Right Heart Dysfunction After Left Ventricular Assist Device Implantation: A Comparison of the Pulsatile HeartMate I and Axial-Flow HeartMate II Devices

Successful echocardiography-guided medical management of severe early post-implant right ventricular failure in a patient with left ventricular assist device support: a case report

BACKGROUND

Post-implant right heart failure (RHF) has been recognized as a crucial prognostic factor in patients receiving left ventricular assist devices (LVADs), and its management has long attracted attention from cardiologists and surgeons.

CASE PRESENTATION

This report described an 18-year-old female with acutely deteriorating heart failure due to dilated cardiomyopathy who underwent paracorporeal pulsatile-flow LVAD and developed early post-implant RHF. At postoperative day (POD) six, she was almost asymptomatic at rest on 2.5 mg/kg/min of dobutamine; however, the echocardiogram, performed as part of the daily postoperative care, revealed a severely enlarged right ventricle with a decompressed left ventricle, implying the development of post-implant RHF. Bolus infusion of saline and reduction of pump flow (6.0 L/min to 3.0 L/min) led to normalization of both ventricular shapes in 30 s, suggesting that RHF could be managed without surgical interventions. Milrinone was started on POD six, followed by sildenafil administration on POD seven. Fluid balance was strictly adjusted under the close observation of daily echocardiograms. Milrinone and dobutamine were discontinued on PODs 18 and 21, respectively. The patient was listed for a heart transplant on POD 40. Despite reduced right ventricular function (right ventricular stroke work index of 182.34 mmHg*ml/m- 2, body surface area 1.5 m2), she was successfully converted to implantable LVAD on POD 44 with no recurrence of post-implant RHF thereafter for four years.

CONCLUSIONS

In post-implant RHF management, early detection, together with proper and prompt medical management, is crucial to avoiding any surgical intervention. Close observation of daily echocardiograms might be helpful in detecting subclinical RHF and is useful for post-implant medical management.

Preoperative Pulmonary Artery-to-Aorta Diameter Ratio as a Predictor of Postoperative Severe Right Ventricular Failure and 1-Year Mortality After Left Ventricular Assist Device Implantation

OBJECTIVES

To evaluate the association of pulmonary artery diameter and pulmonary artery- to-aorta diameter ratio (PA/Ao) with right ventricular failure and mortality within 1 year after left ventricular assist device implantation.

DESIGN

This was a retrospective observational study between March 2013 and July 2019.

SETTING

The study was conducted at a single, quaternary-care academic center.

PARTICIPANTS

Adults (≥18 years old) receiving a durable left ventricular assist device (LVAD). Inclusion if (1) a chest computed tomography scan was performed within 30 days before the LVAD and (2) a right and left heart catheterization was completed within 30 days before the LVAD.

INTERVENTIONS

A left ventricular assist device was used for intervention.

MEASUREMENTS AND MAIN RESULTS

A total of 176 patients were included in this study. Median PA diameter and PA/Ao ratio were significantly greater in the severe right ventricular failure (RVF) group (p = 0.001, p < 0.001, respectively). Receiver operating characteristic analysis revealed PA/Ao and RVF as predictors for mortality (area under the curve = 0.725 and 0.933, respectively). Logistic regression analysis-predicted probability gave a PA/Ao ratio cutoff point of 1.04 (p < 0.001). Survival probability was significantly worse in patients with a PA/Ao ratio ≥1.04 (p = 0.005).

CONCLUSIONS

The PA/Ao ratio is an easily measurable noninvasive indicator that can predict RVF and 1-year mortality after LVAD implantation.

Right Ventricular Global Longitudinal Strain as a Predictor of Acute and Early Right Heart Failure Post Left Ventricular Assist Device Implantation

Early right heart failure (RHF) occurs in up to 40% of patients following left ventricular assist device (LVAD) implantation and is associated with increased morbidity and mortality. The most recent report from the Mechanical Circulatory Support-Academic Research Consortium (MCS-ARC) working group subdivides early RHF into early acute RHF and early postimplant RHF. We sought to determine the effectiveness of right ventricular (RV) longitudinal strain (LS) in predicting RHF according to the new MCS-ARC definition. We retrospectively analyzed clinical and echocardiographic data of patients who underwent LVAD implantation between 2015 and 2018. RVLS in the 4-chamber (4ch), RV outflow tract, and subcostal views were measured on pre-LVAD echocardiograms. Fifty-five patients were included in this study. Six patients (11%) suffered early acute RHF, requiring concomitant RVAD implantation intraoperatively. Twenty-two patients (40%) had postimplant RHF. RVLS was significantly reduced in patients who developed early acute and postimplant RHF. At a cutoff of -9.7%, 4ch RVLS had a sensitivity of 88.9% and a specificity of 77.8% for predicting RHF and area under the receiver operating characteristic curve of 0.86 (95% confidence interval 0.76-0.97). Echocardiographic RV strain outperformed more invasive hemodynamic measures and clinical parameters in predicting RHF.

