Diagnosis and Management of LVAD Thrombosis

Left ventricular functional improvement appears to contribute to lower rates of device thrombosis in patients on durable mechanical circulatory support

By unloading the failing heart, left ventricular (LV) assist devices (LVADs) provide a favorable environment for reversing adverse structural and functional cardiac changes. Prior reports have suggested that an improved native LV function might contribute to the development of LVAD thrombosis. We used the Interagency Registry for Mechanically Assisted Circulatory Support and found that LV functional improvement is associated with a lower risk for device thrombosis. The risk for cerebrovascular accident and transient ischemic attack was comparable across post-LVAD LV function subgroups, while the risk of hemolysis was lower in subgroups of patients with better LV function on LVAD support.

Controversies and challenges of coil embolization for intracranial aneurysm in a continuous-flow LVAD implanted patient: A case report

Background

Continuous-flow left ventricular assist device (CF-LVAD) technology has rapidly developed to support the failing heart refractory to standard medical treatments. Although the expected prognosis has improved dramatically, ischemic and hemorrhagic strokes are possible complications and the leading causes of death in the CF-LVAD population.

Case Description

We encountered a case of an unruptured large internal carotid aneurysm in a patient with a CF-LVAD. Following a detailed discussion of his expected prognosis, the risk of aneurysm rupture, and the inherited risk of aneurysm treatment, coil embolization was performed without adverse events. The patient remained recurrence-free for 2-year postoperatively.

Conclusion

This report illustrates the feasibility of coil embolization in a CF-LVAD recipient and emphasizes the necessity of vigilant consideration of whether to intervene in an intracranial aneurysm after CF-LVAD implantation. We confronted several challenges during the treatment: optimal endovascular technique, management of antithrombotic drugs, safe arterial access, desirable perioperative imaging modalities, and prevention of ischemic complications. This study aimed to share this experience.

Long-Term Benefit of Mechanical Thrombectomy for Acute Ischemic Stroke in Patients with a Left Ventricular Assist Device: A Single-Center Retrospective Study

OBJECTIVE

Left ventricular assist devices (LVADs) are an epoch-making treatment option for patients with severe heart failure; however, the patients occasionally experience severe acute ischemic strokes (AISs). Although mechanical thrombectomy is considered as an effective treatment for severe AIS in patients with LVADs, there remains a paucity of data on the long-term outcomes. This study aimed to investigate the acute-phase efficacy and long-term outcomes of mechanical thrombectomy for AIS patients with LVADs.

METHODS

We retrospectively reviewed 9 cases in 8 patients with LVADs who developed AIS and underwent mechanical thrombectomy from July 2014 to November 2021 at our hospital. Clinical information, including the National Institutes of Health Stroke Scale score and modified Rankin Scale score before and after thrombectomy, the details of procedures, and the long-term outcomes after thrombectomy, was retrospectively reviewed and statistically analyzed.

RESULTS

Effective recanalization was achieved in 89% of the 9 cases. The median National Institutes of Health Stroke Scale score improved from 12 (range, 8-29) to 5 (range, 0-29) after mechanical thrombectomy. The median total follow-up duration was 1327 (range, 78-2659) days. Of the 8 patients, 3 patients underwent heart transplantation, and the LVAD was removed after recovery of the patient's heart function. One patient awaited heart transplantation.

CONCLUSIONS

This study revealed the long-term benefit of mechanical thrombectomy for AIS in patients with LVADs, eventually achieving 50% of independence from LVADs.

Medical Management of Recurrent Left Ventricular Assist Device Thrombosis in a Patient With Biventricular Assist Devices

Ventricular assist device (VAD) pump thrombosis is a known complication and while the preferred standard treatment is surgical pump exchange this procedure is not without risk and for some patients the risks are prohibitive. This is a case of a 68-year-old female with bilateral HeartWare ventricular assist devices (HVAD) implanted as destination therapy who presented with signs of recurrent pump thrombosis. Surgical pump exchange was deemed to confer prohibitive risk due to her underlying medical co-morbidities and therefore not an option for treatment. After careful consideration of possible options for treatment, she received systemic thrombolysis (Alteplase 5 mg IV bolus followed by 3 mg/hour infusion for 10 hours through a central line) which was successful. This case highlights, not only the rarity of bilateral VADs as destination therapy, but also demonstrates the safety and efficacy of using systemic thrombolytics in patients with bilateral HVADs for treatment of pump thrombosis.

