Cardiogenic Shock Classification System

Advances within the treatment of acute myocardial infarction (AMI) over the past five many years, including immediate percutaneous coronary intervention, have proven to dramatically improve outcomes. Patients with AMI may develop cardiogenic shock (CS) before or after coronary reperfusion. CS in association with AMI is related to a 40% to 50% overall 30-day mortality rate, which, despite advances, has not modified over the past 20 years. In May 2019, the Society for Cardiovascular Angiography and Interventions (SCAI) published a clinical expert statement on the classification of cardiogenic shock.

According to the National Cardiovascular Data Registry, CS means systolic blood pressure (SBP) ≤ 90 mm Hg and cardiac index < 2.2 l/min/m² and/or the necessity for parenteral inotropic or vasopressor therapy to take care of systolic blood pressure and cardiac index above these levels as a result of myocardial failure (Baran et al., 2019). In other words, CS is a decrease in systemic blood pressure with tissue hypoperfusion as a result of low cardiac output/index within the absence of hypovolemia. Hypoperfusion is evidenced by clinical signs resembling cool, clammy extremities, poor urine production, and mental confusion.

The purpose of the classification scheme is to help in clear communication between clinicians and researchers regarding the patient’s current clinical status, recognizing that CS encompasses a spectrum, including those at high risk for shock as a result of myocardial dysfunction in addition to those that develop hemodynamic collapse and cardiac arrest. The writing committee focused on the next guiding principles in developing the classification scheme:

• Easy and quick to make use of on the bedside for initial assessment and re-assessment
• It concerns research conducted up to now and the longer term
• Can be utilized in all clinical environments (i.e. emergency departments, intensive care units, catheterization labs)
• Actionable and resulting in behavioral change to enhance performance
• They have prognostic potential allowing for differentiation of mortality and morbidity depending on the precise form of shock.

The CS classification scheme includes five stages of shock, labeled A through E. The authors divided patients into three categories, including laboratory test results, physical examination results, and hemodynamics. In the case of cardiac arrest, the modifier (_AND) is added to the classification of stages (i.e. stage C)_AND). Here is a temporary description of every stage, including the domains of patient characteristics that might be expected at each stage.

Grade A or “at risk”:

• The patient has been identified as being in danger for developing CS but doesn’t yet have any signs or symptoms
• Diagnoses resembling non-ST-segment elevation myocardial infarction, ST-segment elevation myocardial infarction (especially within the case of anterior wall or large infarcts), and decompensated heart failure (each systolic and diastolic)
• Physical examination, laboratory tests and hemodynamics are inside normal limits.

Stage B or “Beginner CS”:

• Also called foreshock or compensated shock
• Patient with relative hypotension (SBP < 90 mm Hg or mean arterial pressure) [MAP] < 60 mm Hg or drop in MAP of > 30 mm Hg from baseline) or tachycardia (heart rate ≥ 100 beats per minute) without hypoperfusion
• Physical examination findings may include increased jugular venous distention (JVP), rales within the lung fields, warm skin with strong distal pulses, and normal brain function.
• Laboratory findings may include normal lactate levels, minimal renal impairment, and elevated brain natriuretic peptide (BNP)
• Hemodynamic findings include relative hypotension, tachycardia, normal cardiac index (≥ 2.2 l/min/m²) and pulmonary artery (PA) oxygen saturation ≥ 65%

Stage C or “Classic CS”:

• The patient with hypotension and signs of ischemia requiring interventions aside from volume resuscitation to revive perfusion (i.e. administration of inotropic drugs, pressor drugs, mechanical support, or extracorporeal membrane oxygenation) [ECMO])
• Physical examination findings may include a stressed/fearful appearance, gray/mottled/dark skin, widespread rales within the lung fields, cold/cold skin temperature, altered level of consciousness, decreased urine output (<30 mL/hr).
• Laboratory findings may include lactate ≥ 2 mmol/L, decreased renal function (doubling of creatinine or > 50% decrease in glomerular filtration rate (GFR), elevated liver function tests (LFTs), elevated BNP
• Hemodynamic findings may include SBP <90 mm Hg or MAP < 60 mm Hg or drop in MAP > 30 mm Hg from baseline and devices/medications used to take care of adequate systolic pressure, cardiac index < 2.2 l/min/m²Pulmonary capillary wedge pressure (PCWP) > 15 mm Hg, cardiac output ≤ 0.6 W/m²

