Berlin Heart EXCOR #4: Implantation—Inflow

The LV inflow is the point of entry to the EXCOR circuit and is a dominant determinant of whether support remains stable (reliable LV decompression) or is complicated by suction events, low-flow alarms, hemolysis, and thromboembolic complications. Although the published pediatric EXCOR literature is weighted toward clinical outcomes rather than step-by-step operative technique, those outcome data underscore why inflow construction must be geometrically correct, unobstructed, and durable. Stroke rates reported across pediatric cohorts range widely (≈5–47%), and pump thrombosis requiring exchange remains a recurring burden—particularly in small infants. [1, 2]

1) Core concept: “Geometry-first” inflow design

A high-performance inflow configuration achieves laminar, non-collapsing LV drainage across changing loading conditions. The practical geometric endpoints are:

• Central-cavity drainage

The cannula should draw from the largest, mid-cavity blood pool, not from a near-wall trabecular pocket.

• No interaction with subvalvular structures

Avoid contact with trabeculations, papillary muscles, and chordae to prevent intermittent obstruction and shear.

• Non–septum-facing trajectory

A septum-directed cannula is mechanically “fragile”: even minor shifts in LV volume or ventricular remodeling can precipitate repetitive suction and unstable filling.

Evidence context (why this matters): Large multicenter experience confirms that neurologic injury and device-related adverse events remain major determinants of morbidity during EXCOR support. [3] Systematic outcome synthesis similarly highlights substantial stroke variability and frequent device exchanges, reinforcing that “durable support” depends on both anticoagulation strategy and mechanically stable flow conditions. [1]

2) Pre-coring planning: choose the apex precisely

2.1 Identify coronary landmarks (mandatory)

Plan the apical entry by directly visualizing epicardial coronaries and defining a safe zone bounded by:

• LAD and diagonal branches (Dx) anteriorly/anterolaterally
• Posterior descending (PDA/PD) territory posteriorly/inferiorly

This protects against iatrogenic coronary injury and helps avoid later cannula–coronary “conflict” after tunneling and pump positioning.

2.2 Use the “muscular dimple” as a practical surface marker

The muscular dimple often corresponds to a stable apical site that supports a favorable intraventricular trajectory (toward the mid-LV cavity), particularly when the apparent apex is distorted by dilation, rotation, or prior operations.

2.3 Echocardiographic confirmation (high-yield when geometry is abnormal)

TEE or epicardial echo can confirm that the planned cannula trajectory:

• Avoids the septum
• Avoids the mitral apparatus
• Will reside in a large, central LV cavity

This is especially useful in congenital geometries, restrictive physiology, or markedly remodeled ventricles, where surface landmarks can be misleading.

3) Ventriculotomy + coring: create a clean, coaxial inflow “chamber”

After ventriculotomy and coring, treat the LV as a flow chamber that must be streamlined around the cannula mouth.

3.1 Coring objective

Create a circular apical opening that permits:

• Symmetric seating of the sewing ring/cannula
• A stable, coaxial cannula trajectory
• Hemostatic closure without tissue distortion

3.2 Resection of obstructors (debridement for flow stability)

Resect or trim structures that can intermittently occlude inflow:

• Prominent trabeculations
• Hypertrophied muscle bundles
• Tissue tags that may behave like a “flap valve” during higher pump filling

Technical endpoint: the cannula should not be forced into a trabecular pocket and should not point toward the septum.

