Treatment of Heart Failure: Mechanical Support

Iki Adachi

Lara Shekerdemian

Paul A. Checchia

Charles D. Fraser Jr.

KEY POINTS

The number of children with heart failure has been increasing, resulting in growing demand for mechanical circulatory support (MCS) in the pediatric population.

Because of an oxygenator, extracorporeal membrane oxygenation (ECMO) should be considered a device for “cardiac and pulmonary” support.

Short-term ventricular assist devices (VADs) provide better decompression of a failing ventricle than do ECMO, and hence is the device of choice when the etiology of heart failure is deemed acute process.

Long-term VADs offer the opportunity to rehabilitate the patients while waiting for heart transplantation, making them better surgical candidates.

There are certain situations, such as posttransplant chronic graft failure, where VAD support is not an ideal solution. Total artificial heart can be a superior option in such settings although currently total artificial heart is a realistic option only for older adolescents due to device size.

The history of mechanical circulatory support (MCS) development spans more than 50 years. The first clinical ventricular assist device (VAD) implantation was performed by DeBakey in 1963 (1), which was 4 years earlier than the first orthotopic heart transplantation by Barnard in South Africa (2). In 1969, a total artificial heart was used in human for the first time by Cooley (3). Interestingly, both of these “firsts” in MCS occurred even before the first clinical use of extracorporeal membrane oxygenation (ECMO) in 1971 by Hill (4). Thanks to continuing improvements in device technology and a growing spectrum of MCS devices available, adults with end-stage heart failure are now treated with devices that can be tailored to their individual needs. In contrast, MCS for children has significantly lagged behind their adult counterpart (5). Indeed, ECMO has long been the mainstay or even the only modality for MCS in children. This frustrating situation has, however, started to change. Following the Berlin Heart Investigational Device Exemption trial (6), the U.S. Food and Drug Administration (FDA) granted Humanitarian Device Exemption approval of the Berlin Heart EXCOR in late 2011. The EXCOR has become the first pediatric-specific VAD that has gained widespread acceptance worldwide, with the potential to transform the outlook for children with end-stage heart failure who are awaiting transplantation. As pediatric patients are so divergent in terms of size and cardiac physiology, appropriate device selection and good understanding of each device are keys to success. In this chapter, we will discuss several types of MCS devices available for children, particularly focusing on VADs.

HEART FAILURE IN CHILDREN

The number of children with heart failure has been increasing, resulting in growing demand for MCS in the pediatric population. A recent analysis (2009) of 15 million pediatric hospitalizations using the Healthcare Cost and Utilization Project Kids Inpatient Database revealed an increasing number of pediatric hospital admissions for heart failure (a 30% increase over 3 years) (7). Possible explanations include better recognition of pediatric cardiomyopathy with earlier intervention with medical therapy and advancements in surgery and perioperative care for children with congenital heart disease (CHD), leading to increased long-term survival of this patient population. One of the inevitable consequences of improved survival of these patient groups will be an increased incidence of end-stage heart failure in children, adolescents, and young adults. Typical examples of end-stage heart failure in the setting of operated CHD involve children whose morphological right ventricle is sustaining the systemic circulation and who progress to failure of that systemic ventricle. While cardiac transplantation remains the treatment of choice for end-stage heart failure, it is unlikely that this growing need can be addressed by transplantation only due to the static number of donor organs available. Indeed, numbers of heart transplantation procedures worldwide has been stagnant for over a decade (8).

While pediatric MCS is in rapid evolution, there has been significant refinement of MCS therapy in adults over the last decade. The most significant change to have an impact on patient management strategy was the emergence of durable intracorporeal (implantable) devices such as the HeartMate II (Thoratec, Corp., Pleasanton, CA). Owing to the impressive efficiency of these devices with relatively low morbidity profiles, the indications for device placement have changed, making the early institution of the device a reasonable option in preference to escalating medical management and to improve outcome (9). In adults, VADs are used as a bridge to transplant, as a bridge to recovery (10), or as destination therapy (for patients who opt against transplantation or for whom transplantation is not an option) (11).

The scope of the use of the HeartMate II and other intracorporeal devices in the pediatric population is limited by body size, and they can therefore only be used to provide MCS in larger children and adolescents. Although miniaturized
intracorporeal devices for smaller children are on the horizon, the Berlin EXCOR, a paracorporeal pulsatile device, is the only currently available option for this group of patients. When comparing the data of the Berlin Heart Investigational Device Exemption (IDE) trial (6) to that of initial European experience (12), it is likely that higher success rates (˜90% in IDE trial vs. 70% in Europe) can be achieved with very careful patient selection and management at higher volume centers (5). However, the Berlin Heart EXCOR is associated with significant morbidity profiles (stroke in ˜30%, bleeding in 40%-50%, and infection in 50%-60%). The incidence of complications in children with pulsatile VADs is greater than in adults with intracorporeal devices. This significant complication rate in children suggests the need for careful assessments of the risks and benefits when considering device placement.

PATIENT SELECTION

MCS for any patient is indicated when the benefits of MCS are deemed to outweigh the risks. Since each patient and each device has unique risk profiles, the appropriateness of MCS and the timing of this need to be determined on a case-by-case basis, by the multidisciplinary team, the family, and where appropriate the patient. Special consideration should be given to not only medical, but also social aspects (i.e., family situation and support, prior compliance with medication, etc.). MCS selection should also be influenced by the institutional experience. As with all interventions, one’s threshold to provide a therapy changes as the confidence in that therapy to produce beneficial and consistent outcomes for patients increases.

There are other confounding issues that must be considered in providing MCS in children and when choosing the most appropriate device for a given child. Children with CHD may have anatomic variations that pose significant difficulty in cannulation for MCS (e.g., abnormal size and location of the aorta, unusual location or shape of the ventricle). Previous surgical procedures may jeopardize the application of MCS with derangement of anatomy and of circulatory physiology. These include systemic-pulmonary artery shunts or disconnected caval veins or pulmonary artery after Glenn or Fontan operations. In addition to careful attention to the anatomy and circulatory physiology, a thorough understanding of the unique pathophysiological features of pediatric heart failure is an absolute prerequisite to a successful outcome with MCS.

At present, long-term VAD support in children requires candidacy for heart transplantation. When considering contraindications to MCS in children, extreme prematurity, very low body weight (<2.0 kg), significant preexisting neurologic injury, a constellation of congenital anomalies with poor prognosis (unlikely survival beyond childhood), and major chromosomal aberrations are generally accepted contraindications for MCS. Multisystem organ failure may be a relative contraindication, but does not necessarily exclude patients from MCS if reversal of organ function is predicted once hemodynamic improvement is achieved. Indeed, it has been well documented that liver and renal dysfunction improve after restoration of hemodynamic stability with MCS (13,14).

DEVICE SELECTION

Device selection for initial MCS in children with heart failure is ideally limited to cardiac support with VADs, which support the left ventricle (LVAD), right ventricle (RVAD), or both (BiVAD). However, some children with acute decompensated heart failure also have significant pulmonary dysfunction, which is most often reversible and may require cardiopulmonary support; in such case temporary support with ECMO may be indicated. Moreover, if the patient is in cardiopulmonary arrest with ongoing cardiopulmonary resuscitation, then ECMO is the initial support of choice as this can be rapidly initiated (peripherally) and will provide support to both right and left heart as well as the lungs. Our own institutional Pediatric MCS guideline is depicted in Figure 75.1.

EXTRACORPOREAL MEMBRANE OXYGENATION

We will not discuss ECMO in detail since ECMO

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