Left Ventricular Assist Device Pump Research Articles

Left Ventricular Assist Device Pump Obstruction Reduces Native Heart Efficiency.

Obstruction of the LVAD flow path can occur when blood clots or tissue overgrowth form within the inflow cannula, pump body, or outflow graft, and it can lead to thrombus, embolism, and stroke. The goal of this study was to measure the impact of progressive pump inflow obstruction on the pressure and flow dynamics of the LVAD-supported heart using a mock circulatory loop. Pump obstruction (PO) was produced by progressively blocking a fraction of the LVAD inlet area. Pressures, flows, and the midplane velocity field of the LV were measured for three LVAD speeds and six PO levels. Pressure and flow decreased with PO, shifting more of the flow through the aortic valve such that the total flow decreased by 6-11% and decreased the efficiency of the work of the native heart up to 60%. PO restricts diastolic flow through the LVAD, which reduces mitral inflow and decreases the strength and energy of the intraventricular vortices. The changes in flow architecture produced by PO include flow stasis and increased shear, which predispose the system to thromboembolic risk. Analysis of the contributions to external work may enable early detection, which allows time for therapeutic intervention, reducing the likelihood of pump replacement and the risk of complications.

Abstract 13623: In Silico Comparison of Pressure Head Loss for Outflow Variations of a Novel LVAD Accessory Compared to Generic LVAD Pump Outflow

Introduction: Left ventricular assist device (LVAD) implantation is a treatment option for end-stage heart failure, requiring a sternotomy. A novel accessory, redirecting the outflow via the left ventricular apex into the ascending aorta, allows for LVAD implantation via left thoracotomy. Pressure distribution within accessory designs is unknown. Our goal was to compare three different outflow designs with a generic LVAD outflow (Control) to optimize the accessory’s outflow design. Hypothesis: We hypothesize that the LVAD accessory leads to higher pressure head loss than Control and that there are relevant differences among varied designs. Methods: Volume models of the LVAD accessory variations (A–C) and Control were created using computer aided design. Computational fluid dynamics (CFD) was used to simulate blood flow through the accessories and generic outflows. A verification study was performed to optimize numerical parameters. Pressure head loss (mmHg) was calculated for each outflow while changing the LVAD flow rate continuously (2–7 L/min). Pressure loss was compared by mean differences (MD). Results: Pressure head loss increased with higher LVAD flow rate among all groups. Addressing the accessories’ outflow designs, Design B revealed the lowest increase in pressure loss revealing a mean slope of 2.3 mmHg/L/min compared to 4.6 and 3.0 for Design A and C. Referring to a flow rate of 5.5 L/min, a common flow rate among clinical LVAD patients, and comparing pressure head loss with Control, we found an additional pressure loss of 15.5, 6.4 and 8.3 mmHg in Design A, B and C, respectively. Conclusion: There is a trade off between fitting the outflow design to the cardiac geometry and the pressure head loss. Continued optimization of the LVAD accessory could allow minimally invasive LVAD implantation with minimal changes in LVAD performance. Potential compromise between improved design and performance renders CFD an important tool for medical device development.

Abstract 16276: Complex Corynebacterium Case: Management of Recurrent Corynebacterium Bacteremia in a Patient With Cardiac Implanted Electronic Device and Left Ventricular Assist Device

Background Cardiac implantable electronic device (CIED) infections are morbid and costly. Atypical organisms are increasingly recognized as a cause of CIED infections. We present a case of recurrent Corynebacterium striatum bacteremia requiring CIED and left ventricular assist device (LVAD) extraction. Case Presentation A 54-year-old female dialysis patient with diabetes, ischemic cardiomyopathy, primary prevention single chamber transvenous defibrillator (ICD) 8 years prior, and destination LVAD presented with chronic C. striatum driveline site infection and relapsing and remitting bacteremia. Over the prior two years, she suffered from chronic driveline infections requiring wound care, driveline washouts, and antibiotics, although not seen by the electrophysiology (EP) team. After a fourth episode of bacteremia, she underwent ICD extraction and LVAD pump exchange, followed by 6 weeks of vancomycin and 3 months of rifampin. She then remained free of bacteremia for 19 months, though continued to demonstrate evidence of driveline infection despite pump exchange. Ultimately, C. striatum bacteremia recurred. Given unrelenting soft tissue infection and recurrent bacteremia, redo LVAD exchange was deferred and she was treated with lifelong suppressive antibiotics. Discussion Corynebacterium species have historically been considered skin flora, but more recently have been identified as pathogens, both as a cause of endocarditis, and a common organism in LVAD associated soft tissue infections. There are few reports of CIED infection. Source control is difficult in bacteremia patients with both CIED and LVAD. In this case, recurrent bacteremia could be attributed to recurrent driveline-soft tissue infection. However, the prolonged freedom from bacteremia off antibiotics after CIED extraction, despite ongoing soft tissue and driveline infection, argues that her transvenous ICD may have been seeded. This case highlights the growing spectrum of bacteria implicated in CIED-related infection, that early extraction may be a critical intervention regardless of infectious source, and importance of multidisciplinary discussions including heart failure, surgery, infectious disease, and EP to improve outcomes in this complex population.

