The original explanation given by Andreas Gruentzig for enlargement of a vessel lumen by PTCA was compression of plaque, but we now know that this is a minor effect. Also contributing minimally is extrusion of some liquid components from a soft plaque. More important, however, is that PTCA leads to cracking of the intimal plaque with resultant stretching of media and adventitia and expansion of the outer diameter of the vessel. This is apparent on postmortem histologic examination of these vessels.
How is PTCA performed when disease occurs at points of bifurcation?
When both branches of a bifurcation of a coronary artery are diseased, angioplasty of one lesion may cause shifting of plaque to the other lesion, resulting in worsening stenosis or occlusion. Thus, to avoid this problem, the operator uses two steerable guidewires simultaneously. The wires are positioned down each limb of the bifurcation and then dilated one at a time. In some instances, two balloons are used and inflated simultaneously. This prevents shifting of plaque from one
branch to the other and is known as the kissing balloon technique.‚
Describe the patient risk factors for restenosis following angioplasty.
The restenosis rates are fairly similar for men and women, but slightly higher for men. Other traditional risk factors for atherogenesis seem to be operative after angioplasty as well. Diabetes promotes restenosis, as demonstrated in various studies. Hypertension, however, has not been proved sufficiently to cause restenosis. Continued smoking following PTCA is clearly a major risk factor due to its vasoconstricting effects and platelet-stimulating properties. Variable results have been reported regarding hypercholesterolemia and restenosis, but it does not seem to be a major risk factor. Unstable angina at the time of PTCA is an independent risk factor for restenosis when compared to those with stable symptoms.
Name some of the minor complications associated with angioplasty.
Embolization of plaque constituents, thrombi, calcium, and others (fortunately rare)
Ventricular fibrillation (usually due to ischemia)
Loss of branch vessels during PTCA of a main vessel
Hypotension from bleeding, tamponade, medications, hypovolemia
Femoral artery complications, including hematoma, pseudoaneurysms, arteriovenous fistulas, etc.
Coronary artery aneurysm at the site of PTCA (rare)
Describe the newer interventional devices that can overcome some of the problems of conventional PTCA.
When conventional PTCA results in abrupt closure or restenosis or suboptimal results, newer interventional techniques may be preferred:
Intravascular stents are endovascular splints‚ used to maintain vascular patency. Different types of stents have been used, but now the balloon expandable ones are preferred. They are useful for reversal of abrupt closure when due to dissection. Its most important complication is thrombosis, which is prevented by a vigorous antithrombotic regimen.
Directional coronary atherectomy (DCA) enlarges the coronary lumen by actually removing plaque by high-speed rotation. It is useful in cases of restenosis, vein graft disease, ulcerated plaque, eccentric lesions, or ostial lesions.
Laser balloon angioplasty applies both heat and pressure to the arterial wall in an attempt to dilate the lumen. This combination may result in desiccation of thrombus and decreased elastic recoil. Although still in its early stages, there is a high restenosis rate with this technique.