HeartWare HVAD Flow Estimator Accuracy for Left and Right Ventricular Support

This study investigated the accuracy of the HeartWare HVAD flow estimator for left ventricular assist device (LVAD) support and biventricular assist device (BiVAD) support for modes of reduced speed (BiVAD-RS) and banded outflow (BiVAD-B). The HVAD flow estimator was evaluated in a mock circulatory loop under changes in systemic and pulmonary vascular resistance, heart rate, central venous pressure, and simulated hematocrit (correlated to viscosity). A difference was found between mean estimated and mean measured flow for LVAD (0.1 ± 0.3 L/min), BiVAD-RS (-0.1 ± 0.2 L/min), and BiVAD-B (0 ± 0.2 L/min). Analysis of the flow waveform pulsatility showed good correlation for LVAD (r2 = 0.98) with a modest spread in error (0.7 ± 0.1 L/min), while BiVAD-RS and BiVAD-B showed similar spread in error (0.7 ± 0.3 and 0.7 ± 0.2 L/min, respectively), with much lower correlation (r2 = 0.85 and r2 = 0.60, respectively). This study demonstrated that the mean flow error of the HVAD flow estimator is similar when the device is used in LVAD, BiVAD-RS, or BiVAD-B configuration. However, the instantaneous flow waveform should be interpreted with caution, particularly in the cases of BiVAD support.

Perioperative Right Ventricular Dysfunction: Analysis of Outcomes

Right ventricular dysfunction (RVD) is a well-known prognostic factor for adverse outcomes in cardiovascular medicine. The right ventricle (RV) in medically managed heart failure patients and in surgical patients perioperatively generally is overshadowed by left ventricular disease. However, with advancement of various diagnostic tools and better understanding of its functional anatomy, the role of the RV is emerging in many clinical conditions. The failure of one ventricle has significant effect on the function of the other ventricle and it is predominantly due to ventricular interdependence.¹ The etiology of RVD is multifactorial and irrespective of etiology. RVD has been associated with significant increases in morbidity and mortality in various clinical scenarios.^2,3 The primary objective of this comprehensive review is to analyze various etiology-related outcomes of RVD in the perioperative population.

Right Ventricular Strain to Assess Early Right Heart Failure in the Left Ventricular Assist Device Candidate

PURPOSE OF REVIEW

Right heart failure (RHF) following left ventricular assist device implantation (LVAD) remains the primary cause of postoperative mortality and morbidity, and prediction of RHF is the main interest of the transplantation community. In this review, we outline the role and impact of right ventricular strain in the evaluation of the right ventricle function before LVAD implantation.

RECENT FINDINGS

Accumulating data suggest that measurement of right ventricular longitudinal strain (RVLS) has a critical role in predicting RHF preoperatively and may improve morbidity and mortality following LVAD implantation. However, the significant intraobserver, interobserver variability, the lack of multicenter, prospective studies, and the need for a learning curve remain the most critical limitations in the clinical practice at present. This review highlighted the importance of right ventricular strain in the diagnosis of RHF preoperatively and revealed that RVLS might have a crucial clinical measurement for the selection and management of LVAD patients in the future with the more extensive multicenter studies.

Off-label use of pulmonary vasodilators after left ventricular assist device implantation: Calling in the evidence

Left ventricular assist devices (LVAD) are increasingly implanted in advanced heart failure patients to improve survival and quality of life either as a bridge to transplant, bridge to recovery or as destination therapy. LVAD therapy is often accompanied by a profound lowering of pulmonary artery pressure due to mechanical unloading of the left ventricle. Persistent pulmonary hypertension (PH) after LVAD implantation increases the risk of right ventricular failure (RVF). In this context pulmonary vasodilators have been implemented: a) as a strategy to reduce afterload and wean patients with RVF from inotropes in the early postoperative period, b) as long-term therapy aiming to optimize right heart hemodynamics and prevent late RVF and c) in order to lower persistently elevated pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) after LVAD and enable candidacy for heart transplantation. However, considerable uncertainty exists regarding the risks and benefits of these strategies and practices vary widely among institutions. This article provides an overview of the available evidence and existing recommendations regarding the use of pulmonary vasodilators in LVAD recipients.

