A contemporary review of mechanical circulatory support

Mechanical Circulatory Support in Cardiogenic Shock: A Narrative Review

Cardiogenic shock (CS) remains a critical condition with high mortality rates, often arising from acute myocardial infarction and advanced heart failure. Despite advancements in medical therapy, traditional interventions frequently fall short of reversing the profound hemodynamic instability seen in CS. Mechanical circulatory support (MCS) devices have emerged as crucial therapeutic options, offering temporary stabilization and bridging to recovery, heart transplantation, or long-term ventricular assist device implantation. This narrative review explores the current landscape of MCS in CS, highlighting the various types of support devices, including intra-aortic balloon pumps (IABP), veno-arterial extracorporeal membrane oxygenation (VA-ECMO), and percutaneous ventricular assist devices (pVADs) such as Impella and TandemHeart. We examine their mechanisms of action, clinical indications, and outcomes alongside the challenges and complications associated with their use. Additionally, we discuss the evolving guidelines and the role of MCS in contemporary CS management, emphasizing the need for timely intervention and a multidisciplinary approach. The review underscores the importance of individualized patient selection and device choice to optimize outcomes in this critically ill population.

Effectiveness of exercise-based cardiac rehabilitation for patients with left ventricular assist device: A systematic review and meta-analysis

PURPOSE

Exercise-based cardiac rehabilitation (EBCR) improves functional capacity in heart failure (HF). However, data on the effect of EBCR in patients with advanced HF and left ventricular assist devices (LVADs) are limited. This meta-analysis aimed to evaluate the impact of EBCR on the functional ability of LVAD patients by comparing the corresponding outcome indicators between the EBCR and ST groups.

METHODS

PubMed, Embase, Clinical Trials, and Cochrane Library databases were searched for studies assessing and comparing the effects of EBCR and standard therapy (ST) in patients following LVAD implantation. Using pre-defined criteria, appropriate studies were identified and selected. Data from selected studies were extracted in a standardized fashion, and a meta-analysis was performed using a fixed-effects model. The protocol was registered on INPLASY (202340073).

RESULTS

In total, 12 trials involving 477 patients were identified. The mean age of the participants was 52.9 years, and 78.6% were male. The initiation of EBCR varied from LVAD implantation during the index hospitalization to 11 months post-LVAD implantation. The median rehabilitation period ranged from 2 weeks to 18 months. EBCR was associated with improved peak oxygen uptake (VO2) in all trials. Quantitative analysis was performed in six randomized studies involving 214 patients (EBCR: n = 130, ST: n = 84). EBCR was associated with a significantly high peak VO2 (weighted mean difference [WMD] = 1.64 mL/kg/min; 95% confidence interval [CI], 0.20-3.08; p = .03). Similarly, 6-min walk distance (6MWD) showed significantly greater improvement in the EBCR group than in the ST group (WMD = 34.54 m; 95% CI, 12.47-56.42; p = .002) in 266 patients (EBCR, n = 140; ST, n = 126). Heterogeneity was low among the included trials. None of the included studies reported serious adverse events related to EBCR, indicating the safety of EBCR after LVAD implantation.

CONCLUSION

This study demonstrated that EBCR following LVAD implantation is associated with greater improvement in functional capacity compared with ST as reflected by the improved peak VO2 and 6MWD values. Considering the small number of patients in this analysis, further research on the clinical impact of EBCR in LVAD patients is warranted.

Anti-infective characteristics of a new Carbothane ventricular assist device driveline

Objectives

Driveline infections are a major complication of ventricular assist device (VAD) therapy. A newly introduced Carbothane driveline has preliminarily demonstrated anti-infective potential against driveline infections. This study aimed to comprehensively assess the anti-biofilm capability of the Carbothane driveline and explore its physicochemical characteristics.

Methods

We assessed the Carbothane driveline against biofilm formation of leading microorganisms causing VAD driveline infections, including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Candida albicans, using novel in vitro biofilm assays mimicking different infection micro-environments. The importance of physicochemical properties of the Carbothane driveline in microorganism-device interactions were analyzed, particularly focusing on the surface chemistry. The role of micro-gaps in driveline tunnels on biofilm migration was also examined.

Results

All organisms were able to attach to the smooth and velour sections of the Carbothane driveline. Early microbial adherence, at least for S. aureus and S. epidermidis, did not proceed to the formation of mature biofilms in a drip-flow biofilm reactor mimicking the driveline exit site environment. The presence of a driveline tunnel however, promoted staphylococcal biofilm formation on the Carbothane driveline. Physicochemical analysis of the Carbothane driveline revealed surface characteristics that may have contributed to its anti-biofilm activity, such as the aliphatic nature of its surface. The presence of micro-gaps in the tunnel facilitated biofilm migration of the studied bacterial species.

Conclusion

This study provides experimental evidence to support the anti-biofilm activity of the Carbothane driveline and uncovered specific physicochemical features that may explain its ability to inhibit biofilm formation.

Ventricular Flow Dynamics with an Intra-Ventricular Balloon Pump: An In Vitro Analysis

Due to the high treatment costs associated with durable ventricular assist devices, an intra-ventricular balloon pump (IVBP) was developed to provide low-cost, short-term support for patients suffering from severe heart failure. It is imperative that intraventricular flow dynamics are evaluated with an IVBP to ensure stagnation points, and potential regions for thrombus formation, are avoided. This study used particle image velocimetry to evaluate flow patterns within the left ventricle of a simulated severe heart failure patient with IVBP support to assess left ventricle pulsatility as an indicator of the likelihood of flow stasis. Two inflation timings were evaluated against the baseline severe heart failure condition: IVBP co-pulsation and IVBP counter-pulsation with respect to ventricular systole. IVBP co-pulsation was found to have a reduced velocity range compared to the severe heart failure condition (0.44 m/s compared to 0.54 m/s). IVBP co-pulsation demonstrated an increase in peak velocities (0.25 m/s directed toward the aortic valve during systole, as opposed to 0.2 m/s in severe heart failure), indicating constructive energy in systole and cardiac output (1.7 L/min increase with respect to severe heart failure baseline - 3.5 L/min) throughout the cardiac cycle. IVBP counter-pulsation, while exhibiting the greatest peak systolic velocity directed to the aortic valve (0.4 m/s) was found to counterasct the natural vortex flow pattern during ventricular filling, as well as inducing a secondary ventricular pulse during diastole and a 23% increase in left ventricle end-diastolic volume (indicative of dilation). Ideal IVBP actuation timing did not result in reduced intraventricular pulsatility, indicating promising blood washout.

