Stenotic flow reserve assessed on quantitative coronary angiography has modest but incremental value in predicting functionally significant coronary stenosis as evaluated by fractional flow reserve.

Introduction: Stenoticflowreserve (SFR) assessed on quantitative coronary angiography (QCA) has been correlated with myocardial ischaemia as determined by pharmacological stress echocardiography. The ability of SFR to accurately predict functionally significant coronary stenosis by the gold standard, fractional flow reserve (FFR) is not widely studied and may have clinical utility. Method(s): Patients who underwent invasive coronary angiography and FFR assessment (January 2010-February 2012) were included. SFR, mean luminal diameter (MLD), diameter-stenosis (DS) >50% on QCA, lesion length, turbulent and Poiseulle resistance were calculated. FFR <0.8 was significant. The diagnostic accuracy of QCA parameters to predict significant FFR was assessed by independent t-test and receiver operator characteristic curve. Result(s): 272 patients (mean age 64 +/- 11, 70% males) and 415 vessels were included. The mean FFR value was 0.81 +/- 0.11. 180 (43%) vessels were FFR significant. On comparison of area under curve for predicting significant FFR, SFR (0.76) had the highest diagnostic accuracy compared to Poiseulle resistance (0.75), diameter stenosis (0.73), turbulent resistance (0.69), MLD (0.71) and DS>50% on QCA (0.64). For an optimised cut-off value of 3.51, the sensitivity of SFR was modest at 56% with good specificity 81%. QCA >50% had a sensitivity of 47% and specificity of 82% in predicting significant FFR. Adding SFR to QCA >50% saw incremental predictive value based on integrated discrimination improvement index (IDI=0.103, P<0.001) and net reclassification index (NRI=0.72, P<0.001). Conclusion(s): SFR has only modest diagnostic accuracy for predicting significant FFR and adds incremental predictive value to DS>50% on QCA.