REVERSIBLE CONTRACTILE DYSFUNCTION OF VIABLE MYOCARDIUM - IMPLICATIONS FOR DECISION-MAKING PROCESS IN POSTINFARCTION PATIENTS

Myocardial dysfunction and silent myocardial ischemia have been identi fied as important prognostic factors following acute myocardial infarc tion, also in low risk patients. In post-infarction patients, impaired left ventricular function is the result of fixed scar and reversible contractile dysfunction of viable stunning or hibernating myocardium. Post-extrasystolic potentiation (PESP) during 2-dimensional echocardio graphic monitoring may be used to detect the presence of viable myocar dium in asynergic myocardial segments. Incidence of reversible contrac tile dysfunction is a very common phenomenon at predischarge examinati on after myocardial infarction in asymptomatic patients, and it is ind ependent on the persistence of silent ischemia. A progressive loss of myocardial viability occurs over the first year following the acute ph ase despite the maintenance of an asymptomatic clinical status. This p henomenon is associated with significant dilatation of the left ventri cle. Moreover, silent ischemia is strongly related with this progressi ve loss of myocardial viability and left ventricular dilatation. Thus, it becomes evident that the most important role of medical and interv entional approaches consists of limiting the acute necrosis by reperfu sion and in preventing the loss of viable chronically hypoperfused myo cardium that appears to be a major factor of left ventricular remodeli ng and changes over time of prognostication in individual patients. Fi nally, the presence of viable myocardium by PESP in the arterial zone at risk is highly predictive of 4-year mortality, particularly in pati ents with low ejection fraction (<40%), and identifies patients who ar e suitable candidates for revascularization after myocardial infarctio n.