Kun Cui, You-quan Shi, Yuan-zheng Zhang, Zheng-gong Li, Chang-ling Li

1 Department of Cardiology, Chongqing General Hospital, Chongqing 400013, China

2 Department of Cardiology, the Third People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830000, China

3 Department of Cardiology, the First People’s Hospital of Tianshui, Tianshui 741000, China

4 Department of Cardiology, the Second Affi liated Hospital of Zhejiang University School of Medicine, Hangzhou 310009, China

KEYWORDS: Acute coronary syndrome; Intravascular ultrasound; Rotational atherectomy;Underexpanded stent

INTRODUCTION

Over the last decade, the number of percutaneous coronary intervention (PCI) procedures in China has increased more than 20 folds, with 454,505 procedures reported in 2013.[1,2]However, due to the incomplete application of intravascular ultrasound (IVUS) or optical coherence tomography (OCT), many surgeons perform insufficient examination of calcification and dense fibrous plaques of the lesion.In clinical practice, less application of rotatory technique, scoring balloon, or cutting balloon leads to poor pretreatment of lesions.Poor stent expansion has an impact on stent thrombosis and restenosis, which always leads to acute coronary syndrome (ACS).It will reduce the occurrence of ACS if we could effectively treat calcified coronary lesions.[3]

One study showed that among all lesions evaluated by angiography, the incidence of calcified coronary lesions was 38%, and this number was 74% in cases that received IVUS.[4]Rotational atherectomy (RA) has been used as an alternative to the treatment of irreparable calcified lesions, usually with good long-term effects before stent deployment.[5,6]This suggests that RA may be used in underexpanded stent patients with ACS.Through IVUS evaluation of lesions during surgery, information such as vascular calcification, stent swelling, minimum lumen diameter (MLD), and area can be accurately obtained,which provides reliable guidance for subsequent stent rotation.[7-10]At present, studies on rotational atherectomy of underexpanded coronary stents (academically called stent ablation, SA) in patients with ACS are limited to case reports and small-center retrospective analysis.The purpose of this study is to analyze SA in patients with ACS as an eff ective alternative strategy for treating underexpanded stents.

METHODS

Study population

Patients with ACS, who underwent SA in the Second Affiliated Hospital of Zhejiang University School of Medicine for intrastent restenosis due to coronary stent under-expansion between April 2017 and January 2019,were analyzed.All patients had symptomology of unstable angina and previously received high-pressure noncompliant balloon inf lation.All patients signed informed consent forms for the procedure and usage of their medical data for research purposes.

Interventional procedure

Patients were pretreated with dual-antiplatelet therapy before the procedure and the treatment lasted for at least 12 months after the procedure.The RotaLinkPlus system(Boston Scientific, Marlborough, USA) and a standard 0.009-inch guidewire (RotaWire; Boston Scientific,Marlborough, USA) were used to perform SA.Rotational speed was set between 170,000 to 200,000 r/min and all ablation time was less than 15 seconds to prevent risk of thrombosis due to excessive thermal injury.IVUS during the whole operation was needed to obtain information about the health condition of original stent, minimum lumen area(MLA), MLD, effect of SA, and the length of stent that needed to be implanted.

Def initions and follow-up

Procedural success was defined as the successful SA of the underexpanded stent and successful delivery of an adequately apposed stent with residual stenosis ＜30%.Major adverse cardiac events (MACEs) were defined as the composite of death, myocardial infarction, and target vessel revascularization (TVR) events.ACS was defined as recurrent symptoms of unstable angina with new reelevation of cardiac markers to at least twice the upper limit of normal.[11,12]Clinical follow-ups were obtained either by telephone call or by scheduled visit.Clinical end-points included periprocedural and postprocedural myocardial infarction, stent thrombosis, target lesion revascularization,and MACEs.Continuous variables were presented as mean±standard deviation (SD) or median (interquartile range) and categorical data as numbers and percentages.

RESULTS

The main baseline demographic data of the 11 patients are shown in Table 1.Important prevalence of cardiovascular risk factors was found among them.The median left ventricular ejection fraction was 52.3%(45.5%-60.2%) and the median glomerular f iltration rate was 67 (43-78) mL/minute.

The procedural characteristics are shown in Table 2.The clinical outcomes are shown in Table 3.There were no complications including no flow, perforation, or burr entrapment during the interventions.However, vasoactive drugs were needed in two patients because of transient hemodynamic instability.

Table 1.Baseline characteristics

Table 2.Procedural characteristics

Table 3.Clinical outcomes

The lower amount of contrast (130 [120-150] mL) and the lower dose of radiation (1,195.0 [998.0-1,356.0] mGy)were used, which reduced renal damage in patients with renal insufficiency, and protect both patients and surgical staff .More burrs (2 [2-3]) were used in our study.

DISCUSSION

In the absence of intracavitary imaging applications,the understanding of coronary artery calcification was very limited.With the clinical application of IVUS or OCT, surgeons can obtain information about the presence,extent, distribution, and calcification eccentricity index of calcified plaques.[13-15]Such data can guide the selection of revascularization strategies.However, using the traditional PCI surgical method, the calcified lesions are insufficiently understood and pre-treatment is insufficient.This results in poor expansion of the implanted stent, which leads to ACS due to stenosis or thrombosis and aff ects the long-term outcome of patients.[16-18]Underexpanded stents are often treated with high-pressure non-compliant balloons, scoring balloons, or cutting balloons.However, balloons often cause changes in the shape of the stent steel beam or they are eventually unsuccessful in expanding.[19-21]Therefore, in ACS cases with severe calcif ication and ineff ective balloon expansion, SA is often required.Moreover, it is better to perform IVUS for endovascular assessment to guide the internal atherectomy.[22-24]IVUS can provide important parameters that are instructive for subsequent treatment strategies, such as specific segments and causes of stent insuffi ciency, restenosis in whole stent, and MLD.According to the data obtained, the treatment strategy, including the burr size, SA degree, and stent size required, can be correctly selected.

In the ACS case shown in Figure 1, we performed the first-run IVUS examination of the target vessel before SA.The stent size was 3.0 mm×38.0 mm and the MLD of underexpanded stent was 1.8 mm; thus, 1.5 mm was selectedfor the first burr.After SA, repeated IVUS examinations showed that the MLD increased to 1.91 mm, but there was still serious calcification.The size of the second burr was selected as 2.0 mm.After the second SA, the MLD was 2.31 mm.Then, a 3.0-mm scoring balloon with pressure of 16 atm (1 atm=1.01×105Pa) was expanded fully and a new stent with 3.0 mm×23 mm was implanted successfully.Finally, the expansion and adherence of the stent as checked by IVUS were satisfactory.Based on our experience, the first burr size is preferably smaller (0.1-0.2 mm) than the MLD (the size of first burr usually 1.25 mm or 1.50 mm), while the size of the second burr tends to be larger(0.1-0.2 mm) than the MLD after the SA.This burr selection principle “downsize f irst, upsize last” can increase the eff ect of modif ication in the f irst SA and the eff ect of polishing in the second SA.

Figure 1.An ACS case performed with the f irst-run IVUS examination.A:MLD 1.8-1.9 mm indicated by IVUS; B: after the f irst SA with a 1.5-mm burr the MLD became signif icantly larger, but there was still signif icant calcif ication and a partial stent; C: an underexpanded stent with signif icant stenosis; D and E: after the second SA with a 2.0-mm burr, the lesion was treated with scoring balloon expansion and implantation of the stent;ACS: acute coronary syndrome; IVUS: intravascular ultrasound; MLD:minimum lumen diameter; SA: stent ablation.

Limitation

The main limitation of our work was that there were only 11 included patients.

CONCLUSIONS

The main findings of the present study are: (1) SA is a safe and effective strategy in treating underexpanded stent patients with ACS; (2) IVUS used during intervention can reduce the risk of burr entrapment and balloon rupture and increase the success rate of the entire surgical procedure through guiding the selection of stent size and final evaluation of surgical effects; and (3) IVUS can reduce the radiation dose and contrast amount used in the RA procedure.Further analyses in multicenter registries are still required to conf irm these f indings.

Funding:This work was supported by the Chongqing Health Commission (2016ZDXM024), the Zhejiang Provincial Public Welfare Technology Research Project (LGF20H020012), and the Scientif ic Research Project of the Department of Education in Zhejiang(Y21330290).

Ethical approval:The Institution Ethics Committee from the Second Affiliated Hospital of Zhejiang University School of Medicine approved the study.

Conflicts of interests: The authors have no conflicts of interest to declare.

Contributors:KC and YQS contributed equally to this work.All authors read and approved the f inal version of the manuscript.