Impact of adverse events on ventricular assist device outcomes. Curr Heart Fail Rep. 2013;10:89-100. [PMID: 23314865 DOI: 10.1007/s11897-012-0127-3]

MitraClip implantation followed by insertion of a left ventricular assist device in patients with advanced heart failure

Aims

Mitral valve regurgitation (MR) is common in patients with advanced heart failure (HF). Percutaneous mitral valve repair (PMVR) via MitraClip (MC) has emerged as a feasible treatment strategy for these high‐risk patients. However, as HF often further progresses, there is a frequent need for left ventricular assist device (LVAD) implantation in these patients. We aimed to investigate whether prior MC implantation affects the subsequent LVAD implantation and outcome.

Methods and results

Thirty‐seven patients with advanced HF and significant MR who underwent LVAD implantation were retrospectively analysed. Follow‐up data were collected at 1 year after LVAD implantation. Primary endpoint was all‐cause mortality. Secondary endpoint included peri‐operative parameters and clinical development depicted as New York Heart Association (NYHA) class and Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) level. Seventeen patients initially received a MC device (MC group), resulting in a significant reduction in MR grade. After MC, NYHA class and INTERMACS level further worsened, leading to subsequent LVAD implantation after a median time of 475 days in the MC group. At LVAD implantation, overall characteristics were comparable with those of the patients undergoing LVAD implantation without prior MC placement (no‐MC group). Procedural data revealed a higher incidence of right ventricular (RV) failure needing mechanical RV assistance and a longer need for nitric oxide ventilation in the MC group after LVAD implantation. One‐year survival was slightly better in the no‐MC group compared with the MC group [41% (n = 7/17) vs. 65% (n = 13/20); P = 0.15], albeit event‐free survival was comparable between both groups, MC and no‐MC.

Conclusions

LVAD implantation after MC is feasible and safe. However, in patients with advanced HF and severe MR, PMVR may only delay a needed LVAD implantation and thereby lead to poorer peri‐operative RV function and impaired outcome. Arguably, these patients might benefit from the timely management of advanced HF by the means of early LVAD implantation or heart transplantation.

Left ventricular assist device-associated infections: incidence and risk factors

Background

Left ventricular assist device (LVAD)-associated infections are major complications that can lead to critical outcomes. The aims of this study were to assess the incidence of and to determine the risk factors for LVAD-associated infections.

Methods

We included all consecutive patients undergoing LVAD implantation between January 1, 2010, and January 1, 2019, in a single institution. Infection-related data were retrospectively collected by review of patient's medical files. LVAD-associated infections were classified into three categories: percutaneous driveline infections, pocket infections and pump and/or cannula infections.

Results

We enrolled 72 patients. Twenty-one (29.2%) patients presented a total of 32 LVAD-associated infections. Eight (38.1%) patients had more than one infection. Five (62.5%) pocket infections and one (50.0%) pump and/or cannula infection were preceded by a driveline infection. The median delay between the operation and LVAD-associated infection was 6.5 (1.4-12.4) months. The probability of having a LVAD-associated infection at one year after receiving an implant was 26.6% (95% CI: 17.5-40.5%). Percutaneous driveline infections represented 68.7% of all LVAD-associated infections. Staphylococcus aureus and coagulase-negative staphylococci were the predominant bacteria in LVAD-associated infections (53.1% and 15.6%, respectively). Hospital length of stay (sdHR =1.22 per 10 days; P=0.001) and postoperative hemodialysis (sdHR =0.17; P=0.004) were statistically associated with infection. Colonization with multidrug-resistant bacteria was more frequent in patients with LVAD-associated infections than in others patients (42.9% vs. 15.7%; P=0.013).

Conclusions

LVAD-associated infections remain an important complication and are mostly represented by percutaneous driveline infections. Gram-positive cocci are the main pathogens isolated in microbiological samples. Patients with LVAD-associated infections are more frequently colonized with multidrug-resistant bacteria.

