Original Title: Impact of the Right Atrial Pressure on Fractional Flow Reserve Measurements Comparison of Fractional flow Reserve and Myocardial Fractional flow Reserve in 1600 Coronary Stenosis. Reference: Toth G, et al. JACC Cardiovasc Interv. 2016 Feb 12. Epub ahead of print.

Courtesy of Dr. Guillermo Migliaro.

Fractional Flow Reserve (FFR) is the gold standard for the invasive functional assessment of chronic heart disease.

FFR is defined as the ratio between the maximum blood flow in a stenotic coronary artery and the theoretical maximum flow in a normal coronary artery.

In practical terms, the FFR is calculated as the ratio of mean distal coronary pressure (Pd), measured with the pressure wire, to mean aortic pressure (Pa), measured with the guiding catheter, during maximum hyperemia chemically induced with adenosine.

The formula is FFR= Pd/Pa. This formula is a simplification of myocardial fractional flow reserve (FFRmyo) that includes right atrial pressure (RAP), where FFRmyo = Pd-RAP/Pa-RAP. Generally low, RAP is eliminated, which results in the FFR formula.

The aim of this study was to assess the impact of right atrial pressure in FFR values.

It included 1678 stenoses (lesions between 30 and 90%) in 1235 patients undergoing left-right heart catheterization and compared FFR to FFRmyo values.

RAP was 7 mmHg (5-10 mmHg) with a maximum of 27 mmHg. The correlation between FFR and FFRmyo was excellent (R²=0.907; slope 1.096±0.003). Median FFR was 0.85 (0.78 to 0.91) and median FFRmyo was 0.83 (0.76 to 0.93) (p<001). The median difference between both methods was 0.01.

Out of 1146 > 0.80 FFR stenoses, there were no <0.75 FFRmyo lesions. 9% of these were <0.80 FFRmyo. In this subgroup, the difference between FFR and FFRmyo was 0.02.

Conclusion
Differences between FFR and FFRmyo are minimal, even in patients with markedly increased RAP, and values above the grey zone did not yield values below the grey zone (FFRmyo< 0.75). This suggests that the impact of right atrial pressure is indeed negligible.

Editorial Comment
This is an observational study with an interesting number of patients that shows FFR is a reliable value, even in the context of increased right atrial pressure, as in cardiac failure.

Courtesy of Dr. Guillermo Migliaro.