Discussion
ECMO technology, patient selection and its implementation has improved
dramatically since the early studies. This has occurred due to better
circuits, improved oxygenator technology, more experienced teams, and
more informed decision-making regarding timing of implementation. This
increase in the deployment of ECMO is evident in ELSO reporting, with
studies increasing regarding factors impacting survival in different
subsets of ECMO populations.
Interestingly, our data has shown no correlation between survival, and
several factors that had previously been thought to contribute to
mortality; the type of operation, operative times (including cross-clamp
and cardiopulmonary bypass times), open chest status, reoperation for
bleeding, the presence of frozen mediastinum and the timing of
cannulation. Our data has shown that patients who are centrally
cannulated may have a trend toward ability to wean from ECMO, with a
non-significant trend toward short and long-term survival as well. One
possible consideration may be more efficient venous drainage and cardiac
offloading via central cannulation, as the timing of cannulation was not
a key factor in survival based on our analysis.
One critique of the study could be the inclusion of VV patients with a
VA ECMO cohort. We included these patients as they represented severe
organ impairment in the postoperative period, and the majority of these
patients were supported with RVAD with in-line oxygenator representing
RV failure, a known indicator of mortality in postcardiotomy
patients[7]. Though a small sample size, no
statistical significance was noted between groups. Of note, analysis was
also conducted for every comparison with and without the VV cohort
included and there were no noted statistically significant differences
in the data at short or long-term follow-up.
The use of ECMO in the post-cardiotomy population has been reported to
have high morbidity and mortality with ability to wean from ECMO
<50% and hospital survival ranging between 25-40%, and
minimal data on long-term outcomes available. Our experience has
demonstrated that PC-ECMO utilization may be associated with a
reasonable rate of long-term survival. Overall survival data in our
PC-ECMO group was: 61% were weaned, 55% survived hospitalization, and
45% were alive one month after discharge. This compares favorably to
data from the ELSO registry (59% weaned, 43% discharged), and
superiorly to ECPR support (41% weaned, 29% discharged).
This data also offers a glimpse into long-term survival for PC-ECMO
patients. At 12 months, 40% of PC-ECMO patients were still alive, and
at almost 3 years after discharge, 33% of patients were still alive.
The estimated 12 month survival for patients surviving their index
hospitalization was 66%, and survival was 60% at both 24 and 36
months, indicating a reasonable prognosis for long-term survival if
patients reach hospital discharge. For reference, in renal failure
patients receiving hemodialysis, the median survival at 3 years is
approximately 57%[8-9]. Data exists for many
chronic medical processes with five-year survival rates to use as a
comparison (Figure 8). Heart failure, gastric and esophageal cancer,
lung cancer and pancreatic carcinoma all have median survival at 5 years
<30%[10]. More specifically, localized
pancreatic adenocarcinoma carries a median 5-year survival of 34%,
which is comparable to the overall survival of our PC-ECMO cohort[10]. Certainly, medical and surgical oncologists
may advocate for the surgical resection of localized pancreatic
adenocarcinoma, provided that the patient is otherwise an appropriate
surgical candidate[11].
More robust data is needed to determine predictors for quality of life
following PC-ECMO, which may yield improved decision-making strategies
for ECMO implementation based on these individual patient
characteristics, allowing physicians to predict which patients stand to
benefit the most from ECMO cannulation from a quality of life
standpoint.
In closing, our results demonstrate that PC-ECMO is a reasonable
strategy to salvage patients who experience refractory post-cardiotomy
cardiogenic shock, and has a 1-year and 3-year survival comparable to
other surgically-treated diseases. Further data is needed to help
characterize which patients may benefit most from ECMO implementation,
but our experience has shown that post-cardiotomy ECMO support is no
longer a bridge to nowhere.