Berlin Heart EXCOR #1: Paracorporeal, Pulsatile Pediatric VAD

Paracorporeal, pneumatically driven pulsatile VAD for pediatric mechanical circulatory support

Berlin Heart EXCOR is a paracorporeal (outside-the-body), pneumatically driven, pulsatile ventricular assist device (VAD) engineered for infants through adolescents with refractory heart failure, most commonly to provide durable bridge-to-transplant (BTT) support when medical therapy and/or short-term mechanical support are insufficient [1,2]. Its clinical niche is defined by pediatric sizing, configuration flexibility (LVAD/RVAD/BVAD), and feasibility in small body weight patients, where many adult-derived continuous-flow systems remain anatomically or technically constrained [1–3].

1) Clinical intent and where EXCOR fits in the MCS pathway

1. Dominant indication: Bridge-to-transplant (BTT)
• Maintain end-organ perfusion, reverse shock physiology, and stabilize nutrition/rehabilitation until donor availability [1–3].
2. Less common indications
• Bridge-to-recovery (selected myocarditis or post-cardiotomy dysfunction with myocardial recovery potential) [1,3].
• Bridge-to-decision (time to clarify transplant candidacy, neurologic trajectory, or long-term strategy) [1].

Evidence-based performance anchor: In a large multicenter US cohort (n=204), 12-month survival was ~75%, with ~64% reaching transplant and smaller fractions recovering or remaining on support; importantly, outcomes were strongly modulated by weight, organ dysfunction, and BiVAD requirement [1].

2) System anatomy and blood flow (how it works)

2.1 Core components

• Paracorporeal blood pump(s) with pulsatile stroke volume; transparent housing facilitates bedside inspection for filling and clot burden (practical advantage in daily management) [2,7].
• Cannulae
• Inflow: most commonly LV apex (systemic ventricle); atrial inflow can be used in select anatomy/strategies [1–3].
• Outflow: typically to ascending aorta for LVAD configuration; RVAD outflow is generally to the pulmonary artery (center/anatomy dependent) [1–3].
• External pneumatic driver controlling systolic/diastolic phases (rate, systolic fraction) that determine effective minute flow [2,7].

2.2 LVAD flow path (conceptual)

Pulmonary venous return → LA/LV → LV apex inflow cannula → EXCOR pump → ascending aorta outflow cannula → restored systemic cardiac output with ventricular unloading [1–3].

3) Configurations and the “systemic ventricle” framing

1. LVAD
• Best suited for isolated/dominant LV failure (cardiomyopathy, myocarditis, post-op LV dysfunction) [1–3].
2. RVAD
• Considered when RV failure is primary or when LVAD alone is predicted to unmask or worsen RV inadequacy (CHD/post-op scenarios) [1–3].
3. BVAD
• Applied for true biventricular failure or when isolated LVAD is unlikely to achieve stable perfusion [1–3].
• BVAD is consistently associated with higher mortality risk in multicenter experience, reflecting both disease severity and the complexity of physiology/management [1,2].

Congenital heart disease lens: Rather than “LV vs RV,” strategy should be anchored to which chamber is the systemic ventricle (e.g., systemic RV physiology) and whether durable unloading can be achieved without creating inflow/outflow limitation or prohibitive suction risk [1–3].

4) Outcomes: what the multicenter literature shows

4.1 Survival to transplant/recovery (range and why it varies)

Across cohorts, EXCOR support achieves meaningful BTT success, often reported in the ~64–86% range depending on age/weight, diagnosis mix, and configuration [1–6,9]. Variation is not noise—it is largely explained by:

• Body size (lower weight) and
• need for BVAD, and
• end-organ dysfunction at implantation (notably hepatic/renal markers) [1,4].

4.2 Key multicenter risk signals (patient selection)

• In the US cohort (n=204), lower weight, BiVAD support, and elevated bilirubin predicted early mortality; renal/hepatic dysfunction tracked late risk. Neurologic dysfunction was common and a leading cause of death [1].
• In children <10 kg, outcomes were inferior to larger children; mortality risk increased with congenital heart disease and elevated bilirubin (a pragmatic marker of systemic illness/venous congestion/hepatic injury) [4].
• Large early North American experience similarly showed higher mortality with younger age and BiVAD, and documented frequent use as a bridge from ECMO in selected patients [2].

