Management of heparin-induced thrombocytopenia with fondaparinux in a patient with left ventricular assist device

Heparin-induced thrombocytopenia is an immune-mediated serious adverse effect of heparin therapy. It is a relatively frequent complication among patients with mechanical circulatory support. Herein, we present a patient with severe heart failure and sepsis who developed heparin-induced thrombocytopenia shortly after implantation of left ventricular assist device as a bridge to transplantation and who was successfully treated with fondaparinux.

Ventricular Assist Devices - Evolution of Surgical Heart Failure Treatment

End-stage heart failure represents a substantial worldwide problem for the healthcare system. Despite significant improvements (medical heart failure treatment, implantable cardioverters, cardiac resyschronisation devices), long-term survival and quality of life of these patients remains poor. Heart transplantation has been an effective therapy for terminal heart failure, but it remains limited by an increasing shortage of available donor organs along with strict criteria defining acceptable recipients. For the last 50 years, mechanical alternatives to support the circulation have been investigated; however, during the early years device development has been marked in general by slow progress. However, in the past two decades, the technology has evolved dramatically. The purpose of this review is to give a short summary on the evolution of ventricular assist device (VAD) therapy and to give perspectives for future treatment of heart failure.

Pediatric mechanical circulatory support

Mechanical circulatory support (MCS) in the pediatric heart failure population has a limited history especially for infants, and neonates. It has been increasingly recognized that there is a rapidly expanding population of children diagnosed and living with heart failure. This expanding population has resulted in increasing numbers of children with medically resistant end-stage heart failure. The traditional therapy for these children has been heart transplantation. However, children with heart failure unlike adults do not have symptoms until they present with end-stage heart failure and therefore, cannot safely wait for transplantation. Many of these children were bridged to heart transplantation utilizing extracorporeal membranous oxygenation as a bridge to transplant which has yielded poor results. As such, industry, clinicians, and the government have refocused interest in developing increasing numbers of MCS options for children living with heart failure as a bridge to transplantation and as a chronic therapy. In this review, we discuss MCS options for short and long-term support that are currently available for infants and children with end-stage heart failure.

Study of a centrifugal blood pump in a mock loop system

An implantable centrifugal blood pump (ICBP) is being developed to be used as a ventricular assist device (VAD) in patients with severe cardiovascular diseases. The ICBP system is composed of a centrifugal pump, a motor, a controller, and a power supply. The electricity source provides power to the controller and to a motor that moves the pump's rotor through magnetic coupling. The centrifugal pump is composed of four parts: external conical house, external base, impeller, and impeller base. The rotor is supported by a pivot bearing system, and its impeller base is responsible for sheltering four permanent magnets. A hybrid cardiovascular simulator (HCS) was used to evaluate the ICBP's performance. A heart failure (HF) (when the heart increases beat frequency to compensate for decrease in blood flow) was simulated in the HCS. The main objective of this work is to analyze changes in physiological parameters such as cardiac output, blood pressure, and heart rate in three situations: healthy heart, HF, and HF with left circulatory assistance by ICBP. The results showed that parameters such as aortic pressure and cardiac output affected by the HF situation returned to normal values when the ICBP was connected to the HCS. In conclusion, the test results showed satisfactory performance for the ICBP as a VAD.

Fulminant myocarditis

Myocarditis is most often caused by a viral infection. Less common causes include other infectious agents and autoimmune diseases. Fulminant myocarditis is an unusual complication with a rapidly progressive course resulting in severe heart failure and cardiogenic shock. Fulminant myocarditis should be treated with full supportive care, using aggressive pharmacologic therapy and mechanical circulatory support, because significant improvement in left ventricular function will often occur. Cardiac transplantation is required in a small minority of patients. Cardiac magnetic resonance imaging is becoming a frequently used modality to aid in the diagnosis of myocarditis.

Heart transplantation with or without prior mechanical circulatory support in adults with congenital heart disease

OBJECTIVES

Recent analyses establish that heart transplantation is increasing among adults with congenital heart disease (ACHD), but the effects of pretransplant mechanical circulatory support (MCS) on perioperative and post-transplant outcomes have not been examined in the ACHD population.

