Central VA-ECMO #2: Operative Technique

Central venoarterial extracorporeal membrane oxygenation (VA-ECMO) is commonly established through an existing median sternotomy when severe postcardiotomy cardiac failure prevents safe separation from cardiopulmonary bypass (CPB) or when profound cardiac failure develops shortly after bypass. In a large postcardiotomy cohort, failure to wean from CPB accounted for 38% of indications and post-weaning heart failure for 48% [1]. Central cannulation offers immediate surgical access to the heart and great vessels, direct aortic return and right-atrial drainage, and the ability to perform surgical left-heart decompression.

The operative goal is not simply to generate maximal circuit flow. Central VA-ECMO must provide adequate systemic perfusion while avoiding complications created by the interaction between extracorporeal flow, residual ventricular function, recent cardiac surgery, anticoagulation, and an open mediastinum. The essential sequence is meticulous hemostasis, secure central cannulation, controlled initiation of flow, repeated assessment of ventricular loading, selective left-heart decompression, and safe temporary chest coverage.

1. Operative Context and Choice of Central Access

Central VA-ECMO is particularly suited to the postcardiotomy patient whose sternum is already open. The conventional configuration consists of arterial return to the ascending aorta and venous drainage from the right atrium. This arrangement provides antegrade systemic arterial flow and allows direct inspection of cannula position, ventricular size, filling, and mediastinal bleeding.

Central access, however, is not universally superior. Comparative postcardiotomy data are retrospective and potentially confounded by illness severity and operative complexity. In a multicenter registry and meta-analysis of 781 patients, central cannulation was associated with higher hospital mortality (OR 1.54), more reoperation for bleeding or tamponade (OR 1.96), and greater requirement for transfusion of more than nine units of red blood cells (OR 2.42) than peripheral cannulation [1]. A separate meta-analysis of 1,691 patients found comparable in-hospital survival between central and peripheral configurations, while peripheral access was associated with less bleeding, hemofiltration, and transfusion [2]. These findings support an individualized cannulation strategy rather than a single preferred approach.

2. Hemostasis Before ECMO Initiation

Strict hemostasis is a core component of central VA-ECMO implantation. The postcardiotomy patient may already have platelet dysfunction, hemodilution, residual anticoagulant effect, coagulation-factor consumption, tissue injury, and multiple fresh suture lines. Once ECMO begins, continued anticoagulation and circuit-related hemostatic abnormalities may magnify relatively small surgical bleeding sites.

The mediastinum should therefore be inspected systematically. Particular attention should be paid to aortic and atrial cannulation sites, cardioplegia and vent sites, atriotomy or aortotomy closures, conduit or patch suture lines, pulmonary artery reconstruction, raw mediastinal surfaces, thymic tissue, pericardial edges, and sternal marrow.

In neonates and infants, even moderate drainage can represent a substantial fraction of circulating blood volume and rapidly lead to repeated transfusion and worsening coagulopathy. The association between central access and bleeding-related complications reinforces the importance of meticulous surgical hemostasis [1,2].

Hemostasis must nevertheless be balanced against the urgency of circulatory rescue. In profound shock, ECMO should not be delayed excessively for diffuse low-grade bleeding when systemic perfusion is critically inadequate. Once support stabilizes circulation, the field can be reassessed under controlled hemodynamic conditions.

3. Central Cannulation

The conventional central configuration uses the ascending aorta for arterial return and the right atrium for venous drainage. If the patient is transitioning directly from CPB, existing cannulation sites may be retained or revised according to cannula size, position, expected support duration, and operative anatomy.

The arterial cannula should be positioned in a secure segment of the ascending aorta, away from fragile reconstruction or competing suture lines when possible. Its direction should avoid wall impingement, mechanical distortion, and excessive tension. The cannulation site must be constructed for prolonged support rather than for short-duration bypass alone.

Venous drainage is usually obtained from the right atrium using a large-bore cannula. Poor drainage may result from malposition, atrial-wall apposition, insufficient preload, tubing obstruction, or excessive negative pressure. The right atrium should decompress without repeated collapse around the cannula.

No comparative evidence establishes an optimal operative cannulation geometry specifically for central postcardiotomy VA-ECMO. Cannula size and position should therefore be individualized to patient size, anatomy, desired flow, previous reconstruction, and the need to preserve safe surgical access.

4. Controlled Initiation and Flow Titration

After connection and de-airing, ECMO flow should be increased progressively while hemodynamic and mechanical responses are observed. In profound cardiac failure, support may approach full predicted cardiac output or exceed it when required, but the ultimate target is adequate organ perfusion rather than a fixed numerical flow.

Assessment should include systemic arterial pressure, circuit flow and pressures, venous drainage, pulse pressure, right- and left-heart filling, aortic-valve opening, oxygenation, lactate trend, urine output, near-infrared spectroscopy when available, and direct inspection for new bleeding or cannula distortion.

Higher ECMO flow can restore perfusion but may also increase the load against which a severely dysfunctional left ventricle must eject. When clinically permissible, management of LV distension may include individualized reduction in ECMO flow, optimization of venous drainage and cannula position, vasodilators to reduce afterload, selective inotropic support to promote native ejection, diuresis, and ventilator or PEEP adjustment [3,4].

