Human Factors Evaluation of HeartMate 3 Left Ventricular Assist Device Peripherals: An Eye Tracking Supported Simulation Study.

BACKGROUND: Despite recent design improvements, human factors issues continue to challenge left ventricular assist device (LVAD) therapy. The aim of this study was to evaluate user experience of former non-HeartMate 3 (HM3) LVAD patients post heart transplantation (HTX) and laypersons (LP) with HM3 LVAD peripherals in simulated everyday and emergency scenarios. METHODS: This single center cohort study included untrained HTX and LP. Seven scenarios, including battery exchanges (without alarm, advisory alarm, dim light, consolidated bag), change of power supply, driveline dis-/reconnection and controller exchange were simulated. Subjects' gaze behavior was recorded using eye tracking technology. Success rate, pump-off-time, duration to success (DTS), percental fixation duration per areas of interest and post-scenario-survey results were defined as outcome measures. RESULTS: Thirty subjects completed 210 scenarios, initially solving 82.4% (HTX vs. LP, p = 1.00). Changing power supply revealed highest complexity (DTS = 251 ± 93s, p = 0.76): 26.7% succeeded at first attempt (p = 0.68), 56.7% at second attempt, with significantly more LP failing (p = 0.04), resulting in 10 hazards from driveline disconnections (pump-off-time 2-118s, p = 0.25). Comparison on initial success showed differences in fixation durations for seven areas of interest (p < 0.037). Decreasing DTS during battery exchanges (p < 0.001) indicate high learnability. Exchanging batteries within the bag took longer (median DTS = 75.0 (IQR = 45.0)s, p = 0.09), especially in elderly subjects (r = 0.61, p < 0.001). Subjects with less initial success were more afraid of making mistakes (p = 0.048). CONCLUSION: This eye tracking based human factors study provided insights into user experiences in handling HM3 peripherals. It highlights unintuitive and hazardous characteristics, providing guidance for future user-centered design of LVAD wearables.

Inflow cannula position as risk factor for stroke in patients with HeartMate 3 left ventricular assist devices.

BACKGROUND: A relation between the left ventricular assist device inflow cannula (IC) malposition and pump thrombus has been reported. This study aimed to investigate if the pump position, derived from chest X-rays in HeartMate 3 (HM3) patients, correlates with neurological dysfunction (ND), ischemic stroke (IS), hemorrhagic stroke (HS) and survival. METHODS: This analysis was performed on routinely acquired X-rays of 42 patients implanted with a HM3 between 2014 and 2017. Device position was quantified in patients with and without ND from frontal and lateral X-rays characterizing the IC and pump in relation to spine, diaphragm or horizontal line. The primary end-point was freedom from stroke and survival one-year after HM3 implantation stratified by pump position. RESULTS: The analysis of X-rays, 33.5 (41.0) days postoperative, revealed a significant smaller IC angle of HM3 patients with ND versus no ND (0.1° ± 14.0° vs. 12.9° ± 10.1°, p = 0.005). Additionally, the IC angle in the frontal view, IS: 4.1 (20.9)° versus no IS: 13.8 (7.5)°, p = 0.004 was significantly smaller for HM3 patients with IS. Using receiver operating characteristics derived cut-off, IC angle <10° provided 75% sensitivity and 100% specificity (C-statistic = 0.85) for predicting IS. Stratified by IC angle, freedom from IS at 12 months was 100% (>10°) and 60% (<10°) respectively (p = 0.002). No significant differences were found in any end-point between patients with and without HS. One-year survival was significantly higher in patients with IC angle >10° versus <10° (100% vs. 71.8%, p = 0.012). CONCLUSIONS: IC malposition derived from standard chest X-rays serves as a risk factor for ND, IS and worse survival in HM3 patients.

Left ventricular assist device driveline infections in three contemporary devices.