Design and optimisation of an Intra-Aortic Shrouded rotor axial pump

Undesirable side effects in patients with a LVAD (Left Ventricular Assist Device) pump fitted include blood damage, thrombosis, blood traumatisation, and End-Organ Disfunctions. These side effects have generally been attributed to the high wall shear stresses and the induced turbulent flow. In this study, we introduce a novel design to address these effects by lowering the rotational speed and providing an optimum flow path design to minimise blood damage. We present an initial scheme for a new Intra-Aortic Shrouded Rotary Axial Pump and develop a sequence of pump geometries, for which the Taguchi Design Optimisation Method has been applied. We apply CFD tools to simulate the pressure rise, pump performance, hydraulic efficiency, wall shear stress, exposure time and mass flow rate. A prototype pump has been tested in a mock cardiovascular circuit using a water-glycerol solution. The optimum design delivered the desired pressure/mass flow rate characteristics at a significantly low rpm (2900 rpm). As a result, the estimated blood damage index is low, matching the design requirements. The theoretical performance was matched by experimental results.

Less Invasive Left Ventricular Assist Device Implantation Is Safe and Feasible in Patients With Smaller Body Surface Area.

Smaller body surface area (BSA) frequently precludes patients from left ventricular assist device (LVAD) therapy. We sought to investigate the clinical outcomes in patients with small BSA undergoing less invasive LVAD implantation. We conducted a retrospective review of 216 patients implanted with HeartMate 3 LVAD (Abbott, Chicago, IL) via less invasive surgery at our institution. Patients were dichotomized based on their preimplant BSA for comparison between small BSA (≤1.8 m2) and normal/large BSA (>1.8 m2). We analyzed patient perioperative characteristics and outcomes. In our study, small BSA was found in 32 patients (14.8%), while 184 patients (85.2%) had normal/large BSA. Women were more prevalent in the small BSA group (50.0% vs 13.0%, P < 0.001). Preoperative and intraoperative data showed comparable results. Major complications and hospital length of stay did not differ by BSA group. Patients with smaller BSA had significantly decreased pump parameters at discharge, including LVAD flow (4.11 ± 0.49 vs 4.60 ± 0.54 L/min, P < 0.001) and pump speed (5,200 vs 5,400 rpm, P < 0.001). Survival to discharge and within 6 months after implantation were similar between the groups. Our study results suggest that less invasive HeartMate 3 implantation can be safely performed and demonstrates equivalent outcomes in patients with smaller body habitus. Randomized trials are required to confirm our data.

Clinical Outcomes of Left Ventricular Assist Device Pump Infection.

Few studies have focused on the clinical outcomes and risk factors of left ventricular assist device (LVAD) pump infection, and no standard treatment for LVAD pump infection has been established. Therefore, we used a therapeutic flowchart to manage LVAD pump infections. We retrospectively evaluated 220 patients who underwent continuous-flow LVAD implantation between January 2005 and March 2021 at Osaka University, Japan. First, we performed wound debridement, negative-pressure wound therapy, antibiotic treatment, and omental flap transposition. Subsequently, we administered conservative treatment, scheduled implantable LVAD exchange, or emergent removal of the implantable LVAD and exchange for extracorporeal LVAD or percutaneous LVAD (IMPELLA). Pump infections occurred in 32 patients. The survival rates of patients with pump infections during LVAD support were 93%, 74%, and 61% at 180 days, 1 year, and 2 years after LVAD pump infection, respectively. Fifteen patients underwent successful heart transplantation. Bridge-to-bridge surgery, preoperative use of venoarterial extracorporeal membrane oxygenation or percutaneous LVAD, high lactate dehydrogenase levels, and driveline infection were significantly associated with pump infection. Our study reveals that poor preoperative condition and driveline infection were significant risk factors for LVAD pump infection.

