Measurement of coronary fractional flow reserve. Standard doses of intracoronary adenosine are insufficient to induce maximal hyperaemia

Abstract

Background: Induction of maximal hyperaemia is a prerequisite for a reliable estimation of fractional flow reserve (FFR) in a moderate coronary artery stenosis. Intracoronary adenosine is the most frequently used agent to achieve maximal hyperaemia. However, an insufficient dose of adenosine may induce only partial hyperaemia, thus artificially increasing the FFR values.
Aim: To assess the tolerability and effects on FFR value of increased doses of adenosine.
Methods: FFR was measured in 36 patients with 53 moderate coronary lesions. In order to induce maximal hyperaemia and assess FFR in the targeted coronary artery, intracoronary adenosine in a dose of 30 µg was administered twice (FFR30). Next, 60 µg of adenosine was tested twice (FFR60). In addition, in some patients with left coronary artery stenosis, 90 µg of adenosine was also injected (FFR90).
Results: No significant side effects were noted except a transient, self-terminating episode of a second degree atrio-ventricular block in one patient. The mean value of FFR30 was significantly higher than FFR60 (0.854±0.152 vs 0.836±0.162, p<0.001), and the mean difference between these two measurements was 0.018±0.036. In 29 (54.7%) evaluated lesions, FFR30 values were higher than FFR60; in 12 (22.6%) measurements the difference exceeded 0.02, and in 8 (15%) cases - 0.05. The use of 90 µg of adenosine did not further decrease FFR in any of the cases.
Conclusions: An increase of the adenosine dose from 30 µg to 60 µg was well tolerated and caused further decrease in the FFR values which may be of clinical importance in some patients. The use of 90 µg of adenosine did not further decrease FFR.