Quantitative relation of myocardial infarct size and myocardial viability by positron emission tomography to left ventricular ejection fraction and 3-year mortality with and without revascularization.

OBJECTIVES

The purpose of this study was to determine the clinical prognostic value, with and without revascularization, of the size of myocardial infarction and viability as measured by positron emission tomography (PET).

BACKGROUND

Poorly contracting but viable myocardium recovers contractile performance after revascularization. However, the quantitative relation among size of infarction and viability by PET, ejection fraction and long-term survival with and without revascularization in patients after myocardial infarction has not been previously reported.

METHODS

Infarct size and viability imaged by PET using generator-produced rubidium-82 were quantified objectively by automated software and related to coronary arteriography, left ventricular ejection fraction, revascularization and 3-year mortality.

RESULTS

Myocardial infarction or scar > or = 23% of the left ventricle was associated with a 3-year mortality rate of 43% versus that of 5% associated with scar < 23% of the left ventricle (p = 0.014). An ejection fraction < or = 43% correlated with a 3-year mortality rate of 38% compared with 6% for an ejection fraction > or = 43% (p = 0.029) because infarct size > or = 23% of the left ventricle was also associated with an ejection fraction < or = 43%. For patients with a low ejection fraction (< or = 43%) or large infarcts/scar (> or = 23% of the left ventricle), ejection fraction value or infarct size did not predict mortality. However, in patients with an ejection fraction < or = 43%, the absence of viable myocardium in arterial zones at risk was associated with a mortality rate of 63% versus 13% in subjects with viable myocardium, a difference with only a 5.9% probability of occurring by chance alone (p = 0.059). For all patients with viable myocardium in arterial zones at risk, the mortality rate was 8%, and 80% had revascularization over 3 years. For patients with only fixed scar in arterial zones at risk, the mortality rate was 50% versus 8% (p = 0.018), and 40% had revascularization, with no difference in mortality with or without revascularization, thereby suggesting no benefit in this subgroup.

CONCLUSIONS

Size of scar and viable myocardium by PET in arterial zones at risk in patients after myocardial infarction are highly predictive of 3-year mortality, particularly in patients with low ejection fraction, and identify patients who are suitable candidates for revascularization after myocardial infarction.