Fully printed prothrombin time sensor for point-of-care testing

With an increasing number of patients relying on blood thinners to treat medical conditions, there is a rising need for rapid, low-cost, portable testing of blood coagulation time or prothrombin time (PT). Current methods for measuring PT require regular visits to outpatient clinics, which is cumbersome and time-consuming, decreasing patient quality of life. In this work, we developed a handheld point-of-care test (POCT) to measure PT using electrical transduction. Low-cost PT sensors were fully printed using an aerosol jet printer and conductive inks of Ag nanoparticles, Ag nanowires, and carbon nanotubes. Using benchtop control electronics to test this impedance-based biosensor, it was found that the capacitive nature of blood obscures the clotting response at frequencies below 10 kHz, leading to an optimized operating frequency of 15 kHz. When printed on polyimide, the PT sensor exhibited no variation in the measured clotting time, even when flexed to a 35 mm bend radius. In addition, consistent PT measurements for both chicken and human blood illustrate the versatility of these printed biosensors under disparate operating conditions, where chicken blood clots within 30 min and anticoagulated human blood clots within 20-100 s. Finally, a low-cost, handheld POCT was developed to measure PT for human blood, yielding 70% lower noise compared to measurement with a commercial potentiostat. This POCT with printed PT sensors has the potential to dramatically improve the quality of life for patients on blood thinners and, in the long term, could be incorporated into a fully flexible and wearable sensing platform.

Left Ventricular Assist Device as Destination Therapy: a State of the Science and Art of Long-Term Mechanical Circulatory Support

PURPOSE OF REVIEW

The purpose of this review is to synthesize and summarize recent developments in the care of patients with end-stage heart failure being managed with a left ventricular assist device (LVAD) as destination therapy.

RECENT FINDINGS

Although the survival of patients treated with LVAD continues to improve, the rates of LVAD-associated complication, such as right ventricular failure, bleeding complications, and major infection, remain high, and management of these patients remains challenging. The durability and hemocompatibility of LVAD support have greatly increased in recent years as a result of new technologies and novel management strategies. Challenges remain in the comprehensive care of patients with destination therapy LVADs, including management of comorbidities and optimizing patient function and quality of life.

Percutaneous Intervention for Left Ventricular Assist Device Outflow Obstruction

Left ventricular assist devices (LVADs) are used to support patients with advanced systolic heart failure (HF). These patients might develop LVAD dysfunction and consequent HF symptoms. Occasionally, outflow graft obstruction is responsible for LVAD dysfunction. Here, we describe percutaneous techniques to repair the outflow graft and avoid re-sternotomy.

Analysis of Patients with Ventricular Assist Devices Presenting to an Urban Emergency Department

Introduction

Left ventricular assist device (LVAD) insertion is an increasingly common intervention for patients with advanced heart failure; however, published literature on the emergency department (ED) presentation of this population is limited. The objective of this study was to characterize ED presentations of patients with LVADs with a focus on device-specific complications to inform provider education and preparation initiatives.

Methods

This was a retrospective chart review of all patients with LVADs followed at an urban academic medical center presenting to the ED over a five-year period (July 1, 2009, to June 30, 2014). Two abstractors reviewed 45 randomly selected charts to standardize the abstraction process and establish a priori categories for reason for presentation to the ED. Remaining charts were then divided evenly for review by one of the two abstractors. Primary outcomes for this study were (1) frequency of and (2) reason for presentation to the ED by patients with LVADs.

Results

Of 349 patients with LVADs identified, 143 (41.0%) had ED encounters during the study period. There were 620 total ED encounters, (range 1 to 32 encounters per patient, median=3, standard deviation=5.3). Among the encounters, 431 (69.5%) resulted in admission. The most common reasons for presentation were bleeding (e.g., gastrointestinal, epistaxis) (182, 29.4%); infection (127, 20.5%); heart failure exacerbation (68, 11.0%); pain (56, 9.0%); other (45, 7.3%); and arrhythmias (40, 6.5%). Fifty-two encounters (8.4%) were device-specific; these patients frequently presented with abnormal device readings (37, 6.0%). Interventions for device-specific presentations included anticoagulation regimen adjustment (16/52, 30.8%), pump exchange (9, 17.3%), and hardware repair (6, 11.5%). Pump thrombosis occurred in 23 cases (3.7% of all encounters). No patients required cardiopulmonary resuscitation or died in the ED.

Conclusion

This is the largest study known to the investigators to report the rate of ED presentations of patients with LVADs and provide analysis of device-specific presentations. In patients who do have device-specific ED presentations, pump thrombosis is a common diagnosis and can present without device alarms. Specialized LVAD education and preparation initiatives for ED providers should emphasize the recognition and management of the most common and critical conditions for this patient population, which have been identified in this study as bleeding, infection, heart failure, and pump thrombosis.

