The role of intravascular ultrasound in percutaneous coronary artery intervention – Nguyen Minh Toan

Journal of military pharmaco-medicine n o 4-2018 166 THE ROLE OF INTRAVASCULAR ULTRASOUND IN PERCUTANEOUS CORONARY ARTERY INTERVENTION Nguyen Minh Toan*; Nguyen Quang Tuan* SUMMARY Objectives: To describe the role of intravascular ultrasonography (IVUS) in assessing the outcome of percutaneous coronary intervention. Subjects and methods: Sixty patients with ischemic heart disease who underwent coronary angiography and intravascular ultrasonography before and after percutaneous coronary intervention. Results: mean (±SD) stent length measured on IVUS was 34.4 ± 2.17 mm, which was longer than mean target lesion length (22.42 ± 1.17 mm), mean stent diameter was 3.21 ± 0.40 mm, equivalent to mean diameter of the far end reference lumen (3.41 ± 0.14 mm). The minimal lumen area (MLA) after the intervention was 8.12 ± 2.84 compared with 4.06 ± 1.65 mm2 before intervention, minimum lumen diameter (MLD) after intervention was 3.85 ± 0.63 compared to 2.06 ± 0.43 mm before the intervention. The rate of completely lumen-attached stent was 81.7% and 96.7% of the cases had the stent that was opened following MUSIC standards. Conclusion: Intravascular ultrasonography (IVUS) is a technique that not only examines the nature of coronary injury accurately, but also evaluates the outcome of the intervention in a fairly comprehensive manner. * Keywords: Coronary artery; Percutaneous coronary artery; Intravascular ultrasound. INTRODUCTION Percutaneous coronary intervention is increasingly common in medical facilities. The main advantage of a percutaneous intervention is that it is easier to perform, avoid systemic anesthesia, open the chest, circulation outside the body, other complications and fast recovery. Thanks to this technique, coronary artery bypass grafts and circulatory reconstruction can also be performed quickly in emergencies. However, its disadvantage is early restenosis and that it does not fully cure chronic obstructive lesions and/or excess fibrosis. Intravascular ultrasound (IVUS) is a technique in which ultrasound transducers are inserted into the vein by attaching it to the distal end of the catheter, the catheter's near-end being attached to the ultrasound. The ultrasound system and IVUS probe show a clear and honest image of the heart and coronary arteries. IVUS is a new, highly accurate method that can be repeatedly performed in assessing coronary artery structure and associated pathologies as well as pre-and post- coronary arterial interventions. This is why we conducted this study: To determine the role of IVUS in assessing the outcome of percutaneous coronary intervention. * Hanoi Heart Hospital Corresponding author: Nguyen Minh Toan (nguyenminhtoan.tm@gmail.com) Date received: 03/02/2018 Date accepted: 05/04/2018 Journal of military pharmaco-medicine n o 4-2018 167 SUBJECTS AND METHODS 1. Subjects. A total of 60 hospitalized patients were enrolled into the study from Cardiovascular Institute, Bachmai Hospital between September 2011 and December 2013. These patients were indicated to receive percutaneous coronary intervention. After coronary intervention, we performed an IVUS as recommended by the ACC/AHA/SCAI [1] to evaluate the effectiveness of the intervention. 2. Methods. All patients underwent clinical examination, laboratory tests and coronary angiography and IVUS as recommended by the ACC/AHA/SCAI. The patient's angiography results will be evaluated by Quantitative Coronary Angiography (QCA) software. All of these patients underwent percutaneous coronary intervention at the National Heart Center. IVUS is performed by Boston Biotech Ilab Ultrasound Imaging System. The obtained image was measured, analyzed and evaluated using iReview version 1.0 software. * Percutaneous coronary intervention assessment criteria: - MUSIC criteria (Multicenter ultrasound - guided stent implantation in coronaries) [2], stent placement under IVUS should meet following criteria: + Minimal lumen areas in the stent must be ≥ 90% of mean reference areas or 100% of the smallest reference area. + The whole stent must be well- attached to the lumen wall. + Stent opens evenly with minimal lumen diameter/maximal lumen diameter ≥ 0.7. - Remodeling Index: RI. RI = EEMA of target lesion /EEMA of mean of reference (Extemal Elastic Membrance Area: EEMA) (mm2). RI > 1: Positive remodeling; RI ≤ 1: negative remodeling * Data analysis: The data of the study was processed according to computerized statistical algorithms using SPSS software program 16.0. RESULTS Table 1: Characteristics of the study subjects. Characteristics Mean ± standard deviation Age 64.88 ± 9.2 Height 160.88 ± 5.82 Weight 58.57 ± 8.74 BMI 22.57 ± 2.66 The mean age of the study was 64.88 ± 9.2 (minimum 44 years, maximun 83 years). Figure 1: Patient distribution by coronary artery lesion positions. A total of 60 patients in the study were divided into two groups: Left coronary (Lm-LAD) group had 42 patients (70%) and the right coronary lesions (RCA) had 18 patients (30%). 