Practical Implications of Myocardial Viability Studies

Abstract

Many non-invasive methods, such as imaging tests, have been developed aiming to add a contribution to existing studies in estimating patients' prognosis after myocardial injury. This prognosis is proportional to myocardial viability, which is evaluated in coronary artery disease and left ventricular dysfunction patients only. While myocardial viability represents the likelihood of a dysfunctional muscle (resulting from decreased oxygen supply for coronary artery obstruction), hibernation represents post-interventional functional recovery itself. This article proposes a review of pathophysiological basis of viability, diagnostic methods, prognosis and future perspectives of myocardial viability. An electronic bibliographic search for articles was performed in PubMed, Lilacs, Cochrane and Scielo databases, according to pre-established criteria. The studies showed the ability of many imaging techniques in detecting viable tissues in dysfunctional areas of left ventricle resulting from coronary artery injuries. These techniques can identify patients who may benefit from myocardial revascularization and indicate the most appropriate treatment.

Figure 1

Main feature of the physiopathology of stunned myocardium and hibernating myocardium [adapted from Chareonthaitawee et al.]

Figure 2

Images of rest (upper line) and nitrate-enhanced rest (lower line) myocardial perfusion scintigraphy, showing improvement of perfusion in anterior (apical, medial and basal) and anterolateral (medial and basal) segments.

Figure 3

Myocardial perfusion scintigraphy with ²⁰¹Tálio for assessment of myocardial viability; stress imaging (upper line) and 24-hour redistribution imaging after injection of the radiotracer ²⁰¹Tálio (lower line), showing improvement of perfusion in anterior (apical, medial and basal) and anterolateral (medial and basal) segments.

Figure 4

Myocardial perfusion scintigraphy with ^99mTc-Sestamibi (upper line) and ¹⁸F-FDG PET (lower line) for assessment of myocardial viability, showing improvement in perfusion/metabolism in anterior (apical, medial and basal), apical septal, anteroseptal (medial and basal) and inferoseptal (medial and basal) segments; “mismatch” pattern.

Figure 5

Patterns of transmurality of infarction in the presence and absence of viability by cardiac magnetic resonance