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Background: Quantitative flow ratio (QFR) is a newly developed image-based index for estimating fractional flow reserve (FFR). Methods and Results:We analyzed 151 coronary arteries with intermediate stenosis in 142 patients undergoing wire-based FFR measurement using dedicated software. Predefined contrast flow QFR, which was derived from 3-dimensional quantitative coronary angiography (3-D QCA) withThrombolysis in Myocardial Infarction (TIMI) frame counts, was compared with FFR as a reference. QFR had good correlation (r=0.80, P<0.0001) and agreement (mean difference: 0.01±0.05) with FFR. After applying the FFR cut-off ≤0.8, the overall accuracy rate of QFR ≤0.8 was 88.0%. On receiver operating characteristics analysis, the area under the curve was 0.93 for QFR. In contrast, 3-D QCA-derived anatomical indices had insufficient correlation with FFR and diagnostic performance compared with QFR.Conclusions: QFR had good correlation and agreement with FFR and high diagnostic performance in the evaluation of intermediate coronary stenosis, suggesting that QFR may be an alternative tool for estimating myocardial ischemia.

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umerous randomized trials have successfully demonstrated the beneficial effects of early percutaneous coronary intervention (PCI) for patients with acute myocardial infarction (AMI). [1][2][3] However, most patients with complications of renal insufficiency were excluded from randomized trials; therefore, the clinical effects of PCI for these patients have not been determined.In the past decade, patients with end-stage renal disease were associated with a decreased procedural success rate. [4][5][6] The development of device technology has provided better procedural outcomes after PCI in such patients 7-9 ; however, little is known regarding the impact of varying degrees of renal insufficiency on the success rate of emergency PCI in patients with AMI.As noted in a recent study, the success of PCI is a prime determinant of the clinical outcome of patients with AMI. 10 However, renal insufficiency is associated with a worse clinical outcome in patients with coronary artery disease including AMI. [11][12][13][14][15][16] It is also unclear whether successful PCI provides a better prognosis of AMI even in patients Circulation Journal Vol.72, February 2008 with renal insufficiency.The aims of this study were: (1) to determine the association between renal insufficiency and the risk of unsuccessful primary PCI in AMI patients; and (2) to evaluate the correlation between unsuccessful primary PCI and the clinical outcomes at various levels of renal function. Methods Study PopulationThe subjects of the present study were selected from the Heart Institute of Japan Acute Myocardial Infarction Registry (HIJAMI) database. Full details of the HIJAMI registry have been described elsewhere. 17 In brief, HIJAMI is a multicenter prospective cohort of consecutive patients with AMI who were admitted within 48 h after the onset of symptoms. Between January 1999 and July 2001, 3,021 consecutive patients from 17 participating hospitals in Japan were registered. As HIJAMI was meant for observational purposes, treatment strategies, such as drug therapies and early reperfusion treatment, were used at the discretion of the physician responsible at each hospital. Clinical and angiographic data, including the patients' demographics, coronary risk factors, therapeutic modalities, complications, number of diseased vessels, infarct-related arteries, PCI strategies, laboratory data and in-hospital outcomes were prospectively collected using a standardized case report form. Serum creatinine concentrations and C-reactive protein were measured at each site immediately after admis-

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