What is the role of mechanical circulatory assist devices, such as Intra-Aortic Balloon Pumps (IABP), Ventricular Assist Devices (VADs), and Extracorporeal Membrane Oxygenation (ECMO), in managing cardiogenic shock?

Role of Mechanical Circulatory Support Devices in Cardiogenic Shock

Key Recommendations

In patients with cardiogenic shock, microaxial intravascular flow pumps (Impella) are reasonable to reduce mortality in selected patients with STEMI and severe or refractory cardiogenic shock, while routine use of intra-aortic balloon pumps (IABP) or venoarterial extracorporeal membrane oxygenation (VA-ECMO) is not recommended due to lack of survival benefit. 1

Definition and Initial Assessment

Cardiogenic shock is characterized by:

• Hypotension (SBP <90 mmHg for ≥30 minutes)
• Evidence of end-organ hypoperfusion
• Elevated lactate levels (>2 mmol/L)
• Hemodynamic criteria: cardiac index <1.8 L/min/m² without vasopressors/inotropes 2

Types of Mechanical Circulatory Support Devices

1. Intra-Aortic Balloon Pump (IABP)

• Mechanism: Provides hemodynamic support through diastolic augmentation of aortic pressure and left ventricular afterload reduction 1
• Indications: No longer recommended for routine use in cardiogenic shock due to lack of survival benefit 1
• Current role: May be considered in patients with mechanical complications of acute coronary syndromes as a bridge to surgery 1

2. Percutaneous Ventricular Assist Devices

• Types: Impella devices, TandemHeart
• Evidence: Microaxial intravascular flow pumps (Impella) have shown mortality benefit in selected patients with STEMI and severe cardiogenic shock 1
• Advantages: Provide superior hemodynamic support compared to IABP 1
• Disadvantages: Higher risk of complications including bleeding and vascular complications 1

3. Extracorporeal Membrane Oxygenation (ECMO)

• Mechanism: Provides both circulatory and respiratory support
• Indications: Used for emergency biventricular support and when oxygenation is poor 1
• Evidence: Not recommended for routine use in AMI with cardiogenic shock due to lack of survival benefit 1
• Complications: Increases afterload, requires adequate right ventricular function, and has high complication rates 1

Clinical Decision Algorithm for MCS Selection

1. Assess shock severity and phenotype:

   • Evaluate hemodynamic parameters (cardiac index, pulmonary capillary wedge pressure)
   • Identify predominant failure pattern (left, right, or biventricular)

2. First-line therapy:

   • Initiate inotropic support with dobutamine (2-20 μg/kg/min) 2
   • Consider early revascularization for ischemic causes 1

3. Consider MCS when:

   • End-organ function cannot be maintained with pharmacologic therapy
   • Evidence of ongoing end-organ hypoperfusion despite optimal medical management 2

4. Device selection based on failure pattern:

   • Left ventricular failure: Impella devices (reasonable in selected patients) 1
   • Right ventricular failure: Impella RP or TandemHeart RVAD 2
   • Biventricular failure: VA-ECMO with LV venting or bilateral Impella pumps 2

5. Specific indications for MCS:

   • Bridge to decision/bridge to bridge (BTD/BTB): Short-term MCS until hemodynamics stabilize and additional options can be evaluated 1
   • Bridge to candidacy (BTC): Improve end-organ function to make patient eligible for transplant 1
   • Bridge to transplantation (BTT): Support until donor organ becomes available 1
   • Bridge to recovery (BTR): Support until native heart function recovers 1
   • Destination therapy (DT): Long-term support for patients ineligible for transplant 1

Special Considerations

Mechanical Complications of ACS

• Short-term MCS devices are reasonable for hemodynamic stabilization as a bridge to surgery 1
• Patients should be managed in facilities with cardiac surgical expertise 1

Multidisciplinary Approach

• MCS implementation decisions should involve a multidisciplinary shock team 2
• Consider transfer to specialized centers that can provide temporary MCS for patients not responding to initial measures 2

Pitfalls and Caveats

1. Device complications: All MCS devices carry risks of bleeding, thromboembolism, and vascular complications that must be weighed against potential benefits 1, 3

2. Patient selection: Not all patients benefit from MCS; careful selection is critical to improve outcomes 2

3. Timing: Delayed implementation of MCS may result in irreversible end-organ damage; consider early implementation before profound dysfunction develops 2

4. Center experience: MCS implementation should be limited to centers with experience in advanced cardiac care 2

5. Exit strategy: A difficult decision to withdraw MCS may be necessary when the patient has no potential for cardiac recovery and is not eligible for longer-term support or transplant 1

In conclusion, while mechanical circulatory support devices play an important role in managing cardiogenic shock, their use must be carefully considered based on patient-specific factors, the underlying cause of shock, and the availability of appropriate expertise. Current evidence supports the use of microaxial flow pumps in selected patients, while routine use of IABP or VA-ECMO is not recommended due to lack of demonstrated survival benefit.