New Syntax Tool Gauges Completeness of Revascularization, Predicts Prognosis

A novel Syntax score-based tool for quantifying the proportion of coronary artery disease (CAD) successfully treated by percutaneous coronary intervention (PCI) may help operators know whether the degree of revascularization achieved is “reasonable” and how it is likely to affect prognosis, suggests a paper published online October 14, 2014, ahead of print in EuroIntervention. However, the metric, called the Syntax Revascularization Index (SRI), is less accurate at predicting 1-year mortality than the residual Syntax score.

Methods
To develop the SRI and determine an acceptable prognostic threshold, Philippe Généreux, MD, of Columbia University Medical Center (New York, NY), and colleagues looked at a subset of 2,618 patients with moderate or high-risk NSTE-ACS from the ACUITY trial who underwent PCI and had quantitative coronary angiography (QCA) performed by experienced core lab technicians. 

Median Syntax score decreased from 9 at baseline to 1 after PCI. Thus, the median SRI—which is based on a formula involving both the baseline and residual Syntax scores—was 85%. Stratified into 3 levels, SRI was:

  • 100% in 1,079 patients (41.2%)
  • 50-99% in 907 patients (34.6%)
  • < 50% in 632 patients (24.1%) 

Outcomes Improve as SRI Increases

At 1-year, MACE (death, MI, and unplanned revascularization for ischemia) and the component endpoints were lowest in the group with complete revascularization and highest in the group with SRI < 50%, with a similar trend for definite/probable stent thrombosis (table 1).

Table 1. One-Year Outcomes by SRI

On multivariable analysis, lower SRI independently predicted 1-year mortality (HR 2.17; 95% CI 1.05-4.35), as did insulin-treated diabetes (HR 3.92; 95% CI 2.17-7.06) and age (per 10-year increment; HR 1.48; 95% CI 1.13-1.94).

ROC curve analysis demonstrated an association between SRI and 1-year mortality, with an SRI cutoff of 80% yielding the best prognostic accuracy (AUC 0.60; 95% CI 0.53-0.67). The SRI exhibited slightly better sensitivity compared with the residual and baseline Syntax scores, but the residual Syntax score—especially when > 8—had the best specificity and accuracy for 1-year mortality compared with the other scores (table 2).

Table 2. Capability of Syntax Scores to Predict 1-Year Mortality

The predictive capability of an SRI < 80% for 1-year mortality was consistent across all subgroups examined except for sex, where it showed an association in men but not women (HR 3.03 vs 0.97; P for interaction = .03).

Patients with lower SRI tended to be older and had a higher prevalence of diabetes, hyperlipidemia, and hypertension. They also were more likely to have a history of prior MI and reduced baseline hemoglobin levels and creatinine clearance. Angiographically, patients with lower SRI had more multivessel disease, a greater number of lesions, and more extensive disease. They were also more likely to have baseline TIMI 0/1 flow, collaterals, and lesions with severe calcification or thrombus. Thienopyridines were less frequently used in the lowest SRI group at discharge and at 30 days but not at 1 year.

According to the authors, baseline Syntax score, residual Syntax score, and SRI “have different meanings and roles during the patient assessment and clinical decision-making process, and therefore each may have utility in practice and during clinical trials.”

The baseline Syntax score can be used to predict patient outcomes prior to revascularization and help inform the choice of PCI vs CABG for individual patients, they say, while the residual Syntax score and SRI “not only have postprocedural prognostic utility but can also serve as a guide for clinical decision making, depending on the expected degree of revascularization. Unless at least a reasonable and appropriate level of revascularization can be achieved, CABG may be a better alternative to PCI.”

SRI Drawbacks Highlighted

Given the generally low Syntax scores of the ACUITY cohort, the SRI “concept will have to be tested in a much more robust group of multivessel patients before it can become a useful clinical tool,” said Jeffrey W. Moses, MD, of NewYork-Presbyterian Hospital/Columbia University Medical Center (New York, NY).

In a telephone interview with TCTMD, he noted that while assessing the percentage of ischemia resolved by PCI embodied in the SRI is an interesting idea, it obscures the importance of the amount of baseline ischemia. For example, revascularizing a high percentage of CAD may have little clinical relevance if the patient’s disease burden was low to begin with, he explained.

On the other hand, he added, “if you started with a Syntax score of 45% and left behind 10%, that would give you an SRI of about 80%. But that 10% residual score bespeaks a lot of ischemia. That’s why the residual Syntax score stands up better than the SRI.”

On the positive side, while the usual emphasis on baseline Syntax score for risk stratification and treatment choice “assumes that all PCI is the same,” Dr. Moses said, this research shows that “what matters is [the effectiveness of] the individual procedure.”

CTOs are a common reason for incomplete revascularization, observed Emmanouil S. Brilakis, MD, PhD, of the VA North Texas Health Care System (Dallas, TX), in a telephone interview with TCTMD. Except in skilled centers, success in treating these lesions hovers around 60% across the United States, although that number is likely to improve with adoption of novel technologies and techniques and more training, he said.

In addition, Dr. Brilakis expressed concern about the proliferation of scores. Although the usefulness of the basic Syntax score in guiding treatment choice is fairly well established, he commented, “having to calculate a score before the procedure and again afterward on clinical grounds might be challenging in practice.” However, if the input of QCA data and calculation of scores could be automated, that would go a long way toward making scoring less burdensome, he added.

Note: Dr. Généreux and several coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

  


Source: 
Généreux P, Campos CM, Yadav M, et al. Reasonable incomplete revascularization after percutaneous coronary intervention: the SYNTAX Revascularization Index. EuroIntervention. 2014;Epub ahead of print.

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New Syntax Tool Gauges Completeness of Revascularization, Predicts Prognosis

Disclosures
  • Dr.Généreux reports receiving speaker’s fees from Abbott Vascular and Cardiovascular Systems and serving as a consultant for Cardiovascular Systems.
  • Dr. Brilakis reports receiving consulting or speaker fees from Abbott Vascular, Asahi, Boston Scientific, St. Jude Medical, and Terumo.
  • Dr. Moses reports serving as a consultant for Abbott Vascular and Boston Scientific.

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