Chapter 40

Hypertension

Gabriel B. Habib, Sr., MD, MS, FACC, FAHA, FCCP

1. Define hypertension. What is the prevalence of hypertension in the United States, Mexico, and worldwide?

The Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure, in its seventh report (JNC 7), defined hypertension as an average of two or more diastolic readings more than 90 mm Hg on at least two consecutive visits, or an average of multiple systolic readings more than 140 mm Hg. Isolated systolic hypertension is diagnosed if systolic blood pressure (SBP) is more than 140 mm Hg with a diastolic blood pressure less than 90 mm Hg. A new category called prehypertension is now defined as a blood pressure less than the arbitrary cutoff of 140/90 mm Hg for hypertension but greater than an optimal blood pressure of 120/80 mm Hg. Patients with prehypertension, unlike hypertensive patients, do not require antihypertensive drug therapy, but should be counseled to start health-promoting lifestyle modifications aimed at preventing the development of hypertension. Hypertension is classified into 2 stages: stage I: 140/90 to 159/99 mm Hg and stage II 160/100 or higher. In the latest National Health and Nutrition Examination Survey 2005-2008, about 33% of adults 20 years of age or older have hypertension (Table 40-1).

TABLE 40-1

JNC 7 CATEGORIES OF HYPERTENSION

Category	Blood Pressure
Normal	<120/80 mm Hg
Prehypertension	120-130/80-89 mm Hg
Hypertension: Stage 1	140-159/90-99 mm Hg
Hypertension: Stage 2	≥160/100 mm Hg

Modified from Chobanian AV, Bakris GL, Black HR, et al: Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7), Bethesda, Md., 2003, National Institutes of Health, pp 54-55.

Prevalence of hypertension worldwide varies from as low as 3% of men in rural India to 72% of men in Poland. Hypertension prevalence is about the same in the United States and Mexico, at about 33% of the adult population.

2. What are the goals of hypertension treatment?

Reducing elevated blood pressure levels is an important strategy to prevent various complications of systemic hypertension, such as stroke, myocardial infarction (MI), heart failure, and renal disease. The best predictor of the efficacy in preventing various cardiorenal complications is the degree of reduction of blood pressure. The risk of death from ischemic heart disease or stroke in cohort longitudinal studies is lowest at a blood pressure of approximately 115/75 mm Hg and doubles beginning at 115/75 mm Hg with each 20 mm Hg increment in SBP.

Although blood pressure less than 120/80 mm Hg is associated in observational cohort studies with the lowest risk of death from ischemic heart disease and stroke, the goal of blood pressure treatment recommended by JNC 7 (2001) is a blood pressure less than 140/90 mm Hg in patients with uncomplicated hypertension, and less than 130/80 mm Hg in higher risk hypertensive patients with chronic kidney disease and/or diabetes mellitus.

The American Heart Association (AHA) Task Force released a scientific statement in 2007 for the treatment of hypertension in the prevention of coronary artery disease (CAD). This AHA Task Force recommended more aggressive control of blood pressure among those at high risk for CAD: individuals with diabetes mellitus, chronic kidney disease (as recommended in JNC 7), but also in patients with cardiovascular disease, congestive heart failure, or a 10-year Framingham risk score of 10% or more. These individuals are advised to maintain a blood pressure less than 130/80 mm Hg. Moreover, the AHA Task Force recommended a goal blood pressure of less than 120/80 in patients with congestive heart failure.

Targeting an SBP of less than 120 mm Hg, as compared with less than 140 mm Hg, in patients with type 2 diabetes mellitus did not reduce the rate of a composite outcome of fatal and nonfatal major cardiovascular events in the recently reported Action to Control Cardiovascular Risk in Diabetes (ACCORD) blood pressure trial. However, SBP less than 120 mm Hg did significantly reduce stroke risk, a secondary study endpoint. Thus, it is NOT recommended at this time to target SBP less than 120 mm Hg in type 2 diabetic patients.

