Coronary Atherectomy: A Revisit with a New Tool — Single-Blade Cutting Balloon

The first percutaneous transluminal coronary angioplasty (PTCA) in humans was performed by Dr. Andreas Gruentzig in 1974.¹ Since then, major evolutions in PTCA have resulted in over 1,000 angioplasty procedures in the registry by 1980. The next decade saw the rapid development of over-the-wire balloons, brachial guiding catheters, steerable guidewires and coronary atherectomy.² From 1986 to 1993, several new inventions and perfections of innovative devices in the field of interventional cardiology occurred. Devices were developed to attempt to reduce the plaque burden of atheromatous lesions and improve arterial remodeling. Tehnologies involving hot and cool laser ablation of plaque were thought to be a promising, however they did not perform as expected. Rotational atherectomy devices (Rotablator®, Boston Scientific Corp., Natick, Massachusetts)³ and intravascular ultrasound (IVUS)⁴ found their unique use in calcified arteries and the evaluation of the arterial lumen, respectively. The turning point of interventional cardiology was the introduction of coronary stents and their final U.S. Food and Drug Administration (FDA) approval in 1995. Despite several advances, the Achilles heel of angioplasty and stenting continued to be in-stent restenosis. In-stent restenosis causes angina and an increase in target vessel revascularization (TVR). The early 1990s brought several niche devices into play as an adjunct to balloon angioplasty. The Balloon versus Optimal Atherectomy Trial (BOAT)⁶ study compared optimal atherectomy versus PTCA. At 6 months, the restenosis rate was lower in the atherectomy group (32% vs. 40% in PTCA). A higher incidence of cardiac enzymes was noted in the atherectomy group, and no difference in mortality or TVR. The benefits of better acute outcomes and reduced restenosis were not reproduced. A meta-analysis of 16 trials compared various atherectomy devices^7,8 to conventional balloon angioplasty. This meta-analysis of 9,222 patients showed no mortality benefit, increased myocardial ischemia and major adverse cardiac events at 30 days. Furthermore, the rate of restenosis and TVR was not reduced. A unique modification of the standard PTCA balloon is the cutting balloon. It differs from a standard balloon in the additional three or four blades placed on its outer surface. The longitudinal atherotome blades assist balloon angioplasty by delivering precise and longitudinal incisions into the atherosclerotic plaque.⁹ Such a controlled dissection was thought to decrease the forces needed to dilate a coronary lesion. A cutting balloon dilatation should reduce the elastic recoil and provide a better luminal expansion. These unique features were applied in areas of fibrotic lesions such as ostial, small vessel segments and restenosis. Initial results of the small, randomized clinical trial showed promising results.¹⁰ However, this was not consistent in the RESCUT11 trial, which compared PTCA versus cutting balloon for 428 patients with in-stent restenosis. The restenosis rate was similar (30% vs. 31% for PTCA), and major adverse events were 16% vs. 15% for PTCA. A paradigm shift occurred in interventional cardiology with the introduction of drug-eluting stents. Dr. Eduardo Sousa and colleagues implanted the first human coronary drug-eluting stent in 1999.¹² Subsequently in 2003 and 2004, sirolimus- and tacrolimus-eluting stents were approved by the FDA. The restenosis rates were noted to be in the single digits and TVR rates were reduced. Despite several decades of advances in PTCA, the Achilles heel of angioplasty and stenting continued to be in-stent restenosis, calcified and fibrotic lesions. The pivotal study by Kinoshita et al using a single-blade cutting balloon (SCB) for directional coronary atherotomy is a novel alternative to conventional PTCA. The unique design of a single atherotome can minimize the risk of perforation, yet provides precise and controlled dissection of the plaque. Ostial and bifurcation lesions contain an abundance of fibrotic tissue and pose a challenge to the interventional operator. The use of a SCB in such lesions as the primary therapy or an adjunct to stenting may be beneficial. Increasing the luminal diameter of a coronary lesion can theoretically help achieve optimal stent expansion in a fibrotic plaque. Adequate stent expansion and apposition to the intima can reduce the incidence of acute stent thrombosis and restenosis. The initial animal study is primitive yet, as it is performed on porcine coronaries with experimentally-induced lesions. Coronary lesions in humans differ in their fibrous content, smooth muscle cells, calcification and eccentricity of the lesions. There is no definitive advantage with the many previous atherectomy devices to reduce restenosis, mortality or TVR. The issue of restenosis in the era of drug-eluting stents is minimal and can be effectively reduced by the use of IVUS in high-risk patients. The Study to evaluate DES deployment Technique on cLinicaL Results (STLLR) is designed to address the important issue of identifying the optimal deployment technique.¹³ SCB, if feasible in humans, may play a vital role in ostial lesions, small vessel disease and coronary lesions in patients who cannot take antiplatelet therapy and where stent placement is not an option. This technology should also be tested in a randomized clinical trial of SCB versus conventional balloon angioplasty with optional stenting in both groups.

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