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Cardiogenic Shock Definition
- Inadequate cardiac output + tissue hypoperfusion despite adequate volume status
- Classic findings:
- Systolic BP < 90 mmHg or vasopressor support
- Cardiac index < 1.8-2.2 L/min/m²
- Pulmonary capillary wedge pressure > 15-18 mmHg
- Evidence of end-organ hypoperfusion (oliguria, altered mental status, cold extremities, lactic acidosis)
Etiology
Most Common: Acute MI (75-80%)
- LV pump failure (largest contributor)
- Mechanical complications:
- Acute mitral regurgitation (papillary muscle rupture)
- Ventricular septal rupture (VSR)
- Free wall rupture (often fatal)
- Right ventricular infarction
Other
- Acute decompensated HF (ADHF) â chronic HF exacerbation
- Cardiomyopathy (DCM, HCM, takotsubo, peripartum)
- Myocarditis (viral, immune-mediated)
- Valvular disease (severe acute MR, AR, AS, MS)
- Arrhythmia-induced (sustained VT, AF with rapid response)
- Cardiac tamponade (technically obstructive but often categorized)
- Massive PE (technically obstructive)
- Post-cardiotomy shock
- Sepsis-induced cardiomyopathy
- Drug toxicity (β-blocker, CCB overdose)
SCAI Shock Classification (2019)
- Stage A (At Risk): no symptoms but increased risk (MI, decompensated HF in stable patient)
- Stage B (Beginning): clinical evidence of decompensation but no hypoperfusion
- Stage C (Classic): hypoperfusion + need for inotrope/vasopressor
- Stage D (Deteriorating): failure of medical therapy + escalation needed
- Stage E (Extremis): cardiac arrest with ongoing CPR or refractory shock
Clinical Manifestations
- Hypotension (SBP < 90 or need for vasopressor)
- Cold extremities + decreased peripheral pulses
- Oliguria (UOP < 30 mL/hr)
- Altered mental status
- Lactic acidosis
- Pulmonary edema (often)
- Elevated JVP
- Crackles (LV dysfunction with pulmonary edema)
- S3 gallop
Initial Management (Door-to-Support Time Critical)
- Recognition + assessment (SCAI staging)
- Volume + tissue perfusion assessment
- Echocardiogram (rapid bedside POCUS)
- Coronary angiography (if AMI etiology) â emergency PCI
- Hemodynamic monitoring (PA catheter if available)
- Inotrope (dobutamine first-line for low cardiac index)
- Vasopressor (norepinephrine for severe hypotension)
- Mechanical circulatory support if refractory
Inotropes
Dobutamine
- β1 + β2 agonist
- Increases contractility + decreases SVR
- 2.5-20 µg/kg/min IV
- Caveat: arrhythmia, tachycardia
- First-line inotrope in cardiogenic shock
Milrinone
- Phosphodiesterase III inhibitor
- Increases contractility + vasodilation (inotrope + vasodilator)
- 0.375-0.75 µg/kg/min IV
- Hypotension common
- Less arrhythmia than dobutamine
- Useful in patients on β-blocker
Dopamine
- Dose-dependent effects
- Higher arrhythmia rate (vs norepinephrine in SOAP II trial)
- Less commonly used now
Epinephrine
- Less used for chronic infusion (more for cardiac arrest)
- High arrhythmia rate
Vasopressors
Norepinephrine
- α1 + β1 agonist
- First-line vasopressor in cardiogenic shock + septic shock (SOAP II trial)
- 0.05-2 µg/kg/min IV
- Less arrhythmia than dopamine
- May worsen tissue perfusion if too high
Vasopressin
- Adjunct to norepinephrine
- Maintains MAP without excessive α-adrenergic effects
- 0.03-0.04 units/min
Phenylephrine
- α1 agonist only
- Limited role (no β effect)
- Reflex bradycardia possible
Mechanical Circulatory Support (MCS)
Intra-Aortic Balloon Pump (IABP)
- Inflates during diastole + deflates during systole
- Improves diastolic perfusion + decreases afterload
