Impact of right atrial pressure on fractional flow reserve measurements comparison of fractional flow reserve and myocardial fractional flow reserve in 1,600 coronary stenoses

Objectives This study sought to assess the impact of a wide range of mean right atrial pressure (P_ra) on fractional flow reserve (FFR) measurements. Background FFR invasively assesses the ischemic potential of coronary stenoses. FFR is calculated as the ratio of mean distal coronary pressure (P_d) to mean aortic pressure (P_a) during maximal hyperemia. The P_ra is considered to have little impact if it is within normal range, so it is neglected in the formula. Methods In 1,676 stenoses of 1,235 patients undergoing left-right heart catheterization for ischemic (642 [52%]) or valvular heart disease (593 [48%]), the authors compared the FFR values calculated without accounting for P_ra (FFR= P_d/P_a) to the corresponding myocardial fractional flow reserve (FFR_myo) values accounting for P_ra (FFR_myo = P_d - P_ra/P_a - P_ra). Results The median P_ra was 7 (interquartile range [IQR]: 5 to 10) mm Hg with a maximum of 27 mm Hg. The correlation and agreement between FFR and FFR_myo was excellent (R² = 0.987; slope 1.096 ± 0.003). The median FFR (0.85; IQR: 0.78 to 0.91) was slightly but statistically significantly higher than the median FFR_myo (0.83; IQR: 0.76 to 0.90; p < 0.001) with a median difference of 0.01 (IQR: 0.01 to 0.02). Values of FFR above the cutoff of 0.80 provided an FFR_myo ≤0.80 in 110 (9%) stenoses. No FFR value above 0.80 provided an FFR_myo ≤0.75. Conclusions The difference between FFR and FFR_myo was minimal even in patients with markedly increased P_ra. FFR values above the gray zone (i.e., >0.80) did not yield values below the gray zone (i.e., ≤0.75) in any case, which suggests that the impact of right atrial pressure on FFR measurement is indeed negligible.