| System | Physiologic Alteration |
|---|---|
| Blood pressure | Loss of nocturnal blood pressure dipping |
| Exaggerated blood pressure responses to exercise or mental stress | |
| Salt sensitivity | |
| Widened pulse pressure | |
| Cardiac | Left ventricular hypertrophy (mild) |
| Increased atrial filling pressure | |
| Decreased diastolic relaxation | |
| Increased natriuretic peptide | |
| Vascular | Increased central arterial stiffness or pulse wave velocity |
| Small artery stiffness | |
| Increased systemic vascular resistance | |
| Increased wave reflection and systolic pressure augmentation | |
| Increased carotid intimal‐media thickness | |
| Coronary calcification or stenoses by computed tomographic angiography | |
| Endothelial dysfunction | |
| Capillary rarefaction | |
| Renal | Microalbuminuria (urinary albumin excretion of 30–300 mg/d)a |
| Elevated serum creatinine | |
| Reduced estimated GFR (60–90 mL/min) | |
| Retinal | Hypertensive retinal changes |
Abbreviation: GFR, glomerular filtration rate. aAlso a marker of microcirculatory disease.
Table IV.
Hypertensive Target Organ Damage and Overt Cardiovascular Disease
| System | Evidence Of Target Organ Damage And Cardiovascular Disease |
|---|---|
| Cardiac | Left ventricular hypertrophy (moderate to severe) |
| Systolic or diastolic cardiac dysfunction | |
| Symptomatic heart failure | |
| Myocardial infarction | |
| Angina pectoris | |
| Ischemic heart disease or prior revascularization | |
| Vasculature | Peripheral arterial disease |
| Carotid arterial disease | |
| Aortic aneurysm | |
| Wide pulse pressure (>65 mm Hg) | |
| Renal | Albuminuria (urinary albumin excretion >300 mg/d) |
| Chronic kidney disease (estimated GFR <60 mL/min) or ESRD | |
| Cerebrovascular | Stroke |
| Transient ischemic attack | |
| Decreased cognitive function | |
| Dementia | |
| Loss of vision |
Abbreviations: ESRD, end‐stage renal disease; GFR, glomerular filtration rate.
ASH stage 1 hypertension is a critical stage to investigate on two fronts: first, to bring specific and sensitive cost‐effective tests that can detect early CVD markers (Table III) into the clinic setting and, second, to determine whether early vascular derangements can be attenuated or reversed before the onset of target organ damage or overt CVD.
ASH Stage 2 Hypertension: Characterized by Diffuse Disease Markers
Individuals with ASH stage 2 hypertension (JNC 7 stage 1 hypertension) frequently have sustained resting BP levels ≥140/90 mm Hg, with much higher elevations induced by physiologic or psychologic stressors. However, individuals with numerous disease markers (Table III) or limited evidence of early target organ damage such as left ventricular hypertrophy (Table IV) are included in this group regardless of BP levels.
ASH stage 2 hypertension indicates that progressive disease has developed as a consequence of persistent functional and structural changes in BP control mechanisms and in the heart and vasculature. Some of the early target organ damage characteristic of this stage of hypertension can be detected with specialized or research studies, which should be evaluated further to determine their potential utility and cost‐effectiveness in clinical settings. Risk factors that are associated with ASH stage 2 hypertension, if not modified, continue to contribute to progressive target organ disease.
ASH Stage 3 Hypertension: Overt CVD
Untreated individuals with ASH stage 3 hypertension (JNC 7 stage 2 hypertension) usually have sustained resting BP levels ≥140/90 mm Hg, and marked elevations to levels >160/100 mm Hg are common. All individuals with clinical evidence of overt target organ damage (Table IV) or CVD are included in this category, as well as those who have already sustained CV events, regardless of BP levels.
ASH stage 3 hypertension is an advanced stage of the hypertensive continuum in which overt target organ damage is demonstrable and CV events may have already occurred or are imminent. Aging and the persistence of other identifiable risk factors together with a BP elevation, if present, exacerbate and accelerate the risk of morbidity and mortality. Management strategies for this phase of hypertension are well described. 6 Reaching this stage of hypertension means that damage to target organs as well as overt vascular, cardiac, and renal disease have already occurred or are imminent. Vigorous attempts at BP lowering as well as aggressive management of other CVD risk factors must be started promptly and sustained in these individuals to prevent or delay further progression.
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