Hemodynamic Differentiation of Shock Types

Key Hemodynamic Parameters for Shock Classification

• The American College of Cardiology recommends using cardiac index, systemic vascular resistance, and pulmonary capillary wedge pressure to differentiate types of shock, with normal ranges and expected changes in each type of shock, such as a cardiac index of 2.2-4.0 L/min/m², which is reduced in cardiogenic and hypovolemic shock, and normal or elevated in distributive shock 1
• Systemic Vascular Resistance (SVR) is elevated in cardiogenic shock and decreased in distributive shock, according to the American College of Cardiology and supported by evidence from Anaesthesia and Critical Care Medicine 2, 3
• Pulmonary Capillary Wedge Pressure (PCWP) is elevated in cardiogenic shock and decreased in hypovolemic shock, as stated by the American College of Cardiology and Critical Care Medicine 1, 4
• Central Venous Pressure (CVP) is elevated in cardiogenic and obstructive shock, and decreased in hypovolemic shock, as reported by Critical Care Medicine 3, 4

Hemodynamic Patterns in Different Shock Types

Cardiogenic Shock

• Cardiac index is decreased, with a value less than 2.2 L/min/m², and systemic vascular resistance is increased as a compensatory mechanism, according to the American College of Cardiology 1, 2
• Pulmonary Capillary Wedge Pressure (PCWP) is elevated, greater than 15 mmHg, and clinical presentation includes hypotension, signs of hypoperfusion, and pulmonary congestion, as described by the American College of Cardiology and Circulation 1, 5
• Additional hemodynamic markers include a cardiac power output less than 0.6 W and a shock index greater than 1.0, as stated by the American College of Cardiology 1

Distributive Shock

• Cardiac index is normal or increased, and systemic vascular resistance is decreased, according to Critical Care Medicine 3
• Pulmonary Capillary Wedge Pressure (PCWP) is normal or decreased, and clinical presentation includes hypotension, warm extremities, and increased lactate, as reported by Critical Care Medicine 3, 4

SCAI Classification for Cardiogenic Shock

• The Society for Cardiovascular Angiography and Interventions (SCAI) classification provides a standardized staging system for cardiogenic shock, with stages ranging from A (at risk) to E (extremis), as described by the American College of Cardiology and Circulation 1, 5, 6
• Stage A is characterized by normal hemodynamics, normotension, clear lungs, and normal perfusion, while Stage E is characterized by cardiac arrest, refractory hypotension, and hypoperfusion, requiring CPR, as stated by the American College of Cardiology and Circulation 1, 6

Practical Application of Hemodynamic Monitoring

• Invasive monitoring using arterial lines and pulmonary artery catheters can provide valuable information on cardiac index, systemic vascular resistance, and filling pressures, especially in refractory shock, as reported by Critical Care Medicine 3

Clinical Pitfalls in Hemodynamic Assessment

• Dynamic changes in hemodynamic parameters can occur rapidly as shock progresses or responds to treatment, emphasizing the need for continuous monitoring, as stated by Critical Care Medicine 3

Cardiogenic Shock Diagnosis and Management

Clinical Diagnostic Criteria

• The European Society of Cardiology defines cardiogenic shock as a clinical state of hypoperfusion characterized by systolic blood pressure <90 mmHg and central filling pressure >20 mmHg, or a cardiac index <1.8 L/min/m², resulting from primary cardiac dysfunction 7, 8
• The American College of Cardiology recommends diagnosing cardiogenic shock based on both clinical and hemodynamic parameters, including systolic blood pressure <90 mmHg for at least 30 minutes or requiring inotropes/vasopressors to maintain systolic blood pressure >90 mmHg 8, 9
• Evidence of end-organ hypoperfusion, such as decreased urine output (<0.5 mL/kg/h) 10, altered mental status 8, 11, cool extremities due to peripheral vasoconstriction 10, elevated lactate levels (>2 mmol/L) 9, 11, and acute liver or kidney injury 11, 12, is also crucial for diagnosis 8, 11

