Discussion
Our data showed that in patients affected by PCS following cardiac
surgery, the duration of VA-ECMO support is associated with increased
mortality. Patients weaned from VA-ECMO after 4 to 7 days had
significantly lower mortality compared with patients with shorter or
longer mechanical support, even when adjusted for confounding. In
addition, VA-ECMO support longer than 7 days was associated with a
significantly increased risk of complications, including re-exploration
for bleeding, blood transfusion, renal failure requiring renal
replacement therapy, deep sternal wound infection, bloodstream infection
and pneumonia.
Evidence from the Extracorporeal Life Support Organisation (ELSO)
registry also showed that short duration of VA-ECMO is associated with
high mortality. In this large registry that included 2699 VA-ECMO
patients, survival increased up to day 4 and then decreased from day 4
to 12, with no significant change thereafter [1]. However, the study
encompassed a mixed cohort of patients with only a minority of them
undergone cardiac surgery, a limitation shared with previous studies
[1-3,8,9]. On the other hand, the absence of clear guidelines on
VA-ECMO weaning is the testament that this aspect is still poorly
addressed [1-3]. In addition, data on survival with longer VA-ECMO
runs are limited [1,3,4,9]. To our knowledge, the present analysis
is the largest to date in evaluating the impact of VA-ECMO duration in
adult patients affected by PCS following cardiac surgery. Distelmaier et
al. [4] firstly addressed the impact of VA-ECMO duration on survival
in 354 cardiovascular surgery patients, observing that longer VA-ECMO
runs were associated with higher mortality even 2-years after hospital
discharge [4]. More recently, Wang et al. [3] enrolled 166 PCS
patients following coronary bypass surgery. More than 60% of patients
received VA-ECMO for 3–6 days and had significantly lower mortality
than those who were supported by VA-ECMO for < 3 days or
≥ 7 days [3].
Our data are consonant with previous studies, suggesting that in PCS
patients following cardiac surgery VA-ECMO support longer than 7 days
can be challenged, considering the associated early and late higher
mortality. In this cohort of patients, the risks of complications appear
to overcome the cardiopulmonary advantage exerted by the VA-ECMO
support. Bloodstream infections have been demonstrated to be associated
with longer VA-ECMO runs, occurring in 27.7% of treated patients
[11,12]. Therefore, it is not surprising that longer VA-ECMO runs
are associated with a higher risk of bloodstream infection along with an
increased rate of blood transfusions and organ failure [11,12].
Among other complications, administration of large volumes of blood
transfusion and renal failure requiring renal replacement therapy are
potentially fatal conditions in longer VA-ECMO runs, particularly in PCS
patients with an underlying severe cardiac dysfunction [13,14].
Similarly, our data confirmed that shorter VA-ECMO runs (≤3 days) are
also associated with significantly higher mortality. Although we did not
detect a higher rate of lethal haemorrhage in this patient group that
has been previously suggested as main cause of the increased early
mortality [15,16], the underlying primary cardiac condition seemed
to play a major role in the survival of those patients [3,17].
Cardiopulmonary failure leading to multiorgan failure appeared to
predominate over ECMO treatment. The hyperlactatemia observed in
patients under VA-ECMO ≤3 days suggest a significant metabolic
derangement in these patients. In this context, arterial lactate level
may be useful in guiding the appropriate timing of VA-ECMO
discontinuation, thereby avoiding futile prolonged support [19].
The results observed in our series are relevant considering the unsolved
issue of balancing a fruitful VA-ECMO duration against a vain support
especially in light of the uniquely high level of resources involved
[19]. In addition, due to the lack of defined guidelines and
indications, the duration of ECMO support is often based on arbitrary
limits [1]. Data derived from ELSO registry over a 10-year period
indicates that 52% of patients on VA-ECMO are discontinued from support
because of irreversible organ failure [1]. Therefore, when
cardiopulmonary recovery cannot be successfully achieved within 7 days,
other therapeutic options should be considered, including ventricular
assist device implantation or heart transplantation [1,7,19].
Certainly, our study is not exempted from limitations. First, our series
is subjected to the limitations of all observational analyses, including
selection bias and unmeasured confounding. Second, the present analysis
is conditional to in-hospital survival only, and our data do not allow
an assessment of the outcomes after weaning and discharge from the
hospital. Third, a trend in the survival of patients with very long ECMO
duration (> 15 days) may not be fully detected due to the
small number of remaining individuals, with insufficient statistical
power. Lastly, we cannot account for the surgeon and anaesthetist’s
experience as well as for the differences in local policies of ECMO
weaning. Despite these limitations, our cohort is currently the largest
in evaluating the impact of VA-ECMO duration in the PCS setting.
In conclusion, in PCS following cardiac surgery, patients weaned from
VA-ECMO after 4 to 7 days of support had significantly lower mortality
compared with those with shorter or longer mechanical support. The
present data can contribute to identifying the most ideal duration of
VA-ECMO support, supporting clinicians in deriving more accurate
prognostic models and timely weaning strategies.