Effect of left ventricular assist device implantation on right ventricular function: Assessment based on right ventricular pressure-volume curves

Right ventricular (RV) failure is significantly associated with morbidity and mortality after left ventricular assist device (LVAD) implantation. However, it remains unclear whether LVAD implantation could worsen RV function. Therefore, we aimed to investigate the effect of LVAD implantation on RV function by comparing RV energetics derived from the RV pressure-volume curve between before and after LVAD implantation. This exploratory observational study was performed between September 2016 and January 2018 at a national center in Japan. Twenty-two patients who underwent LVAD implantation were included in the analysis. We measured RV energetics parameters: RV stroke work index (RVSWI), which was calculated by integrating the area within the RV pressure-volume curve; RV minute work index (RVMWI), which was calculated as RVSWI × heart rate; and right ventriculo-arterial coupling, which was estimated as RV stroke volume/RV end-systolic volume. We compared RV energetics between before and after LVAD implantation. Although RVSWI was similar [424.4 mm Hg · mL/m² (269.5-510.3) vs. 379.9 mm Hg · mL/m² (313.1-608.8), P = 0.485], RVMWI was significantly higher after LVAD implantation [29 834.1 mm Hg · mL/m² /min (18 272.2-36 357.1) vs. 38 544.8 mm Hg · mL/m² /min (29 016.0-57 282.8), P = 0.001], corresponding to a significantly higher cardiac index [2.0 L/min/m² (1.4-2.2) vs. 3.7 L/min/m² (3.3-4.1), P < 0.001] to match LVAD flow. Right ventriculo-arterial coupling was significantly higher after LVAD implantation [0.360 (0.224-0.506) vs. 0.480 (0.343-0.669), P = 0.025], suggesting that the efficiency of RV performance improved. In conclusion, higher RVMWI with higher cardiac index to match LVAD flow and improved efficiency of RV performance indicate that LVAD implantation might not worsen RV function.

Pulmonary hypertension in HFpEF and HFrEF: Pathophysiology, diagnosis, treatment approaches

Pulmonary hypertension (PH) is a frequent hemodynamic condition that is highly prevalent in patients with heart failure and reduced (HFrEF) or preserved ejection fraction (HFpEF). Irrespective of left ventricular EF, the presence of PH and right ventricular (RV) dysfunction are highly relevant for morbidity and mortality in patients with heart failure. While elevated left-sided filling pressures and functional mitral regurgitation primarily lead to post-capillary PH, current guidelines and recommendations distinguish between isolated post-capillary PH (IpcPH) and combined post- and pre-capillary PH (CpcPH), the latter being defined by a pulmonary vascular resistance (PVR) of ≥3 Wood units. Here, we describe the pathophysiology and clinical relevance of these distinct entities, and report on the diagnostic work-up including remote pulmonary artery pressure (PAP) monitoring. Furthermore, we highlight strategies to manage PH and improve RV function in heart failure, which may include optimized management of HFrEF and HFpEF (medical and interventional), sufficient volume control, catheter-based mitral valve repair, and-in selected cases-targeted PH therapy. In this context, we also highlight gaps in evidence and the need for further research.

Right Heart Failure in Different Left Ventricular Assist Devices: Single-Center Experience

Background: Right heart failure (RHF) following left ventricular assist device (LVAD) implantation increases morbidity and mortality for those who develop this complication. The purpose of this study was to assess the differences in incidence of RHF and outcomes between 2 types of continuous-flow LVADs at a single center. Methods: From January 2012 through June 2016, 184 patients were implanted with a continuous-flow LVAD (161 patients with the HeartMate II and 23 patients with the HeartWare device) either as a bridge to transplant or as destination therapy. Preoperative demographics, medical history, laboratory values, hemodynamics, and device type were analyzed to determine the variables associated with RHF and mortality. Results: Preoperative variables between the 2 groups were homogeneous. Most patients were Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2 (92%) and New York Heart Association class IV (81%). More patients in the HeartMate II group had the indication of destination therapy (54% vs 30%), while more patients in the HeartWare group were implanted as bridge to transplant (70% vs 46%). RHF occurred in 57% of HeartWare patients compared to 16% of patients who received the HeartMate II (P=0.0001). After propensity score analysis, patients receiving the HeartWare device had increased odds for RHF (P=0.0013) and renal failure requiring dialysis (P=0.0135). The HeartMate II patient survival rate exceeded the HeartWare patient survival rate at 1 year (82.1% vs 67.2%) and at 2 years (74.6% vs 61.7%), but this difference did not achieve statistical significance (log-rank P=0.087). Conclusion: These results indicate that device type may affect RHF incidence and mortality. Studies at other centers are needed to replicate these findings.

