Clinical experience with an implantable, intracardiac, continuous flow circulatory support device: physiologic implications and their relationship to patient selection

Percutaneous endovascular stenting to treat left ventricular assist device outflow graft stenosis

A 72-year-old woman presented with acute symptoms of congestive heart failure exacerbation and cardiogenic shock secondary to flow alarms in her HeartMate II left ventricular assist device (LVAD) placed in 2013. Her rapid deterioration required venoarterial extracorporeal membrane oxygenation placement with subsequent cardiac catheterization. A computed tomography scan corroborated 90% stenosis of the LVAD outflow graft with mural thrombus causing cardiogenic shock. A multidisciplinary team proceeded with endovascular treatment of the LVAD outflow obstruction via realignment with percutaneous angioplasty and placement of covered stent grafts. After in-hospital recovery, she was discharged to a rehabilitation facility.

Encouraging Regular Aortic Valve Opening for EVAHEART 2 LVAD Support Using Virtual Patient Hemodynamic Speed Modulation Analysis

This study focuses on investigating the EVAHEART 2 left ventricular assist device (LVAD) toward designing optimal pump speed modulation (PSM) algorithms for encouraging aortic valve (AV) flow. A custom-designed virtual patient hemodynamic model incorporating the EVAHEART 2 pressure-flow curves, cardiac chambers, and the systemic and pulmonary circulations was developed and used in this study. Several PSM waveforms were tested to evaluate their influence on the mean arterial pressure (MAP), cardiac output (CO), and AV flow for representative heart failure patients. Baseline speeds were varied from 1,600 to 2,000 rpm. For each baseline speed, the following parameters were analyzed: 1) PSM ratio (reduced speed/baseline speed), 2) PSM duration (3-7 seconds), 3) native ventricle contractility, and 4) patient MAP of 70 and 80 mm Hg. More than 2,000 rpm virtual patient scenarios were explored. A lower baseline speed (1,600 and 1,700 rpm) produced more opportunities for AV opening and more AV flow. Higher baseline speeds (1,800 and 2,000 rpm) had lower or nonexistent AV flow. When analyzing PSM ratios, a larger reduction in speed (25%) over a longer PSM (5+ seconds) duration produced the most AV flow. Lower patient MAP and increased native ventricle contractility also contributed to improving AV opening frequency and flow. This study of the EVAHEART 2 LVAD is the first to focus on leveraging PSM to enhance pulsatility and encourage AV flow. Increased AV opening frequency can benefit aortic root hemodynamics, thereby improving patient outcomes.

Heart, kidney and left ventricular assist device: a complex trio

BACKGROUND

Heart failure (HF) is a complex syndrome affecting the whole body, kidneys included. The left ventricular assist device (LVAD) is a valid option for patients with very severe HF. Focusing on renal function, LVAD implantation could theoretically reverse the detrimental effects of HF syndrome on kidneys. However, implanting an LVAD is a high-risk surgical procedure, and LVAD patients have higher risk of bleeding, device thrombosis, strokes, renal impairment, multi-organ failure and infections. Furthermore, an LVAD has its own particular effects on the renal system.

METHODS

In this review, we provide a comprehensive overview of the complex interaction between LVAD and the kidneys from the pathophysiological and clinical perspectives. An analysis of the different effects of pulsatile-flow and continuous-flow LVAD is provided.

RESULTS

Despite their limitations, creatinine-based estimated glomerular filtration rate (eGFR) formulas help to stratify patients by their post-LVAD placement prognosis. Poor basal renal function, the onset of acute kidney injury or the need for renal replacement therapy after LVAD implantation negatively influences a patient's prognosis. LVAD can also prompt an improvement in renal function, however, with some counterintuitive effects on a patient's prognosis.

CONCLUSION

It is still hard to say whether different trends in eGFR depend on different renal conditions before LVAD placement, on a patient's better overall status or on a particular patient management strategy before and/or after the device's implantation. Steps should be taken to solve this question because finding the best candidates for LVAD implantation is of paramount importance to ensure the best outcomes.

Kidney replacement therapy in pediatric patients on mechanical circulatory support: challenges for the pediatric nephrologist

The use of mechanical circulatory support (MCS) therapies in children with medically refractory cardiac failure has increased over the past two decades. With the growing experience and expertise, MCS is currently offered as a bridge to recovery or heart transplantation and in some cases even as destination therapy. Acute kidney injury (AKI) is common in patients with end-stage heart failure (ESHF). When severe AKI develops requiring kidney replacement therapy (KRT), these patients present unique challenges for the pediatric nephrology team. The use of KRT has not been adequately described in children with ESHF on the newer MCS. We also present original case series data from our center experience. The purpose of this review is to familiarize the reader with the current MCS technologies, approach to their selection, how they interact when combined with current KRT circuits, and distinguish similarities and differences. We will attempt to highlight the distinctive features of each technology, specifically focusing on growing trends in use of continuous-flow ventricular assist devices (CF-VAD) as it poses additional challenges to the pediatric nephrologist.

