Assessment of tissue viability: clinical demand and problems.

Over the past decade it has become clear that chronic left ventricular dysfunction is not necessarily an irreversible process[1-41. In some patients recovery of function may occur dependent on the presence of dyssynergic yet viable myocardium. It has been hypothesized that chronic hypoperfusion may result in a down-regulation of myocardial contractility and this process can be reversed after adequate restoration of myocardial perfusion[51. To describe this concept, the term hibernation was coined by Diamond et al.[61. However, no animal modes are currently available to study long-term hibernation. In addition, no serial studies in patients with hibernation have been performed to determine the chronicity of the disorder and whether the 'severity' of the hibernation is stable over a long period of time. Several studies[7-1 have recently demonstrated that many regions with chronic contractile dysfunction have (near-)normal perfusion. In these situations, it is quite conceivable that recurrent episodes of ischaemia result in chronic depression of contractile function[8.111. Nonetheless, independent of the underlying pathophysiology, the detection of myocardial viability has now become an important aspect in the diagnostic work-up of patients with chronic left ventricular dysfunction. Only if viability can be demonstrated, are revascularization procedures justified, whereas absence of viability warrants conservative medical therapy or heart transplantation. The present review article focuses on three important questions that are frequently raised on the topic of myocardial viability. First, which patients need viability assessment and what is the ensuing clinical demand? Second, what is the optimum method to detect viability, and third, what other factors determine