Myocardial viability

Abstract

Viability information is like a moon in the sky of prognosis: in the daytime of a preserved global left ventricular function (ejection fraction >35%) the sun shines, and the moon - even if present in the sky - gives no additional prognostic light. The prognosis is linked to the clouds of ischemia, which obscure the sun of preserved resting function. In these good ventricles, with ejection fraction greater than 35%, the documentation of ischemia should dictate a revascularization oriented by the results of physiological testing. In the prognostic night light of a reduced left ventricular function (ejection fraction <35%), the adverse prognostic effects of ischemia are magnified and ischemia, per se, warrants revascularization. For any given level of inducible ischemia, the prognosis worsens with the worsening of the left ventricular function. The documentation of a large amount of viable myocardium reduces the risk of revascularization and viability-oriented revascularization determines a survival advantage in comparison to medically treated patients. It is important, however, that the viability moonlight can direct the cardiologist only when a full moon is present, i.e., a considerable amount of viable myocardium. Similar to ischemia, viability response should also be titrated. Viability is not a binary, dichotomous response, but it is a continuous response that should be stratified in different shades of gray. The prognostic protection conferred by viability is only detected when it exceeds a critical threshold of at least four segments or 20% of the total left ventricle. The beneficial impact of viability on survival is more pronounced in revascularized patients. © 2009 Springer Berlin Heidelberg.