Evaluation of hypertension

Hypertension is a common disorder that affects a large proportion of the community. It is usually asymptomatic and is detected on routine exam or after the occurrence of a complication such as a heart attack or stroke. [1] Lip GY. Hypertension, platelets, and the endothelium: the "thrombotic paradox" of hypertension (or "Birmingham paradox") revisited. Hypertension. 2003;41:199-200. http://hyper.ahajournals.org/cgi/content/full/41/2/199 http://www.ncbi.nlm.nih.gov/pubmed/12574081?tool=bestpractice.com It is often referred to as the silent killer.

The definition of hypertension is based on recommendations by the American Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, [2] Chobanian AV, Bakris GL, Black HR, et al. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA. 2003;289:2560-2572. http://www.ncbi.nlm.nih.gov/pubmed/12748199?tool=bestpractice.com the British Society of Hypertension, [3] Williams B, Poulter NR, Brown MJ, et al. Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV. J Hum Hypertens. 2004;18:139-185. http://www.nature.com/jhh/journal/v18/n3/full/1001683a.html http://www.ncbi.nlm.nih.gov/pubmed/14973512?tool=bestpractice.com and the European Society of Hypertension. [4] Mancia G, Fagard R, Narkiewicz K, et al. 2013 ESH/ESC guidelines for the management of arterial hypertension: the Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC). Eur Heart J. 2013;34:2159-2219. http://eurheartj.oxfordjournals.org/content/34/28/2159.long http://www.ncbi.nlm.nih.gov/pubmed/23771844?tool=bestpractice.com There are slight differences in the definition of hypertension between guidelines.

• The American guidelines (JNC-7) state that a blood pressure <120/80 mmHg is normal, 120 to 139/80 to 89 mmHg is prehypertension, and anything above this is abnormal. Isolated systolic hypertension is defined as an elevated systolic blood pressure of >140 mmHg with a normal (<80 mmHg) diastolic pressure. It should be noted that the more recent Joint National Commission (JNC-8) guidelines recommended revised treatment thresholds but did not redefine diagnostic categories. [5] James PA, Oparil S, Carter BL, et al. 2014 evidence-based guideline for the management of high blood pressure in adults: report from the panel members appointed to the Eighth Joint National Committee (JNC 8). JAMA. 2014;311:507-520. http://jama.jamanetwork.com/article.aspx?articleid=1791497 http://www.ncbi.nlm.nih.gov/pubmed/24352797?tool=bestpractice.com

• The European and British guidelines have classified a blood pressure of <120/80 mmHg as optimal. 120 to 129/80 to 84 mmHg is normal, 130 to 139/85 to 89 mmHg is high normal, and anything above that is classified as hypertension and is divided into 3 stages:

  1. Stage 1: systolic 140 to 159 and/or diastolic 90 to 99 mmHg

  2. Stage 2: systolic 160 to 179 and/or diastolic 100 to 109 mmHg

  3. Stage 3: systolic 180 mmHg or higher and/or diastolic 110 mmHg or higher.

Isolated systolic hypertension is also graded according to systolic blood pressure values in the ranges indicated, provided that diastolic values are <90 mmHg.

Although different studies have used a variety of cut-off points for the diagnosis of hypertension in the community, any blood pressure over 120 mmHg systolic is associated with an increased cardiovascular risk. The importance of hypertension is its relation to other cardiovascular risk factors and consequent overall cardiovascular risk.

Epidemiology

In the US, data from the National Health and Nutrition Survey (NHANES) suggest hypertension has a mean prevalence of 29% in the population over 18 years of age, using a cut-off value of 140/90 mmHg. This ranges from around 7% in those ages 18 to 39 years to 66% in those ages >60 years. [6] Ong KL, Cheung BM, Man YB, et al. Prevalence, awareness, treatment, and control of hypertension among United States adults 1999-2004. Hypertension. 2007;49:69-75. http://hyper.ahajournals.org/cgi/content/full/49/1/69 http://www.ncbi.nlm.nih.gov/pubmed/17159087?tool=bestpractice.com The prevalence seems to be higher in Western Europe. [7] Wolf-Maier K, Cooper RS, Banegas JR, et al. Hypertension prevalence and blood pressure levels in 6 European countries, Canada, and the United States. JAMA. 2003;289:2363-2369. http://jama.ama-assn.org/cgi/content/full/289/18/2363 http://www.ncbi.nlm.nih.gov/pubmed/12746359?tool=bestpractice.com However, as elevated blood pressure is usually asymptomatic, the exact prevalence of hypertension is difficult to assess, and is expected to rise as the "cut-off" value for hypertension is redefined at a lower level.

Complications and target organ damage

Studies have shown that treatment of hypertension can reduce the incidence of future cardiovascular and cerebrovascular events. [8] Ogden LG, He J, Lydick E, et al. Long-term absolute benefit of lowering blood pressure in hypertensive patients according to the JNC VI risk stratification. Hypertension. 2000;35:539-543. http://hyper.ahajournals.org/cgi/content/full/35/2/539 http://www.ncbi.nlm.nih.gov/pubmed/10679494?tool=bestpractice.com The aim of early diagnosis and treatment of hypertension is to lower overall cardiovascular risk and prevent cerebrovascular events. The effects of chronic hypertension on organ systems are referred to as target organ damage.

Left ventricular hypertrophy, cardiovascular disease, cerebrovascular disease, hypertensive retinopathy, and nephropathy are the most common manifestations. [9] Nadar SK, Tayebjee MH, Meserelli F, et al. Target organ damage in hypertension: pathophysiology and implications for drug therapy. Curr Pharm Des. 2006;12:1581-1592. http://www.ncbi.nlm.nih.gov/pubmed/16729871?tool=bestpractice.com The presence of left ventricular hypertrophy is a poor prognostic sign, and regression of left ventricular hypertrophy improves prognosis. [10] Lewington S, Clarke R, Qizilbash N, et al. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002;360:1903-1913. http://www.ncbi.nlm.nih.gov/pubmed/12493255?tool=bestpractice.com

Cardiovascular risk

Guidelines on the management of hypertension emphasize the importance of calculating and managing the overall cardiovascular risk of a patient, rather than focusing only on blood pressure readings. For individuals ages 40 to 70 years, each increment of 20 mmHg in systolic blood pressure or 10 mmHg in diastolic blood pressure across the entire blood pressure range from 115/75 to 185/115 mmHg doubles the risk of cardiovascular disease. [11] Blair SN, Goodyear NN, Gibbons LW, et al. Physical fitness and incidence of hypertension in healthy normotensive men and women. JAMA. 1984;252:487-490. http://www.ncbi.nlm.nih.gov/pubmed/6737638?tool=bestpractice.com Treating associated cardiovascular risk factors such as obesity, diabetes, hypercholesterolemia, and smoking are as important as managing hypertension in lowering overall cardiovascular risk.