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.

A multicenter evaluation of external outflow graft obstruction with a fully magnetically levitated left ventricular assist device

BACKGROUND

The HeartMate 3 (HM 3; Abbott) left ventricular assist device (LVAD) has improved hemocompatibility-related adverse outcomes. In sporadic cases, external compression of the outflow graft causing obstruction (eOGO) can result from substance accumulation between the outflow graft and its bend relief. We sought to evaluate the prevalence, course, and clinical implications of eOGO in an international study.

METHODS

A multicenter retrospective analysis of HM 3 LVADs implanted between November 2014 and April 2021 (n = 2108) was conducted across 17 cardiac centers in 8 countries. We defined eOGO as obstruction >25% in the cross-sectional area in imaging (percutaneous angiography, computed tomography, or intravascular ultrasound). The prevalence and annual incidence were calculated. Serious adverse events and outcomes (death, transplantation, or device exchange) were analyzed for eOGO cases.

RESULTS

Of 2108 patients, 62 were diagnosed with eOGO at a median LVAD support duration of 953 (interquartile range, 600-1267) days. The prevalence of eOGO was 3.0% and the incidence at 1, 2, 3, 4, and 5 years of support was 0.6%, 2.8%, 4.0%, 5.2%, and 9.1%, respectively. Of 62 patients, 9 were observed, 27 underwent surgical revision, 15 underwent percutaneous stent implantation, 8 received a heart transplant, and 2 died before intervention. One patient underwent surgical revision and later stent implantation. The mortality with therapeutic intervention was 9/53 (17.0%).

CONCLUSIONS

Although uncommon, HM 3 LVAD-supported patients might develop eOGO with an increasing incidence after 1 year of support. Although engineering efforts to reduce this complication are under way, clinicians must maintain a focus on early detection and remain vigilant.

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.

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.

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.

Feasibility of an Animal Model for Cavopulmonary Support With a Double-Outflow Pump

Both single- and double-outflow cavopulmonary assist devices (CPADs) were recently proposed for the Fontan population, whereas single-outflow configurations were evaluated in large animal trials and double-outflow concepts are lacking an equivalent in vivo assessment. The aim of this study was to test the hemodynamic properties of a double-outflow CPAD device in an acute sheep model. The two inflow cannulae of a CPAD were anastomosed to the caval veins. Outflow graft connection was performed via end-to-side anastomosis to the right (RPA) and main pulmonary artery (MPA). Speed ramp protocols were conducted, and hemodynamic effects were monitored in terms of caval flows, cardiac output (CO), central venous pressure (CVP), pulmonary artery pressure (PAP), and left atrial pressure (LAP). Six experiments were conducted (53.35 ± 5.1 kg). In three experiments, the animal model was established, the CPAD was examined, and restoration of biventricular equivalency in terms of venous return was achieved. Venous pressures (CVP) declined linearly with increasing pump speed (r > 0.879), whereas caval flow (r > 0.973), CO (r > 0.993), PAP (r > 0.973), and LAP (r > 0.408) increased. Despite the considerable complexity of the sheep model caused by the sheep pulmonary arterial anatomy that requires substantial graft bending, the CPAD was evaluated in three acute experiments and showed the potential to completely substitute a subpulmonary ventricle.

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.

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.

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.

Impact of ABO Blood Group on Thromboembolic and Bleeding Complications in Patients with Left Ventricular Assist Devices

BACKGROUND

 The ABO blood group system is linked to hemostasis via its relationship with von Willebrand factor (VWF) and factor VIII (FVIII). In the current study, we investigated the association of the ABO system with clinical outcomes as well as VWF and platelet function in patients with left ventricular assist devices (LVADs).

METHODS

 Bleeding and thromboembolic complications were assessed in 111 patients during 1 year after LVAD implantation. In 67 LVAD patients, VWF antigen, VWF activity, VWF ristocetin cofactor, VWF collagen-binding, and FVIII activity were assessed. Platelet surface P-selectin and activated glycoprotein IIb/IIIa were determined by flow cytometry, and soluble P-selectin was measured with an enzyme-linked immunoassay. Platelet aggregation was assessed by light transmission and impedance aggregometry.