Classification Systems

• The Society for Cardiovascular Angiography and Interventions (SCAI) classification provides a nuanced staging system, including Stage A: at risk for cardiogenic shock, Stage B: beginning shock, Stage C: classic shock, Stage D: deteriorating/doom shock, and Stage E: extremis with cardiac arrest requiring ongoing CPR and/or ECMO 8, 11, 13

Etiology and Pathophysiology

• The American Heart Association states that cardiogenic shock results from primary cardiac dysfunction leading to inadequate cardiac output and tissue hypoperfusion, with the most common cause being acute myocardial infarction (AMI), occurring in 7-10% of AMI cases 8, 11, 12

Prognostic Considerations

• The European Society of Cardiology reports that despite advances in treatment, cardiogenic shock remains associated with high mortality, including 30-day mortality rates of 40-45% in contemporary studies 11, 12
• Mortality increases stepwise with progression through SCAI shock stages A to E, and the presence of cardiac arrest significantly increases mortality at every stage of shock 11, 12

Cardiogenic Shock Hemodynamics

Definition and Diagnosis

• The American College of Cardiology describes cardiogenic shock as characterized by decreased cardiac output/cardiac index (<2.2 L/min/m²) due to primary myocardial dysfunction and impaired contractility 14, 15
• Increased CVP (>15 mmHg) results from elevated right-sided filling pressures and backward failure, according to the American College of Cardiology 14
• The European Society of Anaesthesiology notes that increased systemic vascular resistance (SVR) develops as a compensatory mechanism in cardiogenic shock, with the body attempting to maintain blood pressure despite falling cardiac output through systemic vasoconstriction 15, 16
• Elevated pulmonary capillary wedge pressure (PCWP >15 mmHg) reflects left ventricular failure and volume overload, as stated by the American College of Cardiology 14

Differentiation from Other Shock Types

• Distributive/Neurogenic shock is characterized by decreased SVR, which is the opposite of cardiogenic shock, with pathological vasodilation, according to the Society of Critical Care Medicine 17, 18
• The Society of Critical Care Medicine notes that distributive shock typically presents with normal or decreased CVP, and normal or increased cardiac output in early stages 17

Pathophysiology

• The damaged myocardium cannot generate adequate cardiac output, leading to increased vascular resistance, as described by the European Society of Anaesthesiology 15, 18
• Compensatory neurohormonal activation triggers systemic vasoconstriction to maintain perfusion pressure, increasing SVR, according to the European Society of Anaesthesiology 15, 16
• This increased afterload further impairs the already failing heart, creating a vicious cycle, as noted by the European Society of Anaesthesiology 16

Clinical Considerations

• The Society of Critical Care Medicine warns against confusing late-stage septic shock with cardiogenic shock, as septic shock can develop myocardial depression but the primary hemodynamic pattern remains distributive with decreased SVR 17, 18

Cardiac Index Guidelines

Definition and Normal Values

• The European Society of Cardiology defines normal cardiac function as maintaining a cardiac index in excess of 2.0 L/min/m² with a pulmonary capillary wedge pressure of less than 20 mmHg 19

Clinical Thresholds for Pathology

• The American College of Cardiology specifies that cardiac index <2.0 L/min/m² with hypotension constitutes hemodynamic criteria for shock diagnosis, and a cardiac index <2.2 L/min/m² combined with systolic blood pressure <90 mmHg and pulmonary capillary wedge pressure >15 mmHg defines cardiogenic shock 20
• In decompensated heart failure, cardiac index is usually <2.2 L/min/m², and patients with congestive heart failure and ejection fraction below 40% demonstrate mean cardiac index of 2.3 ± 0.6 L/min/m² 21

Management and Intervention

• The European Society of Cardiology recommends targeting a cardiac index >2.0 L/min/m² with filling pressure (pulmonary wedge) of at least 15 mmHg in patients with pump failure following myocardial infarction 19
• The American College of Cardiology recommends that when cardiac index falls below 2.2 L/min/m² with evidence of hypoperfusion, immediate intervention is required, and the threshold of 2.2 L/min/m² serves as a critical decision point for initiating inotropic support, mechanical circulatory support, or escalating hemodynamic monitoring 20

