Key result
During myocardial ischemia, decreases in subendocardial blood flow are disproportionately large, leading to a fall in the subendocardial to subepicardial flow ratio.
Highlights the physiological vulnerability of the subendocardium during myocardial ischemia and the importance of the inner:outer flow ratio as a sensitive marker.
Subendocardial vulnerability during ischemia warrants attention in risk assessment; leaves open whether the flow ratio should guide interventions.
creases with the severity of the ischemia.Research by Griggs and Nakamura,'0 Hoffman,1'12 Buckberg et al,13 and others,14'15 demonstrated that the subendocardial myocardium is especially vulner- able to acute decreases in CAP.Thus, during ischemia, decreases in subendocardial blood flow are disproportionately large compared with the remain- der of the left ventricular wall, and the ratio of subendocardial to subepicardial flow (inner: outer ratio) falls, sensitively reflecting ischemia.The imbal- ance is exaggerated by excessive myocardial demand, and a fall in the inner: outer ratio can even be provoked without coronary stenosis if metabolic de- mand is excessive.13It should follow and has been shown that during ischemia, flow reserve in the subendocardium is less than that in the subepicardial zone.16Collateral development may ameliorate the inner: outer imbalance somewhat in chronic states.
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Bristow et al. (1991) conducted a review in Myocardial ischemia. Myocardial ischemia was evaluated on Subendocardial to subepicardial flow ratio. During myocardial ischemia, decreases in subendocardial blood flow are disproportionately large, leading to a fall in the subendocardial to subepicardial flow ratio.
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