Flow reduction is not appropriate when it compromises systemic perfusion. The practical target is the lowest flow that reliably supports organ perfusion while avoiding unnecessary LV afterload.

5. Why LV Distension Occurs During VA-ECMO

VA-ECMO does not completely eliminate blood entering the left heart. Pulmonary venous return persists because of bronchial circulation, Thebesian flow, incomplete right-heart drainage, and residual pulmonary blood flow. If LV contractility is severely depressed, the ventricle may be unable to eject this volume effectively against the arterial pressure generated by ECMO.

The resulting sequence is:

LV distension → increased LV end-diastolic pressure → increased left-atrial pressure → pulmonary venous hypertension → pulmonary congestion and pulmonary edema.

Progressive LV distension also increases myocardial wall stress and oxygen demand, potentially opposing myocardial recovery. When the aortic valve remains closed, stasis may develop in the LV and aortic root, increasing the risk of spontaneous echo contrast and thrombus formation.

Persistent LV distension, poor or absent aortic-valve opening, minimal pulsatility, pulmonary congestion or edema, rising left-sided filling pressures, refractory arrhythmia, spontaneous echo contrast, and intracardiac stasis or thrombosis are commonly used signals that additional unloading should be considered [5,6].

6. Left-Heart Decompression and the LA Vent

In an open-chest postcardiotomy setting, surgical left-heart venting is a direct unloading option. An LA vent can reduce left-atrial pressure and indirectly reduce LV filling and distension. The objectives are to lower pulmonary venous pressure, reduce ventricular wall tension, limit pulmonary edema, improve myocardial unloading, and reduce left-heart blood stasis.

Not every patient requires a vent. A patient with meaningful native ejection, regular aortic-valve opening, acceptable pulsatility, stable LV dimensions, and no pulmonary congestion may remain adequately unloaded with optimized ECMO flow and medical management. Conversely, an akinetic LV with a persistently closed aortic valve and progressive pulmonary edema should prompt early consideration of direct decompression.

Surgical venting may be performed through the sternotomy, and several left-atrial or left-ventricular decompression techniques have been described [7,8]. Current literature does not define a single optimal surgical vent location, cannula size, drainage target, or timing strategy specifically for central postcardiotomy VA-ECMO. Technique should therefore be selected according to operative anatomy, ventricular physiology, previous reconstruction, bleeding risk, and anticipated duration of support.

Excessive vent suction can collapse the atrium, entrain air, or create unstable drainage; insufficient venting may fail to control LV distension. Vent flow should therefore be titrated together with ECMO flow and native cardiac ejection.

7. Evidence for Early and Targeted Unloading

Observational evidence supports LV unloading when clinically indicated. In a meta-analysis including 3,997 patients supported with VA-ECMO, LV unloading was associated with lower mortality, approximately 54% versus 65%, although hemolysis was more frequent [9]. These data support active attention to ventricular unloading but do not prove that routine prophylactic unloading is superior for every patient or identify the best method for central postcardiotomy support.

Modern unloading strategies also include transseptal or pulmonary-artery-based approaches, but some contemporary data derive specifically from peripheral VA-ECMO populations [10]. These findings should not be extrapolated directly to the open-chest central configuration, where surgical access, bleeding risk, cannula geometry, and direct LA or LV venting are different.

The practical strategy is therefore early physiologic surveillance and targeted unloading rather than a universal venting protocol.

8. Cannula Security and Open-Chest Management

Once satisfactory support has been achieved, all cannulae and vent lines should be rechecked. Potentially catastrophic complications include arterial cannula dislodgement, venous cannula migration, tubing kinking, atrial-wall obstruction, tension on cannulation sites, and compression beneath temporary chest coverage.

Cannulae should be securely fixed and routed so that transport, repositioning, radiography, dressing changes, and delayed sternal closure do not create traction or distortion. The exit path should provide sufficient mobility without redundant loops that can kink.

The sternum frequently remains open because myocardial edema, cannula position, hemodynamic instability, or the need for rapid re-entry makes immediate closure undesirable. A temporary sterile membrane or patch protects the mediastinum while avoiding compression of the heart and circuit components.

After temporary coverage is applied, circuit function should be reassessed because tubing redirection or closure can alter cannula angle and drainage.

9. Final Operative Assessment

Before transfer to the intensive care unit, the team should confirm stable circuit function, adequate systemic perfusion, acceptable venous drainage, controlled mediastinal bleeding, secure cannula fixation, and appropriate ventricular unloading.

Particular attention should be given to LV size, aortic-valve opening, pulse pressure, pulmonary congestion, and vent function. These variables establish the baseline for subsequent assessment of myocardial recovery and weaning readiness.

Central VA-ECMO is a dynamic interaction between the circuit and native circulation. Excessive flow may worsen LV loading; inadequate flow may compromise organ perfusion; excessive drainage can collapse cardiac chambers; and insufficient unloading can produce pulmonary edema and intracardiac stasis.