46.7% of the patients are male and 46 patients are female, accounting for 23.3%. Journal of military pharmaco-medicine n o 4-2018 168 Table 2: Comparison of stent length versus target lesion size. n = 60 Length (mm) Diameter (mm) Lesion size on IVUS 22.42 ± 1.17 3.91 ± 0.14 Stent size 34.4 ± 2.17 3.21 ± 0.4 The length of the stent selected is greater than that of the target lesion. Table 3: Area and maximal lumen diameter, minimal lumen diameter before and after the intervention (IVUS). Parameters Before intervention (mean ±SD) After intervention (mean ±SD) p Minimal lumen area(mm2) 4.6 ± 1.65 8.12 ± 2,84 < 0.001 Maximal lumen diameter (mm) 2.48 ± 0.46 4.49 ± 0.73 0.002 Minimal lumen diameter (mm) 2.06 ± 0.43 3.85 ± 0.63 0.002 After stent placement, the minimal lumen area was greater than before intervention, difference was statistically significant (p < 0.001). The diameter of the lumenis equivalent to that of the stent. Thus, after stent placement, the area of the lumen was significantly larger than before placing the stent. Table 4: Results of intravascular ultrasound after high pressure ballooning. MUSIC criteria Lesions Percentage (%) Stent opens evenly 58 96.7 Stent closed to the artery walls 60 100 In our study, patients with stent did not attach to the artery wall, we used coronary balloon with higher pressure (14 - 18 atm). The results showed that the success rate following the MUSIC criteria was higher than before the ballooning. 100% of patients had stents well-closed to the vascular wall. Figure 2: Distribution of coronary artery remodeling. Journal of military pharmaco-medicine n o 4-2018 169 In 60 lesions, 52 lesions were calculated for the remodeling index (some lesions that did not count for the remodeling index were lesions at the ostium of the artery so that there was no near- by reference). The majority of lesions (44/52, accounting for 84.61%) had a negative re- structure, only 15.39% (8/60) had positive re-structure. DISCUSSION Mean age of the patients in our study was relatively high (64.88 ± 9.2 years). However, this finding was similar to that in Yamagishi et al’s (64 ± 11 years) and was equivalent to that by Nguyen Phuong Anh, who studied the role of intravascular ultrasound in assessing moderate coronary artery stenosis (64.25 ± 8.95) and greater than the age in the study by Hoang Van Sy’s (60.53 ± 9.71) and Berry's study [5] in 525 patients with an average age of 58 ± 10. IVUS is a technique of direct insertion of ultrasonic transducers into the lumen, so the resulting images clearly reflect and accurately measure the characteristics of the transcutaneous artery and its components, including: lumen, intravascular and plaque (if any). This is a point that can not be evaluated or evaluated incorrectly on the contrast scan because the contrast is only an indirect picture of the lumen filled with contrast medium and the walls do not contain contrast material which can not be accurately assessed. Normally, coronary arteries progress smaller from near-end to far-end. Coronary artery gets smaller depended on the size of the external elastic membrane (EEM) and plaque plus media (PM) at the far-end of the segment. Thus, under normal anatomy, external elastic membrane (EEM) near the right segment is greater than the distance [5]. In our study, for cases that coronary artery interventions did not meet three criteria of the MUSIC, we use stent balloons with higher pressure, ranging from 14 to 18 atmospheres. The results showed that the rate of successful interventions according to the MUSIC standard has increased. All 60 cases (100%) of the stent are well- opened and stick to the wall. IVUS has an important role in evaluating the phenomenon of remodeling, in our study the negative remodeling accounted for 84.61%. Negative reconstructive phenomena occur in the late stages of the atherosclerotic process [7, 8]. Thus, negative re-structure is often observed in more severe lesions. IVUS is a well-known method of assessing coronary artery damage, providing detailed information on coronary artery status, making it the most effective and meaningful intervention in prognosis. CONCLUSION Application of IVUS allows detailed assessment of coronary artery injury pattern before intervention as well as the efficacy after interventions. Mean (±SD) stent length measured by IVUS was 34.4 ± 2.17 mm, which was longer than the mean target lesion length (22.42 ± 1.17 mm), mean stent diameter was 3.21 ± 0.40 mm, which was equivalent to mean diameter of the far-end reference lumen Journal of military pharmaco-medicine n o 4-2018 170 (3.41 ± 0.14mm). The minimal lumen area after the intervention was 8.12 ± 2.84 compared with 4.06 ± 1.65 mm2 before intervention, the minimum lumen diameter after intervention was 3.85 ± 0.63 compared to 2.06 ± 0.43 mm before the intervention. 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