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FFR accurately diagnoses flow-limiting CAD in patients with non-STEMI
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Fractional flow reserve demonstrated high diagnostic accuracy for flow limitation at the lesion level compared with stress perfusion cardiac magnetic resonance at 3 T, according to results of a substudy of the FAMOUS-NSTEMI trial.
The current substudy included 106 patients with non-STEMI who had been referred for early invasive management. Clinicians at two centers measured FFR in all major patent epicardial coronary arteries with estimated visual stenosis of at least 30%, with a repeat FFR measurement in the event that PCI was performed. Stress perfusion cardiac magnetic resonance at 3 T was used to assess myocardial perfusion. A mean duration of 6.1 ± 3.1 days elapsed between FFR assessment and cardiac magnetic resonance.
The mean left ventricular ejection fraction was 58.2 ± 9.1%, mean infarct size was 5.4 ± 7.1% and mean troponin concentration was 5.2 ± 9.2 μg/L.
The researchers evaluated 168 coronary arteries, including 96 infarct-related and 72 noninfarct-related arteries. Thirty-four of the observed perfusion defects were fixed and 160 were inducible. The number of segments with a perfusion abnormality and FFR were significantly and negatively correlated (r = −0.77; P < .0001).
An FFR of 0.8 or less yielded 91.4% sensitivity, 92.2% specificity, 76% positive predictive value and 97% negative predictive value, with a diagnostic accuracy of 92%, the researchers wrote.
The study also included an analysis of 21 patients with non-STEMI who underwent perfusion cardiac magnetic resonance prior to invasive angiography. In these patients, FFR yielded a positive predictive value of 92% and a negative predictive value of 93% for flow-limiting CAD, defined as FFR of 0.8 or lower.
Results of an analysis of receiver operating characteristics suggested an optimal FFR cutoff value of 0.805 or lower for demonstrating reversible ischemia on cardiac magnetic resonance (area under the receiver operating characteristic curve, 0.94; P < .0001).
Findings from an analysis of the infarct-related culprit artery territory in 89 patients indicated a negative correlation between the number of segments with an inducible perfusion abnormality on stress cardiac magnetic resonance and FFR (r = −0.8; P < .001). Restriction of analysis to 59 segments in 66 arteries with occlusive disease maintained this correlation (r = −0.69; P < .0001).
“This is the first study to date to examine the diagnostic accuracy of FFR in a reasonably large cohort of patients with recent non-STEMI vs. a high-fidelity noninvasive reference method,” the researchers concluded. “Our results indicate that FFR and stress perfusion [cardiac magnetic resonance] at 3.0 T were highly concordant and add further evidence for the utility of FFR in this population.” – by Rob Volansky
Disclosure: One researcher reports receiving research grants from and consulting for St. Jude Medical; another researcher reports consulting for St. Jude Medical and Volcano Corporation.
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