Outcomes in Patients with Left Ventricular Assist Devices, Pacemakers, and Implantable Cardioverter Defibrillators Undergoing Single Balloon Enteroscopy

OBJECTIVES

Obscure overt gastrointestinal bleeding can be challenging to evaluate in patients with electronic cardiac devices such as continuous flow left ventricular assist devices (LVADs), pacemakers (PPMs), and implantable cardioverter defibrillators (ICDs). Limited data exist on the utility and safety of single balloon enteroscopy (SBE) in patients with cardiac devices. We aimed to evaluate the safety, efficacy, diagnostic, and therapeutic outcomes of the aforementioned devices in patients undergoing SBE.

METHODS

A retrospective study was performed using the medical records of 57 patients undergoing SBE at our institution from 2010 to 2014. Patients were divided into two groups: those with cardiac devices and those without. Data on comorbidities, complications, findings, diagnostic, and therapeutic yield were compared. t Test and logistic regression assessed the association between dependent and independent variables. For continuous data, the results were summarized as mean difference and standard deviation. For dichotomous data, the results were summarized as odds ratio and 95% confidence intervals.

RESULTS

The overall age in patients with cardiac devices was 67.89 ± 6.96 versus 66.03 ± 11.95 years in the control. The cardiac device group was composed of 42.1% women; the control comprised 21.1% women. There were 19 patients with cardiac devices; 8 (LVAD + ICD), 1 (LVAD + PPM + ICD), 2 (PPM + ICD), 6 (PPM), 2 (ICD); 38 patients were in the control group. Patients with cardiac devices were hospitalized more often than patients without devices; this finding was not statistically significant (odds ratio 1.826, 95% confidence interval 0.544-6.128, P = 0.389). Procedure times were longer in the cardiac device group, 65.16 ± 49.92 minutes, when compared with the control, 57.40 ± 20.42, but it also did not reach statistical significance (mean difference 7.758, 95% confidence interval -11.360 to 26.876, P = 0.049). There was no statistically significant difference in major or minor events between patients with cardiac devices and the control group. Diagnostic and therapeutic yield and rebleeding rates were similar across both groups.

CONCLUSIONS

Patients in the cardiac device group did not appear to be at any more significant risk than those without cardiac devices. Furthermore, diagnostic and therapeutic yield and rebleeding rates appear to be similar across both groups. Clinicians may perform SBE in these patients safely and effectively, with good overall outcomes.

Utility and correlation of known anticoagulation parameters in the management of pediatric ventricular assist devices

AIM

To assess utility and correlation of known anticoagulation parameters in the management of pediatric ventricular assist device (VAD).

METHODS

Retrospective study of pediatric patients supported with a Berlin EXCOR VAD at a single pediatric tertiary care center during a single year.

RESULTS

We demonstrated associations between activated thromboplastin time (aPTT) and R-thromboelastography (R-TEG) values (rs = 0.65, P < 0.001) and between anti-Xa assay and R-TEG values (rs = 0.54, P < 0.001). The strongest correlation was seen between aPTT and anti-Xa assays (rs = 0.71, P < 0.001). There was also a statistically significant correlation between platelet counts and the maximum amplitude of TEG (rs = 0.71, P < 0.001). Importantly, there was no association between dose of unfractionated heparin and either measure of anticoagulation (aPTT, anti-Xa or R-TEG value).

CONCLUSION

This study suggests that while there is strong correlation between aPTT, anti-Xa assay and R-TEG values for patients requiring VAD support, there is a lack of relevant correlation between heparin dose and degree of effect. This raises concern as various guidelines continue to recommend using these parameters to titrate heparin therapy.

