Abstract 3333: Stability of Fractional Flow Reserve and Index of Microcirculatory Resistance Post Intervention
Background: Changes in microcirculatory resistance and collateral flow occur following percutaneous intervention. In some patients a vasodilatory response predominates whilst in others resistance increases as a result of vascular obstruction and vasoconstriction. Fractional flow reserve (FFR) values post procedure have prognostic importance, however, variability in microcirculatory resistance impacts on values as a result of changes in distal coronary pressure. This study examines FFR and index of microcirculatory resistance (IMR) immediately post intervention.
Methods and Results: Physiological parameters post intervention were examined in 24 vessels (hyperaemia achieved with adenosine 140μg/kg/min IV). FFR and IMR were recorded serially over a 15 minute period post stenting. Pre-intervention mean (SD) FFR and IMR were 0.60 (0.20) and 27.8 (7.8). Changes in both parameters were observed post procedure. In some cases values increased whilst in others a decrease was observed, thus overall changes were not found to be statistically significant. Mean FFR and IMR changed by 1.2% and 3.3% respectively between the first and second measurements post stent, and by 6.9% and 16.6% between the first and third measurement. Furthermore the maximum change in FFR was found to be 33.4% and maximum change in IMR 59.9%.
Conclusions: This study of serial FFR measurements following intervention demonstrates marked variability in values in the immediate post-procedure period. The corresponding variability in IMR values suggests this is the consequence of changes in microvascular resistance and thus interpretation of FFR values post intervention should be made with caution.