Surgical Critical Care: Mechanical Circulatory Support

Mechanical Circulatory Support (MCS)

Types of Temporary MCS

  • Intra-Aortic Balloon Pump (IABP)/Intra-Aortic Balloon Counterpulsation (Most Commonly Used)
  • Left Ventricular Assist Device (LVAD)
    • Impella Devices
    • TandemHeart
  • Extracorporeal Membrane Oxygenation (ECMO)

Comparison

  Max Flow Preload Afterload MAP
IABP 0.5 L/min Small Decrease Decrease Small Increase
Impella 5.0 L/min Decrease No Effect Increase
TandemHeart 5.0 L/min Decrease Increase Increase
VA ECMO 6.0 L/min Decrease Increase Increase
    • IABP:
      • Provide the Least Hemodynamic Support (0.5 L/min Compared to 5-6 L/min)
      • Easiest to Place with Small Access Catheter
    • TandemHeart:
      • Requires Technical Expertise to Place the Inflow Cannula
      • Bypasses Left Ventricle – Left Ventricle Thrombus is Not a Contraindication (As with Impella)
    • ECMO:
      • Only Type that Provides Oxygenation

General Indications for Temporary MCS

  • Cardiogenic Shock Due to:
    • Acute Myocardial Infarction Complicated by Cardiogenic Shock (AMICS)
    • Acute Decompensated Heart Failure
    • Post-Cardiotomy Shock
    • Acute Rejection After Cardiac Transplant
  • Refractory Angina/Myocardial Infarction Awaiting Revascularization
  • Adjunct During High-Risk Percutaneous Coronary Intervention (PCI)
  • Bridge to Permanent LAVD or Cardiac Transplant

Types of Long-Term MCS

  • Ventricular Assist Devices:
    • Heartmate 3
    • Heartmate II
    • HeartWare HVAD
  • Total Artificial Heart

Intra-Aortic Balloon Pump (IABP)

Mechanics

  • Balloon Catheter Inserted Through the Femoral Artery
  • Proximal Balloon Tip is Placed in the Aorta Just Distal to the Left Subclavian Artery
  • Function:
    • Inflates on T Wave (Diastole)
    • Deflates on P Wave (Systole)

Hemodynamic Effects

  • Diastolic Inflation: Increases Diastolic Blood Pressure
    • Improves Coronary Perfusion
      • Increased Blood Flow is Most Likely to Occur in Coronary Vessels Maximally Dilated by Ischemia
      • Flow Becomes Pressure-Dependent when Autoregulation is Exhausted (Maximally Dilated)
  • Systolic Deflation: Decreases Afterload
    • Decreases Myocardial Oxygen Demand
    • Increases Cardiac Output
    • Increases Ejection Fraction
    • Increases Cerebral & Peripheral Perfusion Pressure

Contraindications 

  • Moderate-Severe Aortic Regurgitation
  • Aortic Aneurysm or Dissection
  • Uncontrolled Bleeding
  • Severe Peripheral Artery Disease

Complications

  • Risk of Complication:
    • Any Complication: 7%
    • Major Complication: 2.6%
  • Malposition
  • Major Bleeding
  • Acute Limb Ischemia
  • Balloon Leak

IABP 1

Impella Devices

Mechanics

  • Continuous Axial Flow Pump
  • Inserted Through the Femoral Artery
    • Impella 5.0 Can Be Placed Through Axillary Artery
  • Pigtail Tip Placed into the Left Ventricle
  • Continuously Pumps Blood from Left Ventricle into the Proximal Aorta
    • Does Not Require Pressure or EKG Timing
    • Dependent on Left Ventricle Preload & Requires Adequate Right-Sided Function

Hemodynamic Effects

  • Increases Cardiac Output (CO)
    • Increases Mean Arterial Pressure (MAP)
    • Increases Systemic Perfusion
  • Reduces Left Ventricle End-Diastolic Pressure
    • Decreases Myocardial Oxygen Demand
  • Decreases Pulmonary Wedge Pressure
    • Decreases Right Ventricle Afterload

