• Primary hypertension in adults aged 18 years and older is defined as blood pressure of 140/90 mm Hg or more, based on an average of two or more properly measured seated blood pressure (BP) readings at each of two or more clinic visits.
  
• Normal BP is a systolic BP (SBP) <120 mm Hg and diastolic BP (DBP) <80 mm Hg.
  
• Prehypertension is defined as an SBP of 120–139 mm Hg or DBP of 80–89 mm Hg.
  
• Stage 1 hypertension is defined by an elevation in either SBP 140–159 mm Hg or diastolic BP of 90–99 mm Hg.
  
• Stage 2 hypertension is defined by an elevation in either SBP of ≥160 mm Hg or DBP of ≥100 mm Hg.
  
• The level of BP alone is inadequate for diagnosis and it should be interpreted in the context of the overall cardiovascular risk of the patient, which is most easily estimated by evaluating other concomitant disorders and target-organ damage (TOD).

Hypertension affects more than 29% adult Americans and is the most common reason for office visits to physicians in the United States. The prevalence of hypertension is expected to increase largely due to the epidemic of obesity and the aging population in the United States. Indeed, data from the Framingham health study suggest that people with a normal BP (<120/80 mm Hg) at 55 years of age have a 90% lifetime risk of developing hypertension. Additionally, it is now well established that a linear relationship exists between BP and risk of cardiovascular events, thus the more elevated the BP the greater the likelihood of myocardial infarction, congestive heart failure, kidney failure, or stroke.

Despite the increased prevalence of hypertension and its associated morbidity and mortality, current control rates are inadequate. Only 34% of people with hypertension have their BP controlled to a goal of BP < 140/90 mm Hg. Key factors for the inadequate BP control include failure of physicians to prescribe (1) lifestyle modifications, (2) adequate doses of antihypertensive medications, and (3) appropriate drug combinations and increased occurrence of pure systolic hypertension in the elderly, which is considerably more difficult to treat.

Risk Factors

The Joint National Committee (JNC) 7 recommends that specific public health interventions such as decreasing calories, saturated fat, and salt intake, especially in processed foods, and increasing physical activity be strongly encouraged at school and community levels. This strategy can achieve a downward shift in the distribution of a population’s BP and thus potentially decrease the lifetime risk of morbidity and mortality from hypertension in an individual.

Measurement of Blood Pressure

Accurate measurement and interpretation of BP is crucial for the diagnosis and treatment of hypertension. The recommendations outlined below will help standardize the technique and improve the accuracy of BP readings:

• Patients should abstain from drinking caffeine or alcohol-containing beverages or using tobacco within 30 minutes prior to a BP measurement.
  
• The cuff size appropriate for the patient’s arm circumference should be used (the cuff bladder should encircle at least 80% of the arm).
  
• The cuff bladder should be centered over the brachial artery, with its lower edge within 2.5 cm of the antecubital fossa.
  
• Listen over the brachial artery using the bell of the stethoscope with minimal pressure exerted on the skin. Inflate the cuff 20 mm Hg higher than the pressure at which the palpable pulse at the radial artery disappears. Use a properly calibrated syphgmomanometer.
  
• The deflation rate of the column of mercury should be 2–3 mm Hg/second.
  
• Multiple measurements should be made on different occasions in the sitting position with the back supported for 5 minutes and the arm at heart level.
  
• At least two readings should be taken on each visit separated by as much time as possible.
  
• Attempt to avoid “terminal digit preference” (more than 20% of measurements ending with a specific even digit).
  
• Measure BP in both arms initially, and in the arm with the higher BP thereafter if the difference is greater than 10/5 mm Hg.

Home Blood Pressure Measurements

Home BP measurements are indicated for (1) evaluating white-coat hypertension, (2) assessing TOD in response to antihypertensive drug therapy, and (3) improving patients’ adherence to therapy. Home BP readings are typically lower (by an average of 12/7 mm Hg), and correlate better with a risk of future mortality, than office BP measurements. Persons with home BP readings of >135/85 mm Hg are generally considered to have hypertension.

Ambulatory Blood Pressure Monitoring

Ambulatory BP readings provide BP data during daily activities and sleep and correlate better than home or office readings with TOD, left ventricular hypertrophy (LVH), and cardiovascular event rates. They are indicated for the evaluation of white-coat hypertension in the absence of TOD, episodic hypertension, apparent drug-resistant hypertension, drug-induced hypotensive symptoms, and autonomic dysfunction. As in home BP readings patients are considered to have hypertension if their mean BP during the day is >135/85 mm Hg or >125/75 mm Hg during sleep. Recent outcome studies have demonstrated increased cardiovascular risk associated with abnormal ambulatory blood pressure monitoring (ABPM) profiles (eg, “nondipping” of BP at night).

White-Coat Hypertension

Approximately 25% of those with hypertension have BP readings that are considerably higher in the doctor’s office or hospital than those measured at home, at work, or by ABPM. This occurs more commonly among the elderly. The clinical consequences of this diagnosis are higher risk for cardiovascular events and related mortality as compared to normotensive, non-white-coat hypertension patients, but with a lower risk than those with primary hypertension. Twenty-four hour ambulatory monitoring is needed along with a normal physical examination to confirm the diagnosis. It has been suggested that such stimuli raise BP only transiently and reversibly while others think that these patients will all eventually become sustained hypertensives. Currently, lifestyle modifications with frequent BP monitoring are recommended.

Laboratory Findings

Patients with essential hypertension should undergo a limited work-up because extensive laboratory testing may be unrewarding.

Cardiac Tests

LVH is an objective measure of both the severity and duration of hypertension. It should be routinely evaluated in all patients with an electrocardiogram although an echocardiogram appears to be a better predictor of future cardiovascular events. Other initial laboratory tests include a 9–12 hour fasting lipid profile that includes high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides, hematocrit, and routine blood chemistries including glucose.

Kidney Function Tests

Current recommendations for evaluation of kidney function include a serum blood urea nitrogen and creatinine, estimated glomerular filtration rate (GFR), electrolytes, and spot urinalysis to detect red blood cells, white blood cells, casts, or proteinuria. Optional tests include measurement of urine albumin excretion or albumin/creatinine ratio and microalbuminuria (protein excretion between 30 and 300 mg/day). Note: All patients with even trace positive protein on routine dipstick should have a spot urine albumin:creatinine checked.

Special Examinations

The initial clinic evaluation of a person with elevated BP readings should include the following objectives:

• Determine an accurate diagnosis of hypertension.
  
• Define the presence or absence of TOD related to hypertension (Table 41–1).
  
• Screen for other cardiovascular (CV) risk factors or comorbidity that often accompany hypertension (Table 41–1).
  
• Stratify the risk for cardiovascular disease.
  
• Assess the likelihood of secondary hypertension and initiate further diagnostic testing to confirm or exclude the diagnosis.
  
• Obtain data that may be helpful in the choice of therapy and prognosis.