What is the differential diagnosis of a regional wall motion abnormality?
A wall motion abnormality indicates a portion of myocardium that has abnormally reduced contractility. This reduced contractility usually occurs on the basis of previous or ongoing ischemia and suggests heart muscle that is acutely ischemic, infarcted, stunned, or hibernating. Acutely ischemic myocardium cannot contract properly because of inadequate blood flow and poor energy supply. Infarcted myocardium is nonviable, does not contract, and may eventually exhibit “paradoxical” motion with ballooning out during systole instead of thickening. When a portion of heart muscle remains viable after a temporary episode of acute ischemia, it can become “stunned,” where wall motion abnormality persists because of chemical changes in the myocardium that resolve over time. Finally, chronically ischemic myocardium can down-regulate its own contractility to match its energy demands with energy supply; this is termed “hibernating” and may signify tissue at risk for future infarction.