Maturation of arteriovenous fistulas in patients with ventricular assist devices

OBJECTIVE

Postoperative renal dysfunction necessitating hemodialysis after implantation of ventricular assist devices presents a challenge with respect to establishment of hemodialysis access. Lack of pulsatile flow has led to concerns that arteriovenous fistulas will not mature. This study aims to evaluate arteriovenous fistula as a method of hemodialysis.

METHODS

Consecutive patients who underwent implantation of a ventricular assist device between 1988 and 2016 with a subsequent need for hemodialysis were identified. Retrospective data were collected for patients requiring hemodialysis through an arteriovenous fistula or arteriovenous graft. Access flow rates and duration of patency are reported.

RESULTS

Sixty-four patients were identified (10 required long-term hemodialysis, 5 via arteriovenous fistula, 1 via arteriovenous graft). All six patients receiving long-term hemodialysis access were on continuous-flow ventricular assist devices. Brachiocephalic arteriovenous fistulas were performed in all arteriovenous fistula patients, and the average preoperative vein diameter was 4.1 ± 0.9 mm. On 30-day follow-up, the average flow rate was 1262 ± 643 mL/min (880-2220). In arteriovenous fistula patients, one died at 30 days, one arteriovenous fistula required ligation for steal syndrome at 5 months, and one was abandoned after 10.7 months for low flow. Of remaining fistulas, one was converted to an arteriovenous graft at 1.7 years for malfunction (with 5.3 month patency), and one remains open at 4.0 years.

CONCLUSION

Arteriovenous fistulas should be considered in selected patients with ventricular assist devices as a means of long-term hemodialysis access to avoid use of catheters. Maturation and usage of primary arteriovenous fistulas is possible despite lack of pulsatile flow.

Endoscopic versus open saphenous vein graft harvest for lower extremity bypass in critical limb ischemia

OBJECTIVE

Endoscopic vein harvest (EVH) has been demonstrated to improve early morbidity when compared with conventional open vein harvest (OVH) technique for infrainguinal bypass surgery. However, recent literature suggests conflicting results regarding mid- and long-term patency with EVH. The purpose of this study is to compare graft patency between harvest techniques specifically in patients with critical limb ischemia.

METHODS

This retrospective study compared two groups of patients (EVH = 39 and OVH = 49) undergoing lower extremity revascularization from January 2009 to December 2011. Outcome measures included patency rates, postoperative complications, and wound infection. Graft patency was assessed using Kaplan-Meier curves.

RESULTS

Both groups were matched for demographics and indications for bypass (critical limb ischemia). Median follow-up was 22 months. There was a significant reduction in the incidence of wound infection at the vein harvest site in the EVH group (OVH = 20%; EVH = 0%; P < .001), nevertheless, the difference was not significant when only the anastomotic sites were included (OVH = 12.2%; EVH = 15.4%; P = .43). The hospital length of stay was comparable between the two groups (EVH = 8.73 ± 9.69; OVH = 6.35 ± 3.28; P = .26) with no significant difference in the recovery time. Primary graft patency rate was 43.2% in the EVH group and 69.4% in the OVH group (P = .007) at 3 years. The most common reason for loss of primary patency was graft occlusion (61.5%) in the OVH group and vein graft stenosis (54.5%) in the EVH group. The average number of vascular reinterventions per bypass graft was significantly lower in the OVH group compared with the EVH group (OVH = 0.37; EVH = 1.28; P < .001).

CONCLUSIONS

Our findings demonstrate inferior primary patency when using the technique of EVH. Additionally, we identified a significantly higher rate of reintervention in the EVH cohort as well as a higher rate of vein graft body stenosis. However, EVH was associated with a decreased rate of wound complications with similar limb salvage and secondary patency rates when compared to OVH. EVH should therefore be selectively utilized in patients at high risk for wound complications.

Cellular-specific role of toll-like receptor 4 in hepatic ischemia-reperfusion injury in mice

Ischemia-reperfusion (I/R) injury is a process whereby an initial hypoxic insult and subsequent return of blood flow leads to the propagation of innate immune responses and organ injury. The necessity of the pattern recognition receptor, Toll-like receptor (TLR)4, for this innate immune response has been previously shown. However, TLR4 is present on various cell types of the liver, both immune and nonimmune cells. Therefore, we sought to determine the role of TLR4 in individual cell populations, specifically, parenchymal hepatocytes (HCs), myeloid cells, including Kupffer cells, and dendritic cells (DCs) subsequent to hepatic I/R. When HC-specific (Alb-TLR4(-/-) ) and myeloid-cell-specific (Lyz-TLR4(-/-) ) TLR4 knockout (KO) mice were subjected to warm hepatic ischemia, there was significant protection in these mice, compared to wild type (WT). However, the protection afforded in these two strains was significantly less than global TLR4 KO (TLR4(-/-) ) mice. DC-specific TLR4(-/-) (CD11c-TLR4(-/-) ) mice had significantly increased hepatocellular damage, compared to WT mice. Circulating levels of high-mobility group box 1 (HMGB1) were significantly reduced in Alb-TLR4(-/-) mice, compared to WT, Lyz-TLR4(-/-) , CD11c-TLR4(-/-) mice and equivalent to global TLR4(-/-) mice, suggesting that TLR4-mediated HMGB1 release from HCs may be a source of HMGB1 after I/R. HCs exposed to hypoxia responded by rapidly phosphorylating the mitogen-activated protein kinases, c-Jun-N-terminal kinase (JNK) and p38, in a TLR4-dependent manner; inhibition of JNK decreased release of HMGB1 after both hypoxia in vitro and I/R in vivo.

