16: Hypertension

Key Points

• Disease summary:

  • Hypertension is a disease than can be caused by mutations in single genes (monogenic hypertension), nonidentifiable causes (essential hypertension) or secondary to other diseases (secondary hypertension).

  • Essential (primary) and secondary hypertension: It accounts for 95% of all cases of hypertension, and is traditionally defined as high blood pressure for which an obvious secondary cause cannot be determined. However, several gene variants are claimed to cause essential hypertension. In the remaining 5% of the cases, the cause of hypertension is secondary to conditions such as primary hyperaldosteronism, excess glucocorticoids, pheochromocytoma, or renal disease.

  • Monogenic hypertension: Most monogenic forms of hypertension have renal origins. The consequence of a defective gene in each of these forms of hypertension is abnormally increased sodium transport in the distal nephron causing an expansion of the circulating plasma volume and increase in cardiac output (Table 16-1). All hereditary forms of hypertension lead to a suppression of the renin-angiotensin system due to plasma volume expansion.

  • The estimated prevalence of hypertension (in the United States derived from the NHANES 2005-2008) in adults 20 years or older is 33.5% (28.5% ≥18 years) which is approximately 76 million US adults and nearly equal between men (34.1%) and women (32.7%). The prevalence of hypertension varies by age, gender, and race or ethnicity and is also affected by behavior such as the intake of dietary sodium and potassium, weight, waist to hip ratio, alcohol consumption, and physical activity. The prevalence of essential hypertension is highest in non-Hispanic Blacks (43%-46%) and lowest in Asian Americans (30%). Among Americans 65 years and older, more women than men have hypertension.

  • Blood pressure is regulated by a complex group of interacting genes and essential hypertension is a polygenic disease. About half of the blood pressure variability is thought to be genetically determined but the variation of blood pressure is the result of an interaction among genes and environmental factors.

  • Early fetal environment may be linked to long-term health and lifespan consequences in the adult, including essential hypertension. Low birth weight babies have higher blood pressures, even after correction for various modifiers such as sex, cigarette smoking, and weight.

  • Hypertension is strongly associated with major cardiovascular risks such as premature cardiovascular disease, congestive heart failure, left ventricular hypertrophy, stroke, chronic kidney disease, and end-stage renal disease. In 2008, high blood pressure was responsible for about one in six deaths of US adults and was the single largest risk factor for cardiovascular mortality, accounting for about 45% of all cardiovascular deaths.

• Differential diagnosis:

  • The correct measurement of blood pressure, including the use of an appropriately sized cuff and sphygmomanometer that is properly calibrated and validated is critical.

• Family history:

  • Blood pressure heritability estimated from family studies is about 20%. The predictive strength of family history as a risk factor is doubled with one hypertensive first-degree relative and increases nearly fourfold with two such relatives.

• Twin studies:...