In this episode, CathMasters hosts Drs. Nazli Okumus and Daniel Ambinder, joined by expert faculty Drs. Ann Gage and Marwan Jumean, examine the foundational principles of veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Utilizing a case study of a 36-year-old patient with fulminant myocarditis and biventricular failure, the panel analyzes the VA-ECMO circuit's anatomy, clinical indications and contraindications, and the supporting evidence across various shock etiologies. The discussion also covers the debate over left ventricular (LV) unloading, the vital function of multidisciplinary shock teams, and strategies for informed consent and family counseling. This episode serves as an introduction to future discussions on cannulation techniques and complication management. Audio editing for this episode was performed by CardioNerds Intern, Dr. Julia Marques Fernandes.
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Pearls
"ECMO is an egotistical machine." Inflow and outflow are referenced from the perspective of the ECMO circuit — inflow = blood entering the machine (venous/drainage cannula); outflow = blood leaving the machine (arterial/return cannula).
VA-ECMO is the only temporary mechanical circulatory support (MCS) device that provides both full circulatory and respiratory support — making it uniquely suited for biventricular failure with concomitant hypoxemia, as in fulminant myocarditis.
"VA-ECMO increases LV afterload" — but the hemodynamic story is more nuanced. The venous drainage cannula reduces right-sided preload, which may decrease LV filling and partially counterbalance the increase in afterload. Not every patient requires mechanical LV unloading; the loading conditions and contractility of both ventricles must be considered.
Randomized controlled trial data for VA-ECMO in cardiogenic shock (ECLS-SHOCK, ECMO-CS) have been neutral. However, underlying diagnosis matters: survival is highest in fulminant myocarditis (~65%) and primary graft failure, and lowest in postcardiotomy shock (mortality ~65–75%).
Shock teams improve outcomes. Multicenter data demonstrate that centers with shock teams have ~28% lower adjusted odds of cardiac ICU (CICU) mortality (adjusted OR 0.72), driven by earlier recognition, increased pulmonary artery catheter (PAC) use, and more appropriate deployment of MCS.
Notes
Anatomy of the VA-ECMO Circuit
ECMO = Extracorporeal Membrane Oxygenation. VA-ECMO does the work of both the heart and the lungs — it provides full circulatory support and gas exchange, normalizing pCO2, pO2, and pH.
The circuit is the complete path blood travels from venous drainage to arterial return. Deoxygenated blood is drained via a large-bore venous cannula → centrifugal pump → membrane oxygenator (gas exchange) → oxygenated blood returned via a large-bore arterial cannula.
The two cannulas have three interchangeable naming conventions: Venous/Arterial, Inflow/Outflow (relative to the machine), or Drainage/Return (relative to the patient).
Peripheral VA-ECMO is placed percutaneously (Seldinger technique), often by an interventional cardiologist, surgeon, or critical care physician. The most common configuration is femoro-femoral: venous cannula tip at the SVC-RA junction, arterial cannula tip in the descending aorta. Alternatives include IJ venous/axillary arterial, or percutaneous left atrial VA-ECMO via transseptal cannulation (e.g., TandemHeart system or multi-stage cannula).
Central VA-ECMO requires surgical anastomosis to intrathoracic vessels; most commonly used in postcardiotomy patients.
A distal perfusion cannula (typically 5F–8F) is placed in the superficial femoral artery (SFA) to prevent limb ischemia.
Indications and Contraindications for VA-ECMO
VA-ECMO is indicated for acute, potentially reversible cardiac or cardiopulmonary failure when conventional therapies have failed. It serves as a bridge to recovery, a bridge to decision, or a bridge to advanced therapies (durable VAD or heart transplant).
Indications:
Cardiogenic shock (CS): AMI, fulminant myocarditis, acute decompensated biventricular HF, postcardiotomy shock, cardiac transplant primary graft failure, arrhythmic storm, drug overdose/cardiotoxicity
Massive pulmonary embolism (PE): Bridge to thrombectomy or thrombolysis
Extracorporeal cardiopulmonary resuscitation (ECPR): Refractory cardiac arrest
Procedural support: High-risk PCI or structural procedures
Contraindications:
Relative: Contraindication to systemic anticoagulation, severe PAD limiting peripheral access (central cannulation may be considered), aortic dissection, significant aortic insufficiency
Absolute: Comfort-focused goals of care, irreversible neurological catastrophe, conditions incompatible with recovery, limited life expectancy (e.g., end-stage malignancy), established irreversible multi-organ failure
Data for VA-ECMO Across Different Indications
The Extracorporeal Life Support Organization (ELSO) registry is the largest source of VA-ECMO outcomes data. Overall survival to hospital discharge for adult cardiac VA-ECMO is approximately 42% (Combes et al., Lancet 2020; 19,627 patients). Survival has remained relatively stable despite increasing utilization.
