3.8 Expert Consensus on Right Ventricular Injury in V-V ECMO

Extracorporeal membrane oxygenation (ECMO) serves as the ultimate rescue therapy for severe acute respiratory distress syndrome (ARDS) and refractory respiratory failure, with clinical application growing exponentially over the past decade. In practice, right heart injury and dysfunction/failure are among the most common and challenging complications during veno-venous extracorporeal membrane oxygenation (V-V ECMO) operation, with incidence fluctuating between 20%–50% across cohorts, significantly increasing in-hospital mortality and decannulation failure rates. The right heart system, as the power source for pulmonary circulation, is extremely sensitive to afterload changes. The pathophysiological basis of ARDS-induced right heart injury involves multiple factors: elevated pulmonary vascular resistance, hypoxic pulmonary vasoconstriction, hypercapnia, microthrombosis, and inappropriate mechanical ventilation strategies further exacerbate this burden.

1. Background of Right Heart Injury in ARDS

Despite widespread guideline inclusion of “low tidal volume lung-protective ventilation” for ARDS, mortality in severe ARDS remains high. V-V ECMO, as an extracorporeal life support technique, drains venous blood percutaneously, oxygenates it via a membrane lung, removes CO₂, and returns it to the venous system, achieving “lung rest” and correcting severe gas exchange impairment, buying time for lung tissue repair. However, V-V ECMO only provides respiratory support; circulatory stability entirely depends on native left and right ventricular function. In this complex pathophysiological network, the right ventricle holds a core position. Previous studies show extremely high incidence of acute cor pulmonale or right ventricular (RV) dysfunction in ARDS patients. Literature reports RV failure incidence at 10%–25% in ARDS; in critically ill subgroups requiring V-V ECMO, this proportion rises significantly, sometimes exceeding 50%. This high incidence reflects both disease severity and potential iatrogenic or technical factors during ECMO therapy. Multiple large-scale retrospective studies and meta-analyses confirm that V-V ECMO patients with RV dysfunction have significantly prolonged ICU stay, reduced decannulation success rates, and increased 28-day and in-hospital mortality. Thus, early identification, precise assessment, and effective intervention of right heart injury hold irreplaceable clinical value for improving overall prognosis in V-V ECMO patients.

2. Definition and Pathophysiological Mechanism of Right Heart Injury

In the field of critical respiratory failure treatment, V-V ECMO introduction is undoubtedly a milestone. However, clinical practice often faces a paradox: despite ECMO effectively improving blood gas indices, some patients still die from circulatory failure. The key driver behind this phenomenon is often the overlooked right ventricle.

Long-term clinical use of the terms “right heart insufficiency,” “right heart failure,” and “right heart injury” has been highly arbitrary, leading to misalignment in diagnostic and therapeutic windows. Right heart injury encompasses the entire process from early RV structural changes (dilation) and functional impairment to final hemodynamic collapse. The primary contribution of the Expert Consensus on Right Heart Injury in V-V ECMO Patients is clearly defining the pathophysiological boundaries of right heart injury, emphasizing that they represent different stages of the same pathological process and are absolutely not interchangeable.

Right ventricular dilation is the early compensatory/adaptative stage. Facing early volume or acute/chronic pressure load increases, RV structural dilative changes occur, but RV function is normal or near-normal, and hemodynamics are stable.

Right heart insufficiency is a transitional stage. This specifically refers to abnormal hemodynamic indices with paradoxical septal motion and impaired contractile function (e.g., changes in tricuspid annular plane systolic excursion [TAPSE] and right ventricular fractional area change [RVFAC]), but the body can still maintain cardiac output via compensatory mechanisms such as increased heart rate and vasoconstriction, without hypoperfusion shock.

Right heart failure is a decompensated state. This involves marked RV contractile dysfunction and severe paradoxical septal motion, with RV dilation restricting left ventricular (LV) diastole; blood flow fails to meet metabolic demands, clinically presenting as systemic venous congestion and low cardiac output shock.

