Abstract
The hyperemic stenosis resistance index is the best parameter correlating with the induction of myocardial ischemia, it provides amore accurate assessment of the severity of coronary stenosis than FFR, similarly, the CFR has a high predictive value. The principleof the iFR (instant wave-free ratio) is the determination of the ratio of the distal and aortic pressure during the wave-free periodin the consecutive cardiac cycles.
Due to the minimal microvascular resistance in this period, administration of adenosine is notrequired. More accurate results of iFR are mainly due to false positive results of FFR in nonsignificant coronary stenoses withnormal microvascular function and a high CFR. iFR -SWEDEHEART and DEFINE-FLAIR studies showed that in patients with clinicalindication for physiologically guided evaluation of coronary artery stenosis, iFR is not inferior to the FFR, as regards the incidenceof death, MI and unplanned revascularization during the 12 months follow-up.
In a subsequent meta-analysis of DEFINE-FLAIRand iFR-SWEDEHEART, a higher incidence of death and myocardial infarctions in the iFR group was, however, demonstrated,albeit the differences were not statistically significant. Thus, the iFR non-inferiority hypothesis was not denied, nevertheless thefinal assessment of whether the iFR is non-inferior compared to the FFR in the management of myocardial revascularization willrequire further research.