Does infection predispose to thrombosis during long term ventricular assist device support?

BACKGROUND

Infections and thrombotic events remain life-threatening complications in patients with ventricular assist devices (VAD).

METHODS

We describe the relationship between both events in our cohort of patients (n=220) supported with the HeartWare VAD (HVAD). This is a retrospective analysis of patients undergoing HVAD implantation between July 2009 and March 2019 at the Freeman Hospital, Newcastle upon Tyne, United Kingdom.

RESULTS

Infection was the most common adverse event in HVAD patients, with 125 patients (56.8%) experiencing ≥ one infection (n=168, 0.33 event-per-person-year-EPPY), followed by pump thrombosis (PT) in 61 patients (27.7%, 0.16 EPPY). VAD-specific infections were the largest group of infections. Of the 125 patients who had an infection, 66 (53%) had a thrombotic event. Both thrombotic events and infections were related to the duration of support, though there was only limited evidence that infections predispose to thrombosis. Those with higher than median levels of CRP during the infection were more likely to have an ischaemic stroke (IS) (34.5% vs 16.7%, p=0.03), though not PT or a combined thrombotic event (CTE: first PT or IS). However, in multivariate analysis there was no significant effect of infection predisposing to CTE.

CONCLUSIONS

Infection and thrombotic events are significant adverse events related to the duration of support in patients receiving HVADs. Infections do not clearly predispose to thrombotic events.

Non-Surgical Resolution of Inflow Cannula Obstruction of a Left Ventricular Assist Device: A Case Report

A 55-year-old woman who had received an implantable left ventricular assist device 3 months earlier presented with dyspnea and a low-flow alarm of the device. Computed tomography and log-file analysis of the device system suggested inflow cannula obstruction. Since the patient had cardiogenic shock due to pump failure, venoarterial extracorporeal membrane oxygenation (ECMO) was initiated. With ECMO, surgical exchange of the pump was considered. However, the obstruction spontaneously resolved without surgical intervention. It turned out that an obstructive thrombus was washed out by rebooting the pump. Moreover, the thrombus was embolized in the patient’s left subclavian artery. The patient underwent heart transplantation 4 months after the pump obstruction accident and continued to do well.

Development of De Novo Aortic Insufficiency in Patients with HeartMate 3

BACKGROUND

De novo aortic insufficiency (AI) is a common adverse event following continuous flow left ventricular assist device (LVAD) placement and is associated with morbidity and mortality. This study aims to compare the development of de novo AI between HeartMate 3 and HeartMate II LVAD recipients.

METHODS

A retrospective review was conducted of clinical characteristics and serial echocardiograms (1 month, 6 months, and 1 year post-implantation) of HeartMate 3 patients implanted between November 2014 and March 2019, and of HeartMate II patients implanted between April 2004 and December 2015 at Columbia University Irving Medical Center. Patients (n=122) were excluded from analysis for a history of aortic valve surgery, concomitant aortic valve surgery with LVAD implant, or more than trace preoperative AI left untreated. De novo AI was defined as development of more than mild AI following LVAD implant.

RESULTS

There were 121 HeartMate 3 patients and 270 HeartMate II patients included in the study. After accounting for competing risks of death and transplantation, there was no significant difference in the development of de novo AI by 1 year post-implantation between HeartMate II and HeartMate 3 patients (p = 0.68). There was no significant difference in severity between HeartMate II and HeartMate 3 among those patients who developed AI up to 1 year post-implantation.

CONCLUSIONS

Development of de novo AI is comparable between HeartMate 3 and HeartMate II patients. There is no significant difference in severity of AI between HM II and HM 3 patients.

Improving Outcome Predictions for Patients Receiving Mechanical Circulatory Support by Optimizing Imputation of Missing Values

BACKGROUND

Risk prediction models play an important role in clinical decision making. When developing risk prediction models, practitioners often impute missing values to the mean. We evaluated the impact of applying other strategies to impute missing values on the prognostic accuracy of downstream risk prediction models, that is, models fitted to the imputed data. A secondary objective was to compare the accuracy of imputation methods based on artificially induced missing values. To complete these objectives, we used data from the Interagency Registry for Mechanically Assisted Circulatory Support.

METHODS

We applied 12 imputation strategies in combination with 2 different modeling strategies for mortality and transplant risk prediction following surgery to receive mechanical circulatory support. Model performance was evaluated using Monte-Carlo cross-validation and measured based on outcomes 6 months following surgery using the scaled Brier score, concordance index, and calibration error. We used Bayesian hierarchical models to compare model performance.

RESULTS

Multiple imputation with random forests emerged as a robust strategy to impute missing values, increasing model concordance by 0.0030 (25th-75th percentile: 0.0008-0.0052) compared with imputation to the mean for mortality risk prediction using a downstream proportional hazards model. The posterior probability that single and multiple imputation using random forests would improve concordance versus mean imputation was 0.464 and >0.999, respectively.

