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Assessment of myocardial viability
1Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Insights
Noninvasive myocardial viability assessment helps identify hibernating heart muscle, guiding treatment for ischemic heart disease. Identifying viable heart muscle improves outcomes and survival after revascularization procedures.
Area of Science:
- Cardiology
- Nuclear Medicine
- Echocardiography
Background:
- Assessing myocardial viability is crucial for managing ischemic heart disease.
- Distinguishing hibernating from irreversibly injured myocardium guides therapeutic decisions.
- Left ventricular dysfunction is common in chronic ischemic heart disease and myocardial infarction.
Purpose of the Study:
- To review noninvasive techniques for assessing myocardial viability.
- To correlate myocardial viability with clinical outcomes after revascularization.
- To inform treatment strategies for patients with severe ischemic cardiomyopathy.
Main Methods:
- Single-photon-emission CT (SPECT) perfusion imaging (201Tl, 99mTc agents).
- Positron emission tomography (PET) for perfusion and glucose uptake.
- Low-dose dobutamine echocardiography for inotropic reserve.
- Contrast echocardiography for microvascular integrity.
Main Results:
- Increased viable myocardial segments correlate with improved left ventricular function.
- Viability assessment predicts improved heart failure symptoms, functional capacity, and survival post-revascularization.
- Patients with low viability undergoing surgery have higher mortality rates.
Conclusions:
- Noninvasive viability assessment is clinically valuable in ischemic heart disease.
- Viability dictates prognosis and response to revascularization.
- Coronary bypass surgery may benefit selected patients with severe cardiomyopathy and hibernating myocardium, even without angina.
Abstract:
The noninvasive assessment of myocardial viability has proved clinically useful for distinguishing hibernating myocardium from irreversibly injured myocardium in patients with chronic ischemic heart disease or recent myocardial infarction who exhibit marked regional and global left ventricular dysfunction. Noninvasive techniques utilized for detection of viability in asynergic myocardial regions include single-photon-emission CT perfusion imaging with 201Tl or one of the new 99mTc-labeled perfusion agents, positron emission tomographic imaging of perfusion and glucose uptake, low-dose dobutamine echocardiography for assessment of inotropic reserve, and contrast echocardiography for evaluation of microvascular integrity. The greater the number of viable myocardial segments by any of these techniques, the greater is the probability of improvement in regional and global left ventricular function, improvement in heart failure symptoms and functional capacity, and enhanced survival after revascularization. Patients with a decreased left ventricular ejection fraction and extensive myocardial viability treated medically have a high cardiac event rate. Similarly, patients with poor viability preoperatively who still undergo coronary bypass surgery have a high rate of early and late cardiac death or need for transplantation compared with patients with greater viability. Finally, some patients with severe ischemic cardiomyopathy referred for cardiac transplantation may have substantial zones of hibernation and may still be candidates for coronary bypass surgery, even in the absence of angina.