Hemodynamic Response to Intravenous Adenosine and Its Effect on Fractional Flow Reserve Assessment:Results of the Adenosine for the Functional Evaluation of Coronary Stenosis Severity (AFFECTS) Study

Background— We studied the hemodynamic response to intravenous adenosine on calculation of fractional flow reserve (FFR). Intravenous adenosine is widely used to achieve conditions of stable hyperemia for measurement of FFR. However, intravenous adenosine affects both systemic and coronary vascular beds differentially. Methods and Results— A total of 283 patients (310 coronary stenoses) underwent coronary angiography with FFR using intravenous adenosine 140 mcg/kg per minute via a central femoral vein. Offline analysis was performed to calculate aortic (Pa), distal intracoronary (Pd), and reservoir (Pr) pressure at baseline, peak, and stable hyperemia. Seven different hemodynamic patterns were observed according to Pa and Pd change at peak and stable hyperemia. The average time from baseline to stable hyperemia was 68.2±38.5 seconds, when both ΔPa and ΔPd were decreased (ΔPa, −10.2±10.5 mm Hg; ΔPd, −18.2±10.8 mm Hg; P &lt;0.001 for both). The fall in Pa closely correlated with the reduction in peripheral Pr (ΔPr, −12.9±15.7 mm Hg; P &lt;0.001; r =0.9; P &lt;0.001). ΔPa and ΔPd were closely related under conditions of peak ( r =0.75; P &lt;0.001) and stable hyperemia ( r =0.83; P &lt;0.001). On average, 56% (10.2 mm Hg) of the reduction in Pd was because of fall in Pa. FFR lesion classification changed in 9% using an FFR threshold of ≤0.80 and 5.2% with FFR threshold &lt;0.75 when comparing Pd/Pa at peak and stable hyperemia. Conclusions— Intravenous adenosine results in variable changes in systemic blood pressure, which can lead to alterations in FFR lesion classification. Attention is required to ensure FFR is measured under conditions of stable hyperemia, although the FFR value at this point may be numerically higher. </jats:sec

Diagnostic Classification of the Instantaneous Wave-Free Ratio Is Equivalent to Fractional Flow Reserve and Is Not Improved With Adenosine Administration:Results of CLARIFY (Classification Accuracy of Pressure-Only Ratios Against Indices Using Flow Study)

ObjectivesThis study sought to determine if adenosine administration is required for the pressure-only assessment of coronary stenoses.BackgroundThe instantaneous wave-free ratio (iFR) is a vasodilator-free pressure-only measure of the hemodynamic severity of a coronary stenosis comparable to fractional flow reserve (FFR) in diagnostic categorization. In this study, we used hyperemic stenosis resistance (HSR), a combined pressure-and-flow index, as an arbiter to determine when iFR and FFR disagree which index is most representative of the hemodynamic significance of the stenosis. We then test whether administering adenosine significantly improves diagnostic performance of iFR.MethodsIn 51 vessels, intracoronary pressure and flow velocity was measured distal to the stenosis at rest and during adenosine-mediated hyperemia. The iFR (at rest and during adenosine administration [iFRa]), FFR, HSR, baseline, and hyperemic microvascular resistance were calculated using automated algorithms.ResultsWhen iFR and FFR disagreed (4 cases, or 7.7% of the study population), HSR agreed with iFR in 50% of cases and with FFR in 50% of cases. Differences in magnitude of microvascular resistance did not influence diagnostic categorization; iFR, iFRa, and FFR had equally good diagnostic agreement with HSR (receiver-operating characteristic area under the curve 0.93 iFR vs. 0.94 iFRa and 0.96 FFR, p = 0.48).ConclusionsiFR and FFR had equivalent agreement with classification of coronary stenosis severity by HSR. Further reduction in resistance by the administration of adenosine did not improve diagnostic categorization, indicating that iFR can be used as an adenosine-free alternative to FFR. (Classification Accuracy of Pressure-Only Ratios Against Indices Using Flow Study [CLARIFY]; NCT01118481