Predictors and 3‐year outcomes of compromised left circumflex coronary artery after left main crossover stenting

Abstract Background There are few predictors of decreased fractional flow reserve (FFR) in the left circumflex coronary artery (LCx) after left main (LM) crossover stenting. Objectives We aimed to determine the predictors for low FFR at LCx and possible treatment strategies for compromised LCx, together with their long‐term outcomes. Methods Altogether, 563 patients who met the inclusion criteria were admitted to our hospital from February 2015 to November 2020 with significant distal LM bifurcation lesions. They underwent single‐stent crossover percutaneous coronary intervention (PCI) under intravascular ultrasound (IVUS) guidance with further LCx intervention based on the measured FFR. Results The patients showed significant angiographic LCx ostial affection post‐LM stenting, but only 116 (20.6%) patients had FFR < 0.8. The three‐year composite major adverse cardiac events (MACE) rates were comparable between the high and low FFR groups (16.8% vs. 15.5; p = 0.744). In a multivariate analysis, low FFR at the LCx was associated with post‐stenting minimal luminal area (MLA) of LCx (odds ratio [OR]: 0.032, p < .001), post‐stenting LCx plaque burden (OR: 1.166, p < .001), poststenting LM MLA (OR: 0.821, p = .038), and prestenting LCx MLA (OR: 0.371, p = .044). In the low FFR group, those with compromised LCx managed with drug‐eluting balloon had the lowest three‐year MACE rate (8.1%), as compared to either those undergoing kissing balloon inflation (KBI) (17.5%) or stenting (20.5%) (p = 0.299). Conclusion Unnecessary LCx interventions can be avoided with FFR‐guided LCx intervention. Poststenting MLA and plaque burden of the LCx, and main vessel stent length are poststenting predictors of low FFR.


| INTRODUCTION
Despite considerable improvements in percutaneous coronary intervention (PCI) techniques and pharmacotherapeutics, distal left main (LM) coronary artery lesions continue to be one of the most difficult interventional cardiology objectives. 1 The single-stent strategy is superior to the two-stent approach, and is regarded as the treatment of choice whenever feasible for LM bifurcation lesions, 2 even though the predictors, functional significance, and luminal changes for compromised side-branch ostium after main vessel (MV) stenting have a large degree of divergence. 3 Previous studies have indicated that plaque or carina shift are the two main mechanisms for compromised left circumflex coronary artery (LCx) after LM to left anterior descending (LAD) artery stenting. 4 Coronary angiography is the most used method to measure the extent of atherosclerotic disease and evaluate the geometric changes associated with stent implantation; however, the discordance between anatomic stenosis as evaluated by angiography or intravascular ultrasound (IVUS), and the functional significance of the jailed LCx is not well known. 5,6 Fractional flow reserve (FFR)guided LCx interventions have been proposed to improve clinical outcomes by reducing unnecessary procedures. 7 FFR-guided LCx intervention may be technically difficult, and its superiority over angiography-guided provisional LCx intervention is still questionable. 8,9 Thus, we aimed to provide IVUS-guided predictors for low FFR at LCx after LM to LAD crossover stenting, and to compare the different treatment strategies for compromised LCx and their longterm outcomes.

| PCI procedure
Angiographic and PCI procedures were performed using transradial or trans-femoral approaches, and all operations were performed using approved interventional techniques. 10 All patients received an aspirin loading dose of 300-mg P2Y12 inhibitors (clopidogrel loading dose: 300-600 mg; ticagrelor loading dose: 180 mg) prior to PCIs. All patients were administered an intravenous bolus of 100-IU/kg heparin preprocedure, and the dosage was

| FFR measurements
The FFR was measured at jailed LCx with angiographic stenosis >50%, immediately after the LM to LAD crossover stenting, by using a 0.014-inch pressure guide wire (Radi Medical Systems, Uppsala, Sweden; or Pressure Wire Certus, St. Jude Medical, St. Paul, AK, USA), passing through the distal struts of the stent, and placed 10-12 mm beyond the LCX ostium without any prior balloon inflation at the LCX ostium. The sensor guide wire was positioned at the tip of the guiding catheter to adjust the pressure. FFR measurements were then taken in patients following intracoronary bolus administration of adenosine (150-200 μg) or continuous intravenous (IV) infusion of 120-240-μg/ kg/min adenosine. LCx was considered functionally stenosed in patients with FFR < 0.8. 14 The IVUS assessment data of the patients with FFR < 0.8 group were compared, and they were further classified into three subgroups according to the additional interventions received: KBI, DEB, and stenting (placement of a second stent).

| Definitions and study endpoints
The primary endpoints and clinical outcomes of the current study were the 3-year MACE incidence. Unless a definite non-cardiac cause was reported, all deaths were assumed to be cardiac deaths.  There were no significant differences in the other IVUS-measured parameters between the two groups.

| Clinical follow-up
The three-year clinical outcomes of the two groups are shown in Table 3 and Figure 1.

| DISCUSSION
The results of the current study consist of three core findings: (1)   Additionally, increased stent length was used to cover diffuse atherosclerotic disease, which contains a large PB, and the associated pre and postdilation will cause increased plaque shift to LCx and more flow reduction. 24,25 An increased stent/artery ratio was also found to accentuate plaque shifting to the SB. 26 In the current study, increased total deployed MV stent length was significantly associated with decreased poststenting FFR in LCx in the univariate analysis, but it did not appear to be an independent predictor in the regression analysis.