Mechanical circulatory support for the right ventricle in combination with a left ventricular assist device

Introduction: Right heart failure (RHF) in patients with a left ventricular assist device (LVAD) carries a poor prognosis although the treatment strategy including mechanical circulatory support for the failing right ventricle (RV) has not been well established. Areas covered: In this review, we describe an overview of RHF post-LVAD implant including natural history, prevalence, pathophysiology, outcomes, and challenges to predict RHF post-LVAD implant. Then, we focus on right ventricular assist devices (RVADs) and their clinical outcomes. Recently developed percutaneous RVADs are the major advance in this field. Finally, we discuss future perspectives to overcome limitations of the current treatment options. Expert opinion: In the absence of dedicated RVAD system RHF post-LVAD implant may have been undertreated. Now that dedicated percutaneous RVADs have emerged, surgeons are encouraged to use these new devices to improve outcomes of LVAD therapy. As experience accumulates, we should be able to establish the best possible strategy to treat early RHF post-LVAD implant. Late RHF is another form of RHF post-LVAD implant and has been underappreciated. Further research is mandatory to clarify the mechanism and risk factors. There are still unmet needs for a dedicated implantable RVAD for a subset of patients who need long-term RV support.

Quantification of interventricular dyssynchrony during continuous-flow left ventricular assist device support

Under continuous-flow left ventricular assist device (CF-LVAD) support, the ventricular volume change and cardiac cycle between the left ventricle (LV) and right ventricle (RV) become dyssynchronous due to the shortening of the LV systole. The purpose of this study was to quantify interventricular dyssynchrony based on different CF-LVAD support conditions and assess its relationship with LV unloading. In this study, we evaluated seven goats (body weight 44.5 ± 6.5 kg) with normal hearts. A centrifugal LVAD was implanted under general anesthesia. We inserted the conductance catheters into the left ventricle (LV) and right ventricle (RV) to assess the volume signal simultaneously. We defined the interventricular dyssynchrony as a signal (increase or decrease) of LV volume (LVV) change opposite to that of RV volume (RVV) (i.e., (dLVV/dt) × (dRVV/dt) < 0). The duration of interventricular dyssynchrony (DYS) was reported as the percentage of time that a heart was in a dyssynchronous state within a cardiac cycle. The mean DYS of normal hearts, hearts with LVAD clamp and hearts supported by LVADs with a bypass rate of 50%, 75% and 100% were 5.6 ± 1.6%, 8.7 ± 2.4%, 8.6 ± 2.8%, 15.1 ± 5.1%, and 25.6 ± 8.0%, respectively. Furthermore, the DYS was found to be associated with the degree of LV stroke volume reduction caused by LV unloading. These findings may be useful for understanding interventricular interactions and physiology during CF-LVAD support. Influences on the right ventricular function and heart failure models warrant further study.

Intersection of Pulmonary Hypertension and Right Ventricular Dysfunction in Patients on Left Ventricular Assist Device Support: Is There a Role for Pulmonary Vasodilators?

Left ventricular assist devices (LVADs) improve survival and quality of life in patients with advanced heart failure. Despite these benefits, combined post- and precapillary pulmonary hypertension can be particularly problematic in patients on LVAD support, often exacerbating right ventricular (RV) dysfunction. Both persistently elevated pulmonary vascular resistance and RV dysfunction are associated with adverse outcomes, including death after LVAD. These observations have led to significant interest in the use of pulmonary vasodilators to treat pulmonary hypertension and preserve RV function among LVAD-supported patients. Although pulmonary vasodilators are commonly used for the treatment of pulmonary hypertension and RV dysfunction in LVADs, the benefits of this practice remain unclear. The purpose of this review is to highlight the current challenges in managing pulmonary vascular disease and RV dysfunction in patients with heart failure on LVAD support.

Pulmonary hypertension associated with left heart disease: Updated Recommendations of the Cologne Consensus Conference 2018

In the summer of 2016, delegates from the German Society of Cardiology (DGK), the German Respiratory Society (DGP), and the German Society of Pediatric Cardiology (DGPK) met in Cologne, Germany, to define consensus-based practice recommendations for the management of patients with pulmonary hypertension (PH). These recommendations were built on the 2015 European Pulmonary Hypertension guidelines, aiming at their practical implementation, considering country-specific issues, and including new evidence, where available. To this end, a number of working groups was initiated, one of which was specifically dedicated to PH associated with left heart disease. In this context, the European Guidelines point out that the drugs currently approved to treat patients with PAH (prostanoids, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, sGC stimulators) have not sufficiently been investigated in other forms of PH. However, despite the lack of respective efficacy data, an uncritical use of targeted PAH drugs in patients with PH associated with left heart disease is currently observed at an increasing rate. This development is a matter of concern. On the other hand, PH is a frequent problem that is highly relevant for morbidity and mortality in patients with left heart disease. In that sense, the distinction between isolated post-capillary pulmonary hypertension (IpcPH) and combined post- and pre-capillary pulmonary hypertension (CpcPH) and their proper definition may be of particular relevance. The detailed results and recommendations of the working group on PH associated with left heart disease, which were last updated in the spring of 2018, are summarized in this article.