The clinical value of this conceptual stratification lies in advancing the therapeutic window, enabling early identification of right heart injury and early intervention before hemodynamic deterioration. Understanding the pathophysiological basis requires starting from RV–pulmonary artery (RV-PA) coupling theory. The RV, as a thin-walled, high-compliance volume pump, is extremely sensitive to afterload changes. Physiologically, the ratio of RV end-systolic elastance (Ees, representing contractility) to pulmonary artery elastance (Ea, representing afterload) is maintained at 1.5–2.0, where energy transfer efficiency is highest. However, in ARDS, hypoxic pulmonary vasoconstriction, hypercapnia, microthrombosis, vascular remodeling, and high transpulmonary pressure from mechanical ventilation jointly cause Ea to rise sharply. Facing increased afterload, the RV initiates compensatory mechanisms. Early adaptation manifests as “isometric regulation” (increasing contractility to counter afterload without chamber enlargement—ideal compensation). When contractile reserve is exhausted, the RV shifts to “isotonic regulation” (Frank-Starling mechanism), maintaining stroke volume via chamber dilation—the typical early manifestation of right heart injury. Once the Ees/Ea ratio further drops (usually <0.8), severe RV dilation fails to maintain output, entering a “decoupling” state, leading to severe hypoperfusion and venous congestion. Additionally, RV coronary perfusion primarily occurs during diastole; extreme RV pressure elevation increases RV wall tension and prolongs systole, potentially causing subendocardial ischemia, further worsening contractility and forming a vicious cycle.

Theoretically, V-V ECMO corrects blood gas abnormalities to lower pulmonary vascular resistance (PVR). However, the consensus specifically notes that right heart injury may persist or worsen during ECMO. This mainly stems from inappropriate mechanical ventilation settings during ECMO operation: low positive end-expiratory pressure (PEEP) may exacerbate atelectasis and hypoxic vasoconstriction, while high PEEP may cause alveolar overdistension compressing extrapulmonary vessels, causing PVR to rise in a “U-shaped curve.” Furthermore, persistent inflammatory storms, microvascular thrombosis, and severe RV dilation causing ventricular interdependence (septal leftward shift restricting LV filling) constitute the complex pathological landscape of progressive right heart injury during ECMO.

3. Severity Classification of Right Heart Injury

A major innovation of this consensus is abandoning the binary “yes/no” classification of right heart injury, introducing a severity classification system based on “flow-demand matching.” The core criterion is not heart size, but whether the RV can maintain cardiac output meeting metabolic demands.

Under this framework, right heart injury is classified into three clinical subtypes:

(1) Mild Right Heart Injury (RV Dilation): Manifests as isolated RV dilation [right ventricular end-diastolic area (RVEDA)/left ventricular end-diastolic area (LVEDA) > 0.6], but hemodynamically stable, no vasopressors needed, meets flow demand without obvious organ congestion, corresponding to the “isotonic regulation” compensatory phase.

(2) Moderate Right Heart Injury (Right Heart Insufficiency): On top of dilation, RV contractile function is impaired. Although patients may rely on vasopressors to maintain circulation, overall flow demand is still met, at the edge of compensation. VExUS grade 1–2, urine output may slightly decrease.

(3) Severe Right Heart Injury (Right Heart Failure): Manifestation of RV decompensation, with significant RV dilation and severe contractile impairment, unable to meet flow demand. Clinically presents with shock, progressive lactate elevation, oliguria, or altered consciousness; severe organ congestion (VExUS grade 3).

This physiology-based classification directly guides treatment strategy escalation: mild-to-moderate injury focuses on load optimization and pharmacological support; severe injury requires mechanical circulatory support escalation.

