Risk Scoring Systems for PCI: Does One Size Fit All?
Predicting outcomes in patients undergoing coronary revascularization has been a topic of long-standing interest. The ACC/AHA (American College of Cardiology/American Heart Association) lesion classification system devised in 1986 and revised in 1990 utilized angiographic variables alone to predict clinical outcomes. Initial studies evaluating the prognostic value of this classification indicated that the early and late outcomes were predicted by the classification.1,2 However, in the age of drug-eluting stents, the prognostic accuracy of this tool has come into question.3 Recent reviews of the utility of the ACC/AHA lesion scoring system seem to indicate that it best predicts outcomes in patients with the most angiographically complex coronary artery disease (CAD).4,5 As percutaneous coronary intervention (PCI) of complex coronary lesions, including left main stenoses, becomes more commonplace, there has been renewed interest in optimizing revascularization outcomes based on risk-stratification scoring tools.
In an effort to delineate an evidence-based approach to coronary revascularization in the population with complex CAD, primarily 3-vessel CAD and unprotected left main disease, the SYNTAX (SYNergy between PCI with TAXUS™ and Cardiac Surgery) investigators developed an angiographically-based model that could aid in determining revascularization strategy (coronary artery bypass grafting [CABG] versus PCI with stenting) as well as predict clinical outcomes.6 This angiographic scoring strategy has been shown to have moderate intraobserver reproducibility. Moreover, when applied to the subgroups of highest complexity (SYNTAX scores > 32), the target population for which the strategy was developed, it predicts increased rates of major adverse cardiac and cerebrovascular events (MACCE).5–8 A retrospective analysis of both the SYNTAX and ARTS II (Arterial Revascularization Therapies Study II) trials demonstrated that among patients with multivessel CAD there were significantly higher rates of MACCE in the highest tertile of SYNTAX scores.6–9 Further, a subgroup post-hoc analysis of the SYNTAX trial has suggested that the patients in the highest tertile of SYNTAX scores benefit from CABG as opposed to PCI with stenting, primarily due to lower rates of target lesion revascularization (TLR).8
Whether a complex angiographic scoring system such as the SYNTAX score would be prognostic for all patients with CAD undergoing PCI is not clear. In this issue of the journal, Brener and colleagues present the results of their study to evaluate the prognostic value of the SYNTAX score in a CAD group of lower complexity.10 This single-center, observational study evaluated the 3-year clinical outcomes of 482 patients with either diabetes mellitus or chronic kidney disease (serum creatinine ≥ 1.5 mg/dL) undergoing nonemergent PCI. They excluded patients with prior PCI, CABG or those presenting with STEMI. Brener et al observed that the SYNTAX score alone was not predictive of mortality or TLR at 3 years. However, their multivariable analysis identified reduced creatinine clearance, ejection fraction and prior myocardial infarction as the strongest predictors of mortality.
The LEADERS (Limus Eluted from A Durable versus ERodable Stent coating) trial also evaluated the SYNTAX score in an all-comers population. Similar to the observations from the post hoc analysis of the SYNTAX trial this post-hoc analysis demonstrated that among the group with the highest SYNTAX scores, defined as a score greater than 16 in this study, there were higher rates of major adverse cardiac events.9 Also, the SYNTAX scores were generally lower than in the SYNTAX or ARTS II trials. However, unlike the results from the Brener study, the discriminatory power for risk assessment using the SYNTAX score was preserved. This suggested that the SYNTAX scoring tool could be extended beyond the multivessel or left main coronary disease population to all patients presenting with obstructive CAD. The reasons for the apparent dichotomous results of these two studies are not clear. One notable difference between the LEADERS trial population and that selected for the Brener study is that patients undergoing emergent PCI as well as those with a prior PCI were included. As such, patients presenting with ST-elevation myocardial infarction (STEMI) were more than a quarter of the highest SYNTAX score tertile in the LEADERS study population. Whether this difference accounts for the contrasting study results remains to be determined.
Although the results of the LEADERS data provided hope for the extrapolation of the SYNTAX score to be predictive of outcomes in an all-comers population, the current study by Brener and colleagues suggests otherwise. The improved prognostic power demonstrated with the consideration of clinical variables in the study by Brener et al suggests that a hybrid scoring system that incorporates angiographic data and clinical variables may have greater discriminatory power than a system based on angiographic criteria alone. Recent evaluation of hybrid scoring systems supports this notion. Scoring systems based on clinical variables have been developed such as the EuroSCORE,11 the Mayo Clinic risk score (MCRS)12 and the ACEF (Age, Creatinine, Ejection Fract13 these take into account objective patient variables to predict short-term mortality after CABG or PCI. They are easy to use and have been shown to be highly reproducible. For example, a Clinical Syntax Score (CSS), the SYNTAX score multiplied by the modified ACEF score (age/ejection fraction +1 for each 10 mL of creatinine clearance 3), demonstrated superior ability to predict 5-year MACCE than either the SYNTAX score or ACEF score alone in a retrospective evaluation of clinical outcomes from a single-center PCI experience.14 Again, the CSS study population had complex CAD (> 2 lesions), and whether their results would hold true when extended to a group with lower angiographic complexity is uncertain.