METHODS

Scientific Registry of Transplant Recipients data on all adult heart transplants from September 1987 to September 2012 (n = 47 160) were classified based on primary diagnosis codes as CHD or non-CHD and MCS or non-MCS. Demographic, procedural, outcome and survival variables were compared between MCS and non-MCS ACHD patient groups.

RESULTS

MCS was used in 83 (6.8%) ACHD patients compared with 8625 (18.8%) patients without CHD (P < 0.001). MCS as a fraction of ACHD transplants increased over time (P = 0.002). MCS patients spent more time on the wait list, had a higher baseline serum creatinine and were more likely to be male, status 1A, hospitalized, in the ICU and/or on a ventilator prior to transplant. However, MCS patients experienced equivalent short-term survival (30-day mortality = 10.8% in MCS vs 13.5% in non-MCS, P = 0.62) and overall survival by Kaplan-Meier analysis (P = 0.57). MCS patients had a longer post-transplant length of stay and were more likely to be transfused, but otherwise had no significant differences in adverse outcomes.

CONCLUSIONS

MCS is less commonly used in adult CHD patients compared with all patients undergoing heart transplant, but has been increasing over time. Within the ACHD population, patients with MCS have a higher risk profile, but except for increased transfusion rate and longer length of stay, do not experience less favourable post-transplant outcomes.

A history of devices as an alternative to heart transplantation

The rapid evolution of mechanical circulatory support (MCS) has extended survival and improved quality of life for patients suffering from the most advanced heart failure (HF). Survival at one year after placement of a left ventricular assist device exceeds 80%. MCS and transplant have developed in counterpoint to each other. Patients with HF now have a meaningful option for lifelong support even if they are not candidates for heart transplant. As the profiles of MCS recipients change and the next generation of devices emerges, new challenges and opportunities await physicians caring for patients with cardiac failure.

Continuous monitoring of cardiac rhythms in left ventricular assist device patients

Monitoring of cardiac rhythms is of major importance in the treatment of heart failure patients with left ventricular assist devices (LVADs) implanted. A continuous surveillance of these rhythms could improve out-of-hospital care in these patients. The aim of this study was to investigate cardiac rhythms using available pump data only. Datasets (n = 141) obtained in the normal ward, in the intensive care unit, and during bicycle ergometry were analyzed in 11 recipients of a continuous flow LVAD (59.1 ± 9.7 years; male 82%). Tachograms and arrhythmic patterns derived from the pump flow waveform, and a simultaneously recorded ECG were compared, as well as heart rate variability parameters such as: the average heart beat duration (RR interval), the standard deviation of the beat duration (SDNN), the root-mean-square of the difference of successive beat durations (RMSSD), and the number of pairs of adjacent beat duration differing by >50 ms divided by the number of all beats (pNN50). A very good agreement of cardiac rhythm parameters from the pump flow compared with ECG was found. Tachycardia, atrial fibrillation, and extrasystoles could be accurately identified from the tachograms derived from the pump flow. Also, Bland-Altman analysis comparing pump flow with ECG indicated a very small difference in average RR interval of 0.3 ± 1.0 ms, in SSDN of 0.5 ± 2.7 ms, in RMSSD of 1.0 ± 5.6 ms, and in pNN50 of 0.3 ± 1.0%. Continuous monitoring of cardiac rhythms from available pump data is possible. It has the potential to reduce the out-of-hospital diagnostic burden and to permit a more efficient adjustment of the level of mechanical support.

Disseminated malignancy after extracorporeal life support and left ventricular assist device, diagnosed by left ventricular apical core biopsy

The left ventricular apical core biopsy performed during implantation of a left ventricular assist device (VAD) is a well-known diagnostic procedure in confirming cardiomyopathies leading to end-stage heart failure. We describe a patient in whom disseminated malignancy was revealed by means of the apical core biopsy after extracorporeal life support and left ventricular assist device implantation as a bridge to transplantation. This case emphasizes the importance of thorough oncological screening before VAD implantation and the possible consequences of circulating tumour cells in this device-assisted circulation.

