Coronary bifurcations are frequent and account for approximately 20% of all percutaneous coronary interventions [1]. Nonetheless,they represent one of the remaining challenges in interventional cardiology and the uniform strategy is still the subject of substantial debate in terms of a lower procedural success rate,a higher risk of procedural complications, and increasing rates of long-term adverse cardiac events [2].

During stent implantation, provisional stenting (PS) was often performed, where a conventional guide wire was inserted to the side branch (SB) before implanting stent to the main vessel (MV), if it wasn’t effective, then the SB could be treated. It has been widely accepted as the gold standard for its lower risks of major adverse cardiac events (MADEs), death, myocardial infarction (MI), and target vessel revascularization (TVR) in the majority of bifurcation lesions [3‐11].

Whereas, simple strategy may shift the carina to the SB and induce a stenosis after stenting of MV. Major SB occlusion after MV stenting is one of the most serious complications closely associated with cardiac death and MI, and it may be the major reason why operators prefer more aggressive strategy in the bifurcation lesions [12‐15]. Therefore, to prevent from carina displacement—the basic mechanism of side branch compromise during bifurcation percutaneous coronary intervention, several novel stenting systems for bifurcation lesions have been developed [16, 17].

The main purpose of this study was to perform a novel SB protection technique called Modified balloon-stent kissing technique (M-BSKT), which was based on balloon-stent kissing technique that was first proposed by Jin Z [18]. Routine usage of proximal optimizing technique (POT) after rewiring could make the malapposition in the stented MV segment completely corrected while maintaining perfect arterial circularity and achieving effective modification of physiological anatomy [19]. With this improvement, we modified balloon-stent kissing technique and discussed the advantage compared to other SB protection techniques such as PS.

The present study focus on clinical outcomes between M-BSKT and PS techniques for simple true bifurcation lesions stratified the criteria. The principal findings in this study are as follows: 1) In general, M-BSKT was similar to PS in every aspects except the damage of SB and the rate of FKBI application. 2) In ACS patients, performing M-BSKT was a significant factor to protect SB, especially in preventing the deterioration of TIMI flow and reducing the application of FKBI.

Although the ESC guidelines strongly recommends provisional SB stenting taking into consideration not only immediate but also long-term results of this strategy [22], abrupt closure of the SB may occur after MV stent implantation [12‐14]. Meanwhile, SB occlusion occurred more frequently in patients with true bifurcation lesions than in those with non-true bifurcation lesions [23]. In the present clinical trial, the final outcomes of provisional stenting of bifurcation lesions were not associated with significant improvement [15, 24]. In our study, we compared the safety and efficacy of PS and M-BSKT during the treatment of some especial bifurcation lesions. It adopted the criteria of true bifurcation lesions and eliminated the complex bifurcation lesions established by Chen [20]. Based on previous researches, we eliminated complex bifurcation lesions that may get the maximum benefit from 2-stent techniques. Since a proportion of patients with a severe big SB lesions (simple true bifurcation lesions) would remain ischemic after MV stenting, the jailed SB wire or balloon facilitated rewiring of the SB by widening the angle between the MV and SB and prevented SB occlusion. This experiment using SB ostial pinching≥90% by angiography as an indication for SB intervention reduced the unnecessary intervention of SB in the maximum limit. Meanwhile, a bailout stent in side branch was implanted only in case of dissection or significant flow impairment after FKBI.

The construction of the classical stent did not take into consideration vessel tapering in bifurcation lesions and resulted in carina and plaque shift—the main mechanisms of SB compromise [15]. However, the M-BSKT consists of leaving a dilated balloon in SB while implanting a stent in the MV. It impacts less on the bifurcation segment by means of limiting carina and plaque shift towards to SB, which are two major factors responsible for SB compromise [18]. Yohei Numasawa [17] evaluated the configuration of true bifurcation lesion after stent implantation using the jailed balloon technique by three-dimensional optical frequency domain imaging (OFDI) which provided clearer and higher resolution images. It was already indicated clearly that there were no signs of plaque or carina shift into the SB. However, there was little data to support the advantage of this technique. In this case, we clustered data from 2 groups about the SB ostial deteriorations and found out all deteriorations were slightly less when applying M-BSKT than PS. The advantage of M-BSKT that balloon inflated between the time from the stent located to inflated could protect SB more effective in theory.

Based on the date and trends we observed, the implementation of M-BSKT had no significant differences regarding to SB protection in the 2 study groups, but a trend towards superior clinical results in patients treated with M-BSKT. So the propensity score matching was used to identify the diversity between the 2 techniques. Baseline features were well balanced among M-BSKT patients versus PS patients. We noted the difference in immediate procedural and clinical outcomes between the 2 groups in the matched cohort. When propensity score matching was adopted, the effect of SB protection revealed the superior technical advantages of M-BSKT comparing with PS. As a result, the rate of SB flow deterioration and dissection after MV stenting at once was higher in PS. Because of cardiac death or myocardial infarction occurred more frequently in patients with SB occlusion [14], it is conceivable to infer that the inflated balloon of the SB provides a high degree of SB protection in immediate procedural.

According to research results available, jailed wire in SB was associated with the recovery of the occluded SB [14]. What’s more, it indicated that M-BSKT used as a rescue procedure to keep the SB open was superior to PS on the basis of technological advantages, once the branch was occluded. This led to significantly reduced proximal deformation with related malapposed struts and reduced rate of SB ostial stenosis. Jailed balloon in SB could be inflated and FKBI could be applied, as long as the damage of SB flow happened accidentally. In some respect, MB restenosis was higher in the routine FKBI group due to the potential distortion of the MB stent strut [25]. On this premise, it is recommended to avoid deploying FKBI technique. The hypothesis that M-BSKT could decrease the proportion of FKBI implement during operation was justified in this study.

Interestingly, when we conducted subgroup analysis of patients with acute coronary syndrome, the advantages of M-BSKT were showed prominently. It just made a clarity conclusion that M-BSKT may provide more protection of SB. Patients with ACS are likely to have multiple vulnerable plaques that are liable to rupture or shift [26, 27]. According to ACS patients with special bifurcation lesions, M-BSKT may limit thrombosis and plaque shift towards to SB more effectively, which avoid the impact on TIMI flow and reduce the application of FKBI.

As we all know, POT consists of an inflating balloon to the MV reference diameter which makes the malapposition in the stented MV segment completely corrected while maintaining perfect arterial circularity [19]. Though high rates of restenosis and stent thrombosis were still often observed after stenting, POT would provide potential benefits such as partially reducing malapposition and achieving effective modification of physiological anatomy [19, 28]. In this study, POT was used as a favourable step to modify BSKT in order to reduce severe coronary flow problems.

Irrespective of propensity score matching, the findings of 1 year clinical follow-up were similar between the 2 techniques. However, wether M-BSKT will play a safe and effective role for a longer period of time is still unknown. Evaluation of long clinical outcomes of two stent percutaneous intervention strategy for treatment of coronary bifurcation lesions offered advantage over PS, simultaneously [11]. Therefore, with our present data, M-BSKT elicited more advantages than PS applied to simple true bifurcation lesions in the operation procedure.

The first and foremost limitation of this study was that it did not involve a significant population. Also, visual estimation of the diameters was used in this study to dedicate bifurcations, rather than quantitative coronary measurement. It may be not precise for the selection of clinically relevant SB. Previous studies suggested that angiographic visual assessment of jailed SB lesions tended to overestimate the severity of jailed SB lesions compared to functional assessment by FFR. Regrettably, there was no application of FFR in this study. Differences in the angiographic assessment of SB lesion severity can affect the treatment strategy for bifurcation lesions. This manuscript used SB ostial pinching≥90% by angiography as indication for SB intervention that was reduced the unnecessary intervention of SB in the maximum limit. Of note, there was a discrepancy between the assessment of the ischemia-inducibility and plan-to-treat. These variable and discrepant values might have influenced the differences of SB intervention between two groups. Although bifurcation angle was regarded as one of the important factors for bifurcation PCI, we excluded it from the scope of criteria, which may influence the SB-occlusion rate. In addition, fractional flow reserve for evaluating the significance of SB ostial lesions wasn't used before and after the procedure. Because randomization may interfere with the chosen of different bifurcations, the simple true bifurcations of the right coronary artery were rarely contained in our study.

We demonstrated that, for patients with coronary simple true bifurcation lesions, M-BSKT provides preferable outcomes comparing with the PS after propensity score matching. Because of the existence of vulnerable plaques in ACS patients exist, the advantages of M-BSKT were showed prominently. Our case reported that it appeared to be a reasonable and suitable strategy to reduce the deterioration of SB and the application of FKBI when MV stent was inflated during the operation. Although M-BSKT has been performed, its long-term impact on patients' outcomes cannot be ascertained based on current studies and requires further investigation on the correlation between BSKT and clinical outcomes.