Controversies and Challenges of Ventricular Assist Device Therapy

Left ventricular assist device (LVAD) therapy has emerged as an increasingly vital facet of the treatment algorithm for advanced heart failure. Growing experience with LVAD support has led to substantial improvements in outcomes, with 1-year survival rates approaching that of cardiac transplantation. These therapeutic refinements have engendered growing interests in the potential for expanding the clinical indications for LVAD therapy to patients with less advanced heart failure. The primary obstacles to this evolution of care center largely on the prevention and/or management of the adverse events associated with LVAD therapy along with patient preference. Many programs also face the mounting difficulty of balancing quality outcomes with the increased volume of implants. During the recently assembled Users Meeting organized by St. Jude Medical, heart failure clinicians from nearly 50 LVAD implanting centers discussed these and other challenges and controversies impacting the field. The present review summarizes the key insights gleaned from this meeting.

Outcomes and Trends of Ventricular Assist Device Selection in Children with End-Stage Heart Failure

We aimed to examine trends in ventricular assist device (VAD) selection, continuous flow devices (CFD) versus pulsatile flow devices (PFD), and their associated outcomes in children eligible for both device types. To accomplish this, the United Network for Organ Sharing database was reviewed for pediatric patients listed for heart transplant (HT) from January 2007 to June 2014. Patients were included if a durable VAD was present at wait listing or when removed from the waiting list and who met size eligibility for a CFD (BSA > 1.0 m). In total, 253 patients met inclusion criteria, 144 (57%) CFD and 109 (43%) PFD. Device type varied significantly based on year with CFD increasing from 11% in 2007 to 88% in 2014 (p < 0.01). PFD patients were younger, had a lower BSA, and an increased rate of extracorporeal membrane oxygenation and biventricular assist device support at listing. Survival to transplant or recovery was similar for CFDs and PFDs (96 vs. 94%; p = 0.57), as was the post-HT survival, 95% for both device types. Despite PFD patients having more risk factors for a poor outcome, survival was similar between device types. Even so, there is a dramatic trend toward CFD utilization in patients who are large enough to support one.

Defining the molecular signatures of human right heart failure

AIMS

Right ventricular failure (RVF) varies significantly from the more common left ventricular failure (LVF). This study was undertaken to determine potential molecular pathways that are important in human right ventricular (RV) function and may mediate RVF.

MATERIALS AND METHODS

We analyzed mRNA of human non-failing LV and RV samples and RVF samples from patients with pulmonary arterial hypertension (PAH), and post-LVAD implantation. We then performed transcript analysis to determine differential expression of genes in the human heart samples. Immunoblot quantification was performed followed by analysis of non-failing and failing phenotypes.

KEY FINDINGS

Inflammatory pathways were more commonly dysregulated in RV tissue (both non-failing and failing phenotypes). In non-failing human RV tissue we found important differences in expression of FIGF, TRAPPAC, and CTGF suggesting that regulation of normal RV and LV function are not the same. In failing RV tissue, FBN2, CTGF, SMOC2, and TRAPP6AC were differentially expressed, and are potential targets for further study.

SIGNIFICANCE

This work provides some of the first analyses of the molecular heterogeneity between human RV and LV tissue, as well as key differences in human disease (RVF secondary to pulmonary hypertension and LVAD mediated RVF). Our transcriptional data indicated that inflammatory pathways may be more important in RV tissue, and changes in FIGF and CTGF supported this hypothesis. In PAH RV failure samples, upregulation of FBN2 and CTGF further reinforced the potential significance that altered remodeling and inflammation play in normal RV function and failure.

Treatment and Prognosis of Pulmonary Hypertension in the Left Ventricular Assist Device Patient

This review will discuss the medical management of pulmonary hypertension in patients with left ventricular assist devices. Although much has been written on the management of primary pulmonary hypertension, also called pulmonary arterial hypertension, this review will instead focus on the treatment of pulmonary hypertension secondary to left heart disease. The relevant pharmacotherapy can be divided into medications for treating heart failure, such as diuretics and β-blockers, and medications for treating pulmonary hypertension. We also discuss important preoperative considerations in patients with pulmonary hypertension; the relationships between left ventricular assist devices, pulmonary hemodynamics, and right heart failure; as well as optimal perioperative and long-term postoperative medical management of pulmonary hypertension.

Preliminary Design and Testing of a Cavo-Arterial Pump Utilizing Axial Magnetic Couplings

Right ventricular (RV) dysfunction has limited the effectiveness of mechanical circulatory support (MCS) therapy in some heart failure (HF) patients. Intravascular pumps can provide adequate circulatory support without the need for extensive operations. The development of an intravascular right ventricular assist device (RVAD), called the cavo-arterial pump (CAP), is presented. Two prototypes of the CAP were developed to demonstrate the feasibility of providing adequate pulmonary support and to demonstrate the feasibility of using axial magnetic couplings for contactless torque transmission from the motor shaft to the pump impeller. The CAP utilizing a direct drive mechanism produced a maximum pressure of 100 mm Hg and a maximum flow of 2.25 L/min when operated at 24 kRPM. When a magnetic drive mechanism was used, the overall flowrate decreased due to a loss in torque transmission. The magnetic drive CAP was able to operate up to 18.5 kRPM and produce a maximum flowrate of 1.35 L/min and a maximum pressure difference of 40 mm Hg. These results demonstrate that the CAP produces sufficient output for partial circulatory support of the pulmonary circulation, and that axial magnetic couplings can help to eliminate the sealing system needed to isolate the miniature motor and bearings from blood contact.