In vitro evaluation of aortic insufficiency with a rotary left ventricular assist device

Aortic insufficiency (AI) is usually repaired prior to rotary blood pump (RBP) implantation but can develop during support due, in part, to the sustained RBP-induced high pressure gradient across the aortic valve. Repair of the aortic valve before or during RBP support predisposes these critically ill patients to even higher risks. This study used an in vitro mock circulation loop to identify the severity of AI and/or left heart failure (LHF) that might benefit from valve repair while investigating RBP operating strategies to reduce the hemodynamic influence of AI. Reproduction of AI with RBP-supported LHF reduced device efficiency, particularly in the more severe cases of AI and LHF. The requirement for repair or closure of the aortic valve was demonstrated in all conditions other than those with only mild AI. When a sinusoidal RBP speed pulse was induced, small changes in systemic flow rate and regurgitant volume were observed with all degrees of AI. Variation of the pulse phase delay only resulted in minor changes to systemic flow rate, with a maximum difference of 0.17 L/min. Although the clinical implications of these small changes may be insignificant, changes in systemic flow rate and transvalvular pressure were shown when the sinusoidal RBP speed pulse was applied with no AI. In these cases, transvalvular pressure was reduced by up to 8% through sinusoidal copulsation of the RBP, which may prevent or delay the onset of AI. This in vitro study suggests that surgical intervention is required with moderate or worse AI and that RBP operating strategies should be further explored to delay the onset and reduce the harmful effects of AI.

Bovine model of chronic ischemic cardiomyopathy: implications for ventricular assist device research

Ventricular assist devices (VADs) have emerged as a successful treatment option for advanced heart failure. The objective of this study was to develop a clinically relevant model of chronic ischemic cardiomyopathy to investigate functional, histological, and molecular changes during mechanical circulatory support. In calves (n = 17, 94 ± 7 kg), 90 μm microspheres were injected percutaneously into the left coronary artery. Serial echocardiography was performed weekly to evaluate cardiac function. Sixty days after coronary microembolization, a terminal study was performed via thoracotomy to measure hemodynamics. Regional myocardial and end-organ blood flows were quantified with 15-μm fluorescent-labeled microspheres. Myocardial fibrosis, myocyte size, and myocardial apoptosis were quantified with histological stains. Eleven animals survived coronary microembolization and exhibited clinical and statistically significant echocardiographic and hemodynamic signs of severe systolic dysfunction. Statistically significant decreases in regional myocardial blood flow and increases in myocardial fibrosis, myocyte size, total myocardial apoptosis, and cardiac myocyte-specific apoptosis were observed. End-organ hypoperfusion was observed. Coronary microembolization induced stable and reproducible chronic left ventricular failure in calves. The anatomical size and physiology of the bovine heart and thorax are appropriate to study novel interventions for the clinical management of heart failure. This model is an appropriate physiological substrate in which to test VAD and adjunctive biological therapies.

Fundus fluorescein angiographic findings in patients who underwent ventricular assist device implantation

Disruption of microcirculation in various tissues as a result of deformed blood rheology due to ventricular assist device (VAD) implantation causes novel arteriovenous malformations. Capillary disturbances and related vascular leakage in the retina and choroidea may also be seen in patients supported by VADs. We aimed to evaluate retinal vasculature deteriorations after VAD implantation. The charts of 17 patients who underwent VAD implantation surgery for the treatment of end-stage heart failure were retrospectively reviewed. Eight cases (47.1%) underwent pulsatile pump implantation (Berlin Heart EXCOR, Berlin Heart Mediprodukt GmbH, Berlin, Germany); however, nine cases (52.9%) had continuous-flow pump using centrifugal design (HeartWare, HeartWare Inc., Miramar, FL, USA). Study participants were selected among the patients who had survived with a VAD for at least 6 months, and results of detailed ophthalmologic examinations including optic coherence tomography (OCT) and fundus fluorescein angiography (FA) were documented. All of the 17 patients were male, with a mean age of 48.5 ± 14.8 years (15-67 years). Detailed ophthalmologic examinations including the evaluation of retinal vascular deteriorations via FA were performed at a mean of 11.8 ± 3.7 months of follow-up (6-18 months). Mean best-corrected visual acuity and intraocular pressure were found as logMAR 0.02 ± 0.08 and 14.6 ± 1.9 mm Hg, respectively in the study population. Dilated fundoscopy revealed severe focal arteriolar narrowing in two patients (11.8%), and arteriovenous crossing changes in four patients (23.5%); however, no pathological alteration was present in macular OCT scans. In patients with continuous-flow blood pumps, mean arm-retina circulation time (ARCT) and arteriovenous transit time (AVTT) were found to be 16.8 ± 3.0 and 12.4 ± 6.2 s, respectively; whereas those with pulsatile-flow blood pumps were found to be 17.4 ± 3.6 and 14.0 ± 2.1 s in patients (P=0.526 and P=0.356, respectively). FA also revealed a tendency for increased frequency of dye leakage from the optic disc in our study population. Except for remarkable delays in both ARCT and AVTT as well as a tendency for increased frequency of dye leakage from the optic disc, ophthalmologic evaluations revealed no other significant pathology or vascular deterioration in the retina that could be attributed to artificial heart systems.