- Limited evidence of mortality benefit (IABP-SHOCK II trial)
- Bridge to revascularization or recovery
- Less utilization in modern era
Impella (Percutaneous LV Assist Device)
- Impella CP (most common): 4 L/min
- Impella 5.5 or 5.0: higher flow, axillary access
- Pulls blood from LV â aorta
- Better hemodynamic support than IABP
- Bridge to revascularization or decision
- DanGER-SHOCK trial 2024: positive findings
TandemHeart
- Trans-septal LV-to-aorta support
- Alternative to Impella
- Less commonly used
Combined ECMO + Impella (ECPELLA)
- For severe biventricular failure
- LV decompression + biventricular support
Other
- Centrifugal pumps
- BiPella (biventricular Impella)
Shock Teams (2024 Trend)
- Multidisciplinary team (cardiology, CT surgery, ICU, perfusion)
- Standardized protocols
- Earlier MCS escalation
- Improved outcomes (single-center observational + ongoing trials)
Special Situations
AMI with Cardiogenic Shock
- Emergent coronary angiography + PCI (door-to-balloon < 90 min ideally)
- Multi-vessel disease: culprit-only PCI initially (CULPRIT-SHOCK trial)
- Then staged PCI of non-culprit if needed
- Mechanical complications (papillary muscle rupture, VSR, free wall rupture) â emergent surgery
Mechanical Complications (Post-MI)
- Papillary muscle rupture (acute severe MR): emergent surgery
- VSR: emergent surgical repair
- Free wall rupture: catastrophic; surgical (rarely successful)
- MCS bridging to surgery
Right Ventricular MI
- Inferior MI + V4R elevation
- Sensitive to nitroglycerin/morphine (drops preload)
- Fluid resuscitation (paradoxical for hypotension)
- Avoid vasodilators
- Inotrope if RV failure
Tamponade
- Echocardiography essential
- Emergency pericardiocentesis
- Fluid resuscitation while preparing
Massive PE
- Thrombolysis (alteplase 50-100 mg IV)
- Catheter-directed thrombolysis
- Surgical embolectomy
- VA-ECMO
Heart Transplantation Considerations
- For chronic advanced HF (Ch 268)
- LVAD bridge to transplant
- Acute cardiogenic shock â temporary MCS â recovery vs LVAD/transplant decision
Sepsis-Induced Cardiomyopathy
- Reversible LV dysfunction in sepsis
- Treat sepsis + supportive (norepinephrine, inotrope if low CO)
- Echocardiogram for diagnosis
- Recovery with sepsis resolution
Outcomes
- Mortality 40-50% even with modern therapy
- Improving with:
- Early recognition + shock teams
- Early MCS
- Reperfusion in AMI
- Multidisciplinary approach
1ïžâ£ SCAI Shock Classification Detail
Stage A (At Risk)
- Patient at risk of cardiogenic shock
- No signs/symptoms of shock
- Examples: recent MI, decompensated HF in stable patient, hospitalized HFrEF
Stage B (Beginning Shock â Pre-Shock)
- Hypotension OR low-output state
- WITHOUT hypoperfusion (no end-organ dysfunction)
- Tachycardia, mild lactate elevation
- Examples: BP < 90, requiring fluids but not vasopressor
Stage C (Classic Cardiogenic Shock)
- Hypotension + hypoperfusion + need for inotrope/vasopressor
- Examples: norepinephrine + dobutamine; oliguria; altered mentation; lactate > 2
Stage D (Deteriorating)
- Failure of initial intervention
- Need for additional intervention
- Examples: increasing vasopressor, addition of MCS, escalating therapy
Stage E (Extremis)
- Refractory shock
- Cardiac arrest with ongoing CPR
- ECMO during CPR (ECPR)
- Highest mortality
2ïžâ£ AMI + Cardiogenic Shock (SHOCK Trial)
Background
- AMI = 75-80% of cardiogenic shock
- LV failure most common (vs mechanical complications)
- Pre-PCI era: 80%+ mortality
- Modern era: 40-50% mortality
Treatment Strategy
Pharmacologic