CONCLUSIONS

Selecting an optimal strategy to impute missing values such as random forests and applying multiple imputation can improve the prognostic accuracy of downstream risk prediction models.

Midterm Results of Minimally Invasive Left Thoracotomy Fully Magnetically Levitated Left Ventricular Assist Device Implantation

The aim of the study is to compare outcomes of the patients who underwent HeartMate3 (HM3) implantation with conventional sternotomy (CS) and minimally invasive thoracotomy technique (MILT). From June 2013 to April 2019, 50 patients who underwent isolated HM3 implantation were included. Patients were divided into two groups according to the operative technique; of 50 patients, 28 were implanted with CS and 22 with MILT. All patients were evaluated for mortality, need of inotrope, blood product transfusion, intensive care unit stay, time on mechanical ventilation, and postoperative right ventricular failure. Primary outcomes were early mortality and occurrence of adverse events. Patients characteristics were similar; preoperative central venous pressure (CVP) and the ratio of CVP to pulmonary capillary wedge pressure (CVP/PCWP) were significantly higher in the MILT group versus the CS group (p < 0.05). Intensive care unit stay was significantly shorter in the MILT group (p < 0.05). Incidence of bleeding requiring exploratory sternotomy and postoperative drainage on the first postoperative day were statistically higher in the CS group (p < 0.05). Right ventricular failure was higher in the CS group but was not statistically significant (p = 0.4). There was no significant difference in long-term adverse events. The Kaplan-Meier survival analysis showed no difference between the groups (p = 0.66). The HM3 assist system can be successfully implanted with the MILT technique, which has proved to be safe and reproducible and yields good clinical outcomes.

Future Devices for Percutaneous Mechanical Circulatory Support

Percutaneous mechanical circulatory support options include intra-aortic balloon pump, transvalvular axial flow pumps, left atrial to femoral artery pumping, and oxygenated right atrium to femoral artery circuits. Percutaneous mechanical circulatory support devices providing greater support have not proven superiority over the intra-aortic balloon pump. Novel counterpulsation devices target durability and ambulatory capability and direct unloading of left ventricle (LV) and right ventricle. Device innovations in transvalvular axial pumping include miniaturization of partial-support devices and development of larger self-expanding devices for near-complete LV support. Aortic entrainment pumping is a novel mode of blood displacement with potential benefits beyond reduced LV afterload.

An Integrative Study of Aortic mRNA/miRNA Longitudinal Changes in Long-Term LVAD Support

Studying the long-term impact of continuous-flow left ventricular assist device (CF-LVAD) offers an opportunity for a complex understanding of the pathophysiology of vascular changes in aortic tissue in response to a nonphysiological blood flow pattern. Our study aimed to analyze aortic mRNA/miRNA expression changes in response to long-term LVAD support. Paired aortic samples obtained at the time of LVAD implantation and at the time of heart transplantation were examined for mRNA/miRNA profiling. The number of differentially expressed genes (Pcorr < 0.05) shared between samples before and after LVAD support was 277. The whole miRNome profile revealed 69 differentially expressed miRNAs (Pcorr < 0.05). Gene ontology (GO) analysis identified that LVAD predominantly influenced genes involved in the extracellular matrix and collagen fibril organization. Integrated mRNA/miRNA analysis revealed that potential targets of miRNAs dysregulated in explanted samples are mainly involved in GO biological process terms related to dendritic spine organization, neuron projection organization, and cell junction assembly and organization. We found differentially expressed genes participating in vascular tissue engineering as a consequence of LVAD duration. Changes in aortic miRNA levels demonstrated an effect on molecular processes involved in angiogenesis.

An Analysis of Waitlist Inactivity Among Patients With Ventricular Assist Devices

BACKGROUND

Ventricular assist devices (VADs) are commonly used mechanical circulatory support for bridge to transplant therapy in end-stage heart failure; however, it is not understood how VADs influence incidence of waitlist inactive status. We sought to characterize and compare waitlist inactivity among patients with and without VADs.

METHODS

Using the Organ Procurement and Transplantation Network database, we investigated the VAD's impact on incidence and length of inactive periods for heart transplant candidates from 2005 through 2018. We compared median length of inactivity between patients with and without VADs and investigated inactivity risk with time-to-event regression models.

RESULTS

Among 46,441 heart transplant candidates, 32% (n = 14,636) had a VAD. Thirty-eight percent (n = 17,873) of all patients experienced inactivity, of which 42% (7538/17,873) had a VAD. Median inactivity length was 31 d for patients without VADs and 62 d for VAD patients (P < 0.0005). Multivariable analysis showed no significant difference in risk of inactivity for deteriorating conditions between patients with and without VADs after controlling for demographic and baseline clinical variables. A larger proportion of patients without VADs were inactive for deteriorating conditions than VAD patients (54%, n = 8242/15,221 versus 32%, n = 3583/11,086, P < 0.001). Ten percent (1155/11,086) of VAD patients' inactive periods were for VAD-related complications.

CONCLUSIONS

Although VAD patients were inactive longer and had an overall increased risk of any-cause inactivity, their risk of inactivity for deteriorating condition was not significantly different from patients without VADs. Furthermore, VAD patients had a smaller proportion of inactivity periods due to deteriorating conditions. Thus, VADs are protective from morbidity for waitlist patients.

