A noninvasive imaging technique combined with fractional flow reserve (FFR) showed the potential to detect functionally significant lesions in patients with multivessel coronary artery disease (CAD), according to a study published June 11 in the Journal of the American College of Cardiology.
Lead author Carlos Collet, MD, and colleagues studied 77 patients from the SYNTAX II study who had three-vessel CAD and were deemed at equivalent risk for coronary artery bypass graft (CABG) surgery and percutaneous coronary intervention (PCI).
Assessing the functionality of stenosis has been shown to improve the prediction for adverse cardiac events, but the feasibility of a noninvasive measure of functional SYNTAX score (FSS) hadn’t previously been investigated in patients with complex CAD, the authors noted.
“Fractional flow reserve derived from computed tomography angiography (FFRCT,) can be used to calculate the noninvasive FSS,” they wrote. “The noninvasive FSS has the potential to individualize risk assessment, assist the heart team in the decision-making process prior to invasive angiography, and guide treatment planning in the noninvasive setting.”
Noninvasive FSS was calculated using only ischemic lesions, meaning an FFRCT of 0.80 or lower.
CT angiography (CTA) was feasible in 86 percent of patients (66 of 77), while the noninvasive FSS was successfully calculated in 80 percent of the patients (53 of 66) who underwent CTA. Most of these failed attempts were due to poor image quality, but the imaging equipment wasn’t uniform across the study or reflective of the most recent technology, the authors noted.
Compared to conventional angiography, CTA overestimated the SYNTAX score, while FFRCT nearly matched conventional angiography (SS of 21.6 versus 21.2). These scores are right on the borderline of whether a patient could be recommended for CABG or PCI based on European and American clinical guidelines, the researchers pointed out.
“In patients with three-vessel CAD and SS less than 22 points, CABG is the preferred strategy, whereas in patients with SS less than 22, both CABG (Class I) and PCI (Class IIb for the American guideline and Class I for the European guideline) can be recommended,” they wrote. “However, refining risk stratification with the FSS can reclassify 25 to 30 percent of patients into a lower-risk category and potentially an alternative revascularization strategy can be offered.”
Noninvasive FFS reclassified 30 percent of patients from the intermediate and high-risk categories to the lower-risk tertile in this study, while invasive FFS reclassified 23 percent of patients in such a manner. Two of the patients reclassified noninvasively to a lower-risk category experienced adverse events.
The authors also evaluated the diagnostic accuracy of FFRCT in terms of its ability to detect functionally significant stenosis, defined as instantaneous wave-free ration (iFR) below 0.89. FFRCT achieved a C-statistic of 0.85, with a sensitivity of 95 percent and a specificity of 61 percent. The positive predictive value was 81 percent and the negative predictive value was 87 percent.
“A refined physiological assessment, the FSS incorporates ischemia to improve discrimination for clinical events and increase reproducibility,” Collet et al. wrote. “Further developments in cardiac computed tomography and FFRCT have the potential to enhance the accuracy and clinical utility of the technology, even for patients with complex coronary disease.”
The researchers acknowledged the study was too small to investigate differences in clinical outcomes. They said an ongoing randomized trial is assessing heart teams’ agreement with either conventional angiography or coronary CTA with FFRCT in making CABG versus PCI decisions. An outcomes-based trial should follow, they suggested.
“Due to the invasive nature and associated costs of SS and FSS, the concept of noninvasive interventional planning is attractive,” wrote the authors of an accompanying editorial. “Moreover, although FFR is considered the current gold standard for guiding coronary revascularization, in real-world practice it is not used for decision making in many patients. Hence, the use of FFRCT, which provides hemodynamic information noninvasively across all locations of the coronary tree, may increase the availability of physiological information for interventional decision-making.”
Despite the limitations of the study, the editorialists said it may indicate an impending shift in the way CAD is assessed.
“The days of having patients entering the catheterization laboratory with nothing more than symptoms and a positive stress test result may be coming to an end,” wrote Bjarne L. Norgaard, MD, PhD, Jonathon Leipsic, MD, and Stephan Achenbach, MD, PhD.
“This study may be signaling a shifting paradigm in which CAD is diagnosed and thoroughly characterized noninvasively, and revascularization planning made in a collaborative fashion integrating the heart team, and a wealth of noninvasive data that will hopefully lead to more effective and cost-efficient revascularization strategies.”