Feasibility of a Composite Measure of Pulmonary Vascular Impedance and Application to Patients with Chronic RV Failure Post LVAD Implant

Pulmonary vascular impedance (PVZ) describes RV afterload in the frequency domain and has not been studied extensively in LVAD patients. We sought to determine (1) feasibility of calculating a composite (c)PVZ using standard of care (SoC), asynchronous, pulmonary artery pressure (PAP) and flow (PAQ) waveforms; and (2) if chronic right ventricular failure (RVF) post-LVAD implant was associated with changes in perioperative cPVZ.PAP and PAQ were obtained via SoC procedures at three landmarks: T(1), Retrospectively, pre-operative with patient conscious; and T(2) and T(3), prospectively with patient anesthetized, and either pre-sternotomy or chest open with LVAD, respectively. Additional PAP's were taken at T(4), following chest closure; and T(5), 4-24 h post chest closure. Harmonics (z) were calculated by Fast Fourier Transform (FFT) with cPVZ(z) = FFT(PAP)/FFT(PAQ). Total pulmonary resistance Z(0); characteristic impedance Zc, mean of cPVZ(2-4); and vascular stiffness PVS, sum of cPVZ(1,2), were compared at T(1,2,3) between +/-RVF groups.Out of 51 patients, nine experienced RVF. Standard hemodynamics and changes in cPVZ-derived parameters were not significant between groups at any T.In conclusion, cPVZ calculated from SoC measures is possible. Although data that could be obtained were limited it suggests no difference in RV afterload for RVF patients post-implant. If confirmed in larger studies, focus should be placed on cardiac function in these subjects.

Design and Rationale for the Direct Oral Anti-Coagulant Apixaban in Left Ventricular Assist Devices (DOAC LVAD) Study

Implantable left ventricular assist devices (LVAD) therapy is used to improve quality of life, alleviate symptoms, and extend survival in patients with advanced heart failure (HF). LVAD patients require chronic anticoagulation to reduce the risk of thromboembolic complications and frequently experience bleeding events. Apixaban is a direct oral anticoagulant which has become first-line therapy for patients with non-valvular atrial fibrillation and venous thromboembolism; however, its safety in LVAD patients has not been well-characterized. The evaluation of the hemocompatibility of the Direct Oral Anti-Coagulant apixaban in Left Ventricular Assist Devices (DOAC LVAD) trial is a Phase 2, open label trial of LVAD patients randomized to either apixaban or warfarin therapy. Patients randomized to apixaban will be started on a dose of 5 mg twice daily, while those randomized to warfarin will be managed to an INR goal of 2.0-2.5. All patients will be treated with aspirin 81mg daily. We plan to randomize and follow up to 40 patients for 24 weeks to evaluate the primary outcome of freedom from death or hemocompatibility related adverse events (HRAEs) (stroke, device thrombosis, bleeding, aortic root thrombus, and arterial non-CNS thromboembolism). DOAC LVAD will establish the feasibility of apixaban anticoagulant therapy in LVAD patients. Clinicaltrials.gov: NCT04865978.

Short-term Retention of Patient and Caregiver Ventricular Assist Device Self-care Skills after Simulation-based Mastery Learning

Background

We developed a simulation-based mastery learning (SBML) curriculum that boosted self-care skills for patients with a ventricular assist device (VAD). In this study, we evaluated short-term skills retention.

Methods

We assessed skill retention among patients and caregivers who participated in VAD self-care SBML at a tertiary care center. We compared discharge skills tests (immediately after completing SBML) to 1- and 3-month follow-up tests to assess skill retention.

Results

Fifteen patients and 15 caregivers completed discharge and follow-up testing. Skills were largely retained at 1- and 3-months.

Conclusions

SBML results in short-term retention of VAD self-care skills.

Timing of Gastrointestinal Bleeding After Implantation of Left Ventricular Assist Devices Associates With Anatomic Location, Presentation, and Management

BACKGROUND & AIMS

Continuous-flow left ventricular assist devices (LVADs) for advanced heart failure have been associated with gastrointestinal bleeding (GIB). We examined the association between time of GIB after LVAD implantation and bleeding location (determined by endoscopy), etiology, and patient outcomes.

METHODS

We performed a retrospective study of consecutive patients who underwent implantation of continuous-flow LVADs from 2008 through 2015. We analyzed data on anatomic location of GIB, etiology, length of hospital stay, transfusion requirement, time to endoscopy, and readmission to the hospital within 30 days (30-day readmission).

RESULTS

GIB developed in 59 of the 271 patients (22%). Higher proportions of patients with GIB during their index hospitalization for LVAD implantation had upper or lower GIB (86.7%) than patients with GIB during a subsequent hospitalization (50.0%; P = .013). Patients with GIB during their index hospitalization also had lower rates of middle GIB (0 vs 20.5%; P = .052), higher rates of overt GIB (100% vs 63.6%; P = .006), longer hospital stays (24 days vs 11 days; P < .001), and more transfusions before endoscopy (7 units vs 4 units; P = .021) than patients with GIB during a subsequent hospitalization. There were no significant differences between groups in time to endoscopy (2 days vs 2.5 days) or 30-day readmission (6.7% vs 9.3%). Angiodysplasias were identified in 100% of patients with middle GIB compared to 48.5% of patients with upper or lower GIB (P < .001) in whom a bleeding lesion was identified.

CONCLUSION

In a retrospective study of patients who underwent implantation of continuous-flow LVADs, we found that timing of GIB associates with the location and severity of bleeding. Although patients with LVADs have an overall increase in risk of middle GIB, patients with GIB during their index LVAD hospitalization should undergo initial evaluation by upper endoscopy and colonoscopy, due to insufficient time for development of small bowel angiodysplasias. Patients who later develop GIB should be evaluated early for middle GI bleeding.