[Indications and strategies in mechanical circulatory support : Rise of the machines?]

Terminal heart failure is an emerging problem with a continuously growing number of diseased patients worldwide. Because of the limited number of donor hearts, mechanical circulatory support is increasingly becoming an integral part of surgical treatment for end-stage heart failure, especially in patients deemed for destination therapy. Accurate patient selection, appropriate indication, and the optimal implantation time point guarantee a good outcome for these patients. This review article gives a systematic overview of the possible indication settings and treatment strategies for various patient groups in need of mechanical circulatory support.

Perioperative Care of the Patient With the Total Artificial Heart

Advanced heart failure continues to be a leading cause of morbidity and mortality despite improvements in pharmacologic therapy. High demand for cardiac transplantation and shortage of donor organs have led to an increase in the utilization of mechanical circulatory support devices. The total artificial heart is an effective biventricular assist device that may be used as a bridge to transplant and that is being studied for destination therapy. This review discusses the history, indications, and perioperative management of the total artificial heart with emphasis on the postoperative concerns.

Pulmonary Valve Opening With Two Rotary Left Ventricular Assist Devices for Biventricular Support

Right ventricular failure is a common complication associated with rotary left ventricular assist device (LVAD) support. Currently, there is no clinically approved long-term rotary right ventricular assist device (RVAD). Instead, clinicians have implanted a second rotary LVAD as RVAD in biventricular support. To prevent pulmonary hypertension, the RVAD must be operated by either reducing pump speed or banding the outflow graft. These modes differ in hydraulic performance, which may affect the pulmonary valve opening (PVO) and subsequently cause fusion, valvular insufficiency, and thrombus formation. This study aimed to compare PVO with the RVAD operated at reduced speed or with a banded outflow graft. Baseline conditions of systemic normal, hypo, and hypertension with severe biventricular failure were simulated in a mock circulation loop. Biventricular support was provided with two rotary VentrAssist LVADs with cardiac output restored to 5 L/min in banded outflow and reduced speed conditions, and systemic and pulmonary vascular resistances (PVR) were manipulated to determine the range of conditions that allowed PVO without causing left ventricular suction. Finally, RVAD sine wave speed modulation (±550 rpm) strategies (co- and counter-pulsation) were implemented to observe the effect on PVO. For each condition, outflow banding had higher PVR (97 ± 20 dyne/s/cm⁵ higher) for when the pulmonary valve closed compared to reduced speed. In addition, counter-pulsation demonstrated greater PVO than co-pulsation and constant speed. For the purpose of reducing the risks of pulmonary valve insufficiency, fusion, and thrombotic event, this study recommends a RVAD with a steeper H-Q gradient by banding and further exploration of RVAD speed modulation.

Effects of Left Ventricular Assist Device Support on End-Organ Function in Patients With Heart Failure: Comparison of Pulsatile- and Continuous-Flow Support in a Single-Center Experience

BACKGROUND

Limited data exist about the effects of continuous-flow versus pulsatile-flow left ventricular assist devices (LVADs) on end-organ function. We hypothesized that a pulsatile Polvad MEV (PM) would result in outcomes similar to those of similarly ill patients implanted with a continuous-flow LVAD (Heartware [HW] or Heartmate II [HMII]). We aimed to compare renal, hepatic, and hematologic functions in the 1st 30 days of support.

METHODS

We retrospectively reviewed patients with 24 PM (21 M, 3 F; group P) and 15 HW and 5 HMII (20 M, 0 F); group C LVAD implantations from April 2007 to February 2014. Creatinine, bilirubin, aspartate (AST) and alanine (ALT) transaminases, hematocrit, platelet count, international normalized ratio (INR), and activated partial thromboplastin time (APTT) parameters were analyzed before implantation and during 30 days of support. Demographic parameters were similar.

RESULTS

No significant differences were found between the groups regarding baseline renal, hepatic, or hematologic function. Baseline INR and APTT were significantly higher in group P. Levels of creatinine were similar between groups. They increased from baseline to postoperative day (POD) 1 and then decreased. Bilirubin levels were insignificantly higher in group P. Transaminases were significantly higher in group P (AST in PODs 3-6, ALT in PODs 3-7). INR values were significantly higher at baseline and in POD 0. APTT values were insignificantly higher in group P.

