Severe calcified coronary stenosis presents a significant challenge for interventional cardiologists during percutaneous coronary intervention procedures as patients with this condition are at high risk of suboptimal results and poor clinical outcomes. The management of coronary artery disease (CAD) continually evolving with the advancements in therapeutics modalities. Intravascular lithotripsy (IVL) has emerged as a crucial tool in CAD management. This minimally invasive technique uses high frequency sound waves to modify calcified coronary plaques safely and effectively, facilitating optimal stent deployment and improving clinical outcomes. The efficacy of IVL is enhanced by C2+ technology as it ensures consistent plaque modification by delivering the appropriate energy. Managing 120 pulses during IVL procedure is vital for achieving optimal plaque modification. Additionally, integrating optical coherence tomography (OCT) or intravascular ultrasound (IVUS) imaging with IVL provides real time guidance and assessment of plaque modification and stent placement. OCT imaging enables clinicians to accurately assess the extent of plaque modification and evaluate results in real-time, leading to improved procedural outcomes .This combination of technologies ensures accurate and targeted treatment, resulting in higher procedural success rates and better clinical outcomes for patients with CAD. IVL has revolutionized the management of CAD, providing a safe and effective means of plaque modification. Utilizing IVL in CAD management has proven effective in safely modifying calcified plaques, facilitating optimal stent deployment and improving clinical outcomes. In conclusion, the use of IVL as a key therapeutic modality, coupled with C2+ technology along with the integration of OCT imaging for procedural guidance, is essential for enhancing the precision and safety of plaque modification and stent deployment. This approach results in improved clinical outcomes for patients with CAD.
Severe calcified coronary stenosis poses a significant challenge for interventional cardiologists during percutaneous coronary intervention (PCI) procedures (1). Patients with severe calcified coronary stenosis are at a higher risk of experiencing sub-optimal results and poor clinical outcomes (2). Old age, chronic kidney disease, diabetes, and hypertension are commonly associated with the presence of calcium within coronary arteries structure (3), affecting approximately 6 to 20% of patients undergoing PCI (4). Calcification is a prevalent issue in coronary circulation, with moderate to severe calcification observed in approximately one third of patients presenting with either stable disease or acute coronary syndrome(5). Severe calcification is found in around 15% of all interventional cases. This level of calcification is associated with worse acute procedural success, increased periprocedural rates of major adverse cardiovascular events (MACE), and higher long-term rates of in-stent restenosis, stent thrombosis, target lesion revascularization, myocardial infarction, and death (6,7).
Coronary artery calcification (CAC) is an independent factor that reduces the likelihood of successful PCI by hindering the expansion of drug eluting stent (DES)(8). This can potentially cause damage to drug eluting polymers due to friction between stent and the calcium proximal to the stenosis, leading to complications such as impaired stent apposition and expansion, and alteration of elution kinetics and drug delivery (9,10).
Various surgical techniques have been employed to treat calcified coronary arteries, including non-compliant high-pressure balloons, excimer lasers, rotational atherectomy devices, and orbital cutting/scoring balloons (11). These devices, while effective in some cases, are associated with a higher incidence of procedural complications such as distal embolization, perforations, and dissections (10,11). They operate based on tissue compression and tissue debulking. Moreover, their success rates diminish in the presence of unconventional, thick or deep calcifications, and the induced tissue injury can accelerate restenosis and uncontrolled neo-intimal growth (12).
Extracorporeal shock wave lithotripsy, a long-established technique for treating kidney stones with high energy shock waves(13), is now increasingly being used to break down calcified plaques to facilitate stent placement(14). The intravascular lithotripsy (IVL) system transforms electric energy into mechanical energy during low pressure balloon inflation. This technology relies on sonic waves for plaque modification rather than causing direct vascular tissue injury (15,16). By emitting sonic waves to the surrounding tissue, the balloon-based catheter safely fractures both shallow and deep calcium deposits while promoting vessel compliance with minimum soft tissue damage (10,17).
This article reviews the application of shock wave lithotripsy in calcified CAD, benefits of C2+ technology and outcome measures of integration of imaging technique along with.
Mechanism of Action on Intravascular Lithotripsy
IVL is an innovative technique designed to address the challenges posed by heavily calcified coronary artery lesions. Its mechanism of action leverages the principle of shockwave therapy, adapted for cardiovascular applications. IVL utilizes controlled acoustic pressure waves to fracture calcified plaques within arterial wall, facilitating subsequent vessel dilation and stent placement (18,19).
The principle of shockwave therapy involves the generation of high energy acoustic waves that propagate through tissues and create mechanical forces. When these waves encounter a medium with different acoustic properties, such as a calcified plaque within the arterial wall, they induce rapid changes in pressure. These pressure changes result in the formation of microfractures within the calcified material, effectively weakening its structure (Honton & Monsegu, 2022; Kereiakes et al., 2021).