The Effect of Judge Selection on Standard Setting Using the Mastery Angoff Method during Development of a Ventricular Assist Device Self-Care Curriculum

Background

Patients and caregivers need to perform ventricular assist device (VAD) self-care safely to help prevent complications (e.g., infection). We developed a VAD self-care simulation-based mastery learning (SBML) curriculum. We determined optimal minimum passing scores (MPSs) and evaluated effects of judge selection.

Methods

A multidisciplinary team created a VAD self-care SBML curriculum including simulated skills and knowledge examinations. Patients, caregivers, VAD coordinators, and physicians were expert judges who determined MPSs using the Mastery Angoff method.

Results

MPSs for the skills and knowledge examinations were high (range = 94-99% and 97% correct), respectively. Judges closely agreed on MPSs.

Conclusions

Stakeholders set stringent MPSs for high-stakes VAD self-care.

Effects of Transient Exposure to High Shear on Neutrophil Rolling Behavior

Introduction

Neutrophils display an array of behaviors ranging from rolling and migration to phagocytosis and granule secretion. Several of these behaviors are modulated by the local shear conditions. In the normal circulation, neutrophils experience shear rates from approximately 10-2,000 s^-1. However, neutrophils are also exposed to pathological shear levels in natural conditions such as severe stenosis and arteriosclerosis, as well as in blood-contacting devices such as ventricular assist devices (VADs) and hemodialysis machines. The effects of transiently (< 1 sec) exposing neutrophils to abnormally high shear rates (>3,000 s^-1) are not well understood.

Methods

We developed a set of microfluidic devices capable of exposing neutrophils to high shear rates for short durations (100-400 msec). Suspensions of isolated neutrophils were perfused through the devices and their rolling velocities on P-selectin were analyzed before and after shear exposure.

Results

We observed a significant increase in neutrophil rolling velocities on P-selectin coated regions following transient high shear exposure. The magnitude of the rolling velocity increase was dependent upon the duration of high shear exposure and became statistically significant for exposure times of 310 msec or longer. When polystyrene beads coated with a glycosulfopeptide that mimics the binding region of P-selectin glycoprotein ligand-1 (PSGL-1) were perfused through the devices, no change between the pre-shear and post-shear rolling velocities was observed.

Conclusions

These results suggest that high shear levels alter normal neutrophil rolling behavior and are important for understanding neutrophil biology in high shear conditions, as well as for improving medical device performance.

Pediatric Quality of Life while Supported with a Ventricular Assist Device

OBJECTIVE

Ventricular assist devices (VADs) have emerged as an important treatment option for bridging pediatric patients with heart failure to transplant. VADs have shown improved survival; however, the pediatric quality of life (QoL) while on VAD support is unknown. We aimed to evaluate the QoL of our pediatric patients while supported with a VAD.

DESIGN

In this prospective study, pediatric patients who underwent VAD placement, and their parents, were administered a generic Pediatric Quality of Life Inventory (PedsQL) 4.0 pre-VAD implant, when feasible, after the acute postoperative period, and then periodically until heart transplant or death. Their final scores while on support were compared with three previously reported groups: healthy controls, outpatients with severe heart disease, and children after heart transplant.

RESULTS

From January 2008 to July 2014, 13 pediatric patients required VAD support greater than 2 weeks and completed a PedsQL. The mean age at implant was 10.0 ± 4.2 years and median duration of support was 1.6 (0.5-19.7) months. Eleven (85%) patients survived to transplant with one (8%) patient remaining alive on support. The median duration of support prior to their final PedsQL was 1.4 (0.5-11.4) months. Patients self-reported significantly (P < .05) lower total and physical QoL scores when compared with all three comparison groups. Self-reported psychosocial QoL scores were significantly lower than healthy controls only. Parent proxy-reported scores were significantly lower than all three comparison groups for all three categories (P < .05).

CONCLUSIONS

A large deficit exists in the total QoL of pediatric patients supported by a VAD compared with outpatient management of severe heart disease or postheart transplant patients; however, VAD patients do represent a group with more severe heart failure. Improvements in QoL must be made, as time spent with a VAD will likely continue to increase.

Pre-clinical Implants of the Levitronix PediVAS® Pediatric Ventricular Assist Device - Strategy for Regulatory Approval

The PediVAS blood pump is a magnetically levitated centrifugal pump designed for pediatric bridge-to-decision or bridge-to-recovery in pediatric patients from 3-20kg in weight. In preparation for submission of an investigational device exemption (IDE) application, we completed a final six-animal series of pre-clinical studies. The studies were conducted under controlled conditions as prescribed by the recently released FDA guidance document for animal studies for cardiovascular devices. Three 30-day chronic left ventricular support studies were completed in a juvenile lamb model to demonstrate the safety and hemocompatibility of the PediVAS pump. Three additional 8-hour acute biventricular support studies were performed to demonstrate the feasibility of this approach from a hemodynamic and systems standpoint. It is estimated that 50% of pediatric patients who require left ventricular support also require right ventricular support. All studies were successfully completed without complications, device malfunctions, or adverse events. End-organ function was normal for the chronic studies. We noted small surface lesions on one kidney from each chronic study as well as the presence of ring thrombus on connectors, as expected for these types of studies in animal models. The strategy and challenges imposed by performing a controlled cardiovascular device study in a juvenile lamb model are discussed. We believe that these successful implants demonstrate safety and performance for the PediVAS device for support of an IDE application to initiate human clinical trials and provide a roadmap for other researchers.