Myocardial Viability: From Proof of Concept to Clinical Practice

Abstract

Ischaemic left ventricular (LV) dysfunction can arise from myocardial stunning, hibernation, or necrosis. Imaging modalities have become front-line methods in the assessment of viable myocardial tissue, with the aim to stratify patients into optimal treatment pathways. Initial studies, although favorable, lacked sufficient power and sample size to provide conclusive outcomes of viability assessment. Recent trials, including the STICH and HEART studies, have failed to confer prognostic benefits of revascularisation therapy over standard medical management in ischaemic cardiomyopathy. In lieu of these recent findings, assessment of myocardial viability therefore should not be the sole factor for therapy choice. Optimization of medical therapy is paramount, and physicians should feel comfortable in deferring coronary revascularisation in patients with coronary artery disease with reduced LV systolic function. Newer trials are currently underway and will hopefully provide a more complete understanding of the pathos and management of ischaemic cardiomyopathy.

Cardiac Magnetic Resonance and Myocardial Viability: Why Is It so Important?

“…Myocardial viability is defined as a regional wall motion abnormality (hypokinesia, dyskinesia, or akinesia) without the presence of necrotic myocardial tissue. 4,6,12 After an acute event, the ischemic cascade is triggered, and myocardial viability, especially the reversibility of this process, can be influenced. A series of pathophysiological modifications appear in the damaged myocardium with the intent to replace the dead tissue with fibrotic scar tissue, as the viable myocardium tries to compensate the dysfunctional myocardium in order to maintain a competent cardiac output.…”

“…This type of myocardium contains not only apoptotic cells, but also cells with autophagosomes, vacuoles, and lysozymes. [1][2][3][4]14 …”

“…The results of this sub-study revealed the prognostic importance of the FDG PET viability imaging technique in patients with ischemic heart disease. 4,23 …”

“…Therefore, an early identification of these modifications is necessary in order to guide the treatment and follow-up of these patients. 4,5 The myocardium is very sensitive to ischemia, thus the degree of contractile damage is influenced by the severity and the duration of the ischemic event, from reversible myocardial tissue to necrosis. Once the myocardium dies, the normal myocardium is replaced by collagenous scar tissue.…”

“…Left ventricular remodeling is defined as a structural, geometrical, and functional change in the infarct patch and remote viable myocardium. [4][5][6] Thus, new treatment options cannot limit ventricular remodeling. It was demonstrated that a coronary intervention improves left ventricular fraction with only 3% to 4%.…”