Coronary artery ectasia (CAE) is defined as localized or diffuse dilation of the coronary arteries that frequently co-exists with atherosclerotic coronary artery stenosis. Although our group identified an angiotensin-converting enzyme gene deletion polymorphism as a significant risk factor for CAE development, 1 Gulec S, Aras O, Atmaca Y, Akyurek O, Hanson NQ, Sayin T, Tsai MY, Akar N, Oral D. Deletion polymorphism of the angiotensin I converting enzyme gene is a potent risk factor for coronary artery ectasia. Heart 2003;89:213–214 Google Scholar the predisposing factors are still not fully understood. Isolated CAE, in which coronary artery stenosis, valvular heart disease, and other cardiac disorders are not present, comprises a small portion of the total of CAE cases, with an incidence of 0.1% to 0.79%. 2 Swaye P.S. Fisher L.D. Litwin P. Vignola P.A. Judkins M.P. Kemp H.G. Mudd J.G. Gosselin A.J. Aneurysmal coronary artery disease. Circulation. 1983; 67: 134-138 Crossref PubMed Scopus (804) Google Scholar , 3 Al-Harthi S.S. Nouh M.S. Arafa M. Al-Nozha M. Aneurysmal dilatation of the coronary arteries diagnostic patterns and clinical significance. Int J Cardiol. 1991; 30: 191-194 Abstract Full Text PDF PubMed Scopus (45) Google Scholar Angina pectoris (commonly exertional) is a frequent complaint of the disease. 4 Befeler B. Aranda M.J. Embi A. Mullin F.L. El-Sherif N. Lazzara R. Coronary artery aneurysms. Study of their etiology, clinical course and effect on left ventricular function and prognosis. Am J Med. 1977; 62: 597-607 Abstract Full Text PDF PubMed Scopus (253) Google Scholar , 5 Rath S. Har-Zahav Y. Battler A. Agranat O. Rotstein Z. Rabinowitz B. Neufeld H.N. Fate of nonobstructive aneurysmatic coronary artery disease angiographic and clinical follow-up report. Am Heart J. 1985; 109: 785-791 Abstract Full Text PDF PubMed Scopus (135) Google Scholar Recently, exercise-induced myocardial ischemia has been documented in isolated CAE, 6 Sayin T. Doven O. Berkalp B. Akyürek O. Gulec S. Oral D. Exercise induced myocardial ischemia in patients with coronary artery ectasia without obstructive coronary artery disease. Int J Cardiol. 2001; 78: 143-149 Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar , 7 Kruger D. Stierle U. Herrmann G. Simon R. Sheikhzadeh A. Exercise-induced myocardial ishemia in isolated coronary artery ectasia and aneurysms (“dilated coronaropathy”). J Am Coll Cardiol. 1999; 34: 1461-1470 Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar and further studies have suggested impaired epicardial flow as a possible cause of coronary insufficiency. 7 Kruger D. Stierle U. Herrmann G. Simon R. Sheikhzadeh A. Exercise-induced myocardial ishemia in isolated coronary artery ectasia and aneurysms (“dilated coronaropathy”). J Am Coll Cardiol. 1999; 34: 1461-1470 Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar , 8 Papadakis C.M. Manginas A. Cotileas P. Demopoulos V. Voudris V. Pavlides G. Foussas S.G. Cokkinos D.V. Documentation of slow coronary flow by the TIMI frame count in patients with coronary ectasia. Am J Cardiol. 2001; 88: 1030-1032 Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar Myocardial perfusion, however, has not yet been elucidated in CAE. Myocardial blush grade (MBG) has been introduced as a simple angiographic parameter to describe the effectiveness of microvascular perfusion after acute myocardial infarction. 9 van ‘t Hof A.W. Liem A. Suryapranata H. Hoorntje J.C. de Boer M.J. Zijlstra F. Angiographic assessment of myocardial reperfusion in patients treated with primary angioplasty for acute myocardial infarction;myocardial blush grade. Circulation. 1998; 97: 2302-2306 Crossref PubMed Scopus (1193) Google Scholar In the present study, we applied this technique to assess whether tissue level perfusion is altered in myocardial regions subtended by the ectatic coronary arteries without coexisting significant stenosis.