Temporal leukocyte numbers and granulocyte activation in pulsatile and rotary ventricular assist device patients

Abstract

Individual ventricular assist device (VAD) design may affect leukocytes and impact immunity. Few studies have presented leukocyte and infection profiles in VAD patients over the course of the implant period. CD11b (MAC-1) expression on granulocytes is an indicator of activation during inflammation, mediating extravasation and the release of reactive oxygen species in tissue. No reported studies have presented MAC-1 expression on circulating granulocytes in VAD patients. Fifty-six patients implanted at a single center with a HeartMate II (HMII; n = 32), HeartWare (HW; n = 12), or Thoratec pneumatic VAD (PVAD; n = 12) between 1999 and 2011 were followed for 120 days of support. The leukocyte profiles and infectious events of all patients were evaluated; additionally, a subset had MAC-1 expression on circulating granulocytes was measured (HMII n = 9; HW n = 7; PVAD n = 4). All groups exhibited a significant peak in leukocyte numbers at postoperative day (POD) 14 while simultaneously experiencing a significant decrease in hematocrit. HMII patients exhibited a 3.2-fold increase in granulocyte MAC-1 expression at POD 14, and the temporal trend over the implant period differed from that experienced by HW patients. Further, HW patients experienced significantly fewer infection events. Alterations in leukocyte profiles and granulocyte activation experienced by VAD patients appear to be device-specific. Elevations in leukocyte activation may be related to an increased risk for infection, although the specific relationship between these phenomena in this patient group is not known.

Keywords: Artificial organs; Circulatory assist devices; Immunology; Inflammatory cells; Left ventricular assist devices; Neutrophils; Systemic inflammation.

Figure 1

Leukocyte and hematocrit changes and incidence of infection events in HMII, HW or PVAD patients following implantation of the device. A) White blood cell numbers. B) The percentage of white blood cells consisting of granulocytes. C) Total hematocrit. D) Infection events per day of patient support. Mean plus standard error of the mean for continuous data. Normal ranges are intra-hospital values. “0” on the abscissa indicates pre-operative values. HMII=HeartMate II; HW=HeartWare; PVAD=Thoratec PVAD pneumatic device.

Figure 2. MAC-1 expression on circulating granulocytes in a subset of VAD patients following implantation

A) MAC-1 expression in all 3 devices evaluated to 1 month post-implant. B) MAC-1 expression in HMII or HW patients to POD 120. Data presented as mean plus standard error of the mean. “0” on the abscissa indicates pre-operative values. HMII=HeartMate II; HW=HeartWare; PVAD=Thoratec PVAD pneumatic device.

Figure 3

Granulocytes expressing MAC-1 in HMII patients that experienced at least one infection event during study enrollment. Data presented as mean plus standard error of the mean. HMII=HeartMate II.