Technical success was achieved in all patients.
The VHIVUS evaluation performed after stent deployment showed a not optimal stent-to-wall apposition,
which was not evident at the fluoroscopic evaluation,
in two
patients (3%),
leading to a postdilation (Fig.
1). The VH-IVUS evaluation led to a stent type change in three patients (5%): two close-to-open cell,
one open-toclose cell.
After VH-IVUS plaque evaluation stent changes in size and/or length were not required in any case. In one Patient,
during after-stenting VH-IVUS evaluation, an intraluminal lesion at the distal third of the stent was observed.
This lesion presented ultrasonographic characteristics suggestive for ruptured plaque material protrusion through stent cells,
caused probably by a plaque ‘squeezing’ by the stent; it appeared at the poststent IVUS evaluation as an ipoechoic protrusion (Fig.
2).
It was decided to perform a manual aspiration with a 6 Fr 90 cm long guide catheter (Mach 1 Guide Catheter,
Boston Scientific Corporation,
Natick,
United States).
A subsequent grey-scale IVUS demonstrated the success of the manual aspiration and fragments of embolic plaque material were found in the Embolic Protection Device filter after its retrieval (Fig.
3).
The patient was relocated to the Stroke unit as a precaution and was discharged 3 days after the procedure; no periprocedural neurological symptomatology had arisen.
Mean fluoroscopy time resulted longer in VH-IVUSguided procedures (IVUS group procedure lengthened of 10.35 min).
A periprocedural self-resolving transient ischaemic attack was observed in one patient (1.6%) which underwent VH-IVUS-assisted procedure.
No other periprocedural or long-term cerebrovascular accidents (e.g.
transient ischaemic attack,
ipsilateral minor or major stroke,
death,
acute myocardial infarction) were observed.
Difference between the two groups resulted not significant (P<0.05).
At the 14 months follow-up,
three (5%) significant (>70%) restenoses,
which required a secondary angioplasty,
were observed; two cases (3%) were observed in the angiography-guided-only group and one case in the IVUS-assisted group.
The difference between the two groups resulted not significant (P<0.05).
Discussion
IVUS has been exhaustively described as valid diagnostic tool for the intraprocedural evaluation of the coronary plaque morphology for the percutaneous transluminal angioplasty and stenting real-time assistance (7–10). There are currently no definitive evidences of its usefulness in CAS procedures,
even if some studies are available.11,12 Whenever a preprocedural CT-angiography or MRangiography is not available,
the angiographic evaluation tipically requires a multiplanar assessment for an accurate vessel measurement and an adequate stent choice; moreover,
the angiography offers a vessel luminography, with few or none informations about the morphology and composition of the atherosclerotic plaque.
A preprocedural DUS evaluation is highly operator-dependant,
and
certain plaques,
as the highly calcific ones,
are poorly evaluated through this technique.
These limitations may be addressed by IVUS.
The 3608 IVUS vessel Imaging may reduce the need to perform calibrated angiogram runs for stent sizing; the need of a lower number of angiogram runs may,
moreover,
lead to a reduction of the overall administered contrast media volume and of the radiation exposure.2,7 In our study,
the careful preprocedural assessment of vessel size,
plaque morphology and aortic arch obviated the need of the diagnostic calibrated angiograms;
this resulted in comparable values of contrast media administration between the two groups and a higher procedural time and radiation exposure,
as well as procedural overall costs,
in the IVUS-assisted
group. In our experience,
VH-IVUS evaluation led to stent type change only in three patients (5%),
with no change in the size and length,
indicating a satisfying concordance with CTA or MRA about the stent choice; although these results are preliminary and need to be confirmed by observations on higher samples,
we believe that VHIVUS, although flawed by a lower spatial resolution and bidimensional output,
may offer a satisfying preprocedural evaluation of plaque ultrastructure and morphology even in carotid plaques. Undeniably,
IVUS has the advantage of a real-time procedural evaluation over MRA and CTA,
which may be useful when treating plaques which are highly prone to rupture,
such as the inflamed ones,
or whenever the operator needs to counter-check the fluoroscopic images for undiagnosed residual stent deformity and suboptimal wall stent apposition.7,8,11,12 In this study IVUS assessment
resulted useful after stent deployment in two cases, in which poor stent expansion,
which was not evident at the fluoroscopic evaluation,
was found.
Some authors, such as Inglese et al.2 and Clark et al.13 believe that the early identification and resolution of a not optimal stent expansion may determine a reduction in the in-stent restenosis rate.
In our study,
however,
the restenosis rate did not significantly differ between the two groups. The comparison of pre-CAS and post-CAS IVUS examination,
moreover,
led to an unexpected result in one case,
in which a focal plaque protrusion through the stent cells,
determined by a plaque compression by the stent,
was observed.
This complication,
which otherwise would have been unnoticed,
was readily solved by intraprocedural manual aspiration of the debris and,
thus, a potentially dangerous intraprocedural embolic complication was prevented.
Though this study provides preliminary results,
to our knowledge this is the first randomized prospective study in which IVUS is used for the CAS intraprocedural evaluation.
The main limitation of this study is the small
number of enrolled patients,
which should be increased in order to confirm the resulted data.