Evaluating medical device adverse event signals using a likelihood ratio test method

Signal detection methods have been used extensively in post-market surveillance to identify elevated risks of adverse events. However, these statistical methods have not been widely used in detecting AE signals for medical devices. In this paper, we focused on the use of a likelihood ratio test (LRT)-based method in identifying adverse event (AE) signals associated with left ventricular assist devices (LVADs) using Medical Device Reporting (MDR) data. Among 110,927 adverse event entries identified in MDR data for LVADs, the LRT method detected 18 AE signals which included seven bleeding-related AEs such as hemolysis, thrombosis, hematuria, thrombus, blood loss, and hemorrhage. The LRT method was also applied to longitudinal data from 2007 to 2019 where a monotone alpha-spending function was used to ensure the control of type I error at each look and overall for trend analysis. Furthermore, the LRT method was compared to proportional reporting ratios (PRRs), Bayesian confidence propagation neural network (BCPNN), and simplified Bayes methods and found to be the most conservative method when examining the total number of detected signals, given its ability to control type-I error and the false discovery rate.

Incidence of Infection and Antimicrobial Consumption in Ventricular Assist Device (VAD) Recipients at the Prince Charles Hospital (TPCH): A Retrospective Analysis

BACKGROUND

Ventricular assist devices (VADs) are frequently used as a bridge to heart transplant; however, infections are a common cause of increased morbidity and mortality. The optimal prophylactic antimicrobial regimen has not been effectively evaluated in literature.

METHODS

Forty-three (43) patients received a VAD over the 5-year study period (2012-2017) at The Prince Charles Hospital (TPCH), Brisbane Australia. Of these, 41 patients were followed from implantation until transplantation or death. Antimicrobial prophylactic regimens and individual episodes of infection were recorded. The infection profiles, including types and incidence were compared to published literature using definitions from the International Society for Heart and Lung Transplantation (ISHLT) guidelines for consistency.

RESULTS

Median duration of VAD insertion was 79 days (IQR: 36-167). Patients received aztreonam, fluconazole and vancomycin (median duration 8 days). Twenty-two (22) (53.6%) patients experienced a VAD-specific and/or a VAD-related infective episode. Incidence of infection in the study cohort was 0.60 infections per 100 patient days. Thirteen (13) patients (31.7%) experienced 16 VAD-specific infections which were all driveline infections. Thirteen (13) patients (31.7%) experienced 14 VAD-related infections. The predominant VAD-related infection type was bacteraemia (36%). Predominant bacterial profiles of VAD-specific as well as VAD related infections were gram positive. Only three episodes had a gram negative as a causative pathogen which occurred much later post VAD insertion. Median time till VAD-specific or VAD-related infection was 46 and 15 days respectively. Obesity was significantly associated with increased risk of infection (HR: 3.2; 95% CI: 1.3-7.4).

CONCLUSIONS

Infection is a common complication of VAD implantation. In our study population gram positive bacteria were the predominant causative pathogen. Based on the micro-organism profile there may be scope for a narrowing of the antibiotic regimen. A larger, multicentre study would be able to accurately guide a change. The information gathered in our study offers a strong foundation for such a multicentre study.

Initial conservative management strategy of HeartWare left ventricular assist device thrombosis with intravenous heparin or bivalirudin

Introduction and objectives:

Pump thrombosis is a serious left ventricular assist device complication, though there are no guidelines regarding its treatment. The main aim of this study was to describe a strategy of intravenous anticoagulation as the initial treatment in these patients and then to compare intravenous heparin with bivalirudin.

Methods:

All consecutive patients who received a HeartWare left ventricular assist device from July 2009 to March 2019 were retrospectively analysed. Patients developing a pump thrombosis were selected, and treatment, outcomes and complications were recorded.

Results:

During this period of time (116 months), 220 patients underwent HeartWare left ventricular assist device implantation and 57 developed pump thrombosis, with an incidence rate of first pump thrombosis of 0.17 events per patient-year of support (incidence rate of all episodes of pump thrombosis: 0.30 events per patient-year of support). All the patients were initially treated medically, predominantly with either intravenous heparin (n = 26) or bivalirudin (n = 16). Patients treated with bivalirudin during the first pump thrombosis episode had less subsequent re-thrombosis episodes (18.7% vs 57.7%, p < 0.05). In addition, percentage time in therapeutic range was greater for bivalirudin compared with heparin (68.5% ± 16.9% vs 37.4% ± 31.0%, p < 0.01). During the first pump thrombosis episode, 26.3% of the patients needed surgery (left ventricular assist device exchange (n = 8), transplant (n = 6) or decommissioning (n = 1)). The overall survival at 1 year was 61.4%, and there was no significant difference in survival.

Conclusion:

Left ventricular assist device thrombosis is a serious life-threatening complication; hence, we propose an initial conservative management of pump thrombosis with enhanced intravenous anticoagulation with either intravenous heparin or bivalirudin, with surgery reserved for refractory cases.

Clinical implications of LDH isoenzymes in hemolysis and continuous-flow left ventricular assist device-induced thrombosis

Pump-induced thrombosis continues to be a major complication of continuous-flow left ventricular assist devices (CF-LVADs), which increases the risks of thromboembolic stroke, peripheral thromboembolism, reduced pump flow, pump failure, cardiogenic shock, and death. This is confounded by the fact that there is currently no direct measure for a proper diagnosis during pump support. Given the severity of this complication and its required treatment, the ability to accurately differentiate CF-LVAD pump thrombosis from other complications is vital. Hemolysis measured by elevated lactate dehydrogenase (LDH) enzyme levels, when there is clinical suspicion of pump-induced thrombosis, is currently accepted as an important metric used by clinicians for diagnosis; however, LDH is a relatively nonspecific finding. LDH exists as five isoenzymes in the body, each with a unique tissue distribution. CF-LVAD pump thrombosis has been associated with elevated serum LDH-1 and LDH-2, as well as decreased LDH-4 and LDH-5. Herein, we review the various isoenzymes of LDH and their utility in differentiating hemolysis seen in CF-LVAD pump thrombosis from other physiologic and pathologic conditions as reported in the literature.

