Correspondence Cardiovascular Center, OLV Clinic, Moorselbaan 164, 9300 Aalst, Belgium

Email bernard.de.bruyne@olvz-aalst.be

Original article

Legalery P et al. (2005) One-year outcome of patients submitted to routine fractional flow reserve assessment to determine the need for angioplasty. Eur Heart J 26: 2623–2629   PubMed

Synopsis

Background

Despite the proven efficacy and accuracy of FRACTIONAL FLOW RESERVE (FFR) for identifying clinically significant stenoses—even in patients with multivessel disease or acute coronary syndromes—the technique is still underused in clinical decision making and the majority of decisions are based on angiography alone. By investigating long-term outcomes, Legalery et al. hope to increase the use of FFR in clinical practice.

Objective

To investigate the long-term patient outcomes when FFR assessment is used to decide whether to revascularize lesions of unclear severity.

Design and intervention

All patients who underwent coronary angiography at a single center from January 2000 to October 2003 were included in this prospective registry. Although the acting physician was given the option of whether or not to use FFR, its use was advised for stenoses without myocardial ischemia and a diameter of 40–60% seen on angiography (i.e. intermediate lesions). Patients who had stenoses with a diameter of 20–40% (i.e. nonsignificant lesions) and were positive for ischemia in noninvasive stress testing also underwent FFR assessment. Revascularization was recommended if FFR was under the cut-off value of 0.8. Legalery et al.'s paper only analyzed patients who had undergone FFR. Patients were grouped in terms of whether their treatment decision was made in accordance with FFR findings. The 'compliant' group consisted of those with an FFR of 0.8 or more who received medical therapy only, and those with an FFR less than 0.8 who underwent revascularization; the 'noncompliant' group consisted of those who had medical therapy only despite an FFR less than 0.8, and those who had revascularization despite an FFR of 0.8 or more.

Outcome measures

The main outcomes were nonfatal acute coronary syndromes, target-vessel revascularization and all-cause death.

Results

Of the 6,288 patients who underwent coronary angiography, 407 underwent FFR assessment (68% male, average age 59 years). By comparing the FFR result with the treatment performed, 336 patients (83%) were compliant (99 with an FFR less than 0.8 were revascularized and 237 with an FFR of 0.8 or more received medical therapy only) and 71 were noncompliant (34 with an FFR less than 0.8 received medical therapy only and 37 with an FFR of 0.8 or more were revascularized). Patients treated in accordance with their FFR results had better 1-year outcomes, and there were significantly more adverse events in the noncompliant group than in the compliant group after 1 year (15.5% vs 6% of patients; P = 0.01). At 1-year follow-up, there were 5 nonfatal acute coronary syndromes, 20 target-vessel revascularizations and 6 deaths. Revascularization did not affect the occurrence of adverse events—there were 9 adverse events in the 136 patients who had undergone revascularization and 22 in the 271 patients who had not (7% vs 8%; P = 0.69).

Conclusion

The routine use of FFR findings to determine treatment strategy is safe and feasible, and leads to fewer adverse events at 1 year.

Commentary

Selective coronary angiography remains fundamental to the confirmation of suspected coronary artery disease; however, it is only an approximate guide to the potential hemodynamic effect of a narrowed vessel. A meta-analysis of almost 70,000 patients undergoing myocardial perfusion imaging confirmed that with a normal myocardial perfusion imaging result, the median annual rate of cardiac death or nonfatal myocardial infarction is only 0.6%, while an abnormal result raises risk by almost 10 times.¹ Nevertheless, as few patients undergo noninvasive stress testing before percutaneous coronary intervention (PCI), in daily practice the vast majority of revascularization decisions are based solely on angiography.² The lack of noninvasive stress testing could be explained by the fact that tests are often performed in another department and the fact that their execution might prolong hospital stay. In addition, most tests have low diagnostic accuracy in lesions with intermediate severity and poor spatial resolution in patients with multivessel disease—precisely the patients in whom complementary information is needed to guide revascularization. There is also growing belief that drug-eluting stents can be placed with impunity, partly because they can be deployed with ease and partly because of an unsubstantiated belief that they prevent acute coronary syndromes.

FFR is an index of stenosis severity that can be obtained in the catheterization laboratory. An FFR of 0.6 means that the maximum amount of blood supplying that particular myocardial distribution only reaches 60% of the area it would reach if the artery were completely free of stenoses. FFR is based on simple intracoronary pressure measurement and provides information very similar to that of perfusion imaging, but with lesion specificity and better spatial resolution. An FFR less than 0.75 indicates that the stenosis can induce ischemia; an FFR greater than 0.8 virtually excludes ischemia. This 'grey' zone is very limited, which is important for clinical decision making.

The safety of not performing PCI with stenoses with an FFR higher than the ischemic threshold was first demonstrated in patients with single-vessel disease. After 5 years, the rate of cardiac events in patients with an isolated nonsignificant stenosis (FFR greater than 0.75) is similar whether or not PCI was performed. Data have suggested that FFR is particularly useful in tailoring the revascularization strategy in patients with left main disease and multivessel disease.^{3, 4} This study by Legalery et al. confirms the safety of deferring PCI in patients with a high FFR. Furthermore, their work makes the important observation that patients in whom a stenosis is left untreated despite a low FFR have a poor prognosis. This happens especially frequently in stenoses of the left main stem and proximal segments of the left anterior descending or dominant right coronary artery, where the flow is high—because the myocardial mass to be perfused is large—and where the angiogram often underestimates the true severity of the stenosis.

These findings confirm what noninvasive cardiologists have been claiming for decades: ischemia-producing lesions have a poor prognosis and lesions that do not induce ischemia have a favorable prognosis. With pressure-derived FFR measurement, this information can now be easily obtained in the catheterization laboratory where treatment can be applied immediately if necessary.

In conclusion, coronary pressure-derived FFR might, to some extent, replace noninvasive testing and should be measured as soon as there is any doubt about the true severity of coronary narrowing detected on angiography.

Acknowledgments

The synopsis was written by Hannah Camm, Associate Editor, Nature Clinical Practice.

References

1. Shaw LS and Iskandrian AE (2004) Prognostic value of gated myocardial perfusion SPECT. J Nucl Cardiol 11: 171–185 | Article | PubMed | ISI |
2. Topol EJ et al. (1993) Analysis of coronary angioplasty practice in the United States with an insurance-claims data base. Circulation 87: 1489–1497 | PubMed | ISI | ChemPort |
3. Botman KJ et al. (2004) Percutaneous coronary intervention or bypass surgery in multivessel disease? A tailored approach based on coronary pressure measurement. Cath Cardiovasc Int 63: 184–191 | ISI |
4. Berger A et al. (2005) Long-term clinical outcome after fractional flow reserve-guided percutaneous coronary intervention in patients with multivessel disease. J Am Coll Cardiol 46: 438–442 | Article | PubMed | ISI |

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Subject areas under which this article appears: Imaging and other investigations | Intervention