Introduction:
In this study, we aimed to distinguish differences in the procedural complication rate in a group of patients undergoing percutaneous coronary interventions (PCI) of the left main coronary artery (LMCA) between patients with isolated LMCA disease and multi-vessel disease (MVD) with LMCA involvement and to identify their predictors.

Material and methods:
We assessed 221,187 patients from the Polish Cardiovascular Intervention Society national registry (ORPKI) regarding all PCI procedures performed in Poland in 2015 and 2016. We extracted data of 1,819 patients with isolated LMCA disease and 3,718 patients with MVD and LMCA involvement. We compared those two groups in terms of procedural complications and their predictors.

Results:
The overall rate of procedural complications was significantly higher in patients treated with LMCA PCI both in the group of patients with isolated LMCA (6.5%) and the group with MVD with LMCA involvement (7.3%) compared to the non-LMCA PCI group (1.9%, p = 0.002). Multivariate analysis confirmed that MVD with LMCA involvement is an independent predictor of decreased risk of procedural death in the overall group of patients undergoing PCI of the LMCA (odds ratio: 0.583; 95% confidence interval: 0.4–0.848; p = 0.005).

Conclusions:
The MVD involvement in patients treated with PCI of the LMCA may play a protective role. Patients with isolated LMCA involvement undergoing PCI should be subjected to special care and protected by various methods, such as devices to support left ventricle function.