Nine contemporary therapeutic directions in heart failure

The global burden of heart failure has continued to increase dramatically with 26 million people affected and an estimated health expenditure of $31 billion worldwide. Several practice-influencing studies were reported recently, bringing advances along many frontiers in heart failure, particularly heart failure with reduced ejection fraction. In this article, we discuss nine distinct therapeutic areas that were significantly influenced by this scientific progress. These distinct areas include the emergence of sodium-glucose cotransporter-2 inhibitors, broadening the application of angiotensin-neprilysin inhibition, clinical considerations in therapy withdrawal in those patients with heart failure that 'recover' myocardial function, benefits of low-dose direct oral anticoagulants in sinus rhythm, targeted therapy for treating cardiac amyloidosis, usefulness of mitral valve repair in heart failure, the advent of newer left ventricular assist devices for advanced heart failure, the role of ablation in atrial fibrillation in heart failure, and finally the use of wearable defibrillators to address sudden death.

Outcomes of Acute Inpatient Rehabilitation of Patients With Left Ventricular Assist Devices and Subsequent Stroke

OBJECTIVE

The aim of the study was to examine the functional outcomes and medical complications of patients with left ventricular assist device implantation and subsequent stroke during comprehensive inpatient rehabilitation.

DESIGN

Retrospective cohort study of 21 patients admitted to an inpatient rehabilitation facility between 2009 and 2015. Main outcome measurements include admission and discharge Functional Independence Measure, length of stay, and Functional Independence Measure efficiency.

RESULTS

The study included 17 male and 4 female patients aged 32-75 yrs. Eleven patients (52%) required transfer to an acute care hospital for evaluation. Fifteen patients completed inpatient rehabilitation with median [interquartile range] length of stay 26 [13.5-34] days (range = 7-59 days), median [interquartile range] Functional Independence Measure gain of 18 [12.5-32], and median [interquartile range] Functional Independence Measure efficiency of 1.0 [0.6-1.44]. Patients who required transfer to acute care during their course but ultimately completed inpatient rehabilitation (n = 5) demonstrated larger median [interquartile range] Functional Independence Measure gain (40 [23-42]) and longer median [interquartile range] length of stay (35 [35-42]) compared with patients who completed inpatient rehabilitation without transfer (Functional Independence Measure gain = 15 [9.25-26.5]; length of stay = 14.5 [11.5-26.25]).

CONCLUSIONS

Patients with left ventricular assist device implantation and subsequent stroke demonstrate functional gains during acute inpatient rehabilitation programs. A large percent of patients required transfer to acute care.

Durable Biventricular Support Using Right Atrial Placement of the HeartWare HVAD

Patients with Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) levels 1-2 who either have or are at risk for right ventricular failure face significant morbidity and mortality after continuous flow left ventricular assist device (CF-LVAD) implantation. Currently, the options for biventricular support are limited the Total Artificial Heart (TAH; CardioWest, Syncardia, Tuscon, AZ) or biventricular assist device (BiVAD), which uses bulky extracorporeal or implantable displacement pumps. We describe a successful series based on an innovative approach for biventricular support in consecutive INTERMACS levels 1-2 patients utilizing a HeartWare Ventricular Assist Device (HVAD; HeartWare, Framingham, MA) in a left ventricular (LV-HVAD) and a right atrial (RA-HVAD) configuration. From June 2014 through May 2016, 11 consecutive INTERMACS levels 1-2 patients with evidence of biventricular failure underwent implantation of a CF LVAD (10 LV-HVAD and 1 HeartMate II LVAD, Thoratec, Pleasanton, CA) and RA-HVAD pumps. A total of 4,314 BiVAD support days were accumulated in our case series. Seven patients have undergone orthotopic heart transplant, whereas 3 are ambulatory and are either waiting transplant or reconsideration for transplantation. There is one mortality in this case series, which was due to an intracranial bleed from supratherapeutic anticoagulation. Two other patients experienced hemorrhagic strokes, but without neurologic sequelae, whereas no patients have experienced ischemic strokes. There were two episodes of gastrointestinal bleeding. This is the largest series to date involving this approach with outcomes superior to those previously described in patients receiving biventricular support. We conclude this novel therapy is a viable alternative to current practices in the management of biventricular failure.

Passive Leg Raising After Left Ventricular Assist Device Implantation

Left ventricular assist device (LVAD) implantation is a common procedure in patients with end-stage heart failure. Although optimal fluid management is essential for acceptable postoperative treatment, it is critical to identify which patients will benefit from fluid administration. Passive leg raising (PLR) is a validated dynamic method that predicts fluid responsiveness in patients with heart failure by inducing a transient increase in cardiac preload. We performed a prospective study on 20 consecutive patients who underwent PLR maneuvers after LVAD implantation. Left ventricular assist device flow, end-tidal carbon dioxide, central venous pressure (CVP), and mean arterial pressure (MAP) were measured before and after PLR. Passive leg raising responsiveness was defined as at least a 15% increase in LVAD flow: (11 were responders and 9 nonresponders). Of the responders, 7 had right ventricular dysfunction (≥3). Passive leg raising responsiveness was associated with an increase of 19% in the LVAD flow, the mean CVP was raised from 11.3 to 14.4 mm Hg and the MAP from 82.6 to 86.7 mm Hg. After PLR, end-tidal carbon dioxide was increased by 4.6 mm Hg in the responders and 1.1 mm Hg in the nonresponders. The PLR maneuver is a noninvasive and easy to perform method that uses LVAD flow to assess fluid responsiveness in patients with heart failure after LVAD implantation.