P23: Preservation of Pulsatility with Universal Ventricular Assist Device: An In Vitro Assessment of Biventricular Support

Objective: The objective of this study was to assess the ability and performance of the Universal Ventricular Assist Device (UVAD) to maintain pulsatility when used as a biventricular assist device (BVAD) through an in vitro experiment utilizing a pulsatile biventricular mock circulatory loop. Methods: The UVAD pumps were evaluated in a dual configuration (BVAD) in the simulated circulatory model under conditions of left heart failure (HF), right HF, and moderate/severe biventricular HF. Measurements of total flow, pulse pressure in the aorta, pulse augmentation factor (PAF), energy-equivalent pressure (EEP), and surplus hemodynamic energy (SHE) were taken at various pump speeds to assess pulsatility. Results: The association between the maximum and minimum pressures and various parameters of the pump was determined during the cardiac cycle. It was observed that the pulse pressure increased across all heart conditions (Figure 1). The PAF ranged from 17-35% in healthy, LHF, RHF, and mild BHF conditions, with the highest PAF, 90%, being observed in the severe BHF condition. EEP correlated with LVAD flow in all groups (R2 = 0.87-0.97) and increased from baseline in all cases. SHE peaked at approximately 5-6 L/min of LVAD support and tended to dissipate surplus energy at higher LVAD pump flow. The greatest decrease in SHE from baseline, 53%, was observed in the mild BHF condition with the highest levels of left ventricular assist device (LVAD) and right ventricular assist device (RVAD) support. Conclusion: The UVAD successfully demonstrated the ability to preserve pulsatility in vitro, and to optimize cardiac output, as an isolated circulatory support device option (RVAD or LVAD), and when used for BVAD support.Figure 1. The relationships between LVAD/RVAD pump flow and aortic pulse pressure/PAF/EEP/SHE in each heart condition. LVAD, left ventricular assist device; RVAD, right ventricular assist device; AoP, aortic pressure; EEP, energy-equivalent pressure; SHE, surplus hemodynamic energy.

Estimation of Left Ventricular Stroke Work for Rotary Left Ventricular Assist Devices.

Continuous monitoring of left ventricular stroke work (LVSW) may improve the medical management of patients with rotary left ventricular assist devices (LVAD). However, implantable pressure-volume sensors are limited by measurement drift and hemocompatibility. Instead, estimator algorithms derived from rotary LVAD signals may be a suitable alternative. An LVSW estimator algorithm was developed and evaluated in a range of in vitro and ex vivo cardiovascular conditions during full assist (closed aortic valve [AoV]) and partial assist (opening AoV) mode. For full assist, the LVSW estimator algorithm was based on LVAD flow, speed, and pump pressure head, whereas for partial assist, the LVSW estimator combined the full assist algorithm with an estimate of AoV flow. During full assist, the LVSW estimator demonstrated a good fit in vitro and ex vivo (R 2 : 0.97 and 0.86, respectively) with errors of ± 0.07 J. However, LVSW estimator performance was reduced during partial assist, with in vitro : R 2 : 0.88 and an error of ± 0.16 J and ex vivo : R 2 : 0.48 with errors of ± 0.11 J. Further investigations are required to improve the LVSW estimate with partial assist; however, this study demonstrated promising results for a continuous estimate of LVSW for rotary LVADs.

Subcutaneous implantable cardioverter-defibrillator noise following left ventricular assist device implantation.

The incidence and impact of noise in a subcutaneous implantable cardioverter defibrillator (S-ICD) after left ventricular assist device (LVAD) implantation is not well established. We performed a retrospective study of patients implanted with LVAD and with a pre-existing S-ICD between January 2005 and December 2020 at the three Mayo Clinic centers (Minnesota, Arizona, and Florida). Of the 908 LVAD patients, a pre-existing S-ICD was present in 9 patients (mean age 49.1± 13.7 years, 66.7% males), 100% with Boston Scientific third-generation EMBLEM MRI S-ICD, 11% with HeartMate II (HM II), 44% with HeartMate 3 (HM 3), and 44% with HeartWare (HW) LVAD. The incidence of noise from LVAD-related electromagnetic interference (EMI) was 33% and was only seen with HM 3 LVAD. Multiple measures attempted to resolve noise, including using alternative S-ICD sensing vector, adjusting S-ICD time zone, and increasing LVAD pump speed, were unsuccessful, necessitating S-ICD device therapies to be turned off permanently. The incidence of LVAD-related S-ICD noise is high in patients with concomitant LVAD and S-ICD with significant impact on device function. As conservative management failed to resolve the EMI, the S-ICDs had to be programmed off to avoid inappropriate shocks. This study highlights the importance of awareness of LVAD-SICD device interference and the need to improve S-ICD detection algorithms to eliminate noise.