4.3 Post-transplant outcomes (critical reassurance)

Early post-transplant survival for EXCOR-bridged children is comparable to status-matched non-VAD transplant recipients in multicenter analyses, supporting EXCOR as a legitimate bridge strategy rather than a “high-risk pre-transplant penalty” by default [5]. This shifts the decision emphasis toward:

• timing of implantation (before irreversible injury), and
• complication prevention (especially neurologic/hemocompatibility events) during support [1,5].

5) Pump size selection and “flow logic” (why sizing is more than weight)

Pump stroke volumes commonly used include 10, 15, 25, 30, 50, and 60 mL (program- and region-dependent listings), selected to meet target systemic flow while preserving safe filling and minimizing suction events [1–4,7].

A functional sizing model (three-variable fit):

1. Target output (perfusion goals: lactate clearance, end-organ recovery, growth/rehab trajectory) [1,2].
2. Cannula resistance and geometry (diameter/length/position; suction vulnerability at inflow) [1,2,7].
3. Driver settings (rate and systolic fraction determine effective minute volume; mismatched settings can “over-pump” a preload-limited ventricle and precipitate suction/arrhythmia/hemolysis) [2,7].

Practical implication: EXCOR provides stroke-volume scalability, but stable support requires disciplined control of preload, afterload, and ventricular decompression, typically guided by serial echocardiography and end-organ markers [1,2,7].

6) Complications: predictable domains that define daily management

Even in experienced centers, morbidity concentrates in a limited set of domains:

1. Neurologic events (stroke/neurologic dysfunction)
• Neurologic dysfunction is consistently prominent in registry-era experience and is a major determinant of both survival and quality of recovery [1].
• In infant-focused series, stroke rates may be lower than early multicenter signals, but remain clinically meaningful [6].
2. Pump thrombosis and need for pump exchange
• Thrombus formation with pump exchange is a recurring reality in long-term runs and demands standardized surveillance and exchange workflows [7,8].
• Institutional experience highlights that pump exchange can be performed safely when protocols are mature, but it remains a marker of hemocompatibility stress and systemic risk [7,8].
3. Bleeding / anticoagulation narrow therapeutic window
• Anticoagulation is obligatory; the bleeding–thrombosis balance is especially fragile in infants and complex CHD physiology, amplifying the need for protocolized management [1,4,7].
4. Infection (cannulation sites / external hardware)
• Paracorporeal architecture increases exposure risk; infection prevention and early treatment are foundational to program success [6–8].

Program-level theme: Outcomes improve when implantation occurs before irreversible end-organ injury and when teams execute protocolized anticoagulation, circuit surveillance, and rapid response pathways to neurologic or pump-related events [1,2,4,7,8].

7) Comparative positioning: EXCOR vs VA-ECMO as bridge strategies

For children requiring BTT, observational comparisons have shown better survival to transplant/recovery with EXCOR than ECMO in appropriately selected patients, while ECMO remains indispensable for immediate rescue in profound shock or severe respiratory failure [3]. Conceptually:

• ECMO = rapid stabilization / short runway
• EXCOR = durable support enabling rehabilitation, growth, and end-organ recovery while waiting for transplant [1–3].

8) Special populations (where risk–benefit shifts)

1. Infants / first year of life
• EXCOR can provide durable support with high bridge success in selected infant cohorts, but neonates with severe illness phenotypes (e.g., myocarditis with re-intervention needs) may carry higher risk [6].
2. Congenital heart disease and small size
• CHD and <10 kg status magnify risk and demand careful cannulation strategy, inflow geometry planning, and early organ protection; bilirubin elevation is a consistent warning signal [4].
3. Restrictive / hypertrophic cardiomyopathy (diastolic failure physiology)
• Diastolic pathophysiology is high-risk for mechanical support, with lower bridge success and higher complication vulnerability compared with dilated phenotypes; configuration choice (LVAD vs BiVAD) and patient age remain influential [9].

