AbstractsEngineering

This study reports the design, construction, and evaluation of an automatic cardiac massage device and support system. The design incorporates the principle of a cardioplethysmograph operated in reverse, such that pneumatic power fed to the prosthesis will mechanically impart a massaging action to the heart. Basically, the prosthesis is a flexible sac inside a rigid housing which extends from the base to the apex of the heart. Pulsating pneumatic pressure, fed through an aperture in the outer housing, causes the inner sac to squeeze the intact ventricles resulting in a period corresponding to normal systole. The compression of the ventricles during the automatic massage procedure tends to eject the heart from the prosthesis; therefore, in order to resist this ejection force the prosthesis is firmly secured around the heart by utilizing the pericardium as a support. An attachment ring is sutured to the pericardium near the base of the ventricles, and the prosthesis is sutured to the ring. Thus the forces tending to eject the heart from the prosthesis are resisted by the entire circumference of the pericardium rather than by local sutured areas. Pericardial strength tests were conducted and the results of these studies indicated that this method of securing the prosthesis is feasible. In order to test the prosthesis under actual working conditions, a prosthesis was implanted in a Rhesus macaque (Macaca mulatta) and the heart was massaged for one hour; during this time an appreciable arterial pulse was maintained, indicating a successful massaging action. The pericardium showed no signs of stress or fatigue during or after massaging and no lesions or rupture were observed. All indications were that the massaging could have been continued for several hours. On the basis of the results obtained, this method of prosthesis attachment and the prosthesis design were considered to be successful and workable.