An Extravascular Left Ventricular Assist Device

The hemodynamic efficacy and prosthesis-vessel interaction of a pneumatically activated circulatory assist device was investigated in 12 acute and 12 chronic studies in dogs. A poly-urethane balloon encased in Dacron-velour cloth was fastened to the descending thoracic aorta with a spiral wrapping of Dacron graft material. Diastolic augmentation was provided by rhythmic inflation and deflation of the balloon. Hemodynamic results, based on 5 dogs with experimental myocardial ischemia, showed that left ventricular systolic peak pressure decreased by 8.2 ± 1.9%, cardiac output increased by 13.1 ± 2.8%, and circumflex coronary artery flow rose by 17.5 ± 2.5%. In the chronic experiments the prosthesis was asynchronously but continuously activated from one to sixteen weeks at 74 cycles per minute. Postmortem examination of the implantation site in all 12 dogs showed that necrosis had developed but was limited to the outer half of the medial layer beneath the pumping chamber and that the aortic wall was compressed to about 70% of its original thickness. Although the method described represents a simple form of providing ventricular assistance, its applicability for long-term circulatory support remains to be evaluated.