Discussion
Cardiogenic shock is a serious and often lethal manifestation following
cardiac insult with extremely high rates of in-hospital mortality.
Historical rates have been reported as high as 80%15.
However, more contemporary trials such as the SHould we emergently
revascularize Occluded Coronaries for cardiogenic shock (SHOCK) trial
and Global Registry of Acute Coronary Events (GRACE) registries have
reported rates around 60%16,17. Few reports have
achieved mortality rates below 50%18,19. Considerably
less data exists in the cardiac surgical population in patients with
cardiogenic shock. Existing literature is limited to smaller case series
and case reports. Herein, we report our experience of 604 procedures
performed on patients in cardiogenic shock.
Hemodynamic stabilization and bridging of the cardiogenic shock patient
population is highly debated. In our series, we utilized intravenous
inotropes most frequently (35.4%), followed by the use of intra-aortic
balloon pumps (33.4%). The effectiveness of intra-aortic balloon pump
in cardiogenic shock, especially in the setting of acute myocardial
infarction, has been argued. The IABP SHOCK II Trial has demonstrated no
mortality benefit of these pumps in addition to early
revascularization2. Early revascularization, however,
has been proven to offer early and long-term survival benefit in this
patient population20. Other methods of bridging such
as venoarteroal ECMO and/or Impella device were utilized infrequently in
our series, comprising less than 4% of our surgical experience. ECMO
bridge to cardiac surgery other than transplant or ventricular assist
device has been described in prior case series and reports. Common
indications were for mechanical complications of acute myocardial
infarction including ventricular septal defect or papillary muscle
rupture21–23. Long-term outcomes of hemodynamic
support with veno-arterial ECMO for cardiogenic shock have not been well
studied.
Timing of surgical intervention can be as important to patient outcomes
as the operation itself. No specific guidelines exist for the patient in
cardiogenic shock, and often, timing is individualized according to the
patient’s clinical status. In our opinion, the timing of operation in
these patients should be dictated by the disease process, baseline risk
of the patient including comorbidity assessment, as well end-organ
status. For example, a patient presenting in volume overload and
marginal hemodynamics with an acute-on-chronic valvular process may
benefit from intravenous diuresis, inotropic or temporary mechanical
circulatory support, and improvement in end-organ status before
commencing with surgery. Sometimes this is not possible such as in cases
of acute valve leaflet perforation from endocarditis where the heart is
not pre-conditioned to valvular insufficiency. These patients typically
require emergent operations. A similar balance exists in coronary
revascularization. Patients presenting with acute ST-elevation
myocardial infarctions with ongoing ischemia require emergent
revascularization, whether percutaneously or surgically. In a patient
presenting late from an acute myocardial infarction who is in
cardiogenic shock but has no ongoing signs of active ischemia,
stabilizing hemodynamics and optimizing the patient for a short time
period before revascularization may be appropriate in select cases.
The early mortality rates in our study were markedly lower than those
described in large cardiogenic shock trials and likely a result of
selection bias when deciding operative candidacy. Patients with higher
comorbidity burden and perceived prohibitive surgical risk were likely
turned down and not captured in this study, while previous trials
investigating cardiogenic shock included all shock patients, both
surgical and non-surgical candidates16,17. When
evaluating cardiogenic shock patients for surgical intervention, we have
identified several risk factors independently associated with increased
hazards for mortality. This include advanced age, peripheral vascular
disease, and renal failure requiring dialysis, all risk factors
associated with increased morbidity and mortality in the non-shock
population following cardiac surgery24–26. Careful
patient selection for surgical intervention may help reduce short-term
mortality and avoidance of futile procedures in non-salvageable
patients. As observed in our study, if these high-risk patients are able
to survive to hospital discharge, their longer-term outcomes are
favorable. Moreover, we observed overall 1- and 5 -year survival of
71.7% and 62.1%. Additionally, heart failure readmission occurred in
only 18.9% of our cohort with median readmissions per person of 0 (IQR
0-2 readmissions), and less than 1% of surviving patients required
advanced heart failure surgical therapy. Such findings support efforts
to perform cardiac surgical procedures in appropriately selected
patients presenting with cardiogenic shock.
Each individual patient is different as is the approach that individual
surgeon’s and other providers may have with these patients. There are
certainly multiple factors which play into the decision-making process
regarding surgical candidacy. The general approach our surgical group
has is to attempt to assess the patient’s overall life expectancy should
they survive surgery, as well as the potential reversibility of the
anatomic or physiologic insults causing the shock state. For instance, a
90-year old presenting in cardiogenic shock on multiple vasoactive
agents with marginal urine output will likely have poor outcomes.
Similarly, a patient with significant comorbidity burden such as chronic
lung disease with home oxygen dependence, dialysis, and peripheral
arterial disease requiring extensive multi-component cardiac surgery may
have poor outcomes and limited life expectancy even if they survive
surgery.