Central VA-ECMO #1: Indications and Core Principles

1. Overview

Central venoarterial extracorporeal membrane oxygenation (VA-ECMO) provides temporary cardiopulmonary support by draining systemic venous blood directly from the heart, passing it through an extracorporeal pump and oxygenator, and returning oxygenated blood to the central arterial circulation. A typical central configuration uses right atrial venous drainage and ascending aortic arterial return, usually through a median sternotomy.

Central VA-ECMO is particularly relevant after cardiac surgery because the chest is already open, the right atrium and ascending aorta are directly accessible, and rapid conversion from cardiopulmonary bypass (CPB) to prolonged mechanical circulatory support may be possible. Failure to separate from CPB and severe cardiac failure after initial CPB separation are among the most common circumstances in which postcardiotomy VA-ECMO is instituted [1]. (PubMed)

Central and peripheral VA-ECMO should not be viewed as competing strategies with a universally superior option. Rather, cannulation should be selected according to anatomy, required flow, vascular access, ventricular function, anticipated duration of support, bleeding risk, and the need for direct cardiac decompression or surgical reintervention [1,2].

2. Basic Central VA-ECMO Configuration

The fundamental circuit consists of:

1. Venous drainage from the right atrium
2. Extracorporeal centrifugal pump
3. Membrane oxygenator
4. Arterial return to the ascending aorta

Direct right atrial drainage allows placement of a relatively large, short venous cannula. This is important because achievable ECMO flow depends heavily on adequate venous return to the pump. Excessive resistance to drainage can produce negative inlet pressure, atrial or venous collapse, cannula chatter, unstable circuit flow, and hemolysis.

The arterial cannula returns blood directly into the ascending aorta. This produces antegrade systemic perfusion, in contrast with femoral arterial VA-ECMO, in which blood travels retrograde through the descending thoracic and ascending aorta. Central arterial return therefore avoids the characteristic retrograde mixing pattern that can produce differential upper-body hypoxemia, or Harlequin syndrome, when native ventricular ejection is poorly oxygenated [2]. (PubMed)

Direct central cannulation also avoids dependence on the diameter of peripheral arteries and veins. This can be particularly important in neonates, infants, and small children, in whom peripheral vessel size may limit cannula diameter and therefore maximum achievable ECMO flow.

3. When Should Central VA-ECMO Be Considered?

A central strategy is most attractive when peripheral cannulation cannot reliably provide the flow or cardiac decompression required for adequate support.

Potential scenarios include:

• Failure to separate from CPB after cardiac surgery
• Severe postcardiotomy ventricular dysfunction
• Refractory low cardiac output despite high-dose vasoactive therapy
• Requirement for unusually high indexed ECMO flows
• Peripheral vessels too small for adequate cannulation
• Complex systemic or venous anatomy
• Inadequate venous drainage with peripheral ECMO
• Need for direct surgical left-heart decompression
• Anticipated requirement for repeated mediastinal exploration or surgical revision

The indication is therefore physiologic rather than simply technical. The essential question is whether the chosen configuration can restore adequate systemic oxygen delivery while maintaining acceptable ventricular loading conditions.

4. Postcardiotomy Failure: The Classic Setting

Postcardiotomy shock is one of the principal indications for central VA-ECMO. In the multicenter series reported by Mariscalco and colleagues, 781 adults required VA-ECMO after cardiac surgery; failure to wean from CPB and severe heart failure after CPB separation accounted for most ECMO initiations [1]. (PubMed)

In congenital heart surgery, inability to separate from CPB should first trigger a systematic search for reversible causes rather than automatic transition to ECMO.

Important considerations include:

• Residual intracardiac or extracardiac obstruction
• Residual shunting
• Coronary artery compromise
• Pulmonary venous obstruction
• Systemic venous obstruction
• Important atrioventricular or semilunar valve dysfunction
• Pulmonary hypertensive crisis
• Abnormal preload or afterload
• Arrhythmia or conduction disturbance
• Air embolism
• Inadequate myocardial protection or ischemic injury

Epicardial or transesophageal echocardiography, direct pressure measurements, saturation measurements, surgical inspection, and occasionally catheter-based assessment may be necessary.