Driveline infections (DLI) are common adverse events in left ventricular assist devices (LVADs), leading to severe complications and readmissions. The study aims to characterize risk factors for DLI readmission 2 years postimplant. This single-center study included 183 LVAD patients (43 HeartMate II [HMII], 29 HeartMate 3 [HM3], 111 HVAD) following hospital discharge between 2013 and 2017. Demographics, clinical parameters, and outcomes were retrospectively analyzed and 12.6% of patients were readmitted for DLI, 14.8% experienced DLI but were treated in the outpatient setting, and 72.7% had no DLI. Mean C-reactive protein (CRP), leukocytes and fibrinogen were higher in patients with DLI readmission (P < .02) than in outpatient DLI and patients without DLI, as early as 60 days before readmission. Freedom from DLI readmission was comparable for HMII and HVAD (98% vs. 87%; HR, 4.52; 95% CI, 0.58-35.02; P = .15) but significantly lower for HM3 (72%; HR, 10.82; 95% CI, 1.26-92.68; P = .03). DLI (HR, 1.001; 95% CI, 0.999-1.002; P = .16) or device type had no effect on mortality. DLI readmission remains a serious problem following LVAD implantation, where CRP, leukocytes, and fibrinogen might serve as risk factors already 60 days before. HM3 patients had a higher risk for DLI readmissions compared to HVAD or HMII, possibly because of device-specific driveline differences.

The influence of left ventricular assist device inflow cannula position on thrombosis risk.

The use of left ventricular assist devices (LVADs) as a treatment method for heart failure patients has been steadily increasing; however, pathological studies showed presence of thrombi around the HeartWare ventricular assist device inflow cannula (IC) in more than 95% of patients after device explantation. Flow fields around the IC might trigger thrombus formation and require further investigation. In this study flow dynamics parameters were evaluated for different patient geometries using computational fluid dynamics (CFD) simulations. Left ventricular (LV) models of two LVAD patients were obtained from CT scans. The LV volumes of Patient 1 (P1) and Patient 2 (P2) were 264 and 114 cm3 with an IC angle of 20° and 9° from the mitral-IC tip axis at the coronal plane. The IC insertion site at the apex was central for P1, whereas it was lateral for P2. Transient CFD simulations were performed over 9 cardiac cycles. The wedge area was defined from the cannula tip to the wall of the LV apex. Mean velocity magnitude and blood stagnation region (volume with mean velocity <5 mm/s) as well as the wall shear stress (WSS) at the IC surface were calculated. Cardiac support resulted in a flow mainly crossing the ventricle from the mitral valve to the LVAD cannula for P2, while the main inflow jet deviated toward the septal wall in P1. Lower WSS at the IC surface and consequently larger stagnation volumes were observed for P2 (P1: 0.17, P2: 0.77 cm3 ). Flow fields around an LVAD cannula can be influenced by many parameters such as LV size, IC angle, and implantation site. Careful consideration of influencing parameters is essential to get reliable evaluations of the apical flow field and its connection to apical thrombus formation. Higher blood washout and lower stagnation were observed for a central implantation of the IC at the apex.

LVAD speed increase during exercise, which patients would benefit the most? A simulation study.

Patients supported with a left ventricular assist device (LVAD) have impaired cardiovascular adaptations during exercise, resulting in reduced total cardiac output and exercise intolerance. The aim of this study is to report associations among these impaired cardiovascular parameters and exercise hemodynamics, and to identify in which conditions an LVAD speed increase can provide substantial benefits to exercise. A cardiorespiratory simulator was used to reproduce the average hemodynamics of LVAD patients at exercise. Then, a sensitivity study was conducted where cardiovascular parameters were changed individually ±20% of their baseline value at exercise (heart rate, left/right ventricular contractility, total peripheral resistance, and valve pathologies). Simulations were performed at a baseline LVAD speed of 2700 rpm and repeated at 3500 rpm to evaluate the benefits of a higher LVAD support on hemodynamics. Total cardiac output (TCO) was mostly impaired by a poor left ventricular contractility or vasodilation at exercise (-0.6 L/min), followed by a poor chronotropic response (-0.3 L/min) and by a poor right ventricular contractility (-0.2 L/min). LVAD speed increase better unloads the left ventricle and improves total cardiac output in all the simulated conditions. The most substantial benefits from LVAD speed increase were observed in case of poor left ventricular contractility (TCO + 1.6 L/min) and vascular dysfunction (TCO + 1.4 L/min) followed by lower heart rate (TCO + 1.3 L/min) and impaired right ventricular contractility (TCO + 1.1 L/min). Despite the presence of the LVAD, exercise hemodynamic is strongly depending on the ability of the cardiovascular system to adapt to exercise. A poor left ventricular inotropic response and a poor vascular function can strongly impair cardiac output at exercise. In these conditions, LVAD speed increase can be an effective strategy to augment total cardiac output and unload the left ventricle. These results evidence the need to design a physiological LVAD speed controller, tailored on specific patient's needs.