RESULTS

 Thirty-six patients (32.4%) experienced a bleeding and 22 patients (19.8%) a thromboembolic event. In univariate analyses, patients with blood group O had numerically more bleeding complications and less thromboembolic events as compared to patients with blood group non-O (both p ≥ 0.05). After multivariable adjustment, blood group O was significantly associated with a higher risk of bleeding (hazard ratio 2.42 [95% confidence interval 1.03-5.70], p = 0.044) but not linked to thromboembolic complications.

CONCLUSION

 Patients with blood group O had significantly lower levels of VWF and FVIII (all p < 0.05), whereas P-selectin expression in response to thrombin-receptor activating peptide and soluble P-selectin were higher as compared to patients with blood group non-O (both p < 0.05). LVAD patients with blood group O are at an increased bleeding risk, potentially due to lower VWF and FVIII levels.

It's not only the pump: Assessment of human factors of wearable components and user experience of patients with left ventricular assist devices

BACKGROUND

Despite design improvements in left ventricular assist devices (LVADs) over the past decade, limitations of external, wearable VAD components affect patient quality of life and safety. The aim of this study was to describe both user experience and human factor issues of 2 contemporary LVADs.

METHODS

This single-center, cross-sectional study included LVAD outpatients who were at least 3 months after implantation. Before developing the 16-item survey, a systematic literature review and 2-round Delphi method involving 9 VAD clinicians were used to select items in 6 domains: power supply, emergency situations, wearability, mobility, and freedom to travel, user modifications, lifestyle, and home adaptations.

RESULTS

Fifty-eight patients (61.6 ± 11.6 years, 13.8% female, HeartMate 3 (HM3)/HVAD: n = 39/19) completed the one-time survey after median of 853 days on device: 10.3% reported problems changing power supply, 12.7% unintentional driveline disconnection (HM3: 5.6% vs HVAD: 26.3%, p = 0.041). Against the recommendation 74.1% sleep with battery-support (HM3: 88.9% vs HVAD: 44.4%, p = 0.001). About 65.3% criticized the carry bag weight/size (HM3: 71.4% vs HVAD: 50.0%, p = 0.035), thus 24.1% wear an own carrying-system, 42.1% modified their wearables, 38.9% their clothing, and 65.3% their home to cope with life on LVAD support. Mobility is reduced due to limited wearability: 18.9% went abroad (only 3.7% by plane) and 40.0% use less public transport than before implantation (the older the less: r = -0.37, p = 0.013).

CONCLUSIONS

HVAD and HM3 wearables still show a variety of human factors issues and potential for improved user experience. User-centered design and incorporation of patient feedback may increase user satisfaction, and patient safety.

The effect of occlusive polytetrafluoroethylene outflow graft protectors in left ventricular assist device recipients

BACKGROUND

The use of polytetrafluoroethylene (PTFE) material as a protective cover for left ventricular assist device (LVAD) outflow grafts (OG) is a common practice. However, it has descriptively been linked to the development of blood flow obstruction (BFO).

METHODS

Patient data from 194 consecutive HVAD (Medtronic Inc; Medtronic, Minneapolis, MN) recipients implanted between March 2006 and January 2021 were retrospectively analyzed. PTFE covers were used in 102 patients. Study outcomes included the incidence of BFO and survival on LVAD support.

RESULTS

Thirty-seven patients (19.1%) developed BFO during the study period. On a multivariable Cox regression analysis, PTFE use was an independent predictor for the development of BFO (HR 2.15, 95% CI 1.03-4.48, p = .04). BFO comprised of 2 types of device malfunction: eleven patients (5.7%) developed outflow graft stenosis (OGS), and 31 patients (16.0%) developed pump thrombosis (PT). There was a significantly higher cumulative incidence of OGS in patients with PTFE cover than in those without (Gray's test, p =.03). However, the observed higher cumulative incidence of PT in PTFE patients was non-significant (Gray's test, p =.06). In a multivariable Cox regression model, the effect of PTFE use on survival was non-significant (HR 0.95, 95% CI 0.60-1.48, p =.81), while the development of BFO was independently associated with increased mortality (HR 3.43, 95% CI 1.94-6.06, p < .0001).

