OBJECTIVES This study was performed to evaluate the feasibility of the physiologic assessment of jailed side branches using fractional flow reserve (FFR) and to compare the measured FFR with the stenosis severity assessed by quantitative coronary angiography (QCA).

BACKGROUND It is not well-known which side branches should be treated after stent implantation at main branches and how to assess the functional significance of these lesions.

METHODS Ninety-seven jailed side branch lesions (vessel size > 2.0 mm, percent stenosis > 50% by visual estimation) after stent implantation at main branches were consecutively enrolled. The FFR was measured using a pressure wire at 5 mm distal and proximal to the ostial lesion of the jailed side branch.

RESULTS The FFR measurement was successful in 94 lesions. Mean FFRs were 0.94 +/- 0.04 and 0.85 +/- 0.11 at the main branches and jailed side branches, respectively. There was a negative correlation between the percent stenosis and FFR (r = -0.41, p < 0.001). However, no lesion with < 75% stenosis had FFR < 0.75. Among 73 lesions with > or = 75% stenosis, only 20 lesions were functionally significant.

CONCLUSIONS The FFR measurement in jailed side branch lesions is both safe and feasible. Quantitative coronary angiography is unreliable in the assessment of the functional severity of jailed side branch lesions, and measurement of FFR suggests that most of these lesions do not have functional significance.