Design, Development, and First In Vivo Results of an Implantable Ventricular Assist Device, MicroVad

Abstract

The design concept and first in vitro and in vivo results of a long-term implantable ventricular assist device system based on a microaxial blood pump are presented. The blood-immersed parts of the pump consist of a single-stage impeller and a proximally integrated microelectric motor. Both parts are surrounded by a pump housing currently made of polycarbonate to allow visible access to the blood-exposed parts. A titanium inflow cage attached to the tip of the housing is directly implanted into the left ventricular apex. The outflow of the pump is connected to the descending aorta by means of an e-PTFE graft. The overall dimensions of the device are 12 mm in outer diameter and about 50 mm in length. The calculated lifetime of the device is up to 2 years. The system underwent long-term durability tests, hydraulic performance tests, dynamic stability tests, and in vitro hemolysis and thrombogenicity tests. Furthermore, animal tests have been performed in adult Dorset sheep. In a first series, the pump has been placed extracorporeally; in a second series, the pump was completely implanted. Mean duration of the animal experiments of the second series was 31 days (range 8-110 days, n=14); no anticoagulation was administered over the whole test period. Blood data revealed no significant changes in blood cell counts, ionogram, or any other value. No end-organ dysfunction induced by long-term support could be observed, nor did the pathology reveal any evidence of thromboembolic complications.

In Vivo Preclinical Anticoagulation Regimens After Implantation of Ventricular Assist Devices

“…During autopsy, bilateral renal infarcts of thromboembolic origin that occurred during the implant period were identified in all animals, but this was not sufficient to impair the renal function. In another study, a miniaturized microaxial pump LVAD, called the MicroVad, was implanted in 24 sheep with mean support duration of 16 days (range 1–30 days) without any anticoagulation regimen and no thrombus formation (69). Christiansen et al.…”

Artificial Organs 2004: A Year in Review

“…In animal experiments up to 90 days there was no noticeable depth increase in the top bearing with in vitro studies and the life of bearings was estimated to be a minimum of 3 years. Wolfgang Kerkhoffs et al (23) of the Helmholtz‐Institute for Biomedical Engineering (Aachen, Germany) reported on the design, development, and first in vivo results of their long‐term implantable ventricular assist device based on a microaxial blood pump. The studies validated the bearing concept in vitro and in animal studies.…”

An Implantable Aortic Valvo-pump for Destination Therapy

“…There are about 950,000 people in the US alone who die of cardiovascular diseases yearly, while only about 2000 heart transplants are performed in the US each year, according to the reports of American Heart Association (Kerkholffs et al, 2004;American Heart Association, 2003). Artificial heart blood pumps, aimed originally at replacing the natural donor heart for heart transplantation, could be only a bridge to heart transplantation after fifty years research and development (DeBakey et al, 2004).…”