CORRESPONDENCE: LETTERS TO THE EDITOR
Reply
Stuart T. Higano, MD, FACC,
Amir-Ali Fassa, MD and
Amir Lerman, MD, FACC*
* Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905 (Email: lerman.amir{at}mayo.edu).
We would like to thank Dr. Leesar for emphasizing the importance of adjunctive methods for evaluating indeterminate left main coronary artery (LMCA) disease with pressure wire and intravascular ultrasound techniques (IVUS). While several investigators have proposed "cut-off" values for both IVUS and fractional flow reserve (FFR) below which coronary artery bypass graft surgery (CABG) should be performed, we believe that the existing data do not definitively support such strict cut-off values. Studies to date have shown that patients with indeterminate LMCA disease deemed insignificant, either by IVUS or FFR, have a good outcome with a conservative approach without CABG. Conversely, patients with indeterminate LMCA disease deemed significant have good outcomes with CABG. However, these studies were non-randomized and, therefore, could not define unequivocal "cut-off" values. In the quoted study by Jasti et al. (1), an IVUS MLA of 5.9 mm2 predicted an FFR of 0.75 and clinical outcome. However, definitive outcome conclusions cannot be drawn from this study as it was also non-randomized and only 14 patients underwent revascularization.
Dr. Leesar pointed out that the distribution of plaque from the LMCA to the ostium of the left anterior descending (LAD) or circumflex artery is not uniform and that a single pullback from one of these vessels was not sufficient. However, the tomographic nature of IVUS imaging makes it ideal for imaging LMCA, including the bifurcation. The dual pullback method proposed has not been used in any prior published reports of LMCA IVUS. He also suggested the use of computerized planimetry on digitized images for more accurate measurements. However, essentially all IVUS measurements, including those in our study (2), are made using planimetric techniques on digital computer images, whether on-line or off-line. We agree that a manual pullback has limitations for assessing plaque severity. Conversely, because complications can occur during LMCA IVUS, including dissection or thrombosis, we utilize a brief procedure, interpreting the images during catheter advancement and quickly withdrawing if critical LMCA disease is identified. A motorized pullback can be undertaken only after critical LMCA disease is excluded, and is required for longitudinal or three-dimensional imaging.
Most would agree that indeterminate LMCA disease with an IVUS MLA <6.0 mm2 (or an FFR <0.75) should have CABG, and an IVUS MLA >7.5 mm2 should be treated conservatively. In the middle "grey" area, we should use our judgment, incorporating clinical features such as presenting symptoms, results of noninvasive functional testing, risk factor profile, and extent and type of disease on angiography and IVUS. We do not believe that any one "cut-off" value should be used in place of good clinical judgment.
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Footnotes
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Please note: Dr. Higano is currently affiliated with Town & Country Cardiovascular Group P.C., St. Louis, Missouri.
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References
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1. Jasti V, Ivan E, Yalamanchili V, Wongpraparot N, Leesar MA. Correlations between fractional flow reserve and intravascular ultrasound in patients with an ambiguous left main coronary artery stenosis Circulation 2004;110:2831-2836.[Abstract/Free Full Text]
2. Fassa AA, Wagatsuma K, Higano ST, et al. Intravascular ultrasound-guided treatment for angiographically indeterminate left main coronary artery disease J Am Coll Cardiol 2005;45:204-211.[Abstract/Free Full Text]
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