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Laser Vaporization of Intracoronary Thrombus and Identifying Plaque Morphology in ST-Segment Elevation Myocardial Infarction as Assessed by Optical Coherence Tomography

Laser Vaporization of Intracoronary Thrombus and Identifying Plaque Morphology in ST-Segment... Hindawi Journal of Interventional Cardiology Volume 2021, Article ID 5590109, 12 pages https://doi.org/10.1155/2021/5590109 Research Article Laser Vaporization of Intracoronary Thrombus and Identifying Plaque Morphology in ST-Segment Elevation Myocardial Infarction as Assessed by Optical Coherence Tomography Yuki Yamanaka, Yoshihisa Shimada , Daisuke Tonomura, Kazunori Terashita, Tatsuya Suzuki, Kentaro Yano, Satoshi Nishiura, Masataka Yoshida, Takao Tsuchida, and Hitoshi Fukumoto Cardiovascular Center, Shiroyama Hospital, 2-8-1 Habikino, Habikino 583-0872, Japan Correspondence should be addressed to Yoshihisa Shimada; shimada@shiroyama-hsp.or.jp Received 6 January 2021; Revised 13 June 2021; Accepted 14 July 2021; Published 29 July 2021 Academic Editor: Seif S. El-Jack Copyright © 2021 Yuki Yamanaka et al. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives. We evaluated the thrombus-vaporizing effect of excimer laser coronary angioplasty (ELCA) in patients with ST- segment elevation myocardial infarction (STEMI) by optical coherence tomography (OCT). Background. Larger intracoronary thrombus elevates the risk of interventional treatment and mortality in patients with STEMI. Methods. A total of 92 patients with STEMI who presented within 24 hours from the onset and underwent ELCA following manual aspiration thrombectomy (MT) were analyzed. Results. *e mean baseline thrombolysis in myocardial infarction flow grade was 0.4± 0.6, which subsequently improved to 2.3± 0.7 after MT (p< 0.0001) and 2.7± 0.5 after ELCA (p � 0.0001). *e median residual thrombus volume after 3 3 MT was 65.7 mm , which significantly reduced to 47.5 mm after ELCA (p< 0.0001). Plaque rupture was identified by OCT in only 22 cases (23.9%) after MT, but was distinguishable in 36 additional cases after ELCA (total: 58 cases; 63.0%). Ruptured lesions contained a higher proportion of red thrombus than nonruptured lesions (75.9% vs. 43.3%, p � 0.001). Significantly larger 3 3 3 3 thrombus burden after MT (69.6 mm vs. 56.3 mm , p< 0.05) and greater thrombus reduction by ELCA (21.2 mm vs. 11.8 mm , p< 0.01) were observed in ruptured lesions than nonruptured lesions. Conclusions. ELCA effectively vaporized intracoronary thrombus in patients with STEMI even after MT. Lesions with plaque rupture contained larger thrombus burden that was frequently characterized by red thrombus and more effectively reduced by ELCA. outcome of primary PCI and reduces the mortality rate in 1. Introduction patients with STEMI. Intracoronary thrombus burden is a major determinant However, routine thrombus aspiration remains of un- of adverse clinical outcome in patients with ST-segment certain value in primary PCI for STEMI. Several randomized elevation myocardial infarction (STEMI). Larger studies have demonstrated that manual aspiration throm- thrombus burden limits the success of percutaneous bectomy (MT) for STEMI prevents the occurrence of the no coronary intervention (PCI) for STEMI, as it increases reflow phenomenon and distal embolization, resulting in the rate of procedural complications, such as distal better myocardial reperfusion and reduced myocardial in- embolization and no reflow phenomenon. It is also as- farct size [3–5]. In contrast, larger randomized clinical trials sociated with worse microvascular dysfunction and have not shown the clinical benefit of the routine aspiration greater myocardial damage, thereby significantly affect- strategy compared with standard PCI [2, 6]. *ese contra- ing mortality [1, 2]. *erefore, theoretically, reduction of dictory findings may be attributed to insufficient removal of intracoronary thrombus at the culprit lesion improves the thrombus using current aspiration thrombectomy devices. 2 Journal of Interventional Cardiology Several optical coherence tomography (OCT) studies implantation or drug-coated balloon utilization. All patients demonstrated that MT had no impact on the reduction of received loading doses of oral antiplatelet agents immedi- thrombus burden in STEMI, and substantial residual ately after the procedure, consisting of aspirin (200 mg) and thrombus was observed even after MTat the culprit segment P2Y12 inhibitor (clopidogrel 300 mg or prasugrel 20 mg) if [7, 8]. they were not pretreated with a dual antiplatelet therapy. Excimer laser is a unique revascularization device based A frequency-domain OCT imaging catheter system on the effect of a pulsed ultraviolet (xenon-chloride) laser (Dragonfly OPTIS/ILUMIEN OPTIS OCT Imaging System; that directly targets and vaporizes the thrombus. Excimer Abbott Vascular Inc., Santa Clara, CA, USA) was used in this laser coronary angioplasty (ELCA) has been shown to be safe study. *e OCT imaging acquisition was performed after and effective in acute ischemic-thrombotic coronary syn- MT, ELCA, and final ballooning, with a pullback speed of dromes by successful vaporization of intracoronary 18 mm/s and acquisition of 180 frames/s. Intracoronary thrombus at the target lesion [9–12]. *erefore, ELCA may administration of isosorbide dinitrate (200–500 mg) was be a useful adjunctive strategy with the potential to further performed prior to each pullback. *e acquired OCT raw reduce the thrombotic burden which poorly responds to data were stored and exported in digital format for offline MT. *e purpose of this study was to evaluate the efficacy of analyses using a dedicated offline review system with a ELCA following MT in patients with STEMI, by measuring semiautomated contour-detection software (Abbott Vas- the thrombus burden before and after ELCA using OCT. cular Inc). All OCT images were analyzed by two experi- enced investigators (Y.Y. and D.T.). In case of any discordance between the observers, a consensus reading was 2. Methods obtained from a third investigator (Y.S.). ELCA for thrombotic coronary lesions has been utilized in *e entire length of the atherothrombotic lesion plus our hospital since November 2015. *is was a retrospective 5 mm proximal and distal reference segments were included study of consecutive patients who presented with STEMI in the analysis. Intracoronary thrombus was defined as an within 24 hours after the onset and underwent ELCA under irregular mass attached to the luminal surface or floated OCT guidance at our hospital. STEMI was defined as from the vessel wall and characterized according to the continuous chest pain that lasted >20 min, electrocardio- signal characteristics [1, 13]. *e predominant type of thrombus was categorized according to the signal char- gram showing new ST-segment elevation≥0.2 mV in at least two contiguous precordial leads or ≥0.1 mV in at least two acteristics: highly backscattering with high attenuation contiguous limb leads, and angiographic identification of a (red thrombus), less backscattering and homogeneous coronary thrombotic stenosis or occlusion. *is study was with low attenuation (white thrombus), or a mixture of approved by the ethics committee of our hospital