Natural History of Hypertension Subtypes

Abstract

The relation between blood pressure (BP) and the risk of cardiovascular disease is direct, graded, and continuous over a wide range, apparently beginning at 115 mm Hg systolic and 75 mm Hg diastolic.1 Despite such a continuous relation, some working definitions, or subtypes, of hypertension have gained wide clinical acceptance. Experimental and clinical data support the notion that the hypertension subtypes defined by isolated or combined elevations of systolic and diastolic BP reflect distinct pathophysiological mechanisms, have different prognostic implications, and may require a different therapeutic approach.2–4 See p 1121 An increase in the stiffness of the aorta and large elastic arteries not accompanied by a rise in arteriolar resistance may lead to isolated systolic hypertension (ISH). In contrast, a predominant rise in arteriolar resistance may lead to combined systo-diastolic hypertension (SDH) if large artery stiffness also increases, or to isolated diastolic hypertension (IDH) if arterial stiffness is normal or low. Thus, IDH might be viewed as a marker of a good elasticity of aorta and large arteries, possibly because of a paucity of atherosclerotic lesions.5 In contrast, because the rigidity of the aorta and large arteries tends to increase with age, systolic BP also tends to increase with age, leading to an elevated frequency of ISH in the elderly.6,7 The decline of diastolic BP with age has been associated with progression of aortic atherosclerosis, defined in one study by the appearance of new calcifications or enlargement of old calcified areas.8 A confounding factor in the assessment of hypertension subtypes is the progressive amplification of the pressure wave during transmission from aorta to peripheral arteries, a phenomenon that is predominant in the young and decreases with aging.2–4 Thus, brachial diastolic BP may overestimate aortic BP, particularly in young subjects. Although ISH is an important …