Device Comparison

  • Impella 2.5
    • Provides 2.5 L/min Increased Cardiac Support
    • 12-Fr Sheath Placed Percutaneously
  • Impella CP
    • Provides 3.0-4.0 L/min Increased Cardiac Support
    • 14-Fr Sheath Placed Percutaneously
  • Impella 5.0
    • Provides 5.0 L/min Increased Cardiac Support
    • 21-Fr Sheath Requires Surgical Cutdown for Placement

Contraindications

  • Left Ventricle Thrombus
  • Mechanical Aortic Valve
  • Ventricular Septal Defect
  • Severe Peripheral Artery Disease
  • Moderate-Severe Aortic Regurgitation

TandemHeart

Mechanics

  • Extracorporeal Centrifugal Pump
  • Inflow Cannula
    • Inserted Through the Femoral Vein
    • Punctures the Intraatrial Septum from Right Atrium into the Left Atrium
  • Outflow Cannula
    • Inserted into the Femoral Artery
  • Blood Pumped from the Left Atrium, Through the Centrifugal Pump & Back into the Femoral Artery

Hemodynamic Effects

  • Decreases Left Ventricle Preload (End-Diastolic Volume)
    • Decreases Myocardial Oxygen Demand
  • Increases Cardiac Output (CO)
  • Increased Afterload from Blood Being Pumped Back into the Arterial System

Contraindications

  • Ventricular Septal Defect
  • Severe Peripheral Artery Disease
  • Moderate-Severe Aortic Regurgitation
  • Aortic Dissection

Extracorporeal Membrane Oxygenation (ECMO)

Types of ECMO

  • Veno-Venous (VV) ECMO – Provides Only Oxygenation
    • Most Commonly Used
  • Veno-Atrial (VA) ECMO – Provides Complete Cardiopulmonary Support (Oxygenation & Hemodynamic Support)

Mechanics

  • Inflow Cannula Inserted Through the Femoral Vein or Internal Jugular Vein
  • Blood is Pumped Out via an Extracorporeal Centrifugal Pump Over a Membrane Oxygenator for Gas Exchange
  • Outflow Cannula:
    • VV ECMO – Oxygenated Blood Returned into the Internal Jugular Vein or Right Atrium
    • VA ECMO – Oxygenated Blood Returned into the Femoral Artery or Aorta

Pulmonary Effects

  • VV ECMO:
    • Lung Blood Flow is Maintained with Oxygen-Rich Blood
      • Risk for Reverse Gas Exchange in the Lung if FiO2 is Low
    • Ability to Create High Systemic Oxygen Tension is Limited
  • VA ECMO:
    • Lungs Receive Minimal Oxygen-Rich Blood
      • Can Exacerbate Lung Ischemia
    • Able to Create High Systemic Oxygen Tension

Hemodynamic Effects

  • VV ECMO:
    • Provides No Hemodynamic Support
    • Oxygenated Blood is Returned to the Aortic Root as Usual (Maintains Coronary/Cerebral Vessel Perfusion)
    • Maintains Pulsatile Blood Flow
  • VA ECMO:
    • Decreases Left Ventricle Preload
      • Decreases Myocardial Oxygen Demand
    • Increases Cardiac Output (CO)
    • Increased Afterload from Blood Being Pumped Back into the Arterial System
    • May Have Decreased Oxygenated Blood Delivery to the Aortic Root (Decreased Coronary/Cerebral Vessel Perfusion)
    • Blood Flow is Non-Pulsatile

Contraindications

  • Indication: Acute Severe Cardiac or Pulmonary Failure that is Potentially Reversible & Unresponsive or Conventional Measures
  • Only One Absolute Contraindication to ECMO: Condition Incompatible with Recovery (Severe TBI or End-Stage Malignancy)
  • Other Contraindications:
    • VV ECMO:
      • Cardiac Arrest
      • Heart Failure
      • Severe Pulmonary Hypertension
    • VA ECMO:
      • Moderate-Severe Aortic Regurgitation
      • Aortic Dissection

References

  1. Ginat D, Massey HT, Bhatt S, Dogra VS. Imaging of mechanical cardiac assist devices. J Clin Imaging Sci. 2011;1:21. (License: CC BY-NC-SA-3.0)