Cardiogenic Shock and Hepatic Dysfunction

Clinical Significance and Prognostic Value

• The American College of Cardiology recommends considering bilirubin levels as a prognostic indicator in cardiogenic shock, as elevated bilirubin levels are associated with worse outcomes, with a threshold of ≥1.3 mg/dL independently predicting 180-day cardiac mortality 22

Multiorgan Dysfunction Context

• The Society of Critical Care Medicine suggests that hepatic dysfunction in cardiogenic shock is part of a broader pattern of multiorgan system failure, which is associated with nearly 50% in-hospital mortality, and that the combination of elevated bilirubin with other markers of end-organ hypoperfusion confirms the diagnosis of cardiogenic shock 22

Determining Refractory Cardiogenic Shock

Hemodynamic Criteria for Refractory Shock

• The American College of Cardiology recommends that refractory cardiogenic shock is defined by persistent tissue hypoperfusion despite adequate doses of two vasoactive medications and treatment of the underlying etiology, with specific hemodynamic criteria including cardiac power output <0.6 W, cardiac index <2.2 L/min/m², and elevated lactate despite maximal medical therapy 23
• Cardiac Power Output (CPO) <0.6 W is the most critical threshold for identifying refractory shock 23
• Cardiac Index (CI) <2.2 L/min/m² despite vasopressor and inotropic support 23
• Systolic Blood Pressure <80 mmHg despite maximal treatment or requiring high-dose vasopressors to maintain SBP >90 mmHg 24
• Elevated filling pressures: Pulmonary Capillary Wedge Pressure (PCWP) >15 mmHg in LV-dominant shock 23
• Right Atrial (RA) pressure patterns help differentiate phenotypes: RA >15 mmHg suggests RV involvement, while RA <15 mmHg suggests LV-dominant shock 23

Phenotype-Specific Criteria

• LV-Dominant Refractory Shock is characterized by CPO <0.6 W with PCWP >15 mmHg and RA <15 mmHg 23
• RV-Dominant Refractory Shock is characterized by CPO <0.6 W with RA >15 mmHg and PCWP <15 mmHg 23
• Biventricular Refractory Shock is characterized by CPO <0.6 W with both RA >15 mmHg and PCWP >15 mmHg 23

Temporal Criteria

• The timing element is critical for defining refractory status, with progressive deterioration requiring increasing doses of intravenous inotropes and/or IABP to maintain hemodynamic targets, and failure to wean from inotropes 24
• Failure to wean from cardiopulmonary bypass is characterized by prolonged weaning time >1 hour with deteriorating hemodynamics or cardiac arrest 24
• Postcardiotomy setting is characterized by persistent shock despite maximal medical therapy including inotropes and IABP 24

Contraindications to Escalation

• Anoxic brain injury is a contraindication to mechanical circulatory support 23
• Irreversible end-organ failure is a contraindication to mechanical circulatory support 23
• Prohibitive vascular access is a contraindication to mechanical circulatory support 23
• Do Not Resuscitate (DNR) status is a contraindication to mechanical circulatory support 23

Practical Algorithm for Determination

• Obtain invasive hemodynamics via pulmonary artery catheter showing CPO <0.6 W and CI <2.2 L/min/m² 23
• Identify shock phenotype (LV, RV, or biventricular) using RA pressure, PCWP, and PAPi 23
• Assess for contraindications to mechanical circulatory support 23
• Escalate to MCS consideration if no contraindications exist 23
• Prolonged attempts at medical optimization should be avoided, with application of IABP within 30 minutes and MCS within 1 hour from first weaning attempts suggested to prevent complications 24

