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Unloading the left ventricle in venoarterial extracorporeal life support: The urgent need of speaking the same language!

  • Paolo Meani
    Affiliations
    Cardio-Thoracic Surgery Department, ECLS Centrum, Heart & Vascular Centre, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands
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  • Mariusz Kowalewski
    Affiliations
    Cardio-Thoracic Surgery Department, ECLS Centrum, Heart & Vascular Centre, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands

    Clinical Department of Cardiac Surgery, Central Clinical Hospital of the Ministry of Interior in Warsaw, Warsaw, Poland
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  • Giuseppe Maria Raffa
    Affiliations
    Cardio-Thoracic Surgery Department, ECLS Centrum, Heart & Vascular Centre, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands

    Department for the Treatment and Study of Cardiothoracic Diseases and Cardiothoracic Transplantation, ISMETT-IRCCS, Palermo, Italy
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  • Roberto Lorusso
    Affiliations
    Cardio-Thoracic Surgery Department, ECLS Centrum, Heart & Vascular Centre, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands

    Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands
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Open AccessPublished:May 14, 2022DOI:https://doi.org/10.1016/j.xjon.2022.04.042
      To the Editor:
      The authors reported no conflicts of interest.
      The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
      We have read the review article entitled “Controversies in ECMO: Immediate versus Watchful Waiting for VA-ECMO Venting” by Cavayas and colleagues,
      • Cavayas Y.A.
      • Noly P.-E.
      • Singh G.
      • Lamarche Y.
      Controversies in extracorporeal membrane oxygenation: immediate versus watchful waiting for venoarterial extracorporeal membrane oxygenation venting.
      published in the Special Issue of Invited Presentations: Adult: Mechanical Circulatory Support: Invited Expert Opinions of JTCVS Open December 2021. We congratulate the authors for this nice review article and, at the same time, provide some personal comments.
      The authors described the pathophysiology of left ventricle (LV) overload and correctly underlined the role of the preload in this complex mechanism. LV preload has been often underestimated as an important determinant of LV distension during venoarterial (VA) extracorporeal life support (ECLS). Indeed, the patient's venous return usually exceeds the ECLS drainage and subsequently passes through the pulmonary circulation. As a consequence, the residual transpulmonary blood flow and bronchial venous return may not be counterbalanced by the reduced LV ejection due to impaired contractility and retrograde ECLS-generated blood flow toward the aortic valve, leading to LV dilation and pulmonary congestion.
      • Bavaria J.E.
      • Ratcliffe M.B.
      • Gupta K.B.
      • Wenger R.K.
      • Bogen D.K.
      • Edmunds Jr., L.H.
      Changes in left ventricular systolic wall stress during biventricular circulatory assistance.
      A meticulous fluid–balance management should be strongly recommended. Continuous renal-replacement therapy may be adopted to avoid fluid overload when diuretics resistance occurs.
      • Ostermann M.
      • Connor Jr., M.
      • Kashani K.
      Continuous renal replacement therapy during extracorporeal membrane oxygenation: why, when and how?.
      Furthermore, the authors highlighted the urgent need of a common LV overload definition during VA ECLS and clearly stated its absence in the literature. On one hand, we strongly believe this gap should be immediately solved to better analyze and elucidate the ongoing research on this topic. On the other hand, a common LV overload definition has been already provided. Among 184 peripheral VA ECLS retrospectively investigated at the Maastricht University Medical Center, we developed a multiparametric approach to appropriately detect and monitor the LV-related hemodynamics and potential overload appearance during VA ECLS.
      • Meani P.
      • Delnoij T.
      • Raffa G.M.
      • Morici N.
      • Viola G.
      • Sacco A.
      • et al.
      Protracted aortic valve closure during peripheral veno-arterial extracorporeal life support: is intra-aortic balloon pump an effective solution?.
      First of all, this definition considered direct and undirect parameters, which should be always assessed in relationship with the others. None of them is sufficient for diagnosing the LV overload.
      Echocardiography plays a central role. This evaluation should quickly achieve an anatomical/functional overview of the heart. Besides the dimensions, volumes, and LV ejection fraction, the echocardiogram must include the aortic valve inspection. Protracted closure or incomplete valve opening are the most important markers of LV overload. As a consequence, the LV might be not able to eject, exceeding the aortic pressure caused by VA ECLS flow.
      • Travis A.R.
      • Giridharan G.A.
      • Pantalos G.M.
      • Dowling R.D.
      • Prabhu S.D.
      • Slaughter M.S.
      • et al.
      Vascular pulsatility in patients with a pulsatile or continuous flow ventricular assist device.
      Therefore, this may lead to dangerous blood stasis at the aortic root and LV cavity, potentially predisposing to cavity thrombosis,
      • Moubarak G.
      • Weiss N.
      • Leprince P.
      • Luyt C.E.
      Massive intraventricular thrombus complicating extracorporeal membrane oxygenation support.
      which can be “announced” by an increased “smoke-like” effect in the heart chambers or proximal aortic tract.
      In addition, there are several echocardiographic semiquantitative or quantitative parameters that might be applied to better define the grade of LV impairment. Among them, the velocity time integral at the LV outflow tract is certainly one of the most commonly used. Ten centimeters should be proposed as the lowest cut-off,