4. Stepwise Management Strategy for Right Heart Injury

For right heart injury during V-V ECMO, the consensus proposes a stepwise comprehensive management plan covering ECMO settings, mechanical ventilation, pharmacotherapy, and mechanical assistance. The therapeutic goal is not merely maintaining systemic oxygenation but breaking the vicious cycle of “RV dilation → restricted LV filling → hypoperfusion → acidosis → elevated PVR.” Management follows the three-dimensional principle of “reduce afterload, optimize preload, enhance contractility.”

(1) V-V ECMO Settings

For newly diagnosed right heart injury, the consensus recommends targeting SaO₂ > 90% and PaCO₂ < 45 mmHg (referencing the EOLIA trial) to eliminate hypoxia and acidosis-induced pulmonary vasoconstriction. Increasing ECMO flow to raise SvO₂/PvO₂ systematically reduces cardiac output, PAP, and RV work without worsening intrapulmonary V/Q matching. Reduce V-V ECMO recirculation; high recirculation (>30%) means large volumes of oxygenated blood circulate ineffectively, with hypoxic blood still flowing in the RV and pulmonary artery, preventing PVR reduction. Crucially, brain protection must be emphasized: in the initial 24 h of ECMO, avoid PaCO₂ relative drops exceeding 50%. Regarding V-V ECMO fluid management, actively pursue negative fluid balance while ensuring minimum effective ECMO flow (avoiding cannula “suction/jumping” phenomena).

(2) Mechanical Ventilation Strategy

Core goal: reduce RV afterload. Target low driving pressure to minimize alveolar overdistension compressing pulmonary capillaries. PEEP setting is a trade-off: too high increases intrathoracic pressure, hindering venous return and increasing PVR; too low causes atelectasis, triggering hypoxic pulmonary vasoconstriction. Finding the “optimal PEEP” (best lung compliance, lowest PVR) is the essence of RV-protective ventilation. Regarding prone positioning, despite lacking RCT evidence for survival benefit, physiologically it improves V/Q matching and lowers PVR, significantly unloading the RV, and is thus considered a reasonable pathophysiological treatment by the consensus.

(3) Pharmacotherapy

When optimizing ventilation and ECMO settings fails to improve right heart injury, pharmacotherapy becomes the second line. The consensus supports dobutamine or milrinone as inotropes; the latter combines inotropic and vasodilatory effects, making it ideal for improving RV-PA coupling, but systemic hypotension must be guarded against. Maintaining systemic mean arterial pressure (MAP) is crucial for RV coronary perfusion; thus, norepinephrine is often combined. Inhaled nitric oxide (iNO) or epoprostenol, selectively dilating well-ventilated alveolar vessels, lowering RV afterload without systemic hypotension, are also recommended to improve pulmonary hemodynamics.

(4) Stepwise Mechanical Assistance

For severe right heart injury unresponsive to all above measures, presenting refractory shock (low MAP, high lactate, SvO₂ < 50%), mechanical circulatory support escalation is mandatory. V-V ECMO alone is insufficient; conversion to V-P (venous–pulmonary artery) ECMO or V-V-A (veno-veno-arterial) ECMO is required. V-P ECMO uses a dual-lumen cannula to pump oxygenated blood directly into the pulmonary artery, essentially acting as an oxygenator-equipped right ventricular assist device (RVAD), suitable for isolated RV failure. V-V-A ECMO adds arterial return to the V-V circuit, providing simultaneous gas exchange and systemic perfusion support, suitable for mixed failure with LV dysfunction or extreme low cardiac output. Timely transition from V-V to V-P or V-V-A mode is the last line of defense for saving severe right heart injury patients.

5. Conclusion

The release of the Expert Consensus on Right Heart Injury in V-V ECMO Patients marks the transition of V-V ECMO right heart injury management from empirical medicine to physiology-based precision medicine. By implementing the “definition–classification–stepwise management” strategy, adjusting ventilator parameters, ECMO settings, and drug choices to restore RV-PA coupling, and decisively escalating mechanical support when necessary, the vicious cycle of RV failure can be broken, improving prognosis for this high-risk population.

(Long Yun, Xue Yuechuan; Peking Union Medical College Hospital)

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