Analysis of Recent Papers in Hypertension

Authors


Jan Basile, MD, Ralph H. Johnson VA Medical Center,
1090 Bee Street, Charleston, SC 29403

GAINING WEIGHT INCREASES THE RISK FOR THE DEVELOPMENT OF HEART FAILURE

Despite the fact that the death rate from coronary heart disease has decreased 60% over the past 40 years, the age-adjusted risk for developing congestive heart failure has continued to increase. Over this same time period, the risk of becoming obese has increased at epidemic proportions, affecting more than one third of Americans over 20 years of age. It has been unclear whether obesity is an independent risk factor for developing heart failure or whether this association is a result of other conditions, such as hypertension, dyslipidemia, or diabetes, which are so often found in obese subjects. Although this observation has been well studied at the extremes of obesity (body mass index [BMI] >40), the impact of having lesser degrees of obesity (BMI >30) or of being overweight (BMI 25–30) has remained unclear.

In the first major community-based study to investigate the risk of weight gain and the development of heart failure, investigators from the Framingham Heart Study studied 5881 men and women (mean age, 55 years; 5% women) with no evidence of heart failure at baseline. Beginning in 1976, over an average follow-up of 14 years, heart failure developed in 8% of the cohort. After adjusting for other risk factors known to be associated with the development of heart failure, i.e., smoking, high cholesterol, diabetes, and hypertension, it was noted that in people who were obese (BMI >30) there was a two-fold increase in the risk of heart failure. The risk of heart failure independently increased 5% for men and 7% for women for each unit increase in BMI >25. Those who were overweight but not obese (BMI 25–29.9) had a risk that was intermediate between the risk in normal-weight and obese subjects. Being obese (BMI >30) was independently responsible for 11% of the heart failure cases in men and 14% of the cases that occurred in women. Increased BMI remains a significant risk factor for developing heart failure. Strategies to promote ideal body weight may reduce this risk.—Kenchaiah S, Evans J, Levy D, et al. Obesity and the risk of heart failure. N Engl J Med. 2002;347:305–313.

Comment

Heart failure remains a major health problem associated with substantial morbidity and mortality. This observational analysis from the Framingham Heart Study suggests that a BMI ≥25 in both men and women may result in heart failure, and the risk of heart failure continues to increase with increasing levels of BMI. Although the precise mechanism(s) accounting for this causation is unclear, the authors suggest that there is experimental evidence associating weight gain with an increase in hemodynamic load, neurohormonal activation, increased oxidative stress, and cardiac steatosis associated with lipoapoptosis.

It is unclear whether or not the findings in this predominantly white sample can be generalized to other races and ethnic groups who are more likely to become obese. Black women continue to remain at greatest risk for obesity. Beginning at age 28, black men became obese 2.2-times faster than white men. Hispanic men and women are also more likely to develop obesity than their white counterparts. These groups also need to be studied for the association of weight gain and heart failure risk.

Americans are becoming obese at epidemic proportions with an estimated 61% of Americans ages 20–74 either overweight or obese. With obesity occurring at an earlier age, the early identification of individuals at risk for obesity may better prepare us to develop strategies that more effectively focus on those at greatest risk of developing heart failure. Intervention strategies to prevent obesity should target all ethnic groups at younger ages when they remain at highest risk for becoming obese. Obesity must not remain the No. 1 untreated disease in this country.

COFFEE INTAKE OVER 33 YEARS IS NOT ASSOCIATED WITH DEVELOPING HYPERTENSION

Drinking coffee acutely raises blood pressure; as a result it has been recommended that blood pressure not be taken within thirty minutes of coffee ingestion. Adaptation to the acute cardiovascular effects of coffee occurs promptly, with blood pressure quickly returning to baseline. However, whether chronic coffee ingestion increases the long-term risk of developing hypertension has never been studied.

As part of the Johns Hopkins Precursors Study, a prospective longitudinal study of former Hopkins medical students, the long-term effect of coffee drinking on the development of hypertension was assessed. Excluding women, because of the small number of graduates, 1017 normotensive white men (mean age 26 years) graduating between 1948 and 1964 supplied coffee information while in medical school. Through an annual questionnaire, caffeinated coffee intake was assessed at baseline by self-report ranging from zero to more than five cups of coffee. This questionnaire was repeated at least every 5 years, up to 11 times during follow-up.

Over a median of 33 years, 281 men developed hypertension at a median age of 53 years. Each cup of coffee per day was associated with a 0.21 mm Hg higher systolic and 0.26 mm Hg higher diastolic blood pressure. During follow-up, Cox analysis (adjusted for cigarettes smoked, alcohol intake, physical activity, and body mass index) found no association between coffee drinking and the development of hypertension.

Although coffee drinking is associated with small increases in blood pressure, the authors concluded that over many years of follow-up it plays a small role in the development of hypertension.—Klag M, Wang NY, Meoni L, et al. Coffee intake and risk of hypertension. Arch Intern Med. 2002;162:657–662.

Comment

The risks of coffee drinking and increased blood pressure have been pondered for many years. Although a recent meta-analysis of up to 1 years' duration found that coffee drinkers had slightly raised blood pressures when compared to nondrinkers, no prospective studies on coffee consumption and the risk of developing hypertension have been previously performed. In this prospective longitudinal study of former medical students, the ability to repeatedly measure coffee intake from young adulthood to age 60 as well as receive validated self-reports of developing hypertension, provided a unique opportunity to study this question.

