Intra-aortic Balloon Pump

Assisted circulatory device consisting of an intra-aortic balloon which:

• ↑ CO by 0.5-1L/min
• Provides temporary myocardial support as bridge to recovery or definitive treatment
• Acts via counterpulsation to improve myocardial supply:demand
  Deflates pre-systole and inflates during diastole, causing:
  • Improved coronary perfusion
    Diastolic inflation ↑ DBP and improves coronary perfusion pressure and myocardial oxygen supply.
  • ↓ Afterload
    Pre-systolic deflation ↓ afterload and myocardial wall tension, ↓ myocardial oxygen demand and myocardial work.
• Improves forward flow rather than just inotropy
  Better in lesions where contractility may be adequate despite a low SV, e.g.
  • MR
  • VSD

Indications

• Reversible cardiogenic shock
  • Post-bypass
  • Post-MI
  • Severe IHD
    Bridge to stenting or CABG.
  • Severe acute MR
    Awaiting surgery.

Contraindications

• Cardiac
  • AR
  • Tachyarrhythmias
    Less effective in:
    • Tachycardia
      ↓ Viable inflation/deflation time.
    • Irregular rhythms
      Timing challenges.
• Anatomical
  • Aortic dissection
  • Severe peripheral vascular disease
  • Aortic aneurysm
  • Aortic grafts
• Other
  • Coagulopathy
  • Local infection
  • Sepsis
  • Lack of expertise

Anatomy

Equipment

• Catheter sheath
  Usually 7.5 Fr.
• Catheter balloon
  • 25-50mL
    Size should:
    • Cover from L SCA origin to coeliac artery
    • Fill 90-95% of the aorta
    • Augmentation optimised when balloon volume equals stroke volume
  • Helium-filled
    Low viscosity speeds inflation and smooths deflation.
• Console
  Contains pump, helium cylinder, and times inflation/deflation.

Technique

Patient selection:

• Cardiogenic shock
  • Of a form less responsive to inotropes
  • Without a stronger indication for VA ECMO or Impella
• Adequate vasculature
  • Accessible and un-tortuous femoral vessels
  • No acute aortic pathology

Some aortic stiffening is probably helpful though - an elastic and compliant aorta will distend during balloon inflation, impeding diastolic augmentation.

Use:

• Setting ratio
  Proportion of augmented to non-augmented beats.
  • 1:1
  • 1:2
  • 1:3
    Identical to no support.
  • 1:4
    Used prior to removal. ↑ risk of thrombus formation.
• Setting trigger
  May be:
  • ECG
    May target from R wave.
  • Pacemaker
    From pacing spikes.
  • Arterial
    From arterial upstroke.
  • Internal trigger
    In asystole.
• An optimised waveform
  • Measure at 1:2
  • Slope of augmented diastolic upstroke should be:
    • Straight
    • Parallel to augmented systolic upstroke
  • Augmented DBP should exceed unaugmented SBP
  • DBP at end of augmented stroke should be lower than unaugmented DBP by 15mmHg
• Anticoagulation
  • Practices vary
    • Heparinised saline through transducer
    • Low-dose systemic heparin
  • May not be required in first 24 hours

Optimisation:

• Optimising location
  • Balloon distal to L SCA, 2cm above left main bronchus
• Optimising timing
  • Should be performed in a 1:2 ratio

Weaning:

• Once inotropic requirements minimal
• Achieved gradually

Complications

• Vascular
  • Limb ischaemia
  • Vascular injury
    • Dissection
    • Pseudoaneurysm
    • Vessel injury/rupture
  • Embolism
    • Dislodged atheroma
• Device
  • Balloon rupture
    
    • Gas embolism
  • Stroke
    • Balloon thrombosis and embolism
    • Aortic atheroma dislodgement
  • Haemolysis
  • Infection
• Use
  • Incorrect positioning
    • Mesenteric ischaemia
    • Failure of augmentation

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References

1. Parissis H, Graham V, Lampridis S, Lau M, Hooks G, Mhandu PC. IABP: history-evolution-pathophysiology-indications: what we need to know. Journal of Cardiothoracic Surgery. 2016;11(1):122. doi:10.1186/s13019-016-0513-0