CONCLUSIONS

The use of PTFE OG cover in LVAD patients is associated with an increased cumulative probability of development of BFO, the latter adversely impacting survival and is therefore, harmful.

Left atrial appendage occlusion in ventricular assist device patients to decrease thromboembolic events: A computer simulation study

Atrial fibrillation (AF) is a common comorbidity in left ventricular assist device (LVAD) patients and has been identified as a risk factor for thromboembolic stroke. Blood stagnation within the left atrial appendage (LAA) is considered a possible major source of thrombosis and clinical studies have shown reduced thromboembolic risk after LAA occlusion (LAAO). Therefore, this study aims to investigate the effect of LAAO on thrombosis-related parameters using patient-specific simulations. Left ventricular and left atrial geometries of an LVAD patient were obtained from computed tomography and combined with hemodynamic data with either sinus rhythm (SR) or AF generated by a lumped parameter model. In four simulations applying contractile walls, stagnation volume and blood residence times were evaluated with or without AF and with or without LAAO. Reduced atrial contraction in AF resulted in unfavorable flow dynamics within the left atrium. The average atrial velocity was lower for the AF simulation when compared to SR, resulting in a 55% increase in the atrial stagnation volume (from 4.2 to 6.5 cm³). Moreover, blood remained in the LAA for more than 8 cardiac cycles. After LAAO the atrial stagnation decreased from 4.2 to 1.4 cm³ for SR and from 6.5 to 2.3 cm³ for the AF simulation. A significant stagnation volume was found in the LAA for both SR and AF, with larger values occurring with AF. These regions are known as potential sources for thrombus formation and can be diminished by LAAO. This significantly improved the thrombus-related flow parameters and may also lower the risk of thromboembolic events from the appendage.

Obesity and outcomes after left ventricular assist device implantation-insights from the EUROMACS registry

OBJECTIVES

The objective was to analyze associations between obesity and outcomes after left ventricular assist device implantation.

METHODS

A retrospective analysis of the EUROMACS Registry was performed. Adult patients undergoing primary implantation of a continuous-flow left ventricular assist device between 2006 and 2019 were included (Medtronic HeartWare® HVAD®, Abbott HeartMate II®, Abbott HeartMate 3™). Patients were classified in 4 different groups according to body mass index at the time of surgery (body mass index < 20 kg/m2: n = 254; 20-24.9 kg/m2: n = 1281; 25-29.9 kg/m2: n = 1238; ≥ 30 kg/m2: n = 691).

RESULTS

The study cohort was comprised of 3464 patients. Multivariable Cox proportional cause-specific hazards regression analysis demonstrated that obesity (body mass index ≥ 30 kg/m2) was independently associated with significantly increased risk of mortality (body mass index "≥ 30" vs "20-24.9" kg/m2: hazard ratio 1.36, 95% confidence interval 1.18 to 1.57, overall p < 0.001). Moreover, obesity was associated with significantly increased risk of infection and driveline infection. The probability to undergo heart transplantation was significantly decreased in obese patients (body mass index "≥ 30" vs "20-24.9" kg/m2: hazard ratio 0.59, 95% confidence interval 0.48 to 0.74, overall p < 0.001).

CONCLUSIONS

Obesity at the time of left ventricular assist device implantation is associated with significantly higher mortality and increased risk of infection as well as driveline infection. The probability to undergo heart transplantation is significantly decreased. These aspects should be considered when devising a treatment strategy before surgery.

A Sensorless Modular Multiobjective Control Algorithm for Left Ventricular Assist Devices: A Clinical Pilot Study

Background

Contemporary Left Ventricular Assist Devices (LVADs) mainly operate at a constant speed, only insufficiently adapting to changes in patient demand. Automatic physiological speed control promises tighter integration of the LVAD into patient physiology, increasing the level of support during activity and decreasing support when it is excessive.

