CLEARstent and CLEARstent Live
Nowadays stent implantation in complex coronary lesions is common and likely to increase CTO kind complex stenting procedures in future.
From inception of stent in Interventional Cardiology the most frequent requirement was seeing the stent position under X-ray. It was required to check if the stent is rightly placed and covering the lesion, rightly expanded and not over expanded, not limiting the flow to other vessels and so on. Till the time bare metallic stent (BMS) was in use the stent visualization was not so difficult task. But the successive iterations in stent design – from bare-metal stents (BMS) to first and second-generation drug-eluting stents (DES) – have seen a progressive decline in the visibility to see stent material construction under fluoroscopy.
This is because the stent struts were thinner starting from 140 µm and it was down to 80 µm. But the physicians are keen to know the stent is located at desired location, whether the stent has expanded properly against the vessel wall and so on. To answer their question Siemens had introduced the CLEARstent and CLEARstent Live in view of making the stent visualization more Clear.
This DES usage has brought down even with predisposing factors during complications procedures like: (1) overlapping stents, (2) vessel tortuosity, vessel curvature proximal to the lesion or a highly angulated vessel, (3) severe calcifiation (highly visible diffuse calcification, >70% of the stented segment), and (4) bifurcation stenting with 2-stent technique.
CLEARstent allows the evaluation of a stent before the implantation, yet it has been designed to deliver highest image quality for assessment of an implanted stent. To achieve this, it takes a couple of seconds acquisition and calculation after which stent will be enhanced to display on screen.
CLEARstent Live makes the image enhancement happen in real time. CLEARstent Live can help as fast as it takes to step on the pedal. It is activated during a low dose acquisition protocol. This allows for catheter manipulation while getting a clear visualization of previously deployed stents or cardiac anatomy in relation to the currently positioned stent. It is very useful in positioning overlapping stent during long lesion stenting cases where first stent needs to have some overlap with the second stent to cover the whole diseased segment. CLEARstent Live allows physician to move stent back and forth to position with minimal overlap of two stents. CLEARstent live helps positioning stent in bifurcation stenting where main and branch vessel need to be stented, for example LAD/Circumflex ostial stent placements.
CLEARstent Live allows the evaluation of stent position which is more essential when evaluating tortuosity before the implantation, it deliver highest image quality for assessment before expanding stent so that vessel curvature and stent stiffness will not cause the pinch of vessel.
CLEARstent Live provides very essential information when vessel is calcfied and stent is placed close to calcium. This allows to access the intima calcium and expanded stent malposition, under expansion. The less incidental outcomes like malapposed, uncovered, under expanded are well addressed by OCT and IVUS (gold standard) and up to a certain limited extent by CLEARstent with fade in and out of vessel with contrast.
The Technical Aspect
Coronary stent implantation is monitored by X-ray fluoroscopy where imaging quality of the guidewires, markers, and stent struts is often low. Basic fluoroscopy/Digital Cine images are done with 7.5 to 15 frames per second so that the cardiac pulsatile movement can be viewed on monitor without much lag of continuity for our eyes. But this can reduce the visibility of stent struts since it moves continuously back and forth.
But in CLEARstent the stent markers of both ends will be re-aligned and multiple images are integrated to be shown as one image. During the integration and motion corrected x-ray stent visualization the stent struts image will be added and boosted up to show the strut lining more sharply and at the same time the background of stent like bones, lungs and other objects which also get integrated and are blurred out to make background more clear. Processed single image will be displayed after a delay of few seconds in exam room as single image.
However in CLEARstent Live this processed image is displayed online without any delay in the exam room. The advantage with respect to movement of stent with online image acquisition is that the movement of stent will be in realtime which allow to position preciously.
CLEARstent is using the same dose level of Cine angiogram dose. Even low dose acquisition which can be used for CLEARstent uses only 50% dose of normal cine dose.
However in CLEARstent Live the dosage used is less than 50% of that of Cine angiogram and with low dose protocol it uses almost as less as a fluoroscopy dose.
Read an interesting published article on evaluating the dose of CLEARstent and CLEARstent Live:
“Comparison of Radiation Exposure in Patients Undergoing Single Vessel PCI (Requiring Single Stent) with and without Clear Stent and Clear Stent Live Technology”.
Case Study 1: Left main bifurcation stenting
Dr. Atul Abhyankar
CLEARstent Live is based on the same principle as CLEARstent, identifying the golden balloon markers and enhancing the stent by rotating and manipulating the images to position the markerson top of each other. In difference to CLEARstent though, this processing is ongoing and displays the live result in real time. CLEARstent Live is used fully to ensure adequate overlap, ensure the struts are expanded against the calcium in calcified arteries. It also ensures proper deployment without malapposed, under expanded stents.
For any further discussions about the case please write to firstname.lastname@example.org
Case Study 2: Overlapping stent placement using CLEARstent Live
48-year-old male patient presented with CAD taken for PTCA of LAD. The LAD diseased with long lesion extending proximal and mid segment of LAD. The first stent was implanted to cover mid segment with longer stent. The proximal part of LAD with covered with short stent. First stent 3.0X48 mm Pronova stent DES was positioned across the mid LAD lesion and dilated. Later a Proximal LAD stenting 3.5X13 mm Pronova Stent DES was positioned across the lesion and dilated. To position the second stent overlapping first stent CLEARStent Live with online was used. Post PTCA dilatation of stent done with 3.5 X13 mm balloon. Check shoot showed excellent result with TIMI (3) flow. Patient was discharged later after full recovery.
CLEARStent and CLEARstent Live can be utilized along with or instead of intracoronary imaging techniques during stent implantation, to assess stent expansion, overlapping, and integrity. CLEARstent Live runs on the Artis system and does not require an additional workstation. It offers full PACS compatibility by saving the resulting scenes as DICOM files.
For any further discussion on this case please write to email@example.com
Case Study 3: Calcified artery post dilation using CLEARstent Live
Dr. E. Arunachalam
With CLEARstent Live, stent enhancement takes place in real time, eliminating cardiac motion in the image during an ongoing acquisition. This allows you to verify the stent position relative to cardiac anatomy or to stents deployed previously. The CLEARstent Live enhanced images are displayed side by side with the acquisition, and the operator can still move the device, facilitating bifurcational stentings or long lesion treatments. Besides providing positioning accuracy, CLEARstent Live can help speed up procedures and lower the amount of contrast agent needed.
For any further discussion about the case please write to firstname.lastname@example.org
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