Continuous-flow Left Ventricular Assist Devices Patients Research Articles

Novel echocardiographic parameters of aortic insufficiency in continuous-flow left ventricular assist devices and clinical outcome

The aim of this study was to evaluate the prognostic performance of novel echocardiographic (transthoracic echocardiography, or TTE) parameters for grading aortic insufficiency (AI) severity in patients with continuous-flow left ventricular assist devices (CF-LVADs). The development of AI after CF-LVAD implantation is common, although the clinical significance remains unclear. We previously described novel TTE parameters that outperformed traditional TTE parameters in grading AI severity in these patients. CF-LVAD patients with varying degrees of AI (N = 57) underwent Doppler TTE of the LVAD outflow cannula. Patients had AI severity graded by the novel parameters (systolic/diastolic velocity ratio and the diastolic acceleration of the LVAD outflow cannula) and the traditional vena contracta. The prognostic performance of novel and traditional AI parameters was determined by comparing rates of congestive heart failure re-admission, need for aortic valve intervention, urgent transplantation and death (composite end-points) for each parameter. Grading AI severity using novel AI parameters led to reclassification of 32% of patients from trace/mild AI to moderate or greater AI (N = 18). Using traditional AI parameters, there was no difference in the occurrence of the composite end-point between the moderate or greater group and the trace/mild group (1.50 vs 1.18 events/person, p = 0.46). With the novel AI parameters, there were significantly more events in the patients with moderate or greater AI compared to those with trace/mild AI (1.57 vs 0.13 events/person, p = 0.002). Novel parameters also better predicted the need for aortic valve intervention, urgent transplantation or death than traditional methods (p = 0.024 vs p = 0.343). In patients with CF-LVADs, traditional parameters tend to underestimate AI severity and future cardiac events. Novel AI TTE parameters are better able to discriminate AI severity and predict clinically meaningful outcomes.

(202) - Use of Long Acting Octreotide in an Outpatient Clinic Reduces the Rate of Gastro-Intestinal Bleeding in Continuous Flow LVAD Patients

(202) - Use of Long Acting Octreotide in an Outpatient Clinic Reduces the Rate of Gastro-Intestinal Bleeding in Continuous Flow LVAD Patients

Outcomes after stroke complicating left ventricular assist device

Stroke is one of the leading complications during continuous flow-left ventricular assist device (CF-LVAD) support. Risk factors have been well described, although less is known regarding treatment and outcomes. We present a large single-center experience on stroke outcome and transplant eligibility by stroke sub-type and severity in CF-LVAD patients. Between January 1, 2008, and April 1, 2015, 301 patients underwent CF-LVAD (266 HeartMate II [HM I], Thoratec Corp, Pleasanton, CA; 35 HeartWare [HVAD], HeartWare International Inc, Framingham, MA). Stroke was defined as a focal neurologic deficit with abnormal neuroimaging. Intracerebral hemorrhage (ICH) definition excluded sub-dural hematoma and hemorrhagic conversion of an ischemic stroke (IS). Treatment in IS included intra-arterial embolectomy when appropriate; treatment in ICH included reversal of coagulopathy. Stroke severity was measured using the National Institutes of Health Stroke Scale (NIHSS). Outcomes were in-hospital mortality and transplant status. Stroke occurred in 40 patients: 8 ICH (4 HM II, 4 HVAD) and 32 IS (26 HM II, 6 HVAD). Among 8 ICH patients, there were 4 deaths (50%), with NIHSS of 18.8 ± 13.7 vs 1.8 ± 1.7 in survivors (p = 0.049). Among 32 IS patients, 12 had hemorrhagic conversion and 5 were treated with intra-arterial embolectomy. There were 9 deaths (28%), with NIHSS of 16.2 ± 10.8 vs 7.0 ± 7.6 in survivors (p = 0.011). Among the 32 IS patients, 12 underwent transplant, and 1 is awaiting transplant. No ICH patients received a transplant. In-hospital mortality after stroke is significantly affected by the initial neurologic impairment. Patients with IS appear to benefit the most from in-hospital treatment and often make sufficient recovery to be able to progress to transplant.

Intractable Hematuria After Left Ventricular Assist Device Implantation: Can Lessons Learned from Gastrointestinal Bleeding Be Applied?