The platelet hammer: In vitro platelet activation under repetitive hypershear

Mechanical circulatory support (MCS) devices, such as ventricular assist devices and the total artificial heart, have emerged as a vital therapy for advanced and end-stage heart failure. However, MCS patients face life-long antiplatelet and anticoagulant therapy to minimize thrombotic complications resulting from the dynamic and supraphysiologic device-associated shear stress conditions, whose effect on platelet activation is poorly understood. We repeatedly exposed platelets to average shear stresses up to 1000 dyne/cm(2) for as short as 25 ms in the "platelet hammer," a syringe-capillary viscometer. Platelet activation state was measured using a modified prothrombinase assay and morphological changes analyzed using scanning electron microscopy. An increase in stress accumulation (SA), the product of shear stress and exposure time, led to an increase in the platelet activation state and post-high shear platelet activation rate, or sensitization. A significant increase in platelet activation state was observed beyond an SA of 1500 dyne-s/cm(2), with a marked increase in pseudopod length visible beyond an SA of 1000 dyne-s/cm(2). The platelet hammer may be used to study other shear-dependent pathologies and may ultimately enhance the safety and effectiveness of MCS devices and objective antithrombotic pharmacotherapy management.

Visualization and analysis of biomaterial-centered thrombus formation within a defined crevice under flow

The blood flow pathway within a device, together with the biomaterial surfaces and status of the patient's blood, are well-recognized factors in the development of thrombotic deposition and subsequent embolization. Blood flow patterns are of particular concern for devices such as blood pumps (i.e. ventricular assist devices, VADs) where shearing forces can be high, volumes are relatively large, and the flow fields can be complex. However, few studies have examined the effect of geometric irregularities on thrombus formation on clinically relevant opaque materials under flow. The objective of this study was to quantify human platelet deposition onto Ti6Al4V alloys, as well as positive and negative control surfaces, in the region of defined crevices (∼50-150 μm in width) that might be encountered in many VADs or other cardiovascular devices. To achieve this, reconstituted fresh human blood with hemoglobin-depleted red blood cells (to achieve optical clarity while maintaining relevant rheology), long working optics, and a custom designed parallel plate flow chamber were employed. The results showed that the least amount of platelet deposition occurred in the largest crevice size examined, which was counterintuitive. The greatest levels of deposition occurred in the 90 μm and 53 μm crevices at the lower wall shear rate. The results suggest that while crevices may be unavoidable in device manufacturing, the crevice size might be tailored, depending on the flow conditions, to reduce the risk of thromboembolic events. Further, these data might be used to improve the accuracy of predictive models of thrombotic deposition in cardiovascular devices to help optimize the blood flow path and reduce device thrombogenicity.

Feasibility study of particulate extracellular matrix (P-ECM) and left ventricular assist device (HVAD) therapy in chronic ischemic heart failure bovine model

Myocardial recovery with left ventricular assist device (LVAD) support is uncommon and unpredictable. We tested the hypothesis that injectable particulate extracellular matrix (P-ECM) with LVAD support promotes cell proliferation and improves cardiac function. LVAD, P-ECM, and P-ECM + LVAD therapies were investigated in chronic ischemic heart failure (IHF) calves induced using coronary embolization. Particulate extracellular matrix emulsion (CorMatrix, Roswell, GA) was injected intramyocardially using a 7 needle pneumatic delivery tool. Left ventricular assist devices (HVAD, HeartWare) were implanted in a left ventricle (LV) apex to proximal descending aorta configuration. Cell proliferation was identified using BrdU (5 mg/kg) injections over the last 45 treatment days. Echocardiography was performed weekly. End-organ regional blood flow (RBF) was quantified at study endpoints using fluorescently labeled microspheres. Before treatment, IHF calves had an ejection fraction (EF) of 33 ± 2% and left ventricular end-diastolic volume of 214 ± 18 ml with cardiac cachexia (0.69 ± 0.06 kg/day). Healthy weight gain was restored in all groups (0.89 ± 0.03 kg/day). EF increased with P-ECM + HVAD from 36 ± 5% to 75 ± 2%, HVAD 38 ± 4% to 58 ± 5%, and P-ECM 27 ± 1% to 66 ± 6%. P-ECM + HVAD demonstrated the largest increase in cell proliferation and end-organ RBF. This study demonstrates the feasibility of combined LVAD support with P-ECM injection to stimulate new cell proliferation and improve cardiac function, which warrants further investigation.

