The present study retrospectively evaluated the impact of ESV systems on contrast media volume and radiation exposure for patients underwent PCI procedures. To best of our knowledge, we firstly reported the comparative results of contrast media usage between the group guided by an ESV system and group guided by standard angiography. It was shown that a significant reduction in contrast media volume, radiation exposure (in Air Kerma) and procedure time with the use of ESV systems. Similar results were observed in the subgroup analysis for the patients with CKD.
ESV system is a fluoroscopic based technique, which could provide enhanced visualization of stents with adequate imaging for diagnosis and guidance. Studies showed that it increases the amount and quality of information during PCI to facilitate the identification of bifurcation stenting, precise stent positioning, stent underexpansion and defining stent-vessel wall relationship in case reports(12, 13, 17, 18). Biscaglia et al.(15) demonstrated a novel timing of intraoperative stent fracture identification during the index PCI with the systematic application of ESV. In addition, ESV system was proved an effective assistance in reducing the excessive overlap in implantation of bioresorbable vascular scaffold(14). Furthermore, the results in the study of McBeath et al.(16) showing a significantly improved correlations of an ESV system and clinical outcome. Jin et al.(19) pointed out that the use of an ESV system (Stentboost, Philips) can be performed with comparable radiation dose with conventional x-ray fluoroscopy imaging and suggested that the operator’s experience have an important impact on radiation dose. However, there is a paucity of research that looked at the contrast media usage during PCI of using such a technique.
The current reliable way to perform PCI in minimum or even without contrast administration is guided by intravascular ultrasound imaging (IVUS), which helps to identify the lesion and its length(20). Nevertheless, due to its time-consuming, expensive and requiring for specifically trained personnel, this technique is not routinely used in daily practice(21). In contrast, as an alternative option, ESV systems such as CLEARstent technique only require a few seconds of fluoroscopy or cine images and immediately provide a real time visualization of the stent. With an enhanced visualization, stent positioning, deployment and overlapping could be performed under a clear and intuitive way without repeated contrast needed, thereby greatly lowering the use of contrast media. Especially for complex cases, such as bifurcation lesions, the relationship between stent and wire and detection of re-crossing wire could be evaluated and facilitated with only one fluoroscopy image, omitting repeated enhanced acquisitions to make confirmation. Furthermore, underexpansions could also be detected without contrast injected, which helps physician to perform proper post-dilation in a minimum of contrast medium. As a result, in this study, the use of ESV systems was demonstrated a significantly reduction on contrast media usage compared with the traditional angiography-guided procedure for preventing the occurrence of contrast-induced nephropathy. In the subgroup analysis, for the patient with existing CKD, a similar result on contrast media suggested that ESV-guided PCI has the potential to reduce the damage to renal and mitigate the progression of CKD, which is of great significance for these patients.
Unlike the result of non-significant impact on patient radiation dose in study of Jin et al.(19), who also noted a learning curve of Stentboost imaging and radiation protection, our study found a significant reduction on radiation dose and procedure time in ESV-guided group, maintaining high quality visualization with an optimization of stents. In traditional angiographic procedures, several cines are required to obtain adequate stent visualization while less cine shots are needed for ESV-guided procedures as enhanced visualization of stent deployment eliminates unnecessary radiation exposure. In addition, since fluoroscopy images could also be post-processed using ESV system developed by Siemens Healthineers, radiation dose could be reduced greatly in terms of replacing the regular cines with fluoroscopy. Not only the reduced radiation dose could provide a relatively radiation protection for patients and operators, but also the shortening procedure time could reduce heart failure from prolonged surgical trauma, especially for patients with CKD.
Studies(19, 22) pointed out that operators’ sufficient experience on using the similar technique has an important impact, however we found a steep learning curve for Siemens ESV technique. On the other hand, despite an inevitable learning curve of ESV systems, it could shorten the overall learning curve of percutaneous coronary intervention procedure for especially junior operators. Additionally, it offers some obvious advantages as follows. (1) ESV systems improved visualization of drug-eluting stent. In recent years, the appearance of some new drug-eluting stents has made it more difficult to locate and deploy by traditional angiography methods due to their low relative thickness and x-ray impenetrable materials. ESV systems could significantly improve the positioning and imaging of this self-dilating stent (see Fig. 1). (2) ESV systems enhanced identification of stent underexpansion (see Fig. 2). Incomplete or uneven expansion of stents is the main risk factor affecting short-term and long-term efficacy, as is the case in the era of drug-eluting stents. Timely identification of incomplete expansion of stents is the prerequisite to avoid risks. At present, IVUS is the gold standard for the evaluation of stent structure and dilation level. Under angiographic-based method, contrast media is required to acquire adequate evaluation of stents. As an additional option, ESV systems require no additional contrast media or hardware and provide instant information about its structure. (3) ESV system provided real time guidance for bifurcation lesions (see Fig. 3). On treatment of bifurcation lesions, the use of distal cell when re-wiring was recommended by The European Club to improve procedural outcomes. Angiography and IVUS are unreliable at detecting the site of wire re-crossing. Optical coherence tomography (OCT) has its own advantage in assessing re-wiring, however, additional contrast is also required. ESV systems can enhance the signal of stent struts and increase the visibility of stents to estimate the wire location, with no additional contrast needed. (4) ESV systems increased identification of vascular calcification. Coronary calcification hinders the placement of stents because of potential inadequate stent expansion and difficult transition. However, it is usually difficult to distinguish the stent struts and calcification under standard angiography. ESV systems could identify distribution of calcification with or without a stent being present and distinguish stents from wall calcification. As a result, the reason for insufficient stent expansion could be confirmed immediately to prevent vascular rupture in case of overexpansion (see Fig. 4).
We should acknowledge some limitations. First, this is a single-center retrospective study with a small sample size and thus a larger, multicenter prospective study will be needed in the future. Second, automatic marker detection may misidentify other objects as markers, and this may need additional step of magnification to improve visualization. Third, further studies demonstrating clinical outcomes with a longer follow-up under ESV guidance for especially patients with CKD are also needed.