10. Practical Surgical Principles

The operative priorities can be summarized as four linked objectives:

Perfusion: provide sufficient extracorporeal flow to restore systemic oxygen delivery.

Drainage: obtain stable systemic venous drainage without chamber collapse or excessive negative pressure.

Decompression: recognize afterload-related LV distension early and use flow adjustment, medical measures, or direct venting when indicated.

Protection: control surgical bleeding, secure every cannula, and maintain safe open-chest coverage.

The endpoint is not maximal ECMO flow. It is a stable circulation in which systemic perfusion is adequate, the left heart is not progressively distending, pulmonary congestion is controlled, cannulae remain mechanically secure, and bleeding is manageable. This balance provides the environment for myocardial recovery, reassessment, and eventual transition toward weaning or another definitive support strategy.

Key Points

• Central VA-ECMO is particularly applicable to severe postcardiotomy failure through an existing median sternotomy.
• Comparative observational studies do not establish universal superiority of central over peripheral cannulation; central access may carry greater bleeding and transfusion burden in some cohorts [1,2].
• The standard central configuration uses ascending-aortic arterial return and right-atrial venous drainage.
• Meticulous hemostasis is essential because postoperative coagulopathy and ECMO anticoagulation can amplify surgical bleeding.
• ECMO flow should be titrated to systemic perfusion while avoiding unnecessary LV afterload; flow reduction is appropriate only when organ perfusion remains adequate [3,4].
• Progressive LV distension, poor aortic-valve opening, pulmonary edema, rising filling pressures, arrhythmia, or intracardiac stasis are important indications to consider additional unloading [5,6].
• Surgical LA or LV venting is practical during central open-chest support, but evidence does not define one optimal technique [7,8].
• Observational data associate LV unloading with lower mortality but increased hemolysis; these findings do not support mandatory unloading in every patient [9].
• Evidence for some newer unloading strategies is derived from peripheral VA-ECMO and should not be extrapolated directly to central postcardiotomy support [10].
• Successful central VA-ECMO requires continuous integration of perfusion, drainage, ventricular unloading, hemostasis, and cannula security.

References

[1] Mariscalco G, Salsano A, Fiore A, Dalén M, Ruggieri VG, Saeed D, et al. Peripheral versus central extracorporeal membrane oxygenation for postcardiotomy shock: Multicenter registry, systematic review, and meta-analysis. J Thorac Cardiovasc Surg. 2019. doi:10.1016/j.jtcvs.2019.10.078.

[2] Raffa GM, Kowalewski M, Brodie D, Ogino MT, Whitman G, Meani P, et al. Meta-analysis of peripheral or central extracorporeal membrane oxygenation in postcardiotomy and non-postcardiotomy shock. Ann Thorac Surg. 2019. doi:10.1016/j.athoracsur.2018.05.063.

[3] Amarelli C, Musumeci F, Loforte A, Montalto A, Di Franco S, Hernández-Montfort J. Flow optimization, management, and prevention of LV distention during VA-ECMO. In: Advances in Extra-corporeal Perfusion Therapies. 2018. doi:10.5772/INTECHOPEN.80265.

[4] Welker CC, Huang J, Boswell M, Spencer P, Villavicencio MA, Ramakrishna H. Left ventricular decompression in VA-ECMO: Analysis of techniques and outcomes. J Cardiothorac Vasc Anesth. 2022. doi:10.1053/j.jvca.2022.07.024.

[5] Xie A, Forrest P, Loforte A. Left ventricular decompression in veno-arterial extracorporeal membrane oxygenation. Ann Cardiothorac Surg. 2019. doi:10.21037/acs.2018.11.07.

[6] Lim Y, Kim MC, Jeong IS. Left ventricle unloading during veno-arterial extracorporeal membrane oxygenation: Review with updated evidence. Acute Crit Care. 2024. doi:10.4266/acc.2024.00801.

[7] Jo YE, Seong J, Cho H, Kim DW, Lim Y, Cho Y, et al. Left heart venting or unloading strategies for VA-ECMO patients: Indications, timing, and techniques: A narrative review. J Cardiovasc Interv. 2025. doi:10.54912/jci.2025.0002.

[8] Ricarte Bratti JP, Cavayas Y, Noly P, Serri K, Lamarche Y. Modalities of left ventricle decompression during VA-ECMO therapy. Membranes. 2021;11(3):209. doi:10.3390/membranes11030209.

[9] Russo J, Aleksova N, Pitcher I, Couture É, Parlow S, Faraz M, et al. Left ventricular unloading during extracorporeal membrane oxygenation in patients with cardiogenic shock. J Am Coll Cardiol. 2019;73(6):654-662. doi:10.1016/j.jacc.2018.10.085.

[10] Inglis S, Rosenbaum AN, Rizzo SA, Anderson JH, Yalamuri S, Spencer P, et al. Novel left ventricular unloading strategies in patients on peripheral venoarterial extracorporeal membrane oxygenation support. ASAIO J. 2024. doi:10.1097/MAT.0000000000002136.