Effects of continuous-flow left ventricular assist devices on cerebral hemodynamics

Continuous-flow left ventricular assist devices (LVADs) reduce peak systolic flow, increase diastolic flow, and eliminate pulsatility of circulation. Altered blood flow may lead to a change in end-organ perfusion. Analysis of the flow dynamics of the arteries of end organs, such as the brain, may indicate whether an organ is perfused sufficiently. The aim of this study is to evaluate and identify the flow pattern changes of carotid (CA) and middle cerebral arteries (MCA) in LVAD patients and to compare with heart failure patients and healthy volunteers. Eighty-nine individuals were included in this cross-sectional study. Participants were divided into three groups: LVAD patients (n = 31), heart failure patients (n = 26), and healthy volunteers (n = 27). Carotid and transcranial Doppler ultrasonography were performed for all study groups for peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility (PI), and resistive (RI) indices of CA and MCA. Flow dynamics were compared between the groups. Doppler ultrasonographic data were analyzed at a median 12 (3-47) months after LVAD implantation. CA-PSV was lower in LVAD group compared with the other two groups (P < .001), MCA-PSV of LVAD and heart failure groups were similar and lower than healthy volunteers (P < .05). The highest values for CA-EDV were found in the LVAD group (P < .05). MCA-EDV values were found to be lowest in heart failure group (P < .05). For PI and RI, in all CA and MCA, the LVAD group had lower indices compared with the other two groups (P < .001). In addition, MCA flow analysis in patients with LVADs was identified for the first time with this study.

Anaesthesia for Implantation of the Jarvik 2000 Flowmaker® LVAD

The Jarvik 2000 Flowmaker® is an intraventricular continuous axial flow left ventricular assist device. We describe the anaesthetic management and considerations for five patients with end-stage heart failure who underwent implantation of the Jarvik 2000 Flowmaker® as a bridge to transplantation or as destination therapy.

Living Without a Pulse: The Vascular Implications of Continuous-Flow Left Ventricular Assist Devices

Pulsatility seems to have a teleological role because evolutionary hierarchy favors higher ordered animals with more complex, multichamber circulatory systems that generate higher pulse pressure compared with lower ordered animals. Yet despite years of such natural selection, the modern generation of continuous-flow left ventricular assist devices (CF-LVADs) that have been increasingly used for the last decade have created a unique physiology characterized by a nonpulsatile, nonlaminar blood flow profile with the absence of the usual large elastic artery Windkessel effect during diastole. Although outcomes and durability have improved with CF-LVADs, patients supported with CF-LVADs have a high rate of complications that were not as frequently observed with older pulsatile devices, including gastrointestinal bleeding from arteriovenous malformations, pump thrombosis, and stroke. Given the apparent fundamental biological role of the pulse, the purpose of this review is to describe the normal physiology of ventricular-arterial coupling from pulsatile flow, the effects of heart failure on this physiology and the vasculature, and to examine the effects of nonpulsatile blood flow on the vascular system and potential role in complications seen with CF-LVAD therapy. Understanding these concomitant vascular changes with CF-LVADs may be a key step in improving patient outcomes as modulation of pulsatility and flow characteristics may serve as a novel, yet simple, therapy for reducing complications.

Peripheral Artery Disease and Continuous Flow Left Ventricle Assist Device: An Engaging Complement Analysis May Help to Guide Treatment

Use of continuous flow left ventricle assist device (CF-LVAD) in advanced heart failure (HF) patients results in clinically relevant improvements in survival, functional capacity, and quality of life. Peripheral artery disease (PAD) can occur in patients with CF-LVAD due to the high rate of concomitance between risk factors for atherosclerosis and HF. Diagnosis of PAD can be difficult in the specific setting of a patient supported by this kind of device because of the marked alteration in waveform morphology and velocity created by the artificial physiology of an LVAD. We report the case of a 53-year-old man with HF secondary to ischemic cardiomyopathy supported by the HeartWare HVAD as bridge to transplant, who after the implant developed symptoms suggestive of PAD. We describe additional computational flow analysis for the study of PAD-related hemodynamic disturbances induced by a CF-LVAD. Flow simulations enhance the information of clinical image data, and may have an application in clinical investigations of the risk of hemodynamic disturbances induced by LVAD implantation.

