Coronary Artery Disease

Coronary Artery Disease, or CAD, is defined as the hardening, or artherosclerosis, of the coronary arteries due to the gradual deposition of lipid and cholesterol plaques on the inner layer, or intima of the arteries. It is estimated that approximately 14 million Americans have CAD, and of them 1.5 million per year develop the most serious complication of this disease, myocardial infarction. The estimated annual cost of CAD in the United States is over $350 billion dollars. [1] CAD is by far the single largest killer of men and women in the United States ; one in every five Americans will die from CAD, and it kills more people annually than the five other leading causes of death combined. Treatment of CAD is complex and often involves invasive or noninvasive coronary interventions and life style modification. The newest and perhaps most promising of these minimally invasive interventions, drug eluting stents, is the topic of this web page and will be explored in some depth in subsequent sections.

A Brief History of Percutaneous Coronary Interventions and the Development of Drug Eluting Stents

With the advent of cardiac catheterization in late 1920s and the development of angiographic technology in the late 1950s, the stage was set for noninvasive or percutaneous treatment of coronary artery disease. New techniques were first applied to the revascularization of the femoral, renal, and carotid arteries in the mid 1960s, and were later adapted to the coronary arteries in the late 1970s. Though the practice of using balloon catheters to mechanically disrupt plaques in the coronary arteries proved quite successful in the short term, the long term prognosis was less promising due to restenosis. This prompted the development of new techniques to remove plaques and the use of mechanical adjuncts, or stents, in order to maintain lumen patency following angioplasty. Though effective at removing plaques, the atherectomy techniques that were developed still had serious side effects such as thrombosis and infarction, and the procedure was largely abandoned in favor of angioplasty with stents in order to maintain arterial patency. Stenting became quite prevalent in Europe in the 1980s and was increasingly used as the first line of percutaneous coronary intervention in the treatment of CAD. Methods to reduce or eliminate the side effects of stenting were developed in the 1990s including administration of anticoagulants, intravascular ultrasound, and application of radioactive pellets to inhibit cell growth in the endothelium surrounding the stent. Systemic anticoagulation proved very effective and greatly reduced thrombus associated complications. The insertion of radioactive pellets or coils, called brachytherapy, was also effective at preventing in stent restenosis but its unfavorable side effects, such as inhibition of healing around the stent and increased risk of cancer, made it unsuitable for widespread use. The shortcomings of brachytherapy prompted further development of technology to maintain long term arterial patency. This led to the emergence of stents designed to locally deliver drugs in order to inhibit neointimal hyperplasia without the serious effects of radiation or systemic drug administration. These coated, or drug eluting, stents used various drugs encapsulated in different polymeric and non-polymeric formulations. Drug eluting stents were found to greatly reduce restenosis and, in the short term, have been found to maintain arterial patency better than surgical interventions such as bypass grafts. This, combined with a lower incidence of side effects and a lower cost, makes drug eluting stents a viable option for treatment of CAD. Though their track record is, at this point, quite impressive, the long term efficacy and implications of drug eluting stents remains to be seen. [2]

For an excellent depiction of atherectomy click here. Select "Surgery" then "Directional coronary artherectomy (DCA)" from the list of animations, and click "Launch Animation."