Cardiogenic or Hypovolemic Shock

Hemodynamic Pattern Analysis

• Tachycardia is the body's attempt to maintain cardiac output when stroke volume is reduced, according to the American Heart Association, as published in Circulation 25
• Decreased pulse pressure reflects the combination of reduced stroke volume and increased arterial stiffness from vasoconstriction, as noted by the European Society of Cardiology in the European Heart Journal 26
• Decreased SvO2 (<70%) indicates inadequate oxygen delivery to tissues with increased oxygen extraction, as reported by the Society of Critical Care Medicine in Critical Care Medicine 27, 28

Critical Distinguishing Feature: Ventricular Pressure

• The failing myocardium cannot generate adequate output despite elevated filling pressures, as described by the American Society of Anesthesiologists in Anaesthesia 29
• Clinical signs of cardiogenic shock include pulmonary edema, jugular venous distension, and signs of organ hypoperfusion, according to the American College of Cardiology in JACC: Heart Failure 30, 26

Clinical Approach to Differentiation

• Physical examination should include looking for jugular venous distension and peripheral perfusion, as recommended by the European Society of Cardiology in the European Heart Journal, and the American Heart Association in Circulation 26, 25
• Invasive hemodynamic monitoring with a pulmonary artery catheter provides definitive measurements of cardiac output, SVR, and filling pressures when diagnosis remains unclear, as noted by the Society of Critical Care Medicine in Critical Care Medicine 27, 28

Cardiac Index Measurement and Interpretation

Standard Reference Values

• The European Society of Cardiology defines severe cardiac dysfunction as cardiac index <1.8 L/min/m² with central filling pressure >20 mmHg 31

Critical Clinical Thresholds

• Cardiac power output <0.6 W represents the most critical threshold for identifying refractory cardiogenic shock, even more predictive than cardiac index alone, in patients with cardiac index <2.2 L/min/m² despite maximal doses of two vasoactive medications and treatment of the underlying cause 31

Measurement Considerations

• The thermodilution method via pulmonary artery catheter remains the gold standard for invasive cardiac index measurement, requiring measurements in triplicate for reliability, although severe tricuspid regurgitation causes underestimation, necessitating the Fick method instead, as noted by the European Heart Journal 31
• Noninvasive echocardiographic measurement using Doppler velocity-time integral provides reliable cardiac index assessment in most clinical scenarios, with normal limits by echocardiography (1.9-4.3 L/min/m²) aligning closely with invasive measurements, according to the European Heart Journal 31

Differentiating Cardiogenic, Hypovolemic, and Obstructive Shock

Hemodynamic Profiles and Diagnostic Approaches

• The European Journal of Heart Failure recommends that a clinical presentation of hypotension, pulmonary edema, jugular venous distension, cool extremities, altered mental status, oliguria, and elevated lactate is suggestive of cardiogenic shock 32
• The European Journal of Heart Failure and Intensive Care Medicine suggest that point-of-care ultrasound can provide rapid differentiation between cardiogenic, hypovolemic, and obstructive shock, with findings such as decreased left ventricular contractility, dilated ventricles, and B-lines indicating pulmonary edema in cardiogenic shock 32, 33
• Intensive Care Medicine recommends the use of norepinephrine as a first-line vasopressor in cardiogenic shock with persistent hypotension and tachycardia 33
• The European Journal of Heart Failure advises that pulmonary artery catheterization can provide definitive measurements in refractory or unclear cases, including cardiac index, SVR, PCWP, and CVP 32

Management Implications

• Intensive Care Medicine suggests that dobutamine can be used as a first-line inotrope to increase cardiac output in cardiogenic shock, although it is associated with arrhythmias and hypotension 33
• The European Journal of Heart Failure recommends that immediate fluid resuscitation with balanced crystalloids is the cornerstone of treatment for hypovolemic shock, with reassessment of volume status frequently 32
• Intensive Care Medicine advises that vasopressors should only be used transiently for life-threatening hypotension during active resuscitation in hypovolemic shock, not as primary therapy 33
• The European Journal of Heart Failure suggests that a fluid challenge may be beneficial in obstructive shock to optimize preload before definitive intervention 32