Bleeding with the artificial heart: Gastrointestinal hemorrhage in CF-LVAD patients

Continuous-flow left ventricular assist devices (CF-LVADs) have significantly improved outcomes for patients with end-stage heart failure when used as a bridge to cardiac transplantation or, more recently, as destination therapy. However, its implantations carries a risk of complications including infection, device malfunction, arrhythmias, right ventricular failure, thromboembolic disease, postoperative and nonsurgical bleeding. A significant number of left ventricular assist devices (LVAD) recipients may experience recurrent gastrointestinal hemorrhage, mainly due to combination of antiplatelet and vitamin K antagonist therapy, activation of fibrinolytic pathway, acquired von Willebrand factor deficiency, and tendency to develop small intestinal angiodysplasias due to increased rotary speed of the pump. Gastrointestinal bleeding in LVAD patients remains a source of increased morbidity including the need for blood transfusions, extended hospital stays, multiple readmissions, and overall mortality. Management of gastrointestinal bleeding in LVAD patients involves multidisciplinary approach in stabilizing the patients, addressing risk factors and performing structured endoluminal evaluation with focus on upper gastrointestinal tract including jejunum to find and eradicate culprit lesion. Medical and procedural intervention is largely successful and universal bleeding cessation occurs in transplanted patients.

Dynamic Changes in Aortic Vascular Stiffness in Patients Bridged to Transplant With Continuous-Flow Left Ventricular Assist Devices

OBJECTIVES

The aim of this study was to measure aortic vascular stiffness from orthotopic heart transplant (OHT) patients exposed to varying types of flow as a result of the presence or absence of left ventricular assist device (LVAD) support pre-OHT.

BACKGROUND

The effects of continuous-flow LVADs (CF-LVADs) on vascular properties are unknown, but may contribute to the pathophysiology of CF-LVAD complications such as stroke, hypertension, and bleeding.

METHODS

Echocardiograms were reviewed from 172 OHT patients immediately before LVAD and at 3 time points post-OHT: baseline, 6 months, and 1 year. For each study, pulse pressure and aortic end-systolic and end-diastolic dimensions were used to calculate aortic strain, distensibility, and stiffness index. Patients were categorized into 3 groups based on the presence or absence of a LVAD and a pulse pre-OHT: No LVAD (n = 111), LVAD No Pulse (n = 30), and LVAD With Pulse (n = 31).

RESULTS

The aortic stiffness index among LVAD No Pulse patients increased from 2.8 ± 1.1 pre-CF-LVAD to 10.9 ± 4.7 immediately post-OHT (p < 0.001). This aortic stiffness index was also significantly higher compared with No LVAD (3.4 ± 1.1; p < 0.001) and LVAD With Pulse (3.7 ± 1.4; p < 0.001) immediately post-OHT with attenuation of these differences by 1 year post-OHT. Similar findings were noted for the other indices of aortic stiffness.

CONCLUSIONS

Aortic stiffness is markedly increased immediately post-OHT among patients bridged with CF-LVADs, with attenuation of this increased stiffness over the first year after transplant. These results suggest that aortic vascular properties are dynamic and may be influenced by alterations in flow pulsatility. As more patients are supported with CF-LVADs and as newer pump technology attempts to modulate pulsatility, further research examining the role of alterations in flow patterns on vascular function and the potential resultant systemic sequelae are needed.

Does Gender Influence the Likelihood or Types of Complications Following Cardiac Surgery?

Over 410,000 cardiac surgeries are performed in American women each year. Women having coronary artery bypass graft (CABG) and valve surgery do so at an older age and with more cardiovascular risk factors than men. Women's smaller body size may also increase risk by increasing the technical difficulty of surgical procedures. Female CABG patients appear to have higher perioperative mortality and cardiac morbidity, although studies of neurologic outcomes in female CABG patients have produced equivocal findings. Women undergoing CABG tend to consume more hospital resources than men do in terms of blood transfusion, mechanical ventilation, and length of intensive care unit and overall hospital stay. With regard to valve surgery, women appear to have worse outcomes than men if the surgery is combined with a CABG operation. Women and men undergoing isolated aortic valve surgery have similar mortality, but little is known about gender differences in mitral and tricuspid valve surgery outcomes. Women who require heart transplantation tend to have idiopathic cardiomyopathy rather than the ischemic cardiomyopathy that is more common in male heart transplant candidates. Although female heart transplant recipients seem to have a stronger immunologic response after transplantation, which manifests in more frequent acute rejection episodes, it is not clear whether this increases women's mortality risk. Men appear to have a greater incidence of posttransplant vasculopathy than women. Further research is needed to identify risk factors for perioperative morbidity and mortality in women undergoing cardiac surgery and to develop medical interventions to mitigate these risks.

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.

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 continuous-flow total artificial heart and vascular permeability

BACKGROUND

We tested the short-term effects of completely nonpulsatile versus pulsatile circulation after ventricular excision and replacement with total implantable pumps in an animal model on peripheral vascular permeability.

METHODS

Ten calves underwent cardiac replacement with two HeartMate III continuous-flow rotary pumps. In five calves, the pump speed was rapidly modulated to impart a low-frequency pulse pressure in the physiologic range (10-25 mm Hg) at a rate of 40 pulses per minute (PP). The remaining five calves were supported with a pulseless systemic circulation and no modulation of pump speed (NP). Skeletal muscle biopsies were obtained before cardiac replacement (baseline) and on postoperative days (PODs) 1, 7, and 14. Skeletal muscle-tissue water content was measured, and morphologic alterations of skeletal muscle were assessed. VE-cadherin, phospho-VE-cadherin, and CD31 were analyzed by immunohistochemistry.