Patients with continuous-flow left ventricular assist devices (CF-LVADs) are at increased risk of bleeding. We reviewed our institutional experience with bleeding in the urinary tract after CF-LVAD implantation and quantified the impact on hospital resource utilization in comparison with bleeding in the gastrointestinal (GI) tract, the most commonly reported mucosal site of bleeding after LVAD implantation. Records were retrospectively reviewed for patients undergoing CF-LVAD implantation at our institution between October 2011 and April 2015. Major adverse events of gross hematuria and GI bleeding were identified, and patient demographics and hospital course were reviewed. Gross hematuria occurred in 3 of the 35 patients (8.6%) and in 5.1% of all hospitalizations for CF-LVAD patients. Severe hematuria occurred after traumatic urethral catheterization, urinary retention, or urologic surgery. Hospitalization for hematuria was six times less likely than hospitalization for GI bleeding; however, hematuria hospitalizations lasted 3.2 times longer than GI bleeding hospitalizations (17.0 vs. 5.3 days). Late recurrent gross hematuria occurred in all cases, with rehospitalization occurring after 109 ± 53 days. In conclusion, gross hematuria is an infrequent but morbid bleeding complication in CF-LVAD patients. Strategies to avoid this complication include strict avoidance of traumatic urethral catheterization and urinary retention in high-risk patients.

Blood pressure management in mechanical circulatory support.

Durable mechanical support has become widely available for end stage heart failure as destination therapy and as bridge to transplantation. The accurate measurement of blood pressure (BP) as well as the recognition and management of hypertension in patients with continuous flow left ventricular assist devices (CF-VADs) is an essential component of optimal clinical care. Strategies for the control of BP in CF-VAD patients are increasingly important as there is an evolving understanding of the connection between hypertension, pump output, and adverse outcomes. As clinical experience grows, optimal BP targets, as well as methods to measure BP in CF-VAD patients have been further defined.

Abstract 19271: Lack of Sufficient Pulsatile Flow in the Microvasculature May Contribute to Increased Microvascular Complications in Patients Implanted With Continuous Flow Left Ventricular Assist Devices

Background: In patients on continuous flow left ventricular assist devices (CF-LVAD) support, low pulsatility has been implicated in the development of microvascular complications such as gastrointestinal bleeds and strokes. The aim of this study was to measure and compare the microvascular flow profiles of both CF-LVAD patients and age matched healthy controls. Methods: The cuff based Mobil-O-Graph system (IEM) was used to measure supine blood pressure (BP) in 6 patients implanted with a CF-LVAD. Using the captured brachial pressures and associated waveform, the inbuilt ARCSolver algorithm was used to calculate central systolic and diastolic pressures, augmentation index (AIx) and aortic pulse wave velocity (aPWV). Pulsatility index (PI) of the central retinal (CR) and mid cerebral artery (MCA) was measured using a 12MHz linear probe with vivid-Q ultrasound and 2MHz transcranial Doppler ultrasound, respectively. Similar measurements were recorded in 13 healthy, age, mean pressure and aPWV matched controls. Results: Brachial and central pulse pressures were both significantly lower in CF-LVAD patients compared to controls. In addition, PI was significantly lower in the CF-LVAD group compared to controls in the CR and MCA (Table). Conclusion: Our data provide the first evidence that pulsatile flow is significantly lower in the microcirculation of CF-LVAD patients compared to healthy controls. This lack of pulsatile flow to appropriately stimulate the endothelium and replicate normal healthy haemodynamics, may in part be responsible for the increased risk of microvascular complications in CF-LVAD patients. As this is a pilot study, more mechanistic studies assessing macro and microvascular flow haemodynamics in CF-LVAD patients are needed to understand these associations further. Table.

Abstract 16373: Improved Prognostic Performance of Novel Parameters for Grading Aortic Insufficiency Severity in Patients With Left Ventricular Assist Devices