Accelerated LVAD pump thrombosis in COVID-19 patient: Case report and mini review.

Coronavirus (COVID-19) infection exposes patients with heart failure specially who are on mechanical support to a higher risk of morbidity and mortality. To investigate the impact of COVID-19 infection on left ventricular assist device (LVAD) thrombosis in heart failure patients. We searched the medical electronic records, Medline, PubMed and Cochrane databases for; (LVAD) AND (thrombosis)) AND (covid-19)) AND (heart failure). We divided cases reported into, LVAD thrombosis with COVID-19 infection and compare them with LVAD thrombosis without COVID-19 infection. Demographic data, LVAD device, presentation, treatment and outcomes were reviewed in all the LVAD thrombosis patients. In addition to our case, 8 other cases of LVAD thrombosis associated with COVID and 9 cases of LVAD thrombosis without covid infection were found. Patients with Covid infection had worse presentation and outcomes (3 deaths VS. 1 death in non-covid group). In LVAD patients, pump malfunction due to thrombus development in the inflow cannula, device body, or outflow graft can result in hemodynamic instability, hemolysis and other life-threatening complications. COVID infection significantly increases the risk of mortality in LVAD patient by accelerating the pump thrombosis due to elevated levels of endothelial protein C receptor and thrombomodulin along with procoagulants such as factor VIII, P-selectin, and von Willebrand factor. Significant morbidity and mortality are attributed to LVAD thrombosis, which are exasperated by prothrombotic conditions created in COVID-19 infections.

Hemodynamic Aberrancies in Left Ventricular Assist Device–Associated Heart Failure Syndromes

Hemodynamic Aberrancies in Left Ventricular Assist Device–Associated Heart Failure Syndromes

A Feasible Method to Control Left Ventricular Assist Devices for Heart Failure Patients: A Numerical Study

Installing and developing a sophisticated control system to optimize left ventricular assist device (LVAD) pump speed to meet changes in metabolic demand is essential for advancing LVAD technology. This paper aims to design and implement a physiological control method for LVAD pumps to provide optimal cardiac output. The method is designed to adjust the pump speed by regulating the pump flow based on a predefined set point (operating point). The Frank–Starling mechanism technique was adopted to control the set point within a safe operating zone (green square), and it mimics the physiological demand of the patient. This zone is predefined by preload control lines, which are known as preload lines. A proportional–integral (PI) controller was utilized to control the operating point within safe limits to prevent suction or overperfusion. In addition, a PI type 1 fuzzy logic controller was designed and implemented to drive the LVAD pump. To evaluate the design method, rest, moderate, and exercise scenarios of heart failure (HF) were simulated by varying the hemodynamic parameters in one cardiac cycle. This evaluation was conducted using a lumped parameter model of the cardiovascular system (CVS). The results demonstrated that the proposed control method efficiently drives an LVAD pump under accepted clinical conditions. In both scenarios, the left ventricle pressure recorded 112 mmHg for rest and 55 mmHg for exercise, and the systematic flow recorded 5.5 L/min for rest and 1.75 L/min for exercise.

Arterial Compliance and Continuous-Flow Left Ventricular Assist Device Pump Function.

Durable continuous-flow left ventricular assist devices (cfLVADs) demonstrate superior survival, cardiac functional status, and overall quality of life compared to medical therapy alone in advanced heart failure. Previous studies have not considered the impact arterial compliance may have on pump performance or developed arterial pressure. This study assessed the impact of alterations in arterial compliance, preload, and afterload on continuous-flow pump function and measured hemodynamics using an in-vitro pulsatile mock circulatory loop. Decreased arterial compliance was associated with a significant increase in arterial pressure pulsatility which was not evident in the flow pulsatility, as displayed in pump flow waveforms. There were marked changes in the pump flow waveforms due to the significant alteration in the aortoventricular gradient during diastole according to the changes in compliance. This study demonstrates that changes in systemic blood pressure, afterload, and left ventricular contractility each significantly affects the flow waveform. The association of hypertension with lower aortic compliance results in markedly decreased diastolic flow rates which may be important in contributing to a greater risk of adverse events under cfLVAD support.

