Shockwave Intravascular Lithotripsy to Unprotected Left Main Stem: Pushing the Boundaries of Calcified Plaque Intervention

Calcified coronary lesions often cause suboptimal stent expansion, one of the biggest predictors of stent failure, potentially resulting in stent thrombosis and stent restenosis.¹ Balloon angioplasty in heavily calcified lesions has a minimal effect on calcium modification. Luminal expansion is achieved by stretching and disruption on the non-calcified vessel wall, resulting in an increased risk of dissection.² While traditional calcium modification devices like rotational atherectomy may have a role in treating concentric calcium, their role in eccentric calcium is unclear. Intravascular lithotripsy (IVL) (Shockwave Medical) is a newly available treatment for calcified coronary plaque prior to stent placement.

At low balloon pressure, lithotripsy electrodes inside the system generate pulsatile mechanical energy that disrupts the calcium at the target site and allows for the optimization of stent deployment and expansion. IVL may be a useful tool for interventional cardiologists as the aging population globally will have a higher prevalence of calcified lesions.³

Case Report

A 68-year-old man with hypertension, end-stage kidney disease on hemodialysis, and coronary artery disease presented with chest pain during dialysis. Previous coronary intervention included a drug-eluting stent (DES) in his ostial left anterior descending (LAD) artery 2 years prior. Coronary angiography revealed a severe, eccentric, heavily calcified lesion in the left main stem (LMS) ostium, extending onto the coronary sinus and aortic root (Figure 1A, Video 1), and moderate in-stent restenosis of the LAD stent.

Video 1. Coronary angiography in cranial left anterior oblique showing heavily calcified plaque in ostial left main stem.

Surgical revascularization was deemed too high risk due to severely impaired left ventricular ejection fraction. The use of rotational atherectomy was considered debatable, given the uncertainty of adequate plaque modification of the very large caliber vessel; poor guide support at the ostial LMS was also an issue. Following engagement with a extra-backup (XB) 3.5 guiding catheter (Cordis, A Cardinal Health company), the lesion was crossed with an Asahi Sion Blue guidewire (Asahi Intecc). A 4.0 mm intravascular lithotripsy (IVL) balloon (Shockwave Medical) was inflated to 4 atmospheres (atm) in the LMS and 4 cycles of 10-second lithotripsy pulses were administered (Figure 1B). A 5.5 mm x 12 mm non-compliant balloon was used to pre-dilate the ostial LMS, followed by deployment of a 5.0 mm x 12 mm Resolute Onyx DES (Medtronic) (Figure 1C, Video 2).

Video 2. Coronary angiography in caudal left anterior oblique showing stent placement.

Finally, post-dilation was done using a 6.0 mm x 12 mm non-compliant balloon (Figure 1D), leaving only mild residual stenosis (Figure 1E-F, Video 3).

Video 3. Coronary angiography in cranial left anterior oblique after balloon postdilation showing mild residual stenosis.

Intravascular ultrasound (IVUS) or optical coherence tomography (OCT) were not used in this case due to the large caliber of the LMS, poor guide support, and the ostial location of the stenosis precluding adequate opacification for OCT or co-axial alignment of the IVUS catheter.

Discussion

To our knowledge, this is the first reported case where IVL was used on the ostium of an unprotected LMS. The prospective, multicenter, single-arm DISRUPT CAD I trial showed a 95% rate of clinical success, defined as <50% residual stenosis and no in-hospital major adverse cardiac events (MACE) with coronary IVL. MACE at 6 months was 8.5%, comprised of 3 non-Q-wave myocardial infarctions within the first 30 days and 2 cardiac deaths.⁴ Although our patient was outside the inclusion criteria for the DISRUPT CAD I trial (unprotected LMS and reference vessel diameter >4.0 mm), this case demonstrates how IVL may provide an additional tool to modify coronary calcium and optimize stenting in patients where surgery and rotational atherectomy may be contraindicated. Further research into the performance and outcome of IVL vs standard ballooning and rotational atherectomy is warranted. 

Disclosures: The authors report no conflicts of interest regarding the content herein.

The authors can be contacted via Bernard Wong, MBChB, at bernardwong@hotmail.co.nz

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