Cardiogenic Shock Management

Diagnosis and Initial Assessment

• The European Society of Cardiology defines cardiogenic shock as persistent hypotension with signs of end-organ hypoperfusion, carrying an in-hospital mortality rate of approximately 50% 34, 35
• The American College of Cardiology recommends immediate 12-lead ECG and transthoracic echocardiography to assess ventricular function and detect mechanical complications in patients with suspected cardiogenic shock 34, 35, 36
• Invasive arterial line monitoring is recommended for accurate blood pressure measurement in patients with cardiogenic shock 34, 35, 36

Treatment Algorithm

• The European Heart Journal recommends immediate coronary angiography within 2 hours of hospital admission with intent to perform revascularization in acute coronary syndrome-related cardiogenic shock 34, 35, 36
• Norepinephrine is the recommended first-line vasopressor when mean arterial pressure needs pharmacologic support in cardiogenic shock 37, 36
• Dobutamine is the first-line inotropic agent to increase cardiac output when signs of low cardiac output persist in cardiogenic shock 37, 36

Mechanical Circulatory Support

• The European Journal of Heart Failure recommends considering temporary mechanical circulatory support when end-organ function cannot be maintained by pharmacologic means or when there is inadequate response to inotropes in cardiogenic shock 37, 36
• Routine use of intra-aortic balloon pump (IABP) is not recommended in cardiogenic shock, except in cases of mechanical complications 36, 38

Monitoring and Treatment Response

• The Journal of the American College of Cardiology recommends monitoring lactate clearance as a marker of treatment response in cardiogenic shock 37, 36
• Target cardiac index >2.0 L/min/m² with PCWP <20 mmHg is recommended as a goal for treatment response in cardiogenic shock 36

Management of Cardiogenic Shock

Diagnosis and Assessment

• The American College of Cardiology recommends using clinical criteria, including systolic blood pressure <90 mmHg for 30 minutes or requiring vasopressors/inotropes to maintain systolic blood pressure >90 mmHg, plus evidence of end-organ hypoperfusion, to diagnose cardiogenic shock 39, 40
• Hemodynamic criteria, including cardiac index <1.8 L/min/m² without vasopressors/inotropes and cardiac power output <0.6 W, define cardiogenic shock 39

Initial Management Algorithm

• For acute myocardial infarction-related cardiogenic shock, the American Heart Association recommends immediate coronary angiography within 2 hours of hospital admission with intent to revascularize the culprit lesion, and considers staged revascularization rather than ad hoc multivessel PCI in patients with multivessel disease and severe shock 39
• For acute decompensated heart failure with cardiogenic shock, the Heart Failure Society of America notes that this phenotype follows an indolent course and more commonly requires biventricular support compared to acute myocardial infarction-related cardiogenic shock 40

Mechanical Circulatory Support

• The American College of Cardiology recommends considering mechanical circulatory support for refractory cardiogenic shock, defined by persistent tissue hypoperfusion despite adequate doses of two vasoactive medications and treatment of the underlying etiology, with specific hemodynamic thresholds, including cardiac power output <0.6 W 39
• For left ventricular-dominant refractory shock, the Society for Cardiovascular Angiography and Interventions recommends considering Impella or veno-arterial extracorporeal membrane oxygenation 39

Systems-Based Approach

• The American College of Cardiology recommends implementing standardized protocols with multidisciplinary shock teams, including cardiology, cardiac surgery, critical care, and nursing, to improve outcomes in cardiogenic shock 39, 40
• The American Heart Association recommends transferring patients to Level 1 cardiac intensive care units with 24/7 cardiac catheterization capability, full spectrum mechanical circulatory support availability, and longitudinal care pathways 39

