The mechanism by which percutaneous devices enlarge obstructed coronary arteries can be classified using two basic categories: dilating devices and tissue removal (atherectomy) devices. Dilating devices expand coronary arteries, displacing the obstructing plaque or thrombus radially to create an expanded arterial lumen diameter. These devices generally use balloon dilation to provide the force for radial displacement. Examples include conventional angioplasty balloons, heated balloons, cutting balloons, and balloon-expandable stents. Atherectomy devices work by removing the obstructing plaque or thrombus, thus expanding the arterial lumen diameter by "debulking" the lesion. Although the predominant mechanism of action with these devices is debulking the lesion, they also dilate the lesion via "Dottering" (i.e., lumen dilation that accompanies the insertion of a rigid body). Atherectomy devices may be further divided into ablative lasers, which remove plaque via tissue vaporization, and the mechanical atherectomy devices. Directional coronary atherectomy and transluminal extraction catheters are examples of devices that collect plaque into an isolated chamber that can be removed from the body. Rotational atherectomy, on the other hand, ablates plaque into debris smaller than red blood corpuscles (2-5 im in diameter), which ultimately passes through the coronary microcirculation and then is cleared by the reticuloen-dothelial system.
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