{"id":34515,"date":"2013-02-06T16:10:47","date_gmt":"2013-02-06T21:10:47","guid":{"rendered":"http:\/\/blogs.nejm.org\/cardioexchange\/?post_type=interventional&#038;p=34515"},"modified":"2013-02-06T16:11:28","modified_gmt":"2013-02-06T21:11:28","slug":"ffr-vs-ifr-all-that-glitters-is-not-gold","status":"publish","type":"post","link":"https:\/\/blogs.nejm.org\/cardioexchange\/2013\/02\/06\/ffr-vs-ifr-all-that-glitters-is-not-gold\/","title":{"rendered":"FFR vs. iFR: All That Glitters Is Not Gold"},"content":{"rendered":"<p><em><strong>The \u201cGold Standard\u201d:<\/strong><\/em> Fractional flow reserve (FFR) is a pressure-derived index of coronary stenosis severity that has been validated for assessing the hemodynamic significance of stenoses that are of \u201cintermediate\u201d angiographic severity.\u00a0In fact, FFR use during PCI\u00a0carries a Class 1A recommendation from the European Society of Cardiology and a Class IIA recommendation from the American College of Cardiology, despite the fact that it\u00a0requires additional instrumentation of the coronary arteries and pharmacologic vasodilation to induce maximal hyperemia.<\/p>\n<p><em><strong>Easier Money?<\/strong><\/em> The instantaneous wave-free ratio (iFR) is an alleged index of coronary stenosis severity that is independent of hyperemia. It is based on the hypothesis that coronary microvascular resistance is minimal during mid and late diastole (when coronary flow is maximal), so the administration of a vasodilator is unnecessary. It is thought that\u00a0by avoiding the need to administer adenosine, iFR is more\u00a0likely than FFR to\u00a0expand the\u00a0practice of pressure wire-guided decision making.<\/p>\n<p><strong><em>Convertible Currency?<\/em><\/strong> Unfortunately, the results of\u00a0two new studies suggest that iFR is unlikely to replace FFR.<\/p>\n<p>Using a simulation model to study the relationship between iFR and FFR, then validating their predictions with data from a large, multicenter cohort of humans, <a href=\"http:\/\/content.onlinejacc.org\/article.aspx?articleID=1569170\">Johnson and colleagues<\/a> found that:<\/p>\n<ul>\n<li>iFR systematically overestimates FFR, with wide limits of agreement that would often alter management decisions.<\/li>\n<li>In\u00a0individual patients, iFR\u00a0is not\u00a0interchangeable with FFR.<\/li>\n<\/ul>\n<p>In <a href=\"http:\/\/content.onlinejacc.org\/article.aspx?articleid=1569171\">VERIFY<\/a>, a prospective study of 206 consecutive PCI patients\u00a0compared with\u00a0a retrospective analysis of 500 archived pressure recordings, Berry\u00a0and colleagues\u00a0showed that:<\/p>\n<ul>\n<li>The diagnostic accuracy of iFR was only 60% compared\u00a0with the FFR cut-off value of \u00a0&lt;0.80 (a value that has been validated in randomized trials for clinical management).<\/li>\n<\/ul>\n<p><strong><em>Pyrite (Fool\u2019s Gold)<\/em><\/strong>: The VERIFY\u00a0authors conclude \u201c\u2026that iFR cannot be recommended for clinical decision making in patients with coronary artery disease.\u201d\u00a0Too bad, since iFR would be a convenient and quick use of\u00a0a pressure-wire alone\u00a0\u2014 without a vasodilator\u00a0\u2014 to assess coronary stenosis severity.<\/p>\n<p><strong>With all the concerns of inappropriate PCI, do you feel compelled to use FFR to justify PCI?<\/strong><\/p>\n<p><strong>In what percentage of patients with \u201cintermediate\u201d coronary stenoses do you use FFR?<\/strong><\/p>\n<p><strong>Does the hassle associated with administering a vasodilator prevent you from measuring FFR in\u00a0patients with intermediate stenoses?<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>David Hillis and Rick Lange consider new evidence that iFR is not an acceptable substitute for FFR. Does the need for adenosine administration hinder the use of FFR to guide management decisions?<\/p>\n","protected":false},"author":214,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[1027,1286,301,1670],"class_list":["post-34515","post","type-post","status-publish","format-standard","hentry","category-interventional-cardiology","tag-ffr","tag-ifr","tag-pci","tag-verify"],"_links":{"self":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts\/34515","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/users\/214"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/comments?post=34515"}],"version-history":[{"count":0,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts\/34515\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/media?parent=34515"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/categories?post=34515"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/tags?post=34515"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}