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The stunned and hibernating myocardium: a brief review
1Department of Medicine, University of Florida College of Medicine, Gainesville.
Insights
Stunned myocardium, viable but dysfunctional after reperfusion, differs from hibernating myocardium, chronically depressed but viable. Differentiation relies on wall motion, perfusion, and metabolism assessments.
Area of Science:
- Cardiology
- Myocardial Viability Assessment
Background:
- Stunned myocardium: viable heart muscle with prolonged dysfunction post-reperfusion.
- Hibernating myocardium: viable but chronically depressed heart muscle due to narrowed coronary arteries.
Purpose of the Study:
- Differentiate stunned from hibernating myocardium.
- Clarify clinical parameters for distinguishing myocardial conditions.
Main Methods:
- Analysis of clinical parameters: left ventricular (LV) wall motion, myocardial perfusion, and metabolism.
- Assessment of patient groups including acute infarction, angina, and post-revascularization.
Main Results:
- Stunned myocardium shows adequate perfusion and metabolism, with wall motion normalizing post-treatment.
- Hibernating myocardium presents reduced perfusion reversible with revascularization, and adequate metabolism.
Conclusions:
- LV wall motion, myocardial perfusion, and metabolism are key differentiators.
- Stunned myocardium recovers function over hours to weeks; hibernating myocardium recovers quickly after cause removal.
Definitions:
Stunned myocardium is viable myocardium salvaged by coronary reperfusion that exhibits prolonged postischemic dysfunction after reperfusion. Hibernating myocardium is ischemic myocardium supplied by a narrowed coronary artery in which ischemic cells remain viable but contraction is chronically depressed.
Clinical Evidence:
Stunned myocardium has been identified in the following patient groups: (1) thrombolysis or percutaneous transluminal coronary angiography (PTCA) in patients with acute evolving infarction; (2) unstable angina; (3) exercise-induced angina; (4) coronary artery spasm; (5) platelet aggregation or transient thrombosis of a coronary artery; (6) PTCA for chronic myocardial ischemia; and (7) immediately following coronary artery bypass graft (CABG). Evidence of hibernating myocardium (LV dysfunction) is found in the patient with severe coronary artery stenosis, even in asymptomatic patients at rest. Stunned myocardium returns to normal after a prolonged period of time (hours to weeks). Hibernating myocardium returns to normal function rather quickly if the cause is removed.
Differentiation:
Stunned myocardium can be differentiated from hibernating myocardium by three clinical parameters, namely, LV wall motion, myocardial perfusion, and myocardial metabolism. Stunned myocardium has abnormal wall motion that tends to normalize in response to inotropes and postextrasystolic potentiation. Perfusion is adequate and metabolism is also adequate. Hibernating myocardium also has abnormal wall motion, which normalizes after nitrates, inotropes, post extrasystolic potentiation (PESP), PTCA, or CABG. Myocardial perfusion is reduced but can be reversed with PTCA or CABG and metabolism is adequate.