Selection and Management of Pediatric and Congenital Heart Disease Patients on Ventricular Assist Devices

Stats:

• More than 1/3 patients receiving heart transplants had a ventricular assist device (VAD).
• Less than 10 VADs are implanted per year on average at most hospitals.

Statement Background: VADs and pediatric heart failure

The International Society for Heart and Lung Transplantation (ISHLT) released a consensus statement from top experts in the field regarding the management of pediatric and congenital heart disease (CHD) patients who are on VADs.

The use of VADs is becoming a more prevalent treatment for pediatric heart failure. The 2019 ISHLT registry found more than one-third of patients being transplanted were bridged to transplant with a VAD. While use of VADs increased in the last decade, most hospitals reported implanting less than 10 VADs each year.

The consensus statement was guided by evidence when available, as well as expert opinion due to lack of pediatric-focused literature and research. Scott Auerbach, MD, medical director of the Ventricular Assist Device Program at Children's Hospital Colorado and Kathleen Simpson, MD, heart failure and transplant cardiologist specializing in heart failure in congenital heart disease, participated in the development of the consensus document. The guideline aims to improve outcomes in children with end-stage heart failure and was endorsed by the American Heart Association. Learn more about Children's Colorado's pediatric cardiac surgery outcomes.

Patient selection: timing of VAD

Decision-making for optimal timing of VAD implantation in pediatric patients is a complex choreography of assessing risks and benefits.

• VAD implementation should be considered before significant end-organ dysfunction or clinical deterioration.
• Patients in cardiogenic shock, or INTERMACS Profile 1, have increased mortality rates post VAD. Consider stabilization prior to durable support, such as attempts to reverse shock or using temporary mechanical circulatory support like extracorporeal membrane oxygenation (ECMO) or a paracorporeal continuous-flow device for children with end-organ dysfunction.

Indications for VAD

Failure of medical management

Despite medical management, commonly reported measures of congestion and/or inadequate cardiac output include:

• Progressive respiratory decompensation
• Liver dysfunction
• Kidney injury
• Feeding intolerance
• Elevated pulmonary vascular resistance
• End-organ dysfunction

Post-cardiotomy failure to wean from cardiopulmonary bypass (CPB)

Failure to wean from CPB or decompensation during the index hospitalization after cardiac surgery is a significant risk factor for mortality among patients supported with the Berlin Heart EXCOR.

Intent: VAD strategies

Bridge to transplant

• Primary indication for pediatric VAD in North America
• 55% listed at the time of implantation

Bridge to candidacy or decision

• 34% accessed for candidacy

Destination therapy

• Becoming more common in certain patients with:
• Muscular dystrophy (MD)
• CHD

Pre-implant planning

End-organ assessment

Preoperative renal, hepatic, respiratory and nutritional failure are associated with worse post-VAD outcomes. But preoperative end-organ dysfunction occurs in many patients, likely due to late presentation, late diagnosis or delayed timing for implantation.

• Congestive hepatopathy from heart failure has been associated with post-VAD morbidity and mortality.
• Mortality is higher in patients with high bilirubin levels, especially those weighing less than 10 kg (70% mortality).
• Tube feeding, TPN or both have been reported in up to 64% of patients undergoing VAD implantation.

Right heart assessment

Up to 42% of children experience “right heart failure” after LVAD implant.

• Individual assessment parameters cannot solely predict the need for RV support.
• Clinical, imaging, and hemodynamic parameters for predicting need for pediatric BiVAD support is limited but includes preoperative ECMO and elevated blood urea nitrogen.
• If RVAD support is needed, consider temporary RV for RV recovery after CPB and decompression of the RV and improvement of fluid overload.

Single ventricle VAD

• LVAD versus BiVAD support relates only to patients with biventricular circulations.
• A systemic VAD (SVAD) in single ventricle circulation patients could result in suboptimal outcomes if the patient’s circulatory derangement perturbations are from the Fontan pathway and not ventricular dysfunction (pump failure).

Device selection

After the decision to place a VAD has been made, the next crucial step is to determine the level of support needed (LVAD vs. SVAD or BiVAD in biventricular circulation).

Key considerations:

• Patient-device size matching
• Implant configuration LVAD, SVAD or BiVAD
• Duration of support
• Support intent

There are several devices used for children with end-stage heart failure.

