How to cite this article:MIef Hendrickx, Jo Dens, Koen Ameloot, Mathias Vrolix. Intravascular Lithotripsy in Recently Implanted Underexpanded Drug Eluting
Stents. 2019; 15(4): 555918. DOI: 10.19080/JOCCT.2019.15.555918
Percutaneous coronary interventions of severely calcified lesions are often associated to poor procedural outcome and long-term stent failure. Extensive plaque modification by using intravascular lithotripsy can enhance stent expansion.
Severely calcified coronary arteries can be challenging and often require multiple plaque modification techniques before successful stent implantation. Lesion preparation with semi-compliant balloons is usually insufficient. Therefore, special balloons such as non-compliant, cutting, scoring and high-pressure balloons are frequently used. Atherectomy (or laser) is often the final step in lesion modification but is less effective in severe concentric calcification which extends deep in the vessel wall.
Intravascular lithotripsy (IVL) by Shockwave (Shockwave Medical, US) can be used for advanced plaque modification.
Shockwave balloons generate pulsatile sonic pressure waves (up to 50 atmosphere) that passes through the surrounding tissue to create a series of micro-fractures in the calcium at a balloon pressure of 4 atmosphere (atm). In the DISRUPT CAD I study, this resulted in a clinical success of 95% without major dissections or perforations . When lesions are not adequately prepared and calcium is insufficiently cracked, stent implantation may result in severe underexpansion which predisposes to stent thrombosis and in-stent restenosis . The use of IVL to improve expansion of freshly implanted drug eluting stents is currently off-label. We present 2 cases in were IVL is used for successful optimization of expansion of recently implanted drug eluting stents.
The first case is a 50-years old female patient who presented
at the emergency department with Non-ST Elevation Myocardial
Infarction (NSTEMI). The electrocardiogram (ECG) showed
iso-electric ST-T segment with mildly elevated high-sensitive
troponin T (152 ng/L, cut-off < 100 ng/L). Coronary angiography
showed diffuse three vessel disease with the culprit lesion on
the proximal Left Anterior Descendens (LAD) (Figure 1A+B).
Because of the technical feasible approach in a non-diabetic
patient, percutaneous coronary intervention was preferred above
surgical revascularization. The LAD lesion was ad hoc treated and
the other non-culprit lesions on the circumflex (Cx) and Right
Coronary Artery (RCA) were staged.
In the presence of severe calcification of the proximal LAD,
plaque modification was performed using 3.0 mm semi-compliant
balloon, 3.0 mm non-compliant balloon and 3.0 mm cutting
balloon (Wolverine, Boston Scientific, US), followed by stent
implantation (3.0 x 26 mm Resolute Onyx, Medtronic, US) (Fig
2A). Severe angiographic stent underexpansion persisted after
aggressive post-dilatation with a 3.5 mm non-compliant balloon
up to 26 atm (Figure 2B+C).
One week later, the non-culprit lesions on the Cx and RCA
were successfully treated. Six weeks later, re-evaluation of the LAD
stent was performed using Optical Coherence Tomography (OCT).
Both coronary angiography and OCT (Figure 3A+B) confirmed
significant underexpansion of the proximal LAD stent due to severe
concentric calcification. The minimum stent area (MSA) was 2.27
mm² and stent expansion 33%. IVL was performed by using a
3.5 mm Shockwave balloon inflated at 4 atm with application of
80 pulses (8 runs of 10 pulses) at the narrowest segment. After
application of all pulses, the balloon opened nicely (Fig 4A+B).
Post-dilatation with a 3.5 mm non-compliant balloon up to 24
atm was repeated. The final result showed a full stent expansion
with correct strut apposition, confirmed by OCT (Figure 5A+B).
The MSA was 7.92 mm². Three-month clinical follow-up was
reassuring with no subjective angina, normal echocardiography
and exercise test.
The second case is a 64-years old male patient who was
referred to the cathlab because of stable angina and visualization
of a severe stenosis of the proximal LAD on Computer Tomography
(CT) scan. He had a normal resting ECG and preserved left ventricle
function. Coronary angiography confirmed the severe calcified
lesion on the LAD (Figure 6A+B). A 2.5 mm semi-compliant
balloon was used for pre-dilatation. However, balloon rupture
occurred and the balloon could not be retrieved (an intracoronary
snare and a guide extension were not able to pass the balloon). To
dislodge the trapped balloon fragment, which caused ST elevation
due to absent distal flow, the technique of external crush was
used (puncture and ballooning towards the subintimal space)
followed by retrieval of wire and fragmented balloon (Fig 7A).
Although the trapped balloon could now successfully be retrieved,
this caused a perforation Ellis type II (Fig 7B). Since there was
a perforation, no atherectomy was performed. Instead a new
balloon dilatation followed by stent implantation was preferred
(3.0 x 32 mm Synergy, Boston Scientific, US). The stent could seal
the perforation but showed severe underexpansion (Figure 8A+
B). IVL was performed by using a 3.5 mm Shockwave balloon
inflated at 4 atm with application of 60 pulses (6 runs of 10
pulses) (Figure 9A). Post-dilation was performed using a 3.5 mm
non-compliant balloon with an acceptable angiographic residual
underexpansion < 30% (Figure 9B). Seven months clinical
follow-up was reassuring with no subjective angina and normal
echocardiography and exercise test.
Significant stent underexpansion, due to severely calcified
lesions, predisposes to stent thrombosis and in-stent restenosis.
The treatment by the conventional techniques is often limited
because of poor contact with the calcification which extends deep
in the vessel wall. Based on both cases, the use of intravascular
lithotripsy in recently implanted underexpanded stents showed
to be feasible and resulted in clear improvement of stent
expansion despite balloon inflation of 4 atm. This also implicates
that the stents struts may not be an obstacle for the pulsatile sonic
pressure waves of lithotrispy. Similar cases have been presented
previously [3-7]. Therefore, IVL could be an additional tool for
stent optimization and is potentially safer when compared with
super high pressure balloon inflations.
The outcome of both cases was successful, but the effects
of IVL application on the stent polymer and drugs needs to be
investigated more. In non-critical underexpansion (<50% on
angiography), IVL probably can be postponed up to 6 weeks after
implantation to allow drug delivery during the first weeks after