Inside The Exam Room™ 11/28/2006
ANGIOPLASTY Part 2
By Mark Ombrellaro, MD
Results with angioplasty appear to be quite good, tending to be intermediate between medical therapy alone and bypass. Durability depends upon a number of variables which include the diameter of the treated vessel, the length of the arterial obstruction, whether or not one is treating a narrowing versus a complete obstruction, calcium content of the lesion, or plaque distribution involving the entire circumference of the artery wall. In general, dilating larger diameter vessels (rather than small), shorter focal lesions (rather than long ones), and narrowed vessels (rather than occluded ones) tend to have better results. As with any medical procedure, complications can occur with angioplasty but the overall incidence is quite low. Complications can include rupture of the artery, arterial dissection, embolization, thrombosis, or incomplete opening of the treated artery. Rupture of the artery typically occurs if it becomes too overstretched so it is important to match balloon size with the true size of the artery in its non-diseased state. This will allow for dilation to the proper arterial diameter while best balancing restoration of the flow channel against the potential for vessel rupture. Even in circumstances where the balloon and artery are properly size matched, plaque containing significant amounts of calcium can tear and poke through the arterial wall and lead to arterial rupture. A dissection is an extensive tear within the artery. The idea of angioplasty is to achieve a controlled linear tear (which is considered stable) without extensively damaging or undercutting the inside lining of the vessel wall, or creating loose debris or a flap. A flap is an unstable segment of the inner arterial lining which can produce a mechanical obstruction of blood flow and clot formation. Embolization is a condition where fragments of the plaque flake off into the blood stream after being manipulated by the angioplasty procedure. Once in the blood stream they are carried off until they lodge in a smaller vessel and obstruct blood flow. Plaques with a high concentration of calcium and those that involve the entire circumference of the arterial wall are less likely to be successfully treated with angioplasty. Under these circumstances, it is more likely that there will be some residual narrowing despite adequate balloon inflation.
Angioplasty balloons are available in a wide variety of lengths and diameters in order to treat arterial obstructions in all types of vascular bed. While most people are aware of angioplasty for the heart, these same techniques can be applied to any other artery in the body. There is also a new technique called cryoplasty which uses a specialized angioplasty balloon and inflation system that cools the artery wall down to -10 degrees C while the balloon is in contact with the artery wall and dilating the abnormal segment. This cooling procedure is thought to slow down the natural healing process within the artery and decrease the amount of scar that forms after angioplasty.
The major limitation with angioplasty is considered restenosis, or the scar formation that occurs within the artery as part of the natural healing process, that ultimately leads to recurrent narrowing of the treated segment. The body’s response to injury is limited and typically consists of fibrous tissue formation and thickening which we refer to as fibrointimal hyperplasia. Angioplasty, being a controlled arterial tear, is actually seen by the body as an injury which it has to heal. Fibrous tissue builds up both in the injured area itself, the medial tissue, as well as along the residual plaque. The scar formation response varies between individuals and as different people will scar differently on the outside, the same applies for the healing response to injury that occurs inside the body.