Continuous LVAD monitoring reveals high suction rates in clinically stable outpatients.

Suction of the left ventricle can lead to potentially life-threatening events in left ventricular assist device (LVAD) patients. With the resolution of currently available clinical LVAD monitoring healthcare professionals are unable to evaluate patients' suction occurrences in detail. This study investigates occurrences and durations of suction events and their associations with tachycardia in stable outpatients. Continuous high-resolution LVAD data from HVAD patients were analyzed in the early outpatient period for 15 days. A validated suction detection from LVAD signals was used. Suction events were evaluated as suction rates, bursts of consecutive suction beats, and clusters of suction beats. The occurrence of tachycardia was analyzed before, during, and after suction clusters. Furthermore, blood work, implant strategy, LVAD speed setting, inflow cannula position, left ventricular diameters, and adverse events were evaluated in these patients. LVAD data of 10 patients was analyzed starting at 78 ± 22 postoperative days. Individuals' highest suction rates per hour resulted in a median of 11% (range 3%-61%). Bursts categorized as consecutive suction beats with n = 2, n = 3-5, n = 6-15, and n > 15 beats were homogenously distributed with 10.3 ± 0.8% among all suction beats. Larger suction bursts were followed by shorter suction-free periods. Tachycardia during suction occurred in 12% of all suction clusters. Significant differences in clinical parameters between individuals with high and low suction rates were only observed in left ventricular end-diastolic and end-systolic diameters (P < .02). Continuous high-resolution LVAD monitoring sheds light on outpatient suction occurrences. Interindividual and intraindividual characteristics of longitudinal suction rates were observed. Longer suction clusters have higher probabilities of tachycardia within the cluster and more severe types of suction waveforms. This work shows the necessity of improved LVAD monitoring and the implementation of an LVAD speed control to reduce suction rates and their concomitant burden on the cardiovascular system.

LVAD Pump Flow Does Not Adequately Increase With Exercise.

Left ventricular assist devices (LVADs) restore cardiovascular circulatory demand at rest with a spontaneous increase in pump flow to exercise. The relevant contribution of cardiac output provided by the LVAD and ejected through the aortic valve for exercises of different intensities has been barely investigated in patients. The hypothesis of this study was that different responses in continuous recorded pump parameters occur for maximal and submaximal intensity exercises and that the pump flow change has an impact on the oxygen uptake at peak exercise (pVO2 ). Cardiac and pump parameters such as LVAD flow rate (QLVAD ), heart rate (HR), and aortic valve (AV) opening were analyzed from continuously recorded LVAD data during physical exercises of maximal (bicycle ergometer test) and submaximal intensities (6-min walk test and regular trainings). During all exercise sessions, the LVAD speed was kept constant. Cardiac and pump parameter responses of 16 patients for maximal and submaximal intensity exercises were similar for QLVAD : +0.89 ± 0.52 versus +0.59 ± 0.38 L/min (P = 0.07) and different for HR: +20.4 ± 15.4 versus +7.7 ± 5.8 bpm (P < 0.0001) and AV-opening with 71% versus 23% of patients (P < 0.0001). Multi-regression analysis with pVO2 (R2  = 0.77) showed relation to workload normalized by bodyweight (P = 0.0002), HR response (P = 0.001), AV-opening (P = 0.02), and age (P = 0.06) whereas the change in QLVAD was irrelevant. Constant speed LVADs provide inadequate support for maximum intensity exercises. AV-opening and improvements in HR show an important role for higher exercise capacities and reflect exercise intensities. Changes in pump flow do not impact pVO2 and are independent of AV-opening and response in HR. An LVAD speed control may lead to adequate left ventricular support during strenuous physical activities.

The 2018 ISHLT/APM/AST/ICCAC/STSW Recommendations for the Psychosocial Evaluation of Adult Cardiothoracic Transplant Candidates and Candidates for Long-term Mechanical Circulatory Support.