ECMO should not substitute for correction of a surgically correctable residual lesion.

When the anatomy is satisfactory but myocardial performance remains inadequate, however, prolonged attempts to separate from bypass with escalating catecholamine doses may increase myocardial oxygen consumption without restoring effective systemic perfusion. Central VA-ECMO can then provide time for myocardial recovery, diagnostic clarification, or definitive intervention.

5. Central VA-ECMO and High-Flow Support

A major practical advantage of central cannulation is the ability to provide high extracorporeal blood flow.

Maximum ECMO flow is determined not only by pump capability but also by cannula diameter, cannula length, vascular resistance, venous return, and circulating blood volume. Small peripheral vessels can become the limiting component of the circuit.

Central cannulation addresses several of these limitations:

• Larger cannulas can often be used.
• Cannula length is relatively short.
• Venous blood is drained directly from the right atrium.
• Arterial return is delivered directly into the ascending aorta.

This configuration may be particularly useful when systemic flow requirements are unusually high. One example is profound vasoplegic or septic physiology with low systemic vascular resistance, in which maintaining adequate perfusion pressure may require both vasopressor therapy and high indexed blood flow.

Central ECMO should not be selected simply because septic shock is present. The relevant indication is failure of a peripheral configuration to provide the systemic flow required by the patient's physiology.

6. Central Versus Peripheral VA-ECMO: Hemodynamic Differences

Peripheral VA-ECMO is less invasive and may avoid reopening or maintaining an open sternotomy. It can therefore be preferable when adequate flows are achievable and direct cardiac access is unnecessary.

Its hemodynamic disadvantage is that arterial blood delivered from a femoral cannula travels retrograde toward the ascending aorta. Increasing peripheral ECMO flow raises aortic pressure and may substantially increase the effective afterload faced by a severely dysfunctional left ventricle.

Central return also increases systemic arterial pressure and therefore can increase LV afterload; central cannulation does not eliminate the problem of LV distension. However, direct antegrade aortic return avoids the retrograde aortic perfusion pattern of femoral ECMO and simultaneously provides straightforward access for surgical unloading.

The clinical literature does not establish that either cannulation strategy is intrinsically superior. In 158 postcardiotomy patients, Radakovic and colleagues reported similar ECMO weaning rates and broadly similar rates of stroke, renal failure, ischemic complications, re-exploration, and transfusion, while central cannulation was associated with better 30-day survival and fewer arterial cannulation-site changes [2]. (PubMed Central (PMC))

In contrast, the larger multicenter analysis by Mariscalco and colleagues found that central cannulation was associated with greater hospital mortality, reoperation for bleeding or tamponade, and major transfusion requirements [1]. (ScienceDirect)

These apparently conflicting findings illustrate an important limitation: cannulation strategy is strongly influenced by patient severity and surgical context. Patients receiving central ECMO may be more critically ill, more likely to have failed CPB separation, and more likely to have active postoperative bleeding. Observational comparisons therefore remain highly susceptible to selection bias.

7. Why Left-Heart Distension Occurs During VA-ECMO

VA-ECMO restores systemic blood flow but does not necessarily unload the left heart.

Even with substantial right atrial drainage, blood continues to reach the left atrium through:

• Residual pulmonary blood flow
• Bronchial circulation
• Thebesian venous return
• Intracardiac or extracardiac shunts
• Aortic regurgitation, when present

At the same time, ECMO increases aortic pressure. If the LV is severely dysfunctional, it may become unable to eject against this increased afterload.

The resulting sequence is:

Reduced LV ejection → increased LV end-diastolic pressure → LA hypertension → pulmonary venous congestion → pulmonary edema

Progressive LV distension increases myocardial wall stress and oxygen demand and may compromise myocardial recovery. If the aortic valve remains closed, severe intracardiac blood stasis may develop, increasing the risk of LV or aortic-root thrombosis [3]. (Annals of Cardiothoracic Surgery)

Thus, successful ECMO management requires attention to two different objectives:

Systemic perfusion and cardiac decompression.

