Keywords
Calcified coronary lesions - complication - coronary artery disease - intravascular
lithotripsy - percutaneous coronary intervention - stent underexpansion - stents
INTRODUCTION
Management of heavily calcified lesions during percutaneous coronary intervention
(PCI) is often associated with a high incidence of complications and long-term adverse
outcomes.[1] IVL is a novel promising technique for management of intracoronary calcification
by using high-energy sonic waves to modify calcified lesions.[2] However, little experience has been documented within stent underexpansion. We present
a case of severe stent underexpansion due to tight underlying calcifications that
was successfully managed on the same session by IVL.
CASE REPORT
A 66-year-old male patient presented to our Cath Lab for coronary angiography after
having a positive dobutamine stress ECHO scan (large area of ischemia on the left
anterior descending (LAD) artery territory with underlying good left ventricular systolic
function). He had a past history of hypertension and hypercholesterolemia.
Coronary angiography [Figure 1] showed a severe lesion in the proximal LAD artery with mild plaques in other coronaries.
Therefore, a decision was made to proceed with stenting of the proximal LAD.
Figure 1: (A,B) Baseline angiographic views of LAD showing a severe proximal LAD lesion. (C)
Stent inflation showing mid-portion severe underexpansion. (D) Stent postdilatation
showing “dog-boning” effect of balloon. (E) Optical coherence tomography run showing
a severe underexpanded stent with circumferential calcification. LAD, left anterior
descending
Using a right radial approach, the left main stem was cannulated by using a 6F Q4
guide catheter and an ASAHI SION blue guidewire was advanced into the distal LAD.
The lesion was predilated with 2.5-mm and 3.0-mm noncompliant (NC) balloons; then,
it was stented with a 3.5 × 20 mm Supraflex Cruz stent [Figure 1]. However, during stent optimization, there was an initial difficulty to cross through
the middle portion of the stent with a 3.75 × 10 mm NC balloon, but after several
attempts and with the help of a balance heavy weight guidewire the balloon was placed
in the middle of the stent and inflated multiple times up to 18 atmospheres (ATM).
Despite repeated postdilatations of this mid-stent segment [Figure 1], there was a persistent waist of the balloon and the CLEARstent tool illustrated
a severely underexpanded stent. Optical coherence tomography (OCT) revealed a marked
stent underexpansion (minimal luminal area (MLA) 1.0 mm2) due to a thick circumferential layer of calcium just deep to the stent [Figure 1].
Super high-pressure non-compliant balloon (OPN NC) was initially considered for further
postdilation, but due to high risk of perforation a decision was to try an alternative
method. Despite the little documented experience regarding the use of IVL within stent
underexpansion as well as the concerns about a potential adverse interaction between
IVL and recently implanted stents, we decided to proceed with IVL as it seemed to
be the safest approach within this scenario.
Although the guidelines for IVL suggest vessel size: balloon ratio of 1:1, we decided
to use a smaller sized balloon based on the very small MLA, at the underexpanded segment,
measured by OCT as well as the fact that IVL is a slightly bulky balloon and we had
concerns that it might be difficult for a 3.5 IVL balloon to cross such tight stenosis.
Therefore, a 2.5 x12 mm lithotripsy balloon (Shockwave Medical, Fremont, CA) was positioned
across the underexpanded segment of the stent and inflated to 4 ATM; then, 10 shockwave
pulses were delivered at a rate of 1 pulse per second, after which the balloon was
inflated further to 6 ATM for 5–10s [Figure 2]. This was repeated five times, thus delivering a total of 50 pulses. Of note, initially
there was a waist within the lithotripsy balloon, but surprisingly after only four
pulses the balloon suddenly expanded and was no longer waisted. Repeated angiography
showed better stent expansion, and further postdilatation was performed with a 4.0-mm
NC balloon [Figure 2]. Complete stent expansion was confirmed by repeat OCT [Figure 2]. The patient was doing well at the three-month follow-up in the cardiology clinic.
Figure 2: (A) IVL balloon showing absence of “dog-boning” effect. (B) Optical coherence tomography
post-IVL showing good stent expansion. (C) Stent postdilation after IVL. (D,E) Final
angiographic views with fully expanded stent. IVL, intravascular lithotripsy
DISCUSSION
This case report highlights a case when IVL was successfully used to treat a severely
underexpanded freshly deployed coronary stent due to marked circumferential calcification,
as was shown by OCT. The lesion was properly prepared with multiple-balloon predilatation;
however, the stent remained underexpanded. Fortunately, applying shockwave lithotripsy
resulted in uniform proper stent expansion.
Even though a few reports have been recently documented about the use of IVL to treat
coronary stent underexpansion,[2] we assume this case is unique because, to our knowledge, there are only a few reports
about the use of IVL for the treatment of freshly deployed underexpanded coronary
stents.[3],[4],[5] Further, it illustrates an alternative safe and effective approach to deal with
tight calcified lesions when there is a high risk of perforation.[6]
Calcified coronary lesions have been always a challenge for interventional cardiologists,
as in many cases they may hinder the equipment’s passage and may resist adequate modification
both before and after stent implantation. In real practice, there are only limited
treatment options for persistent stent underexpansion and most of the time they carry
high risk. For instance, scoring or cutting balloons can alter the integrity of the
stents, whereas using higher pressure inflations with an NC/OPN balloon predisposes
one to strut fracture, stent deformation, or vessel perforation. Although excimer
laser and rotational atherectomy can achieve successful results, unfortunately, they
are not available in all centers and also carry a few risks, for instance, high target
lesion revascularization rate, strut embolization, and burr entrapment.[7],[8] The IVL acts by modifying intimal and medial calcifications through sending acoustic
pressure pulses that crackle calcium, thus easing stent expansion.[9]
Although applying IVL for de novo calcified coronary lesions has been proved to be
safe and effective, its use in freshly deployed non-endothelialized stents is still
under investigations. Issues such as peeling off the stent’s polymer coat as well
as indenting its metal—predisposing corrosion—have been documented with bench testing
studies; however, a recent case report showed favorable OCT findings at four months
post-IVL for a stent that was deployed one month before IVL.[10]
Finally, although our case offers a potential safe and highly effective tool for the
management of acute stent underexpansion, we must mention that IVL should only be
used on bail-out situations, and priority should always go for lesion preparation
before stent implantation to avoid such complications. Moreover, operators should
have a low threshold of using intra-coronary imaging (e.g. IVUS or OCT) in suspected
highly calcified coronary lesions and never underestimate a lesion’s severity.
In conclusion, IVL may be considered a safe, feasible, and effective alternative approach
to deal with acute stent underexpansion caused by severe calcification. Of note, we
recommend further investigations to confirm this proposed approach, particularly investigating
its long-term outcomes.