Devices used in children and adolescents

Broad categorizations of VADs include:

• Duration of support (temporary vs. durable)
• Design (pulsatile vs. continuous-flow)
• Site of implantation (paracorporeal, intracorporeal or intravascular)

Patient size and devices used:

• Intracorporeal CF devices are generally considered in children >15-20kg, with use increasing over the last decade.
• The Berlin EXCOR is used mostly in children <20kg.
• The paracorporeal continuous-flow devices are used in patients that may recover, those that need BiVAD support and as a BTT in some high-risk populations such as small children with CHD.
• While TAH can be used in children, its typically unique situations such as complex CHD and transplant graft failure.

Operative management

The optimal surgical technique depends on the device and the patient’s unique characteristics. In children, challenges due to anatomic and pathophysiologic variations remain.

In pediatric patients with residual shunting, shunt closure (exceptions may exist in the Fontan patients) should occur at the time of VAD implant.

Postoperative hemodynamic goals

After returning to the ICU, the primary postoperative goals include:

• Obtain sufficient systemic perfusion
• Maintain normal systemic and venous pressure
• Avoid VAD-related complications

For EXCOR, target settings to allow a full fill and ejection with each cycle. Digital image capture with slow motion can help assess membrane movement.

Individualize continuous-flow device support parameters based on physiologic support needs; optimize support through parameter changes and manipulation of afterload and preload.

Anticoagulation management

Bleeding is a significant issue after VAD implantation.

• For anticoagulation, direct thrombin inhibitors (DTI) therapy, particularly bivalirudin, is becoming more common in North America for paracorporeal VAD support in children.
• In EXCOR patients, post-VAD inflammation may increase the risk of thrombosis, bleeding and stroke.
  • Steroids have been used in small single-center cohorts to treat inflammation and decrease stroke chances.

Adverse events

Adverse events include:

• Infection (17% of all adverse events)
• Right ventricular failure (usually occurs within 2 weeks of LVAD, associated with morbidity and mortality)
• Pump thrombosis (less common, but significant)
• Neurological events and stroke (~12% of all adverse events)
• Bleeding (major complication, affects 30% of all pediatric patients)

Support strategies for unique pediatric populations

Small patients, patients with Muscular Dystrophies or chemotherapy-induced cardiomyopathies, adult congenital heart disease or single ventricle physiology require different strategies.

• Evaluate patients with Adult Congenital Heart Disease (ACHD) for mechanical circulatory support early before the progression of end-organ dysfunction.
• ACHD patients have a higher earlier mortality rate, but they have similar adverse event rates and improvement in quality of life when compared to non-ACHD patients.

Support strategies for single-ventricle patients

• Stage 1 patients with parallel circulations often need SVAD flows to achieve a higher cardiac index; balanced Qp/Qs are crucial.
• Consider converting stage 2 patients to shunted or Fontan physiology at time of SVAD implant to improve pulmonary blood flow.
• Durable VAD use to support Fontan patients with HF due to systemic ventricular dysfunction is becoming more successful.

Discharge of the pediatric patient on a VAD

Despite advancements in VAD technology for improved survival, quality of life and the potential for hospital discharge, less than 60 percent of children with intracorporeal CF devices in the US or Europe are discharged. Some medically stable patients are suitable for safe discharge.

Preparing for heart transplant and post-transplant survival

• Patients on VAD support listed for a heart transplant (HT) should receive testing for anti-HLA sensitization, even though some antibodies may only be present transiently and higher sensitization in VAD patients has not seemed to affect post-transplant outcomes.
• A prolonged time for VAD recovery and cardiac rehabilitation (CR) before listing for HT has led to improved outcomes in some studies.
• Cardiac rehabilitation should begin early post-operatively and advance to a multidisciplinary approach with the goal of whole-body rehabilitation for HT or explanation when possible.
• Nutritional status should be optimized for all patients before and after VAD implantation.

End of life care of the pediatric patient on VAD

• Many young people prefer to be involved in decision-making regarding their end of life.
• Communication with parents and patients concerning symptom management, decision-making, and advanced care planning for known potential adverse events should occur early and regularly.
• Discuss the potential need for compassionate deactivation before a VAD is implanted; it is critical to support patients, families and clinicians.