SYNTAX score II – Authors' reply

We welcome the opportunity to expand on how to assess the performance of the SYNTAX score II.1Farooq V van Klaveren D Steyerberg EW et al.Anatomical and clinical characteristics to guide decision making between coronary artery bypass surgery and percutaneous coronary intervention for individual patients: development and validation of SYNTAX score II.Lancet. 2013; 381: 639-650Summary Full Text Full Text PDF PubMed Scopus (662) Google Scholar First, interactions in the SYNTAX score II are central to more personalised decision making—ie, specific anatomical or clinical factors to be more predictive of mortality with percutaneous coronary intervention (PCI) compared with coronary artery bypass graft (CABG) surgery, or vice versa. All variables in the SYNTAX score II were validated, with the exception of age and left ventricular ejection fraction, which might relate to selection bias inherent to all registries. Hence randomised validation was proposed.1Farooq V van Klaveren D Steyerberg EW et al.Anatomical and clinical characteristics to guide decision making between coronary artery bypass surgery and percutaneous coronary intervention for individual patients: development and validation of SYNTAX score II.Lancet. 2013; 381: 639-650Summary Full Text Full Text PDF PubMed Scopus (662) Google Scholar Currently, validation of the SYNTAX score II is prespecified as an endpoint in the ongoing randomised EXCEL trial (NCT01205776), and the planned SYNTAX trial II which will use the SYNTAX score II to recruit patients on the grounds of patient safety. Second, substantial differences in treatment assignment (CABG or PCI) were evident using reclassification analyses—ie, comparisons between the SYNTAX score II and conventional tertiles of the anatomical SYNTAX score.2Serruys PW Morice MC Kappetein AP et al.Percutaneous coronary intervention versus coronary-artery bypass grafting for severe coronary artery disease.N Engl J Med. 2009; 360: 961-972Crossref PubMed Scopus (3465) Google Scholar These were quantified and presented in the manuscript, and cannot be deemed misleading, because they are an accepted and important step in assessing performance.3Steyerberg EW Moons KGM van der Windt DA et al.Prognosis research strategy (PROGRESS) 3: prognostic model research.PLoS Med. 2013; 10: e1001381Crossref PubMed Scopus (883) Google Scholar A further step to quantify effect on survival of the population under study requires a clear decision rule. If we simply select CABG or PCI based on a higher or lower expected survival (Kaplan-Meier analyses) with the SYNTAX score II, irrespective of the margin of difference, 4-year mortality would be 7·5% compared with 8·4% using the anatomical SYNTAX score with existing myocardial revascularisation guidelines4Wijns W Kolh P Danchin N et al.Guidelines on myocardial revascularization: The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS).Eur Heart J. 2010; 31: 2501-2555Crossref PubMed Scopus (26) Google Scholar (equivalent to using the SYNTAX score II in only 111 patients [100/0·9%] to have one more patient alive at 4 years). Similar analyses selecting CABG or PCI based on statistical comparisons of expected survival showed that 4-year mortality remained unaltered at 8·2%. Notably, using either approach to decision making with the SYNTAX score II resulted in a similar 4-year survival (Kaplan-Meier analyses) between CABG and PCI in both the development and validation populations. Additionally, and contrary to current myocardial revascularisation guidelines,4Wijns W Kolh P Danchin N et al.Guidelines on myocardial revascularization: The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS).Eur Heart J. 2010; 31: 2501-2555Crossref PubMed Scopus (26) Google Scholar patients were identified in all tertiles of the anatomical SYNTAX score who would be potentially suitable for CABG, PCI, or both. The choice between CABG and PCI would thus be down to individual patient preference, their perception of short-term and long-term risk, and health economics. We agree that the practical applications of performance statistics are complex, and future work in this evolving field will prove to be of additional value in upcoming validation studies. We declare that we have no conflicts of interest. SYNTAX score IIVasim Farooq and colleagues1 (Feb 23, p 639) developed and validated a new score (SYNTAX II) for the prediction of mortality after coronary artery bypass graft (CABG) and percutaneous coronary intervention (PCI) in patients with complex coronary artery disease. They added clinical characteristics to the anatomical SYNTAX score to improve individualised treatment decisions. They conclude that the new score can better guide the choice between CABG and PCI. It is very valuable that they used the SYNTAX trial not only to compare the treatment groups but also to develop a decision rule to guide treatment choice. Full-Text PDF Anatomical and clinical characteristics to guide decision making between coronary artery bypass surgery and percutaneous coronary intervention for individual patients: development and validation of SYNTAX score IILong-term (4-year) mortality in patients with complex coronary artery disease can be well predicted by a combination of anatomical and clinical factors in SYNTAX score II. SYNTAX score II can better guide decision making between CABG and PCI than the original anatomical SYNTAX score. Full-Text PDF