In vitro study for the evaluation of transluminal aspiration as a novel treatment option for thrombosis in the HeartWare HVAD

INTRODUCTION:

Pump thrombosis of left ventricular assist devices remains a devastating complication with high morbidity and mortality. Despite the improvements made, the matter affects many patients and the treatment options are limited to thrombolysis and surgical replacement. An alternative approach using the aspiration Indigo catheter was tested.

METHODS:

An Indigo thrombectomy catheter was used within an in vitro model to assess the direct aspiration of prefabricated clots from three different positions within the HeartWare HVAD (inlet, outlet, and housing). The experiments were conducted with a straight and an angled catheter. The aspiration pressure was constant. The flow, power consumption, and pressure head of the left ventricular assist devices were measured at pre-defined measuring points.

RESULTS:

The device was more effective (success rate 71%) at inlet and outlet of the left ventricular assist device. In addition, the duration of aspiration and the aspiration volume were shorter in comparison to the aspiration in the housing (inlet M = 19.75 s, outlet M = 60.50 s, and housing M = 38.75 s). Moreover, the aspiration volume was associated with the aspiration duration and the weight of thrombi but not with their volume. Noteworthy, the angled catheter showed an improved performance compared to the straight one (67%-33%). The recorded parameters showed no major changes during the use of the catheter. After application of the Indigo catheter, flow and pressure head of the pump could be restored.

CONCLUSIONS:

The aspiration system showed promising results under specific conditions for the treatment of pump thrombosis in an in vitro model. However, further examination, including in vivo experiments, will justify its effectiveness.

An acoustic method for systematic ventricular assist device thrombus evaluation with a novel artificial thrombus model

BACKGROUND

Pump thrombosis (PT) is still one of the major adverse events in patients supported with left ventricular assist devices. Nowadays, thrombus detection relies on clinical parameters like reoccurring heart failure symptoms, on changes in pump power consumption, and on laboratory parameters such as increased LDH and hemolysis. Once detected PT is most often persistent and refractory to medical therapy. We therefore designed a novel, non-invasive acoustic method for early pump thrombus detection in an in vitro artificial thrombus model.

METHODS

The study was performed in vitro using a mock circulation loop, artificial blood (water-glycerin) and artificial thrombus material (silicon) allowing for repeatable and defined testing. Tested ventricular assist device (VAD) type was HVAD (Medtronic). Three different thrombus locations were evaluated: on the tilted pad of the rotor, in the primary flow path, and in the secondary flow path beneath the rotor. After evaluating baseline parameters (no thrombus, n=20 for each pump), the influence of thrombi of seven different masses (no thrombus, 0.5-5.0 mg) on pump power consumption and acoustic emission of four HVAD devices was investigated via a microphone system (Sennheiser) and subsequent frequency spectrum analysis (n=12). The acoustic analysis algorithm included the number of frequency peaks recorded.

RESULTS

Measurements with thrombi on the tilted pad showed an increased number of frequency peaks with all thrombus sizes compared to baseline measurements without any thrombus (baseline: 32.7±7.4; 0.5 mg: 45.3±10.4 up to 5 mg: 80.4±5.5). Power consumption was relevantly elevated in 5mg thrombus measurement only (6.3±1.29 W compared to 4.9±0.14 W at baseline). Measurements with thrombi in the primary and secondary showed no relevant alteration in power consumption and frequency peak count.

CONCLUSIONS

We present an acoustic method that detects pump thrombi located on the tilted pad of the HVAD rotor requiring ten times less mass compared to thrombi detected by power consumption alterations used in current detection algorithms. Assuming that pump thrombi are growing over several days, the presented method may detect PT much earlier thereby increasing efficacy of medical therapy and helping to avoid pump exchange.

Diagnosis and Treatment Algorithm for Blood Flow Obstructions in Patients With Left Ventricular Assist Device

BACKGROUND

Thrombosis is an uncommon, but severe complication of left ventricular assist devices (LVADs).

OBJECTIVES

This study analyzed experience with obstruction of blood flow through the LVAD with the purpose of developing optimal diagnosis and treatment of LVAD-related thrombosis.

METHODS

Between October 2009 and July 2015, a total of 652 LVAD were implanted in 557 patients. Blood flow abnormalities in patients with LVAD (n = 524) were identified and classified as "high-power" and "low-flow" events.

