Berlin Heart EXCOR #5: Transition from CPB to LVAD

Transitioning from cardiopulmonary bypass (CPB) to Berlin Heart EXCOR LVAD support is a controlled physiologic handoff, not simply “coming off bypass.” The circulation changes from a fully supported, non-physiologic circuit to a state in which LVAD flow is preload-limited and becomes contingent on the RV–lungs–LA inflow pipeline. Standard CPB separation principles still apply (rhythm, temperature, afterload/vasoplegia, volume status, and myocardial function), but they must be integrated with LVAD-specific preload dependence and suction risk [1].

A useful mental model

• CPB era: systemic perfusion can be maintained despite impaired RV–lung–LA transit.
• LVAD era: RV → lungs → LA becomes the mandatory inflow pathway that determines LV filling and thus LVAD output.

A frequent failure mode is not inadequate pump power, but inadequate LV preload—often driven by RV dysfunction and/or elevated PVR—resulting in low LVAD flows, suction events, and systemic hypoperfusion [4,12].

1) Core objective before leaving CPB

A transition is successful when all three conditions are met:

1. RV can deliver adequate flow through the pulmonary circuit
• Acceptable PVR and sufficient RV contractile reserve.
2. LA/LV can accept and transmit that flow to the LVAD inflow
• Adequate preload, no mechanical inflow limitation (position, obstruction, compression).
3. Total systemic cardiac output is adequate
• Total CO = native CO + LVAD flow, sufficient for end-organ perfusion.

This framework is clinically relevant because RV dysfunction is common and consequential in pediatric LVAD populations. Large multicenter outcomes series and systematic reviews highlight substantial morbidity during support [2,3], while dedicated RV-function studies demonstrate that RV failure can occur early and can evolve over time despite LV unloading [4,5].

2) Evidence-informed context (what the literature supports—and what it does not)

Current published evidence provides strong data on outcomes and RV behavior after implantation, but comparatively limited granular data on CPB-to-LVAD separation protocols (e.g., specific ramping schedules, target RAP/LAP/PCWP thresholds, or standardized TEE-based “go/no-go” criteria). This gap is important: it means the intraoperative strategy must be physiology-driven and consistent with what is known about:

• RV vulnerability during LVAD support [4,5]
• high event rates and risk factors in EXCOR cohorts [2,3]
• device support in complex physiologies (e.g., single ventricle) where pulmonary blood flow strategy and RV performance are critical determinants of stability [6].

3) Stepwise transition algorithm (“textbook workflow”)

Step 1 — Optimize RV function and reduce PVR (make the inflow pipeline work)

Goal: maximize RV output and minimize RV afterload to ensure robust LA filling.

Operational levers

• Inotropy / RV support: epinephrine (or equivalent institutional strategy), calcium optimization, correct acidosis and electrolyte derangements [1].
• Pulmonary vasodilation: inhaled nitric oxide or inhaled epoprostenol as appropriate; contemporary adult cardiac-surgery data suggest similar clinical effectiveness between iEPO and iNO for postoperative RV failure prevention/management, supporting pragmatic selection based on availability and response [9].
• Ventilation: avoid atelectasis and hypercarbia (raise PVR); avoid excessive mean airway pressure that impairs venous return and RV output.

Physiology checkpoint

• Improved RV output → ↓ RAP, ↑ LAP → improved LV filling → improved LVAD flows.

Step 2 — Establish left-heart inflow (protect LVAD preload)

Goal: confirm that LA→LV filling is adequate and that the LVAD inflow will remain stable as support increases.

TEE-based confirmation (minimum set)

• LV cavity size: avoid an “empty LV” configuration
• Inflow cannula orientation and clearance (no near-wall contact)
• Septal position and LV geometry (avoid excessive leftward shift)
• Exclude mechanical contributors (tamponade, inflow obstruction, severe TR/MR dynamics affecting filling)

TEE is the fastest discriminator between true RV/PVR limitation and mechanical inflow problems and should be treated as a core monitoring tool during implantation and separation [10–12].

Step 3 — Ramp LVAD flow gradually (avoid a “snap transition”)

Goal: transfer systemic output from CPB to LVAD in controlled increments while observing preload adequacy.

• Start LVAD at low support, then increase stepwise.
• Keep CPB as a safety net while confirming:
• stable LV size (not collapsing),
• stable venous return and pulmonary transit,
• absence of suction behavior on echo/hemodynamics.

Step 4 — Use RAP vs LAP as a rapid decision rule (high-yield screen)

This rule operationalizes whether the RV–lung–LA pipeline is supplying adequate LVAD preload.

✅ Pattern A: RAP < LAP

• Interpretation: pulmonary transit is functioning; LV filling is adequate
• Action: proceed with further CPB wean and LVAD up-titration

⚠️ Pattern B: RAP > LAP

• Interpretation: LV is underfilled relative to right-sided pressures
• Likely mechanisms
• elevated PVR (pulmonary “gate” partially closed)
• RV dysfunction (insufficient forward flow)
• excessive drainage / imbalance between LVAD + venous return during the handoff
• Action: step back
• reduce LVAD demand temporarily and rebalance drainage
• treat RV/PVR (inotropy, pulmonary vasodilator, ventilation/recruitment)
• reassess with TEE and pressures

This pattern is consistent with pediatric observational data showing RV dysfunction and progressive RV remodeling can persist or evolve during LVAD support, reinforcing the need to treat the upstream circuit when LVAD filling is inadequate [4,5].