The psychosocial evaluation is well-recognized as an important component of the multifaceted assessment process to determine candidacy for heart transplantation, lung transplantation, and long-term mechanical circulatory support (MCS). However, there is no consensus-based set of recommendations for either the full range of psychosocial domains to be assessed during the evaluation, or the set of processes and procedures to be used to conduct the evaluation, report its findings, and monitor patients' receipt of and response to interventions for any problems identified. This document provides recommendations on both evaluation content and process. It represents a collaborative effort of the International Society for Heart and Lung Transplantation (ISHLT) and the Academy of Psychosomatic Medicine, American Society of Transplantation, International Consortium of Circulatory Assist Clinicians, and Society for Transplant Social Workers. The Nursing, Health Science and Allied Health Council of the ISHLT organized a Writing Committee composed of international experts representing the ISHLT and the collaborating societies. This Committee synthesized expert opinion and conducted a comprehensive literature review to support the psychosocial evaluation content and process recommendations that were developed. The recommendations are intended to dovetail with current ISHLT guidelines and consensus statements for the selection of candidates for cardiothoracic transplantation and MCS implantation. Moreover, the recommendations are designed to promote consistency across programs in the performance of the psychosocial evaluation by proposing a core set of content domains and processes that can be expanded as needed to meet programs' unique needs and goals.

A Standardized Telephone Intervention Algorithm Improves the Survival of Ventricular Assist Device Outpatients.

Ventricular assist devices (VADs) are an established therapeutic option for patients with chronic heart failure. Continuous monitoring of VAD parameters and their adherence to guidelines are crucial to detect problems in an early stage to optimize outcomes. A telephone intervention algorithm for VAD outpatients was developed, clinically implemented and evaluated. During the phone calls, a structured inquiry of pump parameters, alarms, blood pressure, INR, body weight and temperature, exit-site status and heart failure symptoms was performed and electronically categorized by an algorithm into 5 levels of severity. VAD outpatient outcomes without (n = 71) and with bi-weekly telephone interviews in their usual care (n = 25) were conducted using proportional hazard Cox regression, with risk adjustment based on a propensity score model computed from demographics and risk factors. From February 2015 through October 2017, 25 patients (n = 3 HeartMate II, n = 4 HeartMate 3 and n = 18 HeartWare HVAD) underwent 637 telephone interventions. In 57.5% of the calls no problems were identified, 3.9% were recalled on the next day because of alarms. In 26.5% (n = 169), the VAD Coordinator had to refer to the physician due to elevated blood pressure (n = 125, >85 mm Hg), INR < 2.0 or > 4.0 (n = 24) or edema (n = 10), 11.9% of the calls led to a follow-up because of equipment or exit-site problems. Propensity-adjusted 2-year survival (89% vs. 57%, P = 0.027) was significantly higher for the telephone intervention group. Continuous, standardized communication with VAD outpatients is important for early detection of upcoming problems and leads to significantly improved survival.

Repair of left ventricular assist device driveline damage directly at the transcutaneous exit site.

With increasing support duration of cardiac assist devices, transcutaneous drivelines remain a weak point of the therapy. First, they can be an entry point for infections, and second, cable lesions and even electrical failures due to material fatigue and eventual carelessness can occur. We report a case of a damaged outer sheath of a ventricular assist device driveline cable directly at the exit site, where the standard repair procedure with self-fusing tape may lead to biocompatibility problems and irritation of the entrance through the skin. Therefore, a new procedure was developed using a special sleeve expander tool and a highly expandable latex tubing to stabilize the defect in a flexible and biocompatible manner. A patient experienced a fracture of the outer sheath of a HeartWare HVAD driveline directly at the skin entrance (approximately 15 mm long, 5 mm distal from the skin). The metal strands and the electrical functionality were yet not affected, therefore, a pump exchange was not indicated. After considering several conventional solutions for repair as not applicable, a new approach was developed: a sleeve expander tool was applied, which allowed radial stretching of the latex tubing. After preparations of the tool and the cable site, the pump was briefly disconnected, the tubing was moved over the connector and was released at the site of fracture. The problem could be solved by keeping the cable's flexibility and without additional risks to the skin. Within a still ongoing (5-month) follow-up, the skin entrance returned to perfect condition and no further intervention was necessary. In conclusion, this method allows a quick stabilization and repair of damaged driveline isolations even near the exit site, resulting in a biocompatible surface and consistent flexibility of the cable.

