Pump Thrombosis Rates Research Articles

Thrombosis in Continuous Flow Left Ventricular Assist Devices: Our Clinical Experience With Medical and Surgical Management

Continuous-flow left ventricular assist devices (CF-LVADs) such as the HeartMate II and HeartWare left ventricular assist device are important alternatives to heart transplantation. Thrombosis is a serious complication in both devices and we present our approach to treating thrombosis and analysis of predisposition factors. Our center's CF-LVADs database was retrospectively reviewed for pump thrombosis between January 2011 and January 2015. The patients were grouped for pump thrombosis (n= 13) and nonpump thrombosis (n= 85). Patients with pump thrombosis were further divided by device type (n= 5 HeartMate II and n= 8 HeartWare left ventricular assist device). Predisposition factors for pump thrombosis, our treatment approach, and patient outcomes were evaluated. Pump thrombosis was diagnosed in 13 of 98 patients. The rate of pump thrombosis did not differ between the 37 HeartMate II and 61 HeartWare left ventricular assist device patients. High mean arterial blood pressure (P< .01) and noncompliance with the anticoagulation regimen (P= .04) were associated significantly with thrombosis. Twelve patients with stable hemodynamics were treated initially with intravenous tissue plasminogen activator and 1 patient who had end-organ damage underwent pump exchange. Two patients failed to respond to medical treatment and underwent pump exchange. Two patients with recurrent thrombosis were administered intracardiac tissue plasminogen activator. Five patients died after medical treatment and 4 deaths were due to cerebral hemorrhage. Avoiding increased mean arterial blood pressures and ensuring optimal anticoagulation may help to decrease pump thrombosis. In patients with pump thrombosis, thrombolytic therapy is an alternative that is less invasive than pump exchange, but carries the risk of hemorrhage and thromboembolism.

A Comparison of Von Willebrand Factor Indexes in Heartmate II Compared to Heartware Left Ventricular Assist Devices

Background: Von Willebrand factor (VWF) is a multimeric glycoprotein synthesized in endothelium and megakaryocytes. Elevated total VWF antigen has been associated with arterial thrombosis, while in patients with left ventricular assist devices (LVAD), loss of high molecular weight multimers is associated with spontaneous bleeding. We hypothesized that the lower rotational speed of the Heartware LVAD would be associated with less severe disruption of VWF.Methods: A total of 22 patients were included. We compared samples from a) 17 patients with Heartmate II LVAD (HM II), 76% male, median age 67 (54-73) years, 24% non-white, 45 (33-59) months after implant, with b) 5 patients with Heartware (HW) LVAD, all male, age 64 (59-65) years, 20% non-white, 27 (14-29) months after implant. All patients received warfarin. All HW patients took aspirin, while 82% of HM II patients took aspirin. Samples were analyzed for VWF antigen, activity, platelet function analyzer-100 collagen adenosine diphosphate closure time (PFA) and VWF multimers by gel electrophoresis. Multimers were assessed qualitatively and quantitatively by dividing mers > 15 by mers 2-15 (multimer ratio) and with a normalized multimer ratio (multimer ratio of patient / normal plasma control from the same gel).Results: Although flow rates did not differ significantly between HM II and HW, 5.2 (4.6-6.5) versus 4.3 (4.2-5.4) liters per minute respectively, rotational speeds were very different, mean 9472 versus 2680 rpms, p<0.0001). There were no differences in hemoglobin, hematocrit, or platelet count at the time of sampling. Qualitative VWF multimers were abnormal in all patients, and PFA was non-clotting in 88% of HM II patients and 80% of HW patients. VWF activity to antigen ratio was not different: HM II 0.68 (0.63-0.74) versus HW 0.70 (0.63-0.71). However, VWF antigen was significantly higher in HM II patients, 199 (174-227) compared to HW, 139 (122-160), p=0.039 and the normalized VWF multimer ratio was significantly lower, suggesting greater loss of high molecular weight multimers in HM II, 0.43 (0.41-0.48) compared to HW, 0.53 (0.48-0.56), p=0.0025 (figure).Conclusion: The lower rotational speed associated with the Heartware LVAD appears to produce less elevation of VWF antigen, and slightly less loss of VWF high molecular weight multimers compared to the Heartmate II LVAD. Additional studies are needed to describe whether or not lower pump thrombosis rates and rates of spontaneous bleeding are associated with these differences. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Abstract 16405: Prevention of HeartMate II Pump Thrombosis - Recommendations and Preliminary Observations From the PREVENT Study