Background: The development of aortic insufficiency (AI) following continuous flow left ventricular assist device (CF-LVAD) implantation is common, although the clinical significance remains unclear. We previously described novel echocardiographic (TTE) parameters that outperformed traditional TTE parameters in grading AI severity in these patients. The aim of this study was to evaluate the prognostic performance of these parameters compared to traditional measurements. Methods: CF-LVAD patients with varying degrees of AI (N=57) underwent Doppler TTE of the LVAD outflow cannula. All patients had AI severity graded by our novel parameters (Systolic/Diastolic ratio and the diastolic acceleration of the LVAD outflow cannula) and traditional vena contracta. The prognostic performance of novel and traditional AI parameters was determined by comparing rates of hospital readmission, need for aortic valve intervention and/or urgent transplantation and death (primary endpoints) for each parameter. Results: Grading AI severity using novel AI parameters led to reclassification of 21% of patients from trace/mild AI to moderate or greater AI (N=12). Using traditional AI parameters, there was no difference in the occurrence of the primary endpoint between the trace/mild group and the moderate or greater group (1.08 vs. 0.89 events/person, p=0.39) (Figure 1A). With the novel AI parameters, there were significantly more events in the patients with moderate or greater AI compared to those with trace/mild. (1.11 vs. 0.56 events/person, p=0.02) (Figure 1B). Novel parameters better predicted the need for aortic valve intervention, urgent transplantation or death than traditional methods (p=0.049) (Figure 1C-D). Conclusions: In patients with CF-LVADs, traditional parameters tend to underestimate AI severity and future cardiac events. Novel AI TTE parameters are better able to discriminate AI severity and predict clinically meaningful outcomes.

Proximal thoracic aorta dimensions after continuous-flow left ventricular assist device implantation: Longitudinal changes and relation to aortic valve insufficiency

In this study we examined the impact of continuous-flow left ventricular assist device (CF-LVAD) support on proximal thoracic aorta dimensions. Aortic root and ascending aorta diameter were measured from serial echocardiograms before and after CF-LVAD implantation in patients with ≥6 months of support, and correlated with the development of >mild aortic valve insufficiency (AI). Of 162 patients included, mean age was 58 ± 11 years and 128 (79%) were male. Seventy-nine (63%) were destination therapy patients. Mean aortic root and ascending aorta diameters at baseline, 1 month, 6 months, 12 months and long-term follow-up (mean 2.0 ± 1.4 years) were 3.5 ± 0.4, 3.5 ± 0.3, 3.9 ± 0.3, 3.9 ± 0.2 and 4.0 ± 0.3, and 3.3 ± 0.2, 3.3 ± 0.3, 3.6 ± 0.2, 3.6 ± 0.3 and 3.6 ± 0.3 cm, respectively. Only change in aortic root diameter from 1-month to 6-month follow-up reached statistical significance (p = 0.03). Nine (6%) patients had accelerated proximal thoracic aorta expansion (>0.5 cm/year), occurring predominantly in the first 6 months after implantation. These patients were older and more likely to have hypertension and baseline proximal thoracic aorta dilation. Forty-five (28%) patients developed >mild AI at long-term follow-up, including 7 of 9 (78%) of those with accelerated proximal thoracic aorta expansion. All 7 had aortic valves that remained closed throughout the cardiac cycle, and this, along with duration of CF-LVAD support and increase in aortic root diameter, were significantly associated with developing >mild AI. CF-LVAD patients have small increases in proximal thoracic aorta dimensions that predominantly occur within the first 6 months after implantation and then stabilize. Increasing aortic root diameter was associated with AI development.

Coagulopathy in Mechanical Circulatory Support: A Fine Balance.

Therapeutic intervention with mechanical circulatory support has revolutionized the medical care of individuals living with advanced heart failure. Left ventricular assist devices (LVADs) have enabled patients to live longer while providing improved quality of life and functional status. However, intervention is not without risk. Over the last decade, clinicians have identified common mechanical assist device-associated complications. This appears to be multi-factorial with relation to patient variables, inherent device technology, and nuances of concurrent medical management. This review will discuss the impact of adverse hematologic complications: bleeding, pump thrombosis, and hemolysis in continuous flow LVAD patients. These obstacles continue to pose a clinical challenge with regard to both diagnosis and optimal management. Heightened awareness and understanding of heterogeneous clinical presentations is essential for preventive management and early detection with intervention.

Changes in Aortic Wall Structure, Composition, and Stiffness With Continuous-Flow Left Ventricular Assist Devices: A Pilot Study.

