New devices for pediatric mechanical circulatory support

Impact of Pulsatile Flow Settings on Hemodynamic Energy Levels Using the Novel Diagonal Medos DP3 Pump in a Simulated Pediatric Extracorporeal Life Support System

Background:

The objective of this study was to evaluate the pump performance of the novel diagonal Medos Deltastream DP3 diagonal pump (MEDOS Medizintechnik AG, , Stolberg, Germany) under nonpulsatile to pulsatile mode with varying differential speed values in a simulated pediatric extracorporeal life support system.

Methods:

The experimental circuit consisted of a Medos Deltastream DP3 pump head and console, a Medos Hilite 2400 LT hollow fiber membrane oxygenator (MEDOS Medizintechnik AG), a 14F Medtronic DLP arterial cannula (Medtronic Inc, Minnesota), and a 20F Terumo TenderFlow Pediatric venous return cannula (Terumo Corporation, Michigan). Trials were conducted at flow rates ranging from 500 mL/min to 2,000 mL/min (500 mL/min increments) and pulsatile differential speed values ranging from 500 rpm to 2,500 rpm (500 rpm increments) using human blood (hematocrit 35%). The postcannula pressure was maintained constantly at 60 mm Hg. Real-time pressure and flow data were recorded using a custom-made data acquisition system and Labview software.

Results:

Under all experimental conditions, pulsatile flow (P) generated significantly greater energy equivalent pressure (EEP), surplus hemodynamic energy (SHE), and total hemodynamic energy (THE) than those of nonpulsatile flow (NP). Under NP, SHE was zero. Higher differential speed values generated greater EEP, SHE, and THE values. There was little variation in the oxygenator pressure drop and the cannula pressure drop in P, compared to NP.

Conclusions:

The novel Medos Deltastream DP3 diagonal pump is able to generate physiological quality of P, without backflow. With increased differential rpm, the pump generated greater EEP, SHE, and THE. Physiological quality of pulsatility may be associated with better microcirculation because of greater EEP, SHE, and THE.

Follow-up of the patients after stem cell transplantation for pediatric dilated cardiomyopathy

Dilated cardiomyopathy is a serious problem in pediatric cardiology. Despite the relatively low incidence, the mortality is high. The conservative therapy does not improve the prognosis, and possibilities of heart transplantation are limited. There are multiple trials of use of stem cells for ischemic heart disease in the adult population. This allows us to believe that the method has perspectives in pediatric cardiology. We performed the cell therapy for seven patients, six of them had complete one yr follow-up after procedure. Five to 30 milliliters of bone marrow was aspirated from the iliac crest and 17 to 122 million BMCs were isolated. The average basal EF was 33.5%. We observed increasing of EF up to 54% (=9.54, p=0.00154) in a 6-month period and up to 54.5% (=10.82, p= 0.00315) after one yr. The changes of LVEDV also were observed. The LVEDV decreased in average per 13.05%. There were no observed side effects or heart rhythm disorders. Intramyocardial administration of bone marrow-derived progenitor cells proved to be a technically feasible and safe method. Up until now, the results obtained have been promising and we suppose that bone marrow-derived progenitor cell intramyocardial transplantation can be used.

Mechanical circulatory support for end-stage heart failure in repaired and palliated congenital heart disease

Approximately one in one hundred children is born with congenital heart disease. Most can be managed with corrective or palliative surgery but a small group will develop severe heart failure, leaving cardiac transplantation as the ultimate treatment option. Unfortunately, due to the inadequate number of available donor organs, only a small number of patients can benefit from this therapy, and mortality remains high for pediatric patients awaiting heart transplantation, especially compared to adults. The purpose of this review is to describe the potential role of mechanical circulatory support in this context and to review current experience. For patients with congenital heart disease, ventricular assist devices are most commonly used as a bridge to cardiac transplantation, an application which has been shown to have several important advantages over medical therapy alone or support with extracorporeal membrane oxygenation, including improved survival to transplant, less exposure to blood products with less immune sensitization, and improved organ function. While these devices may improve wait list mortality, the chronic shortage of donor organs for children is likely to remain a problem into the foreseeable future. Therefore, there is great interest in the development of mechanical ventricular assist devices as potential destination therapy for congenital heart disease patients with end-stage heart failure. This review first discusses the experience with the currently available ventricular assist devices in children with congenital heart disease, and then follows to discuss what devices are under development and may reach the bedside soon.

The use of computational fluid dynamics in the development of ventricular assist devices

Progress in the field of prosthetic cardiovascular devices has significantly contributed to the rapid advancements in cardiac therapy during the last four decades. The concept of mechanical circulatory assistance was established with the first successful clinical use of heart-lung machines for cardiopulmonary bypass. Since then a variety of devices have been developed to replace or assist diseased components of the cardiovascular system. Ventricular assist devices (VADs) are basically mechanical pumps designed to augment or replace the function of one or more chambers of the failing heart. Computational Fluid Dynamics (CFD) is an attractive tool in the development process of VADs, allowing numerous different designs to be characterized for their functional performance virtually, for a wide range of operating conditions, without the physical device being fabricated. However, VADs operate in a flow regime which is traditionally difficult to simulate; the transitional region at the boundary of laminar and turbulent flow. Hence different methods have been used and the best approach is debatable. In addition to these fundamental fluid dynamic issues, blood consists of biological cells. Device-induced biological complications are a serious consequence of VAD use. The complications include blood damage (haemolysis, blood cell activation), thrombosis and emboli. Patients are required to take anticoagulation medication constantly which may cause bleeding. Despite many efforts blood damage models have still not been implemented satisfactorily into numerical analysis of VADs, which severely undermines the full potential of CFD. This paper reviews the current state of the art CFD for analysis of blood pumps, including a practical critical review of the studies to date, which should help device designers choose the most appropriate methods; a summary of blood damage models and the difficulties in implementing them into CFD; and current gaps in knowledge and areas for future work.

Current management of pediatric dilated cardiomyopathy

PURPOSE OF REVIEW

American and European guidelines for treatment of adult heart failure have been recently revised. This review will reconcile those guidelines to recent studies and experience in the treatment of pediatric dilated cardiomyopathy.

RECENT FINDINGS

Therapy for pediatric dilated cardiomyopathy includes establishing a diagnosis for diagnostic-specific therapies as well as preventive strategies for anthracycline toxicity and muscular dystrophy. Pediatric studies demonstrate safety and efficacy for use of angiotensin-converting enzyme inhibition and beta-blockers in dilated cardiomyopathy. Cardiac resynchronization and mitral annuloplasty represent potential nonpharmacologic therapies. Implantable defibrillator therapy may be of less import in children as compared with adults. Ventricular assist devices (VADs) are now available for all ages, which can improve survival and potentially can lead to recovery.

SUMMARY

The robust development of new therapies for adult heart failure has been successfully applied to children with dilated cardiomyopathy. Therapies for severe, intractable heart failure have been more widely utilized than therapies for mild-to-moderate heart failure.