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.