One of the first sessions at this year’s SCAI meeting was “shocking” but only in the sense that it focused on intracoronary lithotripsy and the Shockwave Coronary Rx Lithoplasty System (Shockwave Medical; Santa Clara, CA). In a session supported in part by Shockwave Medical, a diverse group of speakers with experience using this new technology reviewed the mechanism of action of coronary lithotripsy and many of the initial studies performed using this technology. Rather than shocking, I would say the results were encouraging.
The percutaneous treatment of coronary stenoses with significant calcification has been a “thorn in the side” of interventional cardiologists for years. Moderate-to-severe calcification is present in up to one-third of patients with coronary artery disease and up to half of those undergoing percutaneous revascularization in peripheral arteries. This degree of calcification is associated with lower procedural success and increased periprocedural major adverse events. Rotational and subsequently orbital atherectomy techniques have been used to successfully treat calcified stenoses. A promising new method to treat severely calcified lesions is an adaptation of lithotripsy technology for vascular calcification. Lithoplasty was the first term used for application of lithotripsy in angioplasty but has now been replaced by the term "intravascular lithotripsy" (IVL).
Calcium disruption by IVL involves several mechanisms, including axial splitting by compressive circumferential forces and microfracture generation. Compared with atherectomy, IVL appears to produce a greater degree of plaque fracture which subsequently facilitates expansion of the artery. Clinical experience with IVL has shown that it may induce calcium fractures where rotational atherectomy has failed to adequately modify the calcium. IVL also has been tried in the setting of in-stent restenosis due to calcified neoatherosclerosis, or for underexpanded stents implanted in severely calcified lesions.
IVL was approved for use in the coronary circulation in February 2021. More recently, the CMS has ruled that coronary IVL cases performed in a hospital setting will be eligible in the future for an additional payment through a New Technology Add-On Payment.
The system consists of a portable generator, a cable connector with a push button for IVL activation, and the IVL balloon-catheter. Incorporated within the balloon is an array of miniaturized lithotripters. The lithotripters generate shock waves of short duration with a positive pressure peak and negative pressure trough components. The semi-compliant balloon is filled with a mixture of contrast and saline. Within the coronary artery, the balloon is inflated at a subnominal pressure but enough pressure to remain opposed to the vessel wall. This provides a fluid-tissue interface that facilitates coupling of the shockwave energy to the vessel wall.
The results of several key trials were presented including the most recent Disrupt CAD III trial (J Am Coll Cardiol 2020;76:2635-46). Disrupt CAD III was a prospective, single-arm multicenter study that enrolled 384 patients from 47 sites. The primary safety endpoint was freedom from major adverse cardiovascular events (cardiac death, myocardial infarction, or target vessel revascularization) at 30 days. The primary effectiveness endpoint was procedural success defined as successful stent delivery with a residual stenosis <50% and without in-hospital major adverse cardiovascular events. The primary safety endpoint (30-day freedom from major adverse cardiovascular events) was achieved in 92.2%. The primary effectiveness endpoint of procedural success was met in 92.4% of patients. Adverse events such as severe vessel dissection, perforation, abrupt closure, and slow or no-reflow were infrequent, and all < 1% after stent placement. Of interest, acoustic shockwaves can induce localized myocardial depolarization, resulting in atrial or ventricular ectopic beats, either as isolated capture beats or asynchronous cardiac pacing. Although there is a theoretical risk of inducing tachyarrhythmias if the capture occurs during the vulnerable phase of repolarization, no serious ventricular tachyarrhythmias induced by IVL have been reported. Collectively, the three Disrupt CAD trials showed that coronary IVL safely and effectively facilitates stent implantation in severely calcified lesions.
My personal takeaways: IVL is an exciting and attractive new treatment for severely calcified lesions. It combines the familiarity and ease of use of balloon catheters with the calcium-disrupting capability of lithotripsy. IVL is a welcome addition to the tools available for the treatment of calcified coronary stenoses. Nobody should be “shocked” if its use becomes more popular over time.
Illustration Collage by Jennifer Bogartz / sorbetto / gettyimages
