Myocardial viability assessment and utility in contemporary management of ischemic cardiomyopathy

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.

Surgical Management of Ischemic Cardiomyopathy Patients with Severe Left Ventricular Dysfunction: Is It Time to Reconsider Revascularization Surgery?

“…Some researchers believe that the results of the STICH trial may be influenced by using SPECT and DSE which have suboptimal image resolution and could not distinguish between hibernating and scarred myocardium. They believe measuring myocardial viability with PET and CMR could precisely determine metabolically active myocardium and quantify myocardial scars [61].…”

Revascularization and Left Ventricular Dysfunction for ICD Eligibility

“…Stunning is referred to the myocardium that is transiently ischemic and displays contractile dysfunction, which ultimately recovers early after restoration of normal resting blood flow. In the context of hibernating myocardium resting blood flow is severely reduced, while cardiac tissue remains viable by adaptively reducing contractility and cellular activity to decrease basal metabolic requests [ 35 ]. In contrast to stunned myocardium, hibernating myocardium usually recovers late after revascularization [ 36 ].…”

“…Prolonged myocardial hibernation may progress to necrosis, limiting functional recovery after revascularization. Extent of viability is also important, and several studies have shown that at least 25% to 30% of dysfunctional myocardium needs to be viable for improvement in LVEF after revascularization, with the except of extensively remodeled and dilated ventricles which could not recover after revascularization even in the presence of viable areas [ 34 , 35 , 36 ].…”

Determination of viable myocardium through delayed enhancement cardiac magnetic resonance imaging combined with 18F-FDG PET myocardial perfusion/metabolic imaging before CABG

“…This then results in improved left ventricle ejection fraction (LVEF), clinical symptoms, long-term survival, and the effect of revascularization can be fully utilized. However, for the patients without viable myocardium, CABG provides little improvement [ 5 , 6 ], resulting in high risk of death [ 7 ]. In addition, surgeries could lead to trauma and complications, and possibly worsen the patient’s condition.…”