Sudden severe left ventricular assist device inflow cannula obstruction caused by huge thrombus after closure of mechanical aortic valve: case report

Thrombus formation is a troublesome and sometimes lethal complication occurring in patients with severe heart failure and supported by a left ventricular assist device (LVAD). Appropriate treatment for pump thrombosis especially in emergency cases with severe pump failure is difficult to choose. Herein, we present important findings of a case of unexpected LVAD pump thrombosis that rapidly developed into serious pump failure and circulatory arrest due to total obstruction of the LVAD inflow tract by a huge thrombus.

Translocation of LVAD Pump and Driveline Causing Bowel Perforation

Introduction Left ventricular assist devices (LVADs) have known risks of device infection and gastrointestinal (GI) bleeding. We present the first known case of LVAD pump migration causing colonic perforation. Case Report A 67-year old man with ischemic cardiomyopathy status post HeartMate II LVAD implantation presented to the emergency department with melena. He was found to be in hemorrhagic shock requiring pressor support, with a hemoglobin of 5.2 g/dl. He had a history of chronic driveline infection with Stenotrophomonas maltophilia treated with long-term suppressive doxycycline and an outflow graft kink requiring stenting 7 months prior. His GI history was notable for recurrent GI bleeding secondary to colonic AVMs and polyps requiring multiple cauterizations and clips. His anticoagulation was periodically interrupted and restarted, as the patient had several readmissions for recurrent GI bleeding, until it was ultimately stopped 3 months prior. This admission, an abdominal CT showed erosion of the LVAD driveline into the transverse colon (Panel A). Subsequent colonoscopy identified the driveline within transverse colon lumen (Panel B). In conjunction with both cardiothoracic and abdominal surgery teams, the patient underwent robotic-assisted colonic exploration which revealed both driveline and LVAD pump had migrated into the colon. Patient underwent removal of the LVAD and primary colo-colonic anastomosis with abdominal washout. Laparoscopic omentopexy was performed to cover the intraabdominal LVAD components. His postoperative course was uncomplicated. Summary This case illustrates a rare but serious complication of LVAD and chronic device infection: migration of LVAD pump and driveline causing colonic perforation. Left ventricular assist devices (LVADs) have known risks of device infection and gastrointestinal (GI) bleeding. We present the first known case of LVAD pump migration causing colonic perforation. A 67-year old man with ischemic cardiomyopathy status post HeartMate II LVAD implantation presented to the emergency department with melena. He was found to be in hemorrhagic shock requiring pressor support, with a hemoglobin of 5.2 g/dl. He had a history of chronic driveline infection with Stenotrophomonas maltophilia treated with long-term suppressive doxycycline and an outflow graft kink requiring stenting 7 months prior. His GI history was notable for recurrent GI bleeding secondary to colonic AVMs and polyps requiring multiple cauterizations and clips. His anticoagulation was periodically interrupted and restarted, as the patient had several readmissions for recurrent GI bleeding, until it was ultimately stopped 3 months prior. This admission, an abdominal CT showed erosion of the LVAD driveline into the transverse colon (Panel A). Subsequent colonoscopy identified the driveline within transverse colon lumen (Panel B). In conjunction with both cardiothoracic and abdominal surgery teams, the patient underwent robotic-assisted colonic exploration which revealed both driveline and LVAD pump had migrated into the colon. Patient underwent removal of the LVAD and primary colo-colonic anastomosis with abdominal washout. Laparoscopic omentopexy was performed to cover the intraabdominal LVAD components. His postoperative course was uncomplicated. This case illustrates a rare but serious complication of LVAD and chronic device infection: migration of LVAD pump and driveline causing colonic perforation.

