Regenerative therapies in young hearts with structural or congenital heart disease

Pediatric Chronic Heart Failure: Age-Specific Considerations of Medical Therapy

Chronic heart failure (CHF) is a rare entity in children but carries a burden of high mortality and morbidity. Medical treatment of pediatric CHF is largely based on guidelines for the adult population. In contrast to adults, evidence for the efficacy of medications in treating CHF in children is sparse. This may be due to the difficulty of conducting high-powered studies in children or to true differences in the mechanisms of CHF pathophysiology. Recent observations suggest that CHF in children differs from adults at the molecular and cellular levels. Different pathways are involved, leading to less fibrosis and hypertrophy than in adults, with potential implications for therapy. The main pathophysiological goals of medical treatment of pediatric CHF due to systemic left ventricular dysfunction are discussed in this review. These include preload and afterload optimization, diminishing cardiomyocyte apoptosis and necrosis as well as interstitial fibrosis, and optimizing myocardial oxygen consumption. The pediatric myocardium should be provided with optimal conditions to achieve its regenerative potential. The cornerstones of medical CHF therapy are angiotensin converting enzyme inhibitors (ACEI), beta blockers and mineralocorticoid receptor antagonists. There are potential benefits of tissue ACEI and ?1-selective beta blockers in children. Angiotensin receptor blockers are an alternative to ACEI and their slightly different mechanism of action may confer certain advantages and disadvantages. Diuretics are employed to achieve a euvolemic state. Digoxin is used more frequently in children than in adults. Promising new drugs already routinely used in adults include angiotensin receptor-neprilysin inhibitors and sodium-glucose contransporter 2 inhibitors. Key words: Pediatric heart failure, Heart failure with reduced ejection fraction (HFrEF), ACE inhibitor, Beta blocker, Digoxin.

Cardiac tissue engineering for the treatment of hypoplastic left heart syndrome (HLHS)

Hypoplastic left heart syndrome (HLHS) is a deadly congenital heart disease that arises when the left ventricle and outflow tract fail to develop appropriately, inhibiting the adequate perfusion of the rest of the body. Historically, this disease has been treated via a series of surgeries that allows the heart to use a single ventricle. These surgeries are often a palliative measure, and heart transplantation is the only definitive therapy that exists for this condition. It has been hypothesized that stem cell-based regenerative therapies could have a role in promoting cardiac tissue regeneration in HLHS patients who are undergoing palliative surgery. Several clinical trials have demonstrated that introducing pluripotent cells into the heart is safe, feasible, and capable of improving right ventricular ejection fraction (RVEF). However, while these approaches show great promise, there is still room for development. There is a substantial body of pre-clinical work that is focused on generating increasingly large and complex pieces of cardiac tissue in the form of cardiac patches, with the idea that these could be used to rebuild and strengthen the heart in a robust and long-lasting manner. In total, stem cell-based therapies have much to offer when it comes to improving the treatment of HLHS.

Early Presentation of Patients with Abnormal Origin of Left Coronary Artery from the Pulmonary Artery is a Predictor of Poor Mid-term Outcomes

Abnormal origin of left coronary artery from the pulmonary artery (ALCAPA) is one of the most common causes of myocardial ischemia and infarction in childhood. This study aimed to determine the correlation between age at clinical presentation, level of ventricular dysfunction, and post-repair outcomes. This is retrospective study from 1993 to 2018 including thirty-one patients. The study cohort was divided into two groups according to age (< 6 months, > 6 months). The significance level was set at p 0.05.The median follow-up time was 72 [24-168] months. Median age was 4.7 [2.3-16] months. Median weight was 6.2 [4.3-9] kg. There was severe left ventricular (LV) dysfunction (ejection fraction < 35%) in 64.5% of patients. Mitral regurgitation (MR) was moderate to severe in 13 patients (41.9%). Two patients (6.4%) required extracorporeal membrane oxygenation (ECMO) support before surgery and 6 (19.4%) after correction. Age < 6 months was significantly associated with severe clinical presentation, severe LV dysfunction, delayed sternal closure, prolonged respiratory mechanical support, and prolonged length of ICU stay (p = 0.024, p = 0.042, p = 0.002, p = 0.042, p = 0.022, respectively). After surgery, ejection fraction improved to a median of 57% [50.7-60.5]. MR regressed in 12 patients (92.3%). Mortality rate after surgery was 9.7%. All patients were free from reoperation at the last follow-up. Young age at diagnosis was significantly associated with a more severe clinical presentation and poorer outcomes. After re-establishment of a two-coronary circulation, both ventricular function and MR tend to normalize over time regardless of age at repair.

Heart failure therapy based on interventricular mechanics and cardio-vascular communications

The heart should not be divided in right and left, whether in health nor in disease. However, the morphological and functional differences between the right and left ventricle should be known and the impact of the ventricle's position considered. Further, the parameters beyond heart rate, contractility, pre- and afterload guaranteeing a sufficient systemic cardiac output have to be integrated in therapeutic measures; preferentially the influence of interventricular mechanics. Despite of recent developments of specific drug therapies, heart failure is associated with a high rate of morbidity and mortality in children. During the progression of heart failure, pulmonary vascular disease is the consequence or the reason for further failing. Clinical symptoms are associated with congestion and low cardiac output at rest or exercise. Improved understanding of the pathophysiological mechanisms particularly of ventricular failure has resulted in the development of innovative therapies that target atrial/ventricular/arterial interactions. Recent advances in interventional and surgical approaches provide promising new strategies to deal with right and left ventricular deterioration. These techniques may delay listing for heart and (heart-) lung transplantation or even make redundant in individual cases. The beneficial effects of these ventricular interaction strategies are mainly based on the mechanics of the interventricular septum and improvement of systolic and diastolic ventricular performance.