Step 5 — Wean CPB gradually (handoff of CPB’s two functions)

CPB is simultaneously providing:

1. Volume drainage (venous return management)
2. Systemic perfusion (arterial flow)

Technique

• Reduce CPB flow stepwise while LVAD flow increases, monitoring:
• MAP and pulse pressure
• lactate/acid–base and perfusion surrogates
• LV size and septal position on TEE
• suction indicators (echo + hemodynamic instability)

Step 6 — Final check: define and confirm “total output”

Total systemic flow = native CO + LVAD flow.

Before committing to full separation:

• confirm end-organ perfusion surrogates (MAP, NIRS if used, acid–base)
• confirm stable LV geometry and no suction pattern

Suction is a recognized hazard when LVAD unloading exceeds preload (underfilled LV) or when inflow geometry predisposes to wall contact; echocardiography is central to diagnosis and iterative correction (reduce LVAD demand, restore preload, correct upstream limitations) [12].

4) Common failure modes and targeted fixes

A) Low LVAD flow + rising RAP + low/flat LAP

Mechanism: RV–PVR limitation → inadequate LV preload

Fix: treat upstream

• pulmonary vasodilator (iNO/iEPO) and ventilation optimization [9]
• RV inotropy/lusitropy strategy; correct acidosis/hypocalcemia [1]
• avoid excessive airway pressures

B) “Empty LV” / suction tendency despite acceptable systemic pressure

Mechanism: over-unloading relative to filling (or inflow proximity to wall)

Fix: temporarily reduce LVAD demand, restore preload, reassess inflow position/geometry by TEE [12]

C) Adequate LV filling but persistent hypotension

Mechanism: vasoplegia, bleeding, inadequate SVR, residual structural issue

Fix: vasopressors + volume/blood product strategy; ensure hemostasis and exclude mechanical/outflow limitations [1]

5) How outcomes data should shape intraoperative judgment

Large EXCOR cohorts and systematic reviews demonstrate that pediatric VAD support is effective but complication-prone, and that patient factors (including small size and complex physiology) influence risk [2,3]. Single-ventricle experience highlights that pulmonary blood flow configuration and right-sided performance can be decisive; caution is warranted when pulmonary blood flow is shunt-dependent [6]. Finally, recovery/weaning from EXCOR is possible in selected patients, but remains uncommon; systematic data suggest a small proportion can be successfully explanted, underscoring the importance of meticulous peri-implant and on-support management to create a stable platform for recovery when it occurs [7,8].

References

[1] Licker M, Diaper J, Cartier V, Ellenberger C, Cikirikcioglu M, Kalangos A, Cassina T, Bendjelid K. Weaning from cardiopulmonary bypass after cardiac surgery. Ann Card Anaesth. 2012;15(3):206-223.

[2] 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, 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.

[3] Rohde S, Antonides C, Dalinghaus M, Muslem R, Bogers A. Clinical outcomes of paediatric patients supported by the Berlin Heart EXCOR: a systematic review. Eur J Cardiothorac Surg. 2019;56(5):830-839.

[4] Iacobelli R, Di Molfetta A, Brancaccio G, Filippelli S, Morelli S, Natali B, Toscano A, Drago F, Amodeo A. Acute and Long-Term Effects of LVAD Support on Right Ventricular Function in Children with Pediatric Pulsatile Ventricular Assist Devices. ASAIO J. 2018;64(3):e42-e48.

[5] Di Molfetta A, Iacobelli R, Filippelli S, Grutter G, Perri G, Iodice F, Pasquini L, Guccione P, Amodeo A. Evolution of Biventricular Loading Condition in Pediatric LVAD Patient: A Prospective and Observational Study. Artif Organs. 2018;42(4):386-393.

[6] Weinstein S, Bello R, Pizarro C, Fynn-Thompson F, Kirklin J, Guleserian K, Woods R, Tjossem C, Kroslowitz R, Friedmann P, Jaquiss R. The use of the Berlin Heart EXCOR in patients with functional single ventricle. J Thorac Cardiovasc Surg. 2014;147(2):697-705.

[7] Mikulski MF, Iyer S, Well A, Mery CM, Owens WR, Glass L, Castleberry C, Fraser CD. Successful explantation of children from the Berlin Heart EXCOR ventricular assist device: A systematic review. Artif Organs. 2024;48(4):e1-e12.

[8] Rohde S, de By TDD, Bogers A, Schweiger M. Myocardial recovery in children supported with a durable ventricular assist device—a systematic review. Eur J Cardiothorac Surg. 2023;64(2):ezad263.

[9] Ghadimi K, MacLaren G, Fashandi AZ, et al. Inhaled Epoprostenol Compared With Nitric Oxide for Right Ventricular Failure After Major Cardiac Surgery. Circulation. 2023;148(5):405-418.

[10] Reeves ST, Finley AC, Skubas NJ, et al. Basic perioperative transesophageal echocardiography examination: a consensus statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr. 2013;26(5):443-456.

[11] Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr. 2013;26(9):921-964.

[12] Stainback RF, Estep JD, Agler DA, et al. Echocardiography in the management of patients with left ventricular assist devices: recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2015;28(8):853-909.