ABSTRACT
An experimental impact on the rat chest in the cardiac area induced bradycardia, arrhythmia, ectopic beats, atrio-ventricular blockade that was followed by a fall of the arterial pressure and a rise in the venous pressure, a decrease of the cardiac output and blood volume. Breakages in cardiac myofibers were seen under the microscope. These changes can be brought about by a direct effect of impact accelerations on the heart. It is concluded that tolerance of the animal heart to impact accelerations is limited by bradycardia, arterial pressure fall and a 25% decrease of the cardiac output. Greater effects may produce breakages in myofibers. An active alertness and unloading of the right atrium increase the heart tolerance to impact accelerations and potassium chloride prevents hazardous cardiac arrhythmias.