Antithrombotic therapy in ventricular assist device (VAD) management: From ancient beliefs to updated evidence. A narrative review

Platelets play a key role in the pathogenesis of ventricular assist device (VAD) thrombosis; therefore, antiplatelet drugs are essential, both in the acute phase and in the long-term follow-up in VAD management. Aspirin is the most used agent and still remains the first-choice drug for lifelong administration after VAD implantation. Anticoagulant drugs are usually recommended, but with a wide range of efficacy targets. Dual antiplatelet therapy, targeting more than one pathway of platelet activation, has been used for patients developing a thrombotic event, despite an increased risk of bleeding complications. Although different strategies have been attempted, bleeding and thrombotic events remain frequent and there are no uniform strategies adopted for pharmacological management in the short and mid- or long-term follow up. The aim of this article is to provide an overview of the evidence from randomized clinical trials and observational studies with a focus on the pathophysiologic mechanisms underlying bleeding and thrombosis in VAD patients and the best antithrombotic regimens available.

Advanced Heart Failure Therapies and Cardiorenal Syndrome

Heart failure (HF) is extremely prevalent and for those with end-stage (stage D) disease, 1-year survival is only 25-50%. Several studies have captured the mortality impact of kidney disease on patients with HF, and measures of kidney function are a component of many HF risk stratification scores. The management of advanced HF complicated by cardiorenal syndrome (CRS) is challenging, and irreversible kidney failure often limits patient candidacy for advanced HF therapies, such as transplant or left ventricular assist device therapy. Thus, prompt institution of aggressive therapy is warranted in stage D HF patients with CRS to prevent irreversible kidney failure. In this chapter, we discuss the assessment and management of patients with CRS with end-stage HF. In addition to discussing medical therapy aimed at decongestion and increased cardiac inotropy, we provide a summary of temporary circulatory support devices that can be considered for those whom hospice is not desired. In all circumstances, a close collaboration between the advanced HF specialist and nephrologist is needed to achieve the best patient outcomes.

Does a Comprehensive Inpatient Rehabilitation Program Improve Patients' and Caregivers' Emotional State in LVAD Patients?

Few studies evaluated the effect of cardiac rehabilitation programs on perceived emotional and health status of left ventricular assist device (LVAD) patients, and none explored their effect on caregivers' strain. We enrolled 119 adult LVAD patients, together with their caregivers (n = 91), in two Rehabilitation Institutes that provided inpatient multidisciplinary activities. At admittance and prior to discharge they completed questionnaires evaluating patient emotional state and subjective perception of health status, caregiver strain, and patient and caregiver perception of the VAD. Six months after discharge, patients and caregivers were contacted again and asked specific questions about their quality of life. Patients' state anxiety and depression symptoms significantly diminished at discharge (0.000), whereas their perception of general health status rose (0.000). Caregivers' perceived strain also significantly decreased (0.001) and the perceived device management skill grew both for patients and caregivers (0.000). A substantial amount (36%) of psychologically frail patients and caregivers, although improving their emotional condition, never reached that of the less frail subjects. At the 6-month follow-up, both patients and caregivers appeared stable in evaluating respectively their general health and their caregiving-related strain, compared to discharge. Our data show that a comprehensive inpatient rehabilitation program improves the emotional state of LVAD patients and of their caregivers, even in psychologically frailer subjects. Team approach makes patients and caregivers self-confident about device management, increasing their knowledge, clarifying their doubts, and encouraging them to handle the difficulties met during the rehabilitation period, suggesting strategies to cope with daily life at home.

Hybrid Continuous-Flow Total Artificial Heart

Clinical studies using total artificial hearts (TAHs) have demonstrated that pediatric and adult patients derive quality-of-life benefits from this form of therapy. Two clinically-approved TAHs and other pumps under development, however, have design challenges and limitations, including thromboembolic events, neurologic impairment, infection risk due to large size and percutaneous drivelines, and lack of ambulation, to name a few. To address these limitations, we are developing a hybrid-design, continuous-flow, implantable or extracorporeal, magnetically-levitated TAH for pediatric and adult patients with heart failure. This TAH has only two moving parts: an axial impeller for the pulmonary circulation and a centrifugal impeller for the systemic circulation. This device will utilize the latest generation of magnetic bearing technology. Initial geometries were established using pump design equations, and computational modeling provided insight into pump performance. The designs were the basis for prototype manufacturing and hydraulic testing. The study results demonstrate that the TAH is capable of delivering target blood flow rates of 1-6.5 L/min with pressure rises of 1-92 mm Hg for the pulmonary circulation and 24-150 mm Hg for the systemic circulation at 1500-10 000 rpm. This initial design of the TAH was successful and serves as the foundation to continue its development as a novel, more compact, nonthrombogenic, and effective therapeutic alternative for infants, children, adolescents, and adults with heart failure.

More than 20 years' experience of left ventricular assist device implantation at a non-transplant Centre

OBJECTIVES

Over recent decades implantable left ventricular assist devices (LVAD) have increased the possibility of improved survival in patients with advanced heart failure who also benefit from a better quality of life. The aim of this retrospective survey was to review the clinical results of LVAD implantation at a low-volume non-transplant centre (Linköping, Sweden) between 1993 and 2016. Our aim was also to assess the mortality and morbidity rates associated with implantation of three LVAD versions at our centre, and to compare our results with those from transplant centres.

DESIGN

A retrospective cohort study was performed examining the medical records of patients who had a HeartMate^® (HMI, HMII, HMIII) LVAD implanted as a bridge to heart transplantation (BTT) or as destination therapy (DT) at the University Hospital, Linköping.

RESULTS

Our main finding was a survival to heart transplantation rate of 82% among our BTT LVAD patients. The most common adverse event among our patients was infection. A higher frequency of temporary dialysis was seen in the HMII group compared to the HMI group, and the frequency of right ventricular failure was higher in our HMII material.

CONCLUSIONS

Our data suggests that patients requiring long-term LVAD support can safely have their device implanted and cared for at a non-transplant centre.