Methods

A sensorless modular control algorithm was developed for a centrifugal LVAD (HVAD, Medtronic plc, MN, USA). It consists of a heart rate-, a pulsatility-, a suction reaction—and a supervisor module. These modules were embedded into a safe testing environment and investigated in a single-center, blinded, crossover, clinical pilot trial (clinicaltrials.gov, NCT04786236). Patients completed a protocol consisting of orthostatic changes, Valsalva maneuver and submaximal bicycle ergometry in constant speed and physiological control mode in randomized sequence. Endpoints for the study were reduction of suction burden, adequate pump speed and flowrate adaptations of the control algorithm for each protocol item and no necessity for intervention via the hardware safety systems.

Results

A total of six patients (median age 53.5, 100% male) completed 13 tests in the intermediate care unit or in an outpatient setting, without necessity for intervention during control mode operation. Physiological control reduced speed and flowrate during patient rest, in sitting by a median of −75 [Interquartile Range (IQR): −137, 65] rpm and in supine position by −130 [−150, 30] rpm, thereby reducing suction burden in scenarios prone to overpumping in most tests [0 [−10, 2] Suction events/minute] in orthostatic upwards transitions and by −2 [−6, 0] Suction events/min in Valsalva maneuver. During submaximal ergometry speed was increased by 86 [31, 193] rpm compared to constant speed for a median flow increase of 0.2 [0.1, 0.8] L/min. In 3 tests speed could not be increased above constant set speed due to recurring suction and in 3 tests speed could be increased by up to 500 rpm with a pump flowrate increase of up to 0.9 L/min.

Conclusion

In this pilot study, safety, short-term efficacy, and physiological responsiveness of a sensorless automated speed control system for a centrifugal LVAD was established. Long term studies are needed to show improved clinical outcomes.

Clinical Trial Registration

ClinicalTrials.gov, identifier: NCT04786236.

When Nothing Goes Right: Risk Factors and Biomarkers of Right Heart Failure after Left Ventricular Assist Device Implantation

Right heart failure (RHF) is a severe complication after left ventricular assist device (LVAD) implantation. The aim of this study was to analyze the incidence, risk factors, and biomarkers for late RHF including the possible superiority of the device and implantation method. This retrospective, single-center study included patients who underwent LVAD implantation between 2014 and 2018. Primary outcome was freedom from RHF over one-year after LVAD implantation; secondary outcomes included pre- and postoperative risk factors and biomarkers for RHF. Of the 145 consecutive patients (HeartMate 3/HVAD: n = 70/75; female: 13.8%), thirty-one patients (21.4%) suffered RHF after a mean LVAD support of median (IQR) 105 (118) days. LVAD implantation method (less invasive: 46.7% vs. 35.1%, p = 0.29) did not differ significantly in patients with or without RHF, whereas the incidence of RHF was lower in HeartMate 3 vs. HVAD patients (12.9% vs. 29.3%, p = 0.016). Multivariate Cox proportional hazard analysis identified HVAD (HR 4.61, 95% CI 1.12–18.98; p = 0.03), early post-op heart rate (HR 0.96, 95% CI 0.93–0.99; p = 0.02), and central venous pressure (CVP) (HR 1.21, 95% CI 1.05–1.39; p = 0.01) as independent risk factors for RHF, but no association of RHF with increased all-cause mortality (HR 1.00, 95% CI 0.99–1.01; p = 0.50) was found. To conclude, HVAD use, lower heart rate, and higher CVP early post-op were independent risk factors for RHF following LVAD implantation.

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.

Driveline Features as Risk Factor for Infection in Left Ventricular Assist Devices: Meta-Analysis and Experimental Tests

Background: Risk factors for driveline infection (DLI) in patients with left ventricular assist devices are multifactorial. The aim of this study was to analyze the correlation between mechanical driveline features and DLI occurrence.

Methods: A meta-analysis was conducted that included studies reporting DLI rates at 6 months after implantation of any of three contemporary devices (HVAD with Pellethane or Carbothane driveline, HeartMate II, and HeartMate 3). Further, outer driveline diameter measurements and ex-vivo experimental three-point bending and torsion tests were performed to compare the stiffness of the four different driveline types.