Drinking one cup of coffee was associated with small increases in blood pressure. However, after adjusting for a number of factors associated with hypertension, long term coffee drinking was not associated with the risk of developing hypertension. Continued adaptation over the long period of follow-up may explain why the effect on systolic blood pressure is less than that seen in previous clinical trials. While coffee consumption may acutely raise blood pressure, studies have not found an increase in the risk of hemorrhagic stroke, a marker of uncontrolled hypertension, and coffee drinking.

Weaknesses of the study include those that are well known to occur in a format that uses a self-reported questionnaire, the fact that it is generalizeable only to white men of high socioeconomic status, and the fact that the amount of other dietary factors associated with hypertension, such as sodium, potassium, and fiber intake, were not known.

Despite the fact that cessation of coffee consumption in those with hypertension has been associated with reduction in blood pressure, drinking caffeinated coffee does not appear to play a major role in the incidence of hypertension.

SERIAL HEMODYNAMIC MEASUREMENTS ALLOW BETTER BLOOD PRESSURE CONTROL THAN CLINICAL JUDGMENT IN THOSE WITH REFRACTORY HYPERTENSION

While effective control of blood pressure lowers both stroke and cardiovascular mortality, only one in four hypertensive adult Americans have their blood pressure controlled to <140/90 mm Hg. As many as 13% of patients are referred to hypertension clinics for “resistant hypertension,” i.e., a blood pressure >140/90 mm Hg on three or more antihypertensive medications, one of which is a diuretic. The term is often used interchangeably with “refractory hypertension,” which refers to the inability to control blood pressure to <140/90 mm Hg with the use of two or more agents.

Investigators from the Mayo Clinic in Rochester, MN compared the use of serial noninvasive hemodynamic measurements (HD) with care delivered conventionally by a clinical hypertension specialist (SC) in an effort to improve the blood pressure control rates in those with refractory hypertension. Over a 30-month period, 104 patients (mean age 66; 48% male) with refractory hypertension were randomly assigned to a 3-month treatment period comparing HD with SC. Using thoracic bioimpedance, an instrument that detects changes in thoracic fluid volume during systole, real-time measurements of stroke volume were determined which, when coupled with heart rate and blood pressure measurements, can determine cardiac output and systemic vascular resistance. HD measurements were obtained in both groups at the initiation and end of the study but remained unavailable to the SC group. In addition, monthly measurements were taken for the HD group. Subjects in the HD group, based on the measurements made, were treated according to a predefined treatment algorithm with the selection and titration of antihypertensive medication made by a single physician.

With the average subject receiving 3.6 different medications at entry (range of 2–6 medications), including a diuretic in 91%, there were no differences in age, gender distribution, blood pressure, or renal function between treatment groups. While a secondary cause of hypertension was identified in 34% of subjects, they were equally distributed between treatment groups and treated medically until the end of the study period.

Blood pressure was favorably lowered by intensified drug therapy in both groups (169/87 to 139/72 mm Hg in the HD group compared to 173/91 to 147/79 mm Hg in the SC group). Achieved blood pressure levels were lower, however, for the HD group than the SC group (56% vs. 33% controlled to 140/90 mm Hg, respectively). While the final number of medications, total number of daily doses, and the number of office visits did not differ between the groups, the defined daily dose of diuretic was higher in the HD group.

The results demonstrate that better blood pressure control may occur over a 3-month treatment period by using hemodynamic measurements and a treatment algorithm compared to clinical judgment by a hypertension specialist. Measurements of thoracic fluid volume suggest occult volume expansion and the need for increasing diuretic use as the reason for differences between groups in blood pressure control.—Taler SJ, Textor SC, Augustine JE. Resistant hypertension: comparing hemodynamic measurement to specialist care. Hypertension. 2002;39:982–988.

Comment

Adequate control of blood pressure continues to elude the majority of practitioners caring for those with hypertension. Refractory hypertension, affecting only a minority of hypertensive patients, is associated with a disproportionately high risk of cardiovascular events. Despite the availability of more effective antihypertensive agents than ever before, refractory hypertension continues to pose management problems for the clinician. The use of noninvasive measurements to guide therapeutic decisions has been limited by the reproducibility of the results, cost, and the lack of improvement in outcome over clinically-based therapy.

In this short-term 3-month study, 56% of patients randomized to HD and 33% of those assigned to care under a clinical hypertension specialist had blood pressure controlled to <140/90 mm Hg. The better results using HD care at the final visit resulted from detection of higher peripheral resistance associated with volume expansion and the greater use of diuretic therapy to control blood pressure. As patients in both groups required the same number of medications (four or more), and similar number of clinic visits, better blood pressure control was a result of more changes in medication choices and treatment intensity in the HD care group.

Occult volume expansion often limits effective blood pressure control. HD care appeared to improve blood pressure control to a greater degree than specialist care in those with refractory hypertension. However, larger trials of longer duration using bioelectrical impedance at baseline will be necessary before hemodynamic-based care becomes ready for prime time. For now, in those with refractory hypertension, more frequent use of and larger doses of diuretics appear to be important in improving blood pressure control.

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