Unique Findings of Myocardial Improvement with Lower Left Ventricular Assist Device Pump Speed

<h3>Purpose</h3> Currently, optimizing hemodynamics and unloading in patients with left ventricular assist device (LVAD) relies on echocardiography and right heart catherization guidance for pump speed adjustments. However, the ideal unloading strategy to maximize reverse remodelling is uncertain - whether to provide maximal pump support to unload the heart (‘rest'), or maximize ventricular work with partial pump support (‘work'). Using non-invasively derived PV loops, we sought to characterize the longitudinal changes in chamber contractile parameters stroke work (SW), peak systolic pressure (LVP_max) and peak LV elastance (E_es) at different pump speeds [2400 vs 2500 vs 2600 revolutions/min (rpm)]. <h3>Methods</h3> 32 Medtronic HVAD patients (mean 55.9±12.3 yrs, 81.3% male) were included in the study. Single-cycle pressure and volume estimations were performed using a validated algorithm with the following bedside measurements: echo parameters, HVAD controller-derived data and oscillometric brachial pressure waveform (SphygmoCor Xcel). In total, 77 PV loops were prospectively collected at 3 intervals: 1, 3 and 6 months post-implant (n=26, 29, 22). Corresponding ventricular contractile parameters SW, LVP_max and E_es were calculated. Pump speed was included as a fixed effect to determine its impact on the longitudinal changes in PV parameters. <h3>Results</h3> There were no significant differences in demographics and clinical data between pump speed groups. Linear mixed-effects model was performed to estimate trends in PV parameters. Patients with pump speed of 2400rpm demonstrated significant monthly increase in SW, LVP_max and E_es at 0.05mmHg/L (95%CI 0.02-0.08, p<0.001), 5.64mmHg (95%CI 1.08-10.2, p=0.016) and 0.071mmHg/mL (95%CI 0.002-0.141, p=0.041) per month respectively. The trajectories were significantly different to the patients with higher speeds of 2500rpm and 2600rpm, in whom the PV parameters were largely unchanged across the first 6 months. These findings were consistent after adjusting for baseline cardiovascular risk factors in a covariate-adjusted model. <h3>Conclusion</h3> Our results provide compelling evidence of the impact pump speed has on the longitudinal changes in cardiac chamber function post-LVAD. Randomized studies are required to evaluate the impacts of lowering pump speed as a strategy, to enhance reverse remodelling in suitable patients.

Less Invasive Left Ventricular Assist Device Implantation is Safe and Feasible in Patients with Smaller Body Surface Area

<h3>Purpose</h3> Smaller body surface area (BSA) frequently precludes patients for Left Ventricular Assist Device (LVAD) therapy. We sought to investigate the clinical outcomes in patients with small BSA undergoing less invasive LVAD implantation. <h3>Methods</h3> We conducted a retrospective review of 216 patients implanted with HeartMate 3 LVAD via less invasive surgery (LIS) at our institution. Patients were dichotomized and compared based on their pre-implant BSA: small BSA (BSA≤1.8 m²) and normal/large BSA (BSA>1.8 m²). We analyzed patients' perioperative characteristics and outcomes. <h3>Results</h3> In our study, small BSA was found in 32 (14.8%) patients, while 184 (85.2%) had normal/large BSA (Table 1). Women were more prevalent in the small BSA group (50.0% vs. 13.0%, p<0.001). Preoperative and intraoperative data showed comparable results. Major complications and hospital length of stay did not differ by BSA group. Patients with smaller BSAs had significantly decreased pump parameters at discharge, this includes LVAD flow (4.11±0.49 vs.4.60±0.54, L/min, p<0.001) and pump speed (5200 vs. 5400, rpm, p<0.001). Survival to discharge and within 6 post-implantation months were similar between the groups (Figure 1). <h3>Conclusion</h3> Our study results suggest that less invasive HeartMate 3 implantation can be safely performed and demonstrates equivalent outcomes in patients with smaller body habitus. Randomized trials are required to confirm our data.

Successful Recovery from Refractory Hypoxia Due to Right-to-Left Shunting Associated with Iatrogenic Atrial Septal Defect After Catheter Ablation in a Patient with a Left Ventricular Assist Device