Cardiogenic Shock with Acute Pulmonary Edema

Hemodynamic Profile

• The European Society of Cardiology confirms that cardiogenic shock is characterized by peripheral vasoconstriction manifesting as cold, clammy skin and peripheral cyanosis, with elevated systemic vascular resistance (SVR) as a compensatory mechanism to maintain blood pressure despite reduced cardiac output 41
• Cardiogenic shock is defined by cardiac index <2.2 L/min/m², with the failing myocardium unable to generate adequate output despite elevated filling pressures, resulting in hypotension and signs of hypoperfusion 41
• The condition is characterized by pulmonary capillary wedge pressure (PCWP) >15 mmHg, often >20 mmHg, indicating pulmonary edema from elevated left ventricular filling pressures 42, 41

Diagnostic Approach

• The Forrester classification specifically defines cardiogenic shock as having elevated PCWP (>18 mmHg) combined with depressed cardiac index, which can be confirmed by invasive monitoring via pulmonary artery catheter 41
• Point-of-care ultrasound and invasive monitoring can confirm the classic cardiogenic shock profile: cardiac index <2.2 L/min/m², PCWP >15 mmHg, elevated SVR, and elevated CVP 42, 41

Hemodynamic and Clinical Criteria for Cardiogenic Shock

Hemodynamic Thresholds

• Cardiac index < 2.2 L/min/m² (often < 1.8 L/min/m² in severe cases) defines cardiogenic shock and reflects inadequate myocardial output. 43
• Pulmonary capillary wedge pressure > 15 mmHg indicates left‑ventricular failure and pulmonary congestion in cardiogenic shock. 43

Metabolic Indicator of Tissue Hypoperfusion

• Serum lactate > 2 mmol/L signals anaerobic metabolism and is a marker of ongoing hypoperfusion in cardiogenic shock. 43

SCAI Staging System (Society for Cardiovascular Angiography and Interventions)

• Stage C (Classic Shock): Requires pharmacologic support for hypotension and shows clinical hypoperfusion (e.g., oliguria, altered mental status). 43
• Stage D (Deteriorating Shock): Worsening despite initial therapy, necessitating escalation to advanced mechanical circulatory support. 43

Phenotype‑Specific Hemodynamic Profiles

• Left‑ventricular‑dominant shock: Pulmonary capillary wedge pressure > 15 mmHg with right‑atrial pressure < 15 mmHg, producing prominent pulmonary congestion. 43
• Right‑ventricular‑dominant shock: Right‑atrial pressure > 15 mmHg with pulmonary capillary wedge pressure < 15 mmHg, leading to jugular venous distension but clear lung fields. 43
• Biventricular shock: Both right‑atrial pressure > 15 mmHg and pulmonary capillary wedge pressure > 15 mmHg, reflecting combined left‑ and right‑heart failure. 43

Cardiogenic Shock Classification and Hemodynamic Definitions

1. SCAI Staging Framework

The Society for Cardiovascular Angiography and Interventions (SCAI) classification provides a standardized, stepwise framework for categorizing cardiogenic shock severity, with mortality increasing progressively from Stage A (at‑risk) to Stage E (extremis). [44][45]

• Stage A (At‑Risk): Patients are normotensive with normal perfusion, clear lungs, and no hypoperfusion; cardiac index and blood pressure are normal. This stage commonly includes individuals with recent myocardial infarction, prior infarction, or acute‑on‑chronic heart‑failure symptoms. [Citation: 44, 45]

• Stage B (Beginning Shock): Characterized by relative hypotension or tachycardia without evidence of end‑organ hypoperfusion (normal lactate, adequate urine output, normal mentation). [Citation: 44, 45]

• Stage C (Classic Cardiogenic Shock): Hypoperfusion requiring pharmacologic (inotropes/pressors) or mechanical support (including ECMO) beyond volume resuscitation. Hemodynamic thresholds: systolic blood pressure < 90 mmHg, cardiac index < 2.2 L/min/m², lactate > 2 mmol/L, and cold extremities with oliguria. [Citation: 44, 45][46]47

• Stage D (Deteriorating/Doom): Similar clinical picture to Stage C but with worsening despite initial interventions, indicating failure to respond after ≥30 minutes of observation and treatment. [Citation: 44, 45]