Percutaneous Circulatory Assist Devices for Right Ventricular Failure

Heart failure is a major cause of global morbidity and mortality affecting nearly 24 million individuals worldwide. Although the importance of right ventricular (RV) function has become more apparent over the past few decades, few therapies specifically target RV failure. Over the past 3 decades, significant advances in percutaneously delivered circulatory support devices has led to the recent development of devices specifically designed for RV failure. In this review, RV pathophysiology, device options, and clinical data exploring the utility of percutaneous RV support devices are discussed.

Intensive care of the pediatric ventricular assist device patient

Utilization of ventricular assist devices (VADs) in children is increasing, as is the complexity of patients supported. We review the intensive care management of pediatric patients with VAD in the perioperative and rehabilitation phases, highlighting the technical aspects and physiology of VADs which impact care. Indications for VAD placement and the preoperative assessment of risk are discussed. Specific aspects of postoperative and long-term care including device troubleshooting, hemostasis and anticoagulation, support of the right ventricle, incidence and prevention of neurologic injury, and other complications are reviewed.

Clinicians' attitudes regarding withdrawal of left ventricular assist devices in patients approaching the end of life

AIMS

Left ventricular assist devices (LVADs) are implanted to support the circulation of patients with advanced heart failure. Patients approaching death, or their surrogates, may request withdrawal of LVAD support. We sought to study the attitudes and practices of heart failure clinicians regarding withdrawal of LVAD support in patients approaching death.

METHODS AND RESULTS

Using internet-based and secure methods, we surveyed members of the European Society of Cardiology-Heart Failure Association (ESC-HFA), the International Society for Heart and Lung Transplantation (ISHLT), and the Heart Failure Society of America (HFSA) to assess their attitudes and practices regarding LVAD withdrawal for patients approaching death. The results indicated that clinicians have varied attitudes and practices regarding withdrawing LVAD support in these patients. Furthermore, ESC-HFA clinicians (primarily European) and ISHLT and HFSA clinicians (primarily North American) differed in their attitudes and practices regarding withdrawal of LVAD support, particularly its ethical and legal permissibility. For example, more European clinicians than North American clinicians regarded withdrawing LVAD support as a form of euthanasia.

CONCLUSION

Opinions and level of comfort with LVAD withdrawal vary among clinicians. Clinicians should be aware of suggested approaches or guidelines for managing requests for withdrawal of LVAD therapy.

The effect of long-term left ventricular assist device support on myocardial sympathetic activity in patients with non-ischaemic dilated cardiomyopathy

AIMS

Dilated cardiomyopathy (DCM) patients have abundant levels of norepinephrine secondary to failure of the norepinephrine transporter uptake mechanism. Little is known about the effects of an LV assist device (LVAD) on cardiac sympathetic innervations and norepinephrine transporter dysfunction. This study examines the effects of continuous-flow HeartMate II LVAD on cardiac sympathetic innervations using [(123)I]metaiodobenzylguanidine ([(123)I]MIBG) nuclear imaging.