Adequate pump flow does not guarantee adequate ventricular unloading.

8. Recognizing Inadequate Left-Heart Decompression

There is no universally accepted single diagnostic criterion for LV overload during VA-ECMO [3]. Assessment should therefore integrate hemodynamic, echocardiographic, respiratory, and circuit findings.

Concerning features include:

• Progressive LA or LV enlargement
• Persistent absence of aortic valve opening
• Minimal arterial pulsatility
• Increasing LA or pulmonary venous pressure
• Progressive pulmonary edema
• Pulmonary hemorrhage
• Dense spontaneous echo contrast
• LV or aortic-root thrombus
• Persistent ventricular arrhythmias
• Failure of ventricular recovery despite otherwise adequate ECMO support

Serial echocardiography is particularly important because ventricular size, aortic valve opening, intracardiac stasis, valve regurgitation, and myocardial recovery can change rapidly during support.

9. Left Atrial Venting During Central VA-ECMO

One of the major practical advantages of central ECMO is the ability to perform direct surgical left-heart decompression.

A vent can be inserted through the right upper pulmonary vein into the LA or LV and connected to the venous limb of the ECMO circuit. Alternative surgical sites include the LA appendage, LV apex, and pulmonary artery [3]. (Annals of Cardiothoracic Surgery)

An LA vent reduces blood volume within the pulmonary venous–LA–LV compartment and can therefore:

• Reduce LA pressure
• Reduce LV filling and distension
• Reduce pulmonary venous hypertension
• Improve pulmonary edema
• Reduce LV wall stress
• Decrease intracardiac stasis
• Facilitate myocardial recovery

The goal is not necessarily to create a completely empty LV. Some degree of native ventricular filling and ejection may be desirable when compatible with adequate systemic support. Venting should instead prevent pathologic distension, pulmonary congestion, and blood stasis.

10. Left-Heart Decompression in Pediatric VA-ECMO

The issue is particularly important in pediatric ECMO because small children may have limited ventricular compliance and profound myocardial dysfunction.

In a retrospective study of 51 pediatric patients undergoing peripheral VA-ECMO, Lin and colleagues identified LV decompression as necessary in patients with profound LV dysfunction and reported successful ECMO removal in 76.5% and survival to discharge in 62.7% of the overall cohort [4]. (PubMed)

Pediatric unloading methods vary substantially. Depending on patient size, anatomy, cannulation configuration, and institutional practice, techniques may include:

• Surgical LA cannulation
• Direct LV venting
• Balloon atrial septostomy
• Transseptal LA drainage
• Atrial septal stenting
• Pulmonary artery venting
• Other mechanical unloading strategies

A contemporary systematic review found marked heterogeneity in both indications and techniques for pediatric LV decompression. Surgical approaches were used more frequently in central postcardiotomy ECMO, whereas catheter-based atrial decompression strategies were common during peripheral support [5]. The available evidence suggests potential benefit, particularly in postcardiotomy patients, but remains predominantly retrospective and does not define a single optimal unloading technique or timing strategy. (PubMed)

11. Does Decompression Improve Survival?

The physiologic rationale for decompression is strong, but clinical outcome data require cautious interpretation.

A 2025 analysis of 377 postoperative infants in the Chinese extracorporeal life-support registry included 141 patients who underwent left-heart decompression. Decompression was associated with improved early survival at 24 hours but not with a clear improvement in hospital survival; bleeding and mechanical complications were more frequent among decompressed patients [6]. (ResearchGate)

This finding is clinically important. Patients selected for decompression frequently have more severe LV dysfunction, making simple comparisons between vented and non-vented patients difficult. In addition, decompression itself introduces risks including bleeding, cardiac injury, cannula-related complications, thromboembolism, and procedural instability.

Accordingly, current pediatric evidence supports selective decompression based on ventricular physiology rather than routine venting of every VA-ECMO patient [5,6].

12. Open-Chest Management

Central ECMO after congenital heart surgery frequently involves temporary open-chest management.

