sarafotoxin at a dose that causes death of 50 of the injected population within one hour group iii was irradiated immediately following the injection of sarafotoxin similarly to the rats in experiment i and again two days thereafter all mice were sacrificed 7 days after the injection of sarafotoxin upon examination heart ventricles of sarafotoxin injected mice were found to be significantly dilated as compared to the control electron microscopy analysis showed damage to myocardial cells of the dilated ventricles in particular it revealed swollen vacuoles containing cardiomyocytes with disorganized contractile apparatus and other cell organelles ecg analysis showed possible damage to the conducting system in the hearts of injected mice the dilatation index defined as the ratio in percent of left ventricular cavity to total volume of left ventricle of non irradiated sarafotoxin injected group ii mice was 22 u00b1 7 in the laser irradiated group iii mice the dilatation index was 12 u00b1 8 significantly p lt 0 05 lower than in the non irradiated mice moreover the cardiomyocytes of the irradiated mice showed a more organized contractile apparatus and contained fewer vacuoles from the results of experiment vi it is concluded that the laser irradiation as applied in the experiment protects the cardiomyocytes and probably the conducting system as well from the adverse effects of sarafotoxin it will thus be appreciated that in addition to the therapeutic effects of ecb in treating ischemic and infarcted heart tissue as shown by experiments i v.