When to consider Mechanical Circulatory Support (MCS) in patients with severe cardiogenic shock?

When to Consider Mechanical Circulatory Support in Severe Cardiogenic Shock

Mechanical circulatory support (MCS) should be considered in patients with severe or refractory cardiogenic shock who fail to stabilize with pharmacological therapy, particularly when there is evidence of ongoing end-organ hypoperfusion despite optimal medical management. 1

Definition and Initial Assessment

Cardiogenic shock is defined as:

• Persistent hypotension (SBP <90 mmHg) despite adequate filling status
• Signs of hypoperfusion
• Hemodynamic criteria: cardiac index <2.2 L/min/m² and pulmonary capillary wedge pressure >15 mmHg 1, 2

Decision Algorithm for MCS Implementation

Step 1: Identify Shock Severity

• Use the Society for Cardiovascular Angiography and Intervention (SCAI) classification system to categorize shock severity 2
• Perform immediate echocardiography to assess ventricular function, valvular disease, and mechanical complications 1

Step 2: Optimize Medical Therapy

• First-line vasopressor: Norepinephrine to maintain MAP ≥65-70 mmHg 2
• First-line inotrope: Dobutamine (2-20 μg/kg/min) to increase cardiac output 2
• Consider alternative inotropes (milrinone, levosimendan) in specific situations (e.g., patients on beta-blockers) 1, 2

Step 3: Consider MCS When:

1. Persistent hemodynamic instability despite optimal medical therapy 1
2. Evidence of end-organ hypoperfusion despite pharmacological support 1
3. Acute myocardial infarction with cardiogenic shock requiring revascularization 1
4. Mechanical complications of myocardial infarction requiring stabilization before surgery 1
5. Bridge to decision when recovery potential is uncertain 1

Device Selection Based on Clinical Scenario

Left Ventricular Failure

• Microaxial intravascular flow pump (Impella): Reasonable in selected patients with STEMI and severe/refractory cardiogenic shock (Class 2a, Level B-R) 1
• IABP: Not recommended for routine use due to lack of survival benefit (Class 3, Level B-R) 1

Right Ventricular Failure

• Impella RP or TandemHeart RVAD: Consider for isolated right ventricular failure 1, 2

Biventricular Failure

• VA-ECMO: Consider for biventricular failure, but not recommended for routine use due to lack of survival benefit (Class 3, Level B-R) 1

Timing of MCS Implementation

The timing of MCS implementation is critical:

• Early implementation (before profound end-organ dysfunction) may improve outcomes 1
• Delayed implementation (after prolonged shock and multi-organ failure) is associated with increased mortality 3

Special Considerations

Bridge to Recovery

• MCS may be used temporarily until cardiac recovery occurs 1
• Regular assessment of cardiac function is essential to determine potential for weaning 1

Bridge to Decision

• MCS can stabilize patients while determining candidacy for longer-term support or transplantation 1
• Allows time for neurological assessment after cardiac arrest 2

Bridge to Transplantation or Durable LVAD

• Short-term MCS may be used to stabilize patients awaiting heart transplantation or implantation of a durable LVAD 1

Limitations and Caveats

• Despite widespread use, there is limited high-quality evidence supporting routine use of specific MCS devices 4
• MCS devices carry significant risks including bleeding, thromboembolism, and vascular complications 4
• MCS implementation should be limited to centers with experience in advanced cardiac care 4
• The decision to implement MCS should involve a multidisciplinary shock team when possible 1

Conclusion

While MCS offers potential hemodynamic benefits in severe cardiogenic shock, device selection should be guided by the specific clinical scenario, shock phenotype, and institutional expertise. The 2025 ACC/AHA guidelines provide the most recent evidence-based recommendations, supporting the use of microaxial flow pumps in selected patients with severe or refractory cardiogenic shock, particularly in the setting of STEMI 1.