RESULTS

There were no significant changes in tissue water content and skeletal muscle morphology within group or between groups at baseline, PODs 1, 7, and 14, respectively. There were no significant alterations in the expression and/or distribution of VE-cadherin, phospho-VE-cadherin, and CD31 in skeletal muscle vasculature at baseline, PODs 1, 7, and 14 within each group or between the two groups, respectively. Although continuous-flow total artificial heart (CFTAH) with or without a pulse pressure caused slight increase in tissue water content and histologic damage scores at PODs 7 and 14, it failed to reach statistical significance.

CONCLUSIONS

There was no significant adherens-junction protein degradation and phosphorylation in calf skeletal muscle microvasculature after CFTAH implantation, suggesting that short term of CFTAH with or without pulse pressure did not cause peripheral endothelial injury and did not increase the peripheral microvascular permeability.

Pre-Operative Right Ventricular Dysfunction Is Associated With Gastrointestinal Bleeding in Patients Supported With Continuous-Flow Left Ventricular Assist Devices

OBJECTIVES

This study sought to determine whether severe right ventricular (RV) dysfunction in the pre-operative setting is associated with an increased risk of gastrointestinal bleeding (GIB) post-left ventricular assist device (LVAD).

BACKGROUND

GIB is a significant complication in patients supported with continuous-flow LVADs. The impact of RV dysfunction on the risk of GIB has not been investigated.

METHODS

We retrospectively identified 212 patients who survived index hospitalization after implantation of HeartMate II (Thoratec Corp., Pleasanton, California) or Heartware HVAD (HeartWare Corp., Framingham, Massachusetts) from June 2009 to April 2013. Patients with severe RV dysfunction on pre-LVAD echocardiogram (n = 37) were compared to patients without severe RV dysfunction (n = 175). The primary outcome was freedom from GIB.

RESULTS

The majority of patients were male (79%) with a median INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) profile of 2 at LVAD implantation. There were no significant differences between cohorts with respect to demographics, comorbidities, device type, international normalization ratio, or aspirin strategy. During follow-up, 81 patients had GIB events: 23 of 37 (62%) in the severe RV dysfunction group versus 58 of 175 (33%) in the control group (p = 0.001). After adjustment for age and ischemic cardiomyopathy, severe RV dysfunction was associated with increased risk of GIB (hazard ratio: 1.799, 95% confidence interval: 1.089 to 2.973, p = 0.022).

CONCLUSIONS

In this single-center sample of patients supported with continuous-flow LVADs, severe RV dysfunction on pre-LVAD echocardiogram was associated with an increased risk of GIB. Further studies are needed to investigate possible mechanisms by which RV dysfunction increases the risk of GIB and to identify patient populations who may benefit from alterations in antithrombotic strategies.

In-Series Versus In-Parallel Mechanical Circulatory Support for the Right Heart: A Simulation Study

Right heart failure (RHF) is a serious health issue with increasing incidence and high mortality. Right ventricular assist devices (RVADs) have been used to support the end-stage failing right ventricle (RV). Current RVADs operate in parallel with native RV, which alter blood flow pattern and increase RV afterload, associated with high tension in cardiac muscles and long-term valve complications. We are developing an in-series RVAD for better RV unloading. This article presents a mathematical model to compare the effects of RV unloading and hemodynamic restoration on an overloaded or failing RV. The model was used to simulate both in-series (sRVAD) and in-parallel (pRVAD) (right atrium-pulmonary artery cannulation) support for severe RHF. The results demonstrated that sRVAD more effectively unloads the RV and restores the balance between RV oxygen supply and demand in RHF patients. In comparison to simulated pRVAD and published clinical and in silico studies, the sRVAD was able to provide comparable restoration of key hemodynamic parameters and demonstrated superior afterload and volume reduction. This study concluded that in-series support was able to produce effective afterload reduction and preserve the valve functionality and native blood flow pattern, eliminating complications associated with in-parallel support.

Characteristics of gastrointestinal bleeding after placement of continuous-flow left ventricular assist device: a case series

BACKGROUND

Medical management of patients with continuous-flow left ventricular assist devices (LVADs) remains challenging for the gastroenterologist given their high risk of gastrointestinal bleeding (GIB) and need for continuous anticoagulation.

AIMS

Our aim was to better characterize LVAD patients who presented with a GIB at our facility and delineate the prevalence, presentation, time to diagnosis, management, and therapeutic endoscopic interventions, including small bowel tools that may offer additional benefit.