METHODS AND RESULTS

After injecting 431 ± 21 MBq of [(123)I]MIBG, planar scintigraphy was performed at 15 min and 4 h in 14 consecutive non-diabetic non-ischaemic DCM patients. Scans were executed early post-LVAD implantation (T1) and prior to either device explantation for myocardial recovery or transplant listing (T2). [(123)I]MIBG measured parameters included early and delayed heart-mediastinum (H/M) ratios and washout rate (W/O). Catecholamine levels were measured using liquid chromatography-mass spectrometry. Following 208.4 ± 85.5 days of LVAD support, both early and delayed H/M ratios increased by 42.1% (P < 0.001) and 54.7% (P < 0.001), respectively. The W/O rate decreased by 46% (P = 0.003). Plasma norepinephrine, epinephrine, and dopamine decreased significantly in correlation with [(123)I]MIBG parameters. Ten patients had recovered and had their device explanted as they had demonstrated a higher percentage change in delayed H/M ratio, W/O rate, and norepinephrine levels. Linear regression analysis revealed a strong correlation between percentage changes in both norepinephrine and epinephrine and myocardial recovery.

CONCLUSION

Combination therapy with LVAD and drug resulted in enhancement of [(123)I]MIBG uptake in DCM patients.

Neurological complications during pulsatile ventricular assistance with the Berlin Heart EXCOR in children: incidence and risk factors

The aim of this study is to describe the incidence of brain injury (BI) in children with end-stage cardiac failure who were supported with the Berlin Heart EXCOR ventricular assist device (VAD) as a bridge to heart transplantation. Between January 2002 and January 2012, all patients <18 years of age who underwent the implantation of the Berlin Heart EXCOR at Bambino Gesú Children's Hospital were included. A total of 25 patients were included in this study. Median age and weight at implantation were 22.4 months (range 3.6-154.2) and 10 kg (range 4.5-36), respectively. Diagnosis included cardiomyopathy (n = 20) and congenital heart disease (n = 5). Eleven patients received atrial cannulation. Nine patients underwent biventricular assist device support. Seven patients underwent extracorporeal membrane oxygenation before the implantation of the EXCOR VAD. Median duration of VAD support was 51 days (range 2-167). Nine patients had evidence of acute BI including intracranial hemorrhage (n = 5) and cerebral ischemia (n = 4). Freedom from BI at 30, 60, and 90 days from VAD implantation was 80.7, 69.9, and 43.3%, respectively. Weight <10 kg at implantation was significantly associated with BI. BI is a frequent complication among children supported with EXCOR VAD and is associated with lower weight at implantation. However, our data do not support the association between size and BI. Future prospective multicenter studies are warranted to further help understand the etiology and the impact of BI and to improve functional outcomes for children undergoing EXCOR VAD mechanical support.

Use of centrifugal left ventricular assist device as a bridge to candidacy in severe heart failure with secondary pulmonary hypertension

OBJECTIVES

Raised pulmonary artery pressure (PAP), trans-pulmonary gradient (TPG) and pulmonary vascular resistance (PVR) are risk factors for poor outcomes after heart transplant in patients with secondary pulmonary hypertension (PH) and may contraindicate transplant. Unloading of the left ventricle with an implantable left ventricular assist device (LVAD) may reverse these pulmonary vascular changes. We studied the effect of implanting centrifugal LVADs in a cohort of patients with secondary PH as a bridge to candidacy.

METHODS

Pulmonary haemodynamics on patients implanted with centrifugal LVADs at a single unit between May 2005 and December 2010 were retrospectively reviewed.

RESULTS

Twenty-nine patients were implanted with centrifugal LVADs (eight HeartWare ventricular assist device (HVAD), HeartWare International, USA and 21 VentrAssist, Ventracor Ltd., Australia). Seventeen were ineligible for transplant by virtue of high TPG/PVR. All the patients were optimized with inotrope/balloon pump followed by LVAD insertion. Four required temporary right VAD support. Thirty-day mortality post-LVAD was 3.4% (1 of 29) with a 1-year survival of 85.7% (24 of 28). Thirteen patients have been transplanted to date: 30-day mortality was 7.7% (1 of 13) and 1-year survival was 91% (10 of 11). Baseline and post-VAD pulmonary haemodynamics were significantly improved: systolic PAP (mmHg), mean PAP, TPG (mmHg) of 57 ± 9.5, 42 ± 4.4 and 14 ± 3.9 reduced to 32 ± 7.5, 18 ± 5.5 and 9 ± 3.3, respectively. PVR reduced from 5 ± 1.5 to 2.1 ± 0.5 Wood units (P < 0.05).

