The letter by Vieras and Alter questions the choice of an angiographic lesion of 50% reduction in luminal diameter (equivalent to 75% reduction of the cross-sectional area pathologically) of the coronary artery. This has been a commonly accepted standard for several studies.1,2 Other studies have used a more stenotic lesion.3 We agree that further evaluation of the functional importance of an obstructive lesion is necessary, including degree of reduction, geometric shape, length, and multiplicity.
There have been several reports in the literature directed at this problem.4-6 However, the major point in the article was to emphasize the observer variability of interpreting angiograms. It is almost certain, regardless of the degree of angiographic lesion chosen, that there would be a noteworthy interobserver variability.7
Murphy ML, Galbraith JE, de Soyza N. Coronary Angiograms and Myocardial Scintigraphy-Reply. JAMA. 1979;241(23):2505. doi:10.1001/jama.1979.03290490016011