The Renaissance of Directional Coronary Atherectomy
The concept of transcatheter atherectomy -- removing obstructive tissue by a catheter-based excision technique -- was first introduced by Simpson to overcome several unsolved limitations of the conventional "forced-dilation or plaque-displacement" approach by balloon angioplasty (PTCA). The first directional atherectomy of human vessels was performed in a superficial femoral artery in 1985, with an initial experience in human coronary arteries following the next year. The safety of the peripheral and coronary devices was confirmed by subsequent large multicenter experience; the peripheral device was approved by the Food and Drug Administration (FDA) in 1987 and the coronary device in 1990. Despite the initial enthusiasm for this first non-balloon percutaneous coronary interventional device, the early randomized clinical trials of directional coronary atherectomy (DCA) in 1993, CAVEAT (Coronary Angioplasty Versus Excisional Atherectomy Trial) and CCAT (Canadian Coronary Atherectomy Trial), failed to demonstrate a clinically significant reduction in late angiographic or clinical restenosis after DCA versus PTCA. These negative findings for DCA, combined with the approval of the Palmaz-Schatz coronary stent (Cordis Corporation, Miami Lakes, Florida) in 1994, resulted in a rapid decrease in the usage of this unique technology.
However, questions remained about whether the potential benefits of DCA might have been underestimated because of the way in which DCA was performed in these early trials. Initial concern over deep vessel wall injury, which might cause unfavorable acute or long-term outcomes, biased the technique toward limited acute gain with relatively small cutter sizes as well as avoidance of post-dilation by adjunctive PTCA. Accordingly, quantitative coronary angiography (QCA) demonstrated large residual stenosis with only a small advantage for DCA: the final diameter stenoses were 29% versus 36% in CAVEAT, and 25% versus 33% in CCAT for DCA versus PTCA, respectively. Although few centers in the two trials used intravascular ultrasound (IVUS), contemporary IVUS studies suggested that with this degree of angiographic result, more than 60-70% of the vessel area was presumably occupied by residual plaque. Over the following several years, it had been shown that late lumen diameter and the probability of restenosis after interventions are influenced strongly by the lumen diameter immediately after the procedure, rather than by the specific device used. In addition, several IVUS trials, including Phase II of GUIDE (Guidance by Ultrasound Imaging for Decision Endpoints), suggested that the residual plaque burden (plaque area/vessel area at the lesion site) assessed by IVUS was a significant predictor of restenosis following non-stent coronary interventions. These concepts led to a great emphasis on aggressive plaque removal and on the use of adjunctive PTCA to achieve "optimal" atherectomy results.
The concept of transcatheter atherectomy -- removing obstructive tissue by a catheter-based excision technique -- was first introduced by Simpson to overcome several unsolved limitations of the conventional "forced-dilation or plaque-displacement" approach by balloon angioplasty (PTCA). The first directional atherectomy of human vessels was performed in a superficial femoral artery in 1985, with an initial experience in human coronary arteries following the next year. The safety of the peripheral and coronary devices was confirmed by subsequent large multicenter experience; the peripheral device was approved by the Food and Drug Administration (FDA) in 1987 and the coronary device in 1990. Despite the initial enthusiasm for this first non-balloon percutaneous coronary interventional device, the early randomized clinical trials of directional coronary atherectomy (DCA) in 1993, CAVEAT (Coronary Angioplasty Versus Excisional Atherectomy Trial) and CCAT (Canadian Coronary Atherectomy Trial), failed to demonstrate a clinically significant reduction in late angiographic or clinical restenosis after DCA versus PTCA. These negative findings for DCA, combined with the approval of the Palmaz-Schatz coronary stent (Cordis Corporation, Miami Lakes, Florida) in 1994, resulted in a rapid decrease in the usage of this unique technology.
However, questions remained about whether the potential benefits of DCA might have been underestimated because of the way in which DCA was performed in these early trials. Initial concern over deep vessel wall injury, which might cause unfavorable acute or long-term outcomes, biased the technique toward limited acute gain with relatively small cutter sizes as well as avoidance of post-dilation by adjunctive PTCA. Accordingly, quantitative coronary angiography (QCA) demonstrated large residual stenosis with only a small advantage for DCA: the final diameter stenoses were 29% versus 36% in CAVEAT, and 25% versus 33% in CCAT for DCA versus PTCA, respectively. Although few centers in the two trials used intravascular ultrasound (IVUS), contemporary IVUS studies suggested that with this degree of angiographic result, more than 60-70% of the vessel area was presumably occupied by residual plaque. Over the following several years, it had been shown that late lumen diameter and the probability of restenosis after interventions are influenced strongly by the lumen diameter immediately after the procedure, rather than by the specific device used. In addition, several IVUS trials, including Phase II of GUIDE (Guidance by Ultrasound Imaging for Decision Endpoints), suggested that the residual plaque burden (plaque area/vessel area at the lesion site) assessed by IVUS was a significant predictor of restenosis following non-stent coronary interventions. These concepts led to a great emphasis on aggressive plaque removal and on the use of adjunctive PTCA to achieve "optimal" atherectomy results.