Clinical and Molecular Comparison of Pediatric and Adult Reverse Remodeling With Ventricular Assist Devices

Biology of myocardial recovery in advanced heart failure with long-term mechanical support

Cardiac remodeling is an adaptive, compensatory biological process following an initial insult to the myocardium that gradually becomes maladaptive and causes clinical deterioration and chronic heart failure (HF). This biological process involves several pathophysiological adaptations at the genetic, molecular, cellular, and tissue levels. A growing body of clinical and translational investigations demonstrated that cardiac remodeling and chronic HF does not invariably result in a static, end-stage phenotype but can be at least partially reversed. One of the paradigms which shed some additional light on the breadth and limits of myocardial elasticity and plasticity is long term mechanical circulatory support (MCS) in advanced HF pediatric and adult patients. MCS by providing (a) ventricular mechanical unloading and (b) effective hemodynamic support to the periphery results in functional, structural, cellular and molecular changes, known as cardiac reverse remodeling. Herein, we analyze and synthesize the advances in our understanding of the biology of MCS-mediated reverse remodeling and myocardial recovery. The MCS investigational setting offers access to human tissue, providing an unparalleled opportunity in cardiovascular medicine to perform in-depth characterizations of myocardial biology and the associated molecular, cellular, and structural recovery signatures. These human tissue findings have triggered and effectively fueled a "bedside to bench and back" approach through a variety of knockout, inhibition or overexpression mechanistic investigations in vitro and in vivo using small animal models. These follow-up translational and basic science studies leveraging human tissue findings have unveiled mechanistic myocardial recovery pathways which are currently undergoing further testing for potential therapeutic drug development. Essentially, the field is advancing by extending the lessons learned from the MCS cardiac recovery investigational setting to develop therapies applicable to the greater, not end-stage, HF population. This review article focuses on the biological aspects of the MCS-mediated myocardial recovery and together with its companion review article, focused on the clinical aspects, they aim to provide a useful framework for clinicians and investigators.

Pathophysiology and molecular signalling in pediatric heart failure and VAD therapy

Heart Failure (HF) is a progressive clinical syndrome characterized by molecular and structural abnormalities that result in impaired ventricular filling and a reduced blood ejection. In pediatric patients, HF represents an important cause of morbidity and mortality, but underlying cause, presentation and disease course remains unclear in many cases. It is evident that a child is not a "small adult" and findings are not comparable. The adoption of a standardized clinical and surgical tools as well as increased biomolecular research and therapeutic trials targeting pediatric patients with HF would greatly improve the management of this special class of patients. This review examines the most current information about the pathophysiology and molecular mechanisms related to HF in children to identify gaps in our knowledge base to further improve clinical care and outcomes.

Bridge to recovery in children on ventricular assist devices-protocol, predictors of recovery, and long-term follow-up

BACKGROUND

The majority of children supported with ventricular assist devices (VADs) are bridged to heart transplantation. Although bridge to recovery has been reported, low recovery patient numbers has precluded systematic analysis. The aim of this study was to delineate recovery rates and predictors of recovery and to report on long-term follow-up after VAD explantation in children.

METHODS

Children bridged to recovery at our institution from January 1990 to May 2016 were compared with a non-recovery cohort. Clinical and echocardiographic data before and at pump stoppages and after VAD explantation were analyzed. Kaplan‒Meier estimates of event-free survival, defined as freedom from death or transplantation after VAD removal, were determined.

RESULTS

One hundred forty-nine children (median age 5.8 years) were identified. Of these, 65.2% had cardiomyopathy, 9.4% had myocarditis, and 24.8% had congenital heart disease. The overall recovery rate was 14.2%, and was 7.1% in patients with dilated cardiomyopathy. Predictors of recovery were age <2 years (recovery rate 27.8%, odds ratio [OR] 5.64, 95% confidence interval [CI] 2.0 to 16.6) and diagnosis of myocarditis (rate 57.1%; OR 17.56, 95% CI 4.6 to 67.4). After a median follow-up of 10.8 years, 15 patients (83.3%) were in Functional Class I and 3 (16.7%) in were in Class II. Mean left ventricular ejection fraction was 53% (range 28% to 64%). Ten- and 15-year event-free survival rates were both 84.1 ± 8.4%.

