Contemporary technologies to modify calcified plaque in coronary artery disease

doi:10.1016/j.pcad.2021.07.003

Progress in Cardiovascular Diseases

Volume 69, November–December 2021, Pages 18-26

https://doi.org/10.1016/j.pcad.2021.07.003 Get rights and content

Abstract

With aging society, one of the more challenging obstacles in percutaneous coronary interventions are calcified coronary lesions. Calcified lesions may impede stent delivery, limit balloon and stent expansion, cause uneven drug distribution, and hinder wire advancement. Even in the setting of acceptable procedural success, vessel calcification is independently associated with increased target lesion revascularization rates at follow-up and lower survival rates. In order to effectively manage such lesions, dedicated technologies have been developed. Atherectomy aims at excising tissue and debulking plaques, as well as compressing and reshaping the atheroma, generally referred to as lesion preparation that enables further balloon and/or stent expansion in contemporary clinical practice. In the current review, we will discuss the available methods for atherectomy, including rotational, orbital, and excimer laser coronary atherectomy, as well as intravascular lithotripsy. In addition, we will review the role of imaging in calcified lesions.

Introduction

Since the initial development of percutaneous coronary intervention (PCI), progress in technology and evolved techniques enabled successful interventions in increasingly complex lesions and patient populations. With aging society, one of the more challenging obstacles are calcified coronary lesions. Despite culmination of knowledge and innovative devices, calcified lesions continue to pose a major challenge in PCI. Calcified lesions may impede stent delivery,¹ limit balloon¹ and stent expansion² which result in lower minimal stent area (MSA), cause uneven drug distribution,³^,⁴ and even hinder wire advancement. Lower MSA and stent under-expansion are associated with adverse outcomes, including target lesion and stent failure.⁵^,⁶ Vessel calcification, even when associated with acceptable procedural success, is independently associated with increased target lesion revascularization (TLR) rates at follow-up⁷^,⁸ and lower survival rates.⁸^,⁹ In order to effectively manage such lesions, dedicated technologies have been developed. In the current review, we will discuss the available methods for atherectomy and the role of imaging in calcified lesions.

Section snippets

Currently available technologies to modify calcified plaque

Atherectomy, originally developed in the 1980s, aims at excising tissue and debulking plaques, as well as compressing and reshaping the atheroma, generally referred to as lesion preparation that enables further balloon and/or stent expansion in contemporary clinical practice. Existing technologies for atherectomy include rotational atherectomy,10, 11, 12 orbital atherectomy,¹³^,¹⁴ excimer laser coronary atherectomy (ELCA),15, 16, 17 and directional atherectomy. A directional atherectomy device

Rotational atherectomy

The commercially available rotational atherectomy device is ROTAPRO or Rotablator (Boston Scientific) – a diamond-tipped brass burr rotating concentrically at 130,000–180,000 rounds per minute (rpm), driven by the energy of compressed gas. Atherectomy is achieved by mechanisms referred to as differential cutting and orthogonal displacement of friction. Differential cutting means that the high-speed ablation distinguishes plaque from the healthy vessel wall. The immobile and firm plaque remains

Orbital atherectomy

Orbital atherectomy is a method for reducing plaque burden with a mechanism aimed at minimizing vessel wall trauma. The commercially available device – Diamondback 360° Coronary Orbital Atherectomy System resembles rotational atherectomy in its ablative crown (equivalent to the burr) which is diamond coated and rotates in 80,000 and 120,000 rpm. It is shaped as an eccentric hump that orbits around the wire. In contrast to rotational atherectomy, the diameter of ablation increases with higher

Rotational versus orbital atherectomy outcomes

There is no prospective randomized study directly comparing rotational versus orbital atherectomy devices. In a propensity score matched cohort of overall 546 patients who underwent rotational versus orbital atherectomy, myocardial infarction occurred more often in the rotational atherectomy group, albeit overall safety outcomes did not differ between the groups.⁴¹ Of note, with orbital atherectomy, the initial lesion diameter was larger (lesion length was similar), perhaps due to sideway

Laser atherectomy

Laser atherectomy is another viable option for atherectomy. Excimer laser coronary atherectomy (ELCA) uses a xenon-chloride monochromatic compound. The optical fibers-containing coronary catheter carries 308 nm length (ultraviolet light spectrum) beams from the laser system that penetrate to a depth of 10–50 μm into the tissue. The laser beams are transmitted at a pulse frequency of 25–80 Hz and generate a fluence rate (the radiant power) of 30–80 mJ/mm. ELCA modifies plaque by 3 mechanisms

Intravascular lithotripsy

Although not an atherectomy device by definition, Shockwave Intravascular Lithotripsy (IVL) should be mentioned as it became available for the treatment of calcified coronary lesions initially in Europe and is now approved by the FDA in the United States. The concept of lithotripsy has been used to pulverize kidney stones using extracorporeal shockwaves without injuring healthy organs. In coronary lithotripsy, lesion modification is achieved by pulsatile mechanical energy delivered to calcified

Imaging of calcified plaque

Angiographically, calcium appears as areas of x-ray attenuation delineating the arterial course, especially before contrast injection. Moderate calcifications are defined as radiopacities noted during the cardiac cycle and severe calcifications are defined as radiopacities noticed without cardiac motion, involving both sides of the vessel wall.⁶² A recent study investigated the detection of calcium by angiography, intravascular ultrasound (IVUS), and optical coherence tomography (OCT) in 440

Practical approach for selecting devices to calcified plaque modification

Fig. 3 presents a suggested practical approach for selecting devices to modify calcified plaque. After a calcified plaque is identified by angiography, the lesion should be assessed with intracoronary imaging. If the intracoronary imaging device cannot cross, upfront rotational or orbital atherectomy needs to be considered. When assessing with intracoronary imaging, we need to identify the extent of calcium such as arc, thickness, and longitudinal length of calcium. As discussed above,

Conclusions

With aging population, interventional cardiologists encounter calcified coronary lesions more often and the importance of calcified plaque modification is increasing. Adequate calcified plaque modification is crucial to achieving adequate stent expansion, which can serve as a nidus for restenosis. Adjunctive intracoronary imaging devices are essential to properly identify the severity of calcium and select an appropriate device for lesion modification to achieve optimal results, especially in

Funding sources

None.

Disclosures

Dr. Latib has served on Advisory Boards for Medtronic, Boston Scientific, Philips, Canon, CorFlow and Abbott. Dr. Kobayashi has served as a consultant to ACIST Medical Systems Inc. and Abbott Vascular Inc. Dr. Bliagos has served on Advisory Boards for Boston Scientific. Dr. Rozenbaum and Dr. Takahashi have nothing to disclose.