Physiological Basis and Long-Term Clinical Outcome of Discordance Between Fractional Flow Reserve and Coronary Flow Velocity Reserve in Coronary Stenoses of Intermediate Severity
Selected in Circulation Cardiovascular Interventions by M. Dobric
Tim P. van de Hoef, Martijn A. van Lavieren, Peter Damman, Ronak Delewi, Martijn A. Piek, Steven A.J. Chamuleau, Michiel Voskuil, José P.S. Henriques, Karel T. Koch, Robbert J. de Winter, Jos A.E. Spaan, Maria Siebes, Jan G.P. Tijssen, Martijn Meuwissen and Jan J. Piek
Circ Cardiovasc Interv. 2014 Apr 29. [Epub ahead of print]
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What is known
Discordance between fractional flow reserve (FFR) and coronary flow velocity reserve (CFVR) in coronary stenoses of intermediate severity is relatively frequently encountered – in approximately one third of cases. It is suggested that it comes from a divergent distribution of epicardial and microvascular involvement in coronary artery disease.
- Study involved 157 patients/stenoses in which revascularization was deferred.
- Follow-up was 11.7 years. MACE was defined as cardiac death, or acute myocardial infarction, or target vessel urgent revascularization.
- Discordant FFR and CFVR values were found in 30.6% and 36.9% of patients (using cut-offs <0.75 and ≤0.80, respectively). CFVR <2.0 indicated abnormal CFVR value.
- Discordance between FFR and CFVR was shown to be related to the magnitude of microvascular resistance.
- Overall, discordance between FFR and CFVR was associated with a higher MACE rate compared with concordant normal FFR and CFVR results.
- The combination of normal FFR and abnormal CFVR was associated with a higher MACE rate compared to patients with concordantly normal values.
- An abnormal FFR with a normal CFVR was associated with equivalent clinical outcome compared to concordantly normal values.
- The MACE rate associated with a normal FFR and abnormal CFVR was significantly higher than that associated with an abnormal FFR and normal CFVR.
This study suggests that there is important prognostic information to be gathered from simultaneous assessment of FFR and CFVR in intermediate coronary stenosis. CFVR is usually criticized for being dependent on resting coronary flow, which is related to baseline hemodynamic and myocardial contractility. This obvious physiological limitation makes CFVR an unreliable index that cannot govern revascularization decision process. Despite that, there are some fundamental microcirculatory properties that CFVR can depict, that can provide useful prognostic information. Current study demonstrates that impaired CFVR is adverse prognostic factor even in cases of normal FFR, and that normal CFVR suggests good long-term prognosis regardless of FFR (in patients with deferred revascularization). Because this discordance is frequently encountered (in approximately one third of cases), and has significant prognostic impact, assessment of CFVR may be the part of routine/optimal physiological evaluation of stable coronary artery disease. Finally, CFVR may be even assessed noninvasively, by the means of transthoracic echo, thus easily providing important information.