<h3>Introduction</h3> Catheter ablation has been reported an effective therapeutic option for ventricular arrhythmias even in patients with a left ventricular assist device (LVAD). However, the issues of right-to-left shunting due to iatrogenic atrial septal defect (iASD) associated with procedures for catheter ablation have not been well documented. <h3>Case Report</h3> A 52-year-old male with a continuous-flow implantable LVAD and progressive right ventricular (RV) dysfunction was admitted because of refractory ventricular tachycardia (VT) and subsequent right heart failure. Since VT could not be controlled by intravenous administration of multiple antiarrhythmic drugs, VT ablation via the transseptal approach was performed. VT was terminated to the sinus rhythm after VT ablation; however, hypoxia associated with significant right-to-left shunting across the iASD was detected. Intensive medical management, such as an adjusted mechanical ventilator to increase pulmonary vascular resistance and adjustment of LVAD pump speed as well as the use of intravenous inotropes to support impaired RV function successfully stabilised the hemodynamic and improved hypoxia due to the disappearance of right-to-left shunting. <h3>Summary</h3> We described a rare case of refractory hypoxia due to significant right-to-left shunting via iASD after catheter ablation. The present case suggests that pre-existing impaired RV function may be responsible for the development of refractory right-to-left shunting after catheter ablation, and implies that evaluation of RV function prior to VT ablation via the transseptal approach is important in postoperative management in a patient with a LVAD.

An Optimal H-Infinity Controller for Left Ventricular Assist Devices Based on a Starling-like Controller: A Simulation Study

Left ventricular assist devices (LVADs) are emerging innovations that provide a feasible alternative treatment for heart failure (HF) patients to enhance their quality of life. In this work, a novel physiological control system to optimize LVAD pump speed using an H-infinity controller was developed. The controller regulates the calculated target pump flow vs. measured pump flow to meet the changes in metabolic demand. The method proposes the implementation of the Frank–Starling mechanism (FSM) approach to control the speed of an LVAD using the left ventricle end-diastolic volume (Vlved) parameter (preload). An operating point was proposed to move between different control lines within the safe area to achieve the FSM. A proportional–integral (PI) controller was used to control the gradient angle between control lines to obtain the flow target. A lumped parameter model of the cardiovascular system was used to evaluate the proposed method. Exercise and rest scenarios were assessed under multi-physiological conditions of HF patients. Simulation results demonstrated that the control system was stable and feasible under different physiological states of the cardiovascular system (CVS). In addition, the proposed controller was able to keep hemodynamic variables within an acceptable range of the mean pump flow (Qp) (max = 5.2 L/min and min = 3.2 L/min) during test conditions.

The Effects of Pencil Beam Scanning Proton Radiation Therapy on a Left Ventricular Assist Device: Implications for Patient Safety

Heart failure remains a major source of morbidity and mortality worldwide. Left ventricular assist devices (LVADs) provide mechanical circulatory support and offer superior outcomes to medical therapy in patients with end-stage heart failure. LVADs can be used as a bridge to cardiac transplantation but are now more commonly used as destination therapy. While the safety of photon beam and older proton beam therapy (PBT) techniques have been established in patients with LVADs, data evaluating the safety of pencil beam scanning (PBS) PBT techniques are lacking. In this study, we evaluated the dose tolerance of an LVAD to PBS proton irradiation. We hypothesized that proton irradiation would affect the function of the LVAD.We conducted three experiments in which we exposed elements of separate LVADs to a proton beam whose Spread Out Bragg Peak (SOBP) had a range of 100 mm and a width of 60 mm. The LVAD was placed in a water-based phantom with a wall of water-equivalent thickness of 11.59 mm at a depth of 5 cm. In the first experiment, we delivered escalating doses of proton beam radiation to the device pump, starting at 5 GyE and increasing in increments of 5 GyE up to 70 GyE. In replicative second and third experiments, we delivered proton beam radiation continuously to a dose of 70 GyE (prescribed to the middle of the SOBP) to the pump and driveline, respectively. Optical stimulated luminescent dosimeters (OSLDs) were utilized to monitor dose to the battery and controller, which were located outside of the field of radiation. Our institutional review board deemed this study exempt.The pump showed no significant operational changes after irradiation in the first and second experiments. However, during continuous irradiation of the driveline in the third experiment, communication between the pump and monitor was lost at 30 GyE (confirmed on the device's log files). While the pump continued to run during this time, the monitor displayed a low flow alarm. OSLD measurements were 0.02 cGy for the monitor and 0.069 cGy for the battery after the completion of the third experiment. No mechanical damage was noted to the components of the LVAD after any of the three experiments.The pump and driveline of the LVAD exhibited no structural damage after direct irradiation by a proton beam. The pump tolerated escalating doses of up to 70 GyE, which is consistent with prior published data. However, when the driveline was irradiated continuously, the controller and pump lost connection at 30 GyE, and a low flow alarm was generated. These results suggest that while the LVAD pump can tolerate clinically significant doses of PBS PBT, further study is necessary to assess the resilience of the driveline to fractionated PBT.