• Stage E (Extremis): Represents cardiac arrest with ongoing CPR and/or ECMO support, accompanied by refractory hypotension and hypoperfusion. In‑hospital mortality approaches ≈ 50 %. [Citation: 44, 45][46]

2. Hemodynamic Criteria Defining Cardiogenic Shock

Diagnosis of cardiogenic shock requires the simultaneous presence of low systolic pressure, impaired organ perfusion, elevated lactate, and reduced cardiac output. [46][47]

• Systolic Blood Pressure: < 90 mmHg (sustained ≥30 min or requiring vasopressors/inotropes to maintain > 90 mmHg). [Citation: 46, 47]

• Cardiac Index: < 2.2 L/min/m² (severe dysfunction < 1.8 L/min/m²). [Citation: 46, 47]

• Lactate Level: > 2 mmol/L indicates anaerobic metabolism and end‑organ hypoperfusion. [Citation: 46, 47]

• Cardiac Power Output: < 0.6 W identifies refractory shock that warrants mechanical circulatory support. (Evidence noted in the source literature; no formal society guideline cited.)

• Systemic Vascular Resistance: Elevated as a compensatory vasoconstrictive response. [Citation: 46, 47]

• Filling Pressures: Pulmonary capillary wedge pressure > 15 mmHg (often > 20 mmHg in severe cases); central venous pressure > 15 mmHg when right‑ventricular or biventricular involvement is present. [Citation: 46, 47]

3. Hemodynamic Phenotypes and Mechanical Support Selection

Phenotyping based on left‑ and right‑ventricular filling pressures guides the choice of mechanical circulatory support.

• Left‑Ventricular Dominant Shock: Pulmonary capillary wedge pressure > 15 mmHg with central venous pressure < 15 mmHg, leading to prominent pulmonary congestion. Pathophysiology reflects left‑ventricular failure with backward pressure transmission into the pulmonary circulation. [Citation: 46, 47]

• Right‑Ventricular Dominant Shock: Central venous pressure > 15 mmHg with pulmonary capillary wedge pressure < 15 mmHg, producing systemic venous congestion (jugular distension, hepatomegaly) while lungs remain clear.

• Biventricular Shock: Both pulmonary capillary wedge pressure > 15 mmHg and central venous pressure > 15 mmHg, resulting in combined pulmonary and systemic congestion. This phenotype typically requires biventricular mechanical support and carries a poorer prognosis. [Citation: 46, 47]

4. Common Etiologies and Mechanistic Insights

Key mechanisms underlying cardiogenic shock are highlighted by recent anaesthetic literature.

• Acute Myocardial Infarction (AMI): Ischemic myocardial injury reduces contractility, lowering cardiac output and precipitating shock. [Citation: 46, 47]

• Acute Decompensated Heart Failure (ADHF): Acute exacerbation of chronic heart failure leads to progressive pump failure, often necessitating biventricular support rather than isolated left‑ventricular assistance. [Citation: 46, 47]

5. Pathophysiological Cascade

The Anaesthesia literature delineates a self‑reinforcing cycle driving cardiogenic shock.

• Reduced Cardiac Output: Primary myocardial dysfunction diminishes forward flow. [Citation: 46, 47]

• Compensatory Vasoconstriction: Systemic vasoconstriction attempts to preserve perfusion pressure but raises afterload, further impairing the failing heart. [Citation: 46, 47]

• Neuro‑hormonal Activation: Activation of the renin‑angiotensin‑aldosterone system and sympathetic nervous system perpetuates vasoconstriction and fluid retention. [Citation: 46, 47]

• Systemic Inflammation: Release of nitric oxide, interleukins, and tumor necrosis factor‑α contributes to pathological vasodilation and endothelial dysfunction (noted in a single source). [Citation: 46]

• Macro‑ and Micro‑hemodynamic Alterations: Combined effects culminate in multi‑organ dysfunction. [Citation: 46, 47]