Abnormal Ultrasonic Tissue Characterization of the Myocardium in Children Receiving Doxorubicin for Cancer Therapy

Ultrasonic tissue characterization by integrated backscatter is a sensitive tool to detect myocardial changes related to specific diseases. Cardiotoxicity related to doxorubicin use is well known and remains a major concern. To determine if ultrasonic tissue characterization of the myocardium is abnormal in patients receiving doxorubicin, we studied the myocardium of pediatric patients receiving doxorubicin by a real-time integrated backscatter (IB) imaging system. Three values of IB parameters were averaged from the left ventricular posterior wall at the level of the tip of the mitral valve. In addition to standard echo parameters, we obtained the following IB parameters: peak, nadir, cyclic variation (CV), end-diastole, heart-rate corrected delay of nadir (Delay_c), and the ratio of CV over end-diastole. IB parameters were normalized as Z scores from multiple linear regression equations including echo wall thickness and functional indices from a normal control group of 72 children. We evaluated 27 patients at a median age of 11.6 years (1.6 years to 20.3 years) and median time of 1.7 m (2 days to 7.2 years) after a mean cumulative dose of doxorubicin of 188 ± 120 mg/m² for treatment of neoplasm. Mean (± SD) Z scores for IB variables were as follows: zPeak 0.15 ± 1.07, P = 0.47; zNadir 0.41 ± 1.16, P = 0.08; zCV -0.49 ± 0.95, P = 0.01; zEnd-diastole 0.17 ± 0.94, P = 0.38; zDelay_c 0.33 ± 0.80, P = 0.06, and zCV/Peak -0.59 ± 1.06, P = 0.009. This study shows that ultrasonic IB of the myocardium of children receiving doxorubicin is abnormal and is independent of the cumulative dosage of doxorubicin or the amount of time since the last dose.