Validity of SYNTAX score II for risk stratification of percutaneous coronary interventions: A patient-level pooled analysis of 5433 patients enrolled in contemporary coronary stent trials

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Abstract

Objectives

To assess the clinical profile and long-term mortality in SYNTAX score II based strata of patients who received percutaneous coronary interventions (PCI) in contemporary randomized trials.

Background

The SYNTAX score II was developed in the randomized, all-comers' SYNTAX trial population and is composed by 2 anatomical and 6 clinical variables. The interaction of these variables with the treatment provides individual long-term mortality predictions if a patient undergoes coronary artery bypass grafting (CABG) or PCI.

Methods

Patient-level (n = 5433) data from 7 contemporary coronary drug-eluting stent (DES) trials were pooled. The mortality for CABG or PCI was estimated for every patient. The difference in mortality estimates for these two revascularization strategies was used to divide the patients into three groups of theoretical treatment recommendations: PCI, CABG or PCI/CABG (the latter means equipoise between CABG and PCI for long term mortality).

Results

The three groups had marked differences in their baseline characteristics. According to the predicted risk differences, 5115 patients could be treated either by PCI or CABG, 271 should be treated only by PCI and, rarely, CABG (n = 47) was recommended. At 3-year follow-up, according to the SYNTAX score II recommendations, patients recommended for CABG had higher mortality compared to the PCI and PCI/CABG groups (17.4%; 6.1% and 5.3%, respectively; P < 0.01).

Conclusions

The SYNTAX score II demonstrated capability to help in stratifying PCI procedures.

Introduction

The SYNTAX score [1], [2], [3] was developed for the randomized comparison of coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI) in the Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) trial [2]. The SYNTAX score provides objective quantification on the diseased coronary artery segment in terms of its severity, anatomical location and importance in supplying blood to the myocardium. Based on the results of the SYNTAX trial [2], [4], [5] the SYNTAX score has been implemented as a watershed between CABG and PCI in prevailing guidelines [6], [7]. However, the SYNTAX score cannot account for the effect related to clinical factors which are widely acknowledged to impact on long-term outcomes, such as a patients' age, left ventricular ejection fraction, and renal function [8], [9], [10].

Recently, the SYNTAX score II was developed by applying a Cox proportional hazards model to the SYNTAX trial data. A combination of clinical and anatomical predictors [5], [11], together with their interaction with the treatment modality (CABG or PCI), enables estimation of the absolute risk difference between CABG and PCI and has the potential to assist the multidisciplinary decision-making process between these two strategies. The SYNTAX score II has been shown to provide reliable predictions of 4-year mortality for complex coronary artery disease, being externally applied in more than 10,000 patients and implemented in the most recent international guidelines [11], [12], [13], [14].

We aim to assess the stratification by the SYNTAX score II theoretical treatment recommendation in heterogeneous patients treated with PCI. Additionally, we intend to evaluate the predictive performance of the SYNTAX score II in recent randomized trials in different clinical scenarios using different types of stents.

Section snippets

Study population

We pooled 7 contemporary coronary drug-eluting stent (DES) trials for which the independent core lab analysis assessment of SYNTAX scores were available: ARTS II (Arterial Revascularization Therapies Study II) trial, STRATEGY (Single High-Dose Bolus Tirofiban and Sirolimus-Eluting Stent Versus Abciximab and Bare-Metal Stent in Myocardial Infarction) trial, EXCELLA II (Elixir Medical Clinical Evaluation of the Novolimus-Eluting Coronary Stent System) trial, LEADERS (Limus Eluted From a Durable

Results

As shown in Table 1, pooled data from the seven trials contained 5433 patients with a mean age 63.3 ± 10.8 years, 75.3% were male, 21.8% had diabetes mellitus, 56.8% presented acute coronary syndrome and the mean body mass index was 27.52 ± 4.1. The mean creatinine clearance was 92.1 ± 36.2 mg/dl, ejection fraction 56 ± 11.1% and SYNTAX score 14.2 ± 9.1. There were 399 deaths (6.3%) over 3-year follow-up.

Discussion

The data presented in this paper can be summarized as follows: (1) the SYNTAX score II based treatment recommendation for CABG was an uncommon finding in contemporary DES trials and (2) the SYNTAX score II showed clinical relevance through its ability to identify patients at higher risk for PCI.

Limitations

This study has the inherent limitations of a not pre-specified retrospective analysis. As previously discussed, the ultimate objective of the SYNTAX score II is to assist the heart team in the decision-making process between CABG and PCI [22]. Thus true validation of the SYNTAX score II would require a prospective study where the decision between CABG and PCI is done randomly. The present study, being retrospective, cannot assess the treatment recommendation based on the SYNTAX score II for the

Conclusions

The SYNTAX score II demonstrated solid predictive performance and aptness to help in stratifying and prescribing PCI procedures.

Conflict of interest

All authors have no conflict of interest and did not receive grants or financial support from industry or from any other source to prepare this manuscript.

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