Leaving the sternum open may:

• Avoid compression of an edematous heart
• Facilitate high-flow central cannulation
• Permit rapid control of postoperative bleeding
• Allow cannula repositioning
• Facilitate direct assessment of cardiac filling and contractility
• Provide immediate access if surgical revision is required

The disadvantages include mediastinal bleeding, infection risk, cannula instability, and the logistical complexity of prolonged open-chest care.

The decision to leave the chest open, tunnel the cannulas, or perform delayed sternal closure should therefore depend on hemodynamic stability, myocardial edema, bleeding, expected support duration, and anticipated need for re-entry.

13. Monitoring the Effectiveness of Central VA-ECMO

ECMO effectiveness should never be assessed from pump flow alone. The therapeutic endpoint is adequate systemic oxygen delivery with favorable ventricular loading conditions.

Monitoring should integrate:

• ECMO flow indexed to weight or body surface area
• Mean arterial pressure
• Arterial and venous oxygen saturation
• Lactate clearance
• Cerebral and somatic NIRS
• Urine output
• Acid-base status
• Renal and hepatic function
• Vasoactive requirement
• Arterial pulse pressure
• Aortic valve opening
• LV and LA dimensions
• Ventricular systolic function
• Pulmonary edema
• Intracardiac stasis or thrombosis

Increasing native pulsatility, improved ventricular contraction, and consistent aortic valve opening may indicate myocardial recovery. Conversely, persistently closed aortic valve, increasing LV dimensions, worsening pulmonary edema, or intracardiac stasis should prompt reassessment of loading conditions and the adequacy of decompression.

14. Practical Surgical Decision-Making

A useful decision sequence is:

1. Is systemic perfusion inadequate despite appropriate medical therapy?

2. Is the underlying myocardial dysfunction potentially reversible or bridgeable?

3. Have important residual surgical lesions been excluded or corrected?

4. Can peripheral cannulation provide the required flow safely?

5. If peripheral support is flow-limited, would central RA-to-aorta cannulation provide more reliable support?

6. Is the left heart adequately decompressed?

7. If not, what unloading strategy is most appropriate for this anatomy and clinical setting?

Central VA-ECMO should therefore be regarded not simply as a cannulation technique, but as an integrated strategy combining high-flow systemic perfusion, direct cardiac access, assessment of residual anatomy, and active management of ventricular loading.

The key principle is:

Use central VA-ECMO when direct central cannulation provides the systemic flow, surgical access, or left-heart decompression required to achieve effective support when a peripheral strategy is inadequate or inappropriate.

References

[1] Mariscalco G, Salsano A, Fiore A, et al. Peripheral versus central extracorporeal membrane oxygenation for postcardiotomy shock: multicenter registry, systematic review, and meta-analysis. J Thorac Cardiovasc Surg. 2020;160(5):1207-1216.e44. (PubMed)

[2] Radakovic D, Hamouda K, Penov K, et al. Central versus peripheral arterial cannulation for veno-arterial extracorporeal membrane oxygenation in post-cardiotomy patients. ASAIO J. 2021;67(1):67-73. (PubMed)

[3] Xie A, Forrest P, Loforte A. Left ventricular decompression in veno-arterial extracorporeal membrane oxygenation. Ann Cardiothorac Surg. 2019;8(1):9-18. (PubMed)

[4] Lin YJ, Liu HY, Kuo H, Huang CF, Hsu M, Cheng M, et al. Left ventricle decompression strategies in pediatric peripheral extracorporeal membrane oxygenation. Acta Cardiol Sin. 2019;35(3):335-341. (PubMed)

[5] Veronese G, Meani P, Sirico D, et al. Left ventricular decompression in paediatric veno-arterial extracorporeal life support: reviewing the evidence. ESC Heart Fail. 2025;12(4):2711-2725. (PubMed)

[6] Lu R, Wang Y, Wang L, Li C, Hao X, Wang H, et al. The impact of left heart decompression on venous-arterial extracorporeal membrane oxygenation in infancy patients after cardiac surgery: an analysis of the Chinese Extracorporeal Life Support Registry. ASAIO J. 2025;71(Suppl 5):11. (ResearchGate)