Flow-function relationship in hibernating and stunned myocardium

The red line demonstrates the relationship between the amount of myocardial blood flow and left ventricular systolic function (flow-function relationship). When myocardium is operating below this line, function is disproportionately depressed relative to flow and when it is above the line, function exceeds blood flow and ischemia is likely to result. Chronically hypoperfused myocardium, resulting from an epicardial stenosis that restricts basal coronary flow, produces hibernation (H). In comparison, stunning (S), resulting from repetitive bouts of ischemia, occurs when the stenosis severely limits flow reserve but not basal coronary flow. Small variations in blood flow may result in a change in myocardial state, between H and S, without any appreciable change in systolic function. Following inotropic stimulation, myocardium operating at both H and S will increase systolic function without a substantial change in blood flow (A and B, respectively). As a result, the two situations cannot be reliably distinguished by stress echocardiography.