CONCLUSION

These results provide insight into the individual cellular response of TLR4. The parenchymal HC is an active participant in sterile inflammatory response after I/R through TLR4-mediated activation of proinflammatory signaling and release of danger signals, such as HMGB1.

Interleukin-17 and interferon-gamma are produced concomitantly by human coronary artery-infiltrating T cells and act synergistically on vascular smooth muscle cells

BACKGROUND

Atherosclerosis is an inflammatory disease in which interferon (IFN)-gamma, the signature cytokine of Th1 cells, plays a central role. We investigated whether interleukin (IL)-17, the signature cytokine of Th17 cells, is also associated with human coronary atherosclerosis.

METHODS AND RESULTS

Circulating IL-17 and IFN-gamma were detected in a subset of patients with coronary atherosclerosis and in referent outpatients of similar age without cardiac disease but not in young healthy individuals. IL-17 plasma levels correlated closely with those of the IL-12/IFN-gamma/CXCL10 cytokine axis but not with known Th17 inducers such as IL-1beta, IL-6, and IL-23. Both IL-17 and IFN-gamma were produced at higher levels by T cells within cultured atherosclerotic coronary arteries after polyclonal activation than within nondiseased vessels. Combinations of proinflammatory cytokines induced IFN-gamma but not IL-17 secretion. Blockade of IFN-gamma signaling increased IL-17 synthesis, whereas neutralization of IL-17 responses decreased IFN-gamma synthesis; production of both cytokines was inhibited by transforming growth factor-beta1. Approximately 10-fold fewer coronary artery-infiltrating T helper cells were IL-17 producers than IFN-gamma producers, and unexpectedly, IL-17/IFN-gamma double producers were readily detectable within the artery wall. Although IL-17 did not modulate the growth or survival of cultured vascular smooth muscle cells, IL-17 interacted cooperatively with IFN-gamma to enhance IL-6, CXCL8, and CXCL10 secretion.

CONCLUSIONS

Our findings demonstrate that IL-17 is produced concomitantly with IFN-gamma by coronary artery-infiltrating T cells and that these cytokines act synergistically to induce proinflammatory responses in vascular smooth muscle cells.

Interleukin (IL)-1 promotes allogeneic T cell intimal infiltration and IL-17 production in a model of human artery rejection

Interleukin (IL) 1α produced by human endothelial cells (ECs), in response to tumor necrosis factor (TNF) or to co-culture with allogeneic T cells in a TNF-dependent manner, can augment the release of cytokines from alloreactive memory T cells in vitro. In a human–mouse chimeric model of artery allograft rejection, ECs lining the transplanted human arteries express IL-1α, and blocking IL-1 reduces the extent of human T cell infiltration into the artery intima and selectively inhibits IL-17 production by infiltrating T cells. In human skin grafts implanted on immunodeficient mice, administration of IL-17 is sufficient to induce mild inflammation. In cultured cells, IL-17 acts preferentially on vascular smooth muscle cells rather than ECs to enhance production of proinflammatory mediators, including IL-6, CXCL8, and CCL20. Neutralization of IL-17 does not reduce T cell infiltration into allogeneic human artery grafts, but markedly reduces IL-6, CXCL8, and CCL20 expression and selectively inhibits CCR6⁺ T cell accumulation in rejecting arteries. We conclude that graft-derived IL-1 can promote T cell intimal recruitment and IL-17 production during human artery allograft rejection, and suggest that targeting IL-1 in the perioperative transplant period may modulate host alloreactivity.

An inflammatory pathway of IFN-gamma production in coronary atherosclerosis

Inflammation is associated with the pathogenesis of coronary atherosclerosis, although the mechanisms remain unclear. We investigated whether cytokine secretion by innate immune responses could contribute to the production of proarteriosclerotic Th1-type cytokines in human coronary atherosclerosis. Cytokines were measured by ELISA in the plasma of patients with coronary atherosclerosis undergoing cardiac catheterization. IL-18 was detected in all subjects, whereas a subset of patients demonstrated a coordinated induction of other IFN-gamma-related cytokines. Specifically, elevated plasma levels of IL-12 correlated with that of IFN-gamma and IFN-gamma-inducible chemokines, defining an IFN-gamma axis that was activated independently of IL-6 or C-reactive protein. Systemic inflammation triggered by cardiopulmonary bypass increased plasma levels of the IFN-gamma axis, but not that of IL-18. Activation of the IFN-gamma axis was not associated with acute coronary syndromes, but portended increased morbidity and mortality after 1-year follow-up. IL-12 and IL-18, but not other monokines, elicited secretion of IFN-gamma and IFN-gamma-inducible chemokines in human atherosclerotic coronary arteries maintained in organ culture. T cells were the principal source of IFN-gamma in response to IL-12/IL-18 within the arterial wall. This inflammatory response did not require, but was synergistic with and primed for TCR signals. IL-12/IL-18-stimulated T cells displayed a cytokine-producing, nonproliferating, and noncytolytic phenotype, consistent with previous descriptions of lymphocytes in stable plaques. In contrast to cognate stimuli, IL-12/IL-18-dependent IFN-gamma secretion was prevented by a p38 MAPK inhibitor and not by cyclosporine. In conclusion, circulating IL-12 may provide a mechanistic link between inflammation and Th1-type cytokine production in coronary atherosclerosis.