and both (mixed thrombus) [13, 14]. *rombus and lumen conducted in accordance with the principles of the Decla- area were measured by planimetry at 1 mm intervals with ration of Helsinki. Written informed consent was provided the automatic lumen contour and supplementary manual by all patients. correction, and the thrombus and lumen volume were Heparin was administered intravenously with an initial calculated by multiplying the areas in each frame by the number of frames [1, 13, 15]. *e distance between the bolus of 5,000 U, followed by periodic shots to maintain an activated clotting time between 200 and 300 s during the most distal and proximal frames that showed intraluminal procedure. Dextran of mean molecular weight 40 kDa material suggestive of thrombus defined the thrombus (50–100 mL of 10% dextran-40 per hour) was also used length [13]. during the procedure to prevent thromboembolic compli- *e culprit lesion was categorized into four groups: cations. After initial coronary angiography, MT was first plaque rupture, plaque erosion, calcified nodule, and un- performed using a manual thrombectomy device (*rom- identified [1, 14]. Plaque rupture was defined by the presence buster III GR; Kaneka Corp., Osaka, Japan or Export Ad- of fibrous-cap discontinuity with a cavity in the plaque. vance; Medtronic, Dublin, Ireland) and repeated at least Plaque erosion was defined by the presence of an attached thrice until there was no visible thrombotic material in the thrombus overlying an intact and visualized plaque or ir- aspirate. ELCA was subsequently performed using a pulsed regular luminal surface with no evidence of fibrous-cap disruption. Calcified nodule was defined by the presence of xenon-chloride excimer laser system with a wavelength of 308 nm; pulse duration of 135 ns; and output of 175 mJ/pulse nodular protruding calcium or luminal surface disruption (CVX-300P; Royal Philips, Amsterdam, Netherlands). *e over a calcified plaque associated with the thrombus. *e laser atherectomy catheters (ELCA Coronary Laser culprit lesions, unable to be recognized based on the aforementioned criteria by the three observers, were clas- Atherectomy Catheter; Royal Philips) were available in sizes of 0.9, 1.4, 1.7, and 2.0 mm, and the default energy pa- sified as unidentified. rameters were set at a fluence of 45 mJ/mm and a repetition Normally distributed continuous variables are expressed rate of 25 Hz. *e size of the catheter, maximum fluency, and as mean± standard deviation, while nonnormally distrib- repetition rate (up to 60 mJ/mm and 40 Hz, respectively) uted continuous variables are presented as median and and the number of passes were at the operator’s discretion. interquartile range. Categorical variables are expressed as *e laser vaporizing manner employed in this study was counts and percentages. Repeated-measures analysis of variance with post hoc Tukey’s honest significant difference previously described [9]. *e procedure was followed by balloon dilatation and finalized with drug-eluting stent test was applied to compare serial parameters after each Journal of Interventional Cardiology 3 procedure. *e Mann–Whitney U test or Pearson’s chi- but was successfully distinguished in another 36 cases (total squared test was applied to examine differences between the 58 cases: 63.0%) after ELCA (Figures 3 and 4). Among the lesions with ruptured plaque and those with nonruptured other cases, OCT after ELCA demonstrated the morphology plaque. A p value <0.05 was considered statistically sig- of plaque erosion in 23 cases (25.0%) (Figure 5) and calcified nificant. All statistical analyses were performed using the nodule in seven cases (7.6%) (Figure 6), whereas the JMP statistical software (version 13.2; SAS Institute, Cary, remaining four cases (4.3%) were unidentifiable. Red NC, USA). thrombus was observed more frequently in lesions with ruptured plaque than those with nonruptured plaque (75.9% vs. 43.3%, respectively, p � 0.001) (Table 4). Although the 3. Results residual thrombus burden after MT was larger in lesions 3 3 From December 2015 to December 2019, 352 consecutive with ruptured plaque (69.6 mm vs. 56.3 mm , respectively, patients with STEMI who presented within 24 h after the p< 0.05), the vaporizing effect by ELCA on reducing the onset of symptoms underwent emergent PCI at our hospital. thrombus burden was more pronounced in lesions with OCT was not attempted under the following conditions: ruptured plaque than those with nonruptured plaque 3 3 patients with cardiogenic shock (n � 47); STEMI caused by (21.2 mm vs. 11.8 mm , respectively, p< 0.01) (Figure 7). in-stent thrombosis (n � 21) or spontaneous coronary artery dissection (n � 4); impaired kidney function (serum creati- 4. Discussion nine ≥1.5 mg/dl; n � 82); left main disease (n � 16); small- vessel disease (<2 mm in diameter; n � 38); extremely tor- *rombus burden at the culprit lesion remains an important tuous vessels (n � 8); heavily calcified vessels (n � 23); or risk factor for cardiac damage and mortality following other conditions the physicians considered inappropriate primary PCI in patients with STEMI [1, 2]. Mechanical (n � 7). *erefore, 106 patients underwent OCT-guided PCI removal of the occlusive thrombus appears to be a logical with the intention to perform MT followed by ELCA option for the treatment of these highly thrombotic lesions, (Figure 1). Patients in whom it was not possible to advance and several clinical trials demonstrated that MT during the manual aspiration catheter (n � 1) or OCT catheter primary PCI resulted in a lower risk of distal embolization (n � 2) distal to the culprit lesion before ELCA or those with and no reflow phenomenon, better ST-segment resolution, poor OCT image quality (n � 11) were excluded from this preserved microvascular integrity, lower myocardial dam- study. Finally, a total of 92 lesions in 92 patients with STEMI age, and reduced mortality rate [3–5]. However, recent large who underwent aspiration thrombectomy followed by randomized trials and a historical cohort study failed to ELCA of the infarct-related artery were analyzed in this show an additional benefit of routine thrombus aspiration in study. patients with STEMI [2, 6]. *is may be attributed to in- Baseline patient, lesion, and procedural characteristics sufficient removal of the thrombus at the culprit lesion by the are shown in Tables 1 and 2. A laser size of 1.7 mm was used currently available MT devices. Previous OCT studies in>80% of cases, mainly because it is the maximum laser size demonstrated that MT did not significantly reduce the compatible with a 6Fr guide catheter. *e excimer laser thrombus burden at the culprit lesions versus lesions catheter was successfully crossed distal to the culprit lesion without MT [7, 8]. In our study, we also observed a sub- in all cases without any balloon predilatation. *e mean stantial amount of OCT-identified residual thrombus even baseline thrombolysis in myocardial infarction (TIMI) flow after repeated MT. grade on initial angiography was 0.4± 0.6. *e TIMI flow Our study demonstrated that ELCA additionally reduced grade was significantly improved by MT to 2.3± 0.7 thrombus burden at the culprit lesion and restored luminal (p< 0.0001) compared to that at