Focal necroses, fatty degeneration and subendocardial nuclear polyploidization of the myocardium in newborns after beta-sympathicomimetic suppression of premature labor.

It has been well documented in laboratory animals that beta-sympathicomimetics, such as isoprenalin, can cause myocardial lesions. Other so called "beta2-selective" symphaticomimetic drugs, which nevertheless induce beta1-cardiostimulatory side effects, are now widely used for suppression of premature labor. We examined the hearts of 25 newborns whose mothers had been treated with beta-sympathicomimetics for various lengths of time (24h to 8 weeks). Three types of lesions were detected: (1) focal subendocardial necroses (3 cases), similar to isoprenalin-induced myocardial necroses in animal experiments, (2) diffuse fatty degeneration of myocardial cells (3 cases), and (3) nuclear polyploidization in the subendocardial layer of the right ventricular wall (14 cases). However, the immediate causes of death could not be directly related to the tocolytic treatment in any of the cases.