Key result
In an ovine model of coronary occlusion, 1 hour of ischemia resulted in greater infarct size in the midmyocardium (90%) compared to the subendocardium (76%, P=0.004).
Absolute Event Rate: 90% vs 76%
p-value: p=0.004
In a collateral-deficient ovine model, the midmyocardium is the most susceptible region to ischemic injury, challenging the traditional subendocardial-to-subepicardial wavefront concept of infarct evolution.
Challenges subendocardial vulnerability dogma in ischemia; leaves open applicability to human reperfused infarction.
It is widely accepted that, during acute coronary occlusion, ischemic cell death progresses from the subendocardium to the subepicardium in a wavefront fashion. This concept, which implies that the subendocardium is the most susceptible myocardial region to ischemic injury, was established using a canine model with an extensive system of subepicardial coronary collaterals. In humans, particularly in those with coronary artery disease, there is a wide range in the distribution and functional capacity of the collateral circulation, which may affect the pattern of infarct evolution. Using an ovine model with a limited system of preformed subendocardial coronary collaterals, we characterized the effect of increasing lengths of ischemia on regional blood flow and infarct size in three regions of the ventricular wall: subendocardium, midmyocardium, and subepicardium. Our results demonstrate that the myocardium and microvasculature in these three regions are equally susceptible to injury after 45 min of ischemia. When ischemic time is increased to 1 h, infarct size in the midmyocardium (90 +/- 2%) is greater than in the subendocardium (76 +/- 4%, P = 0.004) and subepicardium (84 +/- 3%, P = 0.13). Microvascular dysfunction as assessed as a percentage of baseline flow is also greater in the midmyocardium (14 +/- 5%) compared with the subendocardium (20 +/- 3%, P = 0.23) and subepicardium (51 +/- 9%, P = 0.007). These findings suggest that, in subjects with a limited system of coronary collateral circulation, the midmyocardium is the most susceptible myocardial region to ischemia and the subendocardium is the most resistant. Myocardial viability during coronary occlusion appears to be primarily determined by the distribution and functional capacity of the collateral circulation.
No takes yet. Share an insight, caveat, or question.
Leshnower et al. (2007) studied Acute coronary occlusion. 1 hour of ischemia vs. Subendocardium and subepicardium regions was evaluated on Infarct size (p=0.004). In an ovine model of coronary occlusion, 1 hour of ischemia resulted in greater infarct size in the midmyocardium (90%) compared to the subendocardium (76%, P=0.004).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: