Evidence suggests a major role for von Willebrand factor (vWF) in left ventricular assist device (LVAD)-associated bleeding. However, the mechanisms of vWF degradation during LVAD support are not well understood. We developed: (i) a simple and inexpensive vortexer model; and (ii) a translational LVAD mock circulatory loop to perform preclinical investigations of LVAD-associated vWF degradation. Whole blood was obtained from LVAD patients (n = 8) and normal humans (n = 15). Experimental groups included: (i) blood from continuous-flow LVAD patients (baseline vs. post-LVAD, n = 8); (ii) blood from normal humans (baseline vs. 4 h in vitro laboratory vortexer, ∼ 2400 rpm, shear stress ∼175 dyne/cm(2) , n = 8); and (iii) blood from normal humans (baseline vs. 12 h HeartMate II mock circulatory loop, 10 000 rpm, n = 7). vWF multimers and degradation fragments were characterized with electrophoresis and immunoblotting. Blood from LVAD patients, blood exposed to in vitro supraphysiologic shear stress, and blood circulated through an LVAD mock circulatory loop demonstrated a similar profile of decreased large vWF multimers and increased vWF degradation fragments. A laboratory vortexer and an LVAD mock circulatory loop reproduced the pathologic degradation of vWF that occurs during LVAD support. Both models are appropriate for preclinical studies of LVAD-associated vWF degradation.
Background Continuous flow left ventricular assist devices (CF LVAD) are being implanted with increasing frequency for end-stage heart failure. At the time of LVAD implant, a large proportion of patients have pulmonary hypertension, right ventricular (RV) dysfunction, and tricuspid regurgitation (TR). RV dysfunction and TR can exacerbate renal dysfunction, hepatic dysfunction, coagulopathy, edema, and even prohibit isolated LVAD implant. Repairing TR mandates increased cardiopulmonary bypass time and bicaval cannulation, which should be reserved for the time of orthotopic heart transplantation. We hypothesized that CF LVAD implant would improve pulmonary artery pressures, enhance RV function, and minimize TR, obviating need for surgical tricuspid repair. Methods One hundred fourteen continuous flow LVADs implanted from 2005 through 2011 at a single center, with medical management of functional TR, were retrospectively analyzed. Pulmonary artery pressures were measured immediately prior to and following LVAD implant. RV function and TR were graded according to standard echocardiographic criteria, prior to, immediately following, and long-term following LVAD. Results There was a significant improvement in post-VAD mean pulmonary arterial pressures (26.6 ± 4.9 vs. 30.2 ± 7.4 mmHg, p = 0.008) with equivalent loading pressures (CVP = 12.0 ± 4.0 vs. 12.1 ± 5.1 p = NS). RV function significantly improved, as noted by right ventricular stroke work index (7.04 ± 2.60 vs. 6.05 ± 2.54, p = 0.02). There was an immediate improvement in TR grade and RV function following LVAD implant, which was sustained long term. Conclusion Continuous flow LVAD implant improves pulmonary hypertension, RV function, and tricuspid regurgitation. TR may be managed nonoperatively during CF LVAD implant. doi: 10.1111/jocs.12214 (J Card Surg 2013;28:770–775)
Obesity has been correlated with various adverse events in patients who receive left ventricular assist devices (LVAD). In this study, we sought to further characterize the role of obesity in this patient population.Methods and Results:We performed a retrospective analysis of 164 patients implanted with a HeartMate II from August 2008 to December 2014. Patients were categorized into 2 BMI groups based on WHO guidelines: BMI 18.5-30 kg/m2(n=99) and BMI >30 kg/m2(n=65). Patient demographics, adverse outcome and long-term survival were compared between the 2 groups. For any outcome associated with BMI groups, we performed a Cox regression to identify confounding comorbidities. Preoperative demographics and comorbidities were similar. Patients with BMI >30 were younger (P=0.01) and had a higher incidence of type 2 diabetes (P=0.01). While rate of pump thrombosis was higher among patients with BMI >30 (P=0.02), overall survival at 2 years did not differ. The most common cause of death was hemorrhagic stroke in the obese group. On multivariable cox regression analysis, BMI was an independent risk factor of pump thrombosis.Higher BMI does not reduce survival after VAD implantation but it does appear to increase the risk of pump thrombosis. Further studies to characterize the role of BMI in survival and thrombosis rates are warranted.
Pump thrombosis (PT) is a common and potentially life-threatening complication among HeartMate II (HMII; Thoratec, Pleasanton, CA) patients. There have been efforts to correlate HMII geometry with higher risk of PT. The aim of this study was to test the validity of using HMII inflow cannula angle (ICA) and pump pocket depth (PPD) to predict PT. We performed a retrospective analysis of patients implanted with HMII left ventricular assist devices (LVADs) from January 2011 to March 2014 at our institution. Three blinded reviewers measured ICA and PPD from chest x-rays at postimplantation and most recent follow-up time points. The diagnosis of PT was visually confirmed upon device explantation by benchtop evaluation. HeartMate II was implanted in 90 patients. Sixteen (20%) patients experienced PT. There was no statistical difference between PT and non-PT patients in their initial ICAs (56.0° ± 10.1 vs. 54.6° ± 10.8, p = 0.63) and PPD (86.7 ± 24.9 mm vs. 81.1 ± 32.2 mm, p = 0.46). Prediction of PT using ICA and PPD by receiving operating characteristic was negative (area under curve (AUC) = 0.54 and 0.55, respectively). Changes in HMII geometry were measured over 112.5 (interquartile range = 34.3-337.3) days. A decrease in PPD was observed (p = 0.0001). Initial ICA was a significant predictor of future angle change and suggested a convergence toward the mean (55.4°) (analysis of variance p = 0.002). Pump thrombosis recurred in four (25%) patients. Postoperative ICA and PPD do not appear to predict PT in HMII patients in our experience. HeartMate II geometry changes over time secondary to remodeling with a decrease in PPD and a convergence toward the median in ICAs. Further investigation into the role of geometric ventricular assist device conformation postimplant may be warranted.
