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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Stunned: prolonged myocardial contractile dysfunction after a brief period of absent or reduced blood flow

  • Hibernating: myocardial contractile dysfunction associated with chronic reduced blood flow that reverses with revascularization

  • Imaging evidence of myocardial viability in areas of reduced myocardial contractility:

    • – Absence of thin scarred myocardial segment on echocardiography

    • – Wall motion response to dobutamine infusion

    • – Metabolic activity but reduced perfusion on positron emission tomography scan

    • – Lack of late gadolinium enhancement on cardiac MRI

GENERAL CONSIDERATIONS

  • Affects both systolic and diastolic function

  • Stunned myocardium recognized by persistent wall motion abnormalities even after chest pain, ST-segment deviation, and regional perfusion have recovered

  • Lack of recovery after a few weeks suggestive of true infarction or scar formation

  • Hibernating myocardium is recognized by improvement of left ventricular function after revascularization of chronic ischemia

  • Hibernation related to chronically reduced myocardial perfusion

  • Recovery of function may occur over days to weeks in both situations

  • Transient improvement occurs in both situations with inotropic stimulation

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Stunned myocardium:

    • – Persistent shortness of breath after an infarction despite evidence of reperfusion

    • – A similar situation may occur with cardioplegia during cardiopulmonary bypass (lack of recovery after a few weeks suggests true infarction)

  • Hibernation:

    • – Persistent dyspnea in chronic coronary artery disease

PHYSICAL EXAM FINDINGS

  • Hypotension may be present

  • S3 may be present

  • Occasionally an S4 may be present

DIFFERENTIAL DIAGNOSIS

  • Stunned: acute ischemia with compromised blood flow

  • Hibernating: infarcted myocardium

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • CBC, brain natriuretic peptide, troponin

ELECTROCARDIOGRAPHY

  • ECG may show infarction or ischemia

IMAGING STUDIES

  • Resting echocardiogram to evaluate left ventricular function after adequate revascularization or reperfusion

  • Thinned hyperechoic and akinetic wall segment indicates scar (nonviable)

  • Technetium-99m sestamibi single-photon emission cardiac tomography (SPECT) stress imaging for regional myocardial ischemia (presumably due to reduced perfusion)

  • Dobutamine echocardiogram: improvement in function in areas of resting regional wall motion at low doses, followed at higher doses by deterioration due to ischemia, so-called biphasic response

  • Positron emission tomography (PET):

    • – Perfusion: 13NH3-labeled ammonia, 15O2-labeled water, and 82Rb-labeled PET

    • – Metabolism: fluorodeoxyglucose PET

    • – Reduced perfusion and metabolism suggest infarction (matched defects)

    • – Reduced perfusion with intact metabolism (flow metabolism mismatch) suggests viable or hibernating myocardium

  • Cardiac magnetic resonance

    • – Myocardial late gadolinium uptake indicates myocardial scar (nonviable)

DIAGNOSTIC PROCEDURES

  • Coronary angiography to define anatomy in hibernation before revascularization

TREATMENT

CARDIOLOGY REFERRAL

  • All patients should be evaluated by a cardiologist

HOSPITALIZATION ...

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