baseline and subsequently flow space, as measured using OCT even after MT. In ad- improved by ELCA to 2.7± 0.5 (p � 0.0001) compared to dition, ELCA significantly enhanced the restoration of an- that at post MT (Figure 2). None of the cases developed terograde TIMI flow of the infarct-related artery without ELCA-induced perforation, angiographical distal emboli- distal embolism. Previous reports have shown ELCA to be zation, or flow-limiting dissection. ELCA-induced TIMI feasible and efficient in primary PCI for STEMI, demon- flow deterioration was observed in two cases (2.2%); how- strating improvement in TIMI flow, TIMI frame count, and ever, no visible distal embolization was detected. TIMI 3 flow TIMI myocardial blush grade [9–12]. *e ELCA effect is was achieved in 87 of 92 patients (94.6%) after adjunctive based on three unique mechanisms of a pulsed xenon- balloon angioplasty and 90 of 92 patients (97.8%) after final chloride laser (photochemical, photothermal, and photo- devices (drug-eluting stent or drug-coated balloon). mechanical), and its thrombus-vaporizing effect may exceed *e results of the OCT analysis are shown in Table 3. the simple mechanical effect of a manual aspiration catheter Compared with those after MT, ELCA significantly reduced on reducing the thrombus burden [16]. 3 3 thrombus volume (from 62.8 mm to 46.2 mm , p< 0.0001), *e products of in vitro excimer laser thrombolysis are resulting in larger lumen volume (from 70.0 mm to reported to be <10 micron in size [17], and previous clinical 87.7 mm , p< 0.0001) and minimum lumen area (from studies reported that ELCA achieved a higher rate of tissue-level 2 2 1.4± 0.7 mm to 2.4± 0.9 mm , p< 0.0001) (after MT and reperfusion (myocardial blush grade, ST-segment resolution) after ELCA, respectively). than MT and balloon angioplasty in patients with STEMI Using the OCT images after MT, plaque rupture at the [18, 19]. However, even invisible microdebris may cause mi- culprit lesion was identified in only 22 of 92 cases (23.9%), crocirculatory impairment during ELCA, such as during 4 Journal of Interventional Cardiology 352 patients with STEMI (i) From Dec 2015 to Dec 2019 82 : serum creatinine ≥1.5 mg/dl (ii) Presenting within 24 hours from onset 47 : cardiogenic shock 38 : small vessel <2 mm in diameter 23 : heavily calcified vessel 21 : in-stent thrombosis 16 : le main disease 8 : extremely tortuous vessel 4 : spontaneous coronary artery dissection 7 : others 106 STEMI underwent OCT-guided PCI 1 : MT catheter unable to cross 2 : OCT catheter unable to cross aer MT 103 STEMI underwent ELCA following MT 11 : poor OCT image 92 STEMI included in detailed OCT analysis Figure 1: Study flow chart. ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; OCT, optical coherence tomography; and STEMI, ST-segment elevation myocardial infarction. Table 1: Patient characteristics. dissolution was more pronounced in lesions with ex- tensive thrombus. *is finding is in line with previous Variable Value studies which showed significantly higher acute laser gain Number of patients 92 in lesions with larger thrombus burden [9, 12]. However, Age (years) 63.5± 12.6 estimating thrombus burden by angiography alone is Male sex 77 (83.7%) often difficult, and a previous study reported that the Hypertension 59 (64.1%) angiographic thrombus grade does not correlate with Diabetes mellitus 38 (41.3%) Hemoglobin A1c (%) 6.5± 1.4 intracoronary thrombus volume as measured by OCT Dyslipidemia 54 (58.7%) [20]. OCT is currently the most reliable method of LDL-cholesterol (mg/dL) 126.4± 38.8 thrombus quantification in vivo [13, 15]. *erefore, it may Current smoking 45 (48.9%) potentially stratify patients with high thrombus burden Serum creatinine (mg/dL) 0.85± 0.78 who further benefit from thrombus dissolution therapy, Prior MI 1 (1.1%) such as ELCA. Prior PCI 1 (1.1%) Vaporizing thrombus by ELCA may assist in under- Symptom onset to hospital arrival (h) 5.5± 5.5 standing the pathophysiology of the culprit lesion in STEMI. Baseline CPK (IU/L) 460± 762 In this study, a significant amount of residual thrombus Baseline CPK-MB (IU/L) 43± 65 hampered the assessment of the underlying plaque mor- Peak CPK (IU/L) 2,868± 2,391 Peak CPK-MB (IU/L) 272± 239 phology in most cases even after MT. *is was mainly because of the fundamental limitation of the OCT signal Data are presented as n (%) or mean± standard deviation. CPK � creatine phosphokinase; CPK-MB � creatine phosphokinase myocardial band; being unable to penetrate red cell-rich thrombus. Even with LDL � low-density lipoprotein; MI � myocardial infarction; its high resolution of OCT imaging, the majority of plaque PCI � percutaneous coronary intervention. ruptures were identifiable after thrombus vaporization by ELCA. Previous studies have reported that the exposed rotational coronary atherectomy, resulting in slow or no necrotic core of ruptured plaque is highly thrombogenic and contains larger amounts of red thrombus compared with reflow phenomenon. In addition, microcirculatory im- pairment can occur more frequently in the setting of acute other plaque phenotypes [21, 22]. Our study demonstrated that adequate removal of sizable red thrombus, which causes myocardial infarction because of reperfusion injury, platelet aggregation, vasospasm, or tissue edema. In this rapid attenuation of the OCT signal, may be required for study, ELCA-induced TIMI flow deterioration was ob- more precise detection of ruptured plaque in the culprit served in two cases (2.2%). We assume that this might be lesion in STEMI. attributable to the microcirculatory disorder, albeit no Aggressive thrombus removal and understanding the visible distal embolization was detected. morphology of the culprit lesion may potentially lead to More thorough removal of thrombus by ELCA may be better management of the therapeutic strategies. In STEMI, beneficial, particularly to patients with large thrombus the pathological culprit lesion is often located proximal or burden. In our study, the effect of ELCA on thrombus distal to the angiographical occlusion site [23]; therefore, Journal of Interventional Cardiology 5 Table 2: Lesion and procedural characteristics. Variable Value Culprit lesion location LAD 41 (44.6%) LCx 11 (12.0%) RCA 40 (43.5%) Angiographic parameters Reference diameter (mm) 2.98± 0.51 Lesion length (mm) 19.0± 4.0 Minimal lumen diameter (mm) 0.15± 0.26 Diameter stenosis (%) 94.6± 9.1 Initial TIMI flow grade TIMI 0 64 (69.6%) TIMI 1 23 (25.0%) TIMI 2 5 (5.4%) Access site and the size of guide catheter Transradial (6 Fr) 84 (91.3%) Transfemoral (6 Fr/8 Fr) 7/1 (7.6%/1.1%) Laser catheter used 1.4 c 15 (16.3%) 1.7 c 74 (80.4%) 1.7 e 2 (2.2%) 2.0 c 1 (1.1%) Maximum energy fluency (J) 56.9± 6.2 Maximum repetition rate (Hz) 27.7± 5.7 Laser pulses delivered 2,338± 1,380 Final device DCB 87 (94.6%) Size of DCB (mm) 3.28± 0.46 Total length of DCB (mm) 28.8± 12.0 DES 5 (5.4%) Size of DES (mm) 3.35± 0.22 Total length of DES (mm) 34.8± 12.1 DCB � drug-coated balloon; DES � drug-eluting stent; LAD � left anterior descending artery; LCx � left circumferential artery; RCA � right coronary artery; TIMI � thrombolysis in myocardial infarction. Baseline Post-aspiration Post-ELCA Post-balloon TIMI 0 n = 64 TIMI 1 n = 23 n = 13 3 1 5 n = 38 n = 27 5 5 TIMI 2 1 18 20 22 TIMI 3 n = 41 39 n = 64 64 n = 87 Figure 2: TIMI flow grade and the number of the patients after each of the procedures. TIMI, thrombolysis in myocardial infarction. 