9) High-yield summary (textbook takeaways)

• Berlin Heart EXCOR Pediatric is a paracorporeal, pneumatically driven pulsatile VAD primarily used as bridge-to-transplant in children with severe LV, BiV, or systemic ventricular failure refractory to medical therapy [1,2].
• Typical LVAD cannulation is LV apex inflow → ascending aorta outflow, with RVAD/BVAD options when physiology requires [1–3].
• Multicenter data show clinically meaningful BTT success; lower weight, BiVAD support, and hepatic/renal dysfunction are consistent risk factors, and neurologic events remain a defining complication domain [1,4,5].
• Post-transplant survival for EXCOR-bridged children is generally comparable to status-matched non-VAD recipients, shifting attention to optimal timing, protocolized anticoagulation, and complication prevention during support [5].

References

[1] Almond CS, Morales DL, Blackstone EH, Turrentine MW, Imamura M, Massicotte MP, Jordan LC, Devaney EJ, Ravishankar C, Kanter KR, Holman W, Kroslowitz R, Tjossem C, Thuita L, Cohen GA, Buchholz H, St Louis JD, Nguyen K, Niebler RA, Walters HL 3rd, Reemtsen B, Wearden PD, Reinhartz O, Guleserian KJ, Mitchell MB, Bleiweis MS, Canter CE, Humpl T. Berlin Heart EXCOR pediatric ventricular assist device for bridge to heart transplantation in US children. Circulation. 2013;127(16):1702-1711.

[2] Morales DLS, Almond CSD, Jaquiss RDB, Rosenthal DN, Naftel DC, Massicotte MP, Humpl T, Turrentine MW, Tweddell JS, Cohen GA, Kroslowitz R, Devaney EJ, Canter CE, Fynn-Thompson F, Reinhartz O, Imamura M, Ghanayem N, Buchholz H, Furness S, Mazor R, Gandhi S, Fraser CD. Bridging children of all sizes to cardiac transplantation: the initial multicenter North American experience with the Berlin Heart EXCOR ventricular assist device. J Heart Lung Transplant. 2011;30(1):1-8.

[3] Imamura M, Dossey AM, Prodhan P, Schmitz M, Frazier E, Dyamenahalli U, Bhutta A, Morrow WR, Jaquiss RDB. Bridge to cardiac transplant in children: Berlin Heart versus extracorporeal membrane oxygenation. Ann Thorac Surg. 2009;87(6):1894-1901.

[4] Conway J, St Louis J, Morales DLS, Law S, Tjossem C, Humpl T. Delineating survival outcomes in children <10 kg bridged to transplant or recovery with the Berlin Heart EXCOR Ventricular Assist Device. JACC Heart Fail. 2015;3(1):70-77.

[5] Eghtesady P, Almond CSD, Tjossem C, Epstein D, Imamura M, Turrentine M, Tweddell J, Jaquiss RDB, Canter C. Post-transplant outcomes of children bridged to transplant with the Berlin Heart EXCOR Pediatric ventricular assist device. Circulation. 2013;128(11 Suppl 1):S24-S31.

[6] Davis LM, Lee MGY, Sheridan BJ, d'Udekem Y, Brizard CP, Konstantinov IE, Mathew J, Brink J. Berlin Heart EXCOR Support in the First Year of Life: A Single Centre Experience. Heart Lung Circ. 2021;30(3):446-453.

[7] Humpl T, Furness S, Gruenwald C, Hyslop C, Van Arsdell G. The Berlin Heart EXCOR Pediatrics-The SickKids Experience 2004-2008. Artif Organs. 2010;34(12):1082-1086.

[8] Sandica E, Zu Knyphausen E, Blanz U, Röfe D, Morshuis M. Safety of Long-Term Mechanical Support With Berlin Heart EXCOR in Pediatric Patients. World J Pediatr Congenit Heart Surg. 2012;3(1):72-76.

[9] Su JA, Menteer J. Outcomes of Berlin Heart EXCOR® pediatric ventricular assist device support in patients with restrictive and hypertrophic cardiomyopathy. Pediatr Transplant. 2017;21(8):e13048.

[10] Cassidy J, Dominguez T, Haynes S, Burch M, Kirk R, Hoskote A, Smith JH, Fenton M, Griselli M, Hsia TY, Ferguson L, van Doorn C, Hasan A, Karimova A. A longer waiting game: bridging children to heart transplant with the Berlin Heart EXCOR device--the United Kingdom experience. J Heart Lung Transplant. 2013;32(12):1101-1106.