In IVL, shockwaves are generated by a series of emitters mounted on an angioplasty balloon catheter. When the balloon is inflated within the artery, the emitters are activated, producing high energy acoustic waves (20). The shockwaves propagate through the balloon’s saline filled environment, focusing energy on the calcified plaque (21). The saline medium ensures efficient transmission of the acoustic energy with minimal loss. As the shockwaves encounter the dense, brittle calcified plaque, they create microfractures. This process weakens the structural integrity of the plaque without causing significant damage to surrounding soft tissue (22). The resultant fractures in the calcified plaque make it more compliant and easier to dilate with subsequent balloon angioplasty. This modification is crucial for effective stent deployment and optimal vessel expansion (23,24).
IVL System and Procedure
The coronary IVL system encompasses a portable, rechargeable generator and a connector cable equipped with a push button mechanism, enabling manual, rapid exchange-controlled delivery of electric pulses compatible with a six French catheter. This system integrates a semi-compliant balloon catheter, conforming to established angioplasty standards, designed for deployment over a 0.014” guidewire (25).
In the conventional procedure, the IVL catheter is positioned at the lesion site utilizing angiographic marker bands. Upon inflation of the integrated balloon at a sub-nominal pressure of 4 atmosphere using a mixture of saline and contrast solution, the fluid encapsulated between the fully opposed balloon surfaces serves as a coupling medium, enhancing the efficient transmission of sonic pressure waves into the vessel wall to target calcium deposits (18,26). Unlike alternative therapies lacking specificity between calcium and soft tissue, acoustic pressure waves penetrate soft tissue to reach both intimal and medial calcium deposits (10).
The generator generates 3 kilowatts of energy, which is transmitted through the catheter cables and connector to the lithotripsy emitters at a frequency of one pulse per second. The emitters, distributed along the length of the balloon, generate a localized field effect. A brief electrical discharge within the emitters vaporizes the balloon, producing a rapidly expanding bubble that generates a sonic pressure wave, collapsing within microseconds. These waves, exerting nearly 50 atm of pressure, induce a series of microfractures within the calcium deposits (20,24).
Upon delivery of a round of ten pulses, the balloon can be further inflated to nominal pressure, enhancing balloon compliance and ensuring symmetrical expansion, thereby modifying calcium deposits. This modification ultimately enhances vessel compliance and optimizes stent expansion. Subsequent to lithotripsy, operators can proceed with their preferred treatment strategy to maximum patient outcomes. By rendering the treatment of calcified lesions more manageable, IVL simplifies intricate procedures (27).
Critical Aspect for Consideration
IVL is performed using a specialized catheter equipped with a balloon and shockwave emitters. The procedure involves several key considerations to ensure precise and effective plaque modification, such as lesion assessment via imaging techniques such as intravascular ultrasound (IVUS) or optical coherence tomography (OCT) prior to IVL, and catheter placement at the target site (28,29).
Clinical Indications in Coronary Interventions
IVL has emerged as a valuable tool in the management of heavily calcified CAD, particularly in scenarios where traditional methods may be less effective or pose higher risks (28). Calcified coronary lesions, left main CAD, bifurcation lesions, diffused calcified disease, and in-stent restenosis are the key clinical indications for IVL in coronary interventions (30,31).
Intravascular Imaging Benefits
To accurately assess the need for coronary intervention, intravascular imaging techniques have been developed. These methods measure parameters such as the amount of calcium, arc and wall thickness, which can predict adequate stent expansion. Although not used before every intervention, IVUS and OCT imaging have been proven to enhance clinical outcomes in individuals undergoing PCI and associated with lower in-hospital mortality rates (32,33).
IVUS imaging is crucial for identifying, guiding therapy, and evaluating post treatment outcomes in CAD. It provides real-time cross-sectional images that allow precise measurement of vessel wall morphology, lumen opening, and other relevant parameters by inserting a tiny ultrasound transducer attached catheter into an artery. The ultrasound transducer, a primary component of the IVUS system, plays a critical role in determining imaging performance (34).
Similar to IVUS, OCT is an intravascular imaging technique that produces high quality images of vessel wall morphology safely and effectively. It has become widely used for studying coronary arteries, stent placement, and arterial injury (35). OCT employs near infrared light, penetrating tissue to several hundred microns deep, with backscattered light detected using an interferometric setup to reconstruct the sample’s depth profile (36). OCT and IVUS, although similar, use different wave sources, with IVUS having wider axial resolution and greater penetration depth in soft tissue (37). They offer comparable pullback lengths, with IVUS excelling in aorto-ostial lesion visualization and plaque burden assessment and OCT enabling better evaluation of cross-sectional calcium and lipidic plaque thickness (33).
In situations such as tissue protrusion through the stent strut, stent malposition, and stent edge dissection, OCT provides superior morphological evaluation (38), whereas IVUS allows positive remodeling detection during follow up visits (39). The choice between IVUS and OCT depends on the operator’s decision -making process, and both techniques can be used if necessary.
