Use of fractional flow reserve and intravascular ultrasonography to evaluate ambiguous left main coronary artery stenosis.

Because angiography provides only a 2-dimensional image, it is an imperfect tool for accurately evaluating left main coronary artery stenosis. Additional methods, such as fractional flow reserve evaluation and intravascular ultrasonography, are more frequently being used to gauge the physiologic significance of angiographically ambiguous left main coronary artery stenosis. Previous studies have shown that a fractional flow reserve cutoff value of less than 0.75 indicates a need for surgical revascularization. It has been suggested that a fractional flow reserve value of 0.75 to 0.80 constitutes a "gray zone." Indeed, the management of patients who have angiographically ambiguous left main coronary artery disease and a fractional flow reserve value of 0.75 to 0.80 is not well established.Herein, we describe the cases of 3 patients whose fractional flow reserve values suggested functionally insignificant stenosis, but in whom intravascular ultrasonography showed substantial narrowing-the latter prompting surgical revascularization instead of medical management. All 3 patients underwent revascularization with good outcomes. Further studies are needed to investigate the role of intravascular ultrasonography in determining the severity of left main coronary artery stenosis and the preferred management thereof. Also warranting further investigation is the possible revision of the fractional flow reserve cutoff values that currently indicate significant stenosis of the left main coronary artery.