Cardiosphere-derived exosomal microRNAs for myocardial repair in pediatric dilated cardiomyopathy

Although cardiosphere-derived cells (CDCs) improve cardiac function and outcomes in patients with single ventricle physiology, little is known about their safety and therapeutic benefit in children with dilated cardiomyopathy (DCM). We aimed to determine the safety and efficacy of CDCs in a porcine model of DCM and translate the preclinical results into this patient population. A swine model of DCM using intracoronary injection of microspheres created cardiac dysfunction. Forty pigs were randomized as preclinical validation of the delivery method and CDC doses, and CDC-secreted exosome (CDCex)-mediated cardiac repair was analyzed. A phase 1 safety cohort enrolled five pediatric patients with DCM and reduced ejection fraction to receive CDC infusion. The primary endpoint was to assess safety, and the secondary outcome measure was change in cardiac function. Improved cardiac function and reduced myocardial fibrosis were noted in animals treated with CDCs compared with placebo. These functional benefits were mediated via CDCex that were highly enriched with proangiogenic and cardioprotective microRNAs (miRNAs), whereas isolated CDCex did not recapitulate these reparative effects. One-year follow-up of safety lead-in stage was completed with favorable profile and preliminary efficacy outcomes. Increased CDCex-derived miR-146a-5p expression was associated with the reduction in myocardial fibrosis via suppression of proinflammatory cytokines and transcripts. Collectively, intracoronary CDC administration is safe and improves cardiac function through CDCex in a porcine model of DCM. The safety lead-in results in patients provide a translational framework for further studies of randomized trials and CDCex-derived miRNAs as potential paracrine mediators underlying this therapeutic strategy.

From Safety to Benefit in Cell Delivery During Surgical Repair of Ebstein Anomaly: Initial Results

BACKGROUND

The objective of this study is to assess the safety and early impact of intramyocardial delivery of autologous bone marrow-derived mononuclear cells (BM-MNC) at time of surgical Ebstein repair.

METHODS

Patients with Ebstein anomaly (ages 6 months to 30 years) scheduled to undergo repair of the tricuspid valve were eligible to participate in this open-label, non-randomized phase I clinical trial. BM-MNC target dose was 1-3 million cells/kg. Ten patients have undergone surgical intervention and cell delivery to the right ventricle (RV) and completed 6-month follow-up.

RESULTS

All patients underwent surgical tricuspid valve repair and uneventful BM-MNC delivery; there were no ventricular arrhythmias and no adverse events related to study product or delivery. Echocardiographic RV myocardial performance index improved and RV fractional area change showed an initial decline and then through study follow-up. There was no evidence of delayed myocardial enhancement or regional wall motion abnormalities at injection sites on 6-month follow-up magnetic resonance imaging.

CONCLUSIONS

Intramyocardial delivery of BM-MNC after surgical repair in Ebstein anomaly can be performed safely. Echocardiography variables suggest a positive impact of cell delivery on the RV myocardium with improvements in both RV size and wall motion over time. Additional follow-up and comparison to control groups are required to better characterize the impact of cell therapy on the myopathic RV in Ebstein anomaly.

Pulmonary Artery Banding for Ventricular Rehabilitation in Infants With Dilated Cardiomyopathy: Early Results in a Single-Center Experience

Background: Pulmonary artery banding (PAB) is reported as an innovative strategy for children with end-stage heart failure (ESHF) to bridge to transplantation or recovery. We report our early experience with PAB to evaluate outcomes, indications, and limitations. Materials and Methods: This is a single-center prospective clinical study, including infants and children admitted for ESHF owing to dilated cardiomyopathy (DCM) with preserved right ventricular function after failure of maximal conventional therapy. All patients underwent perioperative anticongestive medical therapy with ACE inhibitor, beta blocker, and spironolactone. Post-operatively, all patients underwent echocardiographic follow-up to assess myocardial recovery. Results: We selected five patients (four males) who underwent PAB at a median age of 8.6 months (range 3.9-42.2 months), with preoperative ejection fraction (EF) <30%. Sternal closure was delayed in all. One patient did not improve after PAB and underwent Berlin Heart implantation after 33 days, followed by heart transplant after 13 months. Four patients were discharged home on full anticongestive therapy. However, 2 months after discharge, one patient experienced severe acute heart failure secondary to pneumonia, which required mechanical circulatory support, and the patient underwent a successful heart transplant after 21 days. The remaining three patients are doing well at home, 22.4, 16.9, and 15.4 months after PAB. They all underwent elective percutaneous de-banding, 18.5, 4.8, and 10.7 months after PAB. EF increased from 17.7 ± 8.5% to 63.3 ± 7.6% (p = 0.03), and they have all been delisted. Conclusion: Use of PAB may be an effective alternative to mechanical support in selected infants for bridging to transplant or recovery. Better results seem to occur in patients aged <12 months. Further experience and research are required to identify responders and non-responders to this approach.