METHODS

We retrospectively reviewed adult patients (>18 years) who underwent LVAD implantation at our tertiary care facility between October 2011 and October 2013. Electronic medical records were reviewed for presenting symptoms, average days to initial and repeat GIB, hospital course, and techniques that led to diagnosis and hemostasis.

RESULTS

Eighteen patients underwent LVAD implantation, of which 61 % presented with a GIB for a total of 20 presentations (1.8 per patient). Mean time to initial GIB was 154 days. Patients required an average of 1.8 endoscopic procedures per admission. Esophagogastroduodenoscopy (EGD) and push enteroscopy (PE) were more likely to lead to a diagnosis, and EGD was the most commonly used diagnostic tool at initial presentation. Sixty percent of patients who initially received EGD presented with a recurrent GIB and required PE, which was diagnostic and therapeutic for small bowel angiodysplasias in 80 % of cases.

CONCLUSION

We found a higher GIB rate compared with prior studies. Bleeding events were associated with multiple procedures and interventions. We recommend an algorithmic approach to LVAD patients who bleed. Our experience suggests that PE is warranted at initial presentation in order to achieve hemostasis, prevent recurrent GIB, and decrease subsequent readmission rates.

Ventricular reconditioning and pump explantation in patients supported by continuous-flow left ventricular assist devices

BACKGROUND

The potential for myocardial reconditioning and device explantation after long-term continuous-flow left ventricular assist device (LVAD) support presents an opportunity to delay or avoid transplantation in select patients.

METHODS

Thirty of 657 patients with end-stage heart failure supported with continuous-flow LVADs were assessed for device explantation. Each patient underwent an individualized process of weaning focused on principles of ventricular unloading, gradual reconditioning, and transition to medical therapy.

RESULTS

After varying reconditioning periods, 27 patients (16 men, 11 women; age, 39 ± 12 years) underwent LVAD explant, and 3 patients (2 men, 1 woman; age, 22 ± 6 years) were evaluated for explantation but could not be weaned. The duration of LVAD support was 533 ± 424 days (range, 42-1,937 days) for the explant cohort and 1,097 ± 424 days (range, 643-1,483) for the non-explant cohort. The LV end-diastolic dimension, LV ejection fraction, systolic pulmonary artery pressure, cardiac output, and cardiac index in the explant cohort were significantly improved at explantation (all, p < 0.05). Two late deaths occurred after LVAD explantation despite satisfactory native cardiac function, and 1 patient required resumption of LVAD support 2.7 years after device removal. The remaining explant patients remain in New York Heart Association classes I to II with medical management alone (mean survival post-explant, 1,172 ± 948 days). The 3 candidates who could not be weaned ultimately underwent transplantation.

CONCLUSIONS

The potential for recovery of native LV function after long-term continuous-flow LVAD support should encourage a more aggressive approach to ventricular reconditioning with the goal of device explantation and a return to medical management, particularly in young patients with dilated cardiomyopathy.

Left ventricular assist devices as a bridge to cardiac transplantation

Heart failure remains a significant cause of morbidity and mortality, affecting over five million patients in the United States. Continuous-flow left ventricular assist devices (LVAD) have become the standard of care for patients with end stage heart failure. This review highlights the current state of LVAD as a bridge to transplant (BTT) in patients requiring mechanical circulatory support (MCS).

Mitral valve repair at the time of continuous-flow left ventricular assist device implantation confers meaningful decrement in pulmonary vascular resistance

We hypothesized that the addition of mitral valve replacement or repair (MVR) to implantation of continuous-flow left ventricular assist device (cf-LVAD) may further decrease pulmonary vascular resistance (PVR) over Heartmate II (HMII) implantation alone. Patients undergoing MVR with concomitant HMII implantation were compared with those undergoing HMII implantation alone. Of the 57 patients undergoing cf-LVAD implantation, 21 (36.8%) underwent concomitant MVR and 36 (63.2%) underwent cf-LVAD implantation alone. Patients receiving MVR had greater decrement in PVR (59.4% vs. 35.2%, p = 0.01). Decrease in end-diastolic diameter was greater for patients receiving MVR but did not reach statistical significance (18.2 vs. 13.5 mm, p = 0.33). Duration of mechanical ventilation (121.6 vs. 181.4 hours, p = 0.45) and inotropic support (162.4 vs. 153.2 hours, p = 0.86), change in creatinine (0.19 vs. -0.26 mg/dl, p = 0.34), increase in bilirubin (2.54 vs. 1.55 mg/dl, p = 0.63), intensive care unit stay (168.0 vs. 231.5 hours, p = 0.38), and overall length of stay (32.0 vs. 42.5 days, p = 0.75) were similar. There was no difference in survival at 3 months (89.7% vs. 83.3%) and 1 year (83.7 vs. 67.3%, p = 0.34). Addition of MVR may result in greater decrement of PVR than HMII implantation alone. This may permit certain patients thought to be ineligible for transplantation to become candidates.

