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Revisiting the Historical Origins of Clinically Meaningful Coronary Artery Obstruction

      To the Editor:
      As part of a recent informative editorial on the significance of nonobstructive coronary artery disease, Rumberger
      • Rumberger J.A.
      Coronary artery disease: a continuum, not a threshold.
      reviewed the historical origins of the 50% coronary stenosis standard for the definition of myocardial ischemia and the relationship of percentage stenosis to coronary flow reserve and fractional flow reserve. I believe some corrections are warranted.
      Rumberger repeated the commonly stated but incorrect assumption that the origin of the 50% stenosis threshold is attributable to the landmark 1974 article by Gould et al.
      • Gould K.L.
      • Lipscomb K.
      • Hamilton G.W.
      Physiological basis for assessing critical coronary stenosis.
      The origin of the 50% coronary stenosis standard antedates the Gould article and was adopted in 1969 as the threshold for intervention by the VA Cooperative Study, the first major randomized trial of bypass surgery.
      Veterans Administration Cooperative Study of Surgery for Coronary Arterial Occlusive Disease, III: methods and baseline characteristics, including experience with medical treatment. By the Veterans Administration Cooperative Group for the Study of Surgery for Coronary Arterial Occlusive Disease.
      Even before this, in 1966, a 50% or greater diameter stenosis was identified as indicating a “severe” arteriographic narrowing by Sones' group at the Cleveland Clinic and was subsequently used and published as the cutoff value for bypass surgery when introduced by that institution.
      • Rosenthal R.L.
      The 50% coronary stenosis.
      The original Gould et al
      • Gould K.L.
      • Lipscomb K.
      • Hamilton G.W.
      Physiological basis for assessing critical coronary stenosis.
      article specifically indicated that a stenosis of “45 to 50 percent by diameter probably does not impair coronary flow reserve in man.” In the text, they were careful to indicate that coronary flow reserve begins to decline at a 30% stenosis but that a 65% to 95% stenosis is required to cause marked impairment of coronary flow reserve. Nor is the Gould et al
      • Gould K.L.
      • Lipscomb K.
      • Hamilton G.W.
      Physiological basis for assessing critical coronary stenosis.
      article the origin of the 70% stenosis standard, which was adopted by the Coronary Artery Surgical Study in 1973,
      CASS Principal Investigators and their Associates
      Coronary Artery Surgery Study (CASS): a randomized trial of coronary artery bypass surgery. Survival data.
      before the publication of the Gould et al report. The Gould et al
      • Gould K.L.
      • Lipscomb K.
      • Hamilton G.W.
      Physiological basis for assessing critical coronary stenosis.
      article, although transformational for many fields, is not responsible for the adoption of the 50% or 70% stenosis threshold for ischemia.
      Rumberger
      • Rumberger J.A.
      Coronary artery disease: a continuum, not a threshold.
      also indicated that a 70% coronary stenosis has become “the de facto stenosis measurement supported by fractional flow reserve data.” To the contrary, the major lesson of coronary flow reserve and fractional flow reserve research is that it is not possible to determine the functional significance of a coronary stenosis on the basis of percentage stenosis. Only one-third of narrowings within a stenosis range of 50% to 70% display provokable myocardial ischemia by fractional flow reserve.
      • Tonino P.A.
      • Fearon W.F.
      • De Bruyne B.
      • et al.
      Angiographic versus functional severity of coronary artery stenosis in the FAME study: fractional flow reserve versus angiography in multivessel evaluation.

      References

        • Rumberger J.A.
        Coronary artery disease: a continuum, not a threshold.
        Mayo Clin Proc. 2017; 92: 323-326
        • Gould K.L.
        • Lipscomb K.
        • Hamilton G.W.
        Physiological basis for assessing critical coronary stenosis.
        Am J Cardiol. 1974; 33: 87-94
      1. Veterans Administration Cooperative Study of Surgery for Coronary Arterial Occlusive Disease, III: methods and baseline characteristics, including experience with medical treatment. By the Veterans Administration Cooperative Group for the Study of Surgery for Coronary Arterial Occlusive Disease.
        Am J Cardiol. 1977; 40: 212-225
        • Rosenthal R.L.
        The 50% coronary stenosis.
        Am J Cardiol. 2015; 115: 1162-1165
        • CASS Principal Investigators and their Associates
        Coronary Artery Surgery Study (CASS): a randomized trial of coronary artery bypass surgery. Survival data.
        Circulation. 1983; 68: 939-950
        • Tonino P.A.
        • Fearon W.F.
        • De Bruyne B.
        • et al.
        Angiographic versus functional severity of coronary artery stenosis in the FAME study: fractional flow reserve versus angiography in multivessel evaluation.
        J Am Coll Cardiol. 2010; 55: 2816-2821

      Linked Article

      • Coronary Artery Disease: A Continuum, Not a Threshold
        Mayo Clinic ProceedingsVol. 92Issue 3
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          In this issue of Mayo Clinic Proceedings, Wang et al1 have substantially advanced our understanding of the prevalence, clinical importance, and long-term prognosis of nonobstructive coronary artery disease (CAD). They performed a detailed meta-analysis, involving a final sample size exceeding 1 million patients, using data from published databases assessing CAD by invasive coronary angiography or coronary computed tomographic (CT) angiography. The core databases spanned a 15-year period, and the authors specifically selected patients with nonobstructive disease (defined as ≤50% stenosis) and further stratified the data as representing mild CAD (≥20% to ≤50% stenosis) or no CAD (0% or <20% stenosis).
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      • In Reply—Revisiting the Historical Origins of Clinically Meaningful Coronary Artery Obstruction
        Mayo Clinic ProceedingsVol. 92Issue 8
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          First, I sincerely thank Rosenthal1 for his correspondence letter regarding my prior editorial.2 We all continue to learn, and as a student of medical history I am embarrassed that I was not aware of his excellent 2015 commentary on “The 50% Stenosis.”3 In that article, Rosenthal acknowledged the commonly held physiologic studies by Gould et al4 as one of the original investigations on the severity of percent stenosis and coronary hemodynamics; I now stand corrected on the true origins of the clinical use of the 50% stenosis threshold.
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