ASSESSMENT OF THE FUNCTIONAL SIGNIFICANCE OF STENOSIS IN MULTIVESSEL CORONARY ARTERY DISEASE BASED ON INTEGRAL INSTANT FLOW RESERVE

Abstract

HighlightsThe assessment of the anatomical significance of multivessel atherosclerosis of the coronary arteries – SYNTAX score takes into account the level and multiplicity of lesions by assigning higher scores for proximal stenoses and subsequent summation. Functional assessment of coronary blood flow – instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) uses one threshold value for all stenoses, and does not take into account their multiplicity. Aim. To develop a new indicator for the integral assessment of the functional significance of multivessel atherosclerosis of the coronary arteries, taking into account the level and multiplicity of lesions.Methods. The model for the integral assessment of the functional significance of a multivessel lesion was the sum of the transstenotic gradients (in our variant 1-iFR) of all stenoses >50%, weighted by the volume of the dependent LV myocardium, which was evaluated on the Duke jeopardy score: Σ(1-iFRi)*Nd, where Nd is the number of Duke dependent segmental arteries supplying blood to 1/6 of the myocardium. To bring the obtained values to the range 0–1 and the threshold level 0.89, the 1/(1+X) transformation was used, i.e. in the case of single non-proximal stenoses, the integral assessment index is equal to the value of the standard iFR. To test the ability of the indicator to take into account the level and multiplicity of lesions, we evaluated its relationship with SYNTAX in patients with multivessel coronary artery disease (>2 segments with stenoses >50%), including in comparison with standard iFR (minimum value). The VERRATA PLUS conductor and the Core module of the Phillips Azurion angiographic system were used for iFR measurements.Results. The study included 42 patients, 29 men and 13 women, aged 65.3 ± 8.9 years, with multivessel coronary artery disease, SYNTAX score = 11.5 ± 2.7. The calculated values of integral iFR were expected to be less than the minimum standard iFR: 0.71 ± 0.11 versus 0.81 ± 0.14, respectively, p < 0,001. Integral iFR demonstrated significant inverse dependence on SYNTAX, p = 0,34, p < 0,05, whereas the standard iFR did not depend on SYNTAX. The number of patients with non-significant standard iFR, but significant integral iFR was 23.5% compared to patients with significant standard iFR. In accordance with the nature of the calculations, there were no cases of significant standard iFR and insignificant integral iFR.Conclusion. The obtained data demonstrated the possibility of taking into account the level and multiplicity of stenoses when assessing the functional significance of coronary artery lesions using the iFR method.