BACKGROUNDCoronary revascularization guided by fractional flow reserve (FFR) is associated with better patient outcomes after the procedure than revascularization guided by angiography alone. It is unknown whether the instantaneous wave-free ratio (iFR), an alternative measure that does not require the administration of adenosine, will offer benefits similar to those of FFR. METHODSWe randomly assigned 2492 patients with coronary artery disease, in a 1:1 ratio, to undergo either iFR-guided or FFR-guided coronary revascularization. The primary end point was the 1-year risk of major adverse cardiac events, which were a composite of death from any cause, nonfatal myocardial infarction, or unplanned revascularization. The trial was designed to show the noninferiority of iFR to FFR, with a margin of 3.4 percentage points for the difference in risk. RESULTSAt 1 year, the primary end point had occurred in 78 of 1148 patients (6.8%) in the iFR group and in 83 of 1182 patients (7.0%) in the FFR group (difference in risk, −0.2 percentage points; 95% confidence interval [CI], −2.3 to 1.8; P<0.001 for noninferiority; hazard ratio, 0.95; 95% CI, 0.68 to 1.33; P = 0.78). The risk of each component of the primary end point and of death from cardiovascular or noncardiovascular causes did not differ significantly between the groups. The number of patients who had adverse procedural symptoms and clinical signs was significantly lower in the iFR group than in the FFR group (39 patients [3.1%] vs. 385 patients [30.8%], P<0.001), and the median procedural time was significantly shorter (40.5 minutes vs. 45.0 minutes, P = 0.001). CONCLUSIONSCoronary revascularization guided by iFR was noninferior to revascularization guided by FFR with respect to the risk of major adverse cardiac events at 1 year. The rate of adverse procedural signs and symptoms was lower and the procedural time was shorter with iFR than with FFR. ( Use of Instantaneous Wave-free R atio in PCI F or the past 20 years, physiological measurements obtained during invasive procedures have been used to guide coronary revascularization. Pioneering work supported the use of flow measurements to make safe decisions about revascularization, 1,2 but this approach was soon superseded by the use of fractional flow reserve (FFR), which measures pressure as a surrogate of flow to estimate the severity of stenosis. 3-5 FFR was successful largely because of its technical simplicity and because clinical trials showed that it was associated with improved clinical outcomes after percutaneous coronary intervention (PCI). 6,7 Consequently, FFR is now included in the appropriate-use criteria for coronary angiography and in the American College of Cardiology-American Heart Association-European Society of Cardiology guidelines; despite these recommendations, its adoption remains limited. [8][9][10] FFR must be measured during maximal hyperemia, which is typically induced with the administration of a potent intravenous or intracoronary vasodilator, such as adenosine. 11 Several studies have...

Current guidelines for the diagnosis of non-ST-segment elevation myocardial infarction are largely based on an elevated troponin level. While this rapid and sensitive blood test is certainly valuable in the appropriate setting, its widespread use in a variety of clinical scenarios may lead to the detection of troponin elevation in the absence of thrombotic acute coronary syndromes. Many diseases, such as sepsis, hypovolemia, atrial fibrillation, congestive heart failure, pulmonary embolism, myocarditis, myocardial contusion, and renal failure, can be associated with an increase in troponin level. These elevations may arise from various causes other than thrombotic coronary artery occlusion. Given the lack of any supportive data at present, patients with nonthrombotic troponin elevation should not be treated with antithrombotic and antiplatelet agents. Rather, the underlying cause of the troponin elevation should be targeted. However, troponin elevation in the absence of thrombotic acute coronary syndromes still retains prognostic value. Thus, cardiac troponin elevations are common in numerous disease states and do not necessarily indicate the presence of a thrombotic acute coronary syndrome. While troponin is a sensitive biomarker to "rule out" non-ST-segment elevation myocardial infarction, it is less useful to "rule in" this event because it may lack specificity for acute coronary syndromes. Ann Intern Med. 2005;142:786-791. www.annals.org For author affiliations, see end of text.

This comprehensive core laboratory analysis comparing iFR and Pd/Pa with FFR demonstrated an overall accuracy of ~80% for both nonhyperemic indices, which can be improved to ≥90% in a subset of lesions. Clinical outcome studies are required to determine whether the use of iFR or Pd/Pa might obviate the need for hyperemia in selected patients.