Usability of ventricular assist devices in daily experience: a multicenter study.

In daily life, the safe, intuitive use of ventricular assist devices (VADs) and especially their peripheral components is not only a question of life quality, but also sometimes crucial for survival. To investigate the advantages and disadvantages of different systems and to get patient feedback on preferred features, a multicenter study was initiated. Based on previous single-center studies, a questionnaire was developed to ascertain patients' experiences, difficulties with, and desires concerning use of the system. This questionnaire was provided both to ongoing patients and to new VAD patients after a minimum hospital discharge time of 6 weeks, at a regular checkup. Additionally, the patients completed a standardized questionnaire on life quality (Kansas City Cardiomyopathy Questionnaire). The centers that contributed to this study were Bad Oeynhausen, Berlin, Hannover, and Vienna. Three hundred fifty-two completed questionnaires on eight different pump types were obtained. An important result is that 42% of those questioned dropped their controller bag at least once. Depending on the device, between 2 and 55% disconnected it unintentionally. Confidence in safe use of the system decreased significantly with age, from 80% at age 20-30 years to 33% at 70-80 years. In devices with an LCD display, 94% considered the readability sufficient. Ninety-four percent considered the training adequate. Between 22 and 88% of the patients called the emergency telephone hotline, depending on the device, and 23-46% depending on the center. This first multicenter study on VAD usability reveals considerable differences among devices and centers. The comparative assessment aims to help optimize device design, patient management, and training.

Semi-invasive measurement of cardiac output based on pulse contour: a review and analysis.

PURPOSE: The aim of this review was to provide a meta-analysis of all five of the most popular systems for arterial pulse contour analysis compared with pulmonary artery thermodilution, the established reference method for measuring cardiac output (CO). The five investigated systems are FloTrac/Vigileo(®), PiCCO(®), LiDCO/PulseCO(®), PRAM/MostCare(®), and Modelflow. SOURCE: In a comprehensive literature search through MEDLINE(®), Web of Knowledge (v.5.11), and Google Scholar, we identified prospective studies and reviews that compared the pulse contour approach with the reference method (n = 316). Data extracted from the 93 selected studies included range and mean cardiac output, bias, percentage error, software versions, and study population. We performed a pooled weighted analysis of their precision in determining CO in various patient groups and clinical settings. PRINCIPAL FINDINGS: Results of the majority of studies indicate that the five investigated systems show acceptable accuracy during hemodynamically stable conditions. Forty-three studies provided adequate data for a pooled weighted analysis and resulted in a mean (SD) total pooled bias of -0.28 (1.25) L·min(-1), percentage error of 40%, and a correlation coefficient of r = 0.71. In hemodynamically unstable patients (n = 8), we found a higher percentage error (45%) and bias of -0.54 (1.64) L·min(-1). CONCLUSION: During hemodynamic instability, CO measurement based on continuous arterial pulse contour analysis shows only limited agreement with intermittent bolus thermodilution. The calibrated systems seem to deliver more accurate measurements than the auto-calibrated or the non-calibrated systems. For reliable use of these semi-invasive systems, especially for critical therapeutic decisions during hemodynamic disorders, both a strategy for hemodynamic optimization and further technological improvements are necessary.

Omission of Antiplatelet Therapy in Patients With HeartMate 3 Left Ventricular Assist Devices: A Systematic Review and Meta-Analysis.

The HeartMate 3 (HM3) left ventricular assist device has decreased thromboembolic events and minimized the risk of pump thrombosis. However, bleeding complications due to combined antithrombotic therapy with a vitamin K antagonist (VKA) and aspirin remain high. Only limited data on the safety of VKA monotherapy in HM3 patients are available. A systematic search on the main databases was performed. Observational data and randomized trials were eligible for this analysis. As primary endpoint, we analyzed hemocompatibility-related adverse events (HRAE). As secondary endpoints, we investigated the individual components of the primary endpoint. The analysis was carried out using the odds ratio (OR) as outcome measure. A random-effects model was fitted to the data. Five manuscripts fulfilled the inclusion criteria. These trials included 785 patients (381 on VKA monotherapy, 404 on VKA and aspirin). VKA monotherapy significantly reduced HRAE (OR: 0.11 [95% confidence interval {CI}: 0.02-0.59], p = 0.01, I2 = 87%). The reduction was driven by a decrease in bleeding complications (OR: 0.12 [95% CI: 0.02-0.62], p = 0.01, I2 = 86%) without increasing the rates of thromboembolic events (OR: 0.69 [95% CI: 0.26-1.81], p = 0.45, I = 0%). Vitamin K antagonist monotherapy is associated with a significant reduction of bleeding events without increasing the risk of thromboembolic complications in HM3 patients.