Chronic outpatient management of patients with a left ventricular assist device

The use of mechanical circulatory support (MCS) as treatment for advanced heart failure (HF) has grown exponentially over the past 15 years. The continuous flow left ventricular assist device (CF-LVAD) has become the most used form of MCS in advanced HF, especially since approval of use as destination therapy (DT) and with the lack of organ availability. Long-term survival has improved and diligent outpatient management is thus particularly critical to achieve optimal outcomes. This review will discuss outpatient management strategies for patients with HF and a left ventricular assist device (LVAD).

Repetitive Hypershear Activates and Sensitizes Platelets in a Dose-Dependent Manner

Implantation of mechanical circulatory support (MCS) devices-ventricular assist devices and the total artificial heart-has emerged as a vital therapy for advanced and end-stage heart failure. Unfortunately, MCS patients face the requirement of life-long antiplatelet and anticoagulant therapy to combat thrombotic complications resulting from the dynamic and supraphysiologic shear stress conditions associated with such devices, whose effect on platelet activation is poorly understood. We developed a syringe-capillary viscometer-the "platelet hammer"-that repeatedly exposed platelets to average shear stresses up to 1000 dyne/cm(2) for as short as 25 ms. Platelet activation state was measured using a modified prothrombinase assay, with morphological changes analyzed using scanning electron microscopy. We observed an increase in platelet activation state and post-high shear platelet activation rate, or sensitization, with an increase in stress accumulation (SA), the product of shear stress and exposure time. A significant increase in platelet activation state was observed beyond an SA of 1500 dyne-s/cm(2) , with a marked increase in pseudopod length visible beyond an SA of 1000 dyne-s/cm(2) . Utility of the platelet hammer extends to studies of other shear-dependent pathologies, and may assist development of approaches to enhance the safety and effectiveness of MCS devices and objective antithrombotic pharmacotherapy management.

Left ventricular assist device management and complications

Patients on long-term left ventricular assist device (LVAD) support present unique challenges in the intensive care unit. It is crucial to know the status of end-organ perfusion, which may require invasive hemodynamic monitoring with a systemic arterial and pulmonary artery catheter. Depending on the indication for LVAD support (bridge to decision or cardiac transplantation vs destination therapy), it is important to readdress goals of care with the patient (if possible) and their family after major events have occurred that challenge the survival of the patient.

Antithrombotic therapy for ventricular assist devices in children: do we really know what to do?

The use of ventricular assist devices (VADs) in children is increasing. Stroke and device-related thromboembolism remain the most feared complications associated with VAD therapy in children. The presence of a VAD causes dysregulation of hemostasis due to the presence of foreign materials and sheer forces intrinsic to the device resulting in hypercoagulability and potentially life-threatening thrombosis. The use of antithrombotic therapy in adults with VADs modulates this disruption in hemostasis, decreasing the risk of thrombosis. Yet, differences in hemostasis in children (developmental hemostasis) may result in variances in dysregulation by these devices and preclude the use of adult guidelines. Consequently, pediatric device studies must include safety and efficacy estimates of device-specific antithrombotic therapy guidelines. This review will discuss mechanisms of hemostatic dysregulation as it pertains to VADs, goals of VAD antithrombotic therapy for children and adults, and emerging antithrombotic strategies for VAD use in children.

Spectroscopic and morphological characterization of inflow cannulas of left ventricular assist devices

Despite the consistent clinical data on the positive effects of left ventricular assist devices (LVADs) in the treatment of refractory heart failure, unfortunately these devices yet show some limitations such as the risk of stroke, infection, and device malfunction. The complex interplay between blood and the foreign material has a major role in the occurrence of these complications and biocompatibility of the inflow cannula would be pivotal in these terms. In this study, we carried out an in-depth physicochemical characterization of two commercially available LVADs by means of field emission gun scanning electron microscopy, energy dispersive X-ray, and X-ray photoelectron spectra. Our results show that, despite both pumps share the same physicochemical concepts, major differences can be identified in the surface nature, morphology, and chemical composition of their inflow cannulas.