SPECIAL SECTIONS: LETTER TO THE EDITOR
Transient ischemic dilation
Charles J. Hardebeck, MD, FACC
Division of Cardiology, University of Kentucky, 210 Thomas More Park, Crestview Hills, KY, USA
chardebeck{at}hotmail.com
Abidov et al. (1) note an increased cardiac event rate in follow-up of patients found to have transient ischemic dilation (TID) as the sole abnormality on stress myocardial perfusion single-photon emission computed tomography (SPECT). However, the finding of severe coronary disease in only a minority (5 of 20) of such patients is in contrast to previous reports (2,3), which conclude TID to be highly specific for severe coronary disease, and it suggests that there are alternate or additional mechanisms to that of balanced diffuse endocardial ischemia due to epicardial coronary stenosis.
Earlier experimental studies have demonstrated a decreased endocardial-to-epicardial flow ratio in response to adenosine (4,5), tachycardia (4), and hypotension (6), particularly in the presence of left ventricular hypertrophy (LVH) and elevated left ventricular end-diastolic pressure (LVEDP) (4–6), as well as coronary stenosis. In addition, redistribution of transmural perfusion would be expected to produce a more pronounced increase in the TID ratio in the presence of LVH, due to a greater subendocardial-to-subepicardial distance. One recent clinical report (7) associates TID, in the absence of focal perfusion defect, with hypertensive LVH.
The possibility that TID may represent a nonspecific marker of stress-induced subendocardial underperfusion by one or more of a number of possible mechanisms and may thus serve as a surrogate of various risk factors for a future cardiac event should be considered. As this phenomenon may not truly be "ischemic" nor represent genuine left ventricular dilation, the term "transient ischemic dilation" may be a misnomer.
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References
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- Abidov A, Bax JJ, Hayes SW, et al. Transient ischemic dilation ratio of the left ventricle is a significant predictor of future cardiac events in patients with otherwise normal myocardial perfusion SPECT. J Am Coll Cardiol. 2003;42:1818–1825[Abstract/Free Full Text]
- Weiss AT, Berman DS, Lew AS, et al. Transient ischemic dilation of the left ventricle on stress thallium-201 scintigraphy: a marker of severe and extensive coronary artery disease. J Am Coll Cardiol. 1987;9:752–759[Abstract]
- Mazzanti M, Germano G, Kiat H, et al. Identification of severe and extensive coronary artery disease by automatic measurements of transient ischemic dilation of the left ventricle in dual-isotope myocardial perfusion SPECT. J Am Coll Cardiol. 1996;27:1612–1620[Abstract]
- Duncker DJ, Ishibashi Y, Bache RJ. Effect of treadmill exercise on transmural distribution of blood flow in hypertrophied left ventricle. Am J Physiol. 1998;275:H1274–1282[Medline]
- Hittinger L, Mirsky I, Shen Y, et al. Hemodynamic mechanisms responsible for reduced subendocardial coronary reserve in dogs with severe left ventricular hypertrophy. Circulation. 1995;92:978–986[Abstract/Free Full Text]
- Harrison DG, Florentine MS, Brooks LA, et al. The effect of hypertension and left ventricular hypertrophy on the lower range of coronary autoregulation. Circulation. 1988;77:1108–1115[Abstract/Free Full Text]
- Robinson VJ, Corley JH, Merks DS, et al. Causes of transient dilatation of the left ventricle during myocardial perfusion imaging. AJR Am J Roentgenol. 2000;174:1349–1352[Free Full Text]
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References