- Dobutamine first-line inotrope
- Norepinephrine for severe hypotension
- DAPT (aspirin + P2Y12)
- Anticoagulation peri-PCI
Mechanical Complications
- Papillary muscle rupture (acute severe MR): emergent mitral valve repair/replacement
- VSR: emergent surgical repair (or transcatheter VSR closure in select)
- Free wall rupture: surgical (high mortality)
- MCS bridging
Modern Outcomes
- 30-day mortality ~ 40-50%
- 1-year mortality ~ 50-60%
- Improving with early recognition + intervention + MCS
3ïžâ£ Mechanical Circulatory Support Detail
Intra-Aortic Balloon Pump (IABP)
Mechanism
- Helium-filled balloon in descending aorta
- Inflates during diastole â augments coronary perfusion
- Deflates during systole â decreases afterload
Hemodynamic Effects
- Modest decrease in afterload
- Modest increase in coronary perfusion
- Modest increase in cardiac output (10-15%)
Evidence
- IABP-SHOCK II trial (NEJM 2012): no mortality benefit in AMI + cardiogenic shock
- Less utilization in modern era
- Bridge to revascularization or recovery in select
Complications
- Limb ischemia
- Vascular access bleeding
- Hemolysis
- Migration
- Aortic dissection (rare)
Impella
Mechanism
- Catheter-based axial-flow pump
- Pulls blood from LV â aorta
- Direct LV unloading
Devices
- Impella 2.5 (2.5 L/min) â historic
- Impella CP (3.5-4 L/min) â most common
- Impella 5.0 or 5.5 (4.5-5.5 L/min) â surgical axillary access for higher support
- Impella RP â RV support (right ventricular)
Hemodynamic Effects
- Substantial LV decompression
- Improved coronary perfusion
- Better hemodynamic support than IABP
Evidence
- DanGER-SHOCK trial (2024): improved mortality in AMI + cardiogenic shock with Impella CP
- IMPRESS trial (2017): no significant difference vs IABP (but small)
- Increasing use in modern era + clinical practice
Complications
- Vascular access (femoral)
- Limb ischemia
- Hemolysis (cell-free hemoglobin)
- Aortic valve damage (rare)
- Stroke
TandemHeart
- LA-to-aorta circuit
- Trans-septal puncture for LA access
- Less commonly used than Impella now
Combined Therapies
ECPELLA (ECMO + Impella)
- VA-ECMO for biventricular support + Impella for LV decompression
- For severe biventricular failure
- Reduces complications of pure VA-ECMO (LV distension)
BiPella (Biventricular Impella)
- Impella CP + Impella RP for biventricular support
- Avoids ECMO complications
Decision Algorithm
IABP
- Less commonly used in modern era
- Some indication post-cardiotomy
- Bridge while preparing for higher support
Impella
- AMI + cardiogenic shock (DanGER-SHOCK)
- LV-dominant shock
- Bridge to recovery or LVAD/transplant
VA-ECMO
- Severe biventricular failure
- Refractory shock
- Cardiac arrest (ECPR)
- Add Impella for LV decompression if needed
Surgical LVAD / RVAD
- Long-term support
- Bridge to transplant or destination
4ïžâ£ Shock Team + Multidisciplinary Approach
Composition
- Cardiologist (advanced HF / interventional)
- Cardiothoracic surgeon
- Intensivist
- Perfusionist
- Pharmacist
- Nursing
Functions
- Rapid evaluation of patient
- Standardized algorithms
- Earlier MCS deployment
- Multi-disciplinary decisions
- Coordinate transfer to specialized centers
- Post-MCS care
Evidence
- Single-center observational studies show improved outcomes
- INOVA Health System shock team protocol
- Increasing adoption in tertiary centers
- 2024 ongoing trials
Transfer to High-Volume Centers
- Patients in cardiogenic shock benefit from transfer to high-volume cardiac centers
- Better outcomes with experienced shock teams + MCS programs
- Time-sensitive