Abstract
Background
In clinical practice, we encounter ischemic cardiomyopathy (ICM) with underlying viable, dysfunctional myocardium on a regular basis. Evidence from the Surgical Treatment for Ischemic Heart failure (STICH) and its Extension Study is supportive of improved outcomes with coronary revascularization, irrespective of myocardial viable status. However, Dobutamine stress echocardiography (DSE) and single‐photon emission computed tomography (SPECT), used in STICH to assess myocardial viability may fail to distinguish hibernating myocardium from scar due to suboptimal image resolution and poor tissue characterization.
Hypothesis
Cardiac magnetic resonance (CMR) and positron emission tomography (PET) can precisely quantify myocardial scar and identify metabolically active, viable myocardium respectively. Unlike DSE and SPECT, CMR and PET allow examining myocardial status as a contiguous spectrum from viable to partially viable myocardium with varying degrees of subendocardial scar and nonviable myocardium with predominantly transmural scar, the therapeutic and prognostic determinants of ICM.
Methods
Under the guidance of CMR and PET imaging, myocardium can be distinguished viable from partially viable with subendocardial scar and predominantly transmural scar. In ICM, optimal medical therapy and coronary revascularization of viable/partially viable myocardium but not transmural scar may improve outcomes in patients with acceptable procedural risk.
Results
Coronary revascularization of partially viable and viable myocardial territory may improve clinical outcomes by preventing future ischemic, infarct events and further worsening of left ventricular remodeling and function.
Conclusions
When deciding if coronary revascularization is appropriate in a patient with ICM, it is essential to take a patient‐tailored, comprehensive approach incorporating myocardial viability, ischemia, and scar data with others such as procedural risk, and patient's comorbidities.
Viability of myocardium is assessed by different imaging modalities, probing different characteristics of the living myocyte – uptake of radioactive isotope, TC‐99m or Tl‐201 (SPECT MPI), contractile reserve (Dobutamine stress imaging, echo or CMR), metabolic properties (FDG uptake on PET), absence of scar (CMR).
Dysfunctional, viable myocardium as compared to nonviable myocardium carries a better prognosis with appropriate therapy.
Dysfunctional myocardium may not be simplified into a binary state of viable or not. It can be a continuum process, with a myocardial segment in a hybrid state with an intermix of viable myocytes in early to late phases of hibernation and fibrosis.
Nonviable myocardium on Dobutamine Stress Echocardiography or SPECT Nuclear imaging may be partially viable (with varying degrees of fibrosis) or viable with no scar, on CMR.
Coronary revascularization of partially viable or viable myocardium should be considered if the procedural risk is acceptable, as it improves long‐term outcomes by preventing further myocardial ischemia/infarction and possibly improving left ventricular function and remodeling.
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