Metabolic Syndrome and Cardiovascular Disease

Metabolic Syndrome and Cardiovascular Disease is a comprehensive text addressing the cardiovascular risk factors and consequences associated with this important condition, a concept that has evolved over much of the past century, but which has received renewed and heightened attention over the past decade. It has been known for several decades that risk factors for atherosclerotic cardiovascular disease often cluster together. This knowledge is the basis for multifactorial algorithms to predict risk for cardiovascular disease. The Framingham Heart Study produced the first risk-prediction algorithms, but more recently, similar risk engines have been created from other databases of prospective studies. These risk-prediction tools have included all of the established atherosclerotic cardiovascular disease risk factors and provide the basis for estimates of global risk.

Only recently have efforts been made to identify particular patterns of risk factors that have a common origin. The metabolic syndrome is one such pattern that has generated much interest in recent years.

Two lines of evidence have merged to produce the metabolic syndrome concept. These different origins have not been fully integrated and account for much of the debate that surrounds the syndrome. The first of these has been the recognition that obesity is strongly associated with multiple risk factors and undoubtedly contributes significantly to them. These include hypertension, hyper-cholesterolemia, hypertriglyceridemia, low levels of high-density lipoproteins, and hyperglycemia. In spite of much research on these metabolic complications of obesity, researchers in this field never consolidated all of them into a syndrome.

But certainly it was recognized that prevention and treatment of obesity is the foundation of management of these risk factors.

During this same period, researchers in the diabetes field identified a metabolic state called insulin resistance. It was characterized by resistance to the actions of insulin and hyperinsulinemia. Insulin resistance was first recognized as a major contributing factor to Type 2 diabetes. However, in 1998, Dr. Gerald Reaven presented the hypothesis that insulin resistance also can be a cause of risk factors of metabolic origin. Among these risk factors he first identified were hypertension, low high-density lipoproteins levels, and hypertriglyceridemia.

Although Dr. Reaven called the clustering of risk factors with insulin resistance and hyperinsulinemia tighten by the name syndrome X, others shortly thereafter changed the name to insulin resistance syndrome. Several different names have been used as alternatives for the metabolic syndrome. Besides metabolic syndrome X, and insulin resistance syndrome, there are the dysmetabolic syndrome, metabolic syndrome X, the deadly quartet, CHAOS, and the cardiometabolic syndrome. Often the name chosen is meant to highlight one or another feature of the syndrome. Recently some investigators have raised the question of whether a clustering of metabolic risk factors should be called a "syndrome" at all. This is a semantic issue, but most researchers believe that the term "syndrome" is appropriate for a clustering of risk factors of metabolic origin. For another decade, the metabolic syndrome/insulin resistance syndrome remained a topic of research interest, but did not become an entity for clinical identification. But in 1998, the World Health Organization Working Group on Definition of Diabetes attempted to formulate criteria for the diagnosis of the metabolic syndrome.