Stage D or “Deteriorating or Fatal CS”:

• A patient whose condition can’t be stabilized after at the very least half-hour of initial treatment
• Therapeutic measures are intensified, including the administration of multiple pressor drugs; mechanical circulatory support might be initiated
• Physical examination, laboratory and hemodynamic results are just like those in stage C but worsen

Stage E or “Extremis”:

• Patient with circulatory collapse, possibly in cardiac arrest, with ongoing cardiopulmonary resuscitation (CPR) and/or ECMO
• The patient requires multiple interventions (mechanical ventilation, defibrillation) and the assistance of multiple doctors.
• Physical examination findings may include near pulselessness, severe hypotension, fatal cardiac abnormalities (pulseless electrical activity) [PEA]ventricular tachycardia, ventricular fibrillation)
• Laboratory test results may include lactate ≥ 5 mmol/l and pH ≤ 7.2
• Hemodynamic findings include absence of SBP without resuscitation, PEA or ventricular arrhythmias, hypotension despite maximal medical intervention

PA catheters play a very important role in enabling clinicians to acquire hemodynamic data to determine a diagnosis, monitor response to therapy, and help differentiate CS from other types of shock. While the classic “cold, wet” CS is related to low CI, high systemic vascular resistance (SVR), and PCWP, there are 4 distinct hemodynamic presentations of CS. PA catheters provide real-time hemodynamic measures which can be essential for the care of those critically sick patients. It can also be possible for a patient to present with or develop mixed shock as CS progresses. Fever and leukocytosis could also be present, representing systemic inflammation reasonably than complete infection. Vasodilation (low SVR) that happens with inflammation and/or infection may further compromise coronary and systemic perfusion. Some data suggest that the usage of PA catheters is related to lower mortality in patients with CS, however the widespread use of this invasive monitoring stays controversial.

The classification scheme is straightforward and highly adaptable within the clinical setting. It provides clinicians with a typical language when diagnosing and treating patients in danger for or who develop CS. As a patient’s clinical condition evolves, it could actually easily progress through the stages and permit for clear documentation of the patient’s condition, and may also aid in data collection in clinical trials. We hope that this latest and widely supported tool will improve outcomes, guide management, and guide future research.

Baran, D. A., Grines, C. L., Bailey, S., Burkhoff, D., Hall, S., Henry, T., Hollenberg, S., Kapur, N., O’Neill, W., Oranto, J., Stelling, K., Thiele, H., van Diepen, S., Naidu, Srihari. (2019). SCAI clinical expert statement on the classification of cardiogenic shock. 94(1), 29-37 https://doi.org/10.1002/ccd.28329

Naidu, S., Baran, D., Jentzer, J., Hollenberg, S., van Diepen, S., Basir, M., Grines, C., Diercks, D., Hall, S., Kapur, N. , Kent, W., Rao, S., Samsky, M., Thiel, H., Truesdell, A., Henry, T. (2022). Update of the expert consensus on the SCAI shock classification: review and incorporation of validation studies: This statement has been endorsed by the American College of Cardiology (ACC), the American College of Emergency Physicians (ACEP), the American Heart Association (AHA), the European Society of Cardiology ( (ESC) Association for Cardiovascular Care (ACVC), International Society for Heart and Lung Transplantation (ISHLT), Society of Critical Care Medicine (SCCM) and Society of Thoracic Surgeons (STS) in December 2021. 79 (9) 933–946. https://doi.org/10.1016/j.jacc.2022.01.018

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