Directional coronary atherectomy: how much lumen enlargement is optimal?

Until recently, it has not been clear how much of the effect of directional coronary atherectomy is due to tissue removal per se, and whether the long-term results of the procedure are helped or harmed when the operator attempts to obtain the "near zero percent" residual stenosis of which this technique is capable. This article summarizes the findings of a series of studies that have addressed these important questions and proposes a prescription for the optimal performance of directional atherectomy. Analysis of retrieved tissue weights compared with measured increases in luminal volume shows that about half of the improvement seen after directional atherectomy results from mechanical dilation. Because this "facilitated" dilation appears to take place within the bases of the trenches created by atherectomy cuts (rather than being randomly distributed in fractures throughout the plaque substance), a larger and smoother lumen is possible compared with that seen after conventional balloon dilation. Although the recovery of deep vessel wall components (media and even adventitia) is common, it generally does not cause either acute complications (i.e., perforation) or increase the probability of subsequent restenosis. Rather, reduction in the probability of late restenosis appears to be most directly related to the ability of directional atherectomy to provide the largest acute luminal diameter safely possible, thus providing better tolerance of subsequent intimal hyperplasia before hemodynamically significant renarrowing results at the treatment site.