Discussion
Our retrospective analysis, comparing simultaneous mechanical support with ECMO+Impella® versus single ECMO therapy in eCPR patients, showed improved overall-survival after concomitant Impella® support. From the data presented, Impella® assist was associated with a higher weaning rate of ECMO support. The association of lower mortality and a higher rate of successful ECMO weaning was consistent through all investigated subgroups, including a comparison of only male patients. On the other hand, complications, including AKI with subsequent hemodialysis, were more frequently seen in the ECMO+Impella® group.
ECMO-therapy establishes an artificial cardiopulmonary bypass in severely impaired hemodynamic situations, such as ongoing CPR, and provides adequate oxygenation for vital organs (16). Besides, ECMO therapy is associated with various complications of inadequate treatment, especially the increased afterload, which might negatively impact the outcome (17).
In this retrospective analysis, we observed a significant reduction in in-hospital mortality in the ECMO+Impella® cohort, alongside a significantly higher rate of successful ECMO weaning in the ECMO+Impella® cohort. These findings are supported by a recent large multicenter cohort study by Schraege and colleagues, who analyzed data from 686 cardiogenic shock patients treated with VA-ECMO with or without left ventricular unloading by concomitant Impella® implantation (11). In their observational analysis, simultaneous Impella® implantation was associated with significantly lower mortality in cardiogenic shock and eCPR patients and more complications, such as bleeding, ischemia, and renal replacement therapy. Another broad analysis by Pappalardo et al. showed similar results, describing increased AKI rates with hemodialysis (18).
The increased survival rates observed in our cohort might be explained by the potential benefits of LV-unloading in eCPR patients. Previously, early LV-unloading has been reported to be beneficial in cardiogenic shock patients treated with ECMO via the reduction in preload (17, 19).
Other mechanical support devices might also improve mortality and outcome. An intraaortic balloon pump might also be beneficial concomitant to VA-ECMO therapy in eCPR patients due to its counter pulsatile fashion (20).
On the other hand, other authors and centers advocate a conservative strategy regarding additional Impella® implantation in VA-ECMO therapy (9, 10). Today, there is no universally used unloading strategy; thus, LV-venting in VA-ECMO patients remains to be the target of ongoing scientific research. Randomized trials are necessary to confirm the reduction in mortality going along with LV unloading and determining a certainty, strategy-wise, for eCPR patients.
Safety of concomitant Impella ®-placement
In our retrospective analysis, complications such as AKI and the need for blood-transfusions occurred more frequently in the ECMO+Impella® group. This was consistent in evaluated subgroup analysis and was associated with Impella®-therapy in linear regression analysis.
A higher rate of active bleeding or limb ischemia could not be observed.
This confers to larger evaluations, such as Schraege et al., who observed a higher rate of complications such as bleeding, ischemia, and AKI in patients treated with additional Impella® implantation (11).
In regard to an increase of shear stress, hemolysis is a known complication associated with Impella® and is associated with an increased need for blood-transfusions (21). As well as limb ischemia due to large vascular access requirements of Impella® support.
In this analysis, we found a significantly higher proportion of AKI with the need for hemodialysis in the ECMO+Impella® group, which was significantly associated with the use of additional Impella® implantation. ECMO therapy is a known risk factor for renal failure (22-24). Moreover, it is thought to lead to a reduction in renal oxygen delivery and inflammatory damage. In particular, during pathological conditions requiring ECMO, biological defense mechanisms maintaining central perfusion by reducing perfusion of peripheral organs (such as the kidney) have been identified. However, the role of additional Impella® implantation on acute kidney failure remains unclear and clinical data is scarce (25-27).
In summary, complications like the higher need for renal replacement therapy, bleeding, and limb ischemia might be explained by more increased survival. Thus, patients are more exposed to the risk of suffering complications.