CONCLUSIONS

The use of LVAD improved renal and hepatic function in our series. Patients in group P had more decreased hepatic function and presented slower regeneration.

Right Ventricular Function in Patients With Left Ventricular Assist Device Support by Pulsatile Polvad MEV and Continuous-Flow Pumps Heartware and Heartmate II

BACKGROUND

Left ventricular assist device (LVAD) support is increasingly used in patients with heart failure. The right ventricle (RV) plays a main role in LVAD support. Little is known about the effects of pulsatile Polvad MEV devices or continuouseconds flow pumps on RV function. We compared hemodynamic parameters of RV in patients after implantation of Polvad MEV (PM) and Heartware (HW) or Heartmate II (HMII) LVADs.

METHODS

Forty-four patients were retrospectively reviewed after implantation of PM (group P; n = 24 [21 M, 3 F]) or HW or HMII (group C; n = 20 [20 M, 0 F]) LVADs from April 2007 to February 2014. Hemodynamic data-mean pulmonary pressure (mPAP), central venous pressure (CVP), cardiac output (CO), and cardiac index (CI)-were collected before surgery, after surgery, and every 2 hours in the intensive care unit, with the time points numbered from 1 to 120. Right ventricular work (RVW) was calculated according to the equation: RCW = CO × (mPAP - CVP) × 0.0144 (g·m).

RESULTS

Baseline characteristic of the patients were similar. mPAP values were similar between groups. CVP values were higher in group P, significantly at time points 5 and 7-33. CO values were higher in group C, significantly from point 3 and almost all the time to point 43. CI reached significance at point 9, 12-14, 16-19, and 30-41. RCW was higher in group P before implantation. Post-implantation RCW values were higher in group C, significantly at time points 19, 20, 32-34, 51-53, and 55-57.

CONCLUSIONS

Continuous-flow pumps more effectively optimize RV function than pulsatile LVADs, which can result in more effective prevention of RV failure or insuffiency in that group.

Early Biventricular Assist Device Use in Children: A Single-Center Review of 31 Patients

Biventricular assist device (BiVAD) support is considered a risk factor for worse outcomes compared with left ventricular assist device (LVAD) alone for children with end-stage heart failure. It remains unclear whether this is because of the morbidity associated with a second device or the underlying disease severity. We aimed to show that early BiVAD support can result in good survival by analyzing our prospectively collected database for all pediatric patients who underwent BiVAD implantation. From 2005 to 2009, BiVADs were used exclusively. From 2010 to 2014, LVAD alone was considered, maintaining a low threshold for BiVAD support. All BiVADs were pulsatile devices. Thirty-one patients with median age of 3.5 years received BiVAD support. Diagnoses included dilated cardiomyopathy in 17 (55%), myocarditis in 6 (19%), and congenital heart disease in 3 (10%). Survival to transplant was achieved in 27 (87%) with a median duration of 41 days (interquartile range, 15-69). Adverse event rates (per 100 days of support) were bleeding at 0.52, infection at 1.17, and central nervous system dysfunction at 0.78. Of those who survived to transplant, 26 (96%) remain alive with a median follow-up of 55 months. These results show that BiVAD support can bridge patients to transplant with excellent long-term survival.

The effect of acute mechanical left ventricular unloading on ovine tricuspid annular size and geometry

OBJECTIVES

Left ventricular assist device (LVAD) implantation may alter right ventricular shape and function and lead to tricuspid regurgitation. This in turn has been reported to be a determinant of right ventricular (RV) failure after LVAD implantation, but the effect of mechanical left ventricular (LV) unloading on the tricuspid annulus is unknown. The aim of the study was to provide insight into the effect of LVAD support on tricuspid annular geometry and dynamics that may help to optimize LV unloading with the least deleterious effect on the right-sided geometry.

METHODS

In seven open-chest anaesthetized sheep, nine sonomicrometry crystals were implanted on the right ventricle. Additional nine crystals were implanted around the tricuspid annulus, with one crystal at each commissure defining three separate annular regions: anterior, posterior and septal. Left ventricular unloading was achieved by connecting a cannula in the left atrium and the aorta to a continuous-flow pump. The pump was used for 15 min at a full flow of 3.8 ± 0.3 l/min. Epicardial echocardiography was used to assess the degree of tricuspid insufficiency. Haemodynamic, echocardiographic and sonomicrometry data were collected before and during full unloading. Tricuspid annular area, and the regional and total perimeter were calculated from crystal coordinates, while 3D annular geometry was expressed as the orthogonal distance of each annular crystal to the least squares plane of all annular crystals.