6 Journal of Interventional Cardiology Table 3: Results of optical coherence tomography results. Variable Value *rombus volume (mm ) After manual thrombectomy 62.8 (41.4–85.4) After ELCA 46.2 (28.3–62.3) After ballooning 13.3 (4.0–27.7) Luminal volume (mm ) After manual thrombectomy 70.0 (51.8–86.7) After ELCA 87.7 (66.9–106.3) After ballooning 121.2 (93.3–152.9) Mean reference vessel area (mm /mm) After manual thrombectomy 5.4± 2.0 After ELCA 6.0± 2.0 After ballooning 7.3± 2.5 Minimal lumen area (mm ) After manual thrombectomy 1.4± 0.7 After ELCA 2.4± 0.9 After ballooning 5.6± 2.0 Culprit lesion morphology Ruptured plaque 58 (63.0%) Erosion 23 (25.0%) Calcified nodule 7 (7.6%) Unidentified 4 (4.3%) Predominant type of thrombus Red thrombus 60 (65.2%) White thrombus 18 (19.6%) Mixed thrombus 14 (15.2%) Data are presented as median (interquartile range), mean± SD, or n (%). ELCA � excimer laser coronary angioplasty. nonruptured plaque, such as lesions with plaque erosion, Post manual thrombectomy usually contains less thrombus burden and can be safely Rupture Unidentified managed by oral dual antiplatelet therapy alone without (23.9%) (75.0%) intracoronary stenting [27]. *erefore, in vivo identification of culprit plaque morphology by reducing the intracoronary Erosion (1.1%) thrombus burden with ELCA may assist in developing an Unidentified (4.3%) interventional approach for patients with STEMI. Post-ELCA Calcified nodule (7.6%) Rupture Erosion 4.1. Limitations. *is was a single-center and nonrandomized (63.0%) (25.0%) study wherein ELCA was employed in all lesions. A further randomized study comparing PCI for STEMI with and without 0% 20% 40% 60% 80% 100% ELCA is required to identify the detailed benefits of ELCA. Figure 3: OCT identification of lesion morphology after MT and None of the patients were pretreated with a glycoprotein IIb/IIIa ELCA. Lesion morphology was not identifiable in the majority of inhibitor, as this agent is not available in Japan. Potent anti- cases even after MT because of the residual thrombus occupying platelet or antithrombotic therapies may have influenced the the lumen. Vaporization of the thrombus by ELCA facilitated the efficacy of ELCA in vaporizing the intracoronary thrombus. *e identification of plaque morphology using OCT. OCT, optical thrombus clot at the site of culprit lesion may, to some extent, coherence tomography; MT, manual aspiration thrombectomy; embolize distally during insertion of the OCT or the laser and ELCA, excimer laser coronary angioplasty. catheter. Although the OCT catheter is smaller (3.0 Fr at the distal shaft) and the laser catheter is similar (5.3 Fr; 1.7c) in size to the manual aspiration catheter (5.1 Fr), the possibility that the incomplete stent coverage of the ruptured site is relatively common [24]. *is insufficient lesion coverage appears to reduced thrombus volume was simply because of insertion of have a substantial clinical impact because the stent-un- any catheter into the coronary artery cannot be ruled out; this covered ruptured plaque often exhibits chronic lumen re- may have potentially altered the quantitative analysis of the duction during the healing process [25]. In addition, thrombus volume. *e number of patients included in the although the rupture site appears to be adequately covered present study was relatively small, especially for assessing the by the stent, chronic thrombus dissolution over time may distribution of culprit lesion morphology in STEMI. However, result in late stent malapposition, which is significantly more the sample size of 92 patients treated with ELCA and assessed by frequent in ruptured plaque [26]. On the other hand, OCT to evaluate its efficacy is the largest population analyzed Journal of Interventional Cardiology 7 Baseline A ABC BC Baseline A A B C BC Baseline A AB C BC Figure 4: Examples of plaque rupture. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) enabled the identification of the ruptured cavity (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. 8 Journal of Interventional Cardiology Baseline A AB C BC Baseline A B C BC Baseline A AB C BC Figure 5: Examples of plaque erosion. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) clarified the identification of the attached thrombus overlying the eroded plaque (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. Journal of Interventional Cardiology 9 Baseline A AB C BC Baseline A A B C BC Baseline A AB C BC Figure 6: Examples of calcium nodules. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) clarified the identification of nodular protruding calcium (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. 10 Journal of Interventional Cardiology Table 4: Comparison between ruptured and nonruptured plaque. Ruptured plaque (n � 58) Nonruptured plaque (n � 31) p value Predominant type of thrombus Red thrombus 44 (75.9%) 13 (43.3%) 0.001 White thrombus 5 (8.6%) 12 (40.0%) Mixed thrombus 9 (15.5%) 5 (16.7%) *rombus length (mm) 7.1± 3.1 6.9± 4.2 0.532 *rombus volume (mm ) After manual thrombectomy 70.4 (47.8–89.8) 49.5 (33.9–70.0) 0.035 After ELCA 46.2 (30.4–62.8) 42.2 (26.0–60.9) 0.495 After ballooning 14.4 (3.9–28.0) 12.7 (4.5–31.7) 0.945 Reduction of thrombus volume by ELCA 17.5 (8.9–30.1) 8.5 (0.7–17.7) 0.004 Luminal volume (mm ) After manual thrombectomy 69.5 (52.3–90.4) 70.6 (51.4–80.4) 0.676 After ELCA 91.5 (70.7–107.7) 79.4 (59.9–92.9) 0.068 After ballooning 128.2 (102.8–160.9) 106.4 (79.8–123.9) 0.014 Minimal lumen area (mm ) After manual thrombectomy 1.4± 0.7 1.4± 0.7 0.996 After ELCA 2.5± 1.0 2.3± 0.8 0.588 After ballooning 5.8± 1.9 5.0± 1.9 0.034 Data are presented as n (%), median (interquartile range), or mean± SD. ELCA � excimer laser coronary angioplasty. 3 3 mm mm Post-aspiration Post-ELCA Post-aspiration Post-ELCA (a) (b) Figure 7: Scatter plots of thrombus volume after manual aspiration thrombectomy and laser vaporization. ELCA, excimer laser coronary angioplasty. (a) Ruptured plaque. (b) Nonruptured plaque. with this technique thus far. Finally, the finding of more plaque morphology using OCT. Lesions with plaque rupture rupture after ELCA may not only reflect greater clearance of contained a larger thrombus burden that was frequently thrombus but also be related to laser-induced intimal injury. characterized by red thrombus and was more effectively Although previous studies demonstrated that atheroma mass is reduced by ELCA compared to those with nonruptured minimally ablated by ELCA and that ELCA-induced channels plaque. are relatively smooth without relevant histologic damage [28, 29], ELCA may have caused vascular injury and affected the Data Availability identification of the lesion morphology. Data are available on reasonable request due to privacy/ 5. Conclusions ethical restrictions. In patients with STEMI, ELCA was feasible and effective in additionally reducing the intracoronary thrombus Conflicts of Interest burden and creating a larger blood flow area even after MT. 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Laser Vaporization of Intracoronary Thrombus and Identifying Plaque Morphology in ST-Segment Elevation Myocardial Infarction as Assessed by Optical Coherence Tomography