RESULTS

Three types of late blood flow obstructions were identified: 1) pre-pump via thrombus obstructing the inflow cannula (26 events; 0.037 events per patient-year); 2) intra-pump (70 events; 0.1 events per patient-year); and 3) post-pump via thrombosis of the outflow graft or stenosis of the anastomosis to the aorta (4 events; 0.006 events per patient-year). Pre-pump obstruction was treated by washout maneuver in 9 cases (success rate, 100%), thrombolysis in 9 patients (success rate, 56%), and pump exchange in 9 cases (success rate, 100%); 1 patient died without treatment and 2 were weaned from LVAD. Intra-pump obstruction was treated by thrombolysis (n = 9; success rate, 33%), pump exchange (n = 53; success rate, 94%), and removal due to myocardial recovery (n = 3; success rate, 100%); 7 patients died without treatment and parameters spontaneously normalized in 2 cases. Post-pump obstruction was treated in 2 patients by stenting (success rate, 100%), and was left untreated in 2 cases.

CONCLUSIONS

We identified 3 types of LVAD-related blood flow obstruction, and developed an algorithm for optimal diagnosis and treatment.

Effective treatment with a new protocol using tissue-type plasminogen activator thrombolysis for pump thrombosis with the HVAD device

BACKGROUND:

Pump thrombosis is a major complication of the continuous flow left ventricular assist device. Pump exchange is seen as the therapeutic gold standard. In this study, we report on our experience with using tissue-type plasminogen activator thrombolysis for therapy of pump thrombosis.

METHODS:

We report on our experience with treatment of continuous flow left ventricular assist device pump thrombosis with the HVAD using tissue-type plasminogen activator thrombolysis in nine patients with 16 thrombotic events. In all events we used a uniform treatment protocol.

RESULTS:

All patients presented with a sufficient anticoagulation and had symptoms of heart failure. However, all patients were haemodynamically stable. Six of nine patients presented with a mean arterial pressure above 85 mm Hg and every patient presented with an infection. In all events we achieved short-term success with resolution of the pump thrombosis within a median time of nine hours. Three of nine patients developed recurrent pump thrombosis after >60 days. Besides one case of nonfatal intracranial haemorrhage and one case of minor bleeding, there were no adverse events.

CONCLUSION:

Our data indicates that using a uniform treatment protocol that builds on usage of tissue-type plasminogen activator thrombolysis might be an effective tool for treatment of continuous flow left ventricular assist device pump thrombosis in haemodynamically stable patients. Additionally, our data indicates that infection may be a potential trigger for pump thrombosis.

Acoustic Characterization of Axial Flow Left Ventricular Assist Device Operation In Vitro and In Vivo

The use of left ventricular assist devices (LVADs), implantable pumps used to supplement cardiac output, has become an increasingly common and effective treatment for advanced heart failure. Although modern continuous-flow LVADs improve quality of life and survival more than medical management of heart failure, device malfunction remains a common concern. Improved noninvasive methods for assessment of LVAD function are needed to detect device complications. An electronic stethoscope was used to record sounds from the HeartMate II axial flow pump in vitro and in vivo. The data were then uploaded to a computer and analyzed using two types of acoustic analysis software. Left ventricular assist device acoustics were quantified and were related to pump speed, acoustic environment, and inflow and outflow graft patency. Peak frequency values measured in vivo were found to correlate strongly with both predicted values and in vitro measurements (r > 0.999). Plots of the area under the acoustic spectrum curve, obtained by integrating over 50 Hz increments, showed strong correlations between in vivo and in vitro measurements (r > 0.966). Device thrombosis was found to be associated with reduced LVAD acoustic amplitude in two patients who underwent surgical device exchange.

Early thrombus formation in patient with HeartWare left ventricular assist device presenting with acute heart failure

Heart failure is one of the leading causes of mortality and morbidity in the world. Heart transplantation is still the gold standard therapy despite emerging treatment options. Due to the limited number of available donors, the use of ventricular assist devices has increased. However, increasing incidences of complications are observed with using these devices. In this article, surgical treatment of a huge mobile thrombus formation in an inflow cannula due to ineffective anticoagulation in a 59 year-old man who received a HeartWare ventricular assist device because of ischemic cardiomyopathy is presented.

Left Ventricular Assist Devices in the Management of Heart Failure

Mechanical circulatory support has emerged as an important therapy for advanced heart failure, with more than 18,000 continuous flow devices implanted worldwide to date. These devices significantly improve survival and quality of life and should be considered in every patient with end-stage heart failure with reduced ejection fraction who has no other life-limiting diseases. All candidates for device implantation should undergo a thorough evaluation in order to identify those who could benefit from device implantation. Long-term management of ventricular assist device patients is challenging and requires knowledge of the characteristic complications with their unique clinical presentations.