Results: 21 studies with 5,393 patients were included in the meta-analysis. The mean weighted DLI rates ranged from 7.2% (HeartMate II) to 11.9% (HeartMate 3). The HeartMate II driveline had a significantly lower maximal bending force (Load_max) (4.52 ± 0.19 N) compared to the Carbothane HVAD (8.50 ± 0.08 N), the HeartMate 3 (11.08 ± 0.3 N), and the Pellethane HVAD driveline (15.55 ± 0.14 N) (p < 0.001). The maximal torque (Torque_max) of the HeartMate II [41.44 (12.61) mNm] and the Carbothane HVAD driveline [46.06 (3.78) mNm] were significantly lower than Torque_max of the Pellethane HVAD [46.06 (3.78) mNm] and the HeartMate 3 [95.63 (26.60) mNm] driveline (p < 0.001). The driveline of the HeartMate 3 had the largest outer diameter [6.60 (0.58) mm]. A relationship between the mean weighted DLI rate and mechanical driveline features (Torque_max) was found, as the the HeartMate II driveline had the lowest Torque_max and lowest DLI rate, whereas the HeartMate 3 driveline had the highest Torque_max and highest DLI rate.

Conclusions: Device-specific mechanical driveline features are an additional modifiable risk factor for DLI and may influence clinical outcomes of LVAD patients.

Effects of the atrium on intraventricular flow patterns during mechanical circulatory support

Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm³), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.

Incidence, clinical relevance and therapeutic options for outflow graft stenosis in patients with left ventricular assist devices

OBJECTIVES

We reviewed our institutional experience with outflow graft stenosis (OGS) in 3 contemporary left ventricular assist devices (LVAD).

METHODS

Data from 347 consecutive adult recipients of LVAD [Medtronic HVAD (n = 184, 53.0%), Abbott HeartMate II (n = 62, 17.9%) and Abbott HeartMate 3 (n = 101, 29.1%)] implanted between March 2006 and October 2019 were analysed retrospectively. Primary study end points were the incidence of OGS necessitating treatment and survival on LVAD support.

RESULTS

During the study period, 17 patients (4.9%) developed OGS requiring treatment with a probability of 0.6% at 1 year, 1.9% at 2 years, 3.8% at 3 years, 4.7% at 4 years and 5.9% at 5 years of LVAD support. Notably, in 13.8% of patients, a compression-related narrowing of the outflow graft with a probability of 1.5% at 6 months, 1.8% 1 year, 6.0% at 2 years, 12.3% at 3 years, 15.4% at 4 years and 16.6% at 5 years of LVAD support with no difference between devices (P = 0.26) was observed. There was a trend towards increased risk of mortality with OGS (hazard ratio 2.21, 95% confidence interval 0.87-5.51; P = 0.09). OGS preferentially occurred in segments of the outflow graft covered by a protective coating.

CONCLUSIONS

OGS is a rare but potentially lethal complication during LVAD support. Modifications of pump design and implant techniques may be needed because OGS preferentially occurs within covered portions of the outflow graft. Systematic screening may be warranted.

Pump position and thrombosis in ventricular assist devices: Correlation of radiographs and CT data

Malpositioning of left ventricular assist devices (LVAD) is a risk factor for thrombosis, but its identification from clinical imaging remains challenging. X-rays and CT scans were analyzed and parameters identified that correlated to pump thrombosis. Retrospective imaging data of patients (n = 115) with HeartmateII (HMII) or HVAD were analyzed in two groups (pump-thrombosis PT, n = 15 vs matched control group NT, n = 15) using routine X-rays and CT scans. In CT, directional deviations of the inflow cannula in three-chamber and two-chamber view (α and β angles) were identified. In HVAD PT frontal radiographs showed reduced pump body area and smaller minor axis (PT 41.3 ± 4.8 mm vs NT 34.9 ± 6.0 mm, p = 0.026), and in the lateral radiographs the visibility of the inflow cannula served as a predictive parameter for PT. In HMII patients, no parameters were associated with PT. The angle α differed significantly (NT −1.2 ± 7.5°, PT −22.0 ± 4.7°, p = 0.006) in HVAD patients. Further, correlations of x-ray parameters with CT angles α and β showed that radiographs can be used to identify malpositioned pumps. Well-aligned inflow cannula positions are essential. HVAD patients with a posterior rotation of the inflow cannula have a higher risk of pump thrombosis. This risk can reliably be identified from routine radiographs.