Mechanical Characterization of Anchoring Devices for the Prevention of Driveline Infection in Left Ventricular Assist Device Patients.

Driveline infection (DLI) is associated with increased mortality and morbidity in left ventricular assist device (LVAD) patients. Because trauma to the driveline exit-site (DLES) is a risk factor for DLI, adhesive anchoring devices are used to immobilize the DL. In this study, commonly used products (identified through literature review and contact with nine international VAD implantation centers) were mechanically characterized to evaluate their effectiveness in preventing DLES trauma. Eight devices were tested in an in vitro abdominal model of the DLES, where a tensile force (10 N) was applied to a HeartMate 3 DL, whereas the resulting force ( FTotal ) on the DLES was recorded using a three-axis load cell. Four devices (CathGrip: FTotal = 2.1 ± 0.4 N, Secutape: FTotal = 2.6 ± 0.3 N, Hollister: FTotal = 2.7 ± 0.5 N, Tubimed: FTotal = 2.9 ± 0.2 N) were significantly ( p < 0.05) better at preventing tensile forces at the DLES compared to the other four devices (Main-Lock: FTotal = 3.7 [0.7] N, Secutape sensitive: FTotal = 3.9 ± 0.4 N, Foley Anchor: FTotal = 4.3 ± 0.5 N, Grip-Lok: FTotal = 5.4 ± 0.8 N). Immobilization of the DL with each anchoring device resulted in lower tensile force on the DLES than without an anchor ( FTotal = 8.2 ± 0.3 N). In conclusion, the appropriate selection of anchoring devices plays a critical role in reducing the risk of DLI, whereas the CathGrip, Secutape, Hollister, or Tubimed were superior in preventing trauma to the DLES in this study.

Hemolysis Index Correlations with Plasma-Free Hemoglobin and Plasma Lactate Dehydrogenase in Critically Ill Patients under Extracorporeal Membrane Oxygenation or Mechanical Circulatory Support-A Single-Center Study.

Monitoring for thrombosis and hemolysis is crucial for patients under extracorporeal or mechanical circulatory support, but it can be costly. We investigated correlations between hemolysis index (HI) and plasma-free hemoglobin (PFH) levels on one hand, and between the HI and plasma lactate dehydrogenase (LDH) levels on the other, in critically ill patients with and without extracorporeal or mechanical circulatory support. Additionally, we calculated the cost reductions if monitoring through HI were to replace monitoring through PFH or plasma LDH. In a single-center study, HI was compared with PFH and plasma LDH levels in blood samples taken for routine purposes in critically ill patients with and without extracorporeal or mechanical circulatory support. A cost analysis, restricted to direct costs associated with each measurement, was made for an average 10-bed ICU. This study included 147 patients: 56 patients with extracorporeal or mechanical circulatory support (450 measurements) and 91 patients without extracorporeal or mechanical circulatory support (562 measurements). The HI correlated well with PFH levels (r = 0.96; p < 0.01) and poorly with plasma LDH levels (r = 0.07; p < 0.01) in patients with extracorporeal or mechanical circulatory support. Similarly, HI correlated well with PFH levels (r = 0.97; p < 0.01) and poorly with plasma LDH levels (r = -0.04; p = 0.39) in patients without extracorporeal or mechanical circulatory support. ROC analyses demonstrated a strong performance of HI, with the curve indicating excellent discrimination in the whole cohort (area under the ROC of 0.969) as well as in patients under ECMO or mechanical circulatory support (area under the ROC of 0.988). Although the negative predictive value of HI for predicting PFH levels > 10 mg/dL was high, its positive predictive value was found to be poor at various cutoffs. A simple cost analysis showed substantial cost reduction if HI were to replace PFH or plasma LDH for hemolysis monitoring. In conclusion, in this cohort of critically ill patients with and without extracorporeal or mechanical circulatory support, HI correlated well with PFH levels, but poorly with plasma LDH levels. Given the high correlation and substantial cost reductions, a strategy utilizing HI may be preferable for monitoring for hemolysis compared to monitoring strategies based on PFH or plasma LDH. The PPV of HI, however, is unacceptably low to be used as a diagnostic test.