Modified central closure technique for treatment of aortic insufficiency in patients on left ventricular assist device support

Development of aortic insufficiency (AI) in a patient with a continuous flow left ventricular assist device (CF-LVAD) represents a serious complication. The circulatory loop that is created by the AI can lead to cardiogenic shock, malperfusion, and multisystem organ failure. The central closure technique has been well described and is a popular method of repairing the aortic valve in CF-LVAD patients with AI. Because of an early failure using this technique, we developed a modification of this technique that we describe in this report that can be particularly useful when the aortic valve leaflet tissue is relatively normal or thin, as opposed to thickened/fibrosed, as the strength of the repair is not solely provided by the central coaptation point of the leaflets, but is rather, distributed more diffusely across the leaflets.

Past and present of cardiocirculatory assist devices: a comprehensive critical review

During the last 20 years, the management of heart failure has significantly improved by means of new pharmacotherapies, more timely invasive treatments and device assisted therapies. Indeed, advances in mechanical support, namely with the development of more efficient left ventricular assist devices (LVADs), and the total artificial heart have reduced mortality and morbidity in patients awaiting transplantation, so much so, that LVADs are now approved of as a strategy for destination therapy. In this review, the authors describe in detail the current basic indications, functioning modalities, main limitations of surgical LAVDs, total artificial heart development, and percutaneous assist devices, trying to clarify this complex, but fascinating topic.

von Willebrand factor, shear stress, and ADAMTS13 in hemostasis and thrombosis

von Willebrand factor (VWF), an adhesive glycoprotein whose deficiency is best known for causing bleeding in patients with von Willebrand disease (VWD), is a complex molecule with a myriad of mysterious properties including its dependence on shear stress for adhesive functions. The discovery of ADAMTS13 has provided a critical impetus for understanding the regulation of VWF activity by shear stress. This communication reviews the current knowledge in VWF homeostasis and illustrates how this knowledge may help understand the changes affecting patients with various conditions including thrombotic thrombocytopenic purpura, VWD, hemolytic uremic syndrome, aortic stenosis, and ventricular assist devices.

The ABCs of left ventricular assist device echocardiography: a systematic approach

Echocardiography is an important imaging modality used to determine the indication of left ventricular assist device (LVAD) implantation for patients with advanced heart failure (HF) and for serial follow-up to make management decisions in patient care post-implant. Continuous axial-flow LVAD therapy provides effective haemodynamic support for the failing left ventricle, improving both the clinical functional status and quality of life. Echocardiographers must develop a systematic approach to echocardiographic assessment of LVAD implantation and post-LVAD implant cardiac morphology and physiology. This approach must include the evaluation of left and right heart chamber morphology and physiology and the anatomy and physiology of the inflow and outflow cannulas and the rotor pump, and the determination of the degree of tricuspid regurgitation and the presence of interatrial shunts and aortic regurgitation. Collaboration among the echocardiography and HF/transplant teams is essential to obtain this comprehensive evaluation. We outline a systematic approach to evaluating patients with HF who have failed conventional therapy and require LVAD therapy as a bridge to cardiac transplantation or destination therapy.

Gastrointestinal bleeding with the HeartMate II left ventricular assist device

BACKGROUND

Continuous flow left ventricular assist devices (CF-LVADs) have yielded improved outcomes compared with pulsatile flow devices for patients on long-term support. However, significant rates of gastrointestinal bleeding (GIB) have been observed during CF-LVAD support.

METHODS

From March 2006 through March 2011, 86 patients with chronic heart failure underwent implantation of a CF-LVAD (HeartMate II; Thoratec Corp., Pleasanton, CA). Records were reviewed to determine the prevalence of post-implant GIB, location of the bleeding site and associated morbidity and mortality. Uni- and multivariate analyses were conducted to identify independent predictors of GIB.

RESULTS

GIB occurred in 19 patients (22.1%) with a duration of support that ranged from 5 to 456 days. Sources of GIB included small bowel and rectum in 6 patients each, large bowel in 2 patients and stomach in 1 patient. No definite source was identified in 4 patients. There were no deaths referable to GIB. Recurrent GIB occurred in 4 patients. History of a GIB prior to LVAD implant was the only variable significantly different between patients with and without post-implant GIB (21.1% vs 10.4%, p = 0.016), and was the only independent predictor of GIB (OR = 2.24, 95% CI 2.121 to 2.435, p = 0.004).

CONCLUSIONS

Gastrointestinal bleeding is a frequent source of morbidity for patients on HeartMate II LVAD support but does not significantly impact survival. As implantation of CF-LVADs with non-pulsatile flow gains popularity for both bridge-to-transplant and destination therapy, a better understanding of the pathophysiology of GIB in these patients will be needed for minimizing this complication.

