Compared with anatomical stenosis, fractional myocardial mass per fractional flow reserve was able to determine physiological severity of a coronary artery with higher accuracy, according to research published in JACC: Cardiovascular Interventions.

Jin-Ho Choi, MD, PhD, associate professor at the Sungkyunkwan University School of Medicine at the Samsung Medical Center, and colleagues analyzed 724 lesions from 463 patients who underwent coronary computed tomography angiography (CCTA) and invasive coronary angiography with fractional flow reserve measurement. They sought to better understand the discordance between anatomical stenosis and physiological severity.

“Coronary angiography (CAG) is being used as a standard for decision of treatment strategy or revascularization in daily practice,” Dr Choi and colleagues wrote. “However anatomical stenosis visualized by CAG is a poor predicator of physiological severity and frequently underestimates or overestimates physiological severity of stenosis.”


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Fractional flow reserve <0.80—a criteria for vessel-specific physiological stenosis—was identified in 281 vessels. Fractional myocardial mass decreased according to the vessel downstream (P<.001, all) and fractional flow reserve frequency increased proportionally to fractional myocardial mass and inversely to angiographic minimal luminal diameter (P<.001).

Fractional myocardial mass per minimal luminal diameter demonstrated a good correlation with fractional flow reserve in a per-vessel analysis (r=0.61). It was also superior to diameter stenosis for fractional flow reserve <0.80 by receiver operating characteristic and reclassification analysis (c-statistics=0.84 vs 0.74; net reclassification improvement [NRI]=0.63; integrated discrimination improvement[IDI]=0.18; P<.001 for all).

“The optimal cut-off of FMM/MLD [fractional myocardial mass/minimal luminal diameter] was 29 g/mm, with sensitivity=75%, specificity=77%, positive predictive value=68%, negative predictive value=83%, and accuracy=77%,” the authors wrote. “Addition of FMM/MLD to DS [diameter stenosis] could further discriminate vessel with FFR [fractional flow reserve] <0.80 (c-statistic=0.86 vs 0.84; NRI=0.34; IDI=0.03; P<.005, all).”

The per-vessel and per-patient prevalence of vessel with fractional flow reserve <0.80 was 39% and 52%, respectively and in both analyses, vessels with fractional flow reserve <0.80 demonstrated higher diameter stenosis, lower reference diameter, and lower minimal lumen diameter compared to vessels with fractional flow reserve ≥0.80 (P<.001 for all).

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The ratio of fractional myocardial mass to minimal lumen diameter may be a novel anatomical index for physiologically significant stenosis having fractional flow reserve <0.80, according to the researchers.

“Fractional myocardial mass may reduce anatomic-physiological discordance and integrate it with the ischemic myocardial burden, which may lead to better comprehensive evaluation of coronary artery disease,” the authors concluded.

Reference

Kim HY, Lim H-S, Doh J-H, et al. Physiological severity of coronary artery stenosis depends on the amount of myocardial mass subtended by the coronary artery. JACC Cardiovasc Interv. 2016. doi:10.1016/j.jcin.2016.04.008