Mechanical circulatory support in pediatric patients with biventricular and univentricular hearts

Background

Mechanical circulatory support (MCS) in pediatric patients remains challenging because of small body size, limited availability of approved devices, and the variety of etiologies, including biventricular and univentricular physiologies. We report our single-center experience with MCS in pediatric patients in terms of survival and adverse events.

Methods

Outcome, etiologic, and demographic data of pediatric patients implanted with a long-term MCS device between 2011 and 2019 at the Medical University of Vienna were retrospectively collected and analyzed. Overall survival and freedom of treatment-related adverse events at 1 year were investigated by Kaplan–Meier analyses and stratified for circulation (biventricular vs univentricular), age group (<6 years vs >6 years), and pump technology (pulsatile ventricular assist device [p-VAD] vs continuous flow pump [cf-VAD]).

Results

One-year survival of all 33 pediatric patients (median, 4 years; interquartile range, 0-13 years) was 73%, with a tendency toward better outcomes in patients with biventricular circulation than in those with univentricular circulation (80%; n = 25 vs 50%; n = 8; P = .063). The trends toward better survival probability in older patients and in patients with cf-VADs did not reach statistical significance (63.2% vs 85.7%; P = .165 and 82.4% vs 62.5%; P = .179, respectively). Freedom from adverse events was higher in older patients (57.1% vs 5.6%; P < .001) and in the cf-VAD group (52.9% vs 0%; P < .001), with pump thrombosis as the main discriminator.

Conclusions

MCS is a promising therapy for a broad spectrum of pediatric patients, irrespective of heart failure etiology, age, and pump type. With increasing experience, improved devices, and patient selection, MCS may become a valuable treatment option for patients with univentricular hearts.

Concomitant cardiac surgery procedures during left ventricular assist device implantation: single-centre experience

Background

Additional cardiac pathologies including tricuspid or mitral valve regurgitation are common in left ventricular assist device (LVAD) recipients and whether to address them remains controversial. We present our institutional outcomes of concomitant cardiac procedures, other than temporary right ventricular (RV) support, at the time of LVAD implantation.

Methods

From 03/2006 to 06/2020, 352 adult patients {median age 60 [interquartile range (IQR): 52-66] years; INTERMACS level 1 29%; INTERMACS level 2 17%; INTERMACS level 3 23%, INTERMACS level 4-6 31%; male 86%} underwent continuous-flow LVAD [Medtronic HVAD^® (HVAD) 50%; Abbott HeartMate II^TM (HMII) 17%; Abbott HeartMate 3^TM (HM3) 33%] implantation. Concomitant valvular procedures were performed in 86 patients (24%) and the majority of patients received the LVAD as bridge to candidacy (BTC) for transplant (74%). Primary study endpoints were short- and mid-term mortality, as well as need for temporary RV support.

Results

Tricuspid valve annuloplasty was the most frequent concomitant procedure (77%), followed by aortic valve replacements (AVRs) or Park's stitch (33%). Temporary RV support was common in the study cohort (35%) using either extracorporeal life support (ECLS, 37%) or a temporary RV assist device (RVAD, 63%). A less invasive (LIS) implantation technique was pursued in 12%. Thirty-day mortality was comparable between those with and without concomitant surgery (4% vs. 6%, P=0.426). In-hospital mortality was significantly higher for additional interventions (22% vs. 14%, P=0.05), whereas one-year survival was similar (71% vs. 79%, P=0.106).

Conclusions

Concomitant cardiac procedures, especially tricuspid and aortic valve surgery, are frequent but are associated with a higher perioperative morbidity and mortality.