RESULTS

There was no significant tricuspid regurgitation observed either before or during LV unloading. Right ventricular free wall to septum diameter increased significantly at end-diastole during unloading from 23.6 ± 5.8 to 26.3 ± 6.5 mm (P = 0.009), but the right ventricular volume, tricuspid annular area and total perimeter did not change from baseline. However, the septal part of the annulus significantly decreased its maximal length (38.6 ± 8.1 to 37.9 ± 8.2 mm, P = 0.03). Annular contraction was not altered. The tricuspid annulus had a complex 3D saddle-shaped geometry that was unaffected during experimental conditions.

CONCLUSIONS

In healthy sheep hearts, left ventricular unloading increased septal-free wall RV diameter and reduced the length of the septal annulus, without altering the motion or geometry of the tricuspid annulus. Acute left ventricular unloading alone in healthy sheep was not sufficient to significantly perturb tricuspid annular dynamics and result in tricuspid insufficiency.

New therapy, new challenges: The effects of long-term continuous flow left ventricular assist device on inflammation

Surgically implanted continuous flow left ventricular assist devices (CF-LVADs) are currently used in patients with end-stage heart failure (HF). However, CF-LVAD therapy introduces a new set of complications and adverse events in these patients. Major adverse events with the CF-LVAD include right heart failure, vascular dysfunction, stroke, hepatic failure, and multi-organ failure, complications that may have inflammation as a common etiology. Our aim was to review the current evidence showing a relationship between these adverse events and elevated levels of inflammatory biomarkers in CF-LVAD recipients.

Inhaled Nitric Oxide Augments Left Ventricular Assist Device Capacity by Ameliorating Secondary Right Ventricular Failure

Clinical right ventricular (RV) impairment can occur with left ventricular assist device (LVAD) use, thereby compromising the therapeutic effectiveness. The underlying mechanism of this RV failure may be related to induced abnormalities of septal wall motion, RV distension and ischemia, decreased LV filling, and aberrations of LVAD flow. Inhaled nitric oxide (NO), a potent pulmonary vasodilator, may reduce RV afterload, and thereby increase LV filling, LVAD flow, and cardiac output (CO). To investigate the mechanisms associated with LVAD-induced RV dysfunction and its treatment, we created a swine model of hypoxia-induced pulmonary hypertension and acute LVAD-induced RV failure and assessed the physiological effects of NO. Increased LVAD speed resulted in linear increases in LVAD flow until pulse pressure narrowed. Higher speeds induced flow instability, LV collapse, a precipitous fall of both LVAD flow and CO. Nitric oxide (20 ppm) treatment significantly increased the maximal achievable LVAD speed, LVAD flow, CO, and LV diameter. Nitric oxide resulted in decreased pulmonary vascular resistance and RV distension, increased RV ejection, promoted LV filling and improved LVAD performance. Inhaled NO may thus have broad utility for the management of biventricular disease managed by LVAD implantation through the effects of NO on LV and RV wall dynamics.

Inhaled therapy for the management of perioperative pulmonary hypertension

Patients with pulmonary hypertension (PH) are at high risk for complications in the perioperative setting and often receive vasodilators to control elevated pulmonary artery pressure (PAP). Administration of vasodilators via inhalation is an effective strategy for reducing PAP while avoiding systemic side effects, chiefly hypotension. The prototypical inhaled pulmonary-specific vasodilator, nitric oxide (NO), has a proven track record but is expensive and cumbersome to implement. Alternatives to NO, including prostanoids (such as epoprostenol, iloprost, and treprostinil), NO-donating drugs (sodium nitroprusside, nitroglycerin, and nitrite), and phosphodiesterase inhibitors (milrinone, sildenafil) may be given via inhalation for the purpose of treating elevated PAP. This review will focus on the perioperative therapy of PH using inhaled vasodilators.

Future Prospects for the Total Artificial Heart

A total artificial heart (TAH) is the sole remaining option for patients with biventricular failure who cannot be rescued by left ventricular assist devices (LVADs) alone. However, the pulsatile TAH in clinical use today has limitations: large pump size, unknown durability, required complex anticoagulation regimen, and association with significant postsurgical complications. That pump is noisy; its large pneumatic driving lines traverse the body, with bulky external components for its drivers. Continuous-flow pumps, which caused a paradigm shift in the LVAD field, have already contributed to the rapidly evolving development of TAHs. Novel continuous-flow TAHs are only in preclinical testing or developmental stages. We here review the current state of TAHs, with recommended requirements for the TAH of the future.

Left ventricular assist devices: current controversies and future directions

Advanced heart failure is a growing epidemic that leads to significant suffering and economic losses. The development of left ventricular assist devices (LVADs) has led to improved quality of life and long-term survival for patients diagnosed with this devastating condition. This review briefly summarizes the short history and clinical outcomes of LVADs and focuses on the current controversies and issues facing LVAD therapy. Finally, the future directions for the role of LVADs in the treatment of end-stage heart failure are discussed.