Original Title: Coronary Flow Reserve and Microcirculatory Resistance in Patients with Intermediate Coronary Stenosis. Reference: Joo Myung Lee, el al. J Am Coll Cardiol 2016; 67:1158-69

Courtesy of Dr. Carlos Fava.

Measuring fractional flow reserve (FFR) helps establish whether intermediate stenosis will generate ischemia, but it won’t help assess microcirculatory function. It has been shown that an alteration at that level generates ischemia and has a negative impact on evolution.

Patients presenting intermediate stenosis were analyzed by visual assessment (40%-70%) and FFR, coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) were measured in the same procedure.

Hyperemia was induced by intravenous infusion of adenosine (140 μg/kg/min) and FFR was an average of the three slowest cardiac cycles.
Cutoff values were ≤0.80 for FFR, ≤2 for CFR and ≥23U for IMRcorr .

Primary end point was a combination of all cause death, AMI and revascularization.

The study included 313 patients, 230 (73.5%) presenting FFR ≥0.80. These were divided into 4 groups: high CFR with low IMR, 61.3% (group A); high CFR with high IMR18.3% (B); low CFR with low IMR, 13.5% (C); low CFR with high IMR, 7% (D).

All 4 groups had similar clinical and angiographic characteristics.

Median follow up was 658 days and primary point incidence was 9.5%, 0%, 7% and 27.9% (p=0.002) for groups A, B, C and D respectively, a significantly higher events rate for the group with low CRF and high IMR (group D).

This was due to the higher rate of death, MI and revascularization; the latter was associated to a progression of stenoses documented by angiography and FFR.

Microvascular disease, multivessel disease and diabetes were primary end point predictors.

Conclusion
Coronary flow reserve and index of microcirculatory resistance improved risk stratification in patients with intermediate lesions and FFR≥0.80. Patients with low coronary flow reserve associated to a high index of microcirculatory resistance have better prognosis.

Commentary
At present, FFR is the “Gold Standard” for the functional assessment of coronary obstructions. This was shown in the FAME studies, where FFR≥0.80 stenoses had no impact in evolution at two years.

Microcirculatory alteration associated to intermediate stenoses documented by FFR presented more hard events and are associated to the progress of epicardial disease.

Courtesy of Dr. Carlos Fava.
Interventional Cardilogist
Favaloro Foundation – Buenos Aires.