Role of hypertension in coronary artery disease

Vascular factors in dementia: an overview

Alzheimer's disease and cerebrovascular disease are two illnesses common to the elderly. Conventional wisdom has sought to separately describe and treat these two diseases. Accumulating evidence, however, shows that cerebrovascular risk factors may cause asymptomatic brain injury, share genetic risk with Alzheimer's disease and possibly accelerate the Alzheimer's process. Such evidence suggests that these two diseases may act additively or synergistically to cause clinical dementia. This review focuses on evolving data that support this hypothesis.

The role of cerebrovascular disease in dementia

BACKGROUND

Improvements in health care over the last 50 years have lengthened average life expectancy significantly, resulting in considerable growth of the population over 65 years of age. With increased age, however, comes an increased risk for Alzheimer's disease (AD), and the prevalence of AD is predicted to reach epidemic proportions by the later half of the 21st century. The prevalence of cerebrovascular disease also increases with age, and recent evidence suggests that cerebrovascular risk factors such as hypertension and hypercholesterolemia also increase an individual's risk for AD, suggesting a potential interaction between these two very common disorders. The potential impact of cerebrovascular disease on general cognitive health is not yet well understood, but is now being actively explored and clarified.

REVIEW SUMMARY

Cerebrovascular disease may manifest itself in many ways, and this review begins by discussing the possible spectrum of brain injury associated with common cerebrovascular risk factors. The prominent role of brain imaging to detect clinically silent cerebrovascular disease is recognized and reviewed. The neuropsychological consequences of cerebrovascular disease across the cognitive spectrum is also reviewed, including potential mechanisms by which cerebrovascular disease may interact with AD to increase the expression or hasten the progression of dementia.

CONCLUSIONS

Cerebrovascular risk factors, common to the elderly, lead to pernicious brain injury and subtle cognitive impairment that most probably places the individual at greater lifetime risk for dementia. The cause of dementia among individuals with cerebrovascular disease, however, remains AD. Recognition of the potential role of cerebrovascular disease as an independent risk factor for AD offers the possibility of primary prevention through treatment of well-recognized risk factors and deserves further study. In the meantime, clinicians presented with an individual suffering from a slowly progressive dementia and findings of clinically silent cerebrovascular brain injury should recognize the potential role of cerebrovascular disease in the dementia process but not ignore the likely overwhelming effects of AD and treat appropriately.

Coronary artery blood flow: physiologic and pathophysiologic regulation

Acute myocardial ischemia, which results from a significant imbalance between myocardial oxygen demands and myocardial oxygen supply, occurs in as many as six million persons with atherosclerotic coronary artery disease in the United States. Accordingly, a clear understanding of the physiologic and pathophysiologic factors that influence coronary artery blood flow is important to the clinician and provides the basis for the judicious use of medications for the treatment of patients with atherosclerotic coronary artery disease. This review discusses the endothelial, metabolic, myogenic, and neurohumoral mechanisms of coronary blood flow regulation and the interaction of the different mechanisms in the regulation of coronary blood flow. The importance of nitric oxide in coronary blood flow regulation is emphasized. We also discuss the common clinical problems of hyperlipidemia and coronary atherosclerosis, coronary artery spasm, and systemic arterial hypertension that result in coronary artery endothelial dysfunction, the impaired production and increased inactivation of nitric oxide, and impairment in coronary blood flow regulation. This information is important to clinicians because more than forty million people in the United States have atherosclerotic or hypertensive heart disease and therefore are at risk for significant myocardial complications due to impairment of coronary blood flow regulation.

Hypertension and pathologic cardiovascular remodeling: a potential therapeutic role for T-type calcium antagonists

Increased myocardial mass (cardiac hypertrophy, left ventricular hypertrophy [LVH]) is an example of the widespread structural cardiovascular changes, often referred to as remodeling, that may be present in association with sustained high blood pressure. LVH strongly predicts myocardial infarction, stroke, and cardiovascular death in patients with hypertension. As a result, prevention or reversal of hypertensive LVH is widely accepted as a desirable therapeutic goal. Although the molecular mechanisms responsible for remodeling are unclear, it is believed that mechanical, endocrine, paracrine, and autocrine factors control the remodeling process. Certain antihypertensive drugs may have particularly favorable long-term effects in that they prevent and correct these structural changes in addition to reducing arterial pressure. However, the mechanism by which they achieve these effects is not well understood. It is theorized that angiotensin-converting enzyme inhibitors do so by preventing the generation of growth-promoting/mitogenic peptides and that beta-blockers interfere with the growth-promoting effects of catecholamines. In experimental models, the selective blockade of T-type calcium-ion (Ca2+) channels with mibefradil has been demonstrated to have antiproliferative effects in both the renal and cardiac vasculature; in patients with LVH, mibefradil reduced the left ventricular mass index. Therefore, blockade of T-type Ca2+ channels may be useful in the prevention or regression of cardiovascular remodeling. However, further research will be required before the clinical implications of these findings can be assessed.