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Copyright © 2021 Yuki Yamanaka et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Journal of Interventional Cardiology Volume 2021, Article ID 5590109, 12 pages https://doi.org/10.1155/2021/5590109 Research Article Laser Vaporization of Intracoronary Thrombus and Identifying Plaque Morphology in ST-Segment Elevation Myocardial Infarction as Assessed by Optical Coherence Tomography Yuki Yamanaka, Yoshihisa Shimada , Daisuke Tonomura, Kazunori Terashita, Tatsuya Suzuki, Kentaro Yano, Satoshi Nishiura, Masataka Yoshida, Takao Tsuchida, and Hitoshi Fukumoto Cardiovascular Center, Shiroyama Hospital, 2-8-1 Habikino, Habikino 583-0872, Japan Correspondence should be addressed to Yoshihisa Shimada; shimada@shiroyama-hsp.or.jp Received 6 January 2021; Revised 13 June 2021; Accepted 14 July 2021; Published 29 July 2021 Academic Editor: Seif S. El-Jack Copyright © 2021 Yuki Yamanaka et al. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives. We evaluated the thrombus-vaporizing effect of excimer laser coronary angioplasty (ELCA) in patients with ST- segment elevation myocardial infarction (STEMI) by optical coherence tomography (OCT). Background. Larger intracoronary thrombus elevates the risk of interventional treatment and mortality in patients with STEMI. Methods. A total of 92 patients with STEMI who presented within 24 hours from the onset and underwent ELCA following manual aspiration thrombectomy (MT) were analyzed. Results. *e mean baseline thrombolysis in myocardial infarction flow grade was 0.4± 0.6, which subsequently improved to 2.3± 0.7 after MT (p< 0.0001) and 2.7± 0.5 after ELCA (p � 0.0001). *e median residual thrombus volume after 3 3 MT was 65.7 mm , which significantly reduced to 47.5 mm after ELCA (p< 0.0001). Plaque rupture was identified by OCT in only 22 cases (23.9%) after MT, but was distinguishable in 36 additional cases after ELCA (total: 58 cases; 63.0%). Ruptured lesions contained a higher proportion of red thrombus than nonruptured lesions (75.9% vs. 43.3%, p � 0.001). Significantly larger 3 3 3 3 thrombus burden after MT (69.6 mm vs. 56.3 mm , p< 0.05) and greater thrombus reduction by ELCA (21.2 mm vs. 11.8 mm , p< 0.01) were observed in ruptured lesions than nonruptured lesions. Conclusions. ELCA effectively vaporized intracoronary thrombus in patients with STEMI even after MT. Lesions with plaque rupture contained larger thrombus burden that was frequently characterized by red thrombus and more effectively reduced by ELCA. outcome of primary PCI and reduces the mortality rate in 1. Introduction patients with STEMI. Intracoronary thrombus burden is a major determinant However, routine thrombus aspiration remains of un- of adverse clinical outcome in patients with ST-segment certain value in primary PCI for STEMI. Several randomized elevation myocardial infarction (STEMI). Larger studies have demonstrated that manual aspiration throm- thrombus burden limits the success of percutaneous bectomy (MT) for STEMI prevents the occurrence of the no coronary intervention (PCI) for STEMI, as it increases reflow phenomenon and distal embolization, resulting in the rate of procedural complications, such as distal better myocardial reperfusion and reduced myocardial in- embolization and no reflow phenomenon. It is also as- farct size [3–5]. In contrast, larger randomized clinical trials sociated with worse microvascular dysfunction and have not shown the clinical benefit of the routine aspiration greater myocardial damage, thereby significantly affect- strategy compared with standard PCI [2, 6]. *ese contra- ing mortality [1, 2]. *erefore, theoretically, reduction of dictory findings may be attributed to insufficient removal of intracoronary thrombus at the culprit lesion improves the thrombus using current aspiration thrombectomy devices. 2 Journal of Interventional Cardiology Several optical coherence tomography (OCT) studies implantation or drug-coated balloon utilization. All patients demonstrated that MT had no impact on the reduction of received loading doses of oral antiplatelet agents immedi- thrombus burden in STEMI, and substantial residual ately after the procedure, consisting of aspirin (200 mg) and thrombus was observed even after MTat the culprit segment P2Y12 inhibitor (clopidogrel 300 mg or prasugrel 20 mg) if [7, 8]. they were not pretreated with a dual antiplatelet therapy. Excimer laser is a unique revascularization device based A frequency-domain OCT imaging catheter system on the effect of a pulsed ultraviolet (xenon-chloride) laser (Dragonfly OPTIS/ILUMIEN OPTIS OCT Imaging System; that directly targets and vaporizes the thrombus. Excimer Abbott Vascular Inc., Santa Clara, CA, USA) was used in this laser coronary angioplasty (ELCA) has been shown to be safe study. *e OCT imaging acquisition was performed after and effective in acute ischemic-thrombotic coronary syn- MT, ELCA, and final ballooning, with a pullback speed of dromes by successful vaporization of intracoronary 18 mm/s and acquisition of 180 frames/s. Intracoronary thrombus at the target lesion [9–12]. *erefore, ELCA may administration of isosorbide dinitrate (200–500 mg) was be a useful adjunctive strategy with the potential to further performed prior to each pullback. *e acquired OCT raw reduce the thrombotic burden which poorly responds to data were stored and exported in digital format for offline MT. *e purpose of this study was to evaluate the efficacy of analyses using a dedicated offline review system with a ELCA following MT in patients with STEMI, by measuring semiautomated contour-detection software (Abbott Vas- the thrombus burden before and after ELCA using OCT. cular Inc). All OCT images were analyzed by two experi- enced investigators (Y.Y. and D.T.). In case of any discordance between the observers, a consensus reading was 2. Methods obtained from a third investigator (Y.S.). ELCA for thrombotic coronary lesions has been utilized in *e entire length of the atherothrombotic lesion plus our hospital since November 2015. *is was a retrospective 5 mm proximal and distal reference segments were included study of consecutive patients who presented with STEMI in the analysis. Intracoronary thrombus was defined as an within 24 hours after the onset and underwent ELCA under irregular mass attached to the luminal surface or floated OCT guidance at our hospital. STEMI was defined as from the vessel wall and characterized according to the continuous chest pain that lasted >20 min, electrocardio- signal characteristics [1, 13]. *e predominant type of thrombus was categorized according to the signal char- gram showing new ST-segment elevation≥0.2 mV in at least two contiguous precordial leads or ≥0.1 mV in at least two acteristics: highly backscattering with high attenuation contiguous limb leads, and angiographic identification of a (red thrombus), less backscattering and homogeneous coronary thrombotic stenosis or occlusion. *is study was with low attenuation (white thrombus), or a mixture of approved by the ethics committee of our hospital and both (mixed thrombus) [13, 14]. *rombus and lumen conducted in accordance