The effects of nonpulsatile flow on the aorta are unknown. Our aim was to examine the structure of the aorta from patients with continuous-flow left ventricular assist devices (LVADs) and directly measure aortic wall composition and stiffness. Age-matched aortic wall samples were collected from consecutive patients with heart failure (HF) at the time of transplantation and compared with nonfailing donor hearts. An unbiased stereological approach was used to quantify aortic morphometry and composition, and biomechanical testing was performed to determine the stress-strain relationship of the vessel. Data were obtained from 4 patients without a left ventricular assist device (HF group: mean age, 58.3±8.0 years), 7 patients with a continuous-flow LVAD (HF+LVAD group: mean, 57.7±5.6 years), and 3 nonfailing donors (mean, 53.3±12.9 years). Compared with HF, the aortic walls from HF+LVAD had an increase in wall thickness, collagen, and smooth muscle content accompanied by a reduction in elastin and mucinous ground-substance content. Stress-strain curves from the aortas revealed increased vessel stiffness in HF+LVAD compared with HF and nonfailing. The physiological modulus of the aorta progressively stiffened from 74.3±5.5 kPa in the nonfailing to 134.4±35.0 kPa in the HF to 201.7±36.4kPa in the HF+LVAD groups (P<0.001). Among continuous-flow LVAD patients without aortic valve opening, there are changes in the structure and composition of the aorta as well as an increase in aortic wall stiffness compared with age-matched HF patients and nonfailing donors. Further studies examining the role of nonpulsatile blood flow on aortic function and the potential resultant systemic sequelae are needed.

Vascular Reactivity Analysis in Patients with Continuous Flow Left Ventricular Assist Devices (CF-LVADs) - the Role of Endothelial Function in Continuous Flow Physiology

Endothelial dysfunction associated with heart failure should improve after a CF-LVAD placement due to correction of the heart failure environment. Yet, a loss of pulsatility could counteract such improvement as endothelial cells need a pulse pressure for normal function. Mixed results of endothelial dysfunction in CF-LVAD when compared to pulsatile VAD have been reported utilizing both brachial reactivity and EndoPAT® machines. Both these tests rely on physical pulse volume and might be impacted by the mere loss of pulsatility. Hence, we set out to analyze endothelial function utilizing thermal digital monitoring (VENDYS) in patients with CF-LVADs. We recruited stable patients during their routine visits and performed the VENDYS test in a soothing environment. Aortic valve opening was determined with a portable echo (GE V-scan) and graded as per previously described classification. Rest of the data was collected from the patient charts. Patients were classified into three groups based on parameters of vascular reactivity index (VRI) described in normal population: poor (<1) intermediate (1 - 2) and good VRI (2 - 3) with higher VRI correlated with better endothelial function, hence better outcomes. Pearsons correlation and T-test were performed, P-values < 0.05 were considered significant. 40 patients had Heartmate II and 2 had Heartware devices. Table 1 describes the characteristics of the 3 cohorts of endothelial function. Overall 81% had aortic valve opening consistently at the time of endothelial function assessment. Only 19% had a poor VRI, while majority had an intermediate VRI. Older patients had worse endothelial function while rest of the baseline characteristics including aortic valve opening and flow were not different between the groups. Correlation between VRI and VAD flow (r= -0.2766 P value= 0.08) and high Doppler blood pressure (r= -0.2656 P value=0.09) showed no significance. However, 50% of the patients with a poor VRI had adverse events while only 23% of those with good endothelial function did (Table 1). The 2 patients with poor VRI who had a GI bleed had 5 episodes while the 3 patients with good VRI had 4 episodes. In a cohort of CF-LVAD patients where the majority had their aortic valve open, endothelial function, as reflected by DTM was poor in only a few. It is not clear if endothelial dysfunction contributes to any of adverse events for CF-LVAD patients but there seem to be a higher recurrence of GI bleeding in patients who had a poor endothelial function.Table 1Total<11 to 22 to 3p valueN42 (100%)8 (19%)21 (50%)13 (31%)VENDYS score1.71±0.780.45±0.351.69±0.282.5±0.35Age57±12.860.3±7.559.6±10.150.2±16.70.073Male34 (81%)5 (62.5%)19 (90%)10 (77%)0.2082Caucasian17(40%)2 (25%)9 (43%)6 (46%)0.6009DT31 (74%)6 (75%)17 (81%)8 (61%)0.45AV opened34 (81%)7 (87%)17 (81%)10 (77%)0.835Days under support585±567244±276672±586497±5820.17BUN275.47±282.425.25±16.4724.8±7.2320.6±7.540.41Hgb11.06±2.229.77±1.4711.56±2.4511.04±2.010.15Flow5.49±1.346.4±1.475.21±1.515.37±0.510.098Patients with events17(100%)4 (23%)10 (59%)3 (18%)0.3GIB10 (58%)2530.99Infections4 (23%)1300.36Arrhythmia1 (6%)0100.59ADHF3 (18%)0300.19Death3 (14%)1200.46VENDYS score: Endothelial function based thermal vascular reactivity. DT: Destination Therapy. AV: Aortic valve. GIB: Gastrointestinal bleeding. ADHF: Acute decompensated heart failure. Open table in a new tab

