About 1 in 20 lesions not revascularized due to fractional flow reserve (FFR) results will require intervention within a year of functional assessment, according to an analysis published online October 21, 2014, ahead of print in the European Heart Journal. Using the study data, researchers constructed a novel algorithm that identifies patients at high risk of revascularization, who may benefit from closer follow-up and more intensive management.

The findings were originally presented at the Transcatheter Cardiovascular Therapeutics scientific symposium in October 2013.

Time Runs Out for Some Deferred Lesions

After FFR-based deferral of revascularization, 5.3% of the lesions required intervention within the first year and 18% underwent treatment (74% by PCI and 26% via CABG) during a mean follow-up of 4.0 years.

A total of 119 patients died, including 44 within 12 months. In addition, 79 suffered an acute MI, with 38% of those events occurring in previously deferred lesions (table 1).

Acute MI accounted for 15% of total interventions performed in the first year in FFR-deferred lesions. Of the 101 lesions (65%) requiring urgent revascularization, 30 lesions were treated for acute MI (6 for STEMI and 24 for NSTEMI) and 71 for unstable angina. Elective revascularization accounted for 34% of interventions, predominantly for stable angina. Overall, revascularizations performed within 1 year of deferral included a higher proportion of urgent procedures than those performed beyond the first year.

A Cox proportional hazards model was developed based on patient- and lesion-level variables determined at the time of FFR assessment. In the final model, multivariable predictors of the probability of freedom from intervention at 1 year were:

• Age, per 1-year increase (HR 0.98; 95% CI 0.97-0.99)
• Current/former smoker (HR 1.49; 95% CI 1.04-2.14)
• History of CAD or prior PCI (HR 1.62; 95% CI 1.05-2.49)
• Creatinine, per 1-mg/dL increase (HR 1.15; 95% CI 1.08-1.22)
• Multivessel CAD (HR 1.68; 95% CI 1.09-2.58)
  
• FFR value, per 0.05-unit decrease (HR 1.21; 95% CI 1.03-1.42)

Based on the algorithm, the predicted probability of intervention over 1 year ranged from 1% to 40%.

The authors observe that despite these findings, “the absence of intervention for over 94% of patients at 1 [year] and of 82% at an average of 4 years following deferral by FFR in our high-risk population supports the safety of FFR-guided decision making for management of intermediate lesions.”

The Higher the FFR Value, the Better?

Earlier studies found lower cumulative rates of deferred revascularization over longer follow-up than the rate reported here, the investigators say. However, they point out, those cohorts were limited to elective cases, whereas in this study almost half of patients had ACS, making it a high-risk population. Moreover, results of the largest previous real-world study (Li J, et al. Eur Heart J. 2013;34:1375-1383) are consistent with the current findings.

This analysis shows an inverse relationship between FFR value and adverse cardiac events in deferred lesions, while another study found that the rate of adverse cardiac events declined for every 0.01 increase in FFR (Lavi S, et al. Catheter Cardiovasc Interv. 2007;70:525-531). Together, these data suggest that even an FFR value above the hemodynamic threshold can have a negative impact on the risk of subsequent events, the investigators say.

Dr. Singh and colleagues add that while a previous study linked a lower dose of intracoronary adenosine for FFR measurement with higher subsequent adverse cardiac events, the current study found no such association.

Possible Role for Preventive Measures

The investigators acknowledge that the risk prediction model requires validation in an independent patient sample but say that its use “may alert clinicians to a need for closer follow-up, optimized medical therapy, and intensified risk factor modification.” While cautioning that the benefit of any specialized strategy in this setting remains unknown, they suggest optimizing medical management following deferred PCI “may offer the best opportunity to prevent subsequent revascularization for lesions at a higher risk for [intervention].” In addition, because current smoking predicts subsequent intervention, aggressive smoking cessation might reduce the risk.

Since the study was conducted at a large tertiary referral center, the results may not be generalizable to other populations, however. A further limitation of the risk model, Dr. Singh and colleagues say, is that it uses patient and lesion characteristics ascertained at the time of FFR assessment, and patient management can vary over time, potentially changing the risk of intervention.

Source:
Depta JP, Patel JS, Novak E, et al. Risk model for estimating the 1-year risk of deferred lesion intervention following deferred revascularization after fractional flow reserve assessment. Eur Heart J. 2014;Epub ahead of print.

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