Mechanical systems designed to support the failing heart temporarily or permanently are briefly described. Of these systems, most are still in the experimental laboratory, but several devices have had limited trial in patients. One for temporary use, the intra-aortic balloon pump, is now routinely used as adjunctive support for selected patients undergoing open-heart surgery. The development of these systems followed experimental demonstration that by manipulating arterial pressure and flow, it would be possible to increase coronary blood flow and diminish left ventricular work.

Assisted Circulation↗

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Early mechanical left ventricular assistance.

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Adult↗

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Autologous arterial grafts grown on polyester molds: observations of graft growth and patency in experimental animals.

Tissue molds consisting of polyester mesh jackets covering silicone mandrils were implanted subcutaneously in dogs. When a sufficiently strong layer of connective tissue had formed around the molds they were excised and the mandrils removed. The process of tissue formation was observed and recorded. The forms were used as grafts in either the abdominal aorta or the femoral artery of the dog. Six grafts 10 mm inner diameter, six grafts 6 mm inner diameter and 26 grafts 3 mm inner diameter were implanted. After 4.5 months 80% of the 10 mm grafts, 83% of the 6 mm grafts, but only 4% of the 3 mm grafts remained patent. Histological studies at various intervals after grafting revealed gradual thickening of the neointima. The reason for graft failure was thrombus formation originating at the line of anastomosis.

Animals↗

PubMedDate not supplied

A mechanical auxiliary ventricle. Histologic responses to long-term, intermittent pumping in calves.

The mechanical auxiliary ventricle (MAV) is an avalvular, inseries left ventricular assist device (LVAD) comprised of a 60 cc Biomer blood pump implanted in the descending thoracic aorta, a percutaneous access device (PAD), and an external pneumatic drive. In four calves the MAV was implanted and activated intermittently for 192, 249, 423, and 785 days, respectively; no anticoagulants were administered. When the animals were killed, the implants were retrieved, and autopsies, including gross, light microscopic, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) examinations, were performed. The MAV was securely attached to the aorta in every animal. A thin, even smooth, pseudoneointimal layer (PNI) contiguous with the aorta at the level of the suture line covered the MAV's blood-contacting surface. Areas of calcification beneath the PNI, expected in growing animals with implanted pumping devices, were noted. At autopsy there was no evidence of thrombosis or infection in the regions of the blood pump or the PAD. These findings confirm the calves' benign histologic response to the MAV, and together with the results of hematologic and biochemiccal studies, and bench tests of system components being reported elsewhere, indicate the system's readiness for limited clinical investigation in selected patients with chronic congestive failure.

Animals↗