Role of Intravascular Ultrasound in Prediction of Acute Side Branch Occlusion in Coronary Artery Bifurcation Lesions Just After Provisional Stenting

INTRODUCTION

The European Bifurcation Club (EBC) describes coronary bifurcation lesions as coronary artery stenosis with more than 50% stenosis of the main vessel (MV) arising beside to or affecting the root of side branches^1,2. The most important factor in bifurcation stenosis is to make the stenting technique as straightforward as possible by using the provisional single stent strategy ³. This technique is based on data from many studies which did not show any advantage of two-stent over one-stent strategy⁴. Intravascular ultrasound (IVUS) is an important tool during PCI as it provides data about the properties of pre-PCI lesions as vulnerable plaques, lesion severity, length, morphology, stent expansion, apposition, and complications after stent implantation^5,6. Several studies compared findings with angiographic evaluation alone versus under the guidance of IVUS, and showed lower major adverse cardiac events (MACE) and cardiac death rates at follow up were seen in the IVUS group^7,8,9. At the beginning of the procedure, risk factors for SB

occlusion after provisional stenting technique should be recognized such as SB stenosis and acute angel of SB ^10-15. In this study, we are trying to understand the usefulness of IVUS to help in the prediction of SB collapse after provisional stenting.

PATIENTS AND METHODS

This was a prospective observational study performed from May 2019 to December 2020, and included 80 patients submitted for elective percutaneous coronary intervention at the cardiology department in Maadi Military Hospital. Patients with recurrent chest pain and their coronary angiography revealed bifurcation stenosis stented by provisional stenting were included in the inclusion criteria. We excluded the patients presented for primary PCI, patients with left main bifurcation stenosis and patients with side branch had a TIMI flow ≤ 2 before MV stenting. The institutional ethics committee approved the research procedure. Venous samples were withdrawn upon admission, then collected into

standardized tubes containing the potassium ethylene di nitro tetra acetic acid (EDTA) reagent, and stored at room temperature. Serum troponin, creatinine, lipid profile were included. ECG and echocardiography were performed. Coronary angiography plus PCI data were recorded, and IVUS measurements were taken. The Volcano Eagle Eye IVUS Platinum Catheter was used in this study, and was inserted it into the main vessel (MV) in all patients prior to stent implantation. After IVUS measurements, the definition of SB was the branch with diameter ≥ 1.5 mm. SB was considered to be occluded if it had TIMI flow ≤ 2 after main vessel stenting. The IVUS catheter crossed the lesion and withdrawn at about 1 mm/sec after guide wire crossing in the MV to show the imaging sequence, and it began distal to the stenosis site, and terminated at the aorta. We calculated the minimum lumen diameter (MLD) of MV, minimal luminal area (MLA), minimum vessel diameter (MVD), and external elastic membrane (EEM) area of MV at the junction site. The plaque area was determined as EEM CSA minus MLA. We measured the thickness of the MV plaque at the junction position, and we used the thinner plaque at the junction position as a measure of the quantity of plaque. The plaque type was fatty, fibrous, mixed, and calcified plaque. We calculated total and luminal diameter of SB in the ostial site of SB. The total SB diameter was the length from media to opposite media, and the luminal SB diameter was the length from intima to opposite intima. We specified the ratio of SB diameter as the total diameter of SB divided on luminal diameter of SB. We had a good stent size (diameter and length) with the aid of IVUS, and we measured the stent area after stenting to confirm stent apposition and expansion. SB pre dilatation prior to MV stent was left to the decision of the operator.

Results were subjected to the analysis using Statistical Program for Social Science (SPSS) software version 18.0 (SPSS Inc., Chicago, IL). We considered frequency and percentage as the qualitative results. We considered mean ± standard deviation (SD) as the quantitative results. T-test of significance was used when we compared between two means. Chi-square (X2) test of significance was used when we compared the ratio between two qualitative parameters.  To classify the factors which predicted the occlusion of SB after MV stenting, we used univariate and multivariate logistic-regression analysis. To evaluate the cut-off value, sensitivity and specificity of predictors of occlusion of the SB after stenting of MV, the receiver operating characteristics (ROC) curve was used. P value ≤ 0.05 indicated that the result was statistically significant

RESULTS

Table 1: Comparison between the demographic data and risk factors among the study groups

The patients in this study divided into two groups according to the occlusion of SB after MV stenting into SB occluded group which represented 22.5% of the patients  (n=18)  and non SB occluded group which represented 77.5% of the patients  (n=62). In non SB occluded group, males represented 74.2% (n=46) and mean age was 55.48 ± 7.26. In SB occluded group males represented 83.3% (n=15) and mean age was 56.00 ± 7.30. Demographic data and risk factors among the study groups were presented in table1.

Table 2: Univariate and multivariate logistic regression analysis to the predictors of SB occlusion

As regard demographic data, risk factors, laboratory investigations, ECG changes and PCI data, no statistically significant difference was found between the study groups as p-values were more than 0.05. As regard IVUS measurements, the thinner plaque of MV at junction position with SB, MV plaque area and diameter ratio of SB were the factors which could predict acute occlusion of SB after provisional stenting by the aid of multivariate logistic regression analysis, as statistically significant difference was found between the study groups as p-values were 0.001, 0.003 and 0.034 respectively (table2).

Fig.1: ROC curve for predictors of SB occluded group

Receiver Operating Characteristic (ROC) Analysis showed that 85% was the accuracy  of thinner MV plaque at junction position with SB by 77.7% sensitivity and 88.7% specificity, at cut off predictive value of occlusion of the SB after provisional stenting