Arteriovenous malformation and gastrointestinal bleeding in patients with the HeartMate II left ventricular assist device

BACKGROUND

In this study we investigated gastrointestinal (GI) bleeding and its relationship to arteriovenous malformations (AVMs) in patients with the continuous-flow HeartMate II (HMII) left ventricular assist device (LVAD).

METHODS

The records of 172 patients who received HMII support between November 2003 and June 2010 were reviewed. Patients were considered to have GI bleeding if they had 1 or more of the following symptoms: guaiac-positive stool; hematemesis; melena; active bleeding at the time of endoscopy or colonoscopy; and blood within the stomach at endoscopy or colonoscopy. The symptom(s) had to be accompanied by a decrease of >1 g/dl in the patient's hemoglobin level. The location of the bleeding was identified as upper GI tract, lower GI tract or both according to esophagogastroduodenoscopy, colonoscopy, small-bowel enteroscopy or mesenteric angiography. Post-LVAD implantation anti-coagulation therapy consisted of warfarin, aspirin and dipyridamole.

RESULTS

Thirty-two of the 172 patients (19%) had GI bleeding after 63 ± 62 (range 8 to 241) days of HMII support. Ten patients had GI bleeding from an AVM; these included 3 patients who had 2 bleeding episodes and 2 patients who had 5 episodes each. Sixteen patients had upper GI bleeding (10 hemorrhagic gastritis, 4 gastric AVM, 2 Mallory-Weiss syndrome), 15 had lower GI bleeding (6 diverticulosis, 6 jejunal AVM, 1 drive-line erosion of the colon, 1 sigmoid polyp, 1 ischemic colitis) and 1 had upper and lower GI bleeding (1 colocutaneous and gastrocutaneous fistula). All GI bleeding episodes were successfully managed medically.

CONCLUSIONS

Arteriovenous malformations can cause GI bleeding in patients with continuous-flow LVADs. In all cases in this series, GI bleeding was successfully managed without the need for surgical intervention.

Mechanical circulatory support as a bridge to transplant or for destination therapy

Mechanical circulatory support (MCS) frequently is used to treat medically refractory end-stage heart failure. Initially designed to be a bridge to transplantation, MCS also has proven itself as a durable therapy for patients who are not transplant candidates. As outcomes for patients with MCS have improved, research interest in device development has flourished, with many new device types under investigation. In addition to improvement of MCS devices, investigational work continues to achieve appropriate patient selection and complication management.

Focused review on transthoracic echocardiographic assessment of patients with continuous axial left ventricular assist devices

Left ventricular assist devices (LVADs) are systems for mechanical support for patients with end-stage heart failure. Preoperative, postoperative and comprehensive followup with transthoracic echocardiography has a major role in LVAD patient management. In this paper, we will present briefly the hemodynamics of axial-flow LVAD, the rationale, and available data for a complete and organized echocardiographic assessment in these patients including preoperative assessment, postoperative and long-term evaluation.

Management options to treat gastrointestinal bleeding in patients supported on rotary left ventricular assist devices: a single-center experience

Gastrointestinal (GI) bleeding in ventricular assist devices (VADs) has been reported with rotary devices. The pathophysiological mechanisms and treatments are in evolution. We performed a retrospective review of GI bleeding episodes for all VADs implanted at our institution. Five male patients experienced GI bleeding-age 63.6 ± 3.64 years. VAD type VentrAssist n = 1, Jarvik 2000 n = 2, and HeartWare n = 2. All patients were anticoagulated as per protocol with antiplatelet agents (aspirin and/or clopidogrel bisulfate [Plavix] and warfarin (therapeutic international normalized ratio 2.0-3.5). There was no prior history of gastric bleeding in this group. Ten episodes of bleeding requiring blood transfusion occurred in five patients. Some patients had multiple episodes (1 × 5, 1 × 2, 3 × 1). The events occurred at varying times post-VAD implantation (days 14, 21, 26, 107, 152, 189, 476, 582, 669, and 839). Octreotide (a long-acting somatostatin analogue that reduces splanchnic arterial and portal blood flow) was administered subcutaneously or intravenously. Three patients received infusions of adrenaline at 1 µg/min to enhance pulsatility. Anticoagulation was interrupted during bleeding episodes but successfully introduced post bleeding event. GI bleeding is a significant complication of VAD therapy. In this article, we discuss diagnosis and management options.

Infectious complications in patients with left ventricular assist device: etiology and outcomes in the continuous-flow era

BACKGROUND

Continuous-flow left ventricular assist devices (LVAD) are increasingly being used in patients with end-stage heart failure and have largely replaced older generation pulsatile devices. While significant rates of infection have been reported in patients with pulsatile device support, incidence and outcomes of this complication for the continuous-flow device patients remain unknown.

METHODS

Between June 2005 and August 2009, 81 patients were implanted with continuous-flow LVADs at Washington University School of Medicine either as bridge to transplantation or as destination therapy. Outcomes of this study included incidence of postimplantation infection, types of infection, microbiologic profile, and association of postimplantation infections with clinical endpoints.