HeartMate 3 Snoopy: Noninvasive cardiovascular diagnosis of patients with fully magnetically levitated blood pumps during echocardiographic speed ramp tests and Valsalva maneuvers.

PURPOSE: The HeartMate 3 (HM3) left ventricular assist device (LVAD) has demonstrated excellent clinical outcomes; however, pump speed optimization is challenging with the available HM3 monitoring. Therefore, this study reports on clinical HM3 parameters collected with a noninvasive HM3 monitoring system (HM3 Snoopy) during echocardiographic speed ramp tests and Valsalva maneuvers. METHODS: In this prospective, single-center study, the HM3 data communication between the controller and pump was recorded with a novel data acquisition system. Twelve pump parameters sampled every second (1 Hz) and clinical assessments (echocardiography, electrocardiogram (ECG), and blood pressure measurement) during speed ramp tests were analyzed using Pearson's correlation (r, median [IQR]). The cause for the occurrence of pulsatility index (PI)-events during ramp speed tests and valsalva maneuvers was investigated. RESULTS: In 24 patients (age: 58.9 ± 8.8 years, body mass index: 28.1 ± 5.1 kg/m2, female: 20.8%), 35 speed ramp tests were performed with speed changes in the range of ±1000 rpm from a baseline speed of 5443 ± 244 rpm. Eight HM3 pump parameters from estimated flow, motor current, and LVAD speed together with blood pressure showed positive collinearities (r = 0.9 [0.1]). Negative collinearities were observed for pump flow pulsatility, pulsatility index, rotor noise, and left ventricular diameters (r = -0.8 [0.1]), whereas rotor displacement and heartrate showed absence of collinearities (r = -0.1 [0.08]). CONCLUSIONS: In this study, the HM3 Snoopy was successfully used to acquire more parameters from the HM3 at a higher sampling rate. Analysis of HM3 per-second data provide additional clinical diagnostic information on heart-pump interactions and cause of PI-events.

An in vitro model to study suction events by a ventricular assist device: validation with clinical data.

Introduction: Ventricular assist devices (LVADs) are a valuable therapy for end-stage heart failure patients. However, some adverse events still persist, such as suction that can trigger thrombus formation and cardiac rhythm disorders. The aim of this study is to validate a suction module (SM) as a test bench for LVAD suction detection and speed control algorithms. Methods: The SM consists of a latex tube, mimicking the ventricular apex, connected to a LVAD. The SM was implemented into a hybrid in vitro-in silico cardiovascular simulator. Suction was induced simulating hypovolemia in a profile of a dilated cardiomyopathy and of a restrictive cardiomyopathy for pump speeds ranging between 2,500 and 3,200 rpm. Clinical data collected in 38 LVAD patients were used for the validation. Clinical and simulated LVAD flow waveforms were visually compared. For a more quantitative validation, a binary classifier was used to classify simulated suction and non-suction beats. The obtained classification was then compared to that generated by the simulator to evaluate the specificity and sensitivity of the simulator. Finally, a statistical analysis was run on specific suction features (e.g., minimum impeller speed pulsatility, minimum slope of the estimated flow, and timing of the maximum slope of the estimated flow). Results: The simulator could reproduce most of the pump waveforms observed in vivo. The simulator showed a sensitivity and specificity and of 90.0% and 97.5%, respectively. Simulated suction features were in the interquartile range of clinical ones. Conclusions: The SM can be used to investigate suction in different pathophysiological conditions and to support the development of LVAD physiological controllers.

Quality of Anticoagulation With Phenprocoumon and Warfarin in Left Ventricular Assist Device Patients: A Multicenter Study.

VISUAL ABSTRACT: of key results. INR, international normalized ratio; TTR, time in therapeutic range; PTR, percentage of tests in range; HRAE, hemocompatibility-related adverse event; FFUV, first follow-up visit; GIB, gastrointestinal bleeding; HR, hazard ratio.http://links.lww.com/ASAIO/A961.