Heart Transplant Donor Characteristics Associated with Worse Outcomes Differ Between Patients who are Bridged Continuous Flow LVAD and Non-bridged Patients: an Analysis of the UNOS Registry

Heart Transplant Donor Characteristics Associated with Worse Outcomes Differ Between Patients who are Bridged Continuous Flow LVAD and Non-bridged Patients: an Analysis of the UNOS Registry

Relation between pressure and volume unloading during ramp testing in patients supported with a continuous-flow left ventricular assist device.

Pulmonary capillary wedge pressure (PCWP) is the key to describing left ventricular (LV) unloading; however, the relation between pressure and the echocardiography-derived surrogate of LV volume (LV end-diastolic diameter [LVEDD]) as a function of pump speed (revolutions per minute [RPM]) in continuous-flow LV assist device (CF-LVAD) patients is unknown. In this study, the pressure-volume relation as a function of RPM during ramp testing was investigated by simultaneously measuring PCWP by Swan-Ganz catheter and LVEDD by echocardiography. The ramp protocol started at usual pump setting (ramp-base) and then went from 8,000 RPM (ramp-low) increasing by 400 RPM/5 minutes until reaching 12,000 RPM or suction/arrhythmic event (ramp-high). The study was finalized by a 25 Watt exercise test at two ramp steps. Ten patients with ramp-base of 9,300 ± 241 RPM (at which 3 of 10 had aortic valve opening) were examined. At ramp-low, ramp-base, and ramp-high, PCWP was 20 ± 4, 14 ± 4, and 7 ± 3 mm Hg (p < 0.001 for all comparisons) and LVEDD 6.6 ± 1.0, 6.7 ± 0.9, and 5.5 ± 1.7 cm (p < 0.05 for all comparisons but ramp-low versus ramp-base). Correlation between PCWP and LVEDD slopes; R = 0.53 (p = 0.02). In conclusion, PCWP as a function of RPM is weakly correlated with changes in LVEDD. Thus, LVEDD is not an accurate measure of unloading in CF-LVAD patients.

A new Bayesian network-based risk stratification model for prediction of short-term and long-term LVAD mortality.

Existing risk assessment tools for patient selection for left ventricular assist devices (LVADs) such as the Destination Therapy Risk Score and HeartMate II Risk Score (HMRS) have limited predictive ability. This study aims to overcome the limitations of traditional statistical methods by performing the first application of Bayesian analysis to the comprehensive Interagency Registry for Mechanically Assisted Circulatory Support dataset and comparing it to HMRS. We retrospectively analyzed 8,050 continuous flow LVAD patients and 226 preimplant variables. We then derived Bayesian models for mortality at each of five time end-points postimplant (30 days, 90 days, 6 month, 1 year, and 2 years), achieving accuracies of 95%, 90%, 90%, 83%, and 78%, Kappa values of 0.43, 0.37, 0.37, 0.45, and 0.43, and area under the receiver operator characteristic (ROC) of 91%, 82%, 82%, 80%, and 81%, respectively. This was in comparison to the HMRS with an ROC of 57% and 60% at 90 days and 1 year, respectively. Preimplant interventions, such as dialysis, ECMO, and ventilators were major contributing risk markers. Bayesian models have the ability to reliably represent the complex causal relations of multiple variables on clinical outcomes. Their potential to develop a reliable risk stratification tool for use in clinical decision making on LVAD patients encourages further investigation.

