Pre-reading
The following are key points to remember from this summary of the
Society for Cardiovascular Angiography and Interventions (SCAI) Clinical
Expert Consensus Statement on the Classification of Cardiogenic Shock
(CS). The document is endorsed by the American College of Cardiology,
American Heart Association, Society of Critical Care Medicine, and
Society of Thoracic Surgeons:
A system describing stages of CS from “A to E” is proposed. The
purpose of this proposed classification of CS is to enable clear
communication regarding patient status and to allow clinical trials to
appropriately differentiate CS patient subsets.
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Stage A:Patient who is“at risk”for CS but is not experiencing signs or symptoms of CS (e.g., someone
with non–ST-segment elevation myocardial infarction (NSTEMI). This
patient is warm and perfusing, and has normal cardiac index and no sign
of volume overload or hypoperfusion.
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Stage B: “beginning”shock or
compensated shock where a patient may be volume overloaded, tachycardic,
and/or hypotensive but no evidence of hypoperfusion on physical exam or
laboratory studies.
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Stage C is“classic”CS: Stage B patient with evidence of hypoperfusion on physical exam and laboratory studies “Cold and Wet.” Invasive hemodynamics (if available) demonstrate the classic depressed cardiac index associated with CS.
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Stage D is“deteriorating”:
Stage C plus failure of initial interventions in restoring adequate
perfusion in 30 minutes and further escalation is required. Escalation
is an increase in the number or intensity of intravenous therapies to
address hypoperfusion, or addition of mechanical circulatory support
after the initial 30-minute period of observation and treatment.
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Stage E is“extremis”:
Patient is highly unstable, often with circulatory collapse and/or
refractory cardiac arrest with ongoing cardiopulmonary resuscitation
(CPR). They are being supported by multiple simultaneous acute
interventions including extracorporeal membrane oxygenation
(ECMO)-facilitated CPR (eCPR).
Additionally, the(A)modifier for cardiac arrest is applied to describe those who suffer a
cardiac arrest irrespective of duration (treated with chest compressions
or direct current cardioversion). Accordingly, a patient may be in
stage BA shock, indicating stage B with a cardiac arrest
complicating the clinical picture (e.g., a patient who presents with
ventricular fibrillation in the setting of acute MI and rapidly
stabilizes with prompt defibrillation).
Other key points highlighted are:
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Troponin T is an independent
prognostic indicator of adverse outcomes and can be used as a patient
risk-stratifying tool. Elevation of troponin in CS may identify patients
who present late.
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Arterial lactate is preferable
since venous lactate is generally higher than arterial lactate and the
2.0 mmol/L cut-off is best established for arterial lactate.
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A low serum bicarbonate level is a better predictor of 30-day mortality than the highest recorded lactate level.
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A low B-type natriuretic peptide
(BNP) level argues against CS in the setting of hypotension; however, an
elevated BNP level does not establish the diagnosis, as any form of
cardiac ventricular or atrial stress may elevate levels of this peptide.
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It is recommended to use a
pulmonary artery catheter in the diagnosis and management of CS
patients, along with rapidly transferring those requiring a higher level
of care to an experienced shock center.
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Mixed shock patients have
features suggestive of systemic inflammation, with or without proven
infection. Such systemic vasodilation exacerbates systemic hypoperfusion
and decreases coronary perfusion pressure. The potential for mixed
shock emphasizes the importance of invasive hemodynamic monitoring.