Introduction and hypothesis: Recent data have indicated an increase in the rate of early, confirmed pump thrombosis of the HeartMate II (HMII) left ventricular assist device. Factors related to this increase were not known, but one of the hypotheses was change in clinical management over time. The PREVENT ( PREVEN tion of Heartmate II Pump T hrombosis through Clinical Management) study was designed to evaluate the impact of clinical practices developed to reduce the risk of HMII pump thrombosis. Methods: PREVENT is a prospective, multi-center, single-arm, non-randomized study of up to 300 patients at up to 25 sites. Patient and pump management, including implant technique, anticoagulation, and pump settings are guided by protocol (Table 1). Primary endpoint is incidence of confirmed pump thrombosis at 3 months, with a total follow-up of 6 months. Presented here are the preliminary results from the first 100 subjects enrolled. Results: Median age was 61 years [25-79], 87% were male, and 79% were destination therapy. At implant, 9% were in INTERMACS Profile1, 68% Profiles 2-3, and 22% Profiles 4-7. Preliminary analysis of 90-day outcomes demonstrated an incidence of 1% for confirmed and 2% for suspected thrombosis with a 38% incidence of INTERMACS-defined bleeding. Adherence to the protocol recommendations was as follows: 91% of the pumps were anchored, 97% of the patients were bridged with heparin, median pump speed at 1 month was 9190 [range: 8400-10000], with 93% of the patients having a pump speed &gt; 8600, and 78% of the patients having pump speeds &gt; 9000. Median INR per patient was 2.2 [IQR: 2.0-2.4]. Overall Kaplan-Meier survival was 93%. Conclusions: Preliminary results are encouraging and suggest good adherence to the PREVENT protocol and low rates of pump thrombosis without a resultant increase in bleeding complications. Overall survival after HM II implantation remains excellent.

Radiologic assessment of HeartMate II position: Minimal pump migration after long-term support

Surgical positioning of the HeartMate II (HMII) left ventricular assist device assuring an unobstructed blood flow path is essential for optimal device function and hemodynamic support. We report a non-invasive radiologic assessment of HMII position after implant and long-term follow-up. We reviewed 132 consecutive patients (age 64 ± 14 years; 86% male; 60% destination therapy) implanted with an HMII from January 2009 to December 2012 and followed for them for up to 4 years. A radiologist measured pump position, pocket depth and cannula angles using chest radiography. Changes over time were determined in 64 of these patients with pairs of radiographs immediately after implant and at an average of 2.0 ± 0.7 years of follow-up. The axis of the pump relative to the spine was 92 ± 10° at baseline and 94 ± 9° at 2 years (n = 64, p = 0.02), and inflow cannula angles averaged 21 ± 13° from vertical at baseline and 20 ± 12° at 2 years (p = not statistically significant). More than 90% of angle measurements showed <15° movement over the follow-up duration. There was a small but significant superior pump migration from a depth of 12.7 ± 2.7 cm to 10.4 ± 2.6 cm (p < 0.001). There were no cannula obstructions or instances of right ventricular assist device use. The 30-day operative mortality was 3.0%. Prolonged inotrope dependence occurred in 5.3% (7 of 126) of patients, and low rates of pump thrombosis of 0.018 event/patient-year (0 at 3 months) and stroke 0.074 event/patient-year were noted. Non-invasive radiographic measurements of surgical pump placement designed to avoid pump and cannula malposition demonstrate stable position with minimal pump migration.