This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Leesar, M. A. Search for Related Content PubMed Articles by Leesar, M. A. Related Collections Related Article

Baseline Fractional Flow Reserve and Stent Diameter Predict Event Rates After Stenting

A Further Step, But Still Much to Learn^_*

University of Cincinnati College of Medicine, Cincinnati, Ohio

Key Words: fractional flow reserve • percutaneous coronary intervention • drug-eluting stent • bare-metal stent

Pijls et al. (1) demonstrated that 5-year outcome after deferral of percutaneous coronary intervention of intermediate coronary stenoses, on the basis of an FFR cut-point of 0.75, was excellent. In addition, they demonstrated that the risk of cardiac death or myocardial infarction was not decreased by stenting. These findings are further substantiated by the fact that deferral of revascularization of angiographically severe but physiologically insignificant stenoses was associated with a favorable outcome and spontaneous resolution of symptoms. Deferring percutaneous coronary intervention in nonischemic stenotic lesions as assessed by FFR is associated with an annual rate of death or myocardial infarction of approximately 1% in patients with single-vessel coronary artery disease, which is lower than the rate after routine stenting. It is worth noting that, even in the era of drug-eluting stents (DES), stenting of a nonsignificant coronary artery stenosis has no prognostic advantage.

Normal epicardial coronary arteries provide no resistance to blood flow, not even during maximum hyperemia. Therefore, optimum coronary stenting should at least result in the disappearance of any hyperemic pressure drop within the respective coronary segment. The measurement of FFR has been proposed as a technique for optimizing the stent results. Indeed, the elimination of any trans-stenotic hyperemic gradient after stenting correlates well with optimal stent deployment on the basis of intravascular ultrasound (IVUS) criteria. Abnormal FFR identifies both residual hyperemic pressure gradient and abnormal resistance across the stented segment and in the adjacent parts of the vessel. In this respect, Pijls et al. (2) conducted a multicenter bare-metal stent (BMS) FFR registry in 750 patients to investigate the correlation between FFR measured after stent implantation and major adverse cardiac events, including the need for target vessel revascularization during the 6 months after implantation. This study demonstrated that measurement of FFR immediately after stent implantation is a strong independent predictor of the event rates such as death, myocardial infarction, or need for repeat revascularization of the target vessel within 6 months. Likewise, the study demonstrated that the higher the FFR, the lower the event rate such that, in 36% of the patients that FFR normalized (FFR >0.95), event rate was 4.9%. In 32% of the patients, post-stent FFR was between 0.90 and 0.95, and event rate was 6.2%. In 32% of patients, post-stent FFR was <0.90, and event rate was 20.3%. In 6% of the patients, FFR was <0.80, and event rate was 29.5% (p < 0.001).

The study reported by Samady et al. (3) in this issue of JACC: Cardiovascular Interventions, is a post hoc analysis of 586 patients derived from the BMS FFR registry that was originally reported in 750 patients (2). Because the BMS registry demonstrated that an FFR >0.90 after stenting was associated with a low event rate of 6%, Samady et al. (3) sought to determine whether variables such as baseline FFR, stent diameter, and stent length would predict a post-stent FFR of 0.90. In this context, Samady et al. (3) demonstrated that a baseline FFR >0.70 compared with a baseline FFR <0.70, after deployment of a 3.0-mm-diameter stent in patients with a coronary artery stenosis, would yield a higher likelihood of achieving an FFR 0.90 (77% vs. 63%, respectively; p < 0.05). Likewise, Samady et al. (3) reported that a baseline FFR <0.50 compared with a baseline FFR ranging from 0.50 to 0.70 and a baseline FFR >0.70, after deployment of a stent with a diameter <3.0 mm, was associated with a higher event rate (40% vs. 15%, and 13%, respectively; p < 0.05). Furthermore, Samady et al. reported that event rates in patients with a stent diameter >3.0 mm, regardless of baseline FFR, were <10% with a BMS.

The authors are to be commended for their vigilance in identifying the predictors of post-stent FFR cut-point of 0.90. Notably, the study is a post hoc analysis of a large registry with all its inherent limitations and requires further validation, but the data have important clinical implications. In this respect, the results suggest that baseline FFR and stent diameter would usher in a decision-making strategy with respect to judicious use of a BMS versus a DES. In particular, the aforementioned data indicate that, among patients with a stent diameter >3.0 mm, event rates were <10% with a BMS, which is similar to that of DES; thus, this would potentially circumvent the need for a DES. In addition, the data indicate that patients with a stent diameter of 3.0 mm and baseline FFR >0.70 would have a significant likelihood of achieving an optimal post-stent FFR of 0.90 with a BMS. Along the same line, patients with a stent diameter of <3.0 mm and FFR >0.70 would have an acceptable event rate of 13% with a BMS. In contrast, patients with a stent diameter <3.0 mm and FFR <0.50 would have a high event rate with a BMS.

