Human myocardial morphologic and functional changes in the first 24 hours after doxorubicin administration

The purpose of this study was to document early structural changes in the human heart after the initial administration of doxorubicin. Endomyocardial biopsies were performed at baseline and at 4 and 24 hours after doxorubicin administration to 13 patients. Morphometric analysis of electron micrographs (x 31,200) quantitated mitochondrial and tubular sizes (sarcoplasmic reticulum and T tubules). The mitochondrial size increased from 0.25 +/- 0.01 mu 2 (mean +/- SE) at baseline to 0.27 +/- 0.03 mu 2 (not significant [NS]) at 4 hours and 0.30 +/- 0.03 mu 2 (NS) at 24 hours. The tubular size increased from 2.24 +/- 0.13 x 10(4) nm2 at baseline to 2.60 +/- 0.26 x 10(4) nm2 (P less than 0.05) at 4 hours and 2.46 +/- 0.29 x 10(4) nm2 (NS) at 24 hours. Micrographs analyzed for nuclear changes showed nucleolar contraction and segregation of granular and fibrillar components. These changes were noted in five of ten patients at 4 hours and in eight of 13 patients at 24 hours. Serial echocardiographic and systolic time interval determinations of left ventricular function demonstrated a significant improvement at both 4 and 24 hours. In conclusion, doxorubicin has its most significant effect on tubular structures. Left ventricular function improved during this time despite these findings.