Inhaled Milrinone After Left Ventricular Assist Device Implantation

BackgroundProven strategies to reduce right ventricular (RV) dysfunction after continuous-flow left ventricular assist device (CF-LVAD) implantation are lacking. We sought to evaluate the tolerability, feasibility, efficacy, and pharmacokinetics of inhaled milrinone (iMil) delivery after CF-LVAD implantation. Methods and ResultsWe prospectively evaluated fixed-dose nebulized iMil delivered into a ventilator circuit for 24 hours in 10 postoperative CF-LVAD (Heartmate-II) patients. Tolerability (arrhythmias, hypotension, and hypersensitivity reaction), efficacy (hemodynamics), pharmacokinetics (plasma milrinone levels), and cost data were collected.Mean age was 56 ± 9 years, 90% were male, and mean INTERMACS profile was 2.5 ± 0.8. No new atrial arrhythmia events occurred, although 3 (30%) ventricular tachycardia (1 nonsustained, 2 sustained) events occurred. Sustained hypotension, drug hypersensitivity, death, or need for right ventricular assist device were not observed. Invasive mean pulmonary arterial pressure from baseline to during iMil therapy was improved (P = .017). Mean plasma milrinone levels (ng/mL) at baseline, and 1, 4, 8, 12, and 24 hours were 74.2 ± 35.4, 111.3 ± 70.9, 135.9 ± 41.5, 205.0 ± 86.7, 176.8 ± 61.3 187.6 ± 105.5, respectively. Reduced institutional cost was observed when iMil was compared with nitric oxide therapy over 24 hours ($165.29 vs $1,944.00, respectively). ConclusionsiMil delivery after CF-LVAD implantation was well tolerated, feasible, and demonstrated favorable hemodynamic, pharmacokinetic, and cost profiles. iMil therapy warrants further study in larger clinical trials.

(403) - Impact and Development of Aortic Insufficiency in CF-LVAD Recipients at 5 Years

Aortic insufficiency (AI) is a significant long-term complication of continuous-flow left ventricular assist device (CF-LVAD) implantation. We sought to evaluate long-term AI development in CF-LVAD patients.

(516) - Modulation of LV Loading and Arterial Pulsatility Affects PET/CT Coronary Flow Reserve in Continuous Flow LVAD Patients

Coronary flow reserve (CFR) is associated with poor outcomes in heart failure (HF). The effect of changes in LV loading and arterial pulsatility (via modulation of pump speed) on CFR in continuous flow LVAD (CF-LVAD) has not been previously studied.

(185) - Health-Related Quality of Life Improves Dramatically From Pre-Implant to Post Implant (6 months) for Continuous Flow LVAD Patients in INTERMACS

s S75 DT and BTT. Mental scores were statistically improved for BTT patients at 3 and 6 months; DT patients showed numeric improvements but the differences did not achieve significance at any time point. Conclusion: CF-LVAD therapy results in significant improvement of QOL as assessed by serial SF-36. Compared with pre-implant, the physical improvements are sustained and statistically significant to 12 months in DT and BTT populations.

Preclinical Models for Translational Investigations of Left Ventricular Assist Device-Associated von Willebrand Factor Degradation.

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.

Anti–Factor Xa and Activated Partial Thromboplastin Time Measurements for Heparin Monitoring in Mechanical Circulatory Support

ObjectivesThis study investigated the relationship between anti–factor Xa (anti-FXa) and activated partial thromboplastin time (aPTT) for monitoring intravenous unfractionated heparin (IV-UFH) in patients with continuous-flow left ventricular assist devices (CF-LVADs). BackgroundCF-LVADs have become mainstream therapy for patients with advanced heart failure. Thromboembolic events, device thrombosis, and bleeding continue to be a challenge with this technology. Adequate anticoagulation is required to prevent these adverse events. MethodsA prospective study of consecutive patients implanted with a CF-LVAD was conducted. Paired samples were considered concordant if aPTT values fell into expected ranges for subtherapeutic, therapeutic, and supratherapeutic anti-FXa levels. Heparin dosing was on the basis of anti-Xa levels. ResultsA total of 340 paired values from 38 patients were evaluated. Anti-FXa and aPTT were discordant in 253 samples (74.4%), with a high degree of variability in aPTT for any given anti-FXa level (r2 = 0.57). Results were discordant in 104 samples (63.8%) from patients undergoing bridging therapy with warfarin and in 149 samples (84.2%) from patients with device obstruction and/or hemolysis (p < 0.001). The most common pattern of discordance was a supratherapeutic aPTT value despite a therapeutic anti-FXa level (49.1% for bridging vs. 75.8% for device obstruction and/or hemolysis; p < 0.001). ConclusionsLevels of aPTT were disproportionately prolonged relative to the corresponding anti-FXa levels in CF-LVAD patients, particularly those with device obstruction. Hemolysis and warfarin administration may falsely elevate aPTT, resulting in overestimation of heparin concentration and under-anticoagulation. Use of aPTT and anti-FXa to guide heparin therapy may lead to different estimates of heparin concentration in the same patient.