A . Calhoun et al .: J Extra Corpor Technol 2025 , 57 , 24 – 31 25
variability to this process due to varying experience with individual technologies . In addition to physiologic differences in the mechanical methods of LV unloading , placement techniques for these strategies vary significantly . For example , atrial septostomy requires expertise in structural heart interventions while intra-aortic balloon pump counter pulsation and percutaneous transvalvular micro-axial pump placement require a separate skill set . While some studies suggest an association between improved hospital mortality with mechanical LV unloading during VA-ECMO , long-term outcomes are less clear [ 7 ]. One small study of cardiogenic shock patients suggested an association with improved 90-day survival in those supported by VA-ECMO ( not due to myocardial infarctionrelated shock ) undergoing concomitant IABP [ 13 ]. For example , a recent study from the United Network for Organ Sharing ( UNOS ) on patients proceeding to transplant did not suggest a difference in survival in VA-ECMO patients undergoing LV mechanical unloading versus those supported by VA-ECMO without it [ 14 ].
LVD is important for patients with cardiogenic shock as it may negatively impact cardiac recovery . Early recognition and management may improve outcomes . LVD may occur upon ( or even prior to ) initiation of VA-ECMO support and methods of detection are based on clinical , hemodynamic , or imaging information . Depending on institutional preferences , pulmonary artery catheter ( PAC ) hemodynamics , echocardiographic ( ECHO ) evaluation , arterial line pulse pressure ( ALPP ) assessment , and the presence of pulmonary congestion on chest radiography have been suggested as assessment tools for the detection of LV distention and its sequelae [ 1 , 2 , 5 , 6 ].
Clinical trials , review articles and editorials have described multiple indications for the use of LV unloading and display significant heterogeneity in triggers for the initiation of this maneuver [ 15 ]. A recent survey of Italian medical centers showed significant practice variation in both monitoring and treatment modalities for LV unloading in patients supported by VA-ECMO [ 16 ]. Additionally , certain clinical trials were designed to initiate mechanical LV unloading at the time of VA-ECMO initiation for cardiogenic shock [ 8 ]( See Table 1 ). This variability makes research more challenging to interpret and increases the complexity of clinical decision-making .
Not all LV unloading strategies are equivalent . As the clinician increases the level of invasiveness in unloading , risks , and negative sequelae increase for the patient . The lack of uniformity in the literature makes the indications of care escalation unclear as well . Additionally , in cases where the AV is not opening due to acute hypovolemia , invasive methods of LV unloading are not only unwarranted but will likely be ineffective . This literature search serves to call attention to further investigation to answer the question of when and how to unload the LV in the setting of VA-ECMO .
Methods
A PubMed search was performed using the phrase “ LEFT VENTRICULAR UNLOADING ECMO ” to retrieve all research , review , and editorial articles that resulted under this search term . The articles were reviewed for suggested criteria to diagnose LVD and thresholds for LV mechanical unloading .
Articles were separated by type ( for example , research ( randomized or otherwise ), guidelines , review , and editorial ). In this literature search , we identified both qualitative and quantitative criteria that were clinical ( and radiological ), hemodynamic , and echocardiographic in nature . Articles were excluded from this review if they did not describe criteria for LVD or thresholds for mechanical LV unloading . For example , articles that described outcomes associated with LV mechanical unloading but did not describe thresholds were not included in this review .
Summary of literature search
Significant heterogeneity was noted in definitions of LVD and triggers for the initiation of LV mechanical unloading . We found that significant variability in the diagnosis and treatment of LVD during VA-ECMO exists , which is consistent with a recent countrywide survey of Italian centers [ 16 ].
Three randomized trials either examine the effect of mechanical unloading or contain a threshold for its initiation [ 8 , 9 , 17 ]. Of these three , two studies examine the effects of transseptal cannulation for left atrial drainage to mechanically unload the LV , both of which did not find an impact on survival [ 8 , 9 ]. The main drawbacks of these studies were their small size and use of a relatively uncommon , and indirect method of LV unloading ( specifically , left atrial drainage that reduces LV preload as opposed to direct LV unloading ) [ 8 , 9 ]. Additionally , these studies did not utilize hemodynamic criteria to trigger LV unloading in either arm . In the third randomized trial which examined the use of VA-ECMO for shock due to acute myocardial infarction , the main drawbacks with regard to LV unloading were the lack of hemodynamic criteria ( rather , pulsatility and echocardiography were utilized ) as well as the low overall incidence of its use ( 5.8 % in the early VA-ECMO arm ) [ 17 ].
Results are found in Table 1 . A total of 31 of 248 articles ( 12.5 %) were found to contain suggested criteria for LVD and indications for mechanical unloading . Publication dates ranged from 2013 to 2023 [ 1 – 3 , 8 – 10 , 12 , 17 – 39 ]. There were ten review articles , ten retrospective reviews five case series , three randomized trials , two guideline documents , and one editorial article . All but five articles contained clinical criteria for LVD or unloading with twenty-five describing chest radiograph evidence of pulmonary edema , and seven describing refractory ventricular arrhythmias . All but seven contained hemodynamic definitions of LVD . Seventeen included criteria regarding ALPP monitoring , fourteen included pulmonary capillary wedge pressure ( PCWP ) elevations , eight included elevated PAC pressures ( such as pulmonary artery diastolic pressure ), and three included central venous pressure ( CVP ) elevations . Finally , echocardiographic signs of LVD were described in all but two articles . A total of twenty articles describe smoke , echo contrast , or signs of significant stasis ; seventeen articles used reduced or loss of AV opening ; fifteen studies included LV size criteria , five discussed visual evidence of reduced LV contractility ; three describe left ventricular outflow tract ( LVOT ) velocity time integral ( VTI ) criteria ; another three describe clot in the aortic root or left ventricle ; another three describe inferior vena cava diameter ; and other , less frequent criteria such as significant aortic insufficiency or lung