Q31 / 110
During femoral VA-ECMO, right radial PaO₂ is 48 mmHg while femoral PaO₂ is 285 mmHg after native LV recovery but with poor lung gas exchange. What explains this?
Correct answer: B — Differential oxygenation from dual circulation
This is differential oxygenation from dual circulation: the recovering LV ejects poorly oxygenated blood proximally while femoral VA-ECMO delivers highly oxygenated blood retrograde distally. The right radial arterial line therefore better reflects cerebral oxygen delivery than the femoral sample. It may be worth discussing interventions at this point, including transitioning to VV, addition of a venous limb, and the impacts of circulation balance depending on the remaining physiology.
Board pearl: When differential oxygenation appears, discussion can extend to transitioning to VV or adding a venous limb depending on circulation balance.
This is differential oxygenation from dual circulation: the recovering LV ejects poorly oxygenated blood proximally while femoral VA-ECMO delivers highly oxygenated blood retrograde distally. The right radial arterial line therefore better reflects cerebral oxygen delivery than the femoral sample. It may be worth discussing interventions at this point, including transitioning to VV, addition of a venous limb, and the impacts of circulation balance depending on the remaining physiology.
Board pearl: When differential oxygenation appears, discussion can extend to transitioning to VV or adding a venous limb depending on circulation balance.
Q32 / 110
Which term is preferred over “Harlequin syndrome” for regional differences in arterial oxygen content during VA-ECMO?
Correct answer: B — Differential oxygenation
Differential oxygenation precisely describes the physiology without assuming a fixed mixing location. A describes a zone rather than the abnormality. C is common but anatomically imprecise. D is not recommended terminology.
Board pearl: Use differential oxygenation as the physiologically precise term.
Differential oxygenation precisely describes the physiology without assuming a fixed mixing location. A describes a zone rather than the abnormality. C is common but anatomically imprecise. D is not recommended terminology.
Board pearl: Use differential oxygenation as the physiologically precise term.
Q33 / 110
During femoral VA-ECMO, what primarily determines the location of the aortic mixing point?
Correct answer: B — Balance between native cardiac output and retrograde ECMO flow
During femoral VA-ECMO, the aortic mixing point is primarily determined by the balance between native cardiac output and retrograde ECMO flow. Questions 31-33 revolve around the Badulak et al. position paper on the physiology and nomenclature of dual circulation during venoarterial ECMO in adults, which emphasizes that this mixing point is dynamic rather than fixed.
Board pearl: Questions 31-33 revolve around the Badulak et al. position paper on dual circulation physiology and nomenclature.
During femoral VA-ECMO, the aortic mixing point is primarily determined by the balance between native cardiac output and retrograde ECMO flow. Questions 31-33 revolve around the Badulak et al. position paper on the physiology and nomenclature of dual circulation during venoarterial ECMO in adults, which emphasizes that this mixing point is dynamic rather than fixed.
Board pearl: Questions 31-33 revolve around the Badulak et al. position paper on dual circulation physiology and nomenclature.
Source(s): Badulak et al. Position paper on the physiology and nomenclature of dual circulation during venoarterial ECMO in adults. Intensive Care Med. 2024 Nov 18;50(12):1994-2004.
Q34 / 110
Which catheter-based modality provides the greatest direct LV unloading while reducing LV and aortic-root stasis?
Correct answer: C — Impella CP or 5.5
Impella CP or 5.5 provides the greatest direct LV unloading among the listed catheter-based modalities because it actively removes blood from the ventricle and reduces LV and aortic-root stasis. A quick discussion of the physiologic impact of increased PEEP on LV afterload reduction can be useful, but if that option is included it is still less direct than Impella. It is also reasonable to keep something like LA-VA ECMO in mind when discussing decompression strategies more broadly.
Board pearl: LA-VA ECMO is worth keeping in the discussion when comparing catheter-based unloading strategies, even though Impella remains the most direct transvalvular unloading option listed here.
Impella CP or 5.5 provides the greatest direct LV unloading among the listed catheter-based modalities because it actively removes blood from the ventricle and reduces LV and aortic-root stasis. A quick discussion of the physiologic impact of increased PEEP on LV afterload reduction can be useful, but if that option is included it is still less direct than Impella. It is also reasonable to keep something like LA-VA ECMO in mind when discussing decompression strategies more broadly.
Board pearl: LA-VA ECMO is worth keeping in the discussion when comparing catheter-based unloading strategies, even though Impella remains the most direct transvalvular unloading option listed here.
Source(s): Lemor et al. Left Atrial-Veno-Arterial Extracorporeal Membrane Oxygenation: Step-By-Step Procedure and Case Example. Structural Heart. 2022 Oct 6:100117.
Q35 / 110
Compared with VA-ECMO alone, observational ECPELLA evidence generally shows which tradeoff?
Correct answer: B — Lower mortality association but more bleeding and hemolysis
Compared with VA-ECMO alone, observational ECPELLA evidence generally shows a tradeoff of lower mortality association but more bleeding and hemolysis. See the Ezad et al. review (https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.062371) for the broader unloading literature and ongoing trials that frame this tradeoff. Additional device-related morbidity may also include vascular complications and greater need for renal replacement therapy.
Board pearl: ECPELLA tradeoffs should be interpreted within the broader unloading literature summarized in the Ezad et al. review (https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.062371).
Compared with VA-ECMO alone, observational ECPELLA evidence generally shows a tradeoff of lower mortality association but more bleeding and hemolysis. See the Ezad et al. review (https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.062371) for the broader unloading literature and ongoing trials that frame this tradeoff. Additional device-related morbidity may also include vascular complications and greater need for renal replacement therapy.
Board pearl: ECPELLA tradeoffs should be interpreted within the broader unloading literature summarized in the Ezad et al. review (https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.062371).
Source(s): Ezad et al. Unloading the Left Ventricle in Venoarterial ECMO: In Whom, When, and How? Circulation. 2023 Apr;147(16). https://doi.org/10.1161/CIRCULATIONAHA.122.062371.