CORRESPONDENCE: LETTERS TO THE EDITOR
Intravascular Ultrasound for the Assessment of an Ambiguous Left Main Coronary Stenosis
Massoud A. Leesar, MD*
* Division of Cardiology, University of Louisville, Louisville, KY 40292 (Email: malees01{at}louisville.edu).
In a recent issue of the Journal, Fassa et al. (1) reported that there are currently no intravascular ultrasound (IVUS) criteria to determine the significance of a left main coronary artery (LMCA) stenosis. Recently, we demonstrated that the use of fractional flow reserve (FFR) as the "gold standard," an IVUS minimal lumen diameter and minimal lumen area (MLA) of 2.8 mm and 5.9 mm2, respectively, strongly predicted the physiological significance of a LMCA stenosis (2). In contrast, an MLA cut-point of 7.5 mm2, as reported by Fassa et al. (1), to determine the significance of an LMCA stenosis is a fairly arbitary number that has not been validated with physiological studies.
In addition, some methodological flaws exist in the Fassa et al. (1) study, which are as follows: 1) Because the distribution of plaque from the LMCA to the ostium of the left anterior descending (LAD) or left circumflex (LCx) is not uniform, thereby the pullback of IVUS from either the LAD or the LCx alone was not sufficient to determine the significance of the LMCA stenosis in one-third of patients who had distal LMCA stenosis; 2) the investigators performed quantitative IVUS analyses by planimetry, which is based on visual estimation. In contrast, the use of computerized planimetry on digitized images is a more accurate technique to assess the significance of an LMCA stenosis. Furthermore, the authors performed manual IVUS pullback in some patients; however, quantitative IVUS measurements in such cases cannot be performed accurately because it is inherent with manual IVUS pullback that some of the images with the tightest frames could be missed during pullback; and 3) a comparison of a long-term outcome between group D (114 patients) and group B (12 patients) is not legitimate. Moreover, FFR was >0.75 in 25% of the group B patients, and that does not account for a poor outcome. Other factors such as advanced age or comorbidities rather than the LMCA stenosis might have contributed to the poor outcome in the group B patients.
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1. 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]
2. Jasti V, Ivan E, Yalamanchili V, Wongpraparut 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]
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