Assessment of myocardial viability by PET

Viability assessment has a key role in the management of patients with ischemic heart disease. Positron emission tomography (PET) is a unique modality that evaluates myocardial viability via assessing the tissues metabolic and perfusion properties. The mainstay of metabolic imaging relies on glucose metabolism using fluorodeoxyglucose, a radiolabeled glucose analog. Mismatch in perfusion metabolism data denotes hibernating myocardium with a high likelihood of functional recovery following revascularization. Matched absence or reduction in perfusion metabolism data represents scar with a low likelihood of functional recovery following revascularization. This review will focus on PET radiotracers and techniques used to assess myocardial viability.

Single-center studies have shown that patients with PET mismatch undergoing bypass grafting had improved survival compared with those on medical therapy. In addition to survival benefit, the patients who underwent PET-guided revascularization had significant improvement in angina and heart failure symptomology. Recent technological advancements in the field of PET-magnetic resonance (MR) opens a new frontier in the field of advanced imaging as it combines anatomical, functional, tissue characterization, and metabolic perfusion data obtained in one setting. The incremental value of PET/MRI is best established in diagnosing and monitoring disease activity in patients with cardiac sarcoidosis and occult malignancies, but more studies are needed to assess it value in viability assessment.

In conclusion, imaging myocardial viability by PET provides assessment of both physiological perfusion and myocardial tissue's metabolic activity to differentiate hibernating from scarred myocardium.