CONCLUSIONS

Children <2 years of age and those diagnosed with myocarditis have the highest probability of recovery. Long-term survival after weaning from the VAD was better than after heart transplantation, as demonstrated in the excellent long-term stability of ejection fraction and functional class.

Evolution of Biventricular Loading Condition in Pediatric LVAD Patient: A Prospective and Observational Study

The aim of this study was to describe the echocardiographic trend of left ventricular (LV) and right ventricular (RV) function after implantation of a pulsatile flow left ventricular assist device (LVAD) in children. From 2013 to 2016, we prospectively evaluated 13 consecutive pediatric Berlin Heart EXCOR LVAD patients. Clinical and echocardiographic data were collected at baseline, within 24 h after implantation and monthly until LVAD explant. Median age and weight at the implantation was 8 (4-23) months and 5 (4.6-8.3) kg at the time of implantation, respectively. All were affected by dilated cardiomyopathy. Average LVAD support time was 226.2 ± 121.2 days. Nine (70%) were transplanted, 4 (30%) died. LV end-systolic and end-diastolic volumes were reduced until the follow up of two months (P = 0.019 and P = 0.001). A progressive increase in RV dimensions was observed. After 4 months of follow up, RV fractional area change worsening was statistically related with the deterioration of LV unloading (P = 0.0036). Four patients needed prolonged inotropic support for RV failure. Pulsatile LVAD in pediatrics is followed by an early and mid-term LV unloading, as expressed by a decrease in LV volumes and diameters at echocardiogram. The effects of unloading do not remain stable at long term follow up. RV function improved in the acute phase, but a progressive dilatation of RV was noted over time. In some patients, RV failure might lead to the need of an increase of inotropic support at long term follow up.

Titanium Plug Closure after HeartWare Ventricular Assist Device Explantation in a 15-Year-Old Girl: First U.S. Experience

We describe the case of a teenage girl with anthracycline-induced cardiomyopathy who received a HeartWare ventricular assist device and underwent successful device explantation after cardiac recovery. During device support, the patient's cardiac function returned to normal. Twelve months after implantation, we explanted the device via repeat median sternotomy. To close the hole in the left ventricular apex and preserve the sewing ring in case future device support is needed, we used a German-manufactured titanium plug, developed specifically for this purpose. To our knowledge, this is the first use of this plug in the United States. The patient recovered uneventfully and was discharged from the hospital on postoperative day 11. Left ventricular biopsy specimens at explantation revealed the resolution of previous degenerative sarcomeric changes. Our patient did well clinically; however, recurrent late anthracycline cardiotoxicity might subsequently cause her cardiac function to deteriorate. In this event, our use of the titanium plug to preserve the left ventricular sewing ring would enable easier device replacement than would other explantation options.

Current Status of Pediatric Ventricular Assist Device Support

The last decade has witnessed significant advancement in the field of ventricular assist device (VAD) support. Although device options for pediatric patients were previously severely limited because of body size constraints, this frustrating situation has gradually been changing, owing to ongoing device miniaturization. Recognition of the superiority of VAD support compared with conventional extracorporeal membrane oxygenation support has spurred enthusiasm for VAD support in children. In this article, we discuss the current status of pediatric VAD support; where do we stand now and where will we be heading? Because this field is rapidly changing, it is anticipated that this article will provide a general overview of what is currently occurring in the field of pediatric VAD support.

Artificial Organs 2015: A Year in Review

In this Editor's Review, articles published in 2015 are organized by category and briefly summarized. We aim to provide a brief reflection of the currently available worldwide knowledge that is intended to advance and better human life while providing insight for continued application of technologies and methods of organ Replacement, Recovery, and Regeneration. As the official journal of The International Federation for Artificial Organs, The International Faculty for Artificial Organs, the International Society for Rotary Blood Pumps, the International Society for Pediatric Mechanical Cardiopulmonary Support, and the Vienna International Workshop on Functional Electrical Stimulation, Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. We take this time also to express our gratitude to our authors for providing their work to this journal. We offer our very special thanks to our reviewers who give so generously of their time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers, the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.