The left ventricular assist device as a patient monitoring system

Technological progress of left ventricular assist devices (LVADs) towards rotary blood pumps and the optimization of medical management contributed to the significant improvements in patient survival as well as LVAD support duration. Even though LVAD therapy is now well-established for end-stage heart failure patients, the long-term occurrence of adverse events (AE) such as bleeding, infection or stroke, still represent a relevant burden. An early detection of AE, before onset of major symptoms, can lead to further optimization of patient treatment and thus mitigate the burden of AE. Continuous patient monitoring facilitates identification of pathophysiological states and allows anticipation of AE to improve patient management. In this paper, methods, algorithms and possibilities for continuous patient monitoring based on LVAD data are reviewed. While experience with continuous LVAD monitoring is currently limited to a few centers worldwide, the pace of developments in this field is fast and we expect these technologies to have a global impact on the well-being of LVAD patients.

Impact of Less Invasive Left Ventricular Assist Device Implantation on Heart Transplant Outcomes

Left ventricular assist device implantation without sternotomy (LIS) may simplify heart transplantation (HTX) by avoiding adhesions and eliminating the need for a re-sternotomy. This study investigates the impact of LIS LVAD implantation on HTX outcomes. A retrospective comparison of 46 patients undergoing HTX between 07/13 and 06/19 after conventional LVAD implantation with a full sternotomy (FS) and LIS LVAD implantation (LIS: n = 27 patients, 59%; FS: n = 19 patients, 41%) was performed. Endpoints were perioperative data including blood product use, de-novo formation of donor specific antibodies (DSAs) and survival. Patient demographics (mean age FS: 60.3 ± 9.3 years vs LIS 58.0 ± 7.7 years, P = 0.313; male gender FS: 84% vs LIS: 82%, P = 1.000; urgent HTX FS: 16% vs LIS 18%, P = 1.000) were comparable between LIS and FS patients. The primary finding was a significantly higher risk to develop de novo donor specific antibodies (DSAs) after HTX in patients of the FS group (FS: 36% vs LIS: 4%; P = 0.006). LIS patients had a significant reduction of intraoperative packed red blood cells (PRBCs) use (LIS: 4 (IQR 2-7) Units vs FS: 7 (IQR 4-8) Units; P = 0.045). Other adverse events rates and in-hospital mortality (LIS: 7% vs FS 5%, P = 1.000) were comparable between both groups. LIS LVAD reduces formation of donor specific antibodies after HTX.

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.

Thrombolysis as first-line therapy for Medtronic/HeartWare HVAD left ventricular assist device thrombosis

OBJECTIVES

METHODS

From March 2006 to November 2018, 30 Medtronic/HeartWare HVAD left ventricular assist device patients had 48 PT events. We analysed outcomes with intravenous Alteplase as a first-line therapy for PT. Pump exchange or urgent heart transplantation was only considered after the failure of TL or existing contraindications to TL.

RESULTS

TL was used as the first-line therapy in 44 PT events in 28 patients without a contraindication to TL. TL was successful in 61.4% of PT events. More than 1 cycle of TL was necessary in 55.6% of events. The combined success of TL and heart transplantation or device exchange was 81.8%. In 15.9% of events, PT was fatal. Causes of death were severe complications (9.1%) related to TL or discontinuation of therapy for multi-organ failure (6.8%). Intracranial bleeding and arterial thromboembolism were observed in 4.5% and 11.5% of the PT events after TL.

CONCLUSIONS

Intravenous TL as a first-line therapy for PT in Medtronic/HeartWare HVAD patients can be a reasonable treatment option and does not preclude subsequent heart transplantation or device exchange. However, thromboembolic and bleeding complications are common. The decision to perform TL or device exchange should, therefore, be made on an individual basis after balancing the risks and benefits of different treatment approaches.

Blood stream infection and outcomes in recipients of a left ventricular assist device

OBJECTIVES

METHODS

We retrospectively analysed all adult recipients of a continuous-flow LVAD between 2006 and 2016 at the Division of Cardiac Surgery, Medical University of Vienna (n = 257; devices: Medtronic HeartWare® HVAD®, Abbott HeartMate II®, Abbott HeartMate 3™). The primary outcome was all-cause mortality during follow-up. Secondary outcomes included the risk of stroke and pump thrombus during follow-up as well as the probability of heart transplantation (HTx). Risk factors for the development of ≥1 positive BC were evaluated additionally.