with the principles of the Decla- area were measured by planimetry at 1 mm intervals with ration of Helsinki. Written informed consent was provided the automatic lumen contour and supplementary manual by all patients. correction, and the thrombus and lumen volume were Heparin was administered intravenously with an initial calculated by multiplying the areas in each frame by the number of frames [1, 13, 15]. *e distance between the bolus of 5,000 U, followed by periodic shots to maintain an activated clotting time between 200 and 300 s during the most distal and proximal frames that showed intraluminal procedure. Dextran of mean molecular weight 40 kDa material suggestive of thrombus defined the thrombus (50–100 mL of 10% dextran-40 per hour) was also used length [13]. during the procedure to prevent thromboembolic compli- *e culprit lesion was categorized into four groups: cations. After initial coronary angiography, MT was first plaque rupture, plaque erosion, calcified nodule, and un- performed using a manual thrombectomy device (*rom- identified [1, 14]. Plaque rupture was defined by the presence buster III GR; Kaneka Corp., Osaka, Japan or Export Ad- of fibrous-cap discontinuity with a cavity in the plaque. vance; Medtronic, Dublin, Ireland) and repeated at least Plaque erosion was defined by the presence of an attached thrice until there was no visible thrombotic material in the thrombus overlying an intact and visualized plaque or ir- aspirate. ELCA was subsequently performed using a pulsed regular luminal surface with no evidence of fibrous-cap disruption. Calcified nodule was defined by the presence of xenon-chloride excimer laser system with a wavelength of 308 nm; pulse duration of 135 ns; and output of 175 mJ/pulse nodular protruding calcium or luminal surface disruption (CVX-300P; Royal Philips, Amsterdam, Netherlands). *e over a calcified plaque associated with the thrombus. *e laser atherectomy catheters (ELCA Coronary Laser culprit lesions, unable to be recognized based on the aforementioned criteria by the three observers, were clas- Atherectomy Catheter; Royal Philips) were available in sizes of 0.9, 1.4, 1.7, and 2.0 mm, and the default energy pa- sified as unidentified. rameters were set at a fluence of 45 mJ/mm and a repetition Normally distributed continuous variables are expressed rate of 25 Hz. *e size of the catheter, maximum fluency, and as mean± standard deviation, while nonnormally distrib- repetition rate (up to 60 mJ/mm and 40 Hz, respectively) uted continuous variables are presented as median and and the number of passes were at the operator’s discretion. interquartile range. Categorical variables are expressed as *e laser vaporizing manner employed in this study was counts and percentages. Repeated-measures analysis of variance with post hoc Tukey’s honest significant difference previously described [9]. *e procedure was followed by balloon dilatation and finalized with drug-eluting stent test was applied to compare serial parameters after each Journal of Interventional Cardiology 3 procedure. *e Mann–Whitney U test or Pearson’s chi- but was successfully distinguished in another 36 cases (total squared test was applied to examine differences between the 58 cases: 63.0%) after ELCA (Figures 3 and 4). Among the lesions with ruptured plaque and those with nonruptured other cases, OCT after ELCA demonstrated the morphology plaque. A p value <0.05 was considered statistically sig- of plaque erosion in 23 cases (25.0%) (Figure 5) and calcified nificant. All statistical analyses were performed using the nodule in seven cases (7.6%) (Figure 6), whereas the JMP statistical software (version 13.2; SAS Institute, Cary, remaining four cases (4.3%) were unidentifiable. Red NC, USA). thrombus was observed more frequently in lesions with ruptured plaque than those with nonruptured plaque (75.9% vs. 43.3%, respectively, p � 0.001) (Table 4). Although the 3. Results residual thrombus burden after MT was larger in lesions 3 3 From December 2015 to December 2019, 352 consecutive with ruptured plaque (69.6 mm vs. 56.3 mm , respectively, patients with STEMI who presented within 24 h after the p< 0.05), the vaporizing effect by ELCA on reducing the onset of symptoms underwent emergent PCI at our hospital. thrombus burden was more pronounced in lesions with OCT was not attempted under the following conditions: ruptured plaque than those with nonruptured plaque 3 3 patients with cardiogenic shock (n � 47); STEMI caused by (21.2 mm vs. 11.8 mm , respectively, p< 0.01) (Figure 7). in-stent thrombosis (n � 21) or spontaneous coronary artery dissection (n � 4); impaired kidney function (serum creati- 4. Discussion nine ≥1.5 mg/dl; n � 82); left main disease (n � 16); small- vessel disease (<2 mm in diameter; n � 38); extremely tor- *rombus burden at the culprit lesion remains an important tuous vessels (n � 8); heavily calcified vessels (n � 23); or risk factor for cardiac damage and mortality following other conditions the physicians considered inappropriate primary PCI in patients with STEMI [1, 2]. Mechanical (n � 7). *erefore, 106 patients underwent OCT-guided PCI removal of the occlusive thrombus appears to be a logical with the intention to perform MT followed by ELCA option for the treatment of these highly thrombotic lesions, (Figure 1). Patients in whom it was not possible to advance and several clinical trials demonstrated that MT during the manual aspiration catheter (n � 1) or OCT catheter primary PCI resulted in a lower risk of distal embolization (n � 2) distal to the culprit lesion before ELCA or those with and no reflow phenomenon, better ST-segment resolution, poor OCT image quality (n � 11) were excluded from this preserved microvascular integrity, lower myocardial dam- study. Finally, a total of 92 lesions in 92 patients with STEMI age, and reduced mortality rate [3–5]. However, recent large who underwent aspiration thrombectomy followed by randomized trials and a historical cohort study failed to ELCA of the infarct-related artery were analyzed in this show an additional benefit of routine thrombus aspiration in study. patients with STEMI [2, 6]. *is may be attributed to in- Baseline patient, lesion, and procedural characteristics sufficient removal of the thrombus at the culprit lesion by the are shown in Tables 1 and 2. A laser size of 1.7 mm was used currently available MT devices. Previous OCT studies in>80% of cases, mainly because it is the maximum laser size demonstrated that MT did not significantly reduce the compatible with a 6Fr guide catheter. *e excimer laser thrombus burden at the culprit lesions versus lesions catheter was successfully crossed distal to the culprit lesion without MT [7, 8]. In our study, we also observed a sub- in all cases without any balloon predilatation. *e mean stantial amount of OCT-identified residual thrombus even baseline thrombolysis in myocardial infarction (TIMI) flow after repeated MT. grade on initial angiography was 0.4± 0.6. *e TIMI flow Our study demonstrated that ELCA additionally reduced grade was significantly improved by MT to 2.3± 0.7 thrombus burden at the culprit lesion and restored luminal (p< 0.0001) compared to that at baseline and subsequently flow space, as measured using OCT even after MT. In