Lithoplasty: “Disruptive,” but not Ablative: Is This the Best Way to Deal with Heavily Calcified Lesions?

9.3 / IAGS 2019
Session 9: Emerging Therapies Session 2
Lithoplasty: “Disruptive,” but not Ablative: Is This the Best Way to Deal with Heavily Calcified Lesions?
Problem Presenter: Ayman Magd, MD

Statement of the problem

Despite advances in current balloon and stent technology, along with operator experience, coronary calcium remains one of the most challenging frontiers during percutaneous interventions. It impedes stent passage of equipment to the lesions, friction that may damage the polymer coating, and it interferes with optimal stent expansion leading to increased stent thrombosis and late restenosis. Indeed, studies have shown that death, myocardial infarction, and target vessel revascularization are markedly increased in calcified relative to non-calcified lesions. The ROTAXUS trial compared the two current strategies of standard balloon angioplasty for predilatation followed by a Taxus stent vs Rotablation predilatation followed by stenting. The results showed no benefit for Rotablation, with longer procedure times, more perforations, and a higher acute gain that was, however, countered by more late loss resulting in higher restenosis rates. 

Gaps in knowledge

Historically, it has been recognized that an arc of calcium >270° was a predictor of such events, however, interventionists have noticed a worrying unpredictability of such lesions. Recent data from Mahera & Mintz using OCT have shown that the 3 most predictive criteria of MACE in calcified lesions are: (1) calcium thickness >.5 mm, (2) an arc of calcium >270°, (3) length of calcium > 5 mm, and that all three must be present to predict MACE, with calcium thickness being most predictive alone. Traditionally, Rotablator has been utilized for heavily calcified lesions, but barriers to use include the need for highly experienced operators, the occurrence of cracks in the superficial calcium only, and the potential increase in late loss and restenosis. These disadvantages have led to a decrease in Rotablator usage with a current utilization rate of about 5% of cases in the United States and 1% in Europe. Meanwhile, orbital atherectomy is currently undergoing clinical trials to determine its impact relative to Rotablator, although preliminary results show no major differences in patient outcomes. 

Possible solutions and future directions

Shockwave lithotripsy has been successfully used for many years to treat renal stones, but the concept has just recently been adopted for peripheral vessels with success. It acts by creating controlled sonic pressure waves that disrupt hard tissue with no impact on soft tissues. The equipment consists of three parts: (1) A small and compact generator that delivers the pulses; (2) a connector cable; and (3) a catheter that ends in a small balloon which is inserted like a traditional angioplasty balloon but has 2 emitters that pulse 1/second up to 80 pulses at the calcified vascular segment when the balloon is inflated at low pressure of 4-6 atm. By creating an expanding and collapsing vapor bubble sonic wave that generates an internal pressure similar to a localized 50 atm, cracking both intimal as well as deep calcium with multiple fractures, producing a smooth lumen at low balloon inflation pressure, thus minimizing vessel injury along with the potential for optimal stent deployment and apposition at low pressures. The recent DISRUPT trial for heavily calcified coronary lesions, although conducted in a small number of patients, has shown promising results with a very low complication rate. It is notable that there were no instances of perforations or no-reflow, there was 100% stent delivery as well as a low MACE rate at 6 months. This technology has generated considerable optimism among interventionists as a potential breakthrough for these lesions, although future ongoing larger trials must prove its efficacy in calcified lesions relative to Rotablator and orbital atherectomy.