Simonton CA Leon MB Baim DS et al Reference

Circulation 1998; 97: 332-339 Abstract

BACKGROUND: Previous clinical trials of directional coronary atherectomy (DCA) have failed to show significant improvement in early or late outcomes compared with balloon angioplasty (PTCA). The present study tested the hypothesis that more aggressive "optimal" atherectomy could be performed safely to produce larger initial lumen diameters and a lower late restenosis rate. METHODS AND RESULTS: The present study was a prospective multicenter registry of consecutive patients undergoing optimal DCA of de novo or restenotic lesions in 3.0- to 4.5-mm native coronary arteries. Optimal DCA was defined as using a 7F atherectomy device and adjunctive PTCA if necessary to achieve a <15% residual stenosis. Six-month angiographic and 1-year clinical follow-up was planned in all patients. A total of 199 patients with 213 lesions met eligibility criteria for enrollment. Short-term procedural success was achieved in 97.5%, with a major complication rate (death, emergency bypass surgery, or Q-wave myocardial infarction [MI]) of 2.5%. There were no early deaths. Non-Q-wave MI (CK-MB >3 times normal) occurred in 14% of patients. Mean reference vessel diameter was 3.28 mm. Mean diameter stenosis was reduced from 63.5% to a final stenosis of 7%. Late 1-year clinical follow-up revealed one cardiac death and a target lesion revascularization rate of 17.8%. The angiographic restenosis rate at 6 months was 28.9%, with the major predictor of restenosis being a smaller postprocedure lumen diameter. CONCLUSIONS: Optimal DCA produced a low residual % diameter stenosis and a lower restenosis rate than seen in previous trials without an increase in early or late major adverse events.

Summary

The OARS (Optimal Atherectomy Restenosis Study) trial followed two large randomized trials (Coronary Angioplasty vs. Excisional Atherectomy Trial and Canadian Coronary Atherectomy [CAVEAT and CCAT]) that examined the efficacy of directional coronary atherectomy (DCA) as a method of treating obstructive atherosclerotic coronary disease versus standard balloon angioplasty. Both trials failed to show a significant benefit to using DCA. Moreover, there was a belief that these trials were conducted too early in the development of the DCA technique, which is to say that the operator's experience was early on the learning curve. Another thought was that "optimal" atherectomy had not been performed. The OARS trial tested the "bigger is better" approach to atherectomy. The hypothesis was that more aggressive DCA would lead to a larger early lumen diameter; and subsequently, better late clinical and angiographical restenosis rates. The study involved 200 consecutive patients at four centres who underwent more aggressive atherectomy and who were followed at 6 months (angiography) and 12 months (clinical). The primary end-points were 6-month angiographical restenosis (>50%) and 12 month target vessel failure rate (myocardial infarction (MI), target vessel revascularization (TVR), or death).

MLD (mm)

Diameter stenosis (%)

Figure 1 Baseline and acute angiographic results. (a) Cumulative distribution of reference vessel diameter and minimal luminal diameter (MLD) at baseline (preprocedure) and after final treatment (postprocedure). (b) Cumulative distribution of % diameter stenosis at baseline (preprocedure) and after final treatment (postprocedure).

Diameter stenosis (%)

Figure 1 Baseline and acute angiographic results. (a) Cumulative distribution of reference vessel diameter and minimal luminal diameter (MLD) at baseline (preprocedure) and after final treatment (postprocedure). (b) Cumulative distribution of % diameter stenosis at baseline (preprocedure) and after final treatment (postprocedure).

The results for angiographical restenosis, death, MI, TVR and target vessel failure were 29%, 1%, 1.5%, 21% and 24%, respectively. A large initial lumen diameter was achieved with an average size of 3.16 mm (in vessels with reference diameters of 3.0-4.5 mm). The authors concluded that "optimal" DCA could be performed safely and would result in larger initial lumen diameters (Figure 1).

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Strengths

The trial was conducted at experienced centres capable of performing more aggressive DCA. The follow-up included angiographical and clinical end points.

Weaknesses

The trial was not randomized and 87% of patients underwent post-DCA percutaneous transluminal coronary angioplasty (PTCA); therefore, in most cases the result was not 100% attributable to DCA. There was a high incidence of periprocedural CK-MB elevation although this did not manifest in poorer clinical outcomes.

Relevance

The overall benefit of DCA shown in this study is modest at best. Using a more aggressive DCA strategy did lead to a larger early lumen; however, this was at a cost of higher CK-MB levels and without a large clinical benefit. The OARS trial did collect early registry results of safety and efficacy, but did not improve greatly on the shortcomings of CAVEAT and CCAT, which were larger studies. Compared to PTCA, the restenosis rate of 29% achieved in this study compares favourably; however, it falls short of newer era bare metal stents and is clearly inferior to drug-eluting stents in terms of angiographical restenosis rates.

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