Selection of Patients for Initial Clinical Trials of Solid Organ Xenotransplantation

Several groups have reported extended survival of genetically engineered pig organs in nonhuman primates, varying from almost 10 months for life-supporting kidney grafts and more than 2 years for non-life-supporting heart grafts to less than 1 month for life-supporting liver and lung grafts. We have attempted to define groups of patients who may not have an option to wait for an allograft. These include kidney, heart, and lung candidates who are highly-allosensitized. In addition, some kidney candidates (who have previously lost at least 2 allografts from rapid recurrence of native kidney disease) have a high risk of further recurrence and will not be offered a repeat allotransplant. Patients with complex congenital heart disease, who may have undergone previous palliative surgical procedures, may be unsuitable for ventricular assist device implantation. Patients dying of fulminant hepatic failure, for whom no alternative therapy is available, may be candidates for a pig liver, even if only as a bridge until an allograft becomes available. When the results of pig organ xenotransplantation in nonhuman primates suggest a realistic potential for success of a pilot clinical trial, highly selected patients should be offered participation.

Short-term Results of Heartmate 3 Ventricular Assist Device Implantation for End-Stage Heart Failure

OBJECTIVE

To report our initial experience with Heartmate 3 ventricular assist device (HM3) in cases with end-stage heart failure (ESHF).

METHODS

Charts of 8 ESHF patients who underwent HM3 implantation in our clinic from January to June 2016 (group 1) and 16 patients who underwent HM2 implantation during 2015 (group 2) were reviewed retrospectively. Demographics as well as pre- and early postoperative medical data were noted and statistically analyzed between the 2 groups.

RESULTS

No statistical difference was found in age or sex distribution between groups (P > .05). Mean Interagency Registry for Mechanically Assisted Circulatory Support scores were 2.13 ± 0.99 and 3.38 ± 0.72 in groups 1 and 2, respectively (P = .020). Mean cardiopulmonary bypass time, and chest tube drainage fluid volume and blood product requirement during intensive care unit (ICU) stay were 64.0 ± 13.9 minutes, 1,112.5 ± 516.7 mL, and 318.8 ± 271.2 mL, respectively, in group 1 and 89.0 ± 33.3 minutes, 2,081.3 ± 1,696.0 mL, and 1,118.8 ± 1,010.8 mL in group 2 (P = .027, P = .019, and P = .040, respectively). Need for surgical revision and early mortality were not evident for group 1, although 4 cases (25.0%) required revision surgery, and early mortality was seen in 3 cases (18.8%) in group 2 (P = .121 and P = .190, respectively). Mean durations of ICU stay and total postoperative hospitalization were 5.9 ± 2.0 and 18.3 ± 5.5 days, respectively in group 1 and 6.2 ± 4.3 and 18.0 ± 6.9 days in the surviving 13 patients of the group 2 (P = .645 and P = .697, respectively).

CONCLUSIONS

With its shorter implantation time and reduced blood product requirement in the early postoperative period, the HM3 system was found to be safe and effective in ESHF treatment.

A Fully Magnetically Levitated Circulatory Pump for Advanced Heart Failure

BACKGROUND

Continuous-flow left ventricular assist systems increase the rate of survival among patients with advanced heart failure but are associated with the development of pump thrombosis. We investigated the effects of a new magnetically levitated centrifugal continuous-flow pump that was engineered to avert thrombosis.

METHODS

We randomly assigned patients with advanced heart failure to receive either the new centrifugal continuous-flow pump or a commercially available axial continuous-flow pump. Patients could be enrolled irrespective of the intended goal of pump support (bridge to transplantation or destination therapy). The primary end point was a composite of survival free of disabling stroke (with disabling stroke indicated by a modified Rankin score >3; scores range from 0 to 6, with higher scores indicating more severe disability) or survival free of reoperation to replace or remove the device at 6 months after implantation. The trial was powered for noninferiority testing of the primary end point (noninferiority margin, -10 percentage points).

RESULTS

Of 294 patients, 152 were assigned to the centrifugal-flow pump group and 142 to the axial-flow pump group. In the intention-to-treat population, the primary end point occurred in 131 patients (86.2%) in the centrifugal-flow pump group and in 109 (76.8%) in the axial-flow pump group (absolute difference, 9.4 percentage points; 95% lower confidence boundary, -2.1 [P<0.001 for noninferiority]; hazard ratio, 0.55; 95% confidence interval [CI], 0.32 to 0.95 [two-tailed P=0.04 for superiority]). There were no significant between-group differences in the rates of death or disabling stroke, but reoperation for pump malfunction was less frequent in the centrifugal-flow pump group than in the axial-flow pump group (1 [0.7%] vs. 11 [7.7%]; hazard ratio, 0.08; 95% CI, 0.01 to 0.60; P=0.002). Suspected or confirmed pump thrombosis occurred in no patients in the centrifugal-flow pump group and in 14 patients (10.1%) in the axial-flow pump group.

CONCLUSIONS

Among patients with advanced heart failure, implantation of a fully magnetically levitated centrifugal-flow pump was associated with better outcomes at 6 months than was implantation of an axial-flow pump, primarily because of the lower rate of reoperation for pump malfunction. (Funded by St. Jude Medical; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755 .).

Challenges faced in long term ventricular assist device support

INTRODUCTION

The development of ventricular assist device (VAD) has been one of the revolutionary advancements in end-stage heart failure management. Although the device has developed and improved significantly over the last few decades, we still face multiple challenges.

AREAS COVERED

This review will discuss quality of life, survival, and clinically encountered complications in patients with VAD support. The literature was extensively reviewed for studies describing the above topic area. We describe the impact of major challenges faced in VAD support and discuss their future and expectations. Expert commentary: The technological advancement of VADs has contributed to major improvement of overall survival, enhancement of quality of life and decrease of incidence of complications. It is expected that technologies will continue to evolve. At the same time, the indications for and timing of device implantation, and selection of device type are continuously important in clinical practice setting.