ad- improved by ELCA to 2.7± 0.5 (p � 0.0001) compared to dition, ELCA significantly enhanced the restoration of an- that at post MT (Figure 2). None of the cases developed terograde TIMI flow of the infarct-related artery without ELCA-induced perforation, angiographical distal emboli- distal embolism. Previous reports have shown ELCA to be zation, or flow-limiting dissection. ELCA-induced TIMI feasible and efficient in primary PCI for STEMI, demon- flow deterioration was observed in two cases (2.2%); how- strating improvement in TIMI flow, TIMI frame count, and ever, no visible distal embolization was detected. TIMI 3 flow TIMI myocardial blush grade [9–12]. *e ELCA effect is was achieved in 87 of 92 patients (94.6%) after adjunctive based on three unique mechanisms of a pulsed xenon- balloon angioplasty and 90 of 92 patients (97.8%) after final chloride laser (photochemical, photothermal, and photo- devices (drug-eluting stent or drug-coated balloon). mechanical), and its thrombus-vaporizing effect may exceed *e results of the OCT analysis are shown in Table 3. the simple mechanical effect of a manual aspiration catheter Compared with those after MT, ELCA significantly reduced on reducing the thrombus burden [16]. 3 3 thrombus volume (from 62.8 mm to 46.2 mm , p< 0.0001), *e products of in vitro excimer laser thrombolysis are resulting in larger lumen volume (from 70.0 mm to reported to be <10 micron in size [17], and previous clinical 87.7 mm , p< 0.0001) and minimum lumen area (from studies reported that ELCA achieved a higher rate of tissue-level 2 2 1.4± 0.7 mm to 2.4± 0.9 mm , p< 0.0001) (after MT and reperfusion (myocardial blush grade, ST-segment resolution) after ELCA, respectively). than MT and balloon angioplasty in patients with STEMI Using the OCT images after MT, plaque rupture at the [18, 19]. However, even invisible microdebris may cause mi- culprit lesion was identified in only 22 of 92 cases (23.9%), crocirculatory impairment during ELCA, such as during 4 Journal of Interventional Cardiology 352 patients with STEMI (i) From Dec 2015 to Dec 2019 82 : serum creatinine ≥1.5 mg/dl (ii) Presenting within 24 hours from onset 47 : cardiogenic shock 38 : small vessel <2 mm in diameter 23 : heavily calcified vessel 21 : in-stent thrombosis 16 : le main disease 8 : extremely tortuous vessel 4 : spontaneous coronary artery dissection 7 : others 106 STEMI underwent OCT-guided PCI 1 : MT catheter unable to cross 2 : OCT catheter unable to cross aer MT 103 STEMI underwent ELCA following MT 11 : poor OCT image 92 STEMI included in detailed OCT analysis Figure 1: Study flow chart. ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; OCT, optical coherence tomography; and STEMI, ST-segment elevation myocardial infarction. Table 1: Patient characteristics. dissolution was more pronounced in lesions with ex- tensive thrombus. *is finding is in line with previous Variable Value studies which showed significantly higher acute laser gain Number of patients 92 in lesions with larger thrombus burden [9, 12]. However, Age (years) 63.5± 12.6 estimating thrombus burden by angiography alone is Male sex 77 (83.7%) often difficult, and a previous study reported that the Hypertension 59 (64.1%) angiographic thrombus grade does not correlate with Diabetes mellitus 38 (41.3%) Hemoglobin A1c (%) 6.5± 1.4 intracoronary thrombus volume as measured by OCT Dyslipidemia 54 (58.7%) [20]. OCT is currently the most reliable method of LDL-cholesterol (mg/dL) 126.4± 38.8 thrombus quantification in vivo [13, 15]. *erefore, it may Current smoking 45 (48.9%) potentially stratify patients with high thrombus burden Serum creatinine (mg/dL) 0.85± 0.78 who further benefit from thrombus dissolution therapy, Prior MI 1 (1.1%) such as ELCA. Prior PCI 1 (1.1%) Vaporizing thrombus by ELCA may assist in under- Symptom onset to hospital arrival (h) 5.5± 5.5 standing the pathophysiology of the culprit lesion in STEMI. Baseline CPK (IU/L) 460± 762 In this study, a significant amount of residual thrombus Baseline CPK-MB (IU/L) 43± 65 hampered the assessment of the underlying plaque mor- Peak CPK (IU/L) 2,868± 2,391 Peak CPK-MB (IU/L) 272± 239 phology in most cases even after MT. *is was mainly because of the fundamental limitation of the OCT signal Data are presented as n (%) or mean± standard deviation. CPK � creatine phosphokinase; CPK-MB � creatine phosphokinase myocardial band; being unable to penetrate red cell-rich thrombus. Even with LDL � low-density lipoprotein; MI � myocardial infarction; its high resolution of OCT imaging, the majority of plaque PCI � percutaneous coronary intervention. ruptures were identifiable after thrombus vaporization by ELCA. Previous studies have reported that the exposed rotational coronary atherectomy, resulting in slow or no necrotic core of ruptured plaque is highly thrombogenic and contains larger amounts of red thrombus compared with reflow phenomenon. In addition, microcirculatory im- pairment can occur more frequently in the setting of acute other plaque phenotypes [21, 22]. Our study demonstrated that adequate removal of sizable red thrombus, which causes myocardial infarction because of reperfusion injury, platelet aggregation, vasospasm, or tissue edema. In this rapid attenuation of the OCT signal, may be required for study, ELCA-induced TIMI flow deterioration was ob- more precise detection of ruptured plaque in the culprit served in two cases (2.2%). We assume that this might be lesion in STEMI. attributable to the microcirculatory disorder, albeit no Aggressive thrombus removal and understanding the visible distal embolization was detected. morphology of the culprit lesion may potentially lead to More thorough removal of thrombus by ELCA may be better management of the therapeutic strategies. In STEMI, beneficial, particularly to patients with large thrombus the pathological culprit lesion is often located proximal or burden. In our study, the effect of ELCA on thrombus distal to the angiographical occlusion site [23]; therefore, Journal of Interventional Cardiology 5 Table 2: Lesion and procedural characteristics. Variable Value Culprit lesion location LAD 41 (44.6%) LCx 11 (12.0%) RCA 40 (43.5%) Angiographic parameters Reference diameter (mm) 2.98± 0.51 Lesion length (mm) 19.0± 4.0 Minimal lumen diameter (mm) 0.15± 0.26 Diameter stenosis (%) 94.6± 9.1 Initial TIMI flow grade TIMI 0 64 (69.6%) TIMI 1 23 (25.0%) TIMI 2 5 (5.4%) Access site and the size of guide catheter Transradial (6 Fr) 84 (91.3%) Transfemoral (6 Fr/8 Fr) 7/1 (7.6%/1.1%) Laser catheter used 1.4 c 15 (16.3%) 1.7 c 74 (80.4%) 1.7 e 2 (2.2%) 2.0 c 1 (1.1%) Maximum energy fluency (J) 56.9± 6.2 Maximum repetition rate (Hz) 27.7± 5.7 Laser pulses delivered 2,338± 1,380 Final device DCB 87 (94.6%) Size of DCB (mm) 3.28± 0.46 Total length of DCB (mm) 28.8± 12.0 DES 5 (5.4%) Size of DES (mm) 3.35± 0.22 Total length of DES (mm) 34.8± 12.1 DCB � drug-coated balloon; DES � drug-eluting stent; LAD � left anterior descending artery; LCx � left circumferential artery; RCA � right coronary artery; TIMI � thrombolysis in myocardial infarction. Baseline Post-aspiration Post-ELCA Post-balloon TIMI 0 n = 64 TIMI 1 n = 23 n = 13 3 1 5 n = 38 n = 27 5 5 TIMI 2 1 18 20 22 TIMI 3 n = 41 39 n = 64 64 n = 87 Figure 2: TIMI flow grade and the number of the patients after each of the procedures. TIMI, thrombolysis in myocardial infarction. 