      • Aissaoui N.
      • Luyt C.E.
      • Leprince P.
      • Trouillet J.L.
      • Léger P.
      • Pavie A.
      • et al.
      Predictors of successful extracorporeal membrane oxygenation (ECMO) weaning after assistance for refractory cardiogenic shock.
      even if we suggest evaluating its trend over time.
      Table 1
      • Whitson M.R.
      • Mayo P.H.
      Ultrasonography in the emergency department.
      ,
      • Ravin C.E.
      Radiographic analysis of pulmonary vascular distribution: a review.
      shows the updated definition of LV overload that has been improved with new parameters and divided in 2 clinical scenarios based on VA ECLS implementation. Some parameters have been reserved to the preimplementation scenario. Central venous pressure and oxygen saturation, as well as the echocardiographic inferior vena cava evaluation, cannot be properly evaluated during full VA ECLS support, as a consequence of the venous cannula position. These parameters should be considered before ECLS, as marker of advanced fluid overload and severe myocardial disjunction. Likewise, the postcapillary wedge pressure should also be more useful either before ECLS placement or in the weaning phase.
      Table 1Definition of left ventricle overload
      MethodGrade of severity
      MildModerateSevere
      Pre-ECLS implementation
       Central venous line
      ScvO2, %75-5555-45<45
      CVP, mm Hg8-1212-16>20
       Echocardiogram
      AoR or MRMildModerateSevere
      LV distensionMildModerateSevere
      LA distensionMildModerateSevere
      “Smoke-like” effectMildModerateSevere
      IVC dilatation, cm
      IVC diameter in inspiration (Whitson and Mayo8).
      1.5-2.5>2.5>2.5
      IVC collapse
      IVC collapse in expiration (Whitson and Mayo8).
      <50%<50%No change
      VTI LVOT13-178-12≤7
      E/E′>15 (increased LV filling pressure)
       Swan-Ganz Catheter (Edwards LifeSciences)
      PCWP, mm Hg13-1818-25>25
      During ECLS
       Arterial line
      Arterial pulsatilityMild reduction (10-15 mm Hg)Moderate reduction (8-10 mm Hg)Almost (<8 mm Hg) or pulseless
       Echocardiogram
      AVOpening every 2 bpmOpening every 3-4 bpmClosure
      LV distensionMildModerateSevere
      LA distensionMildModerateSevere
      “Smoke-like” effectMildModerateSevere
      VTI13-178-12≤7
       Chest radiograph
      Congestion
      Classification according to Ravin.9
      Alveolar edemaInterstitial edemaRedistribution
      ECLS, Extracorporeal life support; ScvO2, central venous blood oxygen saturation; CVP, central venous pressure; AoR, aortic regurgitation; MR, mitral regurgitation; LV, left ventricle; LA, left atria; IVC, inferior vena cava; VTI, velocity time integral; LVOT, left ventricle outflow tract; E/E′, early diastolic velocity of mitral annular motion/early diastolic velocity of mitral inflow; PCWP, postcapillary wedge pressure; AV, aortic valve; bpm, beats per minute.
      IVC diameter in inspiration (Whitson and Mayo
      • Whitson M.R.
      • Mayo P.H.
      Ultrasonography in the emergency department.
      ).
      IVC collapse in expiration (Whitson and Mayo
      • Whitson M.R.
      • Mayo P.H.
      Ultrasonography in the emergency department.
      ).
      Classification according to Ravin.
      • Ravin C.E.
      Radiographic analysis of pulmonary vascular distribution: a review.
      Cavayas and colleagues
      • Cavayas Y.A.
      • Noly P.-E.
      • Singh G.
      • Lamarche Y.
      Controversies in extracorporeal membrane oxygenation: immediate versus watchful waiting for venoarterial extracorporeal membrane oxygenation venting.
      further declared that the LV can often be “medically” unloaded. Nevertheless, this statement might lead to underestimation of the current issue. In fact, in a cardiogenic shock animal model, we performed a full monitoring of the LV hemodynamic and workload.
      • Meani P.
      • Mlcek M.
      • Kowalewski M.
      • Raffa G.M.
      • Popkova M.
      • Pilato M.
      • et al.
      Transaortic or pulmonary artery drainage for left ventricular unloading in venoarterial extracorporeal life support: a porcine cardiogenic shock model.
      Although the relevant clinical parameters did not show any signs of LV overload or end-organ perfusion impairment, the pressure–volume analysis revealed increased LV filling pressure and diastolic volume, as well as raised myocardial oxygen consumption, as confirmed by other investigators.
      • Burkhoff D.
      • Sayer G.
      • Doshi D.
      • Uriel N.
      Hemodynamics of mechanical circulatory support.
      ,
      • Donker D.W.
      • Brodie D.
      • Henriques J.P.S.
      • Broomé M.
      Left ventricular unloading during veno-arterial ECMO: a simulation study.
      Overall, we thank the authors for the opportunity to highlight some urgent needs in the LV management during VA ECLS. First, the absence of a shared definition of LV overload does not allow one neither to act consistently nor to compare the outcomes recorded in different centers. Second, the effectiveness of each venting strategy cannot be properly judged due to the lack of consensus and standard LV monitoring under VA ECLS. Furthermore, until well-designed and performed randomized trials are performed, it will be extremely difficult to consider beneficial or detrimental any strategy in this respect based on the large amount of confounding negative factors present in a patient undergoing VA ECLS. Therefore, imputing the actual impact or influence of LV unloading procedure on the ultimate patient outcome will be very difficult.
      All these topics, in particular the elaboration of a common indication for unloading the LV, should be a priority for our scientific organization.

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