Intravascular imaging is indispensable when exploring complex anatomical structures, such as the left main coronary system (40) or coronary bifurcation lesions (41). Left main coronary stem lesions present unique challenges during PCI, associated with poorer clinical outcomes and a higher need for revascularization (42). Similarly, coronary bifurcation lesions, occurring in 15-20% of PCIs, pose challenges due to traditional angiography’s limitation, leading to poorer procedural success rates and a greater risk of adverse events (43). Intravascular imaging guides PCI device placement, leading to immediate procedural improvement and better long-term outcomes. In terms of IVL, OCT is the preferred imaging method (44).
Both IVUS and OCT play essential roles in guiding complex PCI procedures, offering unique advantages and complementing each other’s limitations. The choice of imaging modality depends on lesion characteristics, procedural requirements, and operator’s expertise, ensuring optimal outcomes for patients with calcified coronary lesions undergoing PCI (45).
Optical Coherence Tomographic Visualization of IVL Induced Calcium Fracture
OCT’s superior resolution allows for more precise visualization of plaque characteristics, leading to more accurate assessment and decision-making during interventions (20). The high-resolution imaging of OCT enables the detection of small intimal tears, microdissections, and neointimal hyperplasia, which are critical for assessing stent deployment and post intervention outcomes (46). OCT provides accurate measurements of lumen dimensions, plaque thickness, and stent strut coverage, facilitating detailed quantitative analysis that aids in optimizing stent placement and evaluating the efficacy of the intervention (47). OCT is also better in differentiating between various types of plaques, such as lipid rich and fibrous caps, due to its detailed imaging capabilities, which is crucial for tailoring specific treatment strategies (48). The OCT sub-studies have consistently demonstrated the primary mechanism of luminal gain following IVL treatment is calcium fracture, without the need for high pressure balloon dilatation (20,35).
Technological Advancement on Pulse Management
An important aspect of IVL management is the monitoring of pulse delivery. Proper pulse delivery is crucial for achieving optimal lesion modification without causing vessel injury (49). One issue that has been raised in the past regarding pulse delivery is the limitation of the device (with C2 technology) to shorter segments, as it was restricted to 80 pulses (18). The Shockwave C2+ catheter addresses this limitation by increasing the number of pulses from 80 to 120, delivered in cycles of 10 pulses each (50). Traditionally, long lesions were better managed with atherectomy (51). The C2+ technological enhancement allows for the treatment of longer calcified lesion with various distribution patterns within the same patient. However, the C2+ catheter’s enhanced pulse delivery allows for comprehensive vessel preparation rather than just lesion preparation. Consequently, the Shockwave C2+ catheter can effectively treat not only superficial and concentric lesions but also nodular and eccentric lesions, which typically require more extensive modification and a higher pulse rate (24).
Experienced IVL practitioners have adopted to the increased pulses by changing their strategy. They now prepare the vessel from the distal end of the calcified segment where the stent will be placed, pulsing from there and pulling back. This approach reserves 80 pulses for the most calcified segment-previously the entire pulse allocation-while using the remaining 40 pulses to address other calcified areas within the lesion. The advantage of this method is that it allows for uniform pulse distribution across the entire artery to be stented, increasing the number of calcium fractures and improving lesion preparation. This refined pulse management strategy, referred to as the ‘power surge’, focuses 50-60% of the IVL energy on the most calcified segment, with the remainder distributed along the lesion. This approach maximizes the therapeutic impact of IVL in heavily calcified coronary lesions (52).
Advantages of IVL
IVL offers several advantages over traditional plaque modification techniques such as rotational atherectomy or laser atherectomy by reducing the risk of vessel injury and associated complications (53). The IVL effectively differentiates between calcified and soft tissues, allowing acoustic pressure waves to pass through soft tissues and specifically impact both intimal and medial calcium deposits, hence selectively targeting calcium (10). The creation of microfractures in calcium deposits improves vessel compliance and optimized stent expansion and optimal stent deployment. Enhanced vessel compliance and optimized stent expansion lead to better long-term outcomes for patients, including reduced restenosis rates (54).
Intravascular lithotripsy represents a significant advancement in the treatment of calcified CAD. By leveraging the principles of shockwave therapy, IVL effectively modifies calcified plaques, enhancing vessel compliance and improving the outcomes of coronary interventions. The introduction of the Shockwave C2+ catheter, with its increased pulse capacity, has expanded the applicability of IVL, making it a valuable tool for addressing complex and diffused calcified lesions. As clinical experience and evidence continue to grow, IVL is poised to become a cornerstone in the management of calcified coronary lesions, offering a safe, effective, and versatile solution for challenging clinical scenarios.
Angsubhakorn N, Kang N, Fearon C, Techorueangwiwat C, Swamy P, Brilakis ES, et al. Contemporary Management of Severely Calcified Coronary Lesions. J Pers Med [Internet]. 2022 Oct 1 [cited 2024 Jun 14];12(10):1638. Available from: /pmc/articles/PMC9605395/
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