['Patients with ischemic heart failure may benefit from coronary artery bypass grafting. The histopathological variables associated with improvement in ejection fraction 6 months after surgery were assessed.', 'This study comprised 24 patients indicated for coronary artery bypass grafting, ejection fraction < 35%, functional class II-IV heart failure, and mean age 59 +/- 9 years. Endomyocardial biopsies were performed during and 6 months after surgery. Extension of the fibrosis, number of cells with myocytolysis, and hypertrophy of the muscle fiber were quantified by using a system of image analysis. Clinical and functional review was repeated within 6 months.', 'A significant improvement in heart failure functional class was observed in 16 patients after 6 months of follow-up (from NYHA functional class 2.8 +/- 0.7 to 1.7 +/- 0.6; P < 0.001), but the ejection fraction did not change (25 +/- 6 % vs. 26 +/- 10%). Hypertrophy of the muscle fiber was similar in the specimens biopsied in the pre- and postoperative periods (21 +/- 4 vs. 22 +/- 4 microm), but the extension of fibrosis (8 +/- 8 vs. 21 +/- 15% area) and the number of cells with myocytolysis (9 +/- 11 vs. 21 +/- 15% cell) significantly increased. However, the composition of a histological score combining those 3 variables indicated a greater increase in the ventricular function of those with a lower degree of preoperative histopathological alterations.'] Does endomyocardial biopsy foretell ventricular function recovery after coronary artery bypass grafting?