Journal of Invasive Cardiology

An interesting feature is the poor performance of SYNTAX score in stratifying risk among the low and intermediate tertiles. In fact, the rates of cardiovascular death were 8.1%, 4.9%, and 30% in patients with low, intermediate, and high SYNTAX scores, respectively, and the rates of MACE were 21.6% in the first tertile, 10.4% in the second tertile, and 42.5% in the third tertile. As described in the Methods section, the SYNTAX score tertiles in this study are different from those in the SYNTAX trial in order to achieve an equilibrium between the groups, as the intermediate score group would be much smaller. However, had the SYNTAX trial tertiles been used, the absolute frequency of mortality and MACE within the groups would have been exactly the same and even though the relative frequencies would have changed, we would still observe the poor risk stratification performance among the low and intermediate tertiles. Such a finding is in agreement not only with the study by Valgimigli et al,⁹ which evaluated this score in multivessel coronary disease, but also with Capodano et al,¹¹ who tested SYNTAX score in left main angioplasty. Our study supports the suggestion by those authors of dichotomizing the score in order to achieve better results. In our case, the optimal cut-off values for mortality and MACE are 32.5 and 28, respectively.

The results of our study demonstrate the usefulness of SYNTAX score in predicting adverse outcomes in this population, but it raises some important questions that suggest caution in using it alone to choose the most appropriate revascularization strategy in each case. In fact, it only takes into account the anatomy, extension, and complexity of coronary artery disease and does not incorporate clinical and procedural factors. This is probably the most important factor that might limit the applicability of SYNTAX score as a tool to indicate angioplasty of left main disease. Indeed, variables such as age, heart failure, or kidney insufficiency have demonstrated their role in outcomes after PCI in previous risk models.^12,13 Some authors have addressed this important subject, showing that risk scores that merge clinical and angiographic variables (Global Risk Classification System)¹⁴ or even with the addition of procedure characteristics (NERS score)¹⁵ have a better predictive ability in ULMCA disease than the SYNTAX score alone.

The population of this study shows many similarities with other contemporary left main revascularization studies. The RESEARCH and T-SEARCH¹⁶ registries, for example, have a similar age and male gender prevalence, but a lower burden of diabetes and hypertension. Presentation as acute coronary syndrome and cardiogenic shock is higher in those registries than in ours. On the other hand, the group that compared NERS and SYNTAX score had a younger population, a similar burden of cardiovascular risk factors and prevalence of men, but a lower rate of acute coronary syndrome at presentation.¹⁵ Albeit differences and similarities, there are features that make this population unique and that fact has to be taken into account when interpreting these results.