All clinicians will be forced to both understand and incorporate the use of risk-scoring systems to guide therapy of patients with CAD, including revascularization strategies. The challenge going forward will be to find a system that is user-friendly and of prognostic value. Calculating the SYNTAX score is cumbersome and precludes its daily use for all patients presenting with CAD. Based on the Brener study and others like it, it seems that a more facile and practical risk-stratification model that incorporates angiographic as well as clinical variables may better aid therapeutic decision-making and explanation of periprocedural risks of revascularization in addressing the needs of an all-comers population with CAD. At this point, a one-size scoring system does not appear to be a fit for all.
References
1. Ryan TJ, Bauman WB, Kennedy JW, et al. Guidelines for percutaneous transluminal coronary angioplasty. A report of the American Heart Association/American College of Cardiology Task Force on assessment of diagnostic and therapeutic cardiovascular procedures (Committee on Percutaneous Transluminal Coronary Angioplasty). Circulation 1993;88:2987–3007.
2. Kastrati A, Schomig A, Elezi S, et al. Prognostic value of the modified American College of Cardiology/American Heart Association stenosis morphology classification for long-term angiographic and clinical outcome after coronary stent placement. Circulation 1999;100:1285–1290.
3. Khattab AA, Hamm CW, Senges J, et al. Prognostic value of the modified American College of Cardiology/American Heart Association lesion morphology classification for clinical outcome after sirolimus-eluting stent placement (Results of the prospective multicenter German Cypher Registry). Am J Cardiol 2008;101:477–482.
4. Capodanno D, Di Salvo ME, Cincotta G, et al. Usefulness of the SYNTAX score for predicting clinical outcome after percutaneous coronary intervention of unprotected left main coronary artery disease. Circ Cardiovasc Interv 2009;2:302–308.
5. Valgimigli M, Serruys PW, Tsuchida K, et al. Cyphering the complexity of coronary artery disease using the syntax score to predict clinical outcome in patients with three-vessel lumen obstruction undergoing percutaneous coronary intervention. Am J Cardiol 2007;99:1072–1081.
6. Sianos G, Morel MA, Kappetein AP, et al. The SYNTAX Score: An angiographic tool grading the complexity of coronary artery disease. EuroIntervention 2005;1:219–227.
7. Serruys PW, Onuma Y, Garg S, et al. 5-year clinical outcomes of the ARTS II (Arterial Revascularization Therapies Study II) of the sirolimus-eluting stent in the treatment of patients with multivessel de novo coronary artery lesions. J Am Coll Cardiol 2010;5:1093–1101.
8. Serruys 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;360:961–972.
9. Wykrzykowska JJ, Garg S, Girasis C, et al. Value of the SYNTAX score for risk assessment in the all-comers population of the randomized multicenter LEADERS (Limus Eluted from A Durable versus ERodable Stent coating) trial. J Am Coll Cardiol 2010;56:272–277.
10. Brener SJ, Prasad AJ, Abdula R, Sacchi TJ. The relationship between the angiographically-derived SYNTAX score and outcomes in high-risk patients undergoing percutaneous coronary intervention. J Invasive Cardiol 2011;23:65–68.
11. Nashef SA, Roques F, Michel P, et al. European System for Cardiac Operative Risk Evaluation (EuroSCORE). Cardiothorac Surg 1999;16:9–13.
12. Singh M, Reeder GS, Jacobsen SJ, et al. Scores for post-myocardial infarction risk stratification in the community. Circulation 2002;106:2309–2314.
13. Ranucci M, Castelvecchio S, Menicanti L, et al. Risk of assessing mortality risk in elective cardiac operations: Age, creatinine, ejection fraction, and the law of parsimony. Circulation 2009;119:3053–3061.
14. Garg S, Sarno G, Garcia-Garcia HM, et al. A new tool for the risk stratification of patients with complex coronary artery disease. The Clinical SYNTAX Score. Circ Cardiovasc Interv 2010;3:317–326.
From the Wake Forest University School of Medicine, Winston-Salem, North Carolina. The authors report no conflicts of interest regarding the content herein. Address for correspondence: Robert J. Applegate, MD, FACC, FSCAI, FAHA, Section of Cardiology, Wake Forest University School of Medicine Medical Center Boulevard, Winston-Salem, NC 27157–1045. E-mail: bapplega@wfubmc.edu