RESULTS

The incidence of ≥1 positive BC during the first year of LVAD support was 32.1% [95% confidence interval (CI) 26.4–37.9]. Multivariable Cox proportional cause-specific hazards regression analysis showed that a positive BC was associated with significantly increased all-cause mortality [hazard ratio (HR) 5.51, 95% CI 3.57–8.51; P &lt; 0.001]. Moreover, a positive BC was associated with a significantly increased risk of stroke (HR 2.41, 95% CI 1.24–4.68; P = 0.010). There was no association with the risk of pump thrombus or the probability of HTx. Independent risk factors for a positive BC included preoperative albumin and extracorporeal membrane oxygenation/intra-aortic balloon pump support.

CONCLUSIONS

Blood stream infection is common and associated with a significantly increased risk of all-cause mortality and stroke at any given time during LVAD support. Effective strategies of prevention and treatment are necessary.

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.

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.

Influence of a fully magnetically levitated left ventricular assist device on functional interrogation of implantable cardioverter defibrillators

Background

Electromagnetic interference between left ventricular assist devices (LVAD) and the telemetry wand of implantable cardioverter‐defibrillators (ICD) with impairment of ICD interrogation has previously been described in HVAD and HeartMate II devices. This is the first study showing the potential influence of the LVAD model HeartMate 3 (with the unique feature of fully magnetically levitated rotor with consistent wide blood‐flow gaps) on functional interrogation of different ICD models.

Methods and Results

Among 51 patients treated with a HeartMate 3 LVAD, 34 patients (66.7%) already had an ICD implanted prior to LVAD therapy. In this cohort, impairment of ICD interrogation was observed in five patients (14.7%) with five different device models. In patients with Biotronik ICD, stretching of the ipsilateral arm to increase the distance between both devices >10 cm was sufficient in one patients, whereas surgical contralateral repositioning was necessary in two patients; in one further patient no action could be taken, as he died early from embolic stroke. In the only patient with a MicroPort ICD, this issue was resolved by using a wireless telemetry. The distances between both devices showed no statistical significant correlation with an impaired interrogation, neither in the overall collective nor within the groups with the same manufacturer.

Conclusions

In patients with impaired ICD interrogation caused by electromagnetic interference between a HeartMate 3 LVAD and the ICD, the actions mentioned above have to be taken, to resolve this technical issue. Especially, a sufficient distance of at least 10 cm between both devices was crucial for avoiding this problem.

Noninvasive assessment of blood pressure in rotary blood pump recipients using a novel ultrasonic Doppler method

In rotary blood pump recipients with low blood pressure pulsatility, current oscillometric methods to measure blood pressure are not applicable. The aim of this study was to use ultrasonic Doppler flow measurements to determine blood pressure in this patient population noninvasively. In 28 rotary blood pump recipients, blood pressure was measured three times with the developed Doppler method and compared to the invasive arterial line (n = 15) or to the oscillometric Terumo Elemano BP monitor (n = 13). Blood velocities in the radial artery were recorded by the new Doppler sensor during cuff deflation. A sigmoid curve was fitted to a preprocessed velocity signal and the systolic and mean arterial pressures were determined. A total of 84 measurements were performed, and 17 recordings were visually excluded from further analysis due to obvious artifacts. Both the systolic and mean pressures derived by the Doppler method were in good accordance with the invasively measured pressure (3.7 ± 6.6 mmHg for the systolic and -2.1 ± 7.3 mmHg for the mean pressure). A good agreement between the oscillometric monitor and the Doppler method for the systolic (0.0 ± 6.0 mmHg) and mean (1.0 ± 5.9 mmHg) pressures was observed. In this study, a new Doppler blood pressure measurement system was developed and clinically validated. The novel sensor allows easier placement above the radial artery compared to commercial probes. An algorithm was developed which processes the Doppler signal robustly and is able to determine the systolic as well as the mean arterial blood pressure.

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 (Q_LVAD ), 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 Q_LVAD : +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 Q_LVAD 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.

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.

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.