Variability in Physical Activity Assessed with Accelerometer Is an Independent Predictor of Mortality in CHF Patients

Aims

Patients with heart failure often display a distinct pattern of walking characterized by short step-length and frequent short pauses. In the current study we sought to explore if qualitative aspects of movement have any additive value to established factors to predict all-cause mortality in patients with advanced heart failure.

Methods and results

60 patients with advanced heart failure (NYHA III, peak VO2 <20 ml/kg and LVEF <35%) underwent symptom-limited CPX, echocardiography and routine chemistry. Physical activity was assessed using an accelerometer worn attached to the waist during waking hours for 7 consecutive days. The heart-failure survival score (HFSS) was calculated for each patient. All accelerometer-derived variables were analyzed with regard to all-cause mortality and added to a baseline model utilizing HFSS scores. HFSS score was significantly associated with the incidence of death (P<0.001; c-index 0.71; CI, 0.67–0.73). The addition of peak skewness to the HFSS model significantly improved the predictive ability with an increase in c-index to 0.74 (CI, 0.69–0.78), likelihood ratio P<0.02, establishing skewness as a predictor of increased event rates when accounting for baseline risk.

Conclusion

The feature skewness, a measure of asymmetry in the intensity level of periods of high physical activity, was identified to be predictive of all-cause mortality independent of the established prognostic model–HFSS and peak VO2. The findings from the present study emphasize the use of accelerometer analysis in clinical practice to make more accurate prognoses in addition to extract features of physical activity relevant to functional classification.

Protein kinase G signaling in cardiac pathophysiology: Impact of proteomics on clinical trials

The protective role of cyclic guanosine monophosphate (cGMP)-stimulated protein kinase G (PKG) in the heart makes it an attractive target for therapeutic drug development to treat a variety of cardiac diseases. Phosphodiesterases degrade cGMP, thus phosphodiesterase inhibitors that can increase PKG are of translational interest and the subject of ongoing human trials. PKG signaling is complex, however, and understanding its downstream phosphorylation targets and upstream regulation are necessary steps toward safe and efficacious drug development. Proteomic technologies have paved the way for assays that allow us to peer broadly into signaling minutia, including protein quantity changes and phosphorylation events. However, there are persistent challenges to the proteomic study of PKG, such as the impact of the expression of different PKG isoforms, changes in its localization within the cell, and alterations caused by oxidative stress. PKG signaling is also dependent upon sex and potentially the genetic and epigenetic background of the individual. Thus, the rigorous application of proteomics to the field will be necessary to address how these effectors can alter PKG signaling and interfere with pharmacological interventions. This review will summarize PKG signaling, how it is being targeted clinically, and the proteomic challenges and techniques that are being used to study it.

Fibrous scaffolds for building hearts and heart parts

Extracellular matrix (ECM) structure and biochemistry provide cell-instructive cues that promote and regulate tissue growth, function, and repair. From a structural perspective, the ECM is a scaffold that guides the self-assembly of cells into distinct functional tissues. The ECM promotes the interaction between individual cells and between different cell types, and increases the strength and resilience of the tissue in mechanically dynamic environments. From a biochemical perspective, factors regulating cell-ECM adhesion have been described and diverse aspects of cell-ECM interactions in health and disease continue to be clarified. Natural ECMs therefore provide excellent design rules for tissue engineering scaffolds. The design of regenerative three-dimensional (3D) engineered scaffolds is informed by the target ECM structure, chemistry, and mechanics, to encourage cell infiltration and tissue genesis. This can be achieved using nanofibrous scaffolds composed of polymers that simultaneously recapitulate 3D ECM architecture, high-fidelity nanoscale topography, and bio-activity. Their high porosity, structural anisotropy, and bio-activity present unique advantages for engineering 3D anisotropic tissues. Here, we use the heart as a case study and examine the potential of ECM-inspired nanofibrous scaffolds for cardiac tissue engineering. We asked: Do we know enough to build a heart? To answer this question, we tabulated structural and functional properties of myocardial and valvular tissues for use as design criteria, reviewed nanofiber manufacturing platforms and assessed their capabilities to produce scaffolds that meet our design criteria. Our knowledge of the anatomy and physiology of the heart, as well as our ability to create synthetic ECM scaffolds have advanced to the point that valve replacement with nanofibrous scaffolds may be achieved in the short term, while myocardial repair requires further study in vitro and in vivo.

A review of infections in patients with left ventricular assist devices: prevention, diagnosis and management

Since the advent of ventricular assist devices with smaller configurations and continuous-flow technology, survival rates for patients with end-stage heart failure have dramatically improved. While the burden of infectious complications is decreased in patients on continuous-flow ventricular assist devices compared to bulkier pulsatile-flow devices, infection remains one of the most common causes of morbidity and mortality. The majority of infections occur at the driveline exit site, beginning with a disruption or trauma to the barrier between the skin and driveline and sometimes spreading deeper. Once infections develop, they can be difficult to eradicate. Depending on the degree of infection, treatment options may include local wound care, antibiotics, or surgical treatment. Preventive strategies and careful surveillance are crucial to improve patient outcomes.

Left ventricular assist device implantation strategies and outcomes

Over the past 15 years, the field of mechanical circulatory support has developed significantly. Currently, there are a multitude of options for both short and long term cardiac support. Choosing the appropriate device for each patient depends on the amount of support needed and the goals of care. This article focuses on long term, implantable devices for both bridge to transplantation and destination therapy indications. Implantation strategies, including the appropriate concomitant surgeries are discussed as well as expected long term outcomes. As device technology continues to improve, long term mechanical circulatory support may become a viable alternative to transplantation.