Survival varies significantly by underlying diagnosis (Danial et al., JACC 2023; Guglin et al., JACC 2019):
Fulminant myocarditis: ~65% survival (highest)
Primary graft failure after heart transplant: >50%
Drug overdose/cardiotoxicity: >50%
AMI-related CS: ~35–47%
Postcardiotomy shock: ~25–35% survival (poorest outcomes)
ECPR in adults: ~29.5% survival (ELSO 2022 report)
Pre-ECMO risk factors for poor outcomes: older age, higher BMI, renal/hepatic/CNS dysfunction, longer pre-ECMO mechanical ventilation, elevated lactate, reduced prothrombin activity, and pre-ECMO cardiac arrest.
The SAVE (Survival After Veno-Arterial ECMO) score is the most widely cited risk prediction tool, incorporating diagnosis, age, weight, organ function, and pre-ECMO intubation duration. AUROC 0.68 in derivation, 0.90 in external validation (Schmidt et al., Eur Heart J 2015).
Key RCT data:
ECLS-SHOCK (NEJM 2023): Largest RCT; AMI-CS patients randomized to early VA-ECMO vs. standard care. No difference in 30-day mortality (47.8% vs. 49.0%; RR 0.98; p=0.81). More bleeding/vascular complications with ECMO.
ECMO-CS (Circulation 2023): 117 patients with rapidly deteriorating/severe CS (multiple etiologies) randomized to immediate VA-ECMO vs. early conservative strategy. No difference in composite primary endpoint at 30 days (63.8% vs. 71.2%; HR 0.72; p=0.21). Post-hoc analyses suggest potential benefit in patients with CI <2.2 L/min/m², SvO2 <60%, or elevated pCO2 gap (Ostadal et al., Crit Care 2025).
IPD meta-analysis of four RCTs (Zeymer et al., Lancet 2023): No mortality benefit with routine VA-ECMO in AMI-CS; more complications in the device group.
ECPR data:
ARREST (Lancet 2020): Refractory OHCA with VF; stopped early for superiority — 43% vs. 7% survival to discharge.
Prague OHCA (JAMA 2022): Shockable and non-shockable rhythms; 180-day neurologically favorable survival 31.5% vs. 22.0% (p=0.09); 30-day neurologic recovery significantly better (30.6% vs. 18.2%; p=0.02).
INCEPTION (NEJM 2023): Multicenter; refractory OHCA with ventricular arrhythmias; 30-day favorable neurologic outcome 20% vs. 16% (OR 1.4; p=0.52). Longer cannulation times and lower-volume centers may have contributed to neutral results.
Pooled analysis of ARREST + Prague OHCA (Belohlavek et al., EClinicalMedicine 2023): Significant benefit for ECPR in shockable rhythms — 47.1% vs. 28.3% neurologically favorable survival at 180 days (NNT = 5).
The 2023 AHA Focused Update on Adult ACLS (Circulation 2024) gives a Class 2b (conditional) recommendation for ECPR in select patients with refractory OHCA at experienced, high-volume centers.
LV Unloading on VA-ECMO
VA-ECMO increases LV afterload via retrograde aortic flow. The concern: increased afterload → elevated LVEDP/volume → increased myocardial O2 demand → worsened LV function → pulmonary congestion and LV stasis.
The nuance: The venous drainage cannula directly drains the right heart, reducing RA preload and RV stroke volume. On the ascending limb of the Frank-Starling curve, decreased RV preload → less LV filling, partially counterbalancing the afterload increase. The hemodynamic response depends on loading conditions and contractility of both ventricles (University of Minnesota group, in vivo data).
LV unloading strategies: IABP (reduces afterload, improves coronary perfusion), micro-axial flow pump/Impella (directly unloads LV), transseptal LA cannulation, atrial septostomy, surgical LV apical drainage.
Observational data (Schrage et al., Circulation 2020): LV unloading associated with lower mortality in a multicenter cohort.
RCTs have not confirmed the benefit of routine unloading:
EARLY-UNLOAD (Circulation 2023): Early LV unloading vs. conventional approach — no mortality difference (46.6% vs. 44.8%; p=0.94).
EVOLVE-ECMO (Eur J Heart Fail 2023): Early LA venting vs. conventional — no difference in ECMO weaning or survival.
Practical consideration: Many operators deploy upfront unloading because the patient is already in the cath lab, avoiding repeated transport on ECMO. The decision should also factor in the goal of ECMO (LV recovery vs. bridge to replacement therapy).
The Role of the Shock Team
Shock teams are multidisciplinary groups (interventional cardiology, heart failure/transplant, cardiac surgery, critical care, and anesthesiology) that facilitate early recognition, evaluation, and management of CS.
Multicenter data (Papolos et al., JACC 2021; >1,200 CS admissions): Centers with shock teams had ~28%
