Hibernating Myocardium and Stunned Myocardium

What is hibernating myocardium?

Hibernating myocardium occurs when a region of your heart muscle stops working because there’s not enough blood flow. It basically goes to “sleep” and stops contracting. This process of hibernation can happen over months and even years.

In this state, your heart muscle switches from using predominantly fatty acids to contract to using glucose to keep the cells alive. It doesn’t have enough energy supply to contract, so a hibernating muscle can’t help your heart pump blood.

What is a stunned myocardium?

This condition is more rapid and occurs over minutes or hours when the supply of blood or nutrients to your heart muscle suddenly drops or stops altogether. Your heart muscle goes into a “stunned” state where it stops contracting. This can continue even after your surgeon restores blood flow to your heart by opening the vessel via a stent, balloon or clot-dissolving procedure. It usually takes days or weeks for the heart muscle in the area to be able to contract again.

How is a stunned or hibernating myocardium different from a heart attack?

In the most severe cases of coronary artery disease, plaque buildups block one or more arteries, causing the muscle cells to die. This cell death is commonly known as a heart attack. After heart muscle cells die, they’re replaced with scar tissue. This tissue can’t support the pumping action of your heart, putting you at risk of heart failure.

A stunned or hibernating myocardium is a temporary condition. Myocardial tissue remains alive even though it’s not fully functioning. The hibernating heart tissue might regain function if blood and oxygen supply improves.

What causes a hibernating myocardium?

Hibernating myocardium occurs in people with severe coronary artery disease. This condition causes waxy buildups (plaque) that clog arteries supplying blood to the heart. When an artery is almost entirely clogged, the myocardium doesn’t receive enough oxygen and nutrients to both stay alive and contract to help your heart pump blood. So, it hibernates to stay alive and conserve energy for basic cell functions.

What causes a stunned myocardium?

Myocardial stunning can occur from treatment of coronary artery disease. Treatment restores blood flow, but some areas of heart muscle don’t recover right away. Stunned myocardium can also result from other conditions, including:

• Seizures, episodes of abnormal electrical activity in your brain.
• Stress cardiomyopathy.
• Stroke.
• Subarachnoid hemorrhage.

What are the symptoms of a stunned or hibernating myocardium?

Because the condition only affects a portion of heart tissue or most of your heart muscle, the symptoms overlap with those of heart failure and include shortness of breath, chest pain and leg swelling.

How is hibernating myocardium diagnosed?

This condition requires sophisticated testing. These assessments distinguish between a stunned or hibernating myocardium that can be revived and scar tissue that can’t.

Care may include:

• Dobutamine stress echocardiogram uses medication to stimulate your heart as exercise would. Your cardiologist can measure how your heart contracts at rest, and with increasing doses of medication (dobutamine). If the medication improves the ability of your heart muscle to contract, you have a stunned or hibernating myocardium. If the muscle doesn’t contract as the medication dose increases, you have a scarred or dead myocardium.
• Cardiac MRI uses a powerful magnet and radio waves to provide more detailed views of your heart muscle. The appearance and thickness of your heart muscle under this powerful magnet allow healthcare providers to accurately determine which tissues are scarred (dead), normal and hibernating or stunned.
• Cardiac positron emission tomography (PET) scan uses a safe level of radioactive substance and a special camera. It shows areas where your heart muscle is working normally or where there’s scarred or dead tissue.

Is a hibernating myocardium reversible?

The condition is reversible with treatment. You may need a procedure to restore blood flow. These include:

• Angioplasty uses a long thin tube (catheter) to access clogged blood vessels supplying the hibernating tissue. A balloon at the tip expands to push plaque deposits out of the way. The procedure may include placing a hollow mesh device (stent) in the artery to keep it open.
• Coronary artery bypass surgery (CABG) is a surgical procedure. It uses a healthy blood vessel from another area of the body to reroute blood flow around the blockage.

After recovering from these procedures, your care may also include cardiac rehabilitation. This medically supervised exercise program helps you gain strength and fitness while adopting heart-healthy habits.

What treatments are available for a stunned myocardium?

Guideline-directed treatment for a stunned myocardium is similar to the standard treatment for coronary heart disease and heart failure. It may include aspirin, beta-blockers, statins and ACE inhibitors or angiotensin II receptor blockers.

How can I prevent a stunned or hibernating myocardium?

You can lower your risk by taking good care of your heart. Your healthcare provider may recommend statins to lower cholesterol or daily aspirin to prevent blood clots. There are many available risk calculators through the American College of Cardiology or European Society of Cardiology to calculate your individual risk score and need for treatment. But, if you already have established heart disease, you should discuss your risk with your healthcare provider. Guideline-directed medical therapy in these conditions has been shown to significantly reduce your risk for heart attacks, heart failure and even death.

What is the prognosis for a hibernating or stunned myocardium?

The prognosis (outlook) for people with this condition depends on many factors — including how much pumping function you’ve lost, whether you’re taking your medications as prescribed and if you’re a candidate for angioplasty/stent or bypass surgery.

People with coronary artery disease have a lifetime risk of future heart issues. Myocardial tissue may hibernate again if you experience another blockage in your coronary arteries.

A note from Cleveland Clinic

Hibernating myocardium occurs in people with coronary artery disease. It happens when a severely clogged coronary artery limits blood flow to heart muscle tissue over a long period of time. A stunned myocardium occurs when blood flow is reduced suddenly. If the blood flow is restored, your heart muscle should regain its ability to contract over a relatively short period of time. Both conditions are potentially reversible. It’s essential to take good care of your heart to try to prevent these conditions from coming back.