3. Is systolic or diastolic blood pressure more powerful as a predictor of cardiovascular complications of hypertension?

Systolic and diastolic blood pressure levels are independently predictive of the risk of cardiovascular complications in hypertensive patients. However, SBP is more powerful in predicting cardiovascular complications, particularly in patients over the age of 50 years. Pulse pressure—the difference between systolic and diastolic blood pressure—is also an independent predictor of cardiovascular complications. A wide pulse pressure is usually indicative of a noncompliant stiff aorta with a reduced ability to distend and recoil back. Thus, during systolic ejection of blood from the left ventricle into the aorta and systemic circulation, the aorta does not distend and the force of ejection is transmitted more forcefully into the peripheral vessels, thus causing an exaggerated SBP level recording. During diastole, the elastic recoil of the aorta is more limited, contributing to a lower diastolic blood pressure. Thus, a noncompliant aorta would increase SBP and reduce diastolic blood pressure, resulting in a widened pulse pressure.

4. You have diagnosed a new case of hypertension. What is your next step?

Arterioles are the vessels that sustain the most damage from persistent elevation of blood pressure. Therefore, the first step is to do a damage assessment by evaluating the target organs of hypertension, keeping in mind that their involvement is an expression of arteriolar damage with subsequent ischemia and ischemia-induced changes.

Kidney: Signs of involvement range from minimal proteinuria or slight increase of serum creatinine to end-stage renal disease. Kidney size is evaluated by a variety of imaging methods and has prognostic significance. Hypertension is the second leading cause of renal failure in the United States, particularly in African Americans.

Brain: The eye fundus appearance is the mirror of the brain circulation. Findings range from minor atherosclerotic changes to papilledema and hemorrhages, which can be seen with severe hypertension and hypertensive crisis. A careful neurologic examination may reveal signs of previously undiagnosed strokes, and history may reveal previous transient ischemic attacks.

Heart: The direct consequence is left ventricular hypertrophy (LVH) with increased left ventricular (LV) mass; this is easily documented by electrocardiogram (ECG), two-dimensional, and M-mode echocardiogram or cardiac magnetic resonance imaging (MRI). LVH is strongly associated with an increased risk of sudden death and MI, and constitutes the basis for decreased LV compliance and subsequent diastolic dysfunction. A thorough evaluation for the presence of CAD, guided by a skillful interview, is required. Holter monitoring may be necessary for evaluating LVH-associated arrhythmias. The last step in the natural history of the disease is LV dilation and pump failure, with the classical signs of congestive heart failure (CHF).

5. What is resistant hypertension and how prevalent is it?

Resistant hypertension is defined as blood pressure that remains above goal in spite of the concurrent use of three antihypertensive agents of different classes. Ideally, one of the three agents should be a diuretic and all agents should be prescribed at optimal dose amounts. Resistant hypertension identifies patients who are at risk of having reversible causes of hypertension or patients who, by virtue of persistently elevated blood pressure levels, may benefit from special diagnostic and therapeutic considerations. In a recent analysis of the National Health and Nutrition Examination Survey (NHANES), only 53% of hypertensive patients were controlled to less than 140/90; the majority of the remaining 47% of these patients probably have resistant hypertension. While the exact prevalence of resistant hypertension is unknown, it is estimated from published hypertension clinical trials, including the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack (ALLHAT) trial, that about 20% to 30% of hypertensive patients have resistant hypertension.

Factors recognized to be associated with resistant hypertension include older age, high baseline blood pressure, obesity, excessive dietary salt ingestion, chronic kidney disease, diabetes mellitus, LVH, African American race, female gender, and residence in southeastern U.S. regions (Box 40-1). Medications that interfere with blood pressure control (Box 40-2), such as nonsteroidal antiinflammatory drugs (NSAIDs), should be specifically inquired about in hypertensive poorly controlled patients.

Box 40-1 PATIENT CHARACTERISTICS ASSOCIATED WITH RESISTANT HYPERTENSION

Older age

High baseline blood pressure

Obesity

Excessive dietary salt ingestion

Chronic kidney disease

Diabetes

Left ventricular hypertrophy

Black race

Female sex

Residence in southeastern United States

From Calhoun D, Jones D, Textor D, et al: Resistant hypertension: diagnosis, evaluation, and treatment: a scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Hypertension 51:1403-1419, 2008.