RESULTS

Forty-two patients (51.9%) had at least one type of infection on continuous-flow LVAD support with a mean follow-up period of 9.2 ± 9.2 months. Patients who had an infection on LVAD support had a significantly prolonged hospital stay (37.9 ± 32.0 versus 20.7 ± 23.0 days, p = 0.008) and a trend toward increased mortality (33.1% versus 18.7% at 2 years, respectively, log rank p = 0.102) compared with patients who did not. Subgroup analysis revealed that postimplantation sepsis was significantly associated with increased mortality in the continuous-flow LVAD cohort (61.9% versus 18.0% at 2 years, respectively, in septic and nonseptic patients, log rank p = 0.001). The majority of the sepsis cases occurred before hospital discharge, whereas most of the device related infections occurred after discharge. Resistant Staphylococcus and Pseudomonas species were the most common pathogens leading to device- and nondevice-related local infections. Development of driveline or pocket infection had no effect on survival in patients with continuous-flow assist device support (p = 0.193).

CONCLUSIONS

Even though better clinical outcomes have been achieved with the newer generation continuous-flow devices, infection complications-in particular sepsis-are still a major risk for patients with continuous-flow LVAD implantation. Prevention strategies with aggressive medical and surgical management of infections may increase survival and decrease morbidity among continuous-flow LVAD patients.

Ventricular assist device outflow-graft site: effect on myocardial blood flow

BACKGROUND

Recent advances in left ventricular assist device (LVAD) technology have resulted in small, durable, energy-efficient, continuous-flow blood pumps that can support patients with end-stage heart failure. However, the effects of reduced or nonpulsatile flow on end-organ function are unclear. We performed a pilot study in calves with a continuous-flow LVAD to assess the effects of the pump's outflow-graft location (ascending versus descending aorta) on myocardial blood flow.

MATERIALS AND METHODS

In 8 healthy calves, we implanted the Jarvik 2000 LVAD in the left ventricular apex without the use of cardiopulmonary bypass. We anastomosed the outflow graft to either the ascending aorta (group 1; n = 4) or the descending aorta (group 2; n = 4). Hemodynamic parameters, myocardial oxygen consumption, and regional myocardial blood flow (analyzed with colored microspheres) were assessed at baseline (pump off) and during pump operation at 8000, 10,000, and 12,000 rpm.

RESULTS

No intergroup differences were found in the aortic pressure, heart rate, central venous pressure, pump-flow to total-cardiac-flow ratio, or blood flow in the left anterior descending and right posterior descending coronary arteries at increasing pump speeds. Neither myocardial oxygen consumption nor myocardial tissue perfusion differed significantly between the two groups.

CONCLUSIONS

Regardless of the outflow-graft location (ascending versus descending aorta), the continuous-flow LVAD unloaded the left ventricle and did not adversely affect myocardial perfusion in either the right or left ventricle. Owing to the small number of animals studied, however, the most we can conclude is that neither outflow-graft location appeared to be inferior to the other.

Renal and hepatic function improve in advanced heart failure patients during continuous-flow support with the HeartMate II left ventricular assist device

BACKGROUND

The effects of continuous blood flow and reduced pulsatility on major organ function have not been studied in detail.

METHODS AND RESULTS

We evaluated renal (creatinine and blood urea nitrogen) and hepatic (aspartate transaminase, alanine transaminase, and total bilirubin) function in 309 (235 male, 74 female) advanced heart failure patients who had been supported with the HeartMate II continuous-flow left ventricular assist device for bridge to transplantation. To determine whether patients with impaired renal and hepatic function improve over time with continuous-flow left ventricular assist device support or whether there are any detrimental effects in patients with normal organ function, we divided patients into those with above-normal and normal laboratory values before implantation and measured blood chemistry over time during left ventricular assist device support. There were significant improvements over 6 months in all parameters in the above-normal groups, with values in the normal groups remaining in the normal range over time. Mean blood urea nitrogen and serum creatinine in the above-normal groups decreased significantly from 37+/-14 to 23+/-10 mg/dL (P<0.0001) and from 1.8+/-0.4 to 1.4+/-0.8 mg/dL (P<0.01), respectively. There were decreases in aspartate transaminase and alanine transaminase in the above-normal groups from 121+/-206 and 171+/-348 to 36+/-19 and 31+/-22 IU (P<0.001), respectively. Total bilirubin for the above-normal group was 2.1+/-0.9 mg/dL at baseline; after an acute increase at week 1, it decreased to 0.9+/-0.5 mg/dL by 6 months (P<0.0001). Both renal and liver values from patients in the normal groups remained normal during support with the left ventricular assist device.

CONCLUSIONS

The HeartMate II continuous-flow left ventricular assist device improves renal and hepatic function in advanced heart failure patients who are being bridged to transplantation, without evidence of detrimental effects from reduced pulsatility over a 6-month time period.