Adding FFR to Syntax Score Improves Predictive Ability

Download this article's Factoid (PDF & PPT for Gold Subscribers)

NEW YORK—Incorporating fractional flow reserve (FFR) measurements into the Syntax score may help clinicians improve risk stratification and predict 1-year adverse outcomes for patients with multivessel disease, according to findings presented February 14, 2011, at the Left Main Coronary Interventions Course.

William F. Fearon, MD, of Stanford University Medical Center (Stanford, CA), described the approach, which he dubbed the Functional Syntax score.

“Because the [original Syntax score] is angiography-based, it is inherently limited by the accuracy of the coronary angiogram,” which cannot pinpoint ischemia-producing lesions, he said.

FFR, on the other hand, can determine the functional significance of individual lesions. Dr. Fearon cited results from the FAME (Fractional Flow Reserve versus Angiography for Guiding PCI in Patients with Multivessel Evaluation) trial, which showed that patients with multivessel disease who undergo PCI guided by FFR as well as angiography have better outcomes than those treated under angiographic guidance alone.

Function + Complexity

For the current analysis, Dr. Fearon and colleagues looked at 497 patients from the FFR-guided arm of FAME. The Syntax score was first calculated in the usual fashion, then it was recalculated only considering lesions with FFR < 0.80. This process reclassified many patients from higher-risk to lower-risk categories, increasing the proportion eligible for PCI. Over 30% of patients with a Syntax score greater than 22 (indicating more complex CAD) moved to a Functional Syntax score below that cutoff.

The newer metric also was more adept at risk stratifying patients, showing increased rates of 1-year death/MI and MACE in those with the highest scores (tables 1 and 2).

Table 1. Cumulative 1-Year Death/MI Rate According to Risk Score Tertile

^a For lowest vs. highest tertile.

Table 2. Cumulative 1-Year MACE Rate According to Risk Score Tertile

^a For lowest vs. highest tertile.

Moreover, inter- and intra-observer variability was lower for the Functional Syntax score than for the conventional Syntax score, Dr. Fearon reported, adding that this was primarily due to the fact that fewer lesions needed to be accounted for and therefore there was less room for disagreement.

Dr. Fearon noted several caveats to the current study. To begin with, it was a retrospective subanalysis and limited to 1-year outcomes. In addition, the FAME population was lower risk than the SYNTAX trial, from which the Syntax score was derived, and did not include patients with left main disease. The Functional Syntax score itself may be handicapped by not taking clinical characteristics into account, he added.

Despite these issues, Dr. Fearon said, “I think we can conclude that by incorporating FFR into the Syntax score to calculate a Functional Syntax score, a significant number of patients are shifted from high- and medium-risk Syntax scores to lower-risk groups. And the Functional Syntax score was a strong predictor of 1-year outcomes after PCI in patients with multivessel coronary disease.”

Does Left Main Complicate FFR?

Session moderator Martin B. Leon, MD, of Columbia University Medical Center (New York, NY), expressed some reservations, however.

“FAME was an amazing trial, but it’s a little bit impractical to FFR every lesion, particularly when we’re dealing with critical left mains and downstream lesions, and false negatives, false positives. In a left main population, it’s still difficult for me to understand how best to integrate FFR when planning a strategy,” he said, questioning whether FFR should only be performed in downstream lesions with 40% to 70% stenosis or if it should be done in the left main as well. “It does add a lot of time and complexity when you start integrating it into every aspect of the procedure.”

Dr. Fearon replied that there was a role for the left main during FFR assessment. “Practically speaking, one decision is: Does the patient need revascularization or not? And in that setting, FFR is helpful because you can put [the guidewire] down the distal two-thirds of the LAD and measure it,” he said. “If the FFR is abnormal, then clearly the patient needs revascularization. Now as far as determining whether that’s due to LAD disease or the left main alone, it gets a little more complicated, . . . but doing a slow pullback can give you some information about the contribution of LAD vs. left main disease.” Dr. Fearon added that putting the pressure wire down the circumflex, if it is not diseased, can also provide knowledge about the left main.

Importantly, he pointed out, the FFR cutoff of 0.80 still applies in left main disease and can help determine when intervention can be deferred.

“The fundamental issue here,” said Dr. Leon, “is that it is to our advantage as interventionalists to treat fewer lesions by using the better discriminating power of FFR in these visually borderline lesions.” This strength of FFR is already being recognized by clinicians, he noted.

Speaking about larger issues related to imaging technology, Patrick W. Serruys, MD, PhD, of Erasmus Medical Center (Rotterdam, The Netherlands), commented that, “the debate is not about anatomy [vs.] function. The debate is about visual assessment of anatomy vs. an objective assessment of anatomy.”

If optimized, anatomical assessment could be used to predict the flow gradient, he said, “but as soon as you have poor assessment of something, [it’s] garbage in, garbage out.” Dr. Serruys praised the company Heartflow (Redwood City, CA), which is working on ways improve the diagnostic accuracy of noninvasive cardiovascular imaging. According to ClinicalTrials.gov, the company is currently conducting a prospective, multicenter trial to determine whether a new method of computed tomographic angiography can measure the hemodynamic significance of lesions.

 

---

Source:
Fearon WF. Functional Syntax score. Presented at: Left Main Coronary Interventions Course; February 14, 2011; New York, NY.

 

 

Related Stories:

• The Syntax Score: Can Learning Curves and Old Habits Be Overcome?
• SYNTAX Scoring Predicts Outcomes in Unprotected Left Main Patients Undergoing PCI
• FFR Beats Angiography in Guiding Left Main Disease Treatment