In calcified coronary lesions, treatment with intravascular lithotripsy (IVL) has superior efficacy compared with conventional plain old balloon angioplasty (POBA), a finding confirmed by histological analysis and dedicated intravascular imaging, according to a study of cadaver hearts.

These data were reported by Kenji Kawai, MD, of the CVPath Institute, Gaithersburg, Maryland, and colleagues, in a manuscript published online Monday and in the Sept. 11 issue of JACC: Cardiovascular Interventions.

Citing a study, the authors mentioned that calcifications within coronaries are a commonly encountered problem in patients undergoing percutaneous interventions (PCI), and these calcifications are often associated with periprocedural complications and stent under-expansion that can lead to late restenosis, thrombosis, and reintervention.

They further emphasized that coronary calcification is one of the predictive factors of a poor prognosis in patients undergoing revascularization. Because IVL disrupts calcified lesions without apparent damage to soft tissues, it provides a therapeutic option for calcified lesions in the coronary arteries. Shockwave Medical manufactures the first IVL system approved for clinical use by the U.S. Food and Drug Administration.

“Although intravascular lithotripsy (IVL) has been an emerging novel option to treat vascular calcification, the specific effects on histology have not been systematically examined,” Kawai and colleagues wrote.

Study details

Kawai and colleagues examined the efficacy of IVL in treating calcified coronary lesions and the utility of optical coherence tomography (OCT) and micro-computed tomography (CT) in assessing the treatment effects of IVL in comparison to histology using human coronary arteries with atherosclerotic calcification from donor hearts.

A total of eight coronary lesions were treated with IVL, and seven lesions were treated with POBA (semi-compliant balloon with inflation pressures at 10 atm). Imaging analysis using OCT and micro-CT were performed before and after treatment, and the characteristics of calcium fracture were evaluated to subsequently compare with the corresponding histological assessment.

The lesions demonstrated sheet calcium with an average depth of 1.1 mm in both groups. The team noted a significant difference in histological evidence of calcium fracture between the IVL group and the POBA group, with higher occurrence in the IVL group (62.5% vs. 0.0%; p = 0.01). A total of 14 fractures were identified from those eight histology cross-sections. The authors observed that calcified lesions that exhibited a treatment effect tended to have a larger maximum arc of calcification when compared to lesions that did not respond to treatment (median 145.6 degrees vs. 107 degrees; p = 0.01), whereas the depth of calcification had no impact on the treatment effect.

The study further added that with regard to fracture depth, micro-CT and histological assessment showed excellent correlation (R² = 0.83; p < 0.0001), whereas OCT did not (R² = 0.37; p = 0.11). The depth of fractures by OCT was significantly shorter compared to those by histology (median 0.49 mm vs. 0.88 mm; p = 0.008), whereas no such difference was observed between micro-CT and histology (median 0.91 mm vs 0.83 mm; P = 0.75).

“IVL demonstrated a histologically superior fracturing effect on coronary calcified lesions compared with POBA,” the authors concluded. “OCT failed to identify the presence of some calcium fractures and underestimated the depth of fracture when compared with micro-CT.”

They further added that future investigations should focus on understanding “the implications of IVL-induced calcium fracture parameters for lesion expansion and their impact on clinical outcomes.”

Editorial comments

In an accompanying editorial comment, Jayakumar Sreenivasan, MD, MSc, and Yousif Ahmad, MD, from the Yale University School of Medicine, noted that not much data comparing imaging modalities to evaluate IVL’s treatment affect are available.

The editorialists reiterated that IVL may effectively modify calcium even in the absence of visible fractures on OCT owing to OCT’s limited penetration depth, lower resolution (compared with micro-CT), and guidewire artifacts at fracture sites. Stressing the importance of understanding these concepts during IVL-assisted PCI, they noted that it “may not be absolutely necessary” to show calcium fractions after IVL before the stent is implanted because “calcium microfractures may be adequate in improving vessel compliance and achieving optimal stent expansion.”

Commenting on another important finding from the study, that larger calcium arc is associated with more evident calcium fractures, the editorialists explained that “this does not mean that IVL is not effective in smaller arcs of calcium, simply that there will be fewer detectable fractures.”

Putting the study’s finding of superior efficacy for IVL in perspective, Sreenivasan, and Ahmad said, “this should be interpreted cautiously, as POBA was performed using the semi-compliant IVL balloon with inflation pressures to 10 atm, which is considerably less than what would be used in clinical practice for POBA with noncompliant balloons or other specialty balloons such as cutting balloons, scoring balloons, and OPN balloons..”

Finally, the commenters applauded the investigators for advancing understanding of calcium modification by IVL and how intravascular imaging can identify potential predictors of therapeutic response.

Sources:

Kawai K, Sato Y, Hokama JY, et al. Histology, OCT, and Micro-CT Evaluation of Coronary Calcification Treated With Intravascular Lithotripsy: Atherosclerotic Cadaver Study. JACC Cardiovasc Interv 2023;16:2097-2108

Sreenivasan J, Ahmad Y. Beyond the Arc: Understanding the Mechanism of Coronary Intravascular Lithotripsy. JACC Cardiovasc Interv 2023;16:2109-2111

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