Mustafa Akdis

Blood pumps for circulatory support.

During the past decade, mechanical cardiac assist devices have gained widespread acceptance as therapeutic instruments for the treatment of cardiac insufficiency. Their primary task is to maintain blood circulation and thus to provide sufficient oxygen supply to organs and body tissue if the natural heart is failing. Modern development in mechanical circulatory assist devices has resulted in a large number of different pumping principles ranging from intra-aortic balloon pumps (IABP) to the total artificial heart (TAH), according to the specific clinical indication. Application times may vary from a few hours over days or weeks to chronic. Therefore, indication, timing of introduction and the selection of the appropriate device are as important as the specific pump design itself. Other issues for consideration are quality of life, reliability, and cost-effectiveness.

Miniaturized HIA microdiagonal pump as left ventricular assist device in a sheep model.

We evaluated the newly developed miniaturized HIA microdiagonal blood pump (MDP) as a continuous flow left ventricular assist device. In a sheep model (n = 6), the MDP was implanted through left lateral thoracotomy and placed paracorporeally with inflow conduit to left atrium and outflow conduit to descending aorta. The sheep were pumped at a mean flow rate of 2.5 L/min for 7 days. Anticoagulation was applied by intravenous heparin administration. Postoperatively, activated clotting time was held stable with values of 200 seconds. During follow-up, blood samples (creatinine kinase, creatinine, glutamic-oxaloacetic transaminase (aspartate aminotransferase) (GOT), glutamate dehydrogenase (GLDH), gamma-GT, plasma-free hemoglobin, and hemoglobine) were taken daily. After 7 days, the sheep were killed for macroscopic examination. Systemic artery pressures remained stable during the whole test period. Because of operative reasons, the hemoglobin value (7.5 ± 0.61 g/dl) decreased perioperatively, but recovered within the test period, whereas creatinine kinase increased initially after thoracotomy, but decreased to normal within days. Renal and liver functions were slightly impaired perioperatively, indicated by temporarily enhanced values of GOT, gamma-GT, GLDH, and creatinine. The MDP did not produce significant hemolysis as measured by plasma-free hemoglobin levels. Wound infections did not occur. We conclude that the MDP ran successfully as an left ventricular assist device for 7 days in sheep has potential for long-term support, and may serve as an alternative to current technologies. Presented data were not obtained in a clinical trial; however, the results are promising enough to proceed with longer duration animal studies.

Temporary or permanent support and replacement of cardiac function

Cardiac assist devices are classified into the traditional engineering categories of displacement and rotary pumps. Clinical use and indications of the various pump categories are outlined and a detailed description of the currently available systems is given. The first section deals with extracorporeal as well as implantable ventricular assist devices of the displacement type and is followed by a section on current developments in the field of total artificial hearts. The latter part of the article covers the rotary pump category from cardiopulmonary bypass applications to implantable systems, including specific design aspects of radial, diagonal and axial pumps.

Experimental testing of a new left ventricular assist device--the microdiagonal blood pump.

All existing ventricular assist devices are associated with a considerable number of serious complications. This article reports on the first animal tests with a newly developed microdiagonal blood pump (MDP). Six adult female sheep weighing 80 to 90 kg underwent implantation of the microdiagonal blood pump. The inflow and outflow conduits were anastomosed to the left atrium and the descending aorta. Pump flow was adjusted to 2–3 L/minute. Hemodynamic and echocardiographic data, as well as blood samples, were measured over the entire test period of 7 days. All internal organs and the pump were explanted for thorough examination at the end of the trial. Mean arterial (range 88.5 ± 13.1–103.7 ± 10.7 mm Hg) and mean pulmonary arterial (18.3 ± 2.7–21.6 ± 20.5 mm Hg) pressures, as well as the pulmonary capillary wedge pressure (14.2 ± 3.0–16.6 ± 4.0 mm Hg), remained stable during the whole test period. Cardiac output (4.9 ± 0.7 → 3.2 ± 0.5 L/minute) decreased postoperatively caused by partial unloading of the heart. Left ventricular end diastolic (4.1 ± 0.5 → 3.6 ± 0.3 cm) and end systolic (3.2 ± 0.4 → 2.8 ± 0.5 cm) diameters, as well as the ejection fraction (57 ± 9 → 42 ± 5 %), decreased after MDP implantation and did not change during the test period. Mean number of platelets (428 ± 54 → 286 ± 66 × 103/μL) and hemoglobin (9.8 ± 1.3 → 6.3 ± 0.8 g/dL) decreased perioperatively because of surgical reasons and increased continuously in the postoperative course (platelet count and hemoglobin on day 7: 441 ± 74 × 103/μL and 7.2 ± 1.1 g/dL, respectively). Free hemoglobin was not enhanced in the postoperative course (mean value during the test period: 18.8 mmoL/L). Histologic examination of the organs did not demonstrate any infarctions of internal organs other than typical operative sequelae such as chronic pericarditis and some degree of atelectasis of the left lungs.These results demonstrate that the microdiagonal pump may be a promising alternative to the currently used ventricular assist devices, if long-term trials support these results.