The SYNTAX score should not be used to choose between CABG and PCI in diabetic patients with multivessel disease

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Michael Farkouh

A post-hoc analysis of FREEDOM (Future revascularisation evaluation in patients with diabetes mellitus: optimal management of multivessel disease) indicates that coronary artery bypass grafting (CABG) provides better outcomes—in terms of major adverse cardiac and cerebrovascular events (MACCE)—for diabetic patients with multivessel disease than does percutaneous coronary intervention (PCI) irrespective of a patient’s SYNTAX score. This suggests that, in this context, the SYNTAX should not be used to predict whether patients would have equivalent outcomes if they underwent PCI rather than CABG.

Writing in the Journal of the American College of Cardiology, Rodrigo B Esper (Heart Institute of São Paulo Medical School, São Paulo, Brazil) and colleagues comment that the FREEDOM trial and other studies have “definitively shown” that CABG improves outcomes compared with PCI in diabetic patients with multivessel disease. They add that the SYNTAX score can be used to determine lesion complexity in patients with multivessel disease and help predict which patients would have equivalent outcomes with PCI as they would have with CABG (i.e. those with lesser lesion complexity). However, the authors comment that “the value of the SYNTAX score has not been assessed specifically in a population limited to patients with diabetes and multivessel coronary artery disease”.

Therefore, in the present study, they reviewed the prognostic implications of the SYNTAX score in diabetic patients with multivessel coronary artery disease who underwent PCI or who underwent CABG in the FREEDOM trial. The primary endpoint was the rate of MACCE, which comprised of all-cause death, non-fatal myocardial infarction, non-fatal stroke, and need for repeat revascularisation. Esper et al also reviewed the rate of hard cardiovascular events (all-cause death, non-fatal myocardial infarction, and non-fatal stroke).

Of 1,900 patients in the study, 953 underwent PCI and 947 underwent CABG. The mean SYNTAX score of these groups was 26.2±8.4 and 26.1±8.8, respectively (p=0.67). Among patients who underwent PCI, the five-year rate of MACCE was significant different among categories of SYNTAX score (i.e. the higher the SYNTAX score, the higher the rate of MACCE). However, there was no such difference between SYNTAX score categories among patients who underwent CABG.

Esper et al report that for the PCI group, the SYNTAX score was an independent risk factor for MACCE and hard cardiovascular events at five years but note “the area under the ROC curve showed a poor discrimination capability for MACCE (0.54) and hard cardiovascular events (0.56).” They add that the score was not an independent predictor of MACCE or hard cardiovascular events in the CABG group.

For all categories of SYNTAX score, the rate of MACCE was higher for patients who underwent PCI vs. those who underwent CABG. For example, for patients with a low score, it was 36.6% vs. 25.9%, respectively (p=0.02). According to the authors, this demonstrates that the “SYNTAX score does not identify a population of diabetes patients with multivessel disease in whom PCI is equivalent or superior to CABG”. They state that unlike the findings of the SYNTAX study, the results of this study suggest “the SYNTAX should not guide decision-making in diabetic patients with multivessel disease”.

There was no significant difference in the rate of hard cardiovascular events between PCI and CABG patients with low and high SYNTAX scores—potentially of suggesting the SYNTAX score could be used to predict which patients would have an equivalent risk hard cardiovascular events if they underwent PCI rather than CABG. However, Esper et al comment: “These results should be interpreted with caution because the study is underpowered to make comparisons between subgroups.”

The authors state their findings “highlight the importance of anatomic and clinical evaluation of diabetic patients with coronary artery disease”. “The decision-making of the best strategy for revascularisation should consider not only coronary angiographic aspects but also clinical aspects that could influence the outcomes,” they add. Co-primary author, Michael Farkouh (Peter Munk Cardiac Centre, University of Toronto) emphasises: “The need for a full clinical assessment of the diabetic patient with multivessel coronary disease as a foundation to deciding how to manage the patient. Patient age, renal function and, of course, patient preference are key determinants in decision making but not the SYNTAX score.”

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