Evidence context: In infants <10 kg, device exchange for thrombosis can be frequent (reported as high as 56 pump changes, ≈1.86 pumps per patient in a single-center series), illustrating the high consequence of any combination of thrombotic substrate + flow instability. [2]

4) Sewing ring fixation: pledget strategy and load distribution

4.1 Pledgeted, evenly spaced, full-thickness sutures

Use uniformly spaced, full-thickness, pledgeted sutures to:

• Distribute load across friable myocardium
• Reduce cut-through
• Maintain a symmetric ring-to-myocardium interface, preserving coaxiality and hemostasis

4.2 Symmetry is functional, not cosmetic

An asymmetric ring can lead to:

• Cannula tilt (often septum-facing)
• Local gaps/oozing
• Progressive instability as the ventricle remodels under unloading

5) “Before you connect”: direct LV inspection as a mandatory safety step

Immediately before final connection:

• Inspect the LV cavity for thrombus and debris (tissue tags, suture fragments)
• Reconfirm cannula position and clearance

This step is disproportionately valuable because early complications are often geometry + substrate problems: maldirection creates intermittent collapse, while residual debris can seed thrombosis.

6) Common failure modes and how the inflow technique prevents them

6.1 Suction events / intermittent low flow

Mechanism: cannula mouth intermittently apposes septum or trabeculated wall.

Prevention bundle: accurate apex selection + echo-confirmed trajectory + aggressive trabeculation/muscle resection + avoid septum-facing alignment.

6.2 Pump thrombosis and embolic events

While anticoagulation is a major determinant, flow stability and avoidance of recurrent suction likely reduce thrombogenic conditions. Outcome studies consistently identify neurologic events and device complications as major morbidities during support. [1–3]

7) Practical operative checklist (LV inflow)

1. Map coronaries (LAD/Dx/PD) → mark safe apical zone.
2. Confirm muscular dimple; add TEE/epicardial echo if trajectory is uncertain.
3. Ventriculotomy + coring.
4. Resect trabeculations/muscle until cannula will sit unobstructed and non–septum-facing.
5. Place symmetric, pledgeted sutures for durable ring fixation.
6. Inspect LV for thrombus/debris; reconfirm cannula direction before final connection.

8) Adjunct strategy when standard apical inflow is suboptimal (selected anatomy)

A technical gap in the broader EXCOR literature is the absence of detailed, consensus-level guidance on apical landmarks and cannula angle optimization. [1] However, alternative inflow strategies have been reported for specific physiologies—e.g., in small, restrictive ventricles with dynamic obstruction risk, a novel inflow approach has been described using a modified strategy to obtain a more reliable filling source (case-level evidence). [4]

References

[1] 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.

[2] Di Molfetta A, Gandolfo F, Filippelli S, et al. The Use of Berlin Heart EXCOR VAD in Children Less than 10 kg: A Single Center Experience. Front Physiol. 2016;7:614.

[3] Almond CS, Morales DL, Blackstone EH, et al. Berlin Heart EXCOR pediatric ventricular assist device for bridge to heart transplantation in US children. Circulation. 2013;127(16):1702-1711.

[4] Ma M, Yarlagadda VV, Rosenthal DN, Maeda K. A novel inflow cannulation strategy for pediatric mechanical circulatory support in small left ventricles. J Thorac Cardiovasc Surg. 2017;154(3):e47-e48.

[5] Morales DLS, Almond CSD, Jaquiss RDB, et al. 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.

[6] 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.

[7] Hetzer R, Kaufmann F, Delmo Walter EM. Paediatric mechanical circulatory support with Berlin Heart EXCOR: development and outcome of a 23-year experience. Eur J Cardiothorac Surg. 2016;50(2):203-210.

[8] Morales DLS, Zafar F, Almond CS, et al. Berlin Heart EXCOR use in patients with congenital heart disease. J Heart Lung Transplant. 2017;36(11):1209-1216.

[9] Davis LM, Lee MGY, Sheridan BJ, et al. Berlin Heart EXCOR Support in the First Year of Life: A Single Centre Experience. Heart Lung Circ. 2021;30(3):446-453.

[10] Almond CS, Buchholz H, Massicotte P, et al. Berlin Heart EXCOR Pediatric ventricular assist device Investigational Device Exemption study: study design and rationale. Am Heart J. 2011;162(3):425-435.e6.