An external cardiac assistance device is provided for augmenting cardiac contractions. The device includes a flexible, non-distensible shell adapted to be positioned over the base of the heart. A distensible membrane is mounted within the shell to define an inflatable space so that the device can be used on various sized hearts. Inflatable compartments are formed within the shell adjacent the membrane so as to engage the left and right ventricles of the heart. The device can be manually held in position on the heart by a handle for short-term use, or by a plurality of straps for intermediate and long term use. The device is operatively connected to an EKG machine which actuates a fluid pump in response to the QRS waves of the heart so as to rhythmically inflate and deflate the compartments to assist with the contractions of the heart.