Complications of hypertension are related either to sustained elevations of blood pressure, with consequent changes in the vasculature and heart, or to atherosclerosis that accompanies and is accelerated by long-standing hypertension. Most of the adverse outcomes in hypertension are associated with thrombosis rather than bleeding, and there is evidence that increased vascular shear stress converts the normally anticoagulant endothelium to a prothrombotic state. The excess morbidity and mortality related to hypertension are progressive over the whole range of systolic and diastolic blood pressures; the risk approximately doubles for each 6 mm Hg increase in diastolic blood pressure. However, target-organ damage varies markedly between individuals with similar levels of office hypertension. Ambulatory pressures are superior to office readings in the prediction of end-organ damage.
A. HYPERTENSIVE CARDIOVASCULAR DISEASE
Cardiac complications are the major causes of morbidity and mortality in primary (essential) hypertension, and preventing them is a major goal of therapy. Electrocardiographic evidence of left ventricular hypertrophy is found in up to 15% of persons with chronic hypertension. For any level of blood pressure, its presence is associated with incremental cardiovascular risk. Echocardiographic left ventricular hypertrophy is a powerful predictor of prognosis. Left ventricular hypertrophy may cause or facilitate many cardiac complications of hypertension, including congestive heart failure, ventricular arrhythmias, myocardial ischemia, and sudden death.
Left ventricular diastolic dysfunction, which may present with all of the symptoms and signs of congestive heart failure, is common in patients with long-standing hypertension. The occurrence of heart failure is reduced by 50% with antihypertensive therapy. Hypertensive left ventricular hypertrophy regresses with therapy and is most closely related to the degree of systolic blood pressure reduction. Diuretics have produced equal or greater reductions of left ventricular mass when compared with other drug classes. β-Blockers are less effective in reducing left ventricular hypertrophy but play a specific role in patients with established coronary artery disease or impaired left ventricular function.
B. HYPERTENSIVE CEREBROVASCULAR DISEASE AND DEMENTIA
Hypertension is the major predisposing cause of hemorrhagic and ischemic stroke. Cerebrovascular complications are more closely correlated with systolic than diastolic blood pressure. The incidence of these complications is markedly reduced by antihypertensive therapy. Preceding hypertension is associated with a higher incidence of subsequent dementia of both vascular and Alzheimer types. Effective blood pressure control may modify the risk or rate of progression of cognitive dysfunction.
C. HYPERTENSIVE RENAL DISEASE
Chronic hypertension leads to nephrosclerosis, a common cause of renal insufficiency; aggressive blood pressure control attenuates the process. In patients with hypertensive nephropathy, the blood pressure should be 130/80 mm Hg or lower, especially when proteinuria is present. Secondary renal disease is more common in blacks, particularly when accompanied by diabetes mellitus. Hypertension also plays an important role in accelerating the progression of other forms of renal disease, most commonly diabetic nephropathy. ACE inhibitors are particularly effective in preventing the latter complication, but these agents also appear to prevent the progression of other forms of nephropathy.
D. AORTIC DISSECTION
Hypertension is a contributing factor in many patients with dissection of the aorta.
E. ATHEROSCLEROTIC COMPLICATIONS
Most Americans with hypertension die of complications of atherosclerosis, but the linkage between hypertension and atherosclerotic cardiovascular disease is not as clear as that with the previously discussed complications. Effective antihypertensive therapy is thus less successful in preventing complications of coronary heart disease.
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