Difficult-to-treat hypertensive populations: focus on African-Americans and people with type 2 diabetes

The awareness, treatment, and control of hypertension has risen steadily over the past three decades, until the early 1990s. However, blood pressure control to < 140/90 mmHg is attained in fewer than 25% of all hypertensive patients and fewer than 50% of drug-treated hypertensive patients, except for white women. Two special populations, African-Americans and diabetics, share several important attributes. First, they both have a high prevalence of hypertension, including stage 3 hypertension (as defined by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of Hypertension VI: > or =180/110 mmHg), relative to other subgroups. African-Americans have an approximate 8% prevalence of stage 3 hypertension, and elevated systolic blood pressure is highly prevalent among diabetic people, particularly older African-American women. Second, both groups have high levels of blood-pressure-related target-organ damage, which contributes to their inordinately high absolute risk for cardiovascular disease complications (i.e. stroke, congestive heart failure, renal failure) at a given level of blood pressure. Moreover, the reduced natriuretic capacity common to each group contributes to the attenuated efficacy of antihypertensive drug monotherapy, particularly for drug classes other than diuretics and calcium antagonists. These two special populations are also typically salt-sensitive, an intermediate blood pressure phenotype that raises blood pressure medication requirements. This phenomenon has been associated with an attenuation in the normal nocturnal fall in blood pressure. The high absolute risk for cardiovascular disease among diabetics led to the formulation of more aggressive treatment recommendations for antihypertensive drug therapy. In diabetics, blood pressure therapy is initiated at blood pressures > or = 130/85 mmHg, and treatment goals are at least to this level, unless proteinuria is > or = 1g/day (in which case the goals are < 125/75 mmHg). The more aggressive treatment targets for diabetics will not be reached with most currently available single antihypertensive agents in many African-Americans. While at best only 50-60% of hypertensive patients can be controlled with single drug therapy, that percentage falls dramatically in persons with stage 3 hypertension and renal insufficiency, thereby necessitating the use of combination drug therapy. Treatment alone is not enough; treatment to goal blood pressure is an essential first step towards optimal target-organ protection. While circulating levels of renin are suppressed, in general, in these special populations, each group manifests an inordinate burden of blood-pressure-related target-organ damage that has been linked to excessive levels of angiotensin II or a reduced bradykinin and nitric oxide tissue effect. The renin-angiotensin-aldo-sterone-kinin system is therefore an attractive therapeutic target that might conceivably provide target-organ protection over and above that attributable solely to lowering the blood pressure.