CONCLUSIONS

In selected heart failure patients with secondary PH, use of centrifugal LVAD results in significant reductions in PAP, TPG and PVR, which are observed within 1 month, reaching a nadir by 3 months. Such patients bridged to candidacy have post-transplant survival comparable with those having a heart transplant as primary treatment.

Implantation of the continuous flow HeartWare® left ventricular assist device

Recent outstanding clinical advances with new mechanical circulatory systems have led to additional strategies in the treatment of end-stage heart failure. Heart transplantation can be postponed and for certain patients even replaced by smaller implantable left ventricular assist devices (LVADs). Mechanical support of the failing left ventricle enables appropriate haemodynamic stabilization and recovery of secondary organ failure, often seen in these severely ill patients. These new devices may be of great help to bridge patients until a suitable cardiac allograft is available but are also discussed as definitive treatment for patients who do not qualify for transplantation. Main indications for LVAD implantation are bridge to recovery, bridge to transplantation or destination therapy. An LVAD may be an important tool for patients with an expected prolonged period on the waiting list, for instance those with blood group O or B, with high or low body weight and those with potentially reversible secondary organ failure and pulmonary artery hypertension. However, LVAD implantation means an additional heart operation with inherent perioperative risks and complications during the waiting period. Finally, cardiac transplantation in patients with prior implantation of an LVAD represents a surgical challenge. The care of patients after the implantation of miniaturized LVADs, such as the HeartWare® system, seems to be easier than following pulsatile devices. The explantation of such devices at the time of transplantation is technically more comfortable than after HeartMate II implantation.

Mechanical circulatory support of the critically ill child awaiting heart transplantation

The majority of children awaiting heart transplantation require inotropic support, mechanical ventilation, and/or extracorporeal membrane oxygenation (ECMO) support. Unfortunately, due to the limited pool of organs, many of these children do not survive to transplant. Mechanical circulatory support of the failing heart in pediatrics is a new and rapidly developing field world-wide. It is utilized in children with acute congestive heart failure associated with congenital heart disease, cardiomyopathy, and myocarditis, both as a bridge to transplantation and as a bridge to myocardial recovery. The current arsenal of mechanical assist devices available for children is limited to ECMO, intra-aortic balloon counterpulsation, centrifugal pump ventricular assist devices, the DeBakey ventricular assist device Child; the Thoratec ventricular assist device; and the Berlin Heart. In the spring of 2004, five contracts were awarded by the National Heart, Lung and Blood Institute to support preclinical development for a range of pediatric ventricular assist devices and similar circulatory support systems. The support of early development efforts provided by this program is expected to yield several devices that will be ready for clinical trials within the next few years. Our work reviews the current international experience with mechanical circulatory support in children and summarizes our own experience since 2005 with the Berlin Heart, comparing the indications for use, length of support, and outcome between these modalities.

Ventricular assist devices in pediatrics

The implantation of a mechanical circulatory device for end-stage ventricular failure is a possible therapeutic approach in adult and pediatric cardiac surgery and cardiology. The aim of this article is to present mechanical circulatory assist devices used in infants and children with special emphasis on extracorporeal membrane oxygenation, Berlin Heart assist device, centrifugal pump and Medos assist device. The success of long-term support with implantable ventricular assist devices in adults and children has led to their increasing use as a bridge to transplantation in patients with otherwise non-treatable left ventricular failure, by transforming a terminal phase heart condition into a treatable cardiopathy. Such therapy allows rehabilitation of patients before elective cardiac transplantation (by removing contraindications to transplantation mainly represented by organ impairment) or acting as a bridge to recovery of the native left ventricular function (depending on underlying cardiac disease). Treatment may also involve permanent device implantation when cardiac transplantation is contraindicated. Indications for the implantation of assisted circulation include all states of cardiac failure that are reversible within a variable period of time or that require heart transplantation. This article will address the current status of ventricular assist devices by examining historical aspects of its development, current technical issues and clinical features of pediatric ventricular assist devices, including indications and contraindications for support.