In recent years, there has been an explosion in the use of DES, but concerns have been raised about the possible increased incidence of stent thrombosis with DES. A meta-analysis of all randomized trials comparing DES with BMS demonstrated similar mortality rates (4). One trial even showed an incidence of late stent thrombosis of 1.4% in the DES group versus 0.8% in the BMS group (5). Nevertheless, certain patient subsets might be well-served with the use of a BMS, if frequency of restenosis can be predicted to be low by FFR or stent diameter. In addition, multiple studies have shown that the single most important predictor of stent thrombosis is the premature discontinuation of antiplatelet therapy, with a dramatic increase in stent thrombosis seen in patients taken off therapy (6). It is of paramount importance that before stent implantation, all patients be evaluated for their ability to continuously receive and tolerate dual antiplatelet therapy.

There are several potential clinical implications for measurements of FFR before and after stenting. First, it is well known that angiography is limited in defining the significance of stenosis; therefore, the measurement of FFR might potentially obviate the need for stenting. Second, it is tempting to speculate that patients with a baseline FFR >0.70, stent diameter of 3.0 mm, and short lesion length might achieve an optimal post-stent FFR of 0.90, and thus DES might not be needed. Furthermore, if such a patient would require biopsy or noncardiac surgery, clopidogrel therapy could be discontinued within 4 weeks of stenting. Third, angiography is a rather inaccurate tool for evaluating the result of stenting, as demonstrated by IVUS. In this respect, incomplete stent deployment, protruding struts, or plaque shift at the entry or exit of the stent is often not recognized by angiography but might result in early in-stent restenosis (7). Such abnormalities can often be detected by the persistence of a hyperemic pressure gradient across the stented segment (8). Therefore, it is likely that several patients with restenosis in fact had suboptimal stent deployment not detected by angiography. Finally, coronary pressure measurement not only reveals an abnormal conductance within the stented segment but also indicates increased plaque accumulation in the remaining part of the coronary artery, contributing to decreased FFR and worst outcome (9).

The results of the aforementioned studies underscore the need for further prospective studies to assess the impact of baseline FFR, stent diameter, and stent length in predicting final FFR after stenting and to address whether additional strategies, such as performing IVUS or high-pressure balloon inflation after stenting in the setting of suboptimal FFR, would translate into improved outcome.

	Footnotes

 
^_* Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.

^_* Reprint requests and correspondence: Dr. Massoud A. Leesar, Professor of Medicine, Associate Chief, Division of Cardiology, Director, Cardiac and Vascular Invasive Services, University of Cincinnati College of Medicine, 231 Albert Sabin Way-ML 0542, Cincinnati, Ohio 45267-0542 (Email: leesarma{at}UC.edu).

	REFERENCES

Top REFERENCES

 

1. Pijls NHJ, van Schaardenburgh P, Manoharan G, et al. Percutaneous coronary intervention of functionally nonsignificant stenosis: 5-year follow-up of the DEFER Study J Am Coll Cardiol 2007;49:2105-2111.[Abstract/Free Full Text]
2. Pijls NHJ, Klauss V, Siebert U, et al. Coronary pressure measurement after stenting predicts adverse events at follow-up: a multicenter registry Circulation 2002;105:2950-2954.[Abstract/Free Full Text]
3. Samady H, McDaniel M, Veledar E. Baseline fractional flow reserve and stent diameter predict optimal post-stent fractional flow reserve and major adverse cardiac events after bare metal stent deployment J Am Coll Cardiol Intv 2009;2:357-363.[Abstract/Free Full Text]
4. Stettler C, Wandel S, Allemann S, et al. Outcomes associated with drug-eluting and bare-metal stents: a collaborative network meta-analysis Lancet 2007;370:937-948.[CrossRef][Web of Science][Medline]
5. Pfisterer M, Brunner-La Rocca HP, Buser PT, et al. BASKET-LATE Investigators Late clinical events after clopidogrel discontinuation may limit the benefit of drug-eluting stents: an observational study of drug-eluting versus bare-metal stents J Am Coll Cardiol 2006;48:2584-2591.[Abstract/Free Full Text]
6. Mauri L, Hsieh WH, Massaro JM, Ho KK, D'Agostino R, Cutlip DE. Stent thrombosis in randomized clinical trials of drug-eluting stents N Engl J Med 2007;356:1020-1029.[CrossRef][Medline]
7. Mintz GS, Popma J, Pichard A, et al. Intravascular ultrasound predictors of restenosis after percutaneous transcatheter coronary revascularization J Am Coll Cardiol 1996;27:1678-1687.[Abstract]
8. Hanekamp C, Koolen JJ, Pijls NHJ, et al. Comparison of quantitative coronary angiography, intravascular ultrasound and pressure-derived fractional flow reserve to assess optimal stent deployment Circulation 1999;99:1015-1021.[Abstract/Free Full Text]
9. De Bruyne B, Hersbach F, Pijls NHJ, et al. Abnormal epicardial coronary resistance in patients with diffuse atherosclerosis but "normal" coronary angiography Circulation 2001;104:2401-2406.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Leesar, M. A. Search for Related Content PubMed Articles by Leesar, M. A. Related Collections Related Article