Oxygen Consumption Predicts Long-Term Outcome of Patients with Left Ventricular Assist Devices.

Reduced oxygen consumption (VO2), either due to insufficient oxygen delivery (DO2), microcirculatory hypoperfusion and/or mitochondrial dysfunction, has an impact on the adverse short- and long-term survival of patients after cardiac surgery. However, it is still unclear whether VO2 remains an efficient predictive marker in a population in which cardiac output (CO) and consequently DO2 is determined by a left ventricular assist device (LVAD). We enrolled 93 consecutive patients who received an LVAD with a pulmonary artery catheter in place to monitor CO and venous oxygen saturation. VO2 and DO2 of in-hospital survivors and non-survivors were calculated over the first 4 days. Furthermore, we plotted receiver-operating curves (ROC) and performed a cox-regression analysis. VO2 predicted in-hospital, 1- and 6-year survival with the highest area under the curve of 0.77 (95%CI: 0.6-0.9; p = 0.0004). A cut-off value of 210 mL/min VO2 stratified patients regarding mortality with a sensitivity of 70% and a specificity of 81%. Reduced VO2 was an independent predictor for in-hospital, 1- and 6-year mortality with a hazard ratio of 5.1 (p = 0.006), 3.2 (p = 0.003) and 1.9 (p = 0.0021). In non-survivors, VO2 was significantly lower within the first 3 days (p = 0.010, p < 0.001, p < 0.001 and p = 0.015); DO2 was reduced on days 2 and 3 (p = 0.007 and p = 0.003). In LVAD patients, impaired VO2 impacts short- and long-term outcomes. Perioperative and intensive care medicine must, therefore, shift their focus from solely guaranteeing sufficient oxygen supply to restoring microcirculatory perfusion and mitochondrial functioning.

Exercise Performance and Quality of Life of Left Ventricular Assist Device Patients After Long-Term Outpatient Cardiac Rehabilitation.

PURPOSE: Exercise performance and quality of life (QoL) of left ventricular assist device (LVAD) patients improve after early cardiac rehabilitation (CR). The purpose of this study was to examine the efficacy of multiprofessional long term phase 3 outpatient CR, and whether cardiopulmonary exercise testing (CPX) and 6-min walk testing (6MWT) post-LVAD implantation predict hospital readmission. METHODS: This retrospective observational cohort study included 29 LVAD patients (58.6 ± 7.7 yr, female: 13.8%, body mass index: 29.4 ± 3.3 kg/m 2 ). Functional performance tests (CPX, 6MWT, sit-to-stand test), QoL, and psychological surveys (Kansas City Cardiomyopathy Questionnaire, hospital anxiety and depression scale, and Control Convictions about Disease and Health [KKG]) were performed at baseline and at the end of CR. RESULTS: The CR was initiated at a median (IQR) of 159 (130-260) d after LVAD implantation for a duration of 340 (180-363) d with 46.8 ± 23.2 trainings. The 6MWT (408.4 ± 113.3 vs 455.4 ± 115.5 m, P = .003) and sit-to-stand test (16.7 ± 6.9 vs 19.0 ± 5.3 repetitions, P = .033) improved, but relative peak oxygen uptake (V˙ o2peak : 9.4 [8.2-14.4] vs 9.3 [7.8-13.4] mL/min/kg, P = .57) did not change. Using receiver operating characteristic curve analysis, baseline V˙ o2peak values were associated with readmission 1-yr after CR onset (C-statistic = 0.88) with a cutoff value of V˙ o2peak < 9.15 mL/min/kg (100% sensitivity, 78% specificity, P < .001). The Kansas City Cardiomyopathy Questionnaire self-efficacy and knowledge (+6.3 points), QoL (+5.0 points), and social limitation (+7.1 points) demonstrated clinically important changes. In addition, the hospital anxiety and depression scale showed a significant reduction in anxiety (4.6 ± 3.2 vs 2.6 ± 2.4, P = .03). CONCLUSIONS: Long-term CR is safe and LVAD outpatients showed improvement of QoL, anxiety, and submaximal exercise performance. In addition, V˙ o2peak and 6MWT have prognostic value for readmission.