6 Journal of Interventional Cardiology Table 3: Results of optical coherence tomography results. Variable Value *rombus volume (mm ) After manual thrombectomy 62.8 (41.4–85.4) After ELCA 46.2 (28.3–62.3) After ballooning 13.3 (4.0–27.7) Luminal volume (mm ) After manual thrombectomy 70.0 (51.8–86.7) After ELCA 87.7 (66.9–106.3) After ballooning 121.2 (93.3–152.9) Mean reference vessel area (mm /mm) After manual thrombectomy 5.4± 2.0 After ELCA 6.0± 2.0 After ballooning 7.3± 2.5 Minimal lumen area (mm ) After manual thrombectomy 1.4± 0.7 After ELCA 2.4± 0.9 After ballooning 5.6± 2.0 Culprit lesion morphology Ruptured plaque 58 (63.0%) Erosion 23 (25.0%) Calcified nodule 7 (7.6%) Unidentified 4 (4.3%) Predominant type of thrombus Red thrombus 60 (65.2%) White thrombus 18 (19.6%) Mixed thrombus 14 (15.2%) Data are presented as median (interquartile range), mean± SD, or n (%). ELCA � excimer laser coronary angioplasty. nonruptured plaque, such as lesions with plaque erosion, Post manual thrombectomy usually contains less thrombus burden and can be safely Rupture Unidentified managed by oral dual antiplatelet therapy alone without (23.9%) (75.0%) intracoronary stenting [27]. *erefore, in vivo identification of culprit plaque morphology by reducing the intracoronary Erosion (1.1%) thrombus burden with ELCA may assist in developing an Unidentified (4.3%) interventional approach for patients with STEMI. Post-ELCA Calcified nodule (7.6%) Rupture Erosion 4.1. Limitations. *is was a single-center and nonrandomized (63.0%) (25.0%) study wherein ELCA was employed in all lesions. A further randomized study comparing PCI for STEMI with and without 0% 20% 40% 60% 80% 100% ELCA is required to identify the detailed benefits of ELCA. Figure 3: OCT identification of lesion morphology after MT and None of the patients were pretreated with a glycoprotein IIb/IIIa ELCA. Lesion morphology was not identifiable in the majority of inhibitor, as this agent is not available in Japan. Potent anti- cases even after MT because of the residual thrombus occupying platelet or antithrombotic therapies may have influenced the the lumen. Vaporization of the thrombus by ELCA facilitated the efficacy of ELCA in vaporizing the intracoronary thrombus. *e identification of plaque morphology using OCT. OCT, optical thrombus clot at the site of culprit lesion may, to some extent, coherence tomography; MT, manual aspiration thrombectomy; embolize distally during insertion of the OCT or the laser and ELCA, excimer laser coronary angioplasty. catheter. Although the OCT catheter is smaller (3.0 Fr at the distal shaft) and the laser catheter is similar (5.3 Fr; 1.7c) in size to the manual aspiration catheter (5.1 Fr), the possibility that the incomplete stent coverage of the ruptured site is relatively common [24]. *is insufficient lesion coverage appears to reduced thrombus volume was simply because of insertion of have a substantial clinical impact because the stent-un- any catheter into the coronary artery cannot be ruled out; this covered ruptured plaque often exhibits chronic lumen re- may have potentially altered the quantitative analysis of the duction during the healing process [25]. In addition, thrombus volume. *e number of patients included in the although the rupture site appears to be adequately covered present study was relatively small, especially for assessing the by the stent, chronic thrombus dissolution over time may distribution of culprit lesion morphology in STEMI. However, result in late stent malapposition, which is significantly more the sample size of 92 patients treated with ELCA and assessed by frequent in ruptured plaque [26]. On the other hand, OCT to evaluate its efficacy is the largest population analyzed Journal of Interventional Cardiology 7 Baseline A ABC BC Baseline A A B C BC Baseline A AB C BC Figure 4: Examples of plaque rupture. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) enabled the identification of the ruptured cavity (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. 8 Journal of Interventional Cardiology Baseline A AB C BC Baseline A B C BC Baseline A AB C BC Figure 5: Examples of plaque erosion. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) clarified the identification of the attached thrombus overlying the eroded plaque (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. Journal of Interventional Cardiology 9 Baseline A AB C BC Baseline A A B C BC Baseline A AB C BC Figure 6: Examples of calcium nodules. Angiographic and OCT images after (A) MT, (B) ELCA, and (C) ballooning. Laser vaporization of the thrombus (arrow) clarified the identification of nodular protruding calcium (arrow head). ELCA, excimer laser coronary angioplasty; MT, manual aspiration thrombectomy; and OCT, optical coherence tomography. 10 Journal of Interventional Cardiology Table 4: Comparison between ruptured and nonruptured plaque. Ruptured plaque (n � 58) Nonruptured plaque (n � 31) p value Predominant type of thrombus Red thrombus 44 (75.9%) 13 (43.3%) 0.001 White thrombus 5 (8.6%) 12 (40.0%) Mixed thrombus 9 (15.5%) 5 (16.7%) *rombus length (mm) 7.1± 3.1 6.9± 4.2 0.532 *rombus volume (mm ) After manual thrombectomy 70.4 (47.8–89.8) 49.5 (33.9–70.0) 0.035 After ELCA 46.2 (30.4–62.8) 42.2 (26.0–60.9) 0.495 After ballooning 14.4 (3.9–28.0) 12.7 (4.5–31.7) 0.945 Reduction of thrombus volume by ELCA 17.5 (8.9–30.1) 8.5 (0.7–17.7) 0.004 Luminal volume (mm ) After manual thrombectomy 69.5 (52.3–90.4) 70.6 (51.4–80.4) 0.676 After ELCA 91.5 (70.7–107.7) 79.4 (59.9–92.9) 0.068 After ballooning 128.2 (102.8–160.9) 106.4 (79.8–123.9) 0.014 Minimal lumen area (mm ) After manual thrombectomy 1.4± 0.7 1.4± 0.7 0.996 After ELCA 2.5± 1.0 2.3± 0.8 0.588 After ballooning 5.8± 1.9 5.0± 1.9 0.034 Data are presented as n (%), median (interquartile range), or mean± SD. ELCA � excimer laser coronary angioplasty. 3 3 mm mm Post-aspiration Post-ELCA Post-aspiration Post-ELCA (a) (b) Figure 7: Scatter plots of thrombus volume after manual aspiration thrombectomy and laser vaporization. ELCA, excimer laser coronary angioplasty. (a) Ruptured plaque. (b) Nonruptured plaque. with this technique thus far. Finally, the finding of more plaque morphology using OCT. Lesions with plaque rupture rupture after ELCA may not only reflect greater clearance of contained a larger thrombus burden that was frequently thrombus but also be related to laser-induced intimal injury. characterized by red thrombus and was more effectively Although previous studies demonstrated that atheroma mass is reduced by ELCA compared to those with nonruptured minimally ablated by ELCA and that ELCA-induced channels plaque. are relatively smooth without relevant histologic damage [28, 29], ELCA may have caused vascular injury and affected the Data Availability identification of the lesion morphology. Data are available on reasonable request due to privacy/ 5. Conclusions ethical restrictions. In patients with STEMI, ELCA was feasible and effective in additionally reducing the intracoronary thrombus Conflicts of Interest burden and creating a larger blood flow area even after MT. 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