Left main coronary intervention: Are we moving too quickly without the appropriate evidence base?

Within the past decade, a large body of evidence has accumulated supporting the potential feasibility, efficacy, and safety of PCI for unprotected left main (ULM) coronary artery (ULMCA) disease [1]. The SYNTAX trial provided randomized evidence to support the potential safety and efficacy of undertaking ULM PCI (compared to CABG) in patients based on anatomical criteria (i.e., SYNTAX Score < 33) [2,3]. Subsequent substudies of the SYNTAX trial have since brought up the tantalizing possibility of potential superiority being achieved with ULM PCI (compared to CABG) in selected patients when anatomical (SYNTAX Score < 33) and clinical factors (additive EuroSCORE < 6) are considered [4]. Further randomized studies have unfortunately lacked sufficient power to draw any clinically directive conclusions [5,6]. The ongoing international multicentre EXCEL (Evaluation of XIENCE Prime versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularisation) trial, aiming to recruit 2,600 patients with ULMCA disease and a SYNTAX Score < 33, will undoubtedly answer these questions. Within this issue of Catheterization and Cardiovascular Interventions, Lee et al. demonstrate the comparability of drug eluting stent implantation versus CABG for ostial ULMCA disease, based on a substudy of the MAIN-COMPARE registry. Notably, no differences in 5-year survival, death/Q-wave MI/stroke, or TVR were evident in the ostial left main group, even after propensity score matching. Certainly, the results appear to support what has long been suspected, the treatment of relatively simple ULMCA disease with PCI has excellent long term outcomes, and may potentially be regarded as similar to the treatment of patients with one or two vessel disease were PCI may be regarded as the gold standard [1]. Several notable factors should, however, be highlighted when interpreting the results of the study by Lee et al. Firstly, the study was significantly underpowered (n 5 263) to draw any firm conclusions, particularly after propensity score matching (n 5 78). Secondly, the SYNTAX Score was not prospectively used to enroll patients, and notably was not available in almost one-quarter of patients (23%)—although advanced imputation methods using clinical variables were undertaken to substitute for the missing SYNTAX Scores, one does question the wisdom of inferring anatomical data from clinical variables, however sophisticated the imputation algorithm is. Furthermore, clinical outcomes in the left main do appear to be predominantly driven by higher SYNTAX Scores and its association with the risk of native coronary disease progression and future coronary events, rather than anatomical characteristics of the left main (although these will no doubt play an important role) [4]. Thirdly, the PCI arm had substantially lower SYNTAX Scores (22.1 2 11.6, i.e., predominantly low-intermediate SYNTAX Scores) compared to the CABG arm (39.3 2 14.9, i.e., predominantly high SYNTAX Scores), were surgery would be expected to be superior [3]. The results of this study by Lee et al., therefore, simply serve to support what is already known in the published literature, with an emphasis on the left main ostium. A word of caution is that undertaking ostial ULMCA disease does require specific technical expertise by suitably trained operators to ensure, for example, appropriate stent positioning and deployment while avoiding geographical miss, ensuring adequate stent expansion (with occasional double stenting) due to the ostium being rich in elastic tissue with a greater chance of acute recoil, and rarer complications, which the operator must be able to deal with [6].