Intravascular Lithotripsy


Continuing Education Activity

Shockwave intravascular lithotripsy is a novel device that modifies calcified lesions via calcium fracture to allow for effective stent deployment. This activity describes the procedure and reviews the role of the healthcare team in treating patients who undergo this procedure.

Objectives:

  • Describe the pathophysiology of coronary artery calcification.
  • Identify the indications for shockwave intravascular lithotripsy.
  • Review the technique for shockwave intravascular lithotripsy.
  • Summarize the risks associated with shockwave intravascular lithotripsy.

Introduction

Coronary artery calcification (CAC) is an independent predictor for major cardiovascular events.[1][2][3][4] Additionally, coronary calcium deposition can hinder successful percutaneous coronary intervention (PCI) as a result of inadequate stent expansion, difficulty transiting the catheter through a calcified lesion, coated drug separation from a stent, proclivity for in-stent restenosis and stent thrombosis, and a change to the underlying pharmacokinetics. Consequently, PCI of calcified lesions correlates with worse outcomes.[5] 

Shockwave intravascular lithotripsy (IVL) is a novel technique evolved from the established therapy for renal and ureteral calculi that utilizes a percutaneous device to produce acoustic pressure waves resulting in the delivery of energy to break superficial and deep calcium deposits and aid with the subsequent deployment of a vascular stent.[6][7][8] Guidance with an intravascular imaging device either with intravascular ultrasound or optical coherence tomography is crucial in defining the calcium density and choosing the optimal lesion modification strategy, i.e., rotational atherectomy, orbital atherectomy or IVL.[9][10][11][12][13]

The feasibility and safety of IVL in the peripheral vasculature was shown in the Disrupt Peripheral Arterial Disease (PAD) studies and the Disrupt Below the Knee (BTK) study.[14][15][16] The Disrupt PAD III study (ClinicalTrials.gov Identifier: NCT02923193) is currently an ongoing prospective multicenter single-arm observational study assessing treatment of moderate and severely calcified femoropopliteal arteries. The disrupt Coronary Artery Disease studies I and II demonstrated the safety and feasibility of IVL in calcified coronary lesions.[17][6] The Disrupt CAD III (ClinicalTrials.gov Identifier: NCT03595176) is an ongoing prospective, multicenter, single-arm study evaluating the safety and effectiveness of IVL in de novo calcified coronary arteries.

Anatomy and Physiology

Vascular smooth muscle dysfunction primarily contributes to calcium deposition within the blood vessel walls; this cascade occurs through microvesicle release with subsequent dysregulation of mineralization inhibitors leading to extracellular calcium deposition within the intimal and medial layers of the vessel. Alternatively, although there are reports of intracellular calcium deposition, the precise incidence and significance of the pathophysiology remain unknown at this current time. Computed tomography coronary angiography (CCTA) is a non-invasive diagnostic modality that can detect both medial and intimal coronary vessel calcification with accuracy.[18][19]

Indications

The use of IVL is presently limited to calcified plaque modification within the innate coronary and peripheral arterial vasculature; however, growing evidence suggests that the device may also be beneficial for facilitating interventions of the major aortic arch vasculature and distal abdominal aorta and iliofemoral vasculature for facilitating large bore access and therapies such as transcatheter aortic valve replacement (TAVR) and endovascular aneurysm repair (EVAR) and thoracic endovascular aortic repair (TEVAR).[20][21] The use of IVL in unique clinical presentations such as chronic total occlusion, unprotected left main calcified stenosis, and calcium-related stent under expansion is under investigation.

Contraindications

The current manufacturer recommendation states that the clinician should not deploy the device if they are unable to advance a 0.014-inch guidewire across the plaque. Also, the procedure should not be attempted in patients suffering from coronary in-stent restenosis (ISR), though its successful off-label use for this entity has been previously described.[22]

Equipment

The IVL utilizes a one-time disposable monorail catheter with an internally mounted ultrasound core positioned around a 0.014″ guidewire. A balloon surrounds the central apparatus; this inflatable equipment is of constant length measuring 12 millimeters (mm) however comes in various diameters ranging between 2.5 and 4.0mm, these device configurations allow the catheter to cross widths from 0.043″ to 0.046″.

Also, the IVL system incorporates a portable regenerator to provide energy to supply two sets of radiopaque and traditional emitters, which are within the central and lateral boundaries of the balloon; these transmitters produce intermittent sonic pressure waves resulting in the delivery of mechanical energy to the target lesion. The acoustic energy results in the creation of micro-cracks within the calcified plaque with each transmission and consecutive impulses cause an increase in vessel compliance with preservation of underlying wall composition, allowing complete balloon opening at substantially reduced atmospheric pressures compared to more conventional techniques.

Personnel

An interventional cardiologist can perform the procedure without any further sub-specialized training.

Preparation

Vessel diameter is the determining factor for balloon sizing for the procedure; a traditional balloon is usually necessary to be advanced to calculate vessel width. Subsequently, a 1 to 1 ratio is used to find appropriate balloon sizing. Although typically a 6 French (Fr) system is used for IVL insertion, a 5 Fr catheter could also be an option in cases where the native radial artery has a small diameter.  Intravascular imaging plays an invaluable role in the accurate balloon size selection and evaluation of calcium morphology.[23][24][25][26][27]

Technique

The device is inflated to 4 atmospheric pressures (ATM) and is advanced through the target plaque, ten rounds of pulsatile sound waves are delivered via transmitters within each emission cycle, the balloon is subsequently deflated, allowing formed bubbles to disburse safely, then, the procedure is repeated for a minimum of two interventions per 12mm target field. Intravascular ultrasound (IVUS) and optical coherence imaging (OCT) can be performed following the procedure to localize calcium fractures and evaluate procedure success.

Complications

The use of IVL for management of calcified coronary lesions like other lithotripsy therapies may theoretically predispose to membrane depolarization; however, sufficient clinical data to support this is lacking at present. In addition, coronary artery perforation may occur due to barotrauma from either low-pressure balloon inflation or high energy acoustic wave emission, though rates have been low in clinical trials.

Clinical Significance

Calcified coronary lesions can cause significant hindrance to percutaneous interventions; such challenging plaques have conventionally been treated with high-pressure balloon expansion and possible atherectomy. However, these therapies are known not to be able to target all lesions successfully.

IVL provides significant advantages to earlier balloon-based interventions; the device does not require further training and is performable by a majority of interventional cardiologists, balloon opening pressure is low which reduces the risk of vascular injury, possible reduction in distal embolization potential, circumferential plaque targeting and a decrease in bias while passing the guidewire.

IVL is associated with the potential to cause significant fractures in most calcified lesions of patients who require coronary revascularization. Further, the device can be used with remarkable success and a small incidence of complications. The use of IVL has the potential to optimize stent expansion by allowing more effective vessel lumen dilatation.

Enhancing Healthcare Team Outcomes

IVL is an important adjunctive tool in the cardiac catheterization laboratory that can be useful for lesion preparation and guidance of optimal percutaneous coronary interventions. Utilization of intravascular imaging modality is vital in defining the calcium density, depth, and circumferential extent and choosing optimal lesion modification strategy afterward and assessment for having achieved an adequate endpoint.


Article Details

Article Author

Nausharwan Butt

Article Author

Nauman Khalid

Article Editor:

Evan Shlofmitz

Updated:

2/6/2021 1:33:26 PM

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