ORONARY COMPUTED TOMOgraphic (CT) angiography is a noninvasive test that enables direct visualization of coronary artery disease (CAD) and correlates favorably with invasive coronary angiography (ICA) for measures of stenosis severity. 1 However, CT cannot determine the hemodynamic significance of CAD, and even among CTidentified obstructive stenoses confirmed by ICA, fewer than half are ischemia-causing. 2,3 These findings underscore an unreliable relationship of stenosis severity to ischemia and have raised concerns that use of CT may pre-cipitate unnecessary ICA and coronary revascularization for patients who do not have ischemia. 4,5 These concerns stem from recent randomized trials that have identified no survival benefit for patients who undergo angiographically based coronary revascularization. 6,7 As an ad-junct to ICA, fractional flow reserve (FFR) has served as a useful tool to determine the likelihood that a coronary For editorial comment see p 1269.

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Multislice computed tomography (CT) is an emerging technique for the non-invasive detection of coronary stenoses. While the diagnostic accuracy of 4-slice scanners was limited, 16-slice CT imagers showed promising results due to increased temporal and spatial resolution. These technical advances prompted us to evaluate the diagnostic performance of 64-slice CT coronary angiography in the detection of significant stenoses (defined as > or = 50% luminal diameter reduction) versus invasive quantitative coronary angiography (QCA). Thirty-five patients with stable angina pectoris underwent CT coronary angiography performed with a 64-slice scanner (gantry rotation time 330 ms, individual detector width 0.6 mm) prior to conventional coronary angiography. Patients with heart rates >70 beats/min received 100 mg metoprolol orally. One hundred millilitres of contrast agent with an iodine concentration of 400 mgl/ml were injected at a rate of 5 ml/s into the antecubital vein. The CT scan was triggered with the bolus tracking technique. The sensitivity, specificity and the positive and negative predictive values of 64-slice CT were 99%, 96%, 78% and 99%, respectively, on a per-segment basis. The values obtained on a per-patient basis were 100%, 90%, 96% and 100%, respectively. When referral to catheterisation is questionable, CT coronary angiography may identify subjects with normal angiograms and consistently decrease the number of unnecessary invasive procedures.

The data confirm that one-third of a large patient population shows discordance between angiogram ≥ 50%DS and FFR ≤ 0.8 thresholds of stenosis severity. Left main stenoses are often underestimated by the classical 50% DS cut-off compared with FFR. This discordance offers physiologic insights for future trials. It is hypothesized that the discordance between angiography and FFR is related to technical limitations, such as imprecise luminal border detection by angiography, as well as to physiologic factors, such as variable minimal microvascular resistance.

Background-Fractional P<0.001). At 3 years, major adverse cardiovascular events were not different between the angiography-guided and FFR-guided groups (12% versus 11%; hazard ratio, 1.030; 95% confidence interval, 0.627-1.692; P=0.908). However, the FFR-guided group compared with the angiography-guided group presented a significantly lower rate of angina (Canadian Cardiovascular Society class II-IV, 31% versus 47%; P<0.001). Conclusions-FFR-guided coronary artery bypass graft surgery was associated with a lower number of graft anastomoses and a lower rate of on-pump surgery compared with angiography-guided coronary artery bypass graft surgery. This did not result in a higher event rate during up to 36 months of follow-up and was associated with a lower rate of angina. Patients were divided into 2 groups: the angiography-guided group and the FFR-guided group. The angiography-guided group consisted of patients in whom no FFR was measured at the time of the preoperative coronary angiography and CABG was indicated solely on the basis of the angiographic severity of the coronary stenosis. The FFR-guided group consisted of patients in whom at least 1 intermediate stenosis was measured by FFR and grafted in the presence of FFR ≤0.80 or deferred with FFR >0.80. Coronary Angiography and FFR MeasurementCoronary angiography was performed by a standard percutaneous femoral or radial approach with 6F or 7F diagnostic or guiding catheters. After the administration of 200 to 300 µg intracoronary isosorbide dinitrate, the angiogram was repeated in the projection allowing the best possible visualization of the stenosis. Experienced operators not involved in the analysis of the data assessed stenosis severity. Multivessel disease was defined as the presence of stenosis in ≥2 major coronary arteries.Performance of FFR measurement was left to the operator's discretion. FFR was measured as previously described.11,12 Briefly, a pressuremonitoring guidewire (Certus PressureWire; St. Jude Medical Inc, St. Paul, MN) was advanced distal to the coronary artery stenosis. After the administration of intracoronary isosorbide dinitrate (200 μg), hyperemia was obtained with either intravenous infusion (140 μg·kg) or an intracoronary bolus of adenosine (70-100 μg). An FFR value ≤0.80 indicated an ischemia-producing coronary stenosis. Coronary Artery Bypass SurgeryThe type of surgery, namely on-pump or off-pump, and the number and type of grafts were left to the surgeon's discretion. Study End PointsPrimary end point of the study was the rate of major adverse cardiac events, defined as overall death, myocardial infarction, and target vessel revascularization occurring during up to 3 years of clinical followup. Secondary end points were all the individual end points included in major adverse cardiovascular events plus the number of graft anastomoses and symptoms at the last clinical follow-up available. Myocardial infarction was defined as previously described.13,14 Target vessel revascularization was defined as any percutaneous or surgical rev...