FAQ: What Is Hibernating Heart Muscle?

The Importance of Hibernating Myocardium

Cardiac MRI
Cardiac MRI. BSIP/UIC/Getty Images

Q. My husband has heart failure because of his coronary artery disease.  The first cardiologist we saw told him that bypass surgery wouldn’t do any good because the blocked artery is supplying heart muscle that is already dead.  But the second cardiologist says it’s possible the heart muscle isn’t permanently damaged, but just “hibernating.”  He says that bypass surgery might allow the muscle to “wake up,” and his heart failure to improve. What can you tell me about hibernating heart muscle, and do you think the second cardiologist might be right?


The concept of “hibernating myocardium” (myocardium means heart muscle) still seems to be a foreign idea to some doctors - but it should not be. In some, cases non-functional heart muscle that appears to be dead is actually still viable, and can be “revived” if it blood supply is restored.

According to the way many doctors think about coronary artery disease (CAD), heart muscle tissue functions normally as long as there is sufficient blood flow. If the blood flow becomes insufficient to meet the needs of the heart muscle (for instance, when a person with CAD begins exercising), the muscle becomes transiently ischemic (starved for oxygen), and angina may occur. But either the ischemia would soon go away (because, for instance, the victim would stop exercising), or the ischemia would persist until a myocardial infarction (death of heart muscle) occurred.

So classically, the myocardium supplied by a diseased coronary artery can exist in one of three states: normal, ischemic, or dead.

But it turns out heart muscle might also persist in a fourth state, a state referred to as hibernation.

What Is Hibernating Myocardium?

Hibernating myocardium is just what it sounds like. Like a bear hibernating through the winter, despite all appearances hibernating heart muscle is not dead, but rather has just assumed a “dormant” state.

  It no longer functions normally - it does not contract with each heartbeat, and is not contributing to the work of the heart.

But neither is it dead.  It is merely in a state of self-protective inactivity.  It has shut down every one of its functions that is not immediately critical to its staying alive.

Heart muscle may enter a state of hibernation when the CAD is severe enough to produce ischemia that is chronic and relatively constant, rather than the more typical ischemia that comes and goes (which we see in most people with angina).  So, essentially, the heart muscle is never really getting enough blood flow to function normally, but it is - just barely - getting enough blood flow to stay alive.

Why Is Hibernating Myocardium Important?

Hibernating heart muscle is still potentially viable. This means that if its blood supply can be restored – through bypass surgery or stenting – there’s a reasonably good chance the hibernating myocardium can “wake up,” and begin once again contributing to cardiac work.

In a person with heart failure, this increased cardiac work capacity might make all the difference.

It sounds like the second cardiologist saw evidence that your husband may have hibernating myocardium, and that opening up one or more of his coronary arteries with bypass surgery might allow at least a portion of his heart muscle to begin functioning again.

There are special tests that cardiologists can do to help differentiate hibernating myocardium from heart muscle that is non-viable (that is, dead), including MRI studies and special echocardiographic testing.  Since this kind of testing is non-invasive and essentially risk-free, pursuing the possibility of hibernating myocardium would seem to be entirely reasonable in your husband’s case.


Ausma, J, Sehaart, G, Thone, F, et al. Chronic ischemic viable myocardium in man: Aspects of dedifferentiation. Cardiovasc Pathol 1995; 4:29.

Rahimtoola SH. The hibernating myocardium in ischaemia and congestive heart failure. Eur Heart J 1993; 14 Suppl A:22.

Kim SJ, Peppas A, Hong SK, et al. Persistent stunning induces myocardial hibernation and protection: flow/function and metabolic mechanisms. Circ Res 2003; 92:1233.

Rahimtoola SH, La